Method and device for calculating soil shear strength based on internal normal stiffness of particles

Abstract

The application discloses a kind of soil shear strength calculation method and device based on particle internal normal stiffness, method mainly includes: obtaining different particle normal contact stiffness corresponding shear strength parameter, obtain multiple data pairs, fitting to multiple data pairs, obtain the relationship curve of soil internal particle normal contact stiffness and shear strength parameter;The axial stress of the soil particle to be measured is obtained, the normal contact stiffness of the particle is determined, and the shear strength parameter of the soil to be measured is obtained according to the relationship curve of the soil internal particle normal contact stiffness and the shear strength parameter.The application can break through the limitation of conventional indoor soil test and soil mechanics macroscopic phenomenological research, and quickly and accurately calculate the loess shear strength parameter, to provide accurate and reliable data parameters for highway engineering high slope stability calculation.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, and more specifically to a method and apparatus for calculating the shear strength of soil based on the internal normal stiffness of particles. Background Technology

[0002] The shear strength of the soil directly affects the progress and effectiveness of engineering construction.

[0003] Currently, scholars both domestically and internationally have conducted extensive research on the influence of macroscopic factors such as moisture content, dry density, and freeze-thaw cycles on the shear strength of soil layers in different regions, and have achieved numerous research results. However, according to the introduction to granular mechanics, rockfill, debris flows, landslides, and soil masses in nature are all typical granular material systems, and many static and dynamic behaviors of granular systems cannot yet be well explained by general solid mechanics, fluid mechanics, and condensed matter physics theories.

[0004] Furthermore, in current technologies, shear strength parameters are generally obtained through indoor direct shear tests. However, since the shear strength parameters obtained from indoor direct shear tests differ significantly from the stress conditions in actual highway engineering slopes, the shear strength parameters obtained from indoor tests are not representative in loess slope stability calculations. As a result, most loess slope stability calculations still rely on engineering geological analogy to select shear strength parameters, thus rendering the parameters obtained from indoor direct shear tests of limited reference value.

[0005] Therefore, in order to address the above-mentioned shortcomings, this invention proposes a method and device for calculating the shear strength of soil based on the normal stiffness inside the particles, which is based on the particle flow simulation of the formation of soil shear bands, in order to break through the limitations of conventional indoor geotechnical tests and macroscopic phenomenological studies of soil mechanics. Summary of the Invention

[0006] In view of this, the present invention provides a method and apparatus for calculating the shear strength of soil based on the internal normal stiffness of particles, starting from the perspective of the true stress at the soil sampling depth. This not only solves the problem that there is no clear essential connection between the interaction of microscopic particles and the mechanical behavior of the macroscopic particle system, but also, compared with the indoor direct shear test, the calculation method disclosed in this application can quickly and accurately calculate the shear strength parameters of loess, providing accurate and reliable data parameters for the stability calculation of high slopes in highway engineering.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for calculating the shear strength of soil based on the internal normal stiffness of particles, comprising:

[0009] Obtain the shear strength parameters corresponding to different particle normal contact stiffness, and obtain multiple data pairs. Fit the multiple data pairs to obtain the relationship curve between the particle normal contact stiffness and the shear strength parameters inside the soil.

[0010] The axial stress of the soil particles to be tested is obtained, the normal contact stiffness of the particles is determined, and the shear strength parameters of the soil to be tested are obtained based on the relationship curve between the normal contact stiffness of the particles inside the soil and the shear strength parameters.

[0011] Preferably, the normal contact stiffness is determined according to the following formula:

[0012]

[0013] In the formula, k n σ1 is the normal contact stiffness of the particle; σ3 is the lateral stress; α is the angle between the long axis of the particle and the horizontal direction; β is the angle between the shear stress surface and L is the long axis of the particle.

[0014] Preferably, when the soil is aeolian loess, α is 90°, and when the soil is alluvial loess, α is 0°.

[0015] Preferably, the axial stress is obtained by the following formula:

[0016] σ1=γh

[0017] In the formula, γ is the soil mass weight, and h is the soil sampling depth.

[0018] Preferably, the lateral stress is obtained by the following formula:

[0019]

[0020] In the formula, K c The consolidation ratio is denoted as , where . The internal friction angle of the soil.

[0021] Preferably, the shear strength parameters include soil cohesion and internal friction angle.

[0022] On the other hand, this application also discloses a soil shear strength calculation device based on the internal normal stiffness of particles, comprising:

[0023] The soil internal stiffness acquisition unit is used to obtain the normal contact stiffness of soil particles based on the soil sampling depth and the stress parameters of soil particles.

[0024] The soil shear strength parameter acquisition unit stores the relationship curve between the normal contact stiffness of soil particles and the shear strength parameter as described above. It is used to receive the normal contact stiffness of soil particles and obtain the shear strength parameter of the soil based on the curve.

[0025] Preferably, the device also includes a parameter setting unit for setting the stress parameters of the soil particles according to the soil type.

[0026] As can be seen from the above technical solution, this invention discloses a method and apparatus for calculating the shear strength of soil based on the internal normal stiffness of particles. Compared with the prior art, this invention establishes a mathematical relationship between the normal contact stiffness of particles and the macro- and micro-parameters of the soil based on a force model of the failure point of two particles within the soil. A direct shear test model of the soil is established using particle flow numerical software, and different normal contact stiffnesses are assigned to the soil particles to obtain their corresponding shear strength parameters, thus establishing a mathematical relationship between the internal stiffness of the soil and the shear strength parameters.

[0027] This invention breaks through the limitations of conventional indoor geotechnical tests and macroscopic phenomenological studies of soil mechanics. Based on the macroscopic and microscopic aspects of soil, it analyzes the mechanical behavior between particles inside loess and establishes a mathematical relationship between the internal stiffness of loess and macroscopic stress. In addition, this application also constructs a curve showing the relationship between the internal stiffness of soil and shear strength parameters.

[0028] Compared with indoor direct shear tests, the calculation method disclosed in this application can quickly and accurately calculate the shear strength parameters of loess, providing accurate and reliable data parameters for the stability calculation of high slopes in highway engineering. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a flowchart of the soil shear strength calculation method based on the internal normal stiffness of particles according to the present invention.

[0031] Figure 2 This is a schematic diagram of the forces acting on the contact points of soil particles according to the present invention.

[0032] Figure 3 The curves showing the relationship between shear displacement and shear stress of loess samples with soil particles of different stiffness are shown in this invention.

[0033] Figure 4 This is a graph showing the relationship between particle stiffness and internal friction angle in this invention.

[0034] Figure 5 This is a graph showing the relationship between particle stiffness and cohesion in this invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention addresses the lack of a clear essential connection between microscopic particle interactions and macroscopic granular system mechanical behavior in soil, as well as the unclear nature of the force chain structure and its complex spatiotemporal evolution at the microscopic scale. From a microscopic perspective, it proposes a method and apparatus for calculating soil shear strength based on the internal normal stiffness of particles. This invention provides a novel method for calculating shear strength parameters based on soil microstructure parameters. Using the soil shear strength calculation method and apparatus disclosed in this invention, the cohesion and internal friction angle of soil can be calculated quickly and accurately.

[0037] The method for calculating the shear strength of soil in this invention, as follows: Figure 1 As shown, it includes:

[0038] Obtain the shear strength parameters corresponding to different particle normal contact stiffness, and obtain multiple data pairs. Fit the multiple data pairs to obtain the relationship curve between the particle normal contact stiffness and the shear strength parameters inside the soil.

[0039] The axial stress of the soil particles to be tested is obtained, the normal contact stiffness of the particles is determined, and the shear strength parameters of the soil to be tested are obtained based on the relationship curve between the normal contact stiffness of the particles inside the soil and the shear strength parameters.

[0040] Specifically, this invention establishes a particle flow direct shear model, assigns different normal stiffnesses to soil particles, and initiates direct shear test simulations under different confining pressures to obtain the aforementioned data pairs; simultaneously, based on the force analysis of the contact point between two soil particles, a mathematical relationship is established through the force equilibrium condition, thereby calculating the normal contact stiffness of the particles.

[0041] In this application, the normal contact stiffness of the particles is determined as follows:

[0042]

[0043] In the formula, k nσ1 is the normal contact stiffness of the particle; σ3 is the lateral stress; α is the angle between the long axis of the particle and the horizontal direction; β is the angle between the shear stress surface and L is the long axis of the particle.

[0044] In one embodiment, α is 90° when the soil is aeolian loess and 0° when the soil is alluvial loess.

[0045] Furthermore, the axial stress is obtained through the following formula:

[0046] σ1=γh

[0047] In the formula, γ is the soil mass weight, and h is the soil sampling depth.

[0048] Lateral stress is obtained using the following formula:

[0049]

[0050] In the formula, K c The consolidation ratio is denoted as , where . This is the internal friction angle of the soil, which is generally a known empirical value.

[0051] This invention establishes a mathematical relationship between the internal stiffness and macroscopic stress of loess based on macroscopic and microscopic stress analysis of the mechanical behavior between particles within the loess mass. The specific analysis process is as follows:

[0052] The stress at the failure point of the two particles was analyzed. Figure 2 This is a schematic diagram of the stress at the contact point of soil particles according to the present invention. The major axis and minor axis of the two particles are L and L′, respectively, with the major axis L > L′. The stress at point O is σ′1 = σ1L cosα and σ′3 = σ3L sinα, where σ1 is the axial stress, σ3 is the lateral stress, and α is the angle of the major axis L of the particle.

[0053] Let the normal stress and shear stress at point O be σ and f, respectively, α be the angle of the major axis L of the particle, and β be the angle between the shear stress surfaces. The shear surface at the failure point O is the plane where f is located in the figure, where f is the shear stress and σ is the normal stress at point O.

[0054] Furthermore, according to the equilibrium condition of forces, we can obtain:

[0055] σ-σ′1cosβ+σ′3sinβ=0

[0056] Substituting σ′1=σ1L cosα and σ′3=σ3L sinα into the above equation, we can obtain...

[0057]

[0058]

[0059] Furthermore, the formula for calculating stiffness is:

[0060]

[0061] Where, k n The normal contact stiffness of the particles; A = Lb; A is the particle contact area; b is the particle contact width, b is taken as unit 1.

[0062] In conclusion:

[0063]

[0064] The present invention further obtains shear strength parameters corresponding to different particle normal contact stiffness, obtains multiple data pairs, fits multiple data pairs, and obtains the relationship curve between particle normal contact stiffness and shear strength parameters inside the soil; wherein, the shear strength parameters include cohesion and internal friction angle.

[0065] In this embodiment, the stress analysis of the contact point between two soil particles is first performed, and the normal contact stiffness of different particles is obtained according to the established mathematical relationship. At the same time, the direct shear test model under different stiffness is established using particle flow numerical simulation software, and the shear strength parameter values ​​corresponding to different normal stiffness are calculated.

[0066] Preferably, this application prioritizes the study of the relationship between shear displacement and shear stress of loess samples under different normal contact stiffnesses, as shown in the curves. Figure 3 As shown, this study aims to verify the feasibility of exploring the relationship between normal contact stiffness, cohesion, and internal friction angle.

[0067] Depend on Figure 3 It is known that there is a certain relationship between soil particle stiffness and soil elastic modulus. When other microscopic parameters are constant, the greater the particle stiffness, the higher the shear strength of loess. With increasing shear displacement, within the elastic range, stiffness has a significant impact on the shear strength of loess; the shear strength increases with increasing stiffness. At the macroscopic level, this manifests as a greater initial elastic modulus corresponding to greater stiffness.

[0068] The normal contact stiffness of loess particles reflects the macroscopic properties of loess. Particles with higher shear strength exhibit dilatation in direct shear tests, while those with lower shear strength exhibit shrinkage. Therefore, the stiffness of loess primarily affects the rate of increase in its shear strength and the magnitude of its peak strength.

[0069] Therefore, by assigning different normal contact stiffness values ​​to soil particles, this invention further investigates the influence of normal contact stiffness on the cohesion and internal friction angle of the peak strength of the soil. In one embodiment, the soil cohesion and internal friction angle under different stiffnesses are shown in Table 1:

[0070] Table 1. Cohesion and internal friction angle of soil under different particle stiffnesses

[0071]

[0072] The fitted curve is as follows Figure 4 , Figure 5 As shown;

[0073] The shear strength calculation method provided by this invention can be used for engineering calculations and numerical simulations. Taking the loess soils of Northwest China as an example, for typical loess soils, β... Around 24°, therefore K c The value is 1.69. Statistical analysis of the long axis of loess particles in the microstructure of Northwest China was performed, with the long axis value taken as 15 μm. Based on the stratification of the soil samples, α was taken as 90° for aeolian loess and 0° for alluvial loess. Loess density and sampling depth were determined according to actual conditions. The axial stress σ1 and lateral stress σ3 of the loess at the actual depth were calculated. The internal stiffness of the loess was then obtained, and then... Figure 4 , Figure 5 The fitted curve was used to further determine the shear strength parameters of the loess.

[0074]

[0075] c = -32.705(k) n ) 2 +27.531k n +11.357

[0076] When calculating shear strength parameters based on the internal stiffness of loess in subsequent highway engineering slopes, this invention first calculates the internal stiffness of the soil based on the actual stress value at the soil sampling depth on site, and then directly calculates the cohesion and internal friction angle of the loess based on the relationship established by numerical simulation.

[0077] On the other hand, this invention discloses a soil shear strength calculation device based on the internal normal stiffness of particles, the device comprising:

[0078] The soil internal stiffness acquisition unit stores the calculation formula for normal contact stiffness, which is used to obtain the normal contact stiffness of soil particles based on the soil sampling depth and the stress parameters of soil particles.

[0079] The soil shear strength parameter acquisition unit stores the relationship curve between the normal contact stiffness of soil particles and the shear strength parameter as described above. It is used to receive the normal contact stiffness of soil particles and obtain the shear strength parameter of the soil according to the curve.

[0080] In addition, the device also includes a parameter setting unit for setting the stress parameters of the soil particles, including the angle α between the particle's long axis and the horizontal direction, the angle β between the shear stress surfaces, the particle's long axis L, and the soil's internal friction angle.

[0081] Furthermore, the soil density can be set, and during testing, only the soil depth needs to be entered to obtain the soil shear strength parameters.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0083] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for calculating the shear strength of soil based on the internal normal stiffness of particles, characterized in that, include: Obtain the shear strength parameters corresponding to different particle normal contact stiffness, and obtain multiple data pairs. Fit the multiple data pairs to obtain the relationship curve between the particle normal contact stiffness and the shear strength parameters inside the soil. The axial stress of the soil particles to be tested is obtained, and the normal contact stiffness of the soil particles to be tested is determined. In the formula, For particle normal contact stiffness; For axial stress; α is the lateral stress; α is the angle between the long axis of the particle and the horizontal direction; β is the angle between the shear stress surface and L is the long axis of the particle. The axial stress is obtained by the following formula: In the formula, denoted as soil mass weight, and h as soil sampling depth; The lateral stress is obtained by the following formula: In the formula, The consolidation ratio is denoted as , where . , The internal friction angle of the soil; The shear strength parameters of the soil under test are obtained based on the relationship curve between the normal contact stiffness of the soil particles and the shear strength parameters.

2. The method for calculating the shear strength of soil based on the internal normal stiffness of particles according to claim 1, characterized in that, When the soil is aeolian loess, α is 90°; when the soil is alluvial loess, α is 0°.

3. The method for calculating the shear strength of soil based on the internal normal stiffness of particles according to claim 1, characterized in that, The shear strength parameters include soil cohesion and internal friction angle.

4. A soil shear strength calculation device based on the internal normal stiffness of particles, characterized in that, include: The soil internal stiffness acquisition unit is used to obtain the normal contact stiffness of soil particles based on the sampling depth of soil particles and the stress parameters between soil particles. The soil shear strength parameter acquisition unit stores the relationship curve between the normal contact stiffness of the soil particles and the shear strength parameter as described in any of claims 1-3, and is used to receive the normal contact stiffness of the soil particles and obtain the shear strength parameter of the soil according to the relationship curve.

5. The soil shear strength calculation device based on the internal normal stiffness of particles according to claim 4, characterized in that, It also includes a parameter setting unit, which is used to set the stress parameters between soil particles according to the soil type.

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