RU2537448C1 - Reinforcement method of foundations of buildings on structurally unstable soils and soils with karst formations - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: first, size and depth of a karst formation under a building foundation is determined; then, the first type of wells is formed along the building perimeter at least in one row; injectors are introduced to each of the above wells and a hardening solution is injected into well walls. Wells are formed so that at injection between adjacent wells in the row there can be formed intersecting zones of compacted soil; in the lower zone of loose soils of geomassif, which are located around a karst formation caving zone, there formed are at least two rows of wells of the second type, which are located in an arch periphery line, into which there also pumped is a hardening solution by means of injectors, so that wall-shaped structures are formed by means of the hardening solution throughout the height of the karst formation out of intersecting solid elements that are flat as to vertical direction. Then, in the lower zone of loose soils of geomassif, which are located above dome-shaped arch of the karst formation caving zone, there formed is the third type of wells located along the imagined surface of the dome-shaped arch of the karst formation and going beyond the perimeter of the zone enveloped with wells of the second type, to which there also pumped is the hardening solution by means of injectors, so that a dome-shaped massif of at least one layer of intersecting flat-parallel elements is formed above the karst formation with formation of compacted geomassif above the dome-shaped massif. After that, at least one well of the fourth type is formed with its opening to the cavity of the karst formation, which is filled with the hardening solution, with formation in the cavity of the karst formation of a volumetric elements; at availability of suffusion processes in the karst formation, to the karst formation cavity there added is at least one flexible envelope, to which the hardening solution is pumped, after hardening of which the soil is additionally compacted above layers of flat-parallel elements of the dome-shaped massif by pumping of the hardening solution in a downward or upward direction to cracks and cavities formed during formation of a dome-shaped arch out of flat-parallel elements. Cement mortar and/or raw mix containing a siliceous component, a gas-forming agent and a mixing agent is used as a hardening solution.

EFFECT: improving reliability of reinforced geomassif; reducing labour input and material consumption at its formation.

8 cl, 4 dwg

Description

Technical field

The inventive method of strengthening the foundations of buildings on soils with karst formations relates to the field of construction, in particular to technologies for strengthening subsidence, structurally unstable and weak karst soils at the base of the foundations of buildings and structures.

State of the art

Soils with karst phenomena are unreliable for any kind of engineering structures, because the bearing capacity of soils at the borders of karst formations decreases due to the softening of the soil around the latter and the increase in pressure in the base when redistributing the load on the soil from buildings and structures.

The width of the zone of the weakened base around the karst formation is determined depending on the type of soil, its condition and the depth of the dip and is determined according to table 9 (Metelyuk N.S., Buchinsky Yu.L., Kovalenko M.A., Gorovensova T.G. Design and protection of industrial buildings in special conditions. Kiev, Budivelnik, 1984, p.21, Fig. 5).

There is a method that provides for the creation of a foundation in the form of a pile field, slowing down the growth of a karst funnel (one of the types of karst formation) in case of its occurrence. The distance between the piles should not exceed 1/3-1 / 5 of the diameter of the predicted funnel, and their length should exceed the possible depth of the dip by 0.5-0.7 m. The stability of the structure can be provided by increasing the supporting surface of the foundation by arranging a backup number of bearing elements console type. (one).

The main disadvantage of this method is the inability to increase the strength of the soil base, because the presence of piles in a pile field does not preclude the possibility of a specified dispersion of piles in a pile field and their length does not take into account the heterogeneity of the soil of the base and their real distribution ability.

In addition, this method is intended only for work on soils with predicted karst phenomena and does not take into account the variety of types of karst (in lithology of karst rocks, their depth, composition of the cover stratum, etc.), does not take into account the mechanisms of karst formation and does not change the conditions and soil characteristics that contribute to the continuation of karst formation processes.

There is also known a method of hardening karst soil, which is recommended to provide the possibility of filling karst funnels formed under the foundation of a building or structure, and to prevent their development, provide for the design of typical and individual buildings and structures in the floors of basements and foundations of through holes with dimensions of at least 150 × 150 mm in increments of 6 × 6 m for pumping cement mortar, concrete or cementless material. (2).

The main disadvantage of this method is the possibility of additional deformation of structural elements of buildings and structures, because the concrete filling the karst funnel mates with the unconsolidated soil, compacts it with its own weight, and the compacted soil leaves the base of the foundation. At the same time, the unconsolidated soil around the karst formation has an underestimated bearing capacity compared to the soil of the enclosing massif, and the load, due to its redistribution, has an increased one. In addition, the method of filling concrete with karst funnels is very material-intensive, since concrete has a long setting time and is exposed to the environment, which contributes to its erosion and entrainment.

The closest in purpose and technical nature to the claimed method of strengthening the foundations of buildings on soils with karst formations is a method of creating an artificial reinforced base for a building being constructed or being reconstructed. An artificial reinforced base is intended to strengthen weak water-saturated and structurally unstable soils at the base of buildings and structures and is created from hardening material in a soil massif as follows. Cement solution is injected into the soil through injectors under high pressure (5-20 atm). The solution penetrates through the hydraulic fractures caused by pressure into the caverns and cracks located between the rows of injectors, filling them, which allows to strengthen the weakest zones of the soil mass to the maximum extent. Areas into which the injection solution did not penetrate are also amplified, as they change their physical and mechanical properties: as a result of hydraulic fracturing caused by the high working pressure of the injected solution, they are compressed and compacted. Non-recoverable injectors serve as elements of vertical soil reinforcement. Monolithic with their deaf part to the foundation and entering the ground with a pointed edge, they perform the function of micro piles. (3) The installation of several injectors with different depths in one well makes it possible to strengthen the soil layers, which have their own characteristics and require solutions of different compositions, and can solve several problems at the same time: for example, strengthening the base, anti-karst measures at depth, and reducing filtration.

The main disadvantage of this method is the uncontrollability of the process of filling cavities and cracks with cement mortar, having a sufficiently long exposure time for the required set of strength. In conditions of weak water-saturated and structurally unstable soils, this can lead to large losses of cement mortar due to its direct contact with groundwater, which may be present in different layers of the soil, for example, during suffusion processes, and when fractures form cavities and cavities, they can form in directional flows.

The problem to which the claimed invention is directed is to form a reinforced geomass, in the structure of which karst formations or zones with structurally unstable soil filled with non-washable and quick-setting materials are included in the fortified geomass in the form of monolithic structures.

Disclosure of invention

The problem is solved due to the fact that in the method of strengthening the foundations of buildings on structurally unstable soils with karst formations, according to the invention, the size and depth of the karst formation located under the base of the building are previously determined, then along the perimeter of the building, at least one row, form the first type of wells, injectors are injected into each of them, injecting a hardening solution into the walls of the wells, while the wells are formed in such a way that, when injected between adjacent in the row intersecting zones of compacted soil formed in the wells, in the lower zone of loosened geomass soils located around the collapse zone of the karst formation, at least two rows of wells of the second type are formed, located along the periphery of the arch, into which, too, by means of injectors, a hardening solution is injected, forming from hardening mortar along the height of the karst formation, the similarity of walls from intersecting vertically flat solid elements, then, in the lower zone of loosened geomass soil, wedges above the dome-shaped arch of the zone of collapse of the karst formation, a third type of wells is formed, located along the imaginary surface of the dome-shaped arch of the karst formation and extending beyond the perimeter of the zone covered by the wells of the second type, into which also a hardening solution is injected through injectors, forming a dome-shaped massif above the karst formation from at least one layer of plane-parallel elements intersecting with each other with the formation of compacted geomass soil above the domed masses then, at least one well of the fourth type is formed with its exit into the cavity of the karst formation, which is filled with a hardening solution, with the formation of a volume element in the cavity of the karst formation, and if there are suffusion processes in the karst formation, at least one flexible shell into which the hardening mortar is injected, after hardening of which the soil is additionally compacted above the layers of plane-parallel domed elements of the massif by injecting the hardening mortar from top to bottom or from bottom to top into cracks and voids formed during the formation of the dome-shaped arch from plane-parallel elements, in addition, cement mortar and / or the raw mixture containing a siliceous component, a gasifier and caster.

Depending on the size of the building and karst formation, a fifth type of wells is additionally formed to compact the soil above the plane-parallel elements of the domed array, located inside the perimeter of the first type of wells and staggered indented from each other in a row and each row from each other not less than 2 m.

It is advisable that the first type of wells are spaced apart from each other in a row and each row from each other for at least 2 m

The injection of the hardening mixture in the wells of the first, third and fifth types is carried out in height in increments of 1 to 3 m.

As a siliceous component in the raw material mixture, fly ash is used with successive addition of lime-fluff, a blowing agent and a stabilizer of the mixture in the form of wood sawdust, and a surfactant-grade aluminum powder with a particle size of up to 100 μm and / or aluminum powder is used as a blowing agent.

It is preferable to use liquid sodium glass and a solution of sodium hydroxide as a substitute in the raw material mixture.

The formation of a domed vault of plane-parallel elements is simultaneously in all directions from the vault point with a maximum depth to the highest point of the vault.

In addition, the formation of a dome-shaped vault of plane-parallel elements can lead simultaneously in all directions from the highest point of the vault with a minimum depth to the lowest point of the vault with a maximum depth, respectively.

The technical result of the claimed method of strengthening the foundations of buildings on soils with karst formations is to increase the reliability of the fortified geomass and reduce the complexity and material consumption during its formation.

The formation of the lower zone of the domed-shaped reinforced geomass from closed flat-parallel hardened soil-cement or aluminosilicate elements formed in the upper loosened soil layer along the imaginary surface of the dome-shaped arch and resting on the similarity of walls formed earlier around the karst formation from intersecting vertical solid vertical elements stable foundation, over which subsequent filling of caverns and cracks in the area of loosened soils above rusty formation or zone of structurally unstable soils, and then cavities of karst formations with a hardening solution, the raw mix of which includes a siliceous component, a gasifier, and liquid sodium glass and a solution of sodium hydroxide as a hardener.

The reaction of the selected blowing agent - aluminum powder - with aqueous alkaline solutions proceeds with the release of gaseous hydrogen and a large amount of heat, which leads to boiling of water and rapid foaming of the reaction mass and allows the formation of aluminosilicate elements formed in the method in the form of porous foam silicate of structural purpose not subject to suffusion processes .

The reaction rate depends on many factors: the pH of the aqueous medium, the viscosity of the closed dough, the content of the blowing agent and the size of its particles.

The foaming process in the sealed mass is accelerated with increasing pH of the curing agent - liquid sodium glass with the addition of a solution of sodium hydroxide.

The sodium hydroxide solution acts as a carrier of water, lowering the modularity of water glass, increases the pH of the medium and is also a regulator of setting and hardening of the binder, which is used as fly ash.

The introduction of lime also increases the alkalinity of the solution, providing a vigorous course of the reaction of gas formation.

3Ca (OH) ₂ + 2Al + 6H ₂ O = 3CaO · Al ₂ O ₃ · 6H ₂ O + 3H ₂

When using the specified raw material mixture for filling cavities and cracks in the area of loosened soils and pumping them through the injectors in the indicated sequence, as a result of reaction with aqueous alkaline solutions of the selected blowing agent - aluminum powder with particle sizes from 50 to 100 microns, hydrogen gas is released leading rapid foaming of the reaction mass and within a short time period, aluminosilicate elements insoluble in the aqueous medium are formed, according to the rate of curing, and, consequently In particular, in terms of bearing capacity, they are ahead of the formation of soil-cement elements. In this case, the reaction of the raw material pumped into cavities and cracks containing a silica component with a blowing agent, which is used as an aluminum powder, and with a liquid sodium glass and a solution of sodium oxide hydrate, is accompanied by the release of a large amount of heat, which leads to boiling water and a sharp increasing pressure up to 40 atm, which creates conditions for compaction of soils falling into the space between the formed aluminosilicate elements.

Due to the formation of a supporting similarity of walls from vertically flat elements and a dome-shaped layer resting on it from closed plane-parallel soil-cement or aluminosilicate elements in the lower zone of loosened geomass soils located above the surface of the karst formation or zone of structurally unstable soil, and subsequent formation in the layer of loosened soil of aluminosilicate elements, between which inclusions of compacted soil are located, a monolithic geomass is created, providing s increasing its reliability.

If there are water flows in the karst cavities (for example, during natural or technogenic suffusion processes), flexible coatings can be introduced into the karst formations before feeding the hardening solution into the zone, into which the hardening solution is supplied.

The inventive method of strengthening the foundations of buildings on structurally unstable soils and soils with karst formations using the above raw material mixture was tested during the implementation of the project to strengthen the geomass in Moscow, on the right-bank region of the Yauza River and is illustrated by the sketches and figures below.

Brief Description of the Drawings

The present invention is illustrated by drawings, where:

In FIG. 1 shows the layout of the injectors along the section of the reinforced

grounds;

in FIG. 2 - an arrangement of injectors in the plan along the site of the reinforced base;

figure 3 shows the structural diagram of the strengthening of the base of the building in the field of karst formation - a vertical section of the geomass;

figure 4 shows a schematic vertical section of a reinforced geomass.

The implementation of the invention

A method of strengthening the foundations of buildings on structurally unstable soils and soils with karst formations is as follows.

In the pre-design geophysical studies of soils at the base of the building, methods were used that take into account the experience of karst monitoring, for example, the method of electric one-way sounding (OZ) in two directions.

In electrical exploration works using the OZ method at the research site, characterized by the limited and cluttered area of neighboring buildings and technical communications, the ERA electrical exploration equipment was used.

As a result of the studies, a characteristic system of zones of increased fracturing was identified, and two canopy caving at two depths of 38-48 m in limestones of the Podolsk-Ballivsky aquifer were recorded at two intersections of the cracks. Table 1 below provides a description of the collapse domes.

Table 1 Characterization of caving domes Karst formation location Diameters of formations in m Estimated height of formations in m The bases of the domed vault Filtration funnel formation Arch in the northern part of the surveyed site 1.8 3.0 4.0 Limestone caving in the area adjacent to the survey site from the south 1,2 2.0 6.0

According to the results of a survey of territories adjacent to the surveyed site, and when assessing the density of distribution of arches on the surveyed site, it was found that the density of manifestation of karst formations in the form of arches of rock collapse in the limestone mass is about 0.6 per 100 m ² . When taking into account cavity sizes of more than 1 m (i.e., they are potentially hazardous), the territory subject to soil hardening, according to the requirements of SP11-105-97 t. P, t.5.1, has the V category of stability with respect to the intensity of the formation of karst dips. The result of the soil survey is shown in Figure 1.

According to the above data of the pre-project survey of the territory, a sequence of strengthening the soil layers above the arch in the northern part of the site and in the formation zone in the form of a filtration funnel on the south side has been developed, which is reduced to the following.

On the fortified site at the base of the building (Fig. 1, 2), the territory of which was at least 1000 m ² , two rows of wells of the first type 1 were formed around the perimeter, located at a distance from each other in a row of at least 3 m, in which injectors 2 are introduced for forming a shielding wall 4 of soil-cement or aluminosilicate elements formed by a hardening mixture pumped through injectors 2. On the fenced area in the zone of karst formation 5, along the periphery of the arch, two rows of wells of the second type 6 are formed, into which, by means of injectors, a hardening solution is also injected, forming from the hardening solution along the height of the karst formation a similarity of the walls 7 of intersecting solid vertical flat elements. At the same time, the depth of injection of injectors 2 into wells 1 along the perimeter of the site to be strengthened and injectors 2 in the zone of karst formation 5, i.e. within the territory enclosed by the wells of the first type 1 (Figure 2), the area was not less than 48 m. In the collapse zone 8 of the soil in the form of a dome-shaped arch with the formation of cavity 9, wells of the third type 10 were formed, the lower bases of which formed an imaginary surface at the maximum depth of the fracture zone a domed arch of karst formation extending beyond the perimeter of the zone covered by wells of the second type 6. Injectors 11 were injected into the wells of the second type 6, by means of which from the raw material mixture consisting of silica above the collapse zone, a dome-shaped massif was formed from one layer (or several layers) of plane-parallel aluminosilicate elements 12 intersecting with each other and with the formation of the above reactions occurring in the pumped-in raw material mixture proceeding with the release of a large amount of water and heat, compacted geomass soil above the domed array. Then, depending on the size of the collapse zone, one or more wells of the fourth type 13 were formed with its / their passage into the cavity 9 of the karst formation. One or several injectors 11 were introduced into the volume of the cavity 9 of the latter, and through the injector / s a hardening solution was supplied (a raw material mixture containing a siliceous component, a gasifier, and a filling agent - liquid sodium glass and a solution of sodium hydroxide to fill the cavity 9 formed in it volume element 14 of aluminosilicate insoluble in an aqueous medium, which provides the necessary set of strength for a short period of time, and if there are suffusion processes in the karst formation, cavity 9 of the karst formation was introduced at least one flexible shell 15, into which the hardening solution was injected.

A similar sequence of the process of soil strengthening is applied in the zone of karst formation in the form of a filtration funnel 16 and in the caving zone 17.

After the elements 14 are cured in the cavity 9 of the karst formation and in the caving zone of the karst formation in the form of a filter funnel 16 and in the zone of caving 17, the soil is compacted above the domed vaults of the elements 12 under the entire base of the building or structure, supplying a hardening solution from top to bottom or from bottom to top natural cracks and voids of loosened soil, and are used to fill cracks and voids formed during the formation of a dome-shaped arch of elements 12 as a result of accompanying th soil compaction process. For this purpose, wells of the fifth type 18 were formed inside the reinforced site, in which, using the injectors 2 or 11 used, the hardening solution was injected from top to bottom or from bottom to top in cracks and voids formed during the formation of the dome-shaped arch from plane-parallel elements 12.

Due to the formation of a support dome-shaped layer of closed plane-parallel aluminosilicate elements 12 in the lower zone of loosened geomass soils located above the surface of the karst formation or zone of structurally unstable soil, and the subsequent formation of aluminosilicate elements in the layer of loosened soils between which inclusions of compacted soil are located, and the use of the proposed raw material mixture to strengthen the geomass, a monolithic geomass is created, providing an increase over basis, and a significant economic effect is achieved due to the use of cheap raw materials and lower energy costs for introducing the raw material mixture through injectors into the ground.

Information sources

1. Ukhov SB, Semenov VV, Znamensky VV, Ter-Martirosyan Z. G., Chernyshev S. N. Soil mechanics, foundations and foundations. - M.: Publishing house ASV, 1994, p. 466-447, Fig. 16.6, 16.7.

2. Instructions for the design of buildings and structures in the areas of Moscow with the manifestation of karst-suffusion processes. Moscow City Executive Committee, 1984, p. 149, p. 11

3. Description of patent RU for utility model No. 121274 by class. MKI E02D 3/12, application No. 2012124958/03 of 06/15/2012, published on 10/20/2012.

Claims (7)

1. A method of strengthening the foundations of buildings on structurally unstable soils with karst formations, characterized in that they first determine the size and depth of the karst formation located under the base of the building, then form the first type along the perimeter of the building, at least in one row wells, injectors are injected into each of them by injecting a hardening solution into the walls of the wells, while the wells are formed in such a way that when injected between adjacent wells in a row, intersecting In the lower zone of loosened geomass soil, located around the collapse zone of the karst formation, at least two rows of wells of the second type, located along the periphery of the arch, are also formed in the lower zone of loosened geomass soil, into which, by means of injectors, a hardening solution is also injected, forming from the hardening solution along the height of the karst formation, the similarity of walls from intersecting vertically flat solid elements, then, in the lower zone of loosened geomass soils located above the dome-shaped arch of the zone karst formation, form the third type of wells located on an imaginary surface of the domed arch of the karst formation and extending beyond the perimeter of the zone covered by the wells of the second type, into which, by means of injectors, a hardening solution is also injected, forming a dome-shaped array of at least one layer above the karst formation overlapping plane-parallel elements with the formation of compacted geomass soil over a domed array, after which form at least re, one well of the fourth type with its exit into the cavity of the karst formation, which is filled with a hardening solution, with the formation of a volume element in the cavity of the karst formation, and in the presence of suffusion processes in the karst formation, at least one flexible shell is introduced into the karst formation hardening solution is injected, after hardening of which the soil is additionally compacted above the layers of plane-parallel elements of the dome-shaped array by injection of a solid from top to bottom or bottom to top into cracks and voids formed during the formation of a dome-shaped arch from plane-parallel elements, in addition, cement mortar and / or a raw mixture containing a siliceous component, a blowing agent and a grout are used as a hardening solution. 2. The method according to claim 1, characterized in that, depending on the size of the building and the karst formation, for the compaction of soil above the plane-parallel elements of the dome-shaped array, a fifth type of wells are additionally formed, located inside the perimeter of the first type of wells, and staggered indented from each other in a row and each row from each other at least 2 m.
3 The method according to claim 1, characterized in that the first type of wells are indented from each other in a row and each row from each other for at least 2 m 4. The method according to claims 1, 2, characterized in that the injection of the hardening mixture in the wells of the first, third and fifth types is carried out in height in increments of 1 to 3 m 5. The method according to claim 1, characterized in that as a siliceous component in the raw material mixture, fly ash is used with successive addition of lime-fluff, a blowing agent and a stabilizer of the mixture in the form of wood sawdust, and a surfactant-grade aluminum powder is used as a blowing agent with a particle size of up to 100 microns and / or aluminum powder. 6. The method according to claim 1, 6, characterized in that, in the raw material mixture, liquid sodium glass and a solution of sodium hydroxide are used as a hardener. 7. The method according to claim 1, characterized in that the formation of the dome-shaped vault of plane-parallel elements is simultaneously in all directions from the vault point with a maximum depth to the highest point of the vault. 8. The method according to claim 1, characterized in that the formation of the dome-shaped vault of plane-parallel elements is simultaneously in all directions from the highest point of the vault with a minimum depth to the lowest point of the vault with a maximum depth, respectively.

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