RU2785603C1 - Injection solution for fixation of sand-containing massif - Google Patents

Abstract

FIELD: earthworks.

SUBSTANCE: invention relates to injection compositions for hardening soils by an impregnation method; it can be used for fixation of sand dusty soils in conditions of natural occurrence, forming slope massifs on landslide and landslide-prone areas, as well as on slopes of artificial recesses and pits. An injection solution for fixation of sand-containing massif includes, vol.fr.: binder – aliphatic epoxy resin 100, curing agent – polyethylene polyamine 16-40, plasticizer – solution consisting of silica 75 and water 225.

EFFECT: increase in the strength of fixation of particles of sand-containing massif with an injection solution, increase in a penetrating capability of the injection solution.

4 cl, 3 tbl, 1 ex

Description

The invention relates to injection compositions for strengthening soils by impregnation and can be used to fix sandy soils of dusty, small and medium size, located in natural occurrence and forming slope massifs in landslide and landslide-prone areas, as well as on the slopes of artificial excavations and pits.

Known injection solution for fixing the array of soil, including the main component, represented by epoxy resin, a hardener, represented by polyethylene polyamine (PEPA), and a plasticizer, represented by a solvent, while the total ratio of components is, wt.h:

epoxy resin 60-100 PEPA 12-28 solvent 100-280

[SU620532 A1, publication date: 12/15/1981, IPC: E02D 3/12].

The disadvantage of the known technical solution is the high fire hazard of the injection solution when working with it, due to the low flash point of the solvent, which is 25-27 ° C, at which the concentration of flammable solvent vapors, which also have high toxicity, is significantly increased, as a result of which such a solution is not suitable for work. with him inside closed mine workings and tunnels.

As a prototype, an injection solution for fixing an array of soil was selected, including the main component, represented by an aliphatic epoxy resin, a hardener, represented by PEPA, and a plasticizer, represented by a 50-100% sodium chloride solution, while the total ratio of components is, wt.h:

aliphatic epoxy resin 100 PEPA 16-28 50-100% NaCl solution 300-400

[SU889792 A1, publication date: 12/15/1981, IPC: E02D 3/12].

The advantage of the prototype over the known technical solution is the lower fire hazard of the injection solution due to the use of sodium chloride solution as a plasticizer.

However, the disadvantages of the prototype are: a high risk of suffosion deformations of the soil in the sandy massif fixed by this injection mortar, as well as the high aggressiveness of the components of the solution to concrete and reinforced concrete structures. The disadvantages of the solution are due to the high content of sodium chloride in it, which can be subject to leaching by ground and surface waters, which does not allow the use of this solution for fixing a sand-containing mass in the soil aeration zone, and the presence of sodium chloride salts in the fixed mass increases the solubility of the concrete components, from which can be made buried in the mass of the foundation of buildings and structures, which significantly reduces its strength and significantly degrades the performance of the injection solution for fixing the sand-containing mass. In addition, the component composition of the solution according to the prototype does not provide high penetrating power due to the relatively high initial viscosity of the solution, which makes it difficult to introduce it into the arrays formed by fine or silty sand.

In view of the foregoing, it is required to create an injection mortar that is fireproof and non-aggressive to concrete and reinforced concrete structures, which, simultaneously with reducing the risk of suffusion deformations of the soil in the fixed array, would ensure that they achieve satisfactory strength characteristics.

The technical problem to be solved by the invention is the need to improve the performance of the injection solution for fixing the sand-containing mass.

The technical result, to which the invention is directed, is to increase the bonding strength of the particles of the sand-containing mass with an injection solution for fixing the sand-containing mass.

An additional technical result, to which the invention is directed, is to increase the penetrating ability of the injection solution for fixing the sand-containing mass.

The essence of the invention is as follows.

An injection solution for fixing a sand-containing mass, including a binder represented by an aliphatic epoxy resin, a hardener represented by polyethylene polyamine, and a plasticizer. Unlike the prototype, the plasticizer is represented by a solution consisting of silica sol and water, taken in a volume ratio of 1:3, while the total ratio of the components is, vol:

aliphatic epoxy resin 100 polyethylenepolyamine 16 - 40 silica sol 75 water 225

The binder, represented by an aliphatic epoxy resin, ensures monolithization of the fixed sand-containing mass by filling the pore space of the mass with the introduction of a solution into it and subsequent cementation of sand particles in the mass during the hardening of the binder during its polymerization. The binder can be represented by an aliphatic epoxy resin, the dynamic viscosity of which is 7.0 cps, for example, an aliphatic epoxy resin of grade "A" (according to TU 2225-144-07510508-2015). The concentration of aliphatic epoxy resin in the solution is 100 vol.d. The presence of aliphatic epoxy resin in the composition of the solution in a minimum amount is necessary to ensure the adhesion of the solution to the surface of sand grains in the array. However, if the concentration of aliphatic epoxy resin in the composition of the solution is higher than the permissible limit, this will lead to delamination of the gel formed during the solidification of the solution in the pore space of the array.

The hardener, represented by polyethylenepolyamine (PEPA), provides an acceleration of the polymerization process of aliphatic epoxy resin. The hardener can be represented by PEPA, with characteristics corresponding to TU 2413-010-75678843-2012. The concentration of PEPA in the solution is in the range of 16 - 40 vol.d. If the concentration of PEPA is below the permissible limits, this will lead to an increase in the gelation (hardening) time of the injection solution, the formation of a gel that is unstable in air-humid conditions, and an increase in its shrinkage. If the concentration of PEPA is higher than the permissible limits, this will lead to a sharp decrease in the time of gelation (hardening) of the injection solution and limit the time of injection of the solution into the sand-containing mass, and can also lead to shrinkage and delamination of the resulting gel. Compliance with the concentration of PEPA within the upper and lower limits of the established range allows you to ensure the optimal time of gelation (hardening) of the injection solution, depending on the temperature of the solution and the ambient temperature.

The plasticizer, represented by a solution consisting of silica sol and water, taken in a volume ratio of 1:3, provides a decrease in the initial viscosity and an increase in the plasticity of the solution, which makes it possible to increase the penetrating ability of the injection solution to fix the sand-containing mass. A solution of silica sol and water, taken in a volume ratio of 1:3, also provides an increase in the bonding strength of particles of a sand-containing mass with an injection solution due to the possibility of forming a bulk silica gel. Silica sol, which is part of the plasticizer, may have the following physical and chemical characteristics: the mass fraction of silicon dioxide in silica sol may be 29-31 wt.%, the density of silica sol may be 1.19-1.21 g/cm ³ , the initial viscosity of silica sol may be 6.05 cP, and the pH of the silica sol can be 10.07 units. Silica sol, which is part of the plasticizer, can be represented, for example, by silica sol of the brand "Laxil" 30 (according to TU 2145-012-61801487-2014).

The concentration of the plasticizer in the solution is 300 vol.d., while silica sol and water, which are part of the plasticizer, are taken in a volume ratio of 1:3, and the concentration of silica sol in the solution is 75 vol.d., and the concentration of water in the solution is 225 vol. .d. The presence of water in the composition of the plasticizer in the amount of 3 parts by volume is necessary to maintain the viscosity of the plasticizer at the level at which it can perform its main function of reducing the overall initial viscosity of the solution, as well as to stabilize the volumetric shrinkage of the final gel. However, an increase in the amount of water in the plasticizer composition can lead to an increase in the gelation time of the bulk silica gel or to the impossibility of its formation at all.

The presence of a plasticizer in the composition of the solution in a minimum amount is necessary to increase the penetrating power of the injection solution. However, if the concentration of the plasticizer in the composition of the solution is higher than the permissible limit, then the gelation (hardening) time of the solution is significantly reduced, which can lead to its setting outside the array, for example, in the hose of the feeder.

The invention can be made from known materials using known means, which indicates its compliance with the criterion of patentability "industrial applicability".

The invention is characterized by a set of essential features previously unknown from the prior art, characterized in that the plasticizer is represented by a solution consisting of silica sol and water, taken in a volume ratio of 1:3, and contained in the solution at the indicated concentrations. The use as a plasticizer of a solution consisting of silica sol and water, which has the ability to form a bulk silica gel, which is a network of interconnected silica particles with a constant concentration over the volume of the gel, makes it possible to use this solution of silica sol and water to create together with a binder epoxy-silica gel substance with high adhesion to the surface of sand grains, as well as elasticity and high resistance to deformation due to the structure of the bulk silica gel. Compliance with the concentrations of silica and water within the specified limits allows you to stabilize the time of gelation (solidification) of the solution without reducing the bonding strength of the particles of the sand-containing mass with an injection solution and thus worsening the strength characteristics of the fixed arrays.

This ensures the achievement of the technical result, which consists in increasing the bonding strength of the particles of the sand-containing mass with an injection solution for fixing the sand-containing mass, thereby improving its performance.

The invention has a set of essential features previously unknown from the prior art, which indicates its compliance with the criterion of patentability "novelty".

From the prior art, injection solutions for fixing a sand-containing mass based on epoxy resins are known, in which a solvent or sodium chloride solution acts as a plasticizer. However, an injection solution for fixing a sand-containing mass based on epoxy resin is not known from the prior art, in which a solution of silica sol and water, taken in a volume ratio of 1:3, acts as a plasticizer. Also, the effect of using a solution of silica and water as a plasticizer is not known from the prior art, which consists in the possibility of increasing the bonding strength of particles of a sand-containing mass with an injection solution, due to the formation of a solution of silica and water, together with a binder, represented by an aliphatic epoxy resin, epoxy-silica gel.

In view of this, the invention meets the criterion of patentability "inventive step".

The invention is illustrated by the following tables.

Tab. 1 - Compositions of injection solutions according to the invention.

Tab. 2 - Results of testing solutions according to the invention for the time of gelation (hardening).

Tab. 3 - Results of tests of the solutions according to the invention and the gels and fixed arrays obtained by using them, for volumetric shrinkage and compressive strength.

In order to illustrate the possibility of implementation and a better understanding of the essence of the invention, an embodiment of its implementation is presented below, which can be modified or supplemented in any way, while the present invention is by no means limited to the presented embodiment.

The invention is illustrated by the following implementation example.

To obtain an injection solution, silica sol brand "Laxil" 30 (according to TU 2145-012-61801487-2014) was taken, in which the mass fraction of silicon dioxide was 29-31 wt.%, the density was 1.19-1.21 g/cm ³ , the initial viscosity was 5 cSt (6.05 cP), and the pH was equal to 10.07 pH units, combined with water in a ratio of 1:3 and mixed, thus obtaining a plasticizer. In the plasticizer, with its constant stirring, was added a binder, represented by aliphatic epoxy grade "A" (according to TU 2225-144-07510508-2015), the dynamic viscosity of which was 7.0 cP. After that, a hardener in the form of polyethylenepolyamine (PEPA) was added to the plasticizer and binder, also with constant stirring (characteristics according to TU 2413-010-75678843-2012). The resulting solution had a light brown tint. The viscosity of the resulting solution immediately after preparation was 1.1 cP and had a constant value over 90% of the duration of the induction period of gelation.

The solution was injected as follows:

An injector was introduced into the sand-containing massif, through which the resulting solution entered the massif in the impregnation mode, completely filling its pore space, without hydraulic fracturing and preserving its natural structure. The maximum solution supply pressure was 0.3 MPa. The flow rate of the solution was 13 l/min. The fixing radius varied from 0.2 to 1.0 m depending on the type of sand contained in the massif (silty sand, fine or medium size). After the injection of the solution into the sand-containing mass, the end of the gelation (hardening) of the solution was expected.

Additionally, to obtain gel samples, plastic molds were taken and filled with a solution in the same way, after which they were expected to end its gelation (hardening).

Solution 1

To obtain 414 ml of the solution, 75 ml of silica sol brand "Laxil" 30 was taken, 225 ml of water was added and 300 ml of the plasticizer was obtained. To the plasticizer was added 100 ml of a binder represented by aliphatic epoxy grade "A". Then, a hardener in the form of PEPA was added to the plasticizer and binder in the amount of 14 ml.

Solution 2

To obtain 416 ml of the solution, 75 ml of silica sol brand "Laxil" 30 was taken, 225 ml of water was added and 300 ml of the plasticizer was obtained. To the plasticizer was added 100 ml of a binder represented by aliphatic epoxy grade "A". Then, a hardener in the form of PEPA was added to the plasticizer and binder in the amount of 16 ml.

Solution 3

To obtain 420 ml of the solution, 75 ml of Leixil 30 silica sol were taken, 225 ml of water were added, and 300 ml of the plasticizer were obtained. To the plasticizer was added 100 ml of a binder represented by aliphatic epoxy grade "A". Then, a hardener in the form of PEPA was added to the plasticizer and binder in an amount of 20 ml.

Solution 4

To obtain 440 ml of the solution, 75 ml of Leixil 30 silica sol were taken, 225 ml of water were added, and 300 ml of the plasticizer were obtained. To the plasticizer was added 100 ml of a binder represented by aliphatic epoxy grade "A". Then, a hardener in the form of PEPA was added to the plasticizer and binder in the amount of 40 ml.

Solution 5

To obtain 450 ml of the solution, 75 ml of silica sol brand "Laxil" 30 was taken, 225 ml of water was added and 300 ml of the plasticizer was obtained. To the plasticizer was added 100 ml of a binder represented by aliphatic epoxy grade "A". Then, a hardener in the form of PEPA was added to the plasticizer and binder in an amount of 50 ml.

The percentages of the components of each solution are presented in Table 1.

After that, the obtained samples of fixed arrays and gel samples were tested, during which the time of gelation (solidification) of the solution, the volumetric shrinkage of the gel and the compressive strength of the gel and fixed arrays were determined.

Test 1 - determination of the time of gelation (hardening) of the solution.

The gelation time is characterized by the period after which the solution from the viscous state passes into the state of an elastic non-flowing gel. For solutions 1-5, the gelation time of the solution t _g was determined under normal conditions of ambient temperature and atmospheric pressure (T=20°C, p=760 mm Hg). Additionally, for solutions 1-3, the solution gelation time was determined at T=10°C, and for solutions 2-4, the solution gelation time was determined at T=0-1°C. The temperature of the solutions coincided with the ambient temperature. The obtained test results were entered in Table 2.

Test 2 - determination of the volumetric shrinkage of the gel.

Upon completion of the process of gelation of solutions 1-5 at T=20°C, the measurement and calculation of the initial volume of the obtained gel samples were performed. Three hours after the completion of the process of gelation of solutions 1-5, re-measurement and calculation of the final volume of gel samples were performed. Volume shrinkage ɛ _{v of} the gel was determined by the formula:

where ɛ _v is the volumetric shrinkage of the gel, %;

V _n - the initial volume of the sample, cm ³ ;

V _to - the final volume of the sample, cm ³ ;

ΔV - absolute volumetric deformation of the sample, cm ³ .

The calculation results were entered in Table 3.

Test 3 - determination of the compressive strength of the gel.

определяли по формуле:Two weeks after completion of the process of gelation of solutions 1-5 at T=20°C, gel samples were placed between the plates of the testing machine, after which each of them was gradually loaded separately. The gel sample was loaded in equal steps of 0.01 MPa, the exposure time at each step was 1 second. During the subsequent loading of the gel sample until it reached destruction, the applied load preceding the destruction F _g , kN was fixed and the loading was stopped. Gel compressive strength

determined by the formula:

- прочность на сжатие геля, МПа;where

- compressive strength of the gel, MPa;

F _g - load preceding destruction, kN;

And _g - cross-sectional area of the sample, cm ² ;

The calculation results were entered in Table 3.

Test 4 - determination of the compressive strength of the fixed arrays.

, прочности на сжатие закрепленного массива, содержащего песок мелкий

, прочности на сжатие закрепленного массива, содержащего песок средней крупности

, заносили в Таблицу 3.The determination of the compressive strength of the fixed massifs was carried out in accordance with the procedure similar to Test 3. The determination of the compressive strength of the fixed massifs was carried out separately for different types of sand contained in them (silty sand, fine or medium size). Test results in the form of calculated compressive strength values of a fixed mass containing dusty sand

, compressive strength of a fixed array containing fine sand

, compressive strength of a fixed array containing sand of medium size

were entered in Table 3.

The resulting solutions according to the invention were subjected to tests for the time of gelation (solidification) of the solution, the volumetric shrinkage of the gel, the compressive strength of the gel and the uniaxial compressive strength of the fixed arrays. The test results were listed in Tables 2 and 3 and further analyzed.

During the analysis of Trial 1, it was found that with a decrease in the amount of PEPA, acting as a hardener, the gelation time of the solution increases, which also depends on the temperature of the solution itself. At T=20°C, solutions 2-4 had satisfactory gel times, while solution 2 had the best value, lying within 1-2 hours. At T=10°C, solutions 2-3 had satisfactory gel times, and solution 4 was not tested at this temperature. At T=0-1°C solutions 2-4 had satisfactory gel time. Such results are due to the fact that in solutions 2-4, the concentrations of the components did not go beyond the upper or lower limits of the established ranges.

Solution 1 had an unsatisfactory gel time at T=20°C and T=10°C, which was significantly increased compared to the optimal one, due to the low content of PEPA in this solution, which acts as a hardener, while testing the solution at T=0-1°C were not carried out. The indicator of gelation time at T=20°C of solution 5 was significantly lower than the optimal value, which is also unsatisfactory and is due to the high content of the hardener in this solution, while testing the solution at T=10°C and T=0-1°C were not carried out.

In the course of the analysis of Tests 2-4, it was found that the gel formed from solutions 2-4 had satisfactory uniaxial compressive strength with relatively low volumetric shrinkage of its samples, while the uniaxial compressive strength of arrays fixed with these solutions also were satisfactory for all types of soils contained in them. The gel formed from solution 2 had the best indicator of uniaxial compressive strength, since its volumetric shrinkage had the lowest value compared to solutions 3-4. This also determines that the arrays fixed with solution 2 had the best uniaxial compressive strength. These results were obtained due to the fact that solutions 2-4 had optimal gelation time indicators, due to compliance with the concentrations of the components of the solutions within the established ranges.

The gel formed from solution 1 had the lowest volume shrinkage among all solutions 1-5, however, its compressive strength was significantly lower than the strength of gels formed from solutions 2-5, which did not allow the arrays fixed with solution 1 to reach satisfactory compressive strength. The arrays fixed with solution 5, as well as the gel formed from this solution, had satisfactory compressive strength, however, the value of the volumetric shrinkage of such a gel was several times higher than the same value for gels formed from solutions 1-4, which subsequently led to to delamination of the sample. The unsatisfactory performance achieved by solutions 1 and 5 is due to the concentrations of the components of these solutions exceeding the upper and lower limits of the established ranges.

All the obtained solutions 1-5 had a low fire hazard and were non-aggressive to concrete and reinforced concrete structures due to the use of a solution consisting of silica sol and water as a plasticizer, which also made it possible to reduce the risk of suffusion deformations of the soil in the fixed array due to the exclusion of components from the composition of the solution that can be leached. At the same time, solutions 2-4, in which the component concentrations did not exceed the upper or lower limits of the established ranges, had satisfactory strength characteristics.

Thus, the achievement of the technical result is achieved, which consists in increasing the bonding strength of the particles of the sand-containing mass with an injection solution for fixing the sand-containing mass, thereby improving its performance.

Table 1 Solutions Contents, vol. d. Aliphatic Epoxy PEPA Silicasol Water Solution 1 100 fourteen 75 225 Solution 2 100 16 75 225 Solution 3 100 twenty 75 225 Solution 4 100 40 75 225 Solution 5 100 fifty 75 225

Tab. 2 Solutions t _{gelobr. at T =20 ° C} , h t _{gelobr. at T =10 ° C} , h t _{gelobr. at T =0-1 ° C} , h Solution 1 3.0 18.0 - Solution 2 1.5 13.0 32.0 Solution 3 0.5 4.5 28.0 Solution 4 0.2 - 16.0 Solution 5 0.1 - -

Tab. 3 Solutions Bulk gel shrinkage ε _v , % Gel compressive strength σ _{szh g} , MPa Uniaxial compressive strength (silty sand) σ _{szh p} , MPa Uniaxial compressive strength (fine sand) σ _{compress m} , MPa Uniaxial compressive strength (medium-sized sand) σ _{szh s} , MPa Solution 1 3 0.15 1.27 1.97 0.97 Solution 2 5 0.28 1.40 2.10 1.10 Solution 3 6 0.30 1.50 2.30 1.20 Solution 4 6 0.32 1.60 2.50 1.30 Solution 5 twenty 0.34 1.62 2.52 1.32

Claims (5)

1. An injection solution for fixing a sand-containing mass, including a binder represented by an aliphatic epoxy resin, a hardener represented by polyethylene polyamine, and a plasticizer, characterized in that the plasticizer is represented by a solution consisting of silica sol and water, taken in a volume ratio of 1:3, while the total ratio of components is, ob.d .: aliphatic epoxy resin 100 polyethylenepolyamine 16-40 silica sol 75 water 225 2. An injection solution according to claim 1, characterized in that the dynamic viscosity of the aliphatic epoxy resin is 7.0 centipoise. 3. An injection solution according to claim 1, characterized in that the mass fraction of silicon dioxide in silica sol is 29-31 wt.%. 4. An injection solution according to claim 1, characterized in that the density of the silica sol is 1.19-1.21 g/cm ³ , the initial viscosity of the silica sol is 6.05 cP, and the pH of the silica sol is 10.07 units.