Coarse-grained soil strength prediction method considering permeation erosion and mudstone fine grain content

Abstract

The invention provides a coarse-grained soil strength prediction method considering permeation erosion and mudstone fine grain content, and belongs to the technical field of soil strength prediction. Aiming at the defects in the prior art, the influence of penetration erosion on the shearing performance of coarse-grained soil with different mudstone fine grain contents is considered, and the siliceous mudstone coarse-grained soil strength prediction model considering the penetration erosion effect is constructed, so that the strength prediction precision can be improved; therefore, a better guiding effect is provided for design, construction and operation maintenance of the coarse-grained soil highway subgrade in the mountainous area.

Description

Technical Field

[0001] The present application belongs to the technical field of soil strength prediction, and specifically relates to a method for predicting the strength of coarse-grained soil taking into account penetration erosion and the fine-grained content of mudstone. Background Art

[0002] Coarse-grained soil is often used as a filler for highway embankments because of its good permeability, high compressive strength, and high compaction density. However, rainwater penetration and erosion can easily cause rheology in coarse-grained soil fillers, gradually weakening the water stability, strength, and stability of the embankment, leading to local or overall instability, posing a threat to the overall life of the embankment and driving safety. The reason is that coarse-grained soil has weak cohesion and impermeability, and fine particles are easily lost under seepage, forming progressive seepage deformation. In the complex process of water-soil interaction, the loss of fine particles causes changes in the mesostructure and mechanical properties of the soil, reducing the shear strength and stability of the soil. Therefore, studying the mesoscopic characteristics and shear properties of coarse-grained soil after seepage is crucial to ensuring the normal service of mountain roads.

[0003] Regarding the impact of rainfall on the mechanical properties of coarse-grained soil, the current mainstream research only considers the wetting effect (change in water content) caused by rainwater infiltration. Specifically, the increase in water content caused by rainwater infiltration may cause soil volume expansion, leading to deformation and loosening; secondly, the increase in water content may weaken its cohesion and internal friction, reducing its shear strength and stability. However, rainwater infiltration not only brings wetting to coarse-grained soil, but also accompanies particle erosion. Coarse-grained soil has a large porosity. Under the infiltration and erosion of rainwater, the fine-grained components in the coarse-grained soil migrate downward and deposit, and the upper skeleton is hollowed out, causing the microstructure of the internal filler of the embankment to change, and its mechanical properties will also decrease. Therefore, the relevant technology only considers the wetting effect caused by rainwater infiltration, which will result in low soil strength prediction accuracy and cannot be used to guide actual construction. Further research on the strength degradation evolution of coarse-grained soil under infiltration erosion is urgently needed. Summary of the invention

[0004] The present application provides a method for predicting the strength of coarse-grained soil taking into account seepage erosion and fine-grained mudstone content. In view of the defects in the prior art, the influence of seepage erosion on the shear properties of coarse-grained soil with different fine-grained mudstone contents is considered, and a strength weakening prediction model taking into account the seepage erosion effect is constructed. The accuracy of strength prediction can be improved to better provide guidance for the design, construction, operation and maintenance of coarse-grained soil highway subgrades in mountainous areas.

[0005] In order to solve the above technical problems, the technical solution of this application is:

[0006] A method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone comprises the following steps:

[0007] Step S1, configuring a plurality of coarse-grained soil samples with different fine-grained mass proportions η, and performing penetration erosion treatment on the coarse-grained soil samples;

[0008] Step S2, measuring the shear strength of the coarse-grained soil sample after the seepage erosion treatment at the real stress level, and constructing the stress-strain curve of the coarse-grained soil sample under different seepage erosion forces p0 and confining pressures σ3;

[0009] Step S3, based on the stress-strain curve, analyze the effect of the fine particle mass ratio η and the penetration erosion force p0 on the shear strength σ1-σ3, cohesion c and internal friction angle of the coarse-grained soil sample. The strength failure criterion applicable to the coarse-grained soil sample was determined by fitting the linear function c(η, p0) related to the cohesion c and the fine particle mass ratio η, the penetration erosion force p0, and the internal friction angle Linear function related to fine particle mass ratio η and penetration erosion force p0 The linear function c(η, p0) and Substituting into the equation of the strength failure criterion, the strength prediction model K of siliceous mudstone coarse-grained soil considering the seepage erosion effect is obtained. MC (η, p0);

[0010] Step S4, using the strength prediction model K MC (η, p0) predicts the strength of coarse-grained soil with a fine particle mass ratio of η under the action of penetration erosion force p0.

[0011] As a preferred improvement, the coarse-grained soil sample is prepared by using cohesiveless angular gravel, sand particles and mudstone fine particles.

[0012] As a preferred improvement, in step S1, the process of penetration erosion specifically includes the following steps:

[0013] The coarse-grained soil sample is placed in a rubber membrane with openings at both ends, and the openings at both ends of the rubber membrane cover a permeable stone with a diameter of 50 mm, and the coarse-grained soil sample is tightly fitted to the permeable stone;

[0014] The coarse-grained soil sample covered with the rubber film is placed into the large end of the funnel, and the small end of the funnel is connected to the variable frequency water pump through a pipeline;

[0015] The variable frequency water pump is started to transport the water in the water tank to the funnel to flush the soil sample, thereby simulating the infiltration and erosion process of rainfall under natural conditions;

[0016] The bottom of the coarse-grained soil sample is taken as the starting point for water seepage, and the treatment is carried out for 10 minutes. The treated coarse-grained soil sample is allowed to stand still and weighed in real time to ensure that the water content of the coarse-grained soil sample remains unchanged before and after flushing.

[0017] As a preferred improvement, the linear function c(η, p0) and Respectively expressed as:

[0018] c(η,p0)=c0(η)-k c (η)p0;

[0019]

[0020] Where c0(η) represents the initial cohesion; represents the initial internal friction angle; k c (η), They represent the cohesion attenuation rate and the internal friction angle attenuation rate respectively, and both are functions related to the fine particle mass proportion η.

[0021] As a preferred improvement, c0(η)=A+Bη; k c (η) = α(η-η critical ) 2 +b;

[0022] Where A, B, a, and b are all fitting parameters; η critical is the critical value of the fine particle mass ratio η, which is determined by the turning point of the relationship curve between the fine particle mass ratio η and the cohesion c or the relationship between the fine particle mass ratio η and the internal friction angle The turning point of the relationship curve is obtained;

[0023]

[0024] In the formula, C, D, k are all fitting parameters.

[0025] As a preferred improvement, the strength prediction model K MC (η, p0) is expressed as:

[0026]

[0027] The beneficial effects of this application are:

[0028] In view of the defects in the existing technology, the influence of seepage erosion on the shear properties of coarse-grained soil with different mudstone fine-particle contents was considered, and a strength weakening prediction model of siliceous mudstone coarse-grained soil considering the seepage erosion effect was constructed. This can improve the accuracy of strength prediction and provide better guidance for the design, construction, operation and maintenance of coarse-grained soil highway subgrades in mountainous areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0030] Figure 1 A gradation curve diagram showing a coarse-grained soil sample;

[0031] Figure 2 It means a device for treating seepage erosion of coarse-grained soil;

[0032] Figure 3 It represents the stress-strain curve of coarse-grained soil sample under different confining pressures σ3 when the penetration erosion force p0 = 0 kPa;

[0033] Figure 4 It represents the stress-strain curve of coarse-grained soil sample under different confining pressures σ3 when the penetration erosion force p0 = 40 kPa;

[0034] Figure 5 It represents the stress-strain curve of coarse-grained soil sample under different confining pressures σ3 when the penetration erosion force p0 = 50 kPa;

[0035] Figure 6 It represents the stress-strain curve of coarse-grained soil sample under different confining pressures σ3 when the penetration erosion force p0 = 60 kPa;

[0036] Figure 7 It represents the stress-strain curve of coarse-grained soil sample under different confining pressures σ3 when the penetration erosion force p0 = 70 kPa;

[0037] Figure 8 Indicates the shear peak strength (σ1-σ3) max -p0 relationship curve;

[0038] Fig. 9 It represents the stress Mohr circle and strength envelope of coarse-grained soil samples under different confining pressures σ3 when the penetration erosion force p0 = 0 kPa;

[0039] Fig.10 It represents the stress Mohr circle and strength envelope of coarse-grained soil samples under different confining pressures σ3 when the penetration erosion force p0 = 40 kPa;

[0040] Fig.11 It represents the stress Mohr circle and strength envelope of coarse-grained soil samples under different confining pressures σ3 when the penetration erosion force p0 = 50 kPa;

[0041] Fig.12It represents the stress Mohr circle and strength envelope of coarse-grained soil samples under different confining pressures σ3 when the penetration erosion force p0 = 60 kPa;

[0042] Fig.13 It represents the stress Mohr circle and strength envelope of coarse-grained soil samples under different confining pressures σ3 when the penetration erosion force p0 = 70 kPa;

[0043] Fig.14 represents the penetration erosion force p0 and the internal friction angle of coarse-grained soil Relationship diagram with cohesion c;

[0044] Fig.15 The shear peak strength diagram of coarse-grained soil samples with different fine particle contents η;

[0045] Fig.16 The graph represents the degree of peak strength attenuation of coarse-grained soil samples with different fine particle contents η;

[0046] Fig.17 The diagram represents the effect of seepage erosion on the cohesion c of coarse-grained soil with different fine particle contents η;

[0047] Fig.18 The internal friction angle of coarse-grained soil with different fine-grain content η is expressed as The influence diagram of

[0048] Fig.19 It represents the Mohr-Coulomb strength failure condition diagram;

[0049] Fig. 20 represents the initial cohesion c0 and the cohesion decay rate k c The variation pattern of η with different fine particle mass proportions;

[0050] Fig.21 represents the initial internal friction angle and internal friction angle attenuation rate The graph showing the variation of η with different fine particle mass proportions;

[0051] Fig. 22 It represents the prediction model image under the confining pressure σ3 = 20 kPa;

[0052] Fig.23 It represents the prediction model image under the confining pressure σ3 = 30 kPa;

[0053] Fig.24 It represents the prediction model image under the confining pressure σ3 = 40 kPa;

[0054] Fig.25 It represents the prediction model image under the confining pressure σ3 = 50 kPa;

[0055] Fig.26It represents the relative error hotspot map between the predicted value and the measured value under the confining pressure σ3 = 50 kPa;

[0056] Fig. 27 It shows the heat map of relative error between the predicted value and the measured value when the fine particle mass proportion η = 3%. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0058] Please refer to Figure 1-Figure 27 This embodiment provides a method for predicting the strength of coarse-grained soil taking into account the penetration erosion and the fine-grained content of mudstone, comprising the following steps:

[0059] A method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone comprises the following steps:

[0060] Step S1, configuring a plurality of coarse-grained soil samples with different fine-grained mass proportions η, and performing penetration erosion treatment on the coarse-grained soil samples;

[0061] Step S2, measuring the shear strength of the coarse-grained soil sample after the seepage erosion treatment at the real stress level, and constructing the stress-strain curve of the coarse-grained soil sample under different seepage erosion forces p0 and confining pressures σ3;

[0062] Step S3, based on the stress-strain curve, analyze the effect of the fine particle mass ratio η and the penetration erosion force p0 on the shear strength σ1-σ3, cohesion c and internal friction angle of the coarse-grained soil sample. The strength failure criterion applicable to the coarse-grained soil sample was determined by fitting the linear function c(η, p0) related to the cohesion c and the fine particle mass ratio η, the penetration erosion force p0, and the internal friction angle Linear function related to fine particle mass ratio η and penetration erosion force p0 The linear function c(η, p0) and Substituting into the equation of the strength failure criterion, the strength prediction model K of siliceous mudstone coarse-grained soil considering the seepage erosion effect is obtained. MC (η, p0);

[0063] Step S4, using the strength prediction model K MC (η, p0) predicts the strength of coarse-grained soil with a fine particle mass ratio of η under the action of penetration erosion force p0.

[0064] The coarse-grained soil sample is prepared by using cohesionless angular gravel, sand particles and mudstone fine particles.

[0065] In step S1, the penetration erosion process specifically includes the following steps:

[0066] The coarse-grained soil sample is placed in a rubber membrane with openings at both ends, and the openings at both ends of the rubber membrane cover a permeable stone with a diameter of 50 mm, and the coarse-grained soil sample is tightly fitted to the permeable stone;

[0067] The coarse-grained soil sample covered with the rubber film is placed into the large end of the funnel, and the small end of the funnel is connected to the variable frequency water pump through a pipeline;

[0068] The variable frequency water pump is started to transport the water in the water tank to the funnel to flush the soil sample, thereby simulating the infiltration and erosion process of rainfall under natural conditions;

[0069] The bottom of the coarse-grained soil sample is taken as the starting point for water seepage, and the treatment is carried out for 10 minutes. The treated coarse-grained soil sample is allowed to stand still and weighed in real time to ensure that the water content of the coarse-grained soil sample remains unchanged before and after flushing.

[0070] The linear function c(η, p0) and Respectively expressed as:

[0071] c(η,p0)=c0(η)-k c (η)p0;

[0072]

[0073] Where c0(η) represents the initial cohesion; represents the initial internal friction angle; k c (η), They represent the cohesion attenuation rate and the internal friction angle attenuation rate, respectively, and are functions related to the fine particle mass proportion η;

[0074] in:

[0075] c0(η)=A+Bη;

[0076] k c (η) = α(η-η critical ) 2 +b;

[0077] Where A, B, a, and b are all fitting parameters; η critical is the critical value of the fine particle mass ratio η, which is determined by the turning point of the relationship curve between the fine particle mass ratio η and the cohesion c or the relationship between the fine particle mass ratio η and the internal friction angle The turning point of the relationship curve is obtained;

[0078]

[0079] In the formula, C, D, k are all fitting parameters.

[0080] The intensity prediction model K MC (η, p0) is expressed as:

[0081]

[0082] Example 1

[0083] In this embodiment, the coarse-grained soil is taken from the slag soil-rock mixture produced by the excavation of a certain cutting section of the Second Ring Road in Hangzhou, and is dried, crushed and sieved.

[0084] In this embodiment, fine particles with a particle size of <0.075 mm, sand particles with a particle size of 0.075-0.5 mm, 0.5-2.0 mm, and angular gravels with a particle size of 2.0-5.0 mm, 5.0-10.0 mm are selected, and a total of 5 kinds of coarse-grained soil with different fine particle mass proportions η (η=3%, 6%, 9%, 12%, 15%) are set to form coarse-grained soil samples. Compaction experiments are carried out on each coarse-grained soil sample to obtain the optimal moisture content and maximum dry density. The physical parameters of each sample are shown in Table 1, and the gradation curve is shown in Table 1. Figure 1 shown.

[0085] Table 1 Physical parameters of coarse-grained soil samples

[0086]

[0087] The shape of the coarse-grained soil sample is cylindrical, with a diameter of d = 50 mm, a height of h = 100 mm, and a height-to-width ratio of H / D = 2. The ratio of the diameter of the coarse-grained soil sample to the maximum particle size is 5, which can basically eliminate the influence of the size effect.

[0088] The coarse-grained soil sample was mixed at the optimal moisture content and placed in a sealed box for 24 hours. The sample was prepared by layered vibration method, divided into 5 layers. After each layer was compacted, the top surface of the layer was roughened and then the next layer was compacted. The last layer was leveled. The relative density of the coarse-grained soil sample was controlled by controlling the quality and height of each layer. The compaction degree was controlled at about 95%, meeting the requirements of the "Highway Subgrade Design Code" (JTGD30-2015).

[0089] Please refer to Figure 2A penetration erosion treatment device is used to carry out a penetration erosion experiment on each coarse-grained soil sample. The penetration erosion device includes a water tank 10, a variable frequency water pump 20 and a funnel 30. The water tank 10, the variable frequency water pump 20 and the funnel 30 are connected in sequence through pipelines, wherein the pipeline is connected to the small mouth end of the funnel 30, and the coarse-grained soil sample abuts against the large mouth end of the funnel 30. The variable frequency water pump 20 is used to pump the water in the water tank 10 into the funnel 30 to flush the coarse-grained soil sample.

[0090] The specific operation of the penetration erosion test is as follows: put the coarse-grained soil sample into the rubber membrane, and cover the upper and lower ends of the coarse-grained soil sample with permeable stones with a diameter of 50mm, and the permeable stones are tightly fitted with the coarse-grained soil sample. Put the coarse-grained soil sample covered with the rubber membrane into the inverted metal funnel, and connect the top of the metal funnel to the water pipe, and tie the connection tightly with a binding belt. Turn on the water source, start the variable frequency water pump (the adjustable water pressure range is 0-450kPa), and deliver water to the metal funnel to flush the sample. Take the bottom as the starting point for water seepage, treat for 10 minutes, let the treated sample stand, and weigh it in real time to ensure that the water content of the sample remains unchanged before and after flushing.

[0091] The infiltration erosion force p0 and rainfall intensity P satisfy the following relationship:

[0092] p0=P·ρ w g / 1000;

[0093] In the formula, ρ w is the water density, take 1000kg / m 3 ; g is the acceleration due to gravity, which is 9.81 m / s 2 .

[0094] Under heavy rain and torrential rain, the rainfall intensity every 12 hours is 4.2~8.7mm / h. According to the above formula, the corresponding seepage erosion force is 40.8~85.7kPa. Therefore, four working conditions of seepage erosion force p0=40kPa, 50kPa, 60kPa and 70kPa are proposed to fully simulate the seepage erosion process under heavy rain and torrential rain.

[0095] The shear strength of coarse-grained soil samples under the true stress level was measured using the GDS standard stress path triaxial apparatus, with an optional shear rate range of 0.002-4.5 mm / min, a confining pressure of 0-2.0 MPa, and a pressure resolution of 0.5 kPa. The test loading conditions are shown in Table 2. The shear rate was 0.24 mm / min, and the test was terminated when the axial strain reached 20%.

[0096] Table 2 Loading conditions of static triaxial test of coarse-grained soil samples

[0097]

[0098]

[0099] The calculation process of loading confining pressure σ3 is:

[0100] σ3=K0(σ0+γh);

[0101] Where K0 is the lateral earth pressure coefficient, calculated as K0 = ν / (1-ν), ν is the Poisson's ratio, which is taken as 0.45; σ0 is the road surface cover weight, which is taken as 24.5 kN / m 3 ; γ is the bulk density of coarse-grained soil, taken as 25kN / m 3 ; h is the depth from the top of the roadbed.

[0102] The stress-strain curves of coarse-grained soil samples under different p0 and σ3 (η=3%) are shown in Figure 3-7 As shown, Figure 3 It represents the stress-strain curve of coarse-grained soil sample under different σ3 when p0=0kPa; Figure 4 It represents the stress-strain curve of coarse-grained soil sample under different σ3 when p0=40kPa; Figure 5 It represents the stress-strain curve of coarse-grained soil sample under different σ3 when p0=50kPa; Figure 6 It represents the stress-strain curve of coarse-grained soil sample under different σ3 when p0=60kPa; Figure 7 It represents the stress-strain curve of coarse-grained soil sample under different σ3 when p0=70kPa.

[0103] from Figure 3-7 It can be seen that:

[0104] (1) Under a confining pressure of 20-50 kPa, both coarse-grained soil samples with and without infiltration erosion treatment showed obvious strain "softening phenomenon";

[0105] (2) Sample failure point (i.e., shear peak strength (σ1-σ3) in the figure) max The corresponding axial strain) occurs at ε 1critical =2.2%-5.3%, and the smaller σ3 is, the greater ε 1critical The smaller;

[0106] Construct shear peak strength (σ1-σ3) max -p0 relationship curve, such as Figure 8 As shown in the figure, the mechanical properties of coarse-grained soil have obvious weakening effect of penetration erosion. Under the same σ3, the (σ1-σ3) of the sample max The small confining pressure change used in this test has no significant effect on the strength weakening difference caused by penetration erosion. For example, when p0 = 70 kPa, σ3 = 30 kPa corresponds to (σ1-σ3) maxThe drop is 133.2 kPa, σ3 = (σ1-σ3) corresponding to 50 kPa max The decrease was 146.4 kPa, with no significant difference. Under the five confining pressures σ3, the decrease was maintained at around 133.1 kPa to 231.1 kPa.

[0107] Figure 9-13 The stress Mohr circle and strength envelope of coarse-grained soil samples treated with different p0 at different σ3 were plotted. Fig. 9 It represents the stress Mohr circle and strength envelope of coarse-grained soil specimens under different σ3 when p0 = 0 kPa; Fig.10 It represents the stress Mohr circle and strength envelope of coarse-grained soil specimens under different σ3 when p0 = 40 kPa; Fig.11 It represents the stress Mohr circle and strength envelope of coarse-grained soil specimens under different σ3 when p0 = 50 kPa; Fig.12 It represents the stress Mohr circle and strength envelope of coarse-grained soil specimens under different σ3 when p0 = 60 kPa; Fig.13 It represents the stress Mohr circle and strength envelope of coarse-grained soil samples under different σ3 when p0=70kPa. Figure 9-13 It can be seen that within the small confining pressure range of 20 to 50 kPa, the coarse-grained soil treated with seepage erosion and the untreated soil follows the linear Mohr-Coulomb strength failure criterion, and the envelope fitting determination coefficient R 2 All are greater than 0.99.

[0108] Fig.14 The internal friction angle of coarse-grained soil samples (η=3%) under different penetration erosion forces p0 is shown. The variation characteristics of cohesion c and the internal friction angle of coarse-grained soil samples under penetration erosion There is no obvious change. Its value is basically stable in the range of 55.7° to 61.23° before and after treatment, while the cohesion c shows a significant decrease. Compared with the untreated sample, the cohesion c value of the sample treated with 40kPa penetration erosion force p0 dropped from 40.9kPa to 16.8kPa, a decrease of 58.9%; and when p0 was increased to 70kPa, the c value dropped to 5.4kPa, a decrease of 86.8%. The reason is that under the penetration erosion treatment operation set in this experiment, the overall skeleton of the coarse-grained soil sample did not change significantly, and the overall bite and interlocking effect between the skeletons was not destroyed. Therefore, the internal friction angle of the coarse-grained soil sample before and after the scouring treatment was There is no significant change. However, under the penetration erosion, the fine particles on the upper part of the sample are lost, and the cementation of the fine particles is significantly weakened under the action of water, and the cohesion c between the particles is significantly reduced.

[0109] Figure 15-16 The peak shear strength of coarse-grained soil (σ1-σ3) for different p0 and different η is shown. max(Take σ3=30kPa as an example), internal friction angle And the influence of cohesion c. Among them, Fig.15 The shear peak strength diagram of coarse-grained soil samples with different fine particle contents η; Fig.16 A diagram showing the degree of peak strength attenuation of coarse-grained soil samples with different fine particle contents η.

[0110] like Fig.15 As shown in the figure, when the penetration erosion force p0 is constant, there is a critical threshold value η of fine particle content. critical , so that it is lower than η critical When the shear peak strength of the coarse-grained soil sample is max As the fine particle mass ratio increases, it increases; and above the critical threshold η critical When the shear peak strength of the coarse-grained soil sample is max It decreases with the increase of fine particle mass proportion.

[0111] Taking p0 = 60 kPa as an example, when the mass proportion of fine particles η increases from 15% to 45%, (σ1-σ3) max From 477.3kPa to 589.1kPa; when the mass proportion of fine particles η increases to 75%, (σ1-σ3) max It drops to 381.6 kPa. This shows that the strength of coarse-grained soil is closely related to the fine-grained mass ratio η. When the fine-grained mass ratio η is lower than the critical threshold η critical , appropriately increasing the fine-grained mass ratio η is helpful to improve the contact and interaction between angular gravels, increase the density and strength of coarse-grained soil, make the soil skeleton more stable, and strengthen its ability to resist penetration and erosion; on the contrary, when the fine-grained mass ratio η is higher than the critical threshold η critical When the soil is filled with fine particles, the contact and support between the soil skeletons are weakened, and its ability to resist penetration erosion is weakened.

[0112] like Fig.16 As shown in the figure, when the penetration erosion force p0 = 70 kPa, the peak stress intensity (σ1-σ3) of the coarse-grained soil samples with fine particle mass proportion η of 3%, 6%, 9%, 12% and 15% is max They decayed to 55.2%, 64.7%, 71.9%, 61.3% and 50.6% of those before the infiltration erosion treatment, respectively, indicating that with the increase of the fine particle mass proportion η, the ability of coarse-grained soil samples to resist infiltration erosion first increased and then decreased.

[0113] Fig.17 The effect of seepage erosion on the cohesion c of coarse-grained soils with different fine-grain content η is shown; Fig.18 The effect of seepage erosion on the internal friction angle of coarse-grained soil with different fine-grain content η is shown. impact.

[0114] Depend on Fig.17 It can be seen that before the penetration erosion treatment, as the mass proportion of fine particles η increases, the cohesion c of the coarse-grained soil sample continues to increase. Specifically, when the mass proportion of fine particles η increases from 3% to 15%, the cohesion c increases from 40.9kPa to 58.1kPa. The reason is that after the collapse of mudstone fine particles, the charge effect and water film effect between fine particles enhance the cohesion of the material, making the coarse-grained soil have higher viscosity and plasticity. As the penetration erosion proceeds, the cohesion c of the sample decreases linearly with the penetration erosion force p0, and its fitting determination coefficient R 2 All of them are over 0.98. The corresponding slopes (average attenuation rates) of the cohesion attenuation curves of coarse-grained soil samples with fine particle mass proportions η of 3%, 6%, 9%, 12% and 15% are 0.521, 0.495, 0.448, 0.516 and 0.607 respectively. The attenuation performance of cohesion c with the penetration erosion force p0 also verifies the critical threshold η critical The existence of characterizes the changing characteristics of the ability of coarse-grained soil to resist penetration erosion with different fine particle mass proportions η.

[0115] Depend on Fig.18 It can be seen that before the infiltration erosion treatment, as the fine particle mass proportion η increases, the initial internal friction angle of the coarse-grained soil sample When the mass proportion of fine particles increases from 3% to 15%, the initial internal friction angle From 55.7° to 29.1°. Fine particles have smaller particle size and higher plasticity. Increasing the mass proportion of fine particles η will reduce the friction between particles. Therefore, the internal friction angle As the penetration erosion progresses, the internal friction angle of the coarse-grained soil samples with fine particle mass proportions η of 3%, 6%, and 9% are There is no significant change, while the internal friction angle of the coarse-grained soil samples with fine particle mass ratio η of 12% and 15% As the penetration erosion force p0 increases, it continues to decrease. This is because, as mentioned above, below the critical threshold η critical , increasing the fine particle content helps to improve the stability of the coarse-grained soil skeleton and enhance its ability to resist penetration erosion; on the contrary, when it is higher than η critical When the soil is filled with fine particles, the filling effect weakens the stability of the coarse-grained soil skeleton and reduces its ability to resist penetration erosion.

[0116] Based on the above analysis, it can be seen that both the coarse-grained soil samples with and without seepage erosion treatment follow the linear Mohr-Coulomb strength failure criterion. Therefore, based on the Mohr-Coulomb strength criterion, a strength prediction model K of siliceous mudstone coarse-grained soil considering the seepage erosion effect is constructed. MC (η, p0).

[0117] See also Fig.19 , Fig.19 Represents the Mohr-Coulomb strength failure condition diagram, Fig.19 The envelope of the Mohr stress circle in is simplified to a straight line, which is expressed by the Coulomb equation as follows:

[0118]

[0119] In the formula, τ f is the shear stress of coarse-grained soil; σ represents the principal stress of coarse-grained soil; represents the internal friction angle of coarse-grained soil; c represents the cohesion of coarse-grained soil;

[0120] in:

[0121]

[0122] Because c. It is closely related to η and p0, so it can be regarded as a function of η and p0 c(η, p0), Combining the above formula, we can get the strength prediction model K MC The expression of (η, p0) is expressed as:

[0123]

[0124] The cohesion c decreases linearly with p0, and the initial cohesion c0 and the cohesion attenuation rate k c are all related to η, then c(η, p0) can be expressed as:

[0125] c(η,p0)=c0(η)-k c (η)p0;

[0126] Fig. 20 Presents c0 and k c The variation law with different η, such as Fig. 20 As shown, c0 can be regarded as a linear function increasing with η, k c It can be regarded as a quadratic function of η, and can be fitted from the curve:

[0127] c(η,p0)=36.2+2.092η-[0.0031985(η-9.15) 2 +0.46381]p0;

[0128] According to k c (η) fitting relationship, determine the critical threshold η critical It is 9.15%.

[0129] When it is lower than η critical As the penetration erosion progresses, the internal friction angle No significant change; when higher than ηcritical When the penetration erosion force p0 decreases linearly, and as it increases, the internal friction angle attenuation rate can be seen from the limited data. If there is no significant change, It can be expressed as:

[0130]

[0131] Fig.21 The initial internal friction angle and internal friction angle attenuation rate With the change of different fine particle mass proportion η, it is obvious that It can be regarded as a linear function that decreases with η. To ensure the continuity of the function, the transition function Sigmoid is used for smooth fitting. The fitting results are shown below:

[0132]

[0133] c(η, p0), Substitute the fitting results into K MC The expression of (η, p0) completes the strength prediction model K MC The construction of (η, p0), the model image is as follows Figure 22-Figure 25 As shown. Among them, Fig. 22 It represents the prediction model image under σ3 = 20 kPa; Fig.23 It represents the prediction model image under σ3 = 30 kPa; Fig.24 It represents the prediction model image under σ3 = 40 kPa; Fig.25 It shows the prediction model image under σ3=50kPa.

[0134] For the strength prediction of any coarse-grained soil, the fine particle mass proportion η and the seepage erosion force p0 are input, and the strength prediction value of the coarse-grained soil is output.

[0135] To test the prediction model K MC The accuracy of (η, p0) is compared with the relative errors between the predicted and measured values ​​of the corresponding peak intensity under different combinations of p0 and η (σ3 = 50 kPa) and different combinations of p0 and σ3 (η = 3%). Figure 26-Figure 27 ,in Fig.25 It represents the heat map of relative error between the predicted value and the measured value under σ3 = 50 kPa; Fig.26 It shows the relative error heat map between the predicted value and the measured value when η = 3%. Figure 26-27 It can be seen that except for the relative error between the predicted value and the measured value of the peak intensity corresponding to the working condition of η=3% and p0=60kPa, which is 16.3%~35.6% (the relative error between the predicted value and the measured value is 16.3%~35.6% Fig.18The abnormal data point in the working condition is removed, and the relative error between the predicted value and the measured value of the remaining working conditions is 1.1% to 14.9%. According to relevant regulations, the error between the soil strength prediction model and the true value is generally required to be less than 15%. Therefore, the siliceous mudstone coarse-grained soil strength prediction model K considering the seepage erosion effect proposed in this application MC (η, p0) has high accuracy and can meet the strength prediction requirements of coarse-grained soil.

[0136] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone, characterized in that: The steps include: Step S1, configuring a plurality of coarse-grained soil samples with different fine-grained mass proportions η, and performing penetration erosion treatment on the coarse-grained soil samples; Step S2, measuring the shear strength of the coarse-grained soil sample after the seepage erosion treatment at the real stress level, and constructing the stress-strain curve of the coarse-grained soil sample under different seepage erosion forces p0 and confining pressures σ3; Step S3, based on the stress-strain curve, analyze the effect of the fine particle mass ratio η and the penetration erosion force p0 on the shear strength σ1-σ3, cohesion c and internal friction angle of the coarse-grained soil sample. The strength failure criterion applicable to the coarse-grained soil sample was determined by fitting the linear function c(η, p0) related to the cohesion c and the fine particle mass ratio η, the penetration erosion force p0, and the internal friction angle Linear function related to fine particle mass ratio η and penetration erosion force p0 The linear function c(η, p0) and Substituting into the equation of the strength failure criterion, the strength prediction model K of siliceous mudstone coarse-grained soil considering the seepage erosion effect is obtained. MC (η, p0); Step S4, using the strength prediction model K MC (η, p0) predicts the strength of coarse-grained soil with a fine particle mass ratio of η under the action of penetration erosion force p0.

2. The method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone according to claim 1, characterized in that: The coarse-grained soil sample is prepared by using cohesionless angular gravel, sand particles and mudstone fine particles.

3. The method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone according to claim 1, characterized in that: In step S1, the penetration erosion process specifically includes the following steps: The coarse-grained soil sample is placed in a rubber membrane with openings at both ends, and the openings at both ends of the rubber membrane cover a permeable stone with a diameter of 50 mm, and the coarse-grained soil sample is tightly fitted to the permeable stone; The coarse-grained soil sample covered with the rubber film is placed into the large end of the funnel, and the small end of the funnel is connected to the variable frequency water pump through a pipeline; The variable frequency water pump is started to transport the water in the water tank to the funnel to flush the soil sample, simulating the penetration and erosion process of rainfall under natural conditions; The bottom of the coarse-grained soil sample is taken as the starting point for water seepage, and the treatment is carried out for 10 minutes. The treated coarse-grained soil sample is allowed to stand still and weighed in real time to ensure that the water content of the coarse-grained soil sample remains unchanged before and after flushing.

4. The method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone according to claim 1, characterized in that: The linear function c(η, p0) and Respectively expressed as: c(η,p0)=c0(η)-k c (h)p0; Where c0(η) represents the initial cohesion; represents the initial internal friction angle; k c (η), They represent the cohesion attenuation rate and the internal friction angle attenuation rate respectively, and both are functions related to the fine particle mass proportion η.

5. The method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone according to claim 4, characterized in that: c0(η)=A+Bη;k c (n)=a(n-n) critical ) 2 +b; Where A, B, a, and b are all fitting parameters; η critical is the critical value of the fine particle mass ratio η, which is determined by the turning point of the relationship curve between the fine particle mass ratio η and the cohesion c or the relationship between the fine particle mass ratio η and the internal friction angle The turning point of the relationship curve is obtained; In the formula, C, D, k are all fitting parameters.

6. The method for predicting the strength of coarse-grained soil considering seepage erosion and fine-grained content of mudstone according to claim 5, characterized in that: The intensity prediction model K MC (η, p0) is expressed as:

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