Method for determining splitting grouting diffusion distance considering coupling of grout and viscosity time variation

Abstract

The application discloses a method for determining the diffusion distance of splitting grouting by considering the coupling of grout and soil and viscosity time variation, belongs to the field of ballastless track subgrade engineering, and aims to solve the problem of large calculation deviation of the diffusion distance caused by the fact that the existing method does not fully consider the grout-soil coupling effect, the nonlinear non-Newtonian fluid characteristics of grout and the viscosity time variation characteristics. The method first proposes four model assumptions, determines the splitting pressure and splitting channel expansion pressure based on the elasticity mechanics and fracture mechanics, and establishes a grout pressure gradient calculation formula; then analyzes the influencing factors of the diffusion radius, assumes the relationship between the splitting channel width and the pressure to establish a diffusion distance model under the grout-soil coupling effect, introduces the viscosity time variation parameter to establish a diffusion distance and time model, and forms a calculation process integrating the grouting pressure, time, viscosity and grouting amount per second. The application realizes the accurate calculation of the diffusion distance of splitting grouting, and provides an effective basis for the design of grouting parameters for the repair of the grouting and mud of the ballastless track subgrade.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ballastless track subgrade engineering, and particularly relates to a method for determining the diffusion distance of split grouting considering the coupling of slurry and soil and the time-varying viscosity. BACKGROUND

[0002] Slurry and mud spewing is one of the common diseases of ballastless track subgrade, and at the present stage, it is mainly repaired by grouting. This method has been widely used in tunnel treatment, foundation reinforcement and other engineering. In order to ensure the effect of grouting reinforcement, a reasonable grouting interval should be selected, which relies on correct grouting theory guidance. According to the state of soil and the degree of slurry and mud spewing, the diffusion mode of slurry in soil can be roughly divided into penetration and splitting. In the coarse-grained soil with developed pore, penetration grouting is generally dominant, and in the dense or fine-grained soil with good gradation, splitting grouting is generally dominant. At the present stage, the research on penetration grouting is relatively sufficient, but the diffusion behavior of splitting grouting still needs to be studied. Figure 1 Splitting grouting is the process of splitting soil by slurry and continuing to expand forward. The principle is that after the soil is hydraulically split by applying grouting pressure, the slurry pushes the crack to open rapidly to form a grouting crack. With the gradual injection of slurry, a network of slurry veins is formed in the soil, and the soil is squeezed, thereby improving the strength and stiffness of the soil. There are the following difficulties in determining the diffusion distance of slurry in the research: (1) The soil deforms outward under the action of grouting pressure, resulting in changes in the width of the splitting channel along the slurry vein, which in turn affects the distribution of slurry pressure, that is, there is a significant slurry-soil coupling effect in the process of slurry diffusion. (2) The slurry is generally a nonlinear non-Newtonian fluid in actual grouting, and the calculation results are prone to deviation. (3) The viscosity changes with time during the splitting grouting diffusion process, and it cannot diffuse outward indefinitely.

[0003] In summary, the existing splitting grouting theory cannot effectively solve the above problems, and it is difficult to accurately determine the diffusion distance of slurry in the splitting grouting of ballastless track subgrade, which restricts the precise application of grouting repair technology in the treatment of slurry and mud spewing disease of ballastless track subgrade. Therefore, it is urgent to propose a method for determining the diffusion distance of splitting grouting which can comprehensively consider the slurry-soil coupling effect, the nonlinear fluid characteristics of slurry and the time-varying viscosity. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application aims to provide a method for determining the diffusion distance of splitting grouting considering the coupling of slurry and soil and the time-varying viscosity. By establishing a splitting grouting diffusion theoretical model considering multiple factors, the accurate calculation of the diffusion distance of slurry is realized, which provides a scientific basis for the design of grouting parameters in the repair of slurry and mud spewing disease of ballastless track subgrade, and finally ensures the effect of grouting reinforcement and improves the service reliability of ballastless track subgrade.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] A method for determining the diffusion distance of split grouting considering the coupling of grout and soil and the time-varying viscosity, comprising the following steps:

[0007] S1, proposing a basic assumption of grout diffusion in split grouting, determining the split grouting pressure, and proposing a basic law of grout diffusion in split grouting, the specific process being as follows:

[0008] S11: proposing a model assumption: ① the grout is incompressible, uniform in mass, isotropic, and the flow pattern is always unchanged during grouting; ② the grout is a power-law fluid, the flow is laminar, the flow velocity of the upper and lower side walls of the split channel is 0, and the no-slip boundary condition is met; ③ the mass of the grout is conserved during the splitting process, and the loss of the grout diffused to the outside of the split channel is not considered; ④ assuming that the stress distribution of the stratum is uniform, and the influence of gravity on the grouting process is ignored;

[0009] S12: determining the split grouting pressure: determining the split grouting pressure and the split channel expansion pressure according to the theory of elasticity and the crack propagation theory of fracture mechanics;

[0010] S13: proposing a basic law of grout diffusion in split grouting: according to the model assumption, a calculation formula for the pressure gradient of the grout in the diffusion channel is established;

[0011] S2, based on the basic law of grout diffusion in split grouting, analyzing the influencing factors of split grouting diffusion radius, deducing the expression of split grouting diffusion radius, and establishing a perfect calculation program, the specific process being as follows:

[0012] S21: analysis of influencing factors: considering the analysis of the nonlinear characteristics of soil and the spatial distribution characteristics of grout, the influencing factors of split grouting diffusion radius are determined;

[0013] S22: derivation of split grouting diffusion distance: assuming the relationship between the width of the split channel and the pressure, a calculation model of the theoretical solution of split grouting considering the coupling effect of grout-soil based on known parameters is established;

[0014] S23: grout diffusion distance considering the viscosity effect of grouting material: considering the change of grout viscosity with time, a calculation model of grout diffusion distance and time is established.

[0015] Further, in the step S1, the pressure gradient calculation expression of the grout in the diffusion channel is:

[0016] ;

[0017] In the formula: is the grout pressure, is the distance from a point to the grouting hole, is the consistency coefficient, is the grouting amount per second, wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0018] Further, the grouting amount per second in the step S1 is calculated by the following equation: wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0019] ;

[0020] wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0021] Further, the splitting pressure in the step S1 is calculated by the following equation: wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0022] ;

[0023] ;

[0024] wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0025] Further, the grouting amount per second in the step S1 is calculated by the following equation:

[0026] ;

[0027] wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0028] Further, the grouting amount per second in the step S1 is calculated by the following equation:

[0029] ;

[0030] Further, the grouting amount per second in the step S1 is calculated by the following equation: wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0031] ;

[0032] wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length. wherein, σt is the tensile strength of soil, σ1 is the maximum principal stress, σ3 is the minimum principal stress, KIC is the critical fracture toughness, and L is the fracture propagation length.

[0033] Further, the step S2, the slurry diffusion distance and time calculation model expression is:

[0034] ;

[0035] In the formula: is the grouting time, is the viscosity of the grouting material, .

[0036] Further, the step S2 also includes establishing an overall calculation process based on the grouting pressure , grouting time , slurry viscosity , grouting amount per second .

[0037] Compared with the prior art, the application has the following innovative advantages:

[0038] (1) The method regards the grouting material as a power-law fluid, combines the nonlinear characteristics of soil stress deformation, considers the slurry-rock coupling effect and the time-varying characteristics of the grouting material, and theoretically derives the analytical solution of the splitting grouting diffusion distance.

[0039] (2) The method combines the polyurethane material parameters and the pressure and flow rate used in the mud grouting repair of the ballastless track roadbed, and determines the theoretical radius solution of the grouting diffusion.

[0040] (3) The method finds that the slurry-rock coupling effect and the time-varying characteristics of the grouting material have a very important influence on the grouting diffusion radius, and neglecting the slurry-rock coupling effect will underestimate the splitting grouting diffusion radius, and neglecting the time-varying characteristics of the grouting material will significantly overestimate the diffusion radius. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a schematic diagram of the grouting process of fractured rock mass;

[0042] Figure 2 is a schematic diagram of the elastic mechanics mechanism analysis of the splitting grouting splitting pressure in the embodiment of the application;

[0043] Figure 3 is a schematic diagram of the stress analysis of the slurry flow unit in the crack in the embodiment of the application;

[0044] Figure 4 is a schematic diagram of the splitting channel width spatial decay curve at different times in the embodiment of the application;

[0045] Figure 5 is a schematic diagram of the slurry pressure difference spatial decay curve at different times in the embodiment of the application. DETAILED DESCRIPTION

[0046] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings, but the scope of protection of the present application is not limited by the specific embodiments.

[0047] The present application is described in detail with a certain polyurethane grouting test as an example.

[0048] Step S1, the properties of soil and slurry are changed by adjusting test parameters in the model test to meet the method assumptions. The initiation pressure and the pressure of the splitting channel expansion are obtained by the theory of elasticity (such as Figure 2 ) and the theory of fracture mechanics:

[0049] ;

[0050] ;

[0051] The mechanical analysis of the slurry flow in the crack during the splitting grouting is carried out to obtain the corresponding stress condition of the slurry flow in the crack (such as Figure 3 ), and the pressure gradient calculation expression of the splitting grouting slurry on the diffusion channel is derived accordingly:

[0052] ;

[0053] In step S2, the relationship between the splitting channel width and the pressure is assumed to be , and the relationship between the crack width and the diffusion distance can be obtained according to the pressure gradient of the splitting grouting slurry on the diffusion channel and the relationship between the splitting channel width and the pressure:

[0054] ;

[0055] Without considering the compressibility of the slurry and the permeability of the soil, the relationship between the slurry diffusion distance and the grouting time can be obtained according to the law of conservation of mass:

[0056] ;

[0057] In the formula:

[0058] ;

[0059] ;

[0060] The above formula includes the grouting amount per second , the non-linear elastic parameter , and the parameter , which are shown in Table 1, and the slurry viscosity .

[0061] Table 1

[0062] ;

[0063] According to the data in the table, the spatial decay curves of the width of the split channel at different times (such as Figure 4 ) and the spatial decay curves of the pressure difference of the slurry (such as Figure 5 ) are obtained.

[0064] The above examples have described the technical solutions of the present application in detail. Apparently, the present application is not limited to the described examples. Based on the examples in the present application, those skilled in the art can make various changes, but any change equivalent or similar to the present application falls within the protection scope of the present application.

[0065] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

[0066] Finally, it should be noted that: the above only describes the preferred examples of the present application, and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity, characterized in that, Includes the following steps: S1. The basic assumptions regarding the diffusion of grout in fracturing grouting are proposed, the fracturing grouting pressure is determined, and the basic laws governing grout fracturing diffusion are proposed. The specific process is as follows: S11: Model assumptions are proposed: ① The grout is incompressible, homogeneous, isotropic, and its flow pattern remains unchanged throughout the grouting process; ② The grout is a power-law fluid with laminar flow, and the flow velocity on the upper and lower sidewalls of the splitting channel is 0, satisfying the no-slip boundary condition; ③ The mass of the grout is conserved during the splitting process, and the loss of grout that diffuses outside the splitting channel is not considered; ④ It is assumed that the formation stress distribution is uniform, and the influence of gravity on the grouting process is ignored. S12: Determine the splitting grouting pressure: Determine the splitting grouting initiation pressure and the splitting channel expansion pressure based on the theory of elasticity and fracture mechanics crack propagation theory; S13: Propose the basic law of grout splitting and diffusion: Based on the model assumptions, establish the calculation formula for the pressure gradient of splitting grout in the diffusion channel; S2. Based on the fundamental laws of grout splitting and diffusion, the influencing factors of the splitting grout diffusion radius are analyzed, the expression for the splitting grout diffusion radius is derived, and a complete calculation program is established. The specific process is as follows: S21: Influencing Factor Analysis: Considering the nonlinear characteristics of the soil and the spatial distribution characteristics of the grout, determine the influencing factors of the splitting grout diffusion radius; S22: Derivation of split grouting diffusion distance: Assuming the relationship between the split channel width and pressure, a theoretical solution calculation model for split grouting considering the grout-soil coupling effect is established based on known parameters; S23: Grout diffusion distance considering the viscosity effect of grouting material: Considering the change of grout viscosity with time, a calculation model of grout diffusion distance versus time is established; In step S2, the calculation expression for the splitting grouting diffusion distance is: ; In the formula: This is the limit radius for split grouting. Where is the radius of the grouting hole. For nonlinear elastic parameters, This is the consistency coefficient. The grouting rate per second. These are the mechanical property constants related to the soil-grout coupling effect. For the nonlinear elastic parameters of the soil, For grouting pressure, To expand the pressure in the splitting channel.

2. The method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity as described in claim 1, characterized in that, In step S1, the expression for calculating the pressure gradient of the fracturing grout in the diffusion channel is: ; In the formula: For slurry pressure, The distance from a point to the grouting hole. This represents the width of the split crack.

3. The method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity as described in claim 2, characterized in that, The grouting rate per second The relationship between the pressure gradient and the pressure gradient is expressed as follows: ; In the formula, The average flow velocity of the slurry within the sand layer.

4. The method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity as described in claim 3, characterized in that, In step S1, the splitting pressure With split channel expansion pressure The calculation expression is: ; ; In the formula: For the tensile strength of soil, For major principal stresses, For minor principal stress, The critical strength factor for splitting crack propagation. This represents the splitting extension length.

5. The method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity as described in claim 4, characterized in that, The assumed relationship between the splitting channel width and pressure in step S2 is as follows: 。 6. The method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity as described in claim 5, characterized in that, Crack width and slurry diffusion distance The relationship is: ; In the formula: For relevant parameters, take boundary conditions. hour, hour, .

7. The method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity as described in claim 6, characterized in that, In step S2, the calculation model expression for the slurry diffusion distance versus time is as follows: ; In the formula: For grouting time, The viscosity of the grouting material, .

8. The method for determining the diffusion distance of splitting grouting considering grout-soil coupling and time-varying viscosity as described in claim 1, characterized in that, Step S2 also includes establishing a system based on grouting pressure. Grouting time Slurry viscosity Grouting rate per second The overall calculation process is used to optimize the grouting spacing for split grouting of ballastless track subgrade.

Images