Construction method of correlation model between erosion distance of super-deep jet flow in soft foundation and overburden pressure

Abstract

The present invention relates to the technical field of soft soil foundation treatment, and provides a method for constructing a correlation model between the erosion distance of ultra-deep rotary jet in soft foundation and the overburden pressure, including taking in-situ soil samples; processing the retrieved in-situ soil samples to obtain the experimental values and simulation values of the effective cohesion, internal friction angle, and initial elastic modulus of the obtained soil samples; obtaining the optimal mesoscopic parameters according to the relationship between the error value of the simulation value and the experimental value of the soil body and the error requirement value; establishing a plane particle model and a fluid grid model based on the similarity ratio; plotting a scatter diagram of the data points of the ultimate erosion distance of the ultra-deep rotary jet varying with the overburden pressure; fitting the relationship between the ultimate erosion distance of the ultra-deep rotary jet and the overburden pressure by using an inverse proportional function, and substituting the obtained values of the model constants α and β into the inverse proportional function to obtain a quantitative correlation mathematical model characterizing the relationship between the erosion distance of the ultra-deep rotary jet in soft soil foundation and the overburden pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of soft soil foundation treatment, and particularly relates to a method for constructing a correlation model between the erosion distance of ultra-deep jet grouting in soft foundation and the overburden pressure. Background Technique

[0002] The high-pressure jet grouting technology is an effective and widely used method for treating soft foundations, with many advantages such as simple construction operation, low cost, multiple construction methods, and good durability of the jet grouting solidified body. However, due to the poor engineering properties of soft soil, such as high water content, large void ratio, high compressibility, low strength, and poor consolidation degree, it is extremely easy to have an adverse impact on the safety and stability of engineering construction in soft foundations, and then induce engineering disaster accidents such as foundation pit collapse, foundation instability, excessive differential settlement of embankments, building cracking or overturning. At present, the reasonable prediction of the shape of high-pressure jet grouted piles in soft foundations involved in this technology is a major difficulty. In engineering practice, due to the lack of effective methods, the prediction of the shape of high-pressure jet grouted piles in soft foundations heavily relies on similar engineering experience, which is likely to cause a large deviation between the prediction result and the true value, with high uncertainty. This not only increases the risk of instability failure and excessive deformation of the reinforcement project, but also increases the project cost. In the construction of soft foundation projects such as coastal and lakeside areas, when using high-pressure jet grouting technology for foundation treatment, in order to meet the requirements of foundation bearing capacity, it is necessary to construct extra-long high-pressure jet grouted piles. For extra-long high-pressure jet grouted piles, their pile body shape is significantly affected by the overburden pressure of the formation. Especially for the middle and lower sections of extra-long high-pressure jet grouted piles, their pile body shape is mainly controlled by the overburden pressure of the formation. On the other hand, since the pile body shape of extra-long high-pressure jet grouted piles is directly related to the erosion distance of high-pressure jet grouting.

[0003] Therefore, in order to reasonably predict the pile body shape of extra-long high-pressure jet grouted piles in deep soft foundations, it is necessary to establish a correlation mathematical model between the erosion distance of jet grouting and the overburden pressure, which has important theoretical and practical significance for improving the current problems of difficult prediction, low accuracy, and high uncertainty of the shape of high-pressure jet grouted piles. Summary of the Invention

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a method for constructing a correlation model between the erosion distance of ultra-deep jet grouting in soft foundation and the overburden pressure, and the construction method includes:

[0006] (1) Taking in-situ soil samples from the site of a deep soft foundation project to be reinforced by ultra-deep high-pressure jet grouting, and the sampling depth is about half of the high-pressure jet grouting reinforcement depth;

[0007] (2) Perform unconsolidated undrained triaxial compression tests on the retrieved in-situ soil samples under three different confining pressures to obtain the experimental values of the effective cohesion and internal friction angle of the soil samples, and calculate the experimental value of the initial elastic modulus of the soil samples according to the deviator stress-strain curve;

[0008] (3) Based on the results of the unconsolidated undrained triaxial compression tests and referring to existing experience, set the initial mesoscopic parameters required for particle flow analysis;

[0009] (4) Use the particle flow method to carry out biaxial compression numerical tests under three different lateral constraint stresses, conduct data processing, and obtain the simulated values of the initial elastic modulus, effective cohesion and internal friction angle of the soil mass;

[0010] (5) Obtain the optimal mesoscopic parameters according to the relationship between the error values of the simulated values and experimental values of the initial elastic modulus, cohesion and internal friction angle of the soil mass and the required error values;

[0011] (6) Based on the similarity ratio and fully considering the balance between the model calculation efficiency and the calculation result accuracy, determine the size of the plane particle model used to simulate the foundation soil, and establish the plane particle model;

[0012] (7) Generate a row of particles closely connected by parallel bonding keys on the top surface of the plane particle model as the simulation medium for overburden pressure;

[0013] (8) Establish a fluid grid model that can submerge the plane particle model;

[0014] (9) Based on the optimal mesoscopic parameters and the overburden pressure simulation medium, carry out the numerical simulation of the fluid-solid coupling of the super-deep jet erosion of soft soil particles under different overburden pressures, and obtain the ultimate erosion distance of the super-deep jet in the soft soil foundation under different overburden pressures;

[0015] (10) Plot a scatter diagram of the data points of the ultimate erosion distance of the super-deep jet varying with the overburden pressure;

[0016] (11) Fit the relationship between the ultimate erosion distance of the super-deep jet and the overburden pressure using an inverse proportional function to obtain the values of the model constants α and β;

[0017] (12) Substitute the obtained values of the model constants α and β into the inverse proportional function to obtain a quantitative correlation mathematical model characterizing the relationship between the erosion distance of the super-deep jet in the soft soil foundation and the overburden pressure.

[0018] Further, in step (2), the three different confining pressures are 100 kPa, 200 kPa, and 300 kPa.

[0019] Furthermore, in step (3), the initial mesoscopic parameters include the normal contact stiffness, tangential contact stiffness, friction coefficient, tensile strength, and cohesion.

[0020] Furthermore, in step (5), the judgment criterion is as follows: if the error value is less than or equal to the error requirement value, the set initial mesoscopic parameters are the optimal mesoscopic parameters;

[0021] Conversely, go to step (4) to adjust the initial mesoscopic parameters. Among them, the error requirement value can be determined according to the engineering accuracy requirements, and generally 5% can be taken.

[0022] Furthermore, in step (8), the size of the fluid meshes in the fluid mesh model is larger than the particle size in the planar particle model.

[0023] Furthermore, in step (11), the inverse proportional function is:

[0024]

[0025] In the formula: X m is the ultimate erosion distance of the ultra-deep rotary jet (cm);

[0026] p 0 is the reference pressure value (the value is 1 kPa);

[0027] σ v is the overburden pressure (kPa);

[0028] α and β are model constants.

[0029] The present invention has the following beneficial effects:

[0030] (1) The present invention makes full use of the advantages of high efficiency and low cost of computer simulation technology, overcomes the disadvantages of low efficiency, high cost, and difficult boundary condition control in constructing the correlation model between the rotary jet erosion distance and the overburden pressure by using the scaled physical model test, can greatly improve the modeling efficiency and prediction accuracy, and has significant economic benefits;

[0031] (2) The present invention considers the fluid-solid coupling effect in the process of high-pressure rotary jet breaking soil in deep soft foundation, has a high degree of reduction to the actual working conditions of high-pressure rotary jet, can be used to quickly estimate the variation law of the pile-forming shape of ultra-deep high-pressure rotary jet in deep soft foundation with the value of overburden pressure, and lays a solid theoretical model foundation for regulating and optimizing the construction process parameters of high-pressure rotary jet in deep soft foundation. Description of the Drawings

[0032] Figure 1 is the flow chart of the model construction method of the present invention;

[0033] Figure 2 is the schematic diagram of the uniaxial compression numerical test;

[0034] Figure 3 Schematic diagram of the simulation medium for overburden pressure

[0035] Figure 4 Schematic diagram of the relative sizes of fluid meshes and particles in the planar particle model

[0036] Figure 5 Schematic diagram of non - linear fitting based on the inverse proportional function

[0037] Figure 6 Planar particle model generated in the embodiment

[0038] Figure 7 Fluid mesh model generated in the embodiment

[0039] Figure 8 Simulation diagram of the erosion distance of the ultra - deep jet grouting in soft soil foundation when the overburden pressure is 30 kPa in the embodiment

[0040] Figure 9 Scatter plot of data points of the ultimate erosion distance of the ultra - deep jet grouting varying with the overburden pressure in the embodiment

[0041] Figure 10 Fitting result diagram based on the inverse proportional function in the embodiment

[0042] In the figure: planar particle model 1, particles 2 closely connected by parallel connection keys, fluid mesh 3, particles 4 in the planar particle model, different overburden pressures 5, ultimate erosion distances 6 corresponding to different overburden pressures, data points 7 of the ultimate erosion distance varying with the overburden pressure, inverse proportional function 8 Detailed implementation manners

[0043] The following describes the detailed implementation manners of the present invention in conjunction with the accompanying drawings. It should be noted that the embodiments are only specific elaborations of the invention and should not be regarded as limitations of the invention. The purpose of the embodiments is to enable those skilled in the art to better understand and reproduce the technical solutions of the present invention. The protection scope of the present invention should still be subject to the scope defined by the claims

[0044] As Figure 1 shown, the present invention provides a method for constructing a correlation model between the erosion distance of ultra - deep jet grouting in soft foundation and the overburden pressure. The construction method includes:

[0045] S1, taking in - situ soil samples from the site of a deep soft foundation project where ultra - deep high - pressure jet grouting reinforcement is to be carried out, and the sampling depth is about half of the high - pressure jet grouting reinforcement depth

[0046] S2. Conduct unconsolidated undrained triaxial compression tests on the retrieved in-situ soil samples under three different confining pressures to obtain the test values of the effective cohesion and internal friction angle of the soil samples, and calculate the test values of the initial elastic modulus of the soil samples according to the deviator stress-strain curve. The three different confining pressures are 100 kPa, 200 kPa, and 300 kPa. The test process and methods can be carried out in accordance with the corresponding provisions of standards and specifications such as "Standard for Geotechnical Test Methods" (GB / T 50123-2019) and "Code for Highway Geotechnical Tests" (JTG 3430-2020).

[0047] S3. Based on the results of the unconsolidated undrained triaxial compression tests and referring to existing experience, set the initial mesoscopic parameters required for particle flow analysis. The initial mesoscopic parameters include the normal contact stiffness, tangential contact stiffness, friction coefficient, tensile strength, and cohesion.

[0048] S4. Use the particle flow method to carry out biaxial compression numerical tests under three different lateral constraint stresses (as shown in Figure 2 ), conduct data processing, and obtain the simulated values of the initial elastic modulus, effective cohesion, and internal friction angle of the soil mass. The three different lateral constraint stresses include lateral and upper and lower constraint stresses.

[0049] S5. Obtain the optimal mesoscopic parameters according to the relationship between the error values of the simulated values and test values of the initial elastic modulus, cohesion, and internal friction angle of the soil mass and the error requirement values. If the error value is less than or equal to the error requirement value, the set initial mesoscopic parameters are the optimal mesoscopic parameters; otherwise, go to step (4) to adjust the initial mesoscopic parameters. Among them, the error requirement value can be determined according to the engineering accuracy requirements, and generally 5% can be taken.

[0050] S6. Based on the similarity ratio and fully considering the balance between the model calculation efficiency and the calculation result accuracy, determine the size of the plane particle model 1 for simulating the foundation soil, and establish the plane particle model 1.

[0051] S7. Generate a row of particles 2 tightly connected by parallel bonds on the top surface of the plane particle model 1 as the overburden pressure simulation medium (as shown in Figure 3 ).

[0052] S8. Establish a fluid grid model that can submerge the plane particle model 1. The size of the fluid grid 3 in the fluid grid model is larger than the size of the particles 4 in the plane particle model (as shown in Figure 4 ).

[0053] S9. Based on the optimal mesoscopic parameters and the overburden pressure simulation medium, carry out the numerical simulation of the fluid-solid coupling of the super-deep jet erosion of soft soil particles under different overburden pressures 5, and obtain the ultimate erosion distance 6 of the super-deep jet in the soft soil foundation under different overburden pressures (as shown in Figure 5as shown); different values of the overburden pressure 5 are taken in the form of graded increments, and the value range is 10 - 300 kPa, and the graded increment can be taken as 30 - 50 kPa;

[0054] S10, plot a scatter diagram of the data points of the ultimate erosion distance of the ultra - deep rotary jet varying with the overburden pressure; where the overburden pressure 5 is the abscissa and the ultimate erosion distance 6 of the ultra - deep rotary jet is the ordinate;

[0055] S11, fit the relationship between the ultimate erosion distance of the ultra - deep rotary jet and the overburden pressure using an inverse proportional function to obtain the values of the model constants α and β;

[0056] The inverse proportional function is:

[0057]

[0058] In the formula: X m is the ultimate erosion distance of the ultra - deep rotary jet (cm);

[0059] p 0 is the reference pressure value (the value is taken as 1 kPa);

[0060] σ v is the overburden pressure (kPa);

[0061] α and β are model constants.

[0062] S12, substitute the obtained values of the model constants α and β into the inverse proportional function to obtain a quantitative correlation mathematical model characterizing the relationship between the erosion distance of the ultra - deep rotary jet in soft soil foundation and the overburden pressure.

[0063] Example

[0064] In this example, a model is constructed for a coastal soft soil foundation under the conditions of a high - pressure rotary jet grouting reinforcement depth of 30 m and a high - pressure rotary jet pressure of 2 MPa. The construction steps are as follows:

[0065] The first step is to take in - situ soil from the site of a large vehicle yard project in a coastal soft soil area of a certain field. The depth of soil sampling is taken as half of the high - pressure rotary jet grouting reinforcement depth, that is, 15 m;

[0066] The second step is to carry out unconsolidated undrained triaxial compression tests on the retrieved in - situ soil samples under three different confining pressures of 100 kPa, 200 kPa, and 300 kPa according to standards and specifications such as "Standard for Geotechnical Test Methods" (GB / T 50123 - 2019) and "Highway Geotechnical Test Procedures" (JTG 3430 - 2020). The effective cohesion of the soil samples is obtained as 11.3 kPa, the internal friction angle is 1.4°, and the initial elastic modulus of the soil samples is calculated as 3.2 MPa according to the deviator stress - strain curve;

[0067] In the third step, based on the results of the unconsolidated undrained triaxial compression test and referring to existing experience, the initial mesoscopic parameters required for the particle flow analysis are set: the normal contact stiffness is 1.2×10 8 N / m, the tangential contact stiffness is 1.5×10 8 N / m, the friction coefficient is 0.1, the tensile strength is 1.6×10 5 Pa, and the cohesion is 1.6×10 5 Pa;

[0068] In the fourth step, the particle flow method is used to carry out biaxial compression numerical tests under lateral confinement stresses of 100 kPa, 200 kPa, and 300 kPa, and data processing is performed to obtain the simulated values of the initial elastic modulus, cohesion, and internal friction angle of the soil mass, which are 3.3 MPa, 14.5 kPa, and 1.9°, respectively;

[0069] In the fifth step, it is calculated that the errors between the simulated values of the initial elastic modulus, cohesion, and internal friction angle of the soil mass and the test values of the initial elastic modulus, cohesion, and internal friction angle of the soil mass obtained from the unconsolidated undrained triaxial compression test are all less than the error requirement value of 5%. That is, the set initial mesoscopic parameters are the optimal mesoscopic parameters, and the sixth step is continued;

[0070] In the sixth step, based on the similarity ratio and fully considering the balance between the model calculation efficiency and the calculation result accuracy, the size of the plane particle model used to simulate the foundation soil is determined to be 80 cm in the horizontal direction and 60 cm in the vertical direction, and plane particle model 1 is established, as Figure 6 shown;

[0071] In the seventh step, a row of particles tightly connected by parallel bonds is generated on the top surface of the plane particle model as the simulation medium for the overlying soil pressure;

[0072] In the eighth step, a fluid grid model capable of submerging the plane particle model is established, as Figure 7 shown;

[0073] In the ninth step, based on the optimal mesoscopic parameters and the simulation medium for the overlying soil pressure, the fluid-solid coupling numerical simulation of the ultra-deep jet erosion of soft soil particles is carried out under overlying soil pressures of 30 kPa, 60 kPa, 90 kPa, 120 kPa, and 150 kPa. The ultimate erosion distances of the ultra-deep jet in the soft soil foundation under overlying soil pressures of 30 kPa, 60 kPa, 90 kPa, 120 kPa, and 150 kPa are obtained as 17.2 cm, 11.8 cm, 10.5 cm, 9.9 cm, and 9.1 cm, respectively. Figure 8 It is the simulation diagram of the erosion distance of the ultra-deep jet in the soft soil foundation when the overlying soil pressure is 30 kPa. The jet cutting cavity shape is within the circle in the figure.

[0074] Step 10: In the drawing software, plot a scatter diagram of the data points of the ultimate erosion distance of the ultra-deep jet grouting flow varying with the overburden pressure, with the overburden pressures of 0 kPa, 60 kPa, 90 kPa, 120 kPa, and 150 kPa as the abscissa and the ultimate erosion distances of the ultra-deep jet grouting flow of 17.2 cm, 11.8 cm, 10.5 cm, 9.9 cm, and 9.1 cm as the ordinate, as shown in Figure 9 shown;

[0075] Step 11: Using the non-linear fitting function of the drawing software, fit the relationship between the ultimate erosion distance of the ultra-deep jet grouting flow and the overburden pressure with an inverse proportional function (Formula ①) ( Figure 10 ), and obtain the values of the model constants α and β as 297.9 and 7.2 respectively;

[0076] Step 12: Substitute the obtained values of the model constants α and β into the inverse proportional function (Formula ①), and the mathematical expression of the correlation model between the erosion distance of the ultra-deep jet grouting flow in the coastal soft soil foundation and the overburden pressure under the condition that the high-pressure jet grouting pressure is 2 MPa is as shown in Formula ②.

[0077]

[0078] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0079] It should be noted that the technical features not described in detail in the present invention can all be implemented by any existing technology.

Claims

1. A method for constructing a correlation model between the erosion distance of ultra-deep rotary jets on soft foundation and the overlying soil pressure, characterized in that: The build methods include: (1) Take in-situ soil samples from the deep and soft foundation project site where ultra-deep high-pressure jet grouting reinforcement is to be carried out. The sampling depth is about half of the high-pressure jet grouting reinforcement depth; (2) The retrieved in-situ soil samples were subjected to unconsolidated and undrained triaxial compression tests under three different confining pressures to obtain the test values ​​of the effective cohesion and internal friction angle of the soil samples, and the test value of the initial elastic modulus of the soil samples was calculated based on the deviatoric stress-strain curve; (3) Based on the unconsolidated undrained triaxial compression test results and reference to existing experience, the initial mesoscopic parameters required for particle flow analysis are set; (4) The particle flow method was used to carry out biaxial compression numerical tests under three different lateral constraint stresses, and data processing was performed to obtain the simulated values ​​of the initial elastic modulus, effective cohesion and internal friction angle of the soil; (5) The optimal micro-parameters are obtained by judging the relationship between the error between the simulation value and the test value of the initial elastic modulus, cohesion and internal friction angle of the soil and the error requirement value; (6) Based on the similarity ratio and taking into full consideration the balance between the model calculation efficiency and the accuracy of the calculation results, determine the size of the plane particle model used to simulate the foundation soil and establish the plane particle model; (7) Generate a row of particles closely connected by parallel connecting bonds on the top surface of the plane particle model as the overlying soil pressure simulation medium; (8) Establish a fluid grid model that can submerge the plane particle model; (9) Based on the optimal mesoscopic parameters and the overburden pressure simulation medium, the fluid-solid coupling numerical simulation of the erosion of soft soil particles by the rotary jet under different overburden pressures was carried out to obtain the limit erosion distance of the ultra-deep rotary jet under different overburden pressures on the soft soil foundation; (10) Draw a scatter plot of the data points showing the extreme erosion distance of the ultra-deep jet flow versus the overburden pressure; (11) The inverse proportional function is used to fit the relationship between the extreme erosion distance of the ultra-deep rotating jet and the overlying soil pressure to obtain the model constant α , β The value of (12) The obtained model constants α , β The value of is substituted into the inverse proportional function, and a quantitative correlation mathematical model is obtained to characterize the relationship between the erosion distance of ultra-deep rotating jets on soft soil foundation and the overlying soil pressure.

2. The method for constructing a correlation model between the erosion distance of ultra-deep rotary jets on soft foundation and overlying soil pressure according to claim 1, characterized in that: In step (2), the three different confining pressures are 100 kPa, 200 kPa, and 300 kPa.

3. The method for constructing a correlation model between the erosion distance of ultra-deep rotary jets on soft foundation and overlying soil pressure according to claim 1, characterized in that: In step (3), the initial microscopic parameters include contact normal stiffness, contact tangential stiffness, friction coefficient, tensile strength and cohesion.

4. The method for constructing a correlation model between the erosion distance of ultra-deep rotary jets on soft foundation and overlying soil pressure according to claim 1, characterized in that: In step (5), the judgment criterion is: if the error value is less than or equal to the error requirement value, the set initial mesoscopic parameters are the optimal mesoscopic parameters; Otherwise, go to step (4) to adjust the initial microscopic parameters.

5. The method for constructing a correlation model between the erosion distance of ultra-deep rotary jets on soft foundation and overlying soil pressure according to claim 1, characterized in that: In step (8), the size of the fluid grid in the fluid grid model is larger than the particle size in the planar particle model.

6. The method for constructing a correlation model between the erosion distance of ultra-deep rotary jets on soft foundation and overlying soil pressure according to claim 1, characterized in that: In step (11), the inverse proportional function is: ① Where: X m is the extreme erosion distance of ultra-deep rotating jet, in cm; p 0 is the reference pressure value, which is 1kPa; σ v is the overlying soil pressure, in kPa; α , β is the model constant.

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