RU2256028C1 - Method for soft ground consolidation - Google Patents

Abstract

FIELD: building, particularly for reinforcing soft and sagging ground at deep locations during building foundation construction and reconstruction, for protection of sliding natural slopes, as well as artificial dam, pit and trench slopes.

SUBSTANCE: method involves forming cylindrical cavity from ground surface; reinforcing cylindrical cavity walls by means of soil pipe and injecting hardening mix by pumping thereof into ground through injector. In the case of consolidating ground having high thickness cylindrical cavity is formed and reinforced with the use of soil pipe by vibratory driving thereof in ground. Soil pipe has auxiliary tube arranged coaxial to soil pipe and having outer diameter determined from a given relation. When soil pipe reaches upper boundary of soft ground layer to be consolidated the auxiliary tube is removed from soil pipe. Injector is deepened for the full soft ground layer thickness through the soil pipe and hardening mix is intermittently fed through the injector. After each hardening mix feeding operation injector is lifted for height corresponding to next gap to be filled with the mix. All injection operations in one consolidation point are performed during relaxation of ground compacted by soil pipe and injector driven in ground.

EFFECT: increased capacity, reduced time and labor inputs, improved technological effectiveness.

3 cl, 4 dwg, 2 ex

Description

The invention relates to the field of construction and can be used to consolidate weak and subsiding soils at great depths during the construction and reconstruction of the foundations of buildings and structures, as well as to increase the stability of natural landslide slopes, artificial slopes of dams, pits and quarries.

A known method for injecting an astringent solution, in which a bar is used. At least two holes for injection of a cementitious solution are made in the lateral surface of the rod. At least one of these holes is between the lower end of the rod and the protrusion on it. The bar is immersed in a soil base. In the process of its immersion, a stream of a binder solution is thrown out through some of the holes. Next, the bar is raised by a certain amount. During the lifting of the rod or after that through the hole located between the protrusion and the lower end of the rod, a stream of cementitious solution with a low, more than 50 kg / cm, pressure similar to a previously injected solution or belonging to a different kind is thrown out [h. Japan No. 2-35086 publ. 05/05/08 No. 4-878].

The disadvantage of this method is its restriction on the consolidation of the soil, the duration of the fixing process and the cost of the binder.

There is also known a method of strengthening the soil by injecting a hardening solution into it, according to which a cylindrical cavity in the form of a well is constructed in the strengthened soil base and the injection rod is lowered into it. By successively moving the rod through the well, a hardened solution is injected into the surrounding soil, which is ejected under pressure through the outlet of the rod. Around the outer side surface of the outer tube of the rod establish an elastic annular shell. The hardening solution enters the shell inflates it, blocking the gap between the injection rod and the wall of the well and prevents the leakage of the strengthening solution from the well along its side wall [Japanese application No. 3-3769, publ. 91.01.21 No. 4-95].

The disadvantage of this method is its duration, complexity and significant costs associated with the separation of injection by special devices that require additional technical means.

The closest and selected as a prototype is a method of strengthening the soil by injection. They construct a cylindrical cavity (well), strengthen its walls at the mouth with a pipe. After drilling, the length of the drill is injected through the drill, gradually raising it, the corresponding solution, i.e. the drill performs the role of an injector during injection in each run [A.Cambefort "Injection of soils". M., Energy, 1971, p.137-139].

The disadvantage of this method is the duration of the process, energy consumption, high consumption of hardening material associated with the sequence of creation and strengthening of the well and the method of its creation by rotary drilling, as well as phased deepening of the well, requiring drilling of already fixed upper intervals. When drilling a well, immediately to the whole greater depth of consolidation, i.e. more than 1 m, and injection of the entire well at the same time does not allow to achieve uniform distribution of the fixing solution along the length of the fixed power, and therefore the required quality, i.e. the method becomes unusable.

The objective of the invention is to develop a technologically advanced method of fixing weak soils of high power, allowing you to use the voltage of relaxation of the soil after its vibration compaction to seal the conductor pipe and injector with upward interval injection.

Technical results that can be obtained by implementing the claimed method are:

manufacturability;

energy saving;

reduction in the duration of the process;

productivity increase;

cost reduction.

The solution of the problem and the achievement of the above technical results became possible due to the fact that in the known method of fixing weak soils, including creating a cylindrical cavity from the surface, strengthening the walls of the cylindrical cavity with a conductor pipe and injecting a hardening solution by applying it under pressure to the soil through an injector in the soil high-power cylindrical cavity create and strengthen its walls with a conductor pipe by simultaneously immersing it under vibration with oh in it coaxially with an auxiliary pipe, the outer diameter of which is determined by the ratio:

D _tr. = D _{to int.} -12D ₆₀

where D _tr. - outer diameter of the auxiliary pipe;

D _{to int.} - the inner diameter of the conductor pipe;

D ₆₀ - controlling the diameter of the particles of the covering soil, which is removed from the conductor pipe when the last upper boundary of the weak soils to be fixed is reached, and through the conductor pipe under the influence of vibration, the injector is immersed at the full power of the fixed thickness of the weak soils and the hardening solution is pumped through it intervalwise each time raising the injector to the height of the next injected interval, moreover, all injection operations at one fixing point are performed during the relaxation of the densified ibropogruzhenii-conductor pipe and the soil injector.

In particular cases, the execution of the claimed method, namely, in weak clay soils, the hardening solution is injected at a discharge pressure higher than the fracturing pressure, and in weak granular soils, the hardening solution is injected under pressure below the hydraulic fracture at the fixation point, while vibration is applied to the soil particles. Vibration to the soil particles is transmitted through the injector when it is raised with the vibrator turned on.

The claimed combination of essential features is not known from the previous technical level and allows you to create an optimal method of fixing weak soils, including high power, in terms of manufacturability and technical results.

The combination of operations to create a cylindrical cavity with the surface while strengthening the walls of this cavity with a conductor pipe increases the manufacturability of the method.

Using vibration to create a cylindrical cavity and immersing the injector can increase productivity and reduce energy consumption. The use in the method of the operation of simultaneous immersion under the influence of vibration of the auxiliary pipe and conductor pipe ensures the rapid formation of a cylindrical cavity without removing soil to the surface, and the normative gap between the pipes, determined by the dependence

D _tr. = D _{to int.} -12D ₆₀ ,

provides free extraction of the auxiliary pipe from the conductor pipe when reaching the last upper boundary of the fixing zone, due to the formation of a natural balance of soil particles of a control diameter in the gap between the pipes at the lower end of the conductor pipe, which prevents the soil from penetrating into the gap and wedging the pipes together .

These measures provide optimal conditions for the injection of the injector through the conductor pipe to the design depth under vibration and reliably protect the fixing solution from breaking through to the surface during injection.

Due to the use of vibration energy in the soil in the process of creating a cylindrical cavity and deepening the injector along the conductor pipe and injector, a zone of compacted soil is formed, which accumulates the energy of vibration compaction. Stable relaxation of soil compacted during vibration immersion of the conductor and injector is observed for three days and provides reliable compression of the conductor pipe by the soil, which prevents the solution from reaching the surface, and compression of the injector to separate injection intervals.

The claimed method is illustrated by the following figures:

Figure 1 The initial stage of vibration dredging of the conductor pipe and auxiliary pipe;

Figure 2 Stage of vibration dredging of the conductor pipe and auxiliary pipe to the upper boundary of weak soils to be fixed;

Figure 3 Stage of vibration extraction of the auxiliary pipe;

Figure 4 Stage injection.

The claimed method of strengthening weak soils is as follows.

On the lower end of the auxiliary pipe 1 (Fig. 1), a conical plug 2 is installed according to the known technology with the top 3 of the cone down. The diameter of the base 4 of the conical plug 2 is equal to the diameter of the auxiliary pipe 1.

Install the auxiliary pipe 1 with a conical plug 2 inside the conductor pipe 5 coaxially with it, and the base 4 of the conical plug is placed in the plane of the lower end of the conductor pipe 5, after which the upper ends of the auxiliary pipe 1 and the conductor pipe 5 are connected by quick-detachable connection 6.

The resulting layout of the upper end of the auxiliary pipe is connected to the vibrator 7 using a trailing device 8 and immersed under the influence of vibration in the soil to the upper boundary of the weak soils to be fixed (figure 2).

After that, the auxiliary pipe 1 is disconnected from the conductor pipe 5 and, under the influence of vibration, removed from the conductor pipe. The auxiliary pipe 1 is easily removed from the conductor pipe 5 due to the calculated value of the external diameter of the auxiliary pipe 1 D _tr.external = D _{to int.} -12D ₆₀ , providing a gap 9 between them, equal to 6D ₆₀ , where D ₆₀ is the controlling diameter of the particles of the coating soil 10, resulting in the process of immersion of the conductor pipe 5 in the gap 9 between the outer surface of the auxiliary pipe 1 and the inner surface of the conductor pipe 5 at the level of the conical plug 2, a set of natural equilibrium is formed from particles D ₆₀ , which does not allow the soil to penetrate into the gap 9 and to wedge the auxiliary pipe 1 and the conductor pipe 5 between themselves.

When immersing the conductor pipe 5 and the auxiliary pipe 1 under the action of the vibro driver 7, the soil at the contact with the conductor pipe is compacted to a distance of three external radii of the cross section of the conductor pipe 5 (Fig. 2) and takes in vibration energy that is stored in the soil for up to 3 days after which it gradually relaxes to the natural background of stresses.

The auxiliary pipe 1, removed from the conductor pipe 5, is disconnected from the vibrator 7, and the injector 11 is connected to it (Fig. 4) and, through the conductor pipe 5, is immersed under vibration in a fixed weak soil 12 at the design fixing depth. Injection is carried out as follows: raise the injector 11 to the height of the fixed interval 13 and pump the calculated amount of hardening solution under pressure, then again raise the injector to the height of the next interval and repeat the injection, as a result of which, in the end, an array of fixed soil of the required shape and bearing capacity is created.

In special cases of execution, the hardening solution is injected into the fixed interval, for example, 13 under pressure above the hydraulic fracturing pressure, if clay soils are weak, or under pressure below the hydraulic fracture pressure at the fixation point, but with the application of vibration to the soil particles, if weak soils are granular.

The practical applicability of the claimed method of strengthening weak soils is shown by the following performance examples.

Example 1

The two-story administrative brick building is a monument of culture and construction on a strip foundation. The base is composed of subsidence loam with a thickness of up to 12 m and partially chalk. Soaking has led to uneven subsidence and the formation of cracks in the bearing walls.

Strengthening weak subsidence soils of high power was carried out as follows.

The diameter of the constructed cylindrical cavity was selected 89 mm, the outer diameter of the conductor pipe was 89 mm, and the vibrator was brand VB-7.

In the basement of the building, a conductor pipe 1.4 m long is used.

In the end parts of the building, where basements are located 2.5 m deep, conductors pipes 2.8 m long were installed. The external diameter of the auxiliary pipe is determined by the ratio.

D _tr.vnesh = D _{to vnutr.} -12D ₆₀

where D _{to int.} -77 mm;

D ₆₀ - 0.1 mm

D _tr.vnesh - 75.8 mm;

The filtration coefficient of 0.007 m / day.

An assembly is assembled from a conductor pipe into which an auxiliary pipe is inserted coaxially, on the lower end of which a conical plug is installed with the top of the cone down. The diameter of the base of the conical plug is equal to the outer diameter of the auxiliary pipe, and the base of the conical plug is placed in the plane of the lower end of the conductor pipe. Both pipes are immersed at the same time under vibration until the upper boundary of the fixed soft soils is reached, i.e. to the bottom of the foundation. After that, the auxiliary pipe with a conical plug is removed under the action of vibration. An injector is deepened through a conductor pipe to the design depth, and through it, the hardening solution is injected intervalwise after 0.5 m, raising the injector before injection to the height of the fixed interval. After injection, the injector and conductor pipe are removed.

Fastening was performed at 103 points, the volume of injectors was 846 m, 143 m ^{3 of} soil was fixed, cement consumption for the entire scope of work was 58 tons. 36 teams / shifts were spent on the work. Control monitoring of the state of the building for four months did not show any deviations from the moment the completion of the fixing work.

Example 2

The reinforcement of the foundations of columnar foundations composed of fine- and medium-grained unconsolidated sands was carried out during the construction of the building of the metallurgical plant workshop from the surface of the bottom of the pit to a depth of 5.0-10.5 m using the vibration-injection method at a pressure of injection of cement mortars from 0.05 to 0.1 MPa which is 1.6 times lower than the calculated fracture pressure.

The immersion and extraction of the injector was performed with the application of vibration while continuously injecting cement mortar through the injector. Injection at each point was performed in one double pass of the injector to the entire depth of the fixed thickness of the decompressed granular soil. Injection performed at 451 points. The volume of the fixed soil is 948 m ³ .

Vibration has a weighing effect on the soil particles, which allows the cement slurry to freely fill the pore space of the soil, mix with it, forming, after hydration of the cement, a high-strength cement soil in the design consolidation volume.

The combination of the operation of immersion and extraction of the injector with the process of injection of the fixing solution more than 1.5 times reduced the fixing time, increased labor productivity when performing injection work and its manufacturability, reduced the cost of fixing the foundations of the foundations and reduced energy costs.

As can be seen from the examples, the claimed combination of essential features allows us to solve the problem and create a technological way of fixing weak soils of high power, which allows using the stress of soil relaxation after vibration compaction to seal the conductor pipe and injector with upward interval injection, which ensures the achievement of the expected results.

Claims (3)

1. The method of fixing weak soils, including creating a cylindrical cavity from the surface, strengthening the walls of the cylindrical cavity with a conductor pipe and injecting a hardening solution by feeding it under pressure into the soil through an injector, characterized in that its walls create and strengthen the cylindrical cavity in high power soils conductor pipe by simultaneously immersing it under vibration with a coaxial auxiliary pipe placed in it, the outer diameter of which is determined by the ratio D _tr. = D _{to int.} -12D ₆₀ where D _tr. - outer diameter of the auxiliary pipe; D _{to int.} - the inner diameter of the conductor pipe; D ₆₀ - controlling the diameter of the particles of the covering soil, which is removed from the conductor pipe when the depth of the upper boundary of the weak soils to be fixed is reached, and through the conductor pipe under the action of vibration the injector is loaded to the full capacity of the fixed thickness of the weak soils and through it the hardening is pumped in an interval solution, each time raising the injector to the height of the next injected interval, and all injection operations at one fixing point are performed during the relaxation time nennogo with vibration immersion of the conductor and soil injector. 2. The method according to claim 1, characterized in that in weak clay soils, a hardening solution is injected at a pressure above the fracturing pressure. 3. The method according to claim 1, characterized in that in weak granular soils, a hardening solution is injected at a pressure below the hydraulic fracturing pressure at the fixation point, while vibration is applied to the soil particles.

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