Excavation work during the reconstruction of utility networks. Excerpts of pits, what a pit is, what the customer of a technical survey should know about pits. Measurements necessary when performing work in pits.

Parameters and methods of tunneling. Based on their depth, exploration pits are divided into shallow - up to 5 m, medium depth - from 5 to 10 m, deep - more than 10 m. In some cases, the depth of the pits reaches 40 m (cuts are usually made from deep pits). The depth of the pits is determined not only by geological conditions, but also by the stage of exploration - during prospecting work shallow pits are passed through; deep pits are most typical for detailed exploration.
More than half of the pits during exploration work are up to 10 m deep. As the depth of the traversed pits increases, the excavation process becomes more complicated, and the costs of money, time and energy for lifting, ventilation, drainage and even fastening increase. Due to the possible increase in the strength of rocks at great depths, the breaking operation is also complicated. Therefore, when drilling deep holes, special attention must be paid to improving technology and mechanization of work.
The holes have a rectangular or circular cross-section; the choice of the cross-sectional shape of the pit is made taking into account the physical and mechanical properties of the rocks, the method of excavation and the design of the support.
The most common are pits with a rectangular cross-section; Recommended typical sections of rectangular exploration pits are presented in Fig. 134. In pits with a cross-sectional area in the penetration of 2 m2 or more, two compartments are usually arranged - a lifting and a staircase. The cross-sectional area of the hole in the excavation is chosen mainly depending on the designed depth of the excavation; for pits of greater depth, a larger cross-sectional area in the penetration is taken. In general cases, the following relationship can be traced between these quantities (within the range of depth changes from 5 to 20 m):

where Sp is the cross-sectional area of the pit in the excavation, m2;
Hpr - design pit depth, m.
The cross-sectional areas of the pits from which the cuttings take place are taken to be somewhat large, ensuring sufficiently productive lifting.
The round shape of the cross-section of the pits is chosen in the following cases: when digging shallow pits without markings (sometimes called “pipes”) in fairly stable rocks; when driving holes in loose granular rocks using frame-lowering support; when excavating holes using the drilling method.

With a round shape, the cross-sectional area of the pit is used (due to the absence of corners) more fully, and the structure of the support, the main elements of which are made from materials stronger than wood (for example, metal), is compact. Therefore, with a round shape, the cross-sectional dimensions of the pit can be taken smaller than with a rectangular shape.
Holes of circular cross-section often have a diameter of 0.7-1.35 m, respectively, with which their cross-sectional area in the penetration ranges from 0.4 to 1.5 m2.
With a round cross-section, the pit can have not only a cylindrical, but also a “stepped” shape - the excavation is traversed by ledges of different diameters. The diameter of each subsequent ledge is less than the diameter of the previous (upper) one. The stepped shape of the pits is necessary for installing a special type of support - “frame-and-window”. The relationship between the cross-sectional area in the excavation of a cylindrical pit Sн and its depth Hpr can be expressed by the following formula:

When excavating step-shaped circular pits, the relationship between the average, maximum and minimum cross-sectional area of the excavation is expressed by the formula

The dependence of Scp on Hpr can be approximately expressed by the formula

Among the methods of digging exploration pits, it seems appropriate to highlight the following: with manual rock removal, with thawing and freezing of rocks, with the use of drilling and blasting operations and the drilling method. This division of methods for sinking pits makes it possible to characterize them not only in relation to the means of performing the main production operation (rock destruction), but also determines to a certain extent the meaning and technology of other main operations of the tunneling cycle. So, for example, the excavation of pits with manual breaking, carried out in loose or poorly cohesive rocks, requires special attention to the fastening operation, while ventilation of the workings to a certain extent loses its importance. Sinking is relatively often carried out with a low degree of mechanization.
A very specific method of sinking pits with thawing of frozen or freezing of thawed watered rocks, including operations to change the thermal regime of rocks in order to change their mining properties.
The method of drilling holes with drilling and blasting, used in rocks of various strengths, is characterized by a multi-operational mining cycle and usually a higher degree of mechanization. And finally, the drilling method, which is currently becoming widespread when drilling exploration pits in weak rocks, is characterized by the complex mechanization of tunneling work and the originality of the excavation support.
Drilling pits with manual rock removal. Manual breaking is typical for digging holes in soft and loose rocks; this operation is simple and usually not very labor intensive. Digging is carried out mainly with shovels and sometimes with picks; in some cases, the rock is first loosened with picks, crowbars or even jackhammers. The complexity and labor intensity of other operations in the tunneling cycle depend not only on the properties of the rocks, but to a large extent on the depth of the holes being driven.
Holes with manual breaking go to different depths, but the largest volume of tunneling work occurs in shallow holes.
When excavating pits up to 2.5 m deep, the operations of loading and lifting rock are excluded from the tunneling cycle - in this case, the rock is thrown out of the workings to the surface.
The fastening of small holes made in soft rocks is often not carried out; ventilation is carried out due to natural diffusion.
When driving pits to great depths, the mining cycle includes the operations of lifting rock and securing the excavation, and the latter has a particularly significant impact on the technology of excavation in loose (loose) rocks.
Drilling holes in soft rocks. Preparatory work includes clearing the working area of boulders and vegetation, the dimensions of which are determined taking into account the placement of stacks of rock produced from the excavation near the mouth of the pit and the convenience of performing work on the surface. Then the mouth of the pit is marked and the rock is removed along its contour to a depth of 0.5-1 m. A tunneling frame is installed above the mouth of the pit, the dimensions of which in the light are equal to the transverse dimensions of the pit. The ends of the frame elements must protrude beyond the mouth of the pit by at least 0.5 m. After installing the frame, the excavation of the pit begins, throwing rock onto the surface.
When driving a hole to a depth of 2 m, a manual crank is mounted on the tunneling frame. Lifting rock from a single-tub pit, a small-capacity tub (up to 0.04 m3); a ladder (usually a suspended one) is used to descend and ascend people. Mechanically driven lifting units are used in rare cases. When compiling geological documentation and testing carried out directly in the pit, the rock exposed to the surface is placed in a compact dump near the mouth of the pit.
In cases where samples are taken from rock produced from a pit, this rock must be poured into separate piles, sometimes called “penetrations”. The laying out of “penetrations” as the pit is deepened is carried out sequentially along the perimeter of the working site.
The pit is usually secured after excavation to a depth of 3-4 m. This part of the excavation is most often secured with a continuous crown support. The upper crowns of the support protrude 1 m above the mouth of the pit and are equipped with rows (Fig. 135).
At greater depths, with sufficient stability of the rocks in the pit, instead of a solid one, a crown support is installed on racks or, less often, suspended. A safety shelf is installed above the working face. When water enters the pit, it is usually removed in buckets.
Ventilation of pits, as noted above, is carried out mainly through diffusion. When the pits are deep enough, wind pressure is used for ventilation by installing inclined shields or sockets above the mouth of the pit.
The tunneling unit usually consists of three people - a tunneler and two turners. When the cross-sectional area of the pit is more than 2 m2, two miners can work simultaneously in the face. In the practice of geological exploration, the excavation of pits in soft rocks per shift ranges from 1 to 2 m; The average monthly penetration ranges from 20-40 m.
During liquidation, the pits are filled up, the support in some cases is completely or partially removed, but more often it is left in the excavation.

Drilling holes in loose granular rocks. A significant difference in the technology of tunneling in loose granular rocks that do not allow more or less significant vertical exposures lies in the peculiarities of the operation of securing the excavation and support structures.
A characteristic feature of tunneling work is the use of frame-and-lower support. The method of sinking pits with frame-lowering support (Fig. 136) has become most widespread in the exploration of gravel and boulder-pebble deposits.
The design of the support allows the passage of circular pits with ledges 2-4 m high; Each ledge is secured during its excavation. Before the start of excavation of the pit, its depth Hpr is set, based on which, taking into account the selected parameters of the benches, the diameter of the upper bench (mouth of the pit) is determined by the formula

where dу is the diameter of the lower ledge, usually taken equal to 0.8-1.1 m;
a" - the difference in the diameters of adjacent ledges, determined depending on the design features of the support (0.2-0.3 m);
ny = Hpr/hu - the number of ledges in the designed pit (hy - the height of the ledge, taken equal to 2-4 m).
Giving the pit a stepped shape leads to a fairly significant increase in its volume compared to a cylindrical pit.
In table 42 shows a comparison of the volumes of cylindrical and stepped pits; calculations were performed at dy=1 m (the diameter of the cylindrical pit was assumed to be equal to dy); hu = 3 m and a" = 0.2 m.
After marking the contour of the pit mouth on the working site, a tunneling frame is installed and a wooden or metal pile driver is mounted, equipped with a crank and a winch for lowering and lifting the frames (Fig. 137).

The diameter of the pit mouth should exceed the outer diameter of the first support frame by 10-20 cm. The rock separated from the bottom with shovels is thrown to the surface; excavation continues to the maximum depth ensuring the stability of the pit walls. Then a frame is lowered into the pit using a winch, and boards (formwork) are installed along the outer perimeter of it. Drilling the pit to the depth of the first ledge is carried out with simultaneous settling of the frame and formwork. After excavating the first ledge, the space between the walls of the pit and the formwork is backfilled; The frame is secured to the tunneling frame using ties.
The operations of excavating the second and subsequent pit ledges are carried out in the same sequence: the outline of the ledge is outlined, partial excavation of the rock is carried out along the height of the ledge, a frame is installed in the recess and formwork is laid around it, the ledge is deepened, upsetting the frame with a sledgehammer.
The use of frame-lowering support reduces the labor intensity of fastening and the cost of excavation, and also ensures higher safety of work.

When drilling pits with frame-and-drop support in the North-Western Geological Department, significant savings in material consumption and an increase in the rate of excavation of pits were achieved in comparison with the excavation of CO pits under the same conditions with continuous roof support. The average monthly speed of penetration of pits with frame-dropping strength is 25-35 m.
Drilling pits with thawing or freezing of rocks. When digging holes in frozen sedimentary rocks, the breaking operation becomes labor-intensive due to the significant strength of the rocks in the frozen state. Natural or artificial thawing of frozen rocks makes it possible to reduce the labor intensity of excavation, reducing this operation to manual loading of soft rocks into a bucket. Natural thawing of rock, carried out under the influence of solar radiation, is a long process and can be of practical importance only when a significant number of small pits are drilled in the summer, located in a dense grid. Artificial thawing is carried out by “burning”, rubble and steam.
Thawing by burning is used when digging prospecting or exploration pits in forested areas. The pits, as a rule, are carried out in winter, since in the warm season the workings are flooded with groundwater. Thawing of the rock is achieved by lighting a fire (burning) directly at the face of the pit. One fire consumes from 0.2 to 0.35 m3 of firewood. The thawing depth, depending on the quality of the fuel and the properties of the rocks, ranges from 0.2 to 0.4 m. The average consumption of firewood is 0.4-0.5 m3 per 1 m3 of rocks. When fuel is burned, the walls of the pit also thaw, losing their stability. As a result, an increase in the cross-section of the excavation is inevitable, as well as additional work to remove the rock that has fallen out of the walls and fasten the pit. When the rocks are significantly icy, water accumulates in the face, as a result of which some of the fuel does not burn. As the pit deepens, insufficiently efficient air circulation reduces the intensity of fuel combustion. The rock can be removed after thoroughly ventilating the pit, scraping off the thawed walls and securing the excavations.
Rubble thawing consists of the following: round-shaped stones (rubble, cross-sectional size 8-10 cm) are heated on the surface in fires laid out near the mouth of the pit to a temperature of 200-300 °C. The total volume of rubble, depending on the cross-section of the pit, ranges from 0.5 to 1 m3. In the center of the face of the pit, a depression is made, heated stones are thrown or stacked into it and covered with a layer of moss to reduce heat losses. After thawing, which lasts several hours, the moss and rubble are removed from the excavation and the thawed layer of rock 0.15-0.3 m thick is loaded into a bucket. The consumption of firewood used to heat the rubble is from 0.2 m3 or more per 1 m3 of rock. During rubble thawing, there is no need for artificial ventilation of the pit; the walls of the excavation remain stable and do not need to be fixed.
Steam thawing is characterized by higher efficiency and can be recommended for a large volume of tunneling work, but it is rarely used in field exploration practice. To organize steam thawing, the following equipment is required: a steam boiler, a steam pipeline with a distribution device, rubber hoses and hollow drills (Fig. 138). The steam thawing operation involves driving hollow drills into the bottom of a pit to a depth of 0.15-0.2 m and supplying steam. As the rock thaws, the drills are driven with a hammer into the face to a depth of 0.6 to 1.2 m and, when steam is supplied, the rock is thawed for 2-4 hours.

Thawing of frozen rocks with steam proceeds very intensively, but the contours of the pit are unclear. It is advisable to excavate the rock 2-3 hours after the steam is turned off, since at this time thawing continues due to the heat of the rock heated near the drills. With this method of excavation, the pit need not be secured.
In sediments with high filtration capacity, the water influx significantly complicates and sometimes makes the excavation of pits completely impossible. One of the ways to simplify mining operations in these conditions is freezing of rocks (mining pits is carried out in winter at subzero temperatures). When the face of the pit approaches aquiferous rocks and, in particular, quicksand, excavation is stopped for some time necessary for the rock layer to freeze, followed by penetration to a depth less than the thickness of the frozen layer, etc.
When digging pits in frozen rocks, interspersed with layers of thawed water-bearing rocks, combined excavation is used: the pits are driven through frozen rocks with thawing, and through thawed rocks - with freezing (Fig. 139), and the excavation of frozen aquifers is also carried out with thawing (rubble). The use in this case of explosive breaking, which is relatively often used in frozen rocks, is associated with the risk of flooding of the excavation after the explosion and is not recommended.

Freezing and thawing of rocks in the face is carried out to a relatively small depth of the layer removed during the cycle. The duration of these operations depends on climatic conditions and the defrosting method used. Productive work is achieved using the multi-hole method when a tunneling crew simultaneously passes several holes located at a short distance from one another. An approximate work organization schedule is shown in Fig. 140.
Drilling holes with drilling and blasting operations. Characteristics of tunneling works. Drilling and blasting is used when making pits in rocky and frozen rocks. This method of breaking rocks is used when drilling relatively shallow pits at all stages of deposit exploration, when drilling pits in soft and loose rocks intersect individual layers of rocks of IV and higher strength categories, when deepening pits into bedrock (“refilling” pits). However, this method is most typical for driving holes to great depths in fairly strong rocks.

Shallow holes with drilling and blasting operations are still often carried out without mechanization - manual drilling of holes, the use of wind power or hand fans for ventilation, lifting rock with hand cranks. This is largely explained by the small volumes and scattered nature of the excavation work, the lack of effective transport links or, in a particular case, electricity.
Drilling deep holes is generally a mechanized production process; The degree of mechanization predetermines the completion time, material and labor costs of tunneling work.
Means of mechanization of tunneling operations. Holes are drilled with light hand-held pneumatic hammer drills (supplied with compressed air from mobile compressors installed at the mouth of the holes) or hand-held electric drills. In some cases, motorized hammer drills can be used (provided the exhaust pipe is connected to the suction fan pipeline and the pit is intensively ventilated). The mechanization of loading rock broken from the face remains practically unresolved to this day. The use of grab loaders of the type used in the excavation of mine shafts is difficult due to the small cross-sections of the pits. Created by the Special Design Bureau of the Ministry of Geology of Russia, the small-sized grab loader GShK-1 with a grab capacity of 0.01 m3 and intended for pits with a cross-sectional area of more than 2 m3 has not found application due to low productivity. It seems advisable to recommend the use of rope grabs of slightly larger capacity not for loading rock into a bucket, but for removing it from the face and lifting it to the surface. The AG-1 hole-boring unit with a hydraulic grab-lift is being tested in geological exploration parties.
Bucket lifting of rock is carried out using small cranes, some of whose designs have been described previously. After blasting, the workings are ventilated with small centrifugal fans, and drainage is carried out with electric pumps and motor pumps.
In geological exploration parties carrying out significant volumes of tunneling work, complex units are used, along with the use of individual machines and mechanisms.
The ShPA-2 unit consists of a diesel engine, a compressor, a driven lifting and manual auxiliary winch, a fan and an electric generator. The equipment set includes a power saw and electrical equipment: frequency converter, control panel, alarm system, starting devices, lighting. All equipment is placed on a car trailer.
Similar tunneling units are manufactured at the West Kazakhstan Complex Expedition (the unit consists of a Pioneer crane, an electric generator, a compressor, a fan, a remote control and an alarm). The Yakut Geological Department, based on a skidder, has created a self-propelled boring machine equipped with a lifting and turning mechanism with a pneumatic grab and a compressor. The KMSH-VITR set of boring machines consists of an electric portable station with a gasoline engine, a KSh-100 boring crane, a pump, a centrifugal fan and a hand-held electric drill. The complex is convenient for transportation in off-road conditions; it can be easily disassembled into individual units weighing less than 80 kg.
Technology and organization of tunneling. The cycle of tunneling operations begins with drilling holes. When excavating shallow holes with a small cross-sectional area, the holes are drilled (and gouged out in frozen rocks) manually. Their depth is usually small (0.2-0.4 m when gouging holes with crowbars and less than 1 m when drilling with chisel drills).
The small depth of the holes, their increased diameter during chiselling (up to 10-12 cm) and the small cross-sectional area of the excavation (up to 1.25 m2) allow us to limit ourselves to hole sets of 2-5 holes (Fig. 141).
In large cross-section holes, when perforating or electric rotary drilling of holes, their depth reaches 1.2-1.4 m, and the location and quantity are taken in accordance with the selected type of cut and the area of the face.

In holes with a cross-sectional area of less than 2 m2, one person drills the hole; with a larger area, two drillers can work simultaneously. A blaster or a miner who has the right to conduct blasting operations charges and explodes the holes. Blasting holes is electric and is carried out from the earth's surface using a blasting machine. If there is a significant number of holes, the charging and blasting operation takes approximately 30 minutes (charging one hole takes 2-3 minutes).
When working in two or three shifts, it is advisable to ventilate the pit during the break between shifts; during single-shift operation, gaseous explosion products are usually removed from the workings due to diffusion or wind pressure during non-working hours of the day.
Before removing the rock, the face is brought into a safe condition after ventilation - the support damaged during the explosion is inspected and repaired; strip loose walls of the pit; pump out, if necessary, the water accumulated during ventilation.
The rock is loaded manually or by mechanical loaders. If the cross-sectional area of the pit is sufficient for lifting rock, it is advisable to use two buckets - while loading a bucket uncoupled from the lifting rope, another bucket, previously filled with rock, is lifted to the surface, unloaded and lowered into the pit. Rock removal takes up most of the mining cycle time.
In hard rocks, usually characterized by increased stability, the pit is fastened with a significant lag from the bottom, and the fastening process is often not included in the cycle of tunneling operations.
The installation of support and reinforcement of the pit is usually carried out in shifts specially allocated for this purpose, after completing several tunneling cycles.
An approximate work organization schedule is shown in Fig. 142.
The average monthly penetration of pits reaches 30-40 m.

The tunneling unit usually consists of three to four people: one or two work in the workings, two work on the surface. Sometimes a tunneling crew works using the multi-hole method to simultaneously excavate several holes. This ensures better organization of work and reduces downtime associated with blasting and ventilation.
General information about the explosive method of tunneling. Drilling holes in relatively easily deformable rocks, which boils down to the formation of a mine opening due to irreversible deformation of rocks (clays, loams, sandy loams, loess) during the explosion of a charge, is called explosive excavation. In wet clays, this excavation method is especially effective.
The drilling technology is very unique and boils down to the following: a well is drilled to the design depth of the hole; the well is filled with alluvial BB; detonators, electric detonators and a detonating cord can be used as initiators. After blasting, the resulting excavation must be thoroughly ventilated. In many cases, there is no need to fasten the pit, since the rocks, being deformed as a result of the explosion, are compacted and become quite stable.
In pits formed by explosive methods, with a relatively regular round cross-sectional shape, the diameter of the excavation along its height does not remain constant; the formation of an ejection funnel in the upper part of the pit is also characteristic. There is an almost direct relationship between the volume of the charge (Azar) and the volume of the cavity (Avyr) formed in the rock after the explosion. The value of the proportionality coefficient k depends on the properties of rocks and explosives.
In the practice of digging holes in clay, loam and loess when using ammonites, the coefficient k is taken in the range from 150 to 300. For the convenience of calculations, moving from volumes to diameters of workings and charges and taking the value of k in the recommended values, we will have

The data obtained by calculation are approximate; they should be clarified during experimental explosions. The explosive method is characterized by insignificant costs of time and material resources, high labor productivity, it is applicable in cases where pits are used as transport workings, and geological information is obtained by making cuts from these pits.
An interesting technology is for drilling holes in clays and weathered clayey tuffs, adopted by the Pervomaiskaya and Merkushevskaya hydraulic fracturing units of the Primorsky Geological Department. Pits up to 15 m deep with a cross-sectional area of 1-1.25 m2 are made using drilling and blasting operations, a feature of which is the use of boiler charges. A central hole is drilled in the face, it is shot through, and a charge weighing 3-5 kg is placed in the resulting chamber. When a boiler charge explodes, the rock is partially pressed into the walls of the excavation and partially (at a small depth of the pit) is thrown out to the surface. Only 25 to 50% of the blasted rock must be removed from the pit.
Drilling pits. Characteristics and conditions for the use of hole excavation by drilling. Over the past decade, the drilling method of excavating pits has begun to be introduced into the practice of mining exploration.
The drilling method of digging holes is characterized by a number of significant advantages that distinguish it from other methods. Drilling pits provides a significant improvement in working conditions and work safety, achievement of the highest technical and economic indicators, elimination of heavy work and comprehensive mechanization of the construction of exploration workings.
Improving working conditions and work safety is a consequence of the fact that during the process of drilling a pit, the worker is not in the working face, but on the surface; the operation of fastening the pit is less labor-intensive and is carried out faster; There are proposals for mechanizing the collection of bulk samples from the bottom of the pit, in which the need for a person to stay in the workings disappears altogether.
High technical and economic indicators of drilling holes include a sharp increase in the speed of penetration, a reduction in labor and material costs.
Let us illustrate this with practical data from one of the expeditions of the Russian Ministry of Geology, which introduced the drilling of small pits on a large scale (Table 43).

Currently, only with the drilling method can we talk about truly comprehensive mechanization of hole excavation. The operations of breaking rock in the face, removing it from the workings and placing it on the surface in dumps are mechanized; the problem of mechanizing the construction of support in a pit that has the correct cylindrical shape is not insoluble (there is already a design design for a portable support layer mounted on a drill string); in addition, in some cases the pit may not be fastened. The scope of application of the drilling method is still limited to weak rocks (I-IV drillability categories).
The institutes TsNIGRI and MGRI (Moscow Geological Prospecting Institute) have developed and tested designs of drilling rigs for drilling exploration pits in medium-hard rocks.
The transportable drilling rigs used ensure drilling of holes up to 30 m deep and more.
The drilling method is especially effective for significant volumes and concentrations of tunneling work.
Equipment used. Holes are drilled mainly in a rotary manner using installations mounted on the base of a car, tractor or trailer. Some of these installations are suitable only for drilling pits, others are universal; they can be used to drill pits and shallow exploration wells. The drilling tools used are mainly augers and, less frequently, cylindrical bucket drills of various designs. Hole drills are designed to destroy the rock face and periodically lift the destroyed rock to the earth's surface. The rock is destroyed by the cutting edges of the auger flanges or the bottom of a cylindrical drill; the destroyed rock is accumulated on the auger flanges or in a cylindrical body and, together with the drill, rises from the excavation.

Installations for drilling small holes are usually vehicles with simple attachments mounted on them (Fig. 143).
Medium-depth or deep holes are drilled with installations mounted on vehicle chassis (Fig. 144), on trailers with independent drives, or on trailers in combination with truck cranes. The drilling rig UBSR-25 is mounted on the basis of a skidder. The characteristics of drilling rigs used for drilling pits are given in Table. 44.

Technology of sinking and fastening pits. After clearing and leveling the horizontal area on the surface and bringing the drilling rig into working condition, they begin to drill holes. The production process of sinking a hole consists of lowering the drill to the face, drilling (usually to a depth of 200-400 mm), lifting the drill filled with rock, and unloading it on the surface. The duration of tripping operations increases sharply with increasing hole depth when it is necessary to build up and dismantle the string of drill rods during each trip. In some installations, this drawback is eliminated due to the design of a bucket drill sliding along the drill rods, raised and lowered on cables without disassembling and extending the rod string.
Currently, sliding auger drills and combined hole drills designed by MGRI have been developed and are being tested, making it possible to increase the working depth by two to three times, as well as to carry out tripping operations without disassembling the drill string.
Bucket hole drills are unloaded either manually or with the help of rotating blades that form the body of the drill and are rotated during unloading by a special hydraulic drive (bucket drill installation LBU-50). Auger drills are usually unloaded when they rotate at an increased speed (unloading due to the developing centrifugal force). When unloading the hole, the mouth of the hole is blocked with lyads.

The fastening of holes drilled is simplified due to the relatively regular cylindrical shape of the workings, while favorable conditions are created for the use of pre-made, sometimes called “inventory”, reusable support. Wood is losing its importance as the main fastening material and is being replaced by metal or plastics.
It is possible to use round frame-lowering support, however, a significant difference in the diameter of the pit steps requires the use of a set of hole drills of different diameters. When replacing wooden puffs with fiberglass plates, the difference in the diameters of the steps of the hole is reduced and it is possible to use one hole drill equipped with an expander.
The use of spacer split rings made of angle or channel steel with wooden or fiberglass ties can provide fastening of a cylindrical pit.
Using the UBSR-25 installation, pits are drilled with metal casing pipes that serve as reliable support.
In the practice of drilling pits in the Ural complex expedition, the workings are secured with metal rings consisting of two half-cylinders bolted together.
Good results were obtained during production tests of ring support made of polyethylene and vinyl plastic rings with longitudinal cuts, reinforced at the ends with angle steel. The assembly of the rings into a column and its installation in the excavation was carried out after the completion of drilling of the hole using a drill string equipped with a support frame at the end. The support made of fiberglass cylinders with a cut along the generatrix has significant elasticity and... therefore, it can be considered “universal” - allowing the use of standard rings for pits of various diameters (from 600 to 1150 mm). The rings fit into each other to a depth of 150 mm; The rigidity of the support is ensured by special locks.
When eliminating a pit, the considered designs ensure the extraction of support for reuse.

The condition in which the foundation of the building is located cannot be determined by a simple inspection, since its main part is hidden under the thickness of the earth. In the case when there is a need to examine the foundation, check its integrity, and draw conclusions about its further operation, you need to go deeper to a certain depth. It is important to do this correctly so as not to damage the structure. Specialists from our company GeoGIS LLC can expertly dig a foundation pit in Moscow and the region. Our employees have sufficient experience, knowledge, necessary permits and licenses to perform such work.

What is a foundation pit?

Having contacted our specialists to order an inspection of the load-bearing foundation of the house, the owner will be faced with the term “pit”, without which it is impossible to carry out a quality inspection of the foundation. The question is often asked - what is a foundation pit? In fact, this is an ordinary excavation, a vertical pit, exposing the surface of the structure, hidden under a layer of soil. It allows our specialists to objectively assess the condition of the foundation, the extent of its damage, and evaluate the possibility of restoration and repair.

IMPORTANT! The pitting must be carried out without deteriorating the strength characteristics of the structure, therefore, specialists with skills in such work should be involved in the construction of the pit.

Often, in the course of our work, non-standard situations arise. Our specialists, having the necessary experience, find, if necessary, a rational solution to the following issues:

how to make a horizontal hole under the slab;
where to place the excavation in order to carry out the survey as completely as possible at minimal cost;
ensuring safe work in pits on difficult soils and objects.

The dimensions of the open pit allow our employees to easily take samples and visually inspect the surface of the foundation.

Why are pits being drilled in Moscow?

ATTENTION! Our specialists, according to the technical specifications: dig a pit, conduct a visual inspection of the foundation, examine it for the presence of waterproofing and the integrity of the structure.

For final conclusions, we use data from laboratory studies of samples taken from the pit:

soil;
the material from which the foundation is made (concrete, stone);
in difficult cases - reinforcing material.

For what purpose is the underground part of structures being studied and the foundation pit being developed in Moscow and the region? In densely populated cities, with a large number of historical buildings, there is often a need to:

reconstruct an old building for future use;
in the re-equipment of an industrial enterprise (installation of new equipment, structures);
carry out restoration and research work on architectural, cultural and ancient buildings;
build additional floors, strengthen structures with a significant increase in the load on the base;
find out the reasons for the appearance of displacement of structures, distortions of openings, cracks in the walls of the building.

The integrity of the foundation, which “holds” the entire structure, is a guarantee of strength, which is why it is so important to inspect it correctly.

Why is there a need to dig a foundation pit in Moscow and the region?

Reasons that can lead to damage to the foundation from our experience:

natural aging of the structure - long-term temperature changes, freezing, humidity, long-term operation of the structure affect the strength of building materials;
flooding of the foundation, washout of soil, having any origin - be it a break in a water pipeline, a rise in the groundwater level, erosion of the soil by precipitation;
exceeding the design (permissible) load on the foundation;
construction of a foundation (structure) without taking into account the geology of the soil, for example, on soils with low bearing capacity;
unprofessional reconstruction, major repairs of the building;
use of low-quality building materials.

There are other reasons why there is a need to drill pits in Moscow, in addition to the purposes of house-building research. In our practice this is:

Drilling pits for piles. The construction of a pile foundation involves the need to prepare guide holes. Qualified drilling ensures accurate installation of piles.

A pit for examining the foundation of a structure adjacent to a construction site

Most of the construction and reconstruction today takes place in densely built areas. Therefore, the Developer’s task is to minimize the impact of construction on nearby structures. Large-scale construction, installation and repair work in the neighborhood, associated with vibrations, shock loads on the ground (driving piles, the work of a soil cutter and excavator) can cause damage and even destruction of foundations (especially old ones) located near the object.

In such situations, it is necessary to lay a pit near the walls of buildings located in close proximity to the construction site.

Drilling a house pit - professionally and in a short time

At the request of research institutions, as well as individual historians, we are digging a hole in a house pit. In light of the massive fascination with history, work to find artifacts has become very relevant. Old buildings (both in use and abandoned), ruins of ancient structures (visually marked and hidden under a layer of earth) require a competent approach and compliance with the law when studying.

Our employees help lovers of antiquity and history to examine the house pit with the necessary delicacy, professionally arrange the pit of old foundations in the place of interest to the Customer to the required depth.

Number of pits during foundation inspection

IMPORTANT! Depending on the reasons why excavation of pits was required, our engineers draw up a program for examining the object, taking into account the individual characteristics of the structure.

We calculate the number of pits when inspecting foundations and designate the locations for pitting:

where obvious damage to the foundation or walls is visually determined (presence of cracks, displacements);
in places of greatest load on the base;
at columns, supports, piles;
at the joints of load-bearing walls;
for each structural element of the building.

There are proven methods that our specialists adhere to. If there is a basement, the pit of the house is placed in it - this will significantly reduce the volume of production. Our specialists dig to a depth of about 0.5 m below the exposed foundation, if this does not threaten additional destruction.

When examining the pile foundation, we arrange the excavation so that at least two sides are in the field of view: “on the corner”, “on both sides”, “along the perimeter”.

The strip foundation is exposed on one or both sides at the same time (two pits are symmetrically united under the base of the foundation).

ATTENTION! The number of pits determined by the technical specifications when examining foundations depends on many factors that cannot always be taken into account when drawing up a research program, and can be adjusted during the work process.

If the design documentation does not correspond to reality, or the excavated pits show the condition of the foundation is worse than initially expected and more data is required for processing by our specialists, the number of workings increases.

It is also impossible to say with certainty in advance whether one hole in the house pit will be dug or whether the finds in the first will require further research activities.

Working closely with the Customer, coordinating our actions and partnering with the Customer speeds up and optimizes the research process.

The specialists of our company GeoGIS LLC carry out drilling pits in Moscow in compliance with the requirements of the law, construction supervision authorities, and monitor the implementation of safety precautions for their employees and other persons who find themselves at the work site.

We take the necessary measures to ensure that research does not harm the object of study. Upon completion of the work, in accordance with current regulations, we fill the pit with soil with mandatory layer-by-layer compaction.

The foundation is the foundation of the house. It depends on it how durable the structure will be. It takes on the load-bearing load, distributing it evenly over the ground. Therefore, when buying a finished house, it is important not only to look at the layout and material of the walls, but also the condition of the foundation. This is most relevant for old houses. This article will discuss how to conduct a foundation inspection.

To determine the degree of wear of the building's foundation, it is necessary to conduct an inspection. The main cases when it is important to do this:

during a major home renovation;
during reconstruction, which will inevitably lead to an increase in the load-bearing load on the foundation, for example, when adding floors;
when visible defects are detected, such as cracks or tilting of the house;
or when extensive excavation work has been carried out near the structure, which could affect the bearing capacity of the soil or the foundation itself;
after natural disasters, such as landslides, landslides, severe floods or seismic ground vibrations.

In most cases, foundation inspections are ordered to special companies that conduct a professional examination of all hidden elements of the foundation. This is a responsible and labor-intensive process that requires professional knowledge and expensive equipment. Therefore, in the case of an apartment building, it is unrealistic to independently assess the current condition of the foundation. But it is quite possible to conduct an inspection of the foundation of a small country house.

Increasingly, people are trying to escape from the bustle of the city by purchasing houses in villages and cottage communities. It is not always possible or desirable to build a house yourself or to track all stages of construction. Therefore, this real estate market is replete with offers for sale of houses. And here you need to be especially careful. It is not uncommon for homes originally built for sale to have foundation problems after the first winter. As well as old buildings, the foundations of which have become unusable due to prolonged use without proper care.

Advice: when buying a house, you need to find out how deep the groundwater is. If they are nearby, then the foundation should not have not only a basement, but also a storage pit. In winter, the water accumulated in the depression will freeze and expand, which will inevitably lead to cracks in the foundation and masonry walls.

Reasons why the foundation collapses

Unfinished construction that was stopped for several years. In particular, the concrete base will become unusable in the absence of a blind area, drainage system and drainage wells. That is, everything that is responsible for draining water.
Departure from calculations. During construction, the house plan indicates all the calculated data used to make up the technological process. And if a cheaper brand of concrete was chosen or the wrong diameter of the reinforcement was chosen, the foundation will also not be durable. Another reason is often a lack of time, due to which the required amount of time is not allocated for the concrete mixture to set.
Reconstruction work was illegally carried out inside the house, increasing the load on the load-bearing walls. Or, which happens quite often, turning the attic into a residential floor.
Constant strong vibration also has a detrimental effect. This applies to scrap sites located in close proximity to a railway or highway.

It is rarely possible to take all these factors into account in advance; sometimes they are quite unpredictable. Therefore, it is worth paying close attention to the foundation at the slightest suspicion. Unfortunately, most country houses have a decorative lining of the foundation with stone or corrugated sheets, so it is possible to see the obviousness of the problem already at a critical stage.

In addition, severe deformations of the base often occur due to natural features at the construction site. And if no changes occurred in the first year, then this may appear in subsequent years. These include:

atmospheric precipitation that easily penetrates the foundation, soaking it;
flooding of the basement with sewage water or due to leaking water supply pipes;
spring groundwater rising above the permissible value;
weak soil. For example, when filling a plot of land, they did not allow it to stand for a year and immediately began to build a house;
washing out of soil during a flood or, in the absence of insulation of the foundation, its freezing in winter.

The main method of examining foundations is trenching. During the work, samples of soil, concrete, mortar or stone are taken for research in special laboratories. They also conduct a visual inspection. There are times when it is necessary to partially destroy the foundation in order to check the condition of the reinforcement. But, for the most part, this applies to apartment buildings; you won’t need to do this in a small private house.

Inspection of a strip or column foundation

The tape is made in the form of a monolithic tape around the perimeter of the house and under its load-bearing walls. And columnar, as the name implies, is in the form of free-standing pillars connected to each other by a concrete or wooden grillage. Most often they are made of reinforced concrete, but these structures are also made of brick, rubble stone or concrete foundation blocks. The type of building material determines the technological process of examining the foundation.

The main criteria by which the quality of strip and column foundations is assessed:

Check using a laser level horizontality base along the entire length of the wall. An ordinary building level will not be suitable for these purposes, as there will be a large error;
visually inspect for the presence cracks. This may require dismantling the facing and thermal insulation layers;
When examining a concrete strip foundation, it should not be detected protruding reinforcement, large chips or delamination of the composition;

At the brick base, the masonry should look good. When signs destruction of masonry mortar and waterproofing layer, and in the absence of bricks repairs will be inevitable;
a block or stone foundation may shift when destroyed and will be immediately noticeable protrusions of individual blocks or their significant chips.

The most economical is considered to be a columnar brick foundation. It is often used for minor buildings with low mechanical loads. Therefore, the technological process is often not given due attention. But because of this, they are more often subject to destruction and repair work. It should be checked at least once a year in the spring. It is enough to simply use a plumb line to determine the vertical of the pillars along the perimeter.

Technical inspection of slab and columnar-strip foundations

Slab foundation- This is a monolithic reinforced concrete slab, poured under the area of the entire building. Depending on the expected load, a pit is dug under it. Inspection of such a base consists of an external inspection for the presence of cracks or severe mechanical damage, as well as for the evenness of the axes (first of all, distortion of the entire slab should be excluded). It is important to check the integrity of the waterproofing and the quality of the external bedding.

Columnar-ribbon the foundation is a reinforced concrete strip, which is reinforced after a certain step with pillars poured below the freezing level. When constructing it, they first dig a trench around the perimeter of the house and inside, under the future load-bearing walls. And then, they drill wells 1.5-2 m deep and insert reinforcing bars into them. They are not provided with a sand cushion, but are immediately filled with concrete. As a rule, these pillars are a strong link and additionally strengthen the foundation, so they do not need to be examined.

Visual inspection of foundations and foundations

There are many methods and devices for checking foundations. Many of them require professional knowledge, extensive excavation work and considerable financial investment. But there is a method that is accessible and simple for everyone - visual inspection. It is quite effective and sometimes only it is enough to assess the current state of the foundation.

The best time to visually inspect the foundation is spring. After going through the freeze/defrost cycle, the foundation will show itself to the greatest extent. This is where shortcomings appear that were made during construction, but were invisible.

Important: sometimes it happens that problems begin in winter. For example, when the columnar foundation of an extension to the main house freezes, it can lift the building. As a result, the porch or veranda simply warps. This is easy to notice even without examining the foundation, since the front door no longer opens easily, but rests on the floor. To avoid this, you need to make a blind area and insulate the foundation.

Stages of visual inspection in spring:

They begin by examining the soil around the foundation. It’s bad when it partially sank or even failed. Most likely, the cause was meltwater that washed away the soil. This means that the blind area was made with violations or is completely absent. Such holes must be immediately filled up and compacted;

when the base is covered with decorative cladding and it is not possible to monitor its condition, the walls of the house and window openings themselves are inspected. The presence of skew is determined by the windows, and there should be no cracks on the walls that could appear as a result of deformation of the foundation;
if there is a basement, inspect the quality of the waterproofing layer. Its damage will be indicated by white salt deposits on the walls of the basement or cellar. Over time, this will lead to constant dampness and mold in the house itself, followed by destruction of the concrete base;
Even at the stage of pouring the concrete solution, it needs to be compacted to remove air bubbles and reduce its porosity. Sometimes this moment is missed, which leads to a decrease in strength and further cracking. If a visual inspection reveals cracks in the foundation itself, then an inspection for the presence of such pores may reveal the situation. Ideally, its surface should be absolutely smooth;
An important step is the arrangement of the sand cushion. When this is not done, heaving can literally push the foundation out of the ground. Therefore, an excavation is made along the outer or inner wall of the base to its base to ensure its presence.

When all the methods described above have been carried out, but there are still doubts about the quality of the foundation, it is worth inviting specialists. He has in his arsenal a whole list of special tools that are inaccessible to ordinary people and difficult to use. In addition, laboratory examination may be required.

Tools for Inspecting Building Foundations

There is a special tool for checking concrete or screw piles. hammer for the “dream book” method. It is often used due to its compactness and ease of use. With its help, a so-called express inspection is carried out, which reveals possible cracks in a monolithic structure or soil inclusions in bored piles.
The operating principle is seismic spectral flaw detection. To do this, they hit the top of the pile with a hammer, and then the wave is reflected and transmitted to a laptop computer. If the pile does not have a crack, then the device will accurately show its total length. If there are defects, the wave will be interrupted on it.

Thus, the survey will not require dismantling the structure or carrying out expensive excavation work, and the result will be absolutely accurate without human error. This example is often used not only for piles in the foundation, but also to identify deformations of load-bearing columns of buildings, floor slabs, etc.
The usual one is also suitable for inspection. building level, which determines the vertical and horizontal of the support pillars more accurately than “by eye”. For a strip or monolithic foundation it is more convenient and expedient to use laser level, the measurement length of which is practically unlimited.
The most effective and common way to inspect foundations during reconstruction is installation of special pits. This method will most accurately show the condition of the base and the possibility of maximizing the load on it. Below we will describe this process in more detail.

Foundation inspection using pits

A pit is a small hole that is dug close to the foundation wall. Their location is determined in each case individually and depends on a number of factors. For example, it is worth installing them precisely in the places of the most noticeable deformations, and also taking into account that they do not interfere with the passage or passage of cars.
In some cases, it is advisable to dig even in inconvenient places, but all these activities are temporary and, in the presence of a large number of workers or special equipment, are carried out quickly.
In addition to boring places with obvious flaws, they are done on areas of the foundation that are subject to the greatest load, and if the house consists of several separate foundation sections, then on each of them.
For maximum reliability, the pit is made in a place where there is deformation and nearby, where the condition of the foundation does not cause concern. The obtained data is analyzed and compared.

Advice: with a partial superstructure, it is enough to check only the part of the foundation located under future construction work. And during a complete reconstruction of the building, the entire base area is examined.

If the inspection of the foundation is carried out for preventive purposes, then 2 control pits are organized. In case of the most severe deformation, it is often recommended to do them on both sides (outside and inside the basement).
They are dug quite deeply, 50-80 cm below the level of the sandy foundation pad or the screw-in level of the screw pile. When there is enough space, the walls of the pit are made at a slope, for maximum convenient work; in cramped conditions, they need to be reinforced with wooden boards and additional spacers.
The process becomes cheaper and greatly simplified when the house has a foundation. You will have to dig less from the inside, and the area of the pit is also reduced.

The pitting method allows us to identify the following parameters:

depth of the underground part of the foundation;
compliance of the width and height of the foundation with those indicated in the design documentation;
the presence of structural defects and other damage;
class of concrete mixture used when pouring or brand of stone;
vertical deviation;
the presence of additional reinforcements or previously carried out repair work;
quality of the waterproofing layer.

Drilling a columnar foundation

There may be several options for the location of the pits:

on two adjacent sides;
corner (in this case, the sides are not completely dug out, but only the corner part);

along the entire perimeter (3 sides are dug out completely, and the fourth only partially).

If we are talking about a residential building, and not a business inspection, then inspections using a pit can only be entrusted to a specialized organization. Before starting work, they do a visual inspection and check the design documentation. Based on all this, a plan is made indicating the locations of the pits and their sizes. The presence of professionals guarantees:

the work will be carried out quickly, which will prevent flooding of the foundation or erosion of the sand cushion in the excavation pestle;
upon completion of the work, the soil will be completely returned to its place and compacted, which guarantees protection against further subsidence of the earth in this place and the collapse of the blind area;
on the spot, a professional craftsman will be able to change the dimensions of the pit himself for a more reliable examination;
collection of the required samples of the required quality.

Disadvantages of the pitting method

This is a whole series of inconveniences that will be an integral part of digging holes.

Before going deeper, you will have to destroy the blind area in this place or the concrete floor, in the case when they are digging from the basement. Then restoration work will have to be carried out.
A lot of dirt and concrete dust that will remain in the air.
By exposing part of the base, humidity in the basement may increase. Therefore, if there are living quarters in it, it is recommended to remove all furniture and, if possible, insulate the trenching areas with film.
If it starts to rain heavily, the possibility of flooding cannot be ruled out. You need to keep a pump ready to pump out water in a timely manner.

The waterproofing layer will inevitably be damaged.

But all these shortcomings and inconveniences are temporary and are not so important as to abandon this method of studying the condition of the foundation.

Inspection of pile foundations

When purchasing a house built on screw piles, the foundation inspection will be slightly different. Here everything will depend on whether the house is going to be reconstructed with a subsequent load on the foundation. If yes, then it is necessary to examine it. If not, then the quality and reliability of modern screw piles is at such a level that you don’t have to worry about their condition in the ground (the exception is cheap homemade piles with a welded tip, they often begin to rust quickly).

To inspect a pile-screw foundation, you cannot do without special instruments. But the catch is that the domestic devices produced at the Chelyabinsk plant for these purposes are not only very expensive, but are not certified by the State Construction Committee. In addition, according to reviews from professionals who use them, they are not effective enough in detecting defects.

The permissible load on each pile can be calculated theoretically. But for this you need to know exactly three components: the length of the pile, its cross-section and the geological data of the soil in a particular place.
The only official recommendation that is given for testing such piles is to remove them from the ground and break them out of the grillage for testing. But if the house is residential and eviction for the period of work is not possible, then this method should be rejected. After all, if the foundation already receives the maximum permissible load, removing one support for analysis can lead to overload and serious consequences. In addition, several types of piles are often used for the construction of one building, each of which needs to be examined.

It is necessary to correctly lay the soil section (pit), the successful collection of the required soil samples depends on this.

The soil pit in plan has a rectangular outline measuring 0.8 x 1.8 m or 1 x 2 m. The depth of the pit is usually about 2 m, but can be less depending on the thickness of the specific soil profile. The pit should be positioned so that its short front wall, along which the soil should be described, is the most illuminated.

Before starting work, outline the outlines of the pit.

Then the turf is carefully cut and stacked at a distance of 2-3 m from the pit. The pit is dug with steep walls to a depth of about 0.8-1.0 m. In this case, the soil mass is thrown out only along one of the longitudinal walls of the pit. After reaching the specified depth, a step is made - a ledge of about 40 cm, then the pit is deepened another 50-60 cm and the next step is made. Usually there are two or three steps in a pit. The soil mass is thrown along the opposite, long side of the pit. Schematic view

Soil section (pit)

Upon completion of the cut, it is necessary to clean the front wall with a knife so that the soil-genetic horizons are clearly visible. A measuring tape is attached to the upper edge of the cleaned wall with a pin, which is stretched down to determine the thickness of individual horizons.

A fresh section is carefully examined, genetic horizons are identified, their boundaries are marked with a knife, and each horizon is described. A description of the soil profile and its sketch are recorded in the field diary.

1) granulometric (mechanical) composition of the soil without instruments according to the method;

2) soil color (color);

3) soil structure, composition, root system and excavation passages, new formations and inclusions;

4) field soil moisture;

CAMERA PROCESSING OF FIELD RESEARCH

Scientific processing of materials obtained as a result of field practice consists of drawing a hypsometric profile and writing a report.

The hypsometric profile is drawn on graph paper; when performing it, one should rely on previously obtained data: schematic drawings of sections, soil formation factors, etc. At the first stage of constructing the profile, an approximate topographic surface is drawn. Then soil sections are displayed on it (in the form of vertical columns). The sections depict soil horizons corresponding to the field descriptions. On the resulting schematic drawing, the necessary inscriptions are made, horizon indices, section numbers are indicated, plant associations, scale, etc. are depicted.

As an example, a complex soil profile laid across the river valley is given. Oka in the area of Tarusa, Kaluga region

Rice. 4. Soil profile

This profile gives an idea of how changes in the composition of vegetation, the type of soil-forming rock and the nature of the water regime determine the formation of soils that differ significantly in their properties and structure.

SAMPLE REPORT PLAN

Introduction.

1 . Natural conditions of the research region

1.1. Geological structure and history of surface formation. The influence of bedrock on soil formation.

1.2. Soil-forming rocks. The influence of various soil-forming rocks on the nature of soil formation.

1.3. Geomorphological structure of the territory. The influence of relief on the nature of soil formation. Basic landforms .

1.4. Climate. The influence of climate on the nature of soil formation. Basic climatic parameters of the study area.

1.5. Vegetation. The influence of vegetation on the nature of soil formation. Main plant communities of the study area.

2. Soils and ground cover

2.1. Description of soil profiles including photographs, description forms.

2.2. Detailed description of the main soil pit

2.3. Drawing of the soil profile of the selected landform (beam, river valley, etc.).

Conclusion.

Applications. Field books.

Every treasure hunter who searches for treasures in old houses knows very well that it is difficult to uncover layers of earth using traditional methods.

Also, foundation builders and repairers understand that in dense urban areas, it is quite difficult to make high-quality foundation repairs, because it is unknown what the depth of the foundation is, its type and dimensions, and even the thickness is sometimes difficult to calculate. Therefore, when it is necessary to inspect foundations, it is recommended to use trenching technology.

What is the essence of this technology

When a building has visible signs of damage associated with the destruction of the foundation, then it is necessary to determine the extent of damage to the structure and the possibility of repairing it. In such cases, it is strictly forbidden to use well drilling, because destruction may continue. In such cases, a pit is dug in several places.

A pit is a deep round hole that is dug to the maximum possible depth along the outer or inner surface of the foundation. When foundations are examined for the purpose of repair or restoration, there may be about a dozen such pits, and sometimes even more.

The pits are located symmetrically with respect to the surface; in most cases they are installed on the outside of the building, because it is difficult to dig inside.

When is it necessary to conduct a foundation inspection?

With a planned increase in the number of storeys of the building;
Changing the purpose of the building, technical re-equipment of the production building;
Major or planned repairs of the foundation associated with the appearance of visible signs of deformation of the supporting structure;
If significant cracks, deformations and subsidence of the basement floor, as well as the facade of the house, appear;
If subsidence occurs that is not related to seasonal soil fluctuations;
When designing and starting the construction of other buildings nearby;
If you need to carry out restoration work on architectural monuments, sculptures with pedestals and other similar structures.

In some cases, to examine the foundations and obtain the final result, it will be enough to study the technical documentation for the building. But for old buildings such projects simply cannot be found, because they do not exist, and construction archives were not kept then.

But when a building suffers systematic subsidence, the situation gets worse, and it is also necessary to carry out restoration of the existing building, then a full inspection of the foundation is done. And digging here will be the optimal method.

Causes of deformation and destruction of building foundations:

Rainwater that has penetrated deep into the foundation through cracks, pores or a damaged drainage system;
Aggressive groundwater contaminated with chemicals that have entered deep into the foundation from damaged sewers;
Groundwater raised above the permissible level;
When errors were made in the design of the foundation, low-quality building materials and products were used that were not designed for the design loads;
Natural aging of building materials, in particular sandstone, limestone and rubble;
Through the occurrence of third-party vibration from new industrial and administrative buildings, which affects the foundation from the outside;
Displacement of soil layers, other reasons.

The trenching method makes it possible to clearly establish the composition of the base, its depth and the composition of the mineral components. When digging, soil and foundation samples are taken at various depths, a visual inspection of the structure is carried out, and samples of building compositions are taken. It is often necessary to completely open the foundation in order to examine the condition of the reinforcement layers.

How to properly arrange pits

Considering that a pit is a hole dug vertically or at a slight angle, which completely opens the surface of the foundation, then you need to dig it correctly.

Places for installing recesses are selected individually in each specific case; priority is given to places with clearly localized damage to the base. Also, the pits can take the form of a long trench if it is necessary to examine adjacent sections of the strip base.

When choosing a digging location, you don’t need to rely only on ease of use. The inspection of foundations must be carried out in full, regardless of the complexity of the work being carried out, because the reconstruction and repair of foundations is always carried out in densely populated areas with dense buildings.

Therefore, before starting work, you need to warn others, and all such work is temporary and after a few days the pits are covered with soil again.

Inspection of bases and foundations is forced and critical in places of clearly visible critical damage. Sanding is also carried out:

in each independent part of a sectional multi-storey building;

in places where additional supports are installed.

Areas where damage to the building is considered critical also require special attention. In such cases, pits are installed not only in the emergency zone, but also in neighboring areas in order to detect reliable zones and balance the building using the load transfer method.

As a rule, when reconstructing a house, an inspection of the foundation is done along the entire perimeter of the building, but with a possible superstructure - only in a specific area.

How many pits do you need to make?

The amount depends on the degree of damage to the foundation. If it is a strip or monolithic foundation, then the holes are made every 1 meter or even closer. Also, 2-3 control samplings are always carried out in independent places, in order to then make a comparative analysis of the composition of the foundation and the soil around it.
If you only need to carry out an examination, then make 2-3 pits for every 10 meters of the length of the base.
When eliminating the influx of groundwater, holes are dug in previously dried areas of the basement or ground floor. And if the basement is being deepened, then one hole in the middle of each wall is enough.
In cases where fluctuations in the level of the base or significant subsidence are detected, double-sided pits are installed to find the cause of the subsidence.

All pits are always dug to a depth of at least half a meter below the base of the foundation.

The results of pitting can be as follows:

there is data on the depth of the underground part;
the overall dimensions of the base were obtained;
the laboratory received information about the condition of the foundation and the degree of its strength;
presence of defects and destruction;
concrete class, stone grade;
there is data on the condition of waterproofing;
you can check the geometry of the base;
Also, there will always be an increase in loads on a specific section of the foundation.

How to open foundations using the boring method

Considering that one of the walls of the pit, which is used to examine the foundations, will be the outer surface of the foundation, then there are three main options for opening them:

double-sided - then the pit is dug on both sides symmetrically and connected from the bottom of the sole. It is used if there are significant deformation subsidences or if there is a possibility of influence of excess loads from superstructures.
corner - the hole is also dug from both sides, but it does not connect and has a slight slope. The depth in such cases may not be to the very bottom of the sole. It is arranged with the same dimensions of the reinforced concrete base and the absence of the influence of sedimentary processes. When inspecting the foundations of industrial facilities, the uniformity of loads from the installed equipment and the absence of the possibility of dismantling are also taken into account.
perimetric - complete exposure of all foundation surfaces on three sides, and the fourth may not be exposed. This method is used in critical situations when it is necessary to conduct a complete inspection of the base or soil. But opening the foundation, in this case, is allowed not to be carried out immediately along the entire perimeter, but only in sections that are no more than one and a half meters long, otherwise the collapse of the building being inspected may occur.

Sometimes a situation arises when more pits are used for a small private house than for surveying a huge industrial enterprise.

The reason here lies in the following: the examination is significantly influenced by the specific conditions of analysis and sampling, as well as preliminary measurements.

As a rule, all this is done by professionals, so the human factor is reduced to a minimum. It happens that during the initial sampling, significant inconsistencies between the design and the technical documentation already arise. Therefore, additional digging is necessary.