CN116698624A - Test method and system for improving internal friction angle and cohesive force of soil by foam - Google Patents
Test method and system for improving internal friction angle and cohesive force of soil by foam Download PDFInfo
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- 239000006260 foam Substances 0.000 title claims abstract description 111
- 239000002689 soil Substances 0.000 title claims abstract description 102
- 238000010998 test method Methods 0.000 title description 5
- 239000002245 particle Substances 0.000 claims abstract description 64
- 239000007788 liquid Substances 0.000 claims abstract description 63
- 238000012360 testing method Methods 0.000 claims abstract description 56
- 238000005187 foaming Methods 0.000 claims abstract description 39
- 238000002347 injection Methods 0.000 claims abstract description 33
- 239000007924 injection Substances 0.000 claims abstract description 33
- 238000004088 simulation Methods 0.000 claims abstract description 30
- 230000008859 change Effects 0.000 claims abstract description 18
- 230000006872 improvement Effects 0.000 claims abstract description 14
- 238000002474 experimental method Methods 0.000 claims abstract description 12
- 239000004088 foaming agent Substances 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims description 19
- 230000003993 interaction Effects 0.000 claims description 14
- 238000010276 construction Methods 0.000 claims description 7
- 239000000758 substrate Substances 0.000 claims description 6
- 238000004458 analytical method Methods 0.000 abstract description 3
- 230000008569 process Effects 0.000 description 11
- 239000007787 solid Substances 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 6
- 239000004576 sand Substances 0.000 description 5
- 230000002902 bimodal effect Effects 0.000 description 4
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000006870 function Effects 0.000 description 4
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000002893 slag Substances 0.000 description 3
- 230000001133 acceleration Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 230000005499 meniscus Effects 0.000 description 2
- 238000012821 model calculation Methods 0.000 description 2
- 230000005641 tunneling Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/04—Devices for withdrawing samples in the solid state, e.g. by cutting
- G01N1/08—Devices for withdrawing samples in the solid state, e.g. by cutting involving an extracting tool, e.g. core bit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N19/00—Investigating materials by mechanical methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/006—Crack, flaws, fracture or rupture
- G01N2203/0067—Fracture or rupture
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0262—Shape of the specimen
- G01N2203/027—Specimens with holes or notches
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Abstract
The application discloses a testing method and a testing system for an internal friction angle and a cohesive force of foam modified soil, comprising the following steps: selecting dregs to be improved and a foaming agent for improvement to establish an indoor slump test model, and obtaining an experimental result, wherein the experimental result comprises: the change rule of the slump of the foam modified soil under different foaming multiplying factors and foam injection ratios; taking Laplace equation as a theoretical basis, and establishing a foam improved soil particle liquid bridge model; calibrating and adjusting macroscopic and microscopic mechanical parameters according to a change rule to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios; based on an indoor slump test model, introducing the mesoscopic parameter relation model into a foam improved soil particle liquid bridge model to obtain a final model; and (3) performing a simulation experiment by using the final model to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and cohesive force of the foam improved soil. The application perfects a foam improved soil theoretical model and a numerical analysis method.
Description
Technical Field
The application relates to the technical field of rock-soil mechanical parameter measurement, in particular to a testing method and a testing system for an internal friction angle and a cohesive force of foam modified soil.
Background
The foam modified soil is one kind of modified soil formed by adding foam into soil, and the main purpose of the modification is to change various physical and mechanical properties of the soil, such as internal friction angle, cohesion, permeability coefficient, etc. The foam is generally used for improving the slag soil excavated in the tunneling process of the shield machine and preventing bad phenomena such as mud cake formation, gushing, unsmooth slag discharge and the like in the tunneling process. In judging whether or not these adverse phenomena occur, the internal friction angle and cohesion are the most important parameters among them. Whether the internal friction angle and the cohesive force of the foam modified soil can be accurately measured is a key point of design quality and engineering success or failure.
The internal friction angle and the cohesive force are two important indexes of the rock-soil mechanical property, are important parameters required by stability analysis, numerical simulation and support structure design of engineering surrounding rocks such as foundation pits, foundations, slopes and tunnels, are also important parameters required to be well known and measured in the rock-soil engineering, geological engineering and other professions in the rock-soil mechanical theory learning and teaching process, and are usually tested by adopting indoor or field tests.
In indoor or field tests, triaxial and direct shear tests are generally used to test the internal friction angle and cohesion of the soil. Conventional triaxial tests employ cylindrical samples that are wrapped with rubber film in a pressure chamber. In the test, confining pressure sigma is applied to a sample by liquid in a pressure chamber 3 Consolidation. Then applying vertical axial pressure, i.e. applying a biasing force DeltaSigma 1 Until the sample shears out. The large principal stress at the time of sample failure is the vertical stress sigma 1 ＝σ 3 +Δσ 1 The small principal stress is the confining pressure sigma 3 . Sigma obtained from a sample 1 Sum sigma 3 A limit stress circle may be drawn. For the same soil, several samples are taken, and the confining pressure sigma is changed 3 The applied axial pressure sigma when the specimen shears out 1 And also changes, so that in turn, several more extreme stress circles can be plotted. Thus, a set (of at least three samples) of limit stress circles can be obtained when tested at different ambient pressures. The common tangent line of these stress circles is the shear strength envelope of the earth, and the internal friction angle and the cohesion c can be obtained from this envelope.
The direct shear test is to put the sample in a shear box, which is divided into an upper box and a lower box on a horizontal plane, one half is fixed, and the other half is pushed or pulled to generate horizontal displacement. The upper portion applies a positive vertical load through the rigid loading cap. The vertical load is generally unchanged in the test process, and the horizontal shear load, horizontal displacement and vertical deformation of the sample can be measured. From the area of the shear plane, the normal stress σ and the shear stress τ on the shear plane can be calculated. From the normal stresses sigma and tau at failure f The relationship can determine the intensity envelope of the soil. The intercept of the strength wrapping line is the cohesive force c', and the included angle between the strength wrapping line and the horizontal line is the internal friction angle。
However, both of these test methods have their limitations and disadvantages. The disadvantage of triaxial test is the principal stress sigma of the test specimen 2 ＝σ 3 In practice, the stress state of the soil body does not necessarily belong to the axisymmetric condition. The disadvantage of the direct shear test is that the shear plane is defined aboveThe plane between the lower boxes is cut rather than along the weakest surface of the soil sample. In addition, in the case of the foam-modified soil, since the foam rapidly decays with time, it breaks down, resulting in a change in the physical and mechanical properties of the foam-modified soil. The triaxial test and the direct shear test require longer time, so that the tested internal friction angle and cohesive force values have larger differences from the real values.
Thus, there is a need for a new method of testing foam for improved internal friction and cohesion of the soil, which overcomes the shortcomings of the current methods.
Disclosure of Invention
In order to overcome the defects of the conventional indoor test for measuring the internal friction angle and the cohesion of the foam modified soil, the test method for the real internal friction angle and the cohesion of the foam modified soil is provided. The method can test the internal friction angle and cohesive force of the foam modified soil before the foam does not decay, and meanwhile, the inaccuracy of test results caused by defects of a direct shear test and a triaxial test is avoided, and the error is small.
In order to achieve the above purpose, the application provides a testing method for improving the internal friction angle and cohesion of soil by foam, comprising the following steps:
selecting dregs to be improved and a foaming agent for improvement to establish an indoor slump test model to obtain an experimental result, wherein the experimental result comprises the following steps: the change rule of the slump of the foam modified soil under different foaming multiplying factors and foam injection ratios;
taking Laplace equation as a theoretical basis, and establishing a foam improved soil particle liquid bridge model;
calibrating and adjusting macroscopic and microscopic mechanical parameters according to the change rule to obtain microscopic parameter relation models under different foaming multiplying factors and foam injection ratios;
based on the indoor slump test model, the mesoscopic parameter relation model is imported into the foam improved soil particle liquid bridge model to obtain a final model;
and performing a simulation experiment by using the final model to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and the cohesive force of the foam improved soil.
Preferably, by using the foam-improved soil particle liquid bridge model, the interaction force between particles is calculated by analyzing each numerical parameter among particles in the process of slumping of the foam-improved soil, and the interaction force comprises: surface tension and substrate suction.
Preferably, when the calibration and adjustment are performed, parameter fitting is performed on each microscopic parameter under different foaming multiplying power and foaming injection ratio, so as to obtain the relation between the macroscopic parameter of the foam improved soil and the microscopic parameter of the discrete element model, and further obtain the relation function of slump of the foam improved soil under different foaming multiplying power and foaming injection ratio.
Preferably, different foaming multiplying power and foam injection ratio are obtained by modifying the values of the internal friction angle and cohesion.
Preferably, the final model is compared with the experimental result, the accuracy of the final model is judged through slump, and if the result is not identical, the internal friction angle and the cohesive force are adjusted to simulate again until the result is identical.
The application also provides a testing system for improving the internal friction angle and cohesive force of the soil by using the foam, which comprises the following steps: the device comprises an experiment module, a construction module, a calibration module, an importing module and a comparison module;
the experimental module is used for selecting dregs to be improved and a foaming agent for improvement to establish an indoor slump test model to obtain experimental results, and the experimental results comprise: the change rule of the slump of the foam modified soil under different foaming multiplying factors and foam injection ratios;
the construction module is used for building a foam improved soil particle liquid bridge model based on a Laplace equation;
the calibration module is used for calibrating and adjusting macroscopic and microscopic mechanical parameters according to the change rule to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios;
the importing module is used for importing the mesoscopic parameter relation model into the foam improved soil particle liquid bridge model based on the indoor slump test model to obtain a final model;
and the comparison module is used for carrying out a simulation experiment by utilizing the final model to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and the cohesive force of the foam improved soil.
Preferably, by using the foam-improved soil particle liquid bridge model, the interaction force between particles is calculated by analyzing each numerical parameter among particles in the process of slumping of the foam-improved soil, and the interaction force comprises: surface tension and substrate suction.
Preferably, the workflow of the calibration module includes: and respectively carrying out parameter fitting on each mesoscopic parameter under different foaming multiplying powers and foam injection ratios to obtain the relation between the macroscopic parameters of the foam improved soil and the mesoscopic parameters of the discrete element model, thereby obtaining the relation function of slump of the foam improved soil under different foaming multiplying powers and foam injection ratios.
Compared with the prior art, the application has the following beneficial effects:
according to the application, from a microscopic scale, numerical simulation research on the slump characteristics of the foam improved soil under different foaming multiplying power and foam injection ratio is carried out, a liquid bridge model among slag soil particles is established, static liquid bridge force among particles is calculated, the slump process of the foam improved soil is simulated, and compared with the result of an indoor test, so that the internal friction angle and cohesion value of the foam improved soil are deduced, and a foam improved soil theoretical model and a numerical analysis method are perfected.
Drawings
In order to more clearly illustrate the technical solutions of the present application, the drawings that are needed in the embodiments are briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a method according to an embodiment of the application;
FIG. 2 is a diagram of a standard sand grading diagram used for simulation in accordance with an embodiment of the present application;
FIG. 3 is a schematic illustration of a particle-liquid bridge model in accordance with an embodiment of the present application;
FIG. 4 is a graph comparing results of experiments and simulations of an embodiment of the present application;
fig. 5 is a schematic diagram of a system structure according to an embodiment of the application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In order that the above-recited objects, features and advantages of the present application will become more readily apparent, a more particular description of the application will be rendered by reference to the appended drawings and appended detailed description.
Example 1
Fig. 1 is a schematic flow chart of a method according to an embodiment of the application.
Firstly, selecting dregs to be improved and a foaming agent for improvement to establish an indoor slump test model, and obtaining an experimental result, wherein the experimental result comprises: the foam improves the change rule of the soil slump under different foaming multiplying factors and foam injection ratios.
In the embodiment, chinese ISO standard sand is adopted, the grading curve of the sand is shown in figure 2, foam with the foam expansion rate (FIR) of 20 is prepared through a foaming device, a slump test in a foam modified soil chamber is developed through a slump test device, a slump test model in the chamber is built, and an experimental result is obtained.
And then, based on the Laplace equation as a theoretical basis, establishing a foam improved soil particle liquid bridge model.
The foam improvement soil particle liquid bridge model calculates interaction force among particles by analyzing each numerical parameter among particles in the process of slumping of the foam improvement soil, wherein the interaction force comprises the following components: surface tension and substrate suction. And calculating the liquid bridge force among the particles according to each parameter of the inter-particle liquid bridge of the liquid bridge model.
A liquid bridge is a segment of liquid that connects to a solid surface and creates a liquid bridge force on the solid surface. Although the liquid bridge force is weak, the hydraulic characteristics of the solid bulk particle group are greatly affected. Meanwhile, whether the liquid bridge can exist stably between two particles is the basis of the research on the dynamic behavior of the liquid bridge.
As shown in fig. 3, the interaction soil particle liquid bridge model is taken as a study object, and the capillary pressure (i.e. the matrix suction force) is expressed as:
wherein gamma is the surface tension of the gas-liquid interface; c is the average curvature of the liquid bridge; radius of curvature r of gas-liquid interface in Cartesian coordinates 1 And r 2 Can be expressed as:
wherein y (x) represents the profile of the liquid-gas interface curve; y' (x) is the first derivative of y (x) with respect to x; y "(x) is the second derivative of y (x) about x, the x axis coinciding with the symmetry axis of the liquid bridge, through the center of the connecting solid particles; x is x 1 And x 2 For the x-coordinate at the three-phase contact of the solid-liquid-gas interface, the corresponding meniscus volume V m And inter-particle distance D can be expressed as:
D＝R 2 (1-acos(x 2 ))+x 2 +R 1 (1-acos(x 1 ))-x 1
wherein R is 1 And R is 2 Respectively the radii of two solid particles; a is dimensionless conductance.
The interparticle forces caused by surface tension and matrix suction are:
wherein y is 0 Is the neck radius corresponding to the contour vertex, the relationship between deltau and the capillary bimodal configuration can be represented by a system of nonlinear coupling equations. Based on this, the liquid bridge control model (foam-modified soil particle liquid bridge model) can be expressed as the following function:
wherein,,representing a system of nonlinear coupling equations between deltau and D and the capillary bimodal configuration.
And calibrating and adjusting macroscopic and microscopic mechanical parameters according to the change rule to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios.
And calibrating and adjusting macroscopic and microscopic mechanical parameters by using discrete meta-software yade to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios.
Defining inter-particle liquid bridge model calculation parameters, including: surface tension gamma, radius of curvature r of gas-liquid interface 1 And r 2 Profile y (x) of liquid-gas interface curve, gravitational acceleration g, etc. After the calculation parameters are calibrated, the inter-particle acting force caused by the surface tension and the matrix suction is calculated, and the inter-particle liquid acting force and the particle gravity are substituted into a Newton formula to calculate the movement track of each particle.
After the steps are finished, the mesoscopic parameter relation model is imported into the foam improved soil particle liquid bridge model based on the indoor slump test model, and a final model is obtained.
And finally, performing a simulation experiment by using a final model to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and cohesive force of the foam improved soil.
The numerical values of the internal friction angle and the cohesion are modified to modify the foaming multiplying power and the foam injection ratio of the foam, so that the slump process of the foam modified soil under different foaming multiplying powers and foam injection ratios is simulated. And comparing and matching the slump value obtained by simulation with the value obtained by an indoor slump test, and deducing the internal friction angle and cohesive force of the foam modified soil. The result pairs are shown in fig. 4, for example.
Example two
Fig. 5 is a schematic diagram of a system structure according to an embodiment of the present application, including: the device comprises an experiment module, a construction module, a calibration module, an introduction module and a comparison module. The experimental module is used for selecting dregs to be improved and a foaming agent for improvement to establish an indoor slump test model, so as to obtain experimental results, wherein the experimental results comprise: the change rule of the slump of the foam modified soil under different foaming multiplying factors and foam injection ratios; the construction module is used for building a foam improved soil particle liquid bridge model based on a Laplace equation; the calibration module is used for calibrating and adjusting macroscopic and microscopic mechanical parameters according to the change rule to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios; the importing module is used for importing the mesoscopic parameter relation model into the foam improved soil particle liquid bridge model based on the indoor slump test model to obtain a final model; the comparison module is used for carrying out a simulation experiment by utilizing the final model to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and the cohesive force of the foam improved soil.
In the following, the present embodiment will be described in detail to solve the technical problems in actual life.
Firstly, selecting dregs to be improved and a foaming agent for improvement by using an experimental module to establish an indoor slump test model, so as to obtain an experimental result, wherein the experimental result comprises: the foam improves the change rule of the soil slump under different foaming multiplying factors and foam injection ratios.
In the embodiment, chinese ISO standard sand is adopted, the grading curve of the sand is shown in figure 2, foam with the foam expansion rate (FIR) of 20 is prepared through a foaming device, a slump test in a foam modified soil chamber is developed through a slump test device, a slump test model in the chamber is built, and an experimental result is obtained.
And then, the construction module establishes a foam improved soil particle liquid bridge model based on the Laplace equation.
The foam improvement soil particle liquid bridge model calculates interaction force among particles by analyzing each numerical parameter among particles in the process of slumping of the foam improvement soil, wherein the interaction force comprises the following components: surface tension and substrate suction. And calculating the liquid bridge force among the particles according to each parameter of the inter-particle liquid bridge of the liquid bridge model.
A liquid bridge is a segment of liquid that connects to a solid surface and creates a liquid bridge force on the solid surface. Although the liquid bridge force is weak, the hydraulic characteristics of the solid bulk particle group are greatly affected. Meanwhile, whether the liquid bridge can exist stably between two particles is the basis of the research on the dynamic behavior of the liquid bridge.
As shown in fig. 3, the interaction soil particle liquid bridge model is taken as a study object, and the capillary pressure (i.e. the matrix suction force) is expressed as:
wherein gamma is the surface tension of the gas-liquid interface; c is the average curvature of the liquid bridge; radius of curvature r of gas-liquid interface in Cartesian coordinates 1 And r 2 Can be expressed as:
wherein y (x)A profile representing a liquid-gas interface curve; y' (x) is the first derivative of y (x) with respect to x; y "(x) is the second derivative of y (x) about x, the x axis coinciding with the symmetry axis of the liquid bridge, through the center of the connecting solid particles; x is x 1 And x 2 For the x-coordinate at the three-phase contact of the solid-liquid-gas interface, the corresponding meniscus volume V m And inter-particle distance D can be expressed as:
D＝R 2 (1-acos(x 2 ))+x 2 +R 1 (1-acos(x 1 ))-x 1
wherein R is 1 And R is 2 Respectively the radii of two solid particles; a is dimensionless conductance.
The interparticle forces caused by surface tension and matrix suction are:
wherein y is 0 Is the neck radius corresponding to the contour vertex, the relationship between deltau and the capillary bimodal configuration can be represented by a system of nonlinear coupling equations. Based on this, the liquid bridge control model (foam-modified soil particle liquid bridge model) can be expressed as the following function:
wherein,,representing a system of nonlinear coupling equations between deltau and D and the capillary bimodal configuration.
And calibrating and adjusting macroscopic and microscopic mechanical parameters according to the change rule to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios.
And calibrating and adjusting macroscopic and microscopic mechanical parameters by using discrete meta-software yade to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios.
Defining inter-particle liquid bridge model calculation parameters, including: surface tension gamma, radius of curvature r 1 And r 2 Profile y (x) of liquid-gas interface curve, gravitational acceleration g, etc. After the calculation parameters are calibrated, the inter-particle acting force caused by the surface tension and the matrix suction is calculated, and the inter-particle liquid acting force and the particle gravity are substituted into a Newton formula to calculate the movement track of each particle.
After the steps are finished, the importing module imports the mesoscopic parameter relation model into the foam improved soil particle liquid bridge model based on the indoor slump test model to obtain a final model.
And finally, performing a simulation experiment by using a final model by a comparison module to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and the cohesive force of the foam improved soil.
The numerical values of the internal friction angle and the cohesion are modified to modify the foaming multiplying power and the foam injection ratio of the foam, so that the slump process of the foam modified soil under different foaming multiplying powers and foam injection ratios is simulated. And comparing and matching the slump value obtained by simulation with the value obtained by an indoor slump test, and deducing the internal friction angle and cohesive force of the foam modified soil. The result pairs are shown in fig. 4, for example.
The above embodiments are merely illustrative of the preferred embodiments of the present application, and the scope of the present application is not limited thereto, but various modifications and improvements made by those skilled in the art to which the present application pertains are made without departing from the spirit of the present application, and all modifications and improvements fall within the scope of the present application as defined in the appended claims.
Claims (8)
1. A testing method for the internal friction angle and cohesion of foam modified soil is characterized by comprising the following steps:
selecting dregs to be improved and a foaming agent for improvement to establish an indoor slump test model to obtain an experimental result, wherein the experimental result comprises the following steps: the change rule of the slump of the foam modified soil under different foaming multiplying factors and foam injection ratios;
taking Laplace equation as a theoretical basis, and establishing a foam improved soil particle liquid bridge model;
calibrating and adjusting macroscopic and microscopic mechanical parameters according to the change rule to obtain microscopic parameter relation models under different foaming multiplying factors and foam injection ratios;
based on the indoor slump test model, the mesoscopic parameter relation model is imported into the foam improved soil particle liquid bridge model to obtain a final model;
and performing a simulation experiment by using the final model to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and the cohesive force of the foam improved soil.
2. The method for testing the internal friction angle and cohesion of a foam-modified soil according to claim 1, wherein the interaction force between particles is calculated by analyzing each numerical parameter between particles during the slump of the foam-modified soil using the foam-modified soil particle liquid bridge model, the interaction force comprising: surface tension and substrate suction.
3. The method for testing the internal friction angle and the cohesion of the foam-improved soil according to claim 1, wherein when the calibration and the adjustment are carried out, parameter fitting is carried out on each mesoscopic parameter under different foaming multiplying powers and foaming injection ratios respectively, the relation between the macroscopic parameters of the foam-improved soil and the mesoscopic parameters of the discrete element model is obtained, and further, the relation function of slump of the foam-improved soil under different foaming multiplying powers and foaming injection ratios is obtained.
4. The method for testing the internal friction angle and the cohesion of the foam improved soil according to claim 1, wherein different foaming ratios and foam injection ratios are obtained by modifying the values of the internal friction angle and the cohesion.
5. The method according to claim 4, wherein the final model is compared with the experimental result, the accuracy of the final model is judged by slump, and if the results do not match, the internal friction angle and the cohesion are re-simulated by adjusting the internal friction angle and the cohesion until the results match.
6. A test system for improving the internal friction angle and cohesion of the soil by foam, comprising: the device comprises an experiment module, a construction module, a calibration module, an importing module and a comparison module;
the experimental module is used for selecting dregs to be improved and a foaming agent for improvement to establish an indoor slump test model to obtain experimental results, and the experimental results comprise: the change rule of the slump of the foam modified soil under different foaming multiplying factors and foam injection ratios;
the construction module is used for building a foam improved soil particle liquid bridge model based on a Laplace equation;
the calibration module is used for calibrating and adjusting macroscopic and microscopic mechanical parameters according to the change rule to obtain microscopic parameter relation models under different foaming multiplying powers and foam injection ratios;
the importing module is used for importing the mesoscopic parameter relation model into the foam improved soil particle liquid bridge model based on the indoor slump test model to obtain a final model;
and the comparison module is used for carrying out a simulation experiment by utilizing the final model to obtain a simulation result, and comparing the simulation result with the experiment result to obtain the internal friction angle and the cohesive force of the foam improved soil.
7. The system for testing the internal friction angle and cohesion of a foam improved soil according to claim 6, wherein the interaction force between particles is calculated by analyzing each numerical parameter between particles during the slump of the foam improved soil using the foam improved soil particle liquid bridge model, the interaction force comprising: surface tension and substrate suction.
8. The foam improved soil internal friction angle and cohesion testing system of claim 6, wherein the workflow of said calibration module comprises: and respectively carrying out parameter fitting on each mesoscopic parameter under different foaming multiplying powers and foam injection ratios to obtain the relation between the macroscopic parameters of the foam improved soil and the mesoscopic parameters of the discrete element model, thereby obtaining the relation function of slump of the foam improved soil under different foaming multiplying powers and foam injection ratios.
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