RU2468152C1 - Method to correct irregularities of buildings and structures subsidence on slab foundation - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method to correct irregularities of buildings and structures subsidence on a slab foundation includes setting of vertically aligned injection conductors and injection of a fluent mortar under a part of the building towards list. Prior to start of fluent mortar injection via conductors installed along the perimetre of the reinforced part of the foundation, soil is soaked to cause its weakening. Then via the same conductors injection of the fluent mortar is carried out under pressure causing a hydraulic rupture of weakened soil. After hardening of the mortar, injection of the fluent mortar is carried out inside the produced contour. Additionally the building is settled at the side opposite to list, and after balancing the building position is fixed by supply of the fluent mortar into conductors at the side opposite to the list.

EFFECT: higher efficiency in expansion of correction range for a most sunk part of a foundation, reduced material intensity.

4 cl, 3 dwg

Description

The present invention relates to construction and can be used to level unevenly settled buildings and structures on slab foundations.

There is a method of adapting a slab foundation to changing the characteristics of a soil foundation (RF patent No. 2184812, E02D 27/28, publ. 07/10/2002), comprising a device in the body of the slab of adaptive technological and measuring channels and the installation of sensors in them, with which assessment of the physico-mechanical properties of the soil and, if necessary, injection of sealing and fixing solutions in the area of low density of the soil base with an assessment of the speed of compaction and penetration of the solution into the soil, depending on pressure eniya.

The disadvantage of this method is the high complexity of the device adaptation, technological and measuring channels in a densely reinforced slab foundation, due to their large number and complexity of manufacture.

Closest to the proposed one is a method of adjusting the vertical position of buildings and structures on a slab foundation (RF patent No. 2352723, E02D 55/00, published April 20, 2009), including installing vertically oriented injection conductors and injecting a moving solution through them under a part of the building in the direction of the roll until the supply pressure increases by 40-50% with respect to the working pressure or until the flow of the mobile solution in the volume of 2 m ³ on one injection horizon.

A significant disadvantage of the method according to patent No. 2352723 is the injection pressure threshold, which may be insufficient to achieve the desired compaction of the base soil. As follows from the abstract of the patent, the moment of completion of injection is governed by two parameters: either the time when the pressure increases by 40-50% with respect to the worker, or the flow rate of the mobile solution in a volume of 2 m ³ on one horizon. From the description it follows that in the case of a further increase in injection pressure, instead of compaction of the soil, new slit-like ruptures of the soil base with uncontrolled spread of the mobile solution are formed. It was found that after the end of injection, under this condition, the maximum compaction pressure can reach a value of no more than 5.6-6.0 atm. Under this condition, the method may be suitable only for the adjustment (termination of further precipitation) of small buildings and structures. However, at a pressure of the feed solution of 5-6 atm, the density of the soil will be insufficient to stop further settlement of the building with high pressure on the ground. However, it is impossible to raise the settled part of the building and thus correct the roll by high-pressure injection at any arbitrarily high pressures.

The technical problem solved in the present invention is to increase efficiency while expanding the range of adjustment of the most sagging part of the foundation.

The problem is solved in that in a method for correcting uneven precipitation of buildings and structures on a slab foundation, including the installation of vertically oriented injection conductors and the injection of rolling mortar under a part of the building in the direction of the roll, before starting the injection of rolling mortar through conductors installed around the perimeter of the reinforced part of the foundation, soaking the soil, causing it to weaken, then through the same conductors inject the mobile solution pressure Causing fracturing the weakened soil, and after solidification produce injection solution within the resulting solution of the movable circuit. Additionally, the soil is soaked from the side opposite the roll. After alignment, the position of the building is fixed by supplying a moving solution through the same conductors from the side opposite the roll.

In the process of carrying out works and after their completion, it is advisable to control the pressure of the rolling solution, and before starting work, in the process of carrying out them and after finishing - monitoring the settlement of the building using geodetic instruments.

Preliminary soaking of the soil and subsequent injection of the mobile solution with pressure causing hydraulic fracturing of the soil along the contour of the sagging part of the foundation will ensure the creation of a strong curtain that will allow the injection of the mobile solution directly under the sagged part of the foundation inside the resulting circuit under high pressure, eliminating uncontrolled leakage of the mobile solution.

The degree of soil moisture characterizes the indicator of soil consistency, which is determined according to GOST 25100-95 (Designer Guide. Foundations, foundations and underground structures. M: Stroyizdat. - 1985. - p.10-12.),

Where

W - natural humidity;

W _L - moisture at the yield stress;

W _p - humidity at the rolling border.

Clay soils can be hard, plastic and fluid depending on their consistency. Obviously, a less moistened soil with a lower consistency index will have increased values of ultimate loads (pressures) at which hydraulic fracturing of the soil occurs under increasing solution pressure.

In the general case, for an approximate assessment of strength characteristics, schematized strain curves are widely used, in which the soil is perfectly elastic-plastic (Prandtl diagrams). A strain diagram of this kind consists of two straight sections - at stresses below the proportionality limit σ _T , Hooke's law is observed, and then fluidity arises. According to the Prandtl diagram, it follows that when fluidity occurs, stress growth stops.

Figure 1 shows the location of the conductors around the perimeter and inside the strengthened zone, figure 2 is a diagram of the deformation of the same soil, characterized by different values of the indicators of consistency, figure 3 is a diagram of the possible options roll.

The proposed method is as follows.

The zone of the reinforced part of the foundation is determined and the arrangement of vertically oriented conductors 1 (Fig. 1) is selected along its perimeter, and vertically oriented conductors 2 (Fig. 1) inside the zone. Before starting work, it is advisable to determine the characteristics of the soil, assess the stress-strain state and, based on the data obtained, draw up a layout and the required number of conductors involved to implement the proposed method. Through conductors 1, the soil is soaked with water under pressure. In figure 2, curve 1 shows a diagram of soil deformation after soaking, curve 2 - deformation of soil with natural humidity. As can be seen from the presented diagrams, the soil after soaking becomes less durable and the achievement of the yield strength in it and fracture fracturing will occur earlier and at lower pressures. Water supply is continued until the neighboring soaking zones 3 (Fig. 1) are closed with each other, forming a continuous contour of weakened soil. Since the injectors have an omnidirectional effect, the soaking around each of them occurs in a radial direction whiter or less evenly, forming soil soaking zones that are similar in appearance to cylindrical. The zones overlap with each other, forming a continuous contour channel of weakened soil, characterized by a lower yield strength.

After that, through the same conductors 1, the mobile solution is injected with pressure, causing hydraulic fracturing of the weakened soil. In this case, the destruction of the soil and the passage of the mobile solution is carried out mainly in the direction of the previously obtained contour channel, since the soil in it has a lower yield strength, which will be overcome sooner than this will happen in stronger soil. Thus, the entire feed solution at the stages of compaction and hydraulic fracturing remains inside the zone of weakened soil. A more dense soil inside the formed contour is compacted by internal pressure, but retains its integrity. The moment of completion of the supply of the moving solution through the conductors 1 can be determined by the pressure curve. It was experimentally established that hydraulic fracturing is preceded by an increase in solution pressure. The increase in pressure continues until the process of cracking in the soil occurs with the filling of the newly formed volumes with a solution. This moment corresponds to a sharp "spasmodic" drop in pressure.

After the filing of the mobile solution through the conductors 1, make a temporary exposure, providing complete solidification of the solution. The hardened mortar forms a closed loop around the intended area of the foundation.

Then, through the conductors 2, the mobile solution is injected inside the resulting circuit. The previously formed closed loop eliminates the possibility of uncontrolled leakage of the mobile solution, therefore, the injection of the mobile solution inside the circuit is carried out with high pressure, providing a high degree of soil compaction, which will allow for more efficient adjustment of the position of the foundation slab. In-circuit pressure when using the proposed method can reach values up to 20 atm.

An increase in the rigidity of the base under the settled area of the slab foundation by injection is associated with soil compaction - a decrease in porosity. The main indicator of the degree of compaction of the soil or the amount of injected solution is the final pressure. It was found that the soil can be compacted only to a certain limit, after which further injection of the solution leads to hydraulic fracturing. At the time of hydraulic fracturing, a sharp drop in pressure is recorded on the manometer due to violation of the continuity of the medium and the formation of new volumes in it in the form of normal fractures. Further injection of the solution does not cause an increase in pressure, since the solution uncontrolledly flows through the newly formed cracks and the soil after hydraulic fracturing becomes less compacted. Using the proposed method will allow to pump a larger amount of a solution with a higher pressure due to the formation of a circuit that prevents the flow of the supplied solution outside the sealing zone.

The foundation foundation thus strengthened will ensure a reliable cessation of further settlement of buildings and structures, regardless of the amount of pressure exerted by them on the ground.

After stopping the building upset, the bank is liquidated, for which soil is soaked from the side opposite the bank. In this case, the soil is weakened and under the influence of the dead weight of the building being leveled, its sediment from the side opposite to the roll occurs. At the end of the alignment, the position of the building is fixed by supplying a moving solution to the same conductors into which water was supplied to soak the soil (not shown in Fig.).

Before, during and after completion of the work, the position of the building is monitored using geodetic instruments.

Due to the fact that under the sole of the foundation slab, the soil has a range of physical and mechanical properties (consistency, porosity, density, etc.), as well as due to the heterogeneity of the over-base load, precipitation can be uneven.

Figure 3 shows three varieties of sediment foundation:

1 - precipitation at points A and B are not equal to zero, but uniform;

2 - precipitation is not equal to zero ahead of point A;

3 - precipitation increases only at point A.

The first option does not constitute a danger during the operation of the structure, therefore it is not considered.

To prevent skewing in the second embodiment, it is necessary to carry out the following operations:

- by the method of high-pressure injection, stop the process of further settling of the foundation plate at point A;

- make a time delay until the precipitation at point B under the building’s own weight becomes equal to the recorded precipitation at point A;

- after the bank has been eliminated, fix the position of point B through the conductors under the sole of the foundation of the hardening mortar under pressure;

With the third option, it is necessary to carry out the following operations:

- stop the process of subsidence of the foundation slab by increasing the rigidity of the base at point A;

- from the side opposite to the heel (point B) by soaking, loosen the soil and cause the foundation plate to settle under its own weight;

- similarly, after a temporary pause and elimination of the roll, fix the position of point B with a hardening solution.

Used in the proposed method, the method of settling the plate from the side opposite the roll is more preferable in comparison with the leveling method by lifting the most sagging point A, for example, using jacks.

Claims (4)

1. A method of correcting uneven precipitation of buildings and structures on a slab foundation, including the installation of vertically oriented injection conductors and the injection of rolling mortar under a part of the building in the direction of the roll, characterized in that before starting the injection of rolling mortar through conductors installed around the perimeter of the fixed part of the foundation, soaking the soil, causing it to weaken, then through the same conductors inject the mobile solution with pressure that causes hydra breakdown of the weakened soil, and after the solution has solidified, a mobile solution is injected inside the obtained contour, the building is further precipitated from the side opposite the roll, and after alignment, the building position is fixed by supplying the mobile solution to the conductors, from the side opposite the roll. 2. The method according to claim 1, characterized in that the draft from the side opposite the roll, is carried out by the influence of the dead weight of the building being leveled. 3. The method according to claim 2, characterized in that before the precipitation is carried out, the soil is soaked. 4. The method according to any one of claims 1 to 3, characterized in that during the work and after they are completed, the pressure of the rolling solution is monitored, and before the work is started, in the process of their work and after it is completed, the building’s settlement is monitored using geodetic instruments .

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