RU2762373C1 - Method for creating a geotechnical structure in the ground - Google Patents

Abstract

FIELD: construction industry.

SUBSTANCE: invention relates to construction and can be used in the construction of underground structures by the “wall in the ground” method, in particular landslide barriers, pit fences, underground floors of buildings, tunnels and collectors for various purposes, underground passages, etc. in conditions of fractured rocks, mainly of carbonate composition. The method for creating a geotechnical wall-in-the-ground structure in the ground includes drilling of cementation boreholes, injection of hardening mortar into cracks of permeable rocks, development of a trench under the protection of drilling mud, installation of a reinforcing frame and concreting of a geotechnical structure. To prevent drilling fluid leaks into fractured permeable rocks, they are injected with a gel-forming suspension through wells previously drilled along the axis of the wall in the ground to an estimated depth below the design mark of the bottom of the wall in the ground. The suspension is prepared on the construction site by mixing the gelating composition with bentonite solution, while the composition is determined experimentally by the leakage of trial portions of the suspension, depending on the fracturing of permeable rocks, and the suspension penetrates into cavities and cracks and turns into an elastic waterproof material. At the next stage of work, during the excavation of the trench, fractured permeable rocks impregnated with a suspension that does not impair the properties of the bentonite solution and does not reduce the quality of the concrete mixture are drilled under the protection of drilling bentonite mortar, then a reinforcing frame is installed and reinforced concrete wall is concreted in the ground with concrete mixture.

EFFECT: reducing the cost and material intensity of work on the construction of a wall in the ground with a simultaneous increase in the quality of concrete.

1 cl, 3 dwg

Description

The invention relates to construction and can be used in the construction of underground structures by the "wall in the ground" method, in particular, anti-landslide barriers, fencing pits, underground floors of buildings, tunnels and collectors for various purposes, underground crossings, etc. in conditions of fractured rocks, mainly of carbonate composition.

A known method of obtaining a gel-forming composition / 1 /. The method consists of dissolving a nepheline-containing additive in a dilute acid, and the acid is diluted with mineralized chloride water with a density of at least 1.12 g / cubic cm. The time for the start of the gelation process is regulated by the ratio of the components and can vary from several minutes to several hours. The resulting gel has a high penetrating ability and is used to impregnate near-wellbore soil and eliminate water inflows in oil and gas production. The disadvantage of this method: increased consumption during the impregnation of permeable gravel and rocky soil due to uncontrolled filtration into the surrounding massif.

A known method of creating in the ground geotechnical structures, such as "wall in the ground" trench type / 2 /. In the ground, a trench is mined with a grab or geofreser under the protection of a drilling, usually bentonite, mud, which ensures the stability of the walls from collapse. The bentonite solution calmates the pores in the soil and prevents its filtration into the surrounding massif. For this, the level of bentonite mortar in the trench must exceed the level of groundwater at the construction site by at least 1.5-2.0 m. least inevitable costs. However, if at the base there are soils with caverns and voids and / or fractured rocks, then the bentonite solution goes uncontrollably into the cracks and its level in the trench cannot be maintained above the groundwater level. In such cases, the use of bentonite mortars is allowed only on condition of preliminary plugging of these rocks with cement or clay-cement mortar / 2 /. To do this, cement mortar is injected into wells, which are arranged at a slightly greater depth of the wall in the ground. Wells are drilled from both sides of the wall at a certain distance from the wall and with a calculated step. Drilling cement holes along the wall axis complicates further work on the erection of a “wall in the ground”, since during the development of a trench protected by a bentonite mortar, the drilled cement stone formed during the injection process sharply thickens the bentonite mortar and leads to poor-quality concreting. The disadvantage of the known method of erecting a monolithic concrete wall with soil, taken as a prototype, is the increased cost of work due to the forced excess volume of drilling for cementing wells.

The technical objective of the invention is to reduce the cost and material consumption of work on the construction of a wall in the ground with a simultaneous increase in the quality of concrete.

The problem is solved due to the fact that in the method of creating a geotechnical structure in the soil, such as a "wall in the soil", including drilling cement wells, injecting a hardening solution into the cracks of permeable rocks, developing a trench under the protection of drilling mud, installing a reinforcing cage and concreting the geotechnical structure, According to the invention, cementing wells are drilled along the axis of the wall in the ground, to the calculated depth below the design mark of the bottom of the “wall in the ground”, and as a hardening solution, to reduce the permeability of fractured rock, mainly carbonate, rocks, a cementless gel-forming suspension is injected, for example, along patent RU 2234598 C2, inert to bentonite drilling mud. To optimize the flow rate of the suspension, an anti-filtration calming additive, for example, bentonite powder, is introduced into it.

The method is illustrated by drawings, where FIG. 1 shows a diagram of drilling injection wells and injection of a gel-forming solution; in fig. 2 - section along the wall trench in the ground; in fig. 3 - finished wall in the ground.

An example of the implementation of the method.

It is required to build a reinforced concrete enclosing “wall in the ground” with a depth of 20 m in sandy soils underlain by fractured highly permeable limestones. Groundwater level at a depth of 15 m.

The walls of the trench 1 in sandy soils 2 must be fixed with drilling mud. To prevent leaks of drilling mud into fractured limestones 4, they are injected with a gelling suspension 5 through wells 6 pre-drilled along the axis of the "wall in the ground" to an estimated depth below the design mark of the bottom of the wall. The suspension is prepared at the construction site by mixing the gelling composition with bentonite solution. The composition is determined empirically by the care of test portions of the suspension, depending on the fracturing of limestone, in the ratio Gel: Bentonite = (5-2): 1. Suspension 5 penetrates into cavities and cracks and turns into an elastic waterproof material 7. At the next stage of work, in the process of digging trench 1 under the protection of drilling bentonite mud 3, limestone 4 impregnated with gel 5 is drilled out, which does not deteriorate the properties of bentonite mud 3 and does not reduce the quality of the concrete mix. Then the reinforcement cage 8 is installed and the reinforced concrete "wall in the ground" is concreted with a concrete mixture, which is poured through the fore-shaft 9. After hardening, the concrete mixture turns into a reinforced concrete "wall in the ground" 10.

The result of the invention is the creation of a method for erecting a geotechnical structure, such as a "wall in the ground" or a bored pile, with reduced material consumption and labor intensity of construction by reducing the number of injection wells and the volume of injection material.

Sources of information

1. RF patent No. 2234598 "Method of obtaining a gel-forming composition", IPC E21B 43/22, publ. 20.08.2004, Bul. No. 23.

2. SP 381.1325800-2018 Retaining structures. Design rules.

Claims (2)

1. A method of creating in the soil a geotechnical structure such as a wall in the soil, including drilling cement wells, injecting a hardening solution into the cracks of permeable rocks, developing a trench under the protection of drilling mud, installing a reinforcing cage and concreting a geotechnical structure, characterized in that to prevent leaks of drilling mud into fractured permeable rocks, they are injected with a gel-forming suspension through the wells pre-drilled along the axis of the wall in the ground to the calculated depth below the design mark of the bottom of the wall in the ground, the suspension is prepared at the construction site by mixing the gel composition with bentonite solution, while the composition is determined empirically for care test portions of the suspension depending on the fracturing of permeable rocks, and the suspension penetrates into cavities and cracks and turns into an elastic waterproof material, at the next stage of work in the process of trenching under the protection of drilling benton The mud solution is drilled into fractured permeable rocks impregnated with a suspension that does not impair the properties of the bentonite solution and does not reduce the quality of the concrete mixture, then a reinforcing frame is installed and the reinforced concrete wall is concreted in the ground with a concrete mixture. 2. The method according to claim 1, characterized in that the cementless gel-forming suspension contains an anti-filtration calming additive in the form of bentonite powder.

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