Impact penetration sounding dynamic response characteristic analysis method for soil-rock mixture

Abstract

The invention provides an impact penetration sounding dynamic response characteristic analysis method for an earth-rock aggregate. The method specifically comprises the following steps: (1) establishing an earth-rock aggregate discrete element model; (2) accurately simulating the mechanical behavior of the soil body by adopting a bond rolling resistance linear contact model; and (3) carrying out dynamic mechanical response analysis on the impact penetration process by using the constructed impact penetration discrete element model. The device is reasonable in conception, can accurately reflect the mechanical response characteristics of the soil-rock mixture in the impact penetration process, provides an effective analysis tool for the impact penetration research of the soil-rock mixture, and is suitable for popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of remote surveying of ground mechanics, and in particular to a method for analyzing dynamic response characteristics of impact penetration probing of a soil-rock mixture. Background Art

[0002] Currently, the main technical means for remote surveying of ground mechanics include space-based remote sensing and airborne geophysical prospecting. Space-based remote sensing is an indirect inversion method, capable of only obtaining information on surface vegetation and its properties, geological structure, and ground features. It also suffers from low spatial resolution, low reliability, and limited real-time performance. Airborne geophysical prospecting, primarily for geological structure delineation and material property identification, also suffers from low vertical spatial resolution, low reliability, and limited real-time performance. Both of these technical methods are non-contact, in-situ surveys, capable only of inverting soil types and properties and unable to quickly and accurately obtain ground mechanics information.

[0003] To address these challenges, the Institute of Mechanics of the Chinese Academy of Sciences has innovatively proposed impact penetration probing, a technique designed to overcome the technical bottleneck of remote, rapid, and in-situ geomechanical surveys. Its fundamental physical concept is inspired by the proverb "throwing a stone to test the water." The basic principle is to use an unmanned aerial vehicle (UAV) as a carrier to generate penetration kinetic energy under the influence of gravity, and then interpret soil profile characteristics and geomechanical parameters based on the penetration resistance.

[0004] However, in actual applications, it is found that when there are stones or hard foreign objects of a certain size on the surface or in shallow soil, the dynamic response of the impact penetration probe will be severely disturbed, resulting in significant fluctuations in the measurement data, which in turn affects the reliability of the impact penetration probe.

[0005] Existing technical solutions cannot accurately distinguish between true soil characteristic signals and rock disturbance signals when the penetrometer strikes hard foreign objects such as rocks, causing data anomalies. This restricts the application of impact penetration testing in complex geological environments. Therefore, it is urgent to develop a method that can effectively analyze the dynamic response of impact penetration testing of soil-rock mixtures, providing an effective analytical tool for impact penetration research of soil-rock mixtures. Summary of the Invention

[0006] In response to the technical problems existing in the above-mentioned background technology, the present invention proposes a method for analyzing the dynamic response characteristics of impact penetration probing of soil-rock mixtures. The method has a reasonable concept and can accurately reflect the mechanical response characteristics of soil-rock mixtures during the impact penetration process, providing an effective analysis tool for the impact penetration research of soil-rock mixtures, and is suitable for promotion and application.

[0007] To solve the above technical problems, the present invention provides a method for analyzing the dynamic response characteristics of impact penetration testing of a soil-rock mixture, which specifically includes the following steps:

[0008] (1) Establishing a discrete element model of soil-rock mixture

[0009] (1.1) Constructing a rock-free soil impact penetration test model

[0010] A benchmark model containing only soil particles is established within the discrete element calculation domain Ω to ensure computational efficiency and analytical accuracy.

[0011] (1.2) Construct an impact penetration test model for soil-rock mixture;

[0012] (2) Contact model

[0013] A linear contact model of bond rolling resistance is uniformly introduced at the soil-soil contact interface to accurately characterize the stress and failure behavior of sandy soil particles.

[0014] (3) Analysis results

[0015] The impact penetration test model of the soil-rock mixture mentioned above is used to analyze the dynamic mechanical response of the impact penetration process, where the governing equation is as follows:

[0016]

[0017] Among them, m i ,I i are the mass and moment of inertia of the unit respectively; F ij ,M ij are the ARR-Linear contact force and moment, respectively.

[0018] The method for analyzing the dynamic response characteristics of impact penetration probing of a soil-rock mixture, wherein the specific process of step (1.1) is as follows:

[0019] (1.1.1) Domain Partitioning

[0020] Divide the discrete element computational domain Ω into N concentric shells The thickness of each layer can be taken as Δr = R / N, where R is the width of the discrete element calculation domain;

[0021] (1.1.2) Scaling factor setting

[0022] Assign a particle scaling factor α to the i-th layer i (i=1:N), satisfying:

[0023]

[0024] The typical value is from the central high resolution area α1=6 to the far field coarse resolution area α N =6;

[0025] (1.1.3) Particle size mapping formula

[0026] The reference particle size d is taken from the measured particle size distribution of the soil ref implement:

[0027] d i =α i d ref ,i=1:N;

[0028] (1.1.4) Sample loading

[0029] The random sedimentation-gravity consolidation algorithm is used to fill the partitioned particles and iterate through explicit dynamic relaxation to:

[0030]

[0031] The quasi-static initial stress field is obtained, which is consistent with the porosity measured indoors;

[0032] The rock-free soil DEM impact penetration model constructed through the above steps (1.1.1)-(1.1.4) takes into account the contact analysis accuracy of the central area and the overall calculation scale, laying the foundation for the subsequent introduction of irregular rocks and dynamic penetration analysis.

[0033] The method for analyzing the dynamic response characteristics of impact penetration probing of a soil-rock mixture, wherein the process of step (1.2) is as follows:

[0034] (1.2.1) Stone geometry generation

[0035] Several points are randomly generated on the surface of the ellipsoid using the spherical coordinate system, as follows:

[0036] For a given ellipsoid primitive, the position of any point on the ellipsoid surface in the spherical coordinate system can be determined by five parameters R1, R2, R3, θ, To jointly determine; when constructing a polyhedron with N vertices based on an ellipsoid primitive, the vertices of the polyhedron are divided into two parts, which are random points independently selected from the upper and lower halves of the ellipsoid primitive surface; assuming that the number of vertices selected from the upper half of the ellipsoid primitive surface is M, then the θ of these random points i and They are:

[0037]

[0038] Where η1 and η2 are two independent random numbers uniformly distributed in [0, 1], and δ is a variable; the remaining polyhedron vertices are independently and randomly selected from the lower half of the ellipsoidal primitive surface and are determined similarly according to the above formula; in the Cartesian coordinate system, the coordinates of the polyhedron vertices (x i ,y i ,z i ) is expressed as:

[0039]

[0040] Where (x0, y0, z0) is the center coordinate of the ellipsoid primitive, R1, R2, and R3 are the lengths of the three semi-major axes of the ellipsoid primitive respectively; then, call Calculate the geometric convex hull and use the trimesh library to export the STL mesh stone_k.stl, which is the shell of a single irregular stone;

[0041] (1.2.2) Domain merging and initialization

[0042] (1.2.2.1) Domain Overlay

[0043] Ω=Ω soil ∪Ω rock ;

[0044] Automatically adjust the initial position of the stone and adjacent soil particles to make the relative overlap δ0≤0.05d min ;

[0045] (1.2.2.2) Gravity consolidation

[0046] Turn on gravity g, and relax the explicit dynamics to A discrete element model of soil-rock mixture with the same porosity as the indoor porosity is obtained.

[0047] The method for analyzing the dynamic response characteristics of impact penetration probing of a soil-rock mixture, wherein the numerical solution process and control equations for the stress and failure behavior of sandy soil particles in step (2) are as follows:

[0048] (2.1) Contact determination

[0049] The radius expansion method is used to detect whether two particles i and j overlap, and the normal overlap is obtained:

[0050] δ n =R i +R j -||x ij ||;

[0051] (2.2) Normal force calculation

[0052] F n =k n δ n ;

[0053] Among them, k n is the normal contact stiffness; if δ n <0, contact failure;

[0054] (2.3) Tangential force increment update

[0055]

[0056] Where Δu s is the tangential displacement increment of the current step, k s is the tangential stiffness;

[0057] (2.4) Coulomb correction

[0058]

[0059] Where μ is the coefficient of kinetic friction between particles;

[0060] (2.5) Rolling resistance torque

[0061]

[0062] Among them, k r is the rolling resistance stiffness, Δθ r is the relative roll angle increment of this step, η is the rolling resistance coefficient, R eq is the equivalent radius;

[0063] (2.6) Bond strength criterion

[0064] If satisfied or It is considered as contact fracture; thereafter, the contact switches to the "friction + rolling resistance" mode and no longer bears tensile stress.

[0065] The method for analyzing the dynamic response characteristics of impact penetration probing of a soil-rock mixture, wherein the specific process of the dynamic mechanical response analysis of the impact penetration process in step (3) is as follows:

[0066] (3.1) Motion state of particles

[0067] Track the displacement, velocity, and acceleration of particles, analyze their deformation and motion patterns, and reveal the dynamic response characteristics of the soil-rock mixture, as follows:

[0068] During the impact simulation phase, the displacement u of particle k k (t), speed v k (t) and acceleration a k (t) is automatically updated by the discrete element solver in each integration step Δt; specifically, the discrete element solver first calculates the resultant force F at the previous moment. k Solve for the instantaneous acceleration a k =F k / m k , and then complete the kinematic recursion:

[0069]

[0070] (3.2) Penetration resistance

[0071] The total contact pairs formed by the penetrometer and the surrounding particles are recorded as Γ(t); the discrete element solver automatically outputs the normal force F of each contact element at each integration step. {n,j} (t) and tangential friction F {s,j} (t); by real-time all normal forces F {n,j} (t) and tangential friction F {s,j} (t) Accumulate along the penetration axis z direction to obtain the instantaneous vertical reaction force F z (t), and simultaneously record the tip displacement s(t); the two can be paired to draw the resistance-displacement curve F z (s); peak value F of the curve z,max Represents the ultimate reaction force generated by the soil-rock mixture on the probe during the penetration process; the peak F z,max Normalized to the equivalent vertical bearing capacity according to the cross-sectional area A of the penetrometer probe:

[0072]

[0073] Considering the amplification of the limit value by the impact inertia, the dynamic load correction factor η=1-k is introduced v V0 / V ref , where k v is the empirical coefficient, V0 is the initial falling velocity of the penetrometer, and the corrected static bearing capacity is:

[0074]

[0075] This provides a prediction for the bearing capacity of the soil.

[0076] By adopting the above technical solution, the present invention has the following beneficial effects:

[0077] The method for analyzing the dynamic response characteristics of impact penetration probing of soil-rock mixtures of the present invention is well conceived. By constructing an accurate discrete element model of the soil-rock mixture, selecting appropriate microscopic contact models and parameters, and performing dynamic mechanical response analysis, it can accurately reflect the mechanical response characteristics of the soil-rock mixture during the impact penetration process, and provide an effective analysis tool for the impact penetration research of soil-rock mixtures.

[0078] The present invention can not only quantitatively reproduce the microscopic response mechanism of soil-rock interaction under different grading and rock content conditions, but also can capture the disturbance characteristics of the resistance curve caused by eccentric collision, rotation and local arch effect of stones in real time during the penetration process, thereby realizing a rapid and non-empirical inversion of the actual bearing capacity and stiffness of the soil layer. In addition, the present invention takes into account both high-resolution contact analysis in the probe neighborhood and computational efficiency in the far field, significantly reducing the dependence of traditional uniform models on computing power; at the same time, by introducing a dynamic load correction coefficient, the inertia effect can be effectively stripped off, and a bearing capacity index that can be directly used for engineering design can be obtained. Compared with existing technologies that rely on simplified formulas or experimental regression, the present invention has the significant advantages of clear mechanism, clear physical meaning of parameters, and applicability to complex working conditions such as a wide range of stone sizes and shapes. It provides an efficient and portable numerical analysis tool for rapid in-situ evaluation of the bearing capacity of soil-rock mixed strata. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0080] Figure 1 Schematic diagram of the construction of an impact penetration test model for a rock-free soil mass involved in the dynamic response characteristic analysis method of impact penetration test for a soil-rock mixture according to the present invention;

[0081] Figure 2 A flow chart for constructing an impact penetration test model of a soil-rock mixture involved in the dynamic response characteristic analysis method of the impact penetration test of a soil-rock mixture according to the present invention;

[0082] Figure 3 Schematic diagram of the bond rolling resistance linear contact model involved in the method for analyzing the dynamic response characteristics of impact penetration probing of a soil-rock mixture according to the present invention;

[0083] Figure 4 It is a schematic diagram of the motion state of particles and the acceleration comparison of the penetrometer involved in the dynamic response characteristic analysis method of impact penetration probing of soil-rock mixture of the present invention. DETAILED DESCRIPTION

[0084] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0085] The present invention will be further explained below with reference to specific embodiments.

[0086] The present embodiment provides a method for analyzing the dynamic response characteristics of impact penetration testing of a soil-rock mixture, specifically comprising the following steps:

[0087] S100, establish a discrete element model of soil-rock mixture

[0088] The present invention adopts a particle refinement method to solve the contradiction between computational efficiency and accuracy in traditional discrete element simulation. Specifically, a progressive particle scaling factor is used in the simulation domain, so that the soil particle size near the penetration center is small, and the particle size away from the penetration center gradually increases, such as Figure 1 As shown (the model is divided into five layers along the radial direction, with typical radius intervals of 0-0.10m, 0.10-0.20m, 0.20-0.30m, 0.30-0.50m and the outermost area; each shell is assigned a particle scaling factor ni (i=1…5), with values ​​of 6, 10, 15, 22 and 30, and the corresponding average particle diameter increases from the inside to the outside, distinguished by five colors: red, magenta, orange, blue and dark red in the figure). This particle size distribution helps to ensure accurate simulation during the penetration process while avoiding the computational burden of large particle numbers. Through this progressive particle size distribution, the calculation scale and accuracy can be effectively balanced, and the method avoids the migration of small particles to large particle layers. For example, the particle scaling factor is 6 at the penetration center and 30 at the boundary, thereby optimizing the computational efficiency and accuracy of the model.

[0089] In order to accurately simulate the impact penetration of soil-rock mixture, it is necessary to first construct a discrete element model of the soil-rock mixture. The specific process is as follows:

[0090] S110, Construction of impact penetration test model for rock-free soil

[0091] To ensure computational efficiency and analytical accuracy, the present invention first establishes a benchmark model containing only soil particles within the discrete element computational domain Ω. The specific process is as follows:

[0092] S111, Domain Partitioning

[0093] Divide Ω into N concentric shells The thickness of each layer can be taken as Δr = R / N, where R is the width of the discrete element calculation domain.

[0094] S112. Scaling factor setting

[0095] Assign a particle scaling factor α to the i-th layer i (i=1:N), satisfying:

[0096]

[0097] Typical values ​​are α1 = 6 (penetrating into the central high resolution area) to α N =6 (far field coarse resolution area).

[0098] S113, Particle size mapping formula

[0099] For reference particle size d ref (taken from the measured particle size distribution of the soil) Execute:

[0100] d i =α i d ref ,i=1:N;

[0101] S114, Sample Loading

[0102] The random sedimentation-gravity consolidation algorithm is used to fill the partitioned particles and iterate through explicit dynamic relaxation to

[0103]

[0104] The quasi-static initial stress field is obtained, which is consistent with the porosity measured indoors.

[0105] After the above steps, the constructed rock-free soil DEM impact penetration model takes into account both the contact analysis accuracy of the central area and the overall calculation scale, laying the foundation for the subsequent introduction of irregular rocks and dynamic penetration analysis.

[0106] S120, Construction of impact penetration test model for soil-rock mixture

[0107] To improve the realism of the simulation, especially the shape simulation of irregular rocks within the soil, this paper adopts a method based on ellipsoid primitives. In this method, a number of points are randomly generated on the surface of the ellipsoid using a spherical coordinate system. These points are used to construct irregular polyhedrons to represent the rocks in the soil. Afterwards, a clump model template is created using PFC3D software. These irregular rocks are added to the soil particle model, thus forming a mixed model containing irregular rocks and soil particles, as shown in the following figure. Figure 2 As shown; in this way, the physical properties of the soil-rock mixture can be reproduced more realistically and the accuracy of the simulation can be improved.

[0108] The specific process of the above step S120 is as follows:

[0109] S121. Stone geometry generation

[0110] Several points are randomly generated on the surface of the ellipsoid using the spherical coordinate system (by calling the Monte-Carlo sampling algorithm in the Python environment), as follows:

[0111] For a given ellipsoid primitive, the position of any point on the ellipsoid surface in the spherical coordinate system can be determined by five parameters (R1, R2, R3, θ, ) are jointly determined. When constructing a polyhedron with N vertices based on an ellipsoid primitive, the vertices of the polyhedron are divided into two parts, which are random points independently selected from the upper and lower halves of the ellipsoid primitive surface. Assuming that the number of vertices selected from the upper half of the ellipsoid primitive surface is M, then the θ of these random points i

[0112] and They are:

[0113]

[0114] Where η1 and η2 are two independent random numbers uniformly distributed in [0, 1], and δ is a variable whose value is usually 0.3. The remaining polyhedron vertices are independently and randomly selected from the lower half of the ellipsoidal primitive surface and are determined similarly according to the above formula. In the Cartesian coordinate system, the coordinates of the polyhedron vertices (x i ,y i ,z i ) can be expressed as:

[0115]

[0116] Where (x0, y0, z0) is the center coordinate of the ellipsoid primitive, R1, R2, R3 are the lengths of the three semi-major axes of the ellipsoid primitive; then, call Compute the geometric convex hull and use the trimesh library to export the STL mesh stone_k.stl, which represents the outer shell of a single irregular stone. PFC3D comes with an STL→clump conversion command.

[0117] S122, Domain Merging and Initialization

[0118] S1221, Domain Overlay

[0119] Ω=Ω soil ∪Ω rock ;

[0120] Automatically adjust the initial position of the stone and adjacent soil particles to make the relative overlap δ0≤0.05d min ;

[0121] S1222, Gravity Consolidation

[0122] Turn on gravity g, and relax the explicit dynamics to A discrete element model of soil-rock mixture with the same porosity as the indoor porosity is obtained.

[0123] S200, contact model

[0124] In order to accurately simulate the mechanical behavior of soil, the present invention adopts the bond rolling resistance linear contact model, such as Figure 3 As shown ( Figure 3 The left side of the figure shows the spatial contact of two spherical particles (Particle 1 and Particle 2) in the discrete element model; the upper right corner shows the corresponding linear contact model of bonding rolling resistance, where: k n , β n : normal spring-damper element, describing the recoverable compression-rebound process generated by particle overlap; k s , β s 、μ s : Tangential spring-damper and Coulomb friction elements to control shear slip and energy dissipation; μ r : Rolling friction element, which limits the additional torque required for the particle to rotate around the contact point and reflects the particle angle effect and surface roughness; F a : The adsorption force element generated by the capillary water film varies with the interparticle distance d (see the curve relationship in the lower right figure). This model adds rolling resistance and cohesion parameters between particles to the traditional linear contact model. This allows it to consider the morphology of soil particles, the capillary water action between particles, and the bonding effect of clay minerals, better reproducing the actual mechanical behavior of unsaturated soils during impact penetration.

[0125] In order to accurately characterize the stress and failure behavior of sandy soil particles in a discrete element environment, the present invention uniformly introduces a linear contact model of adhesive rolling resistance at the "soil-soil" contact interface. The numerical solution process and control equations are as follows:

[0126] S210, contact determination

[0127] The radius expansion method is used to detect whether two particles i and j overlap, and the normal overlap is obtained:

[0128] δ n =R i +R j -||x ij ||;

[0129] S220, Normal force calculation

[0130] F n =k n δ n ;

[0131] where k n is the normal contact stiffness; if δ n <0, contact failure.

[0132] S230, tangential force increment update

[0133]

[0134] Δu s is the tangential displacement increment of the current step, k s is the tangential stiffness.

[0135] S240, Coulomb correction

[0136]

[0137] μ is the coefficient of kinetic friction between particles.

[0138] S250, rolling resistance torque

[0139]

[0140] where k r is the rolling resistance stiffness, Δθ r is the relative roll angle increment of this step, η is the rolling resistance coefficient, R eq is the equivalent radius.

[0141] S260, Bond Strength Criteria

[0142] If satisfied

[0143] or

[0144] It is considered as contact fracture; thereafter, the contact switches to the "friction + rolling resistance" mode and no longer bears tensile stress.

[0145] S300, analysis results

[0146] The impact penetration test model of the soil-rock mixture mentioned above is used to analyze the dynamic mechanical response of the impact penetration process, where the governing equation is as follows:

[0147]

[0148] Among them, m i ,I i Unit mass and moment of inertia; F ij ,M ij The ARR-Linear contact forces and moments.

[0149] like Figure 4 As shown ( Figure 4 The left side shows the particle displacement cloud map (upper row) and instantaneous velocity cloud map (lower row) when the penetration depth Z is 0.1m, 0.2m, 0.3m and 0.5m respectively; the color scale displacement range is 0.005-0.05m, and the velocity range is 0.5-5.0m / s; Figure 4The right side plots the curve of the penetrometer axial acceleration versus penetration depth). Through computational analysis, the dynamic response characteristics of the soil-rock mixture during impact penetration can be comprehensively evaluated.

[0150] Among them, the specific process of dynamic mechanical response analysis during impact penetration is as follows:

[0151] S310, the motion state of particles

[0152] Track the displacement, velocity, and acceleration of particles, analyze their deformation and motion patterns, and reveal the dynamic response characteristics of the soil-rock mixture, as follows:

[0153] During the impact simulation phase, the displacement u of particle k k (t), speed v k (t) and acceleration a k (t) is automatically updated by the discrete element solver in each integration step Δt. Specifically, the solver first calculates the resultant force F at the previous moment. k Solve for the instantaneous acceleration a k =F k / m k , and then complete the kinematic recursion:

[0154]

[0155] Therefore, the present invention can continuously track the entire process of "elastic accumulation → particle rearrangement" at a mesoscopic scale, thereby truly reflecting the dynamic response mechanism of the soil-rock mixture under impact loading.

[0156] S320, penetration resistance

[0157] During the penetration process, all contact pairs formed between the penetrometer and the surrounding particles are recorded as Γ(t). The discrete element solver automatically outputs the normal force F of each contact element at each integration step. {n,j} (t) and tangential friction F {s,j} (t). The present invention realizes real-time {n,j} (t) and F {s,j} (t) Accumulate along the penetration axis z direction to obtain the instantaneous vertical reaction force F z (t), and simultaneously record the tip displacement s(t); the two can be paired to draw the resistance-displacement curve F z (s). The peak value F of the curve z,max Represents the ultimate reaction force generated by the soil-rock mixture on the probe during the penetration process. Normalizing this peak value by the cross-sectional area A of the penetrometer probe, the equivalent vertical bearing capacity can be obtained:

[0158]

[0159] Considering the amplification of the limit value by the impact inertia, the dynamic load correction factor η=1-k is introduced v V0 / V ref (where k v is the empirical coefficient, V0 is the initial falling velocity of the penetrometer), the corrected static bearing capacity is:

[0160]

[0161] Thus, a prediction of the bearing capacity of the soil is provided.

[0162] The present invention has a reasonable concept. By constructing an accurate discrete element model of soil-rock mixture, selecting appropriate microscopic contact models and parameters, and performing dynamic mechanical response analysis, it can accurately reflect the mechanical response characteristics of the soil-rock mixture during the impact penetration process, and provide an effective analysis tool for the impact penetration research of soil-rock mixture.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing the dynamic response characteristics of impact penetration testing of a soil-rock mixture, characterized in that: The specific steps include: (1) Establishing a discrete element model of soil-rock mixture (1.1) Constructing a rock-free soil impact penetration test model A benchmark model containing only soil particles is established within the discrete element calculation domain Ω to ensure computational efficiency and analytical accuracy. (1.2) Construct an impact penetration test model for soil-rock mixture; (2) Contact model A linear contact model of bond rolling resistance is uniformly introduced at the soil-soil contact interface to accurately characterize the stress and failure behavior of sandy soil particles. (3) Analysis results The impact penetration test model of the soil-rock mixture mentioned above is used to analyze the dynamic mechanical response of the impact penetration process, where the governing equation is as follows: Among them, m i ,I i are the mass and moment of inertia of the unit respectively; F ij ,M ij are the ARR-Linear contact force and moment, respectively.

2. The method for analyzing dynamic response characteristics of impact penetration testing of a soil-rock mixture according to claim 1, wherein: The specific process of step (1.1) is: (1.1.1) Domain Partitioning Divide the discrete element computational domain Ω into N concentric shells The thickness of each layer can be taken as Δr = R / N, where R is the width of the discrete element calculation domain; (1.1.2) Scaling factor setting Assign a particle scaling factor α to the i-th layer i (i=1:N), satisfying: 1＜α1＜α2＜…＜α N , The typical value is from the central high resolution area α1=6 to the far field coarse resolution area α N =6; (1.1.3) Particle size mapping formula The reference particle size d is taken from the measured particle size distribution of the soil ref implement: d i =α i d ref ,i=1:N; (1.1.4) Sample loading The random sedimentation-gravity consolidation algorithm is used to fill the partitioned particles and iterate through explicit dynamic relaxation to: The quasi-static initial stress field is obtained, which is consistent with the porosity measured indoors; The rock-free soil DEM impact penetration model constructed through the above steps (1.1.)-(1.1.4) takes into account both the accuracy of the central area contact analysis and the overall calculation scale, laying the foundation for the subsequent introduction of irregular rocks and dynamic penetration analysis.

3. The method for analyzing dynamic response characteristics of impact penetration probing of a soil-rock mixture according to claim 1, wherein: The process of step (1.2) is: (1.2.1) Stone geometry generation Several points are randomly generated on the surface of the ellipsoid using the spherical coordinate system, as follows: For a given ellipsoid primitive, the position of any point on the ellipsoid surface in the spherical coordinate system can be determined by five parameters R1, R2, R3, θ, To jointly determine; when constructing a polyhedron with N vertices based on an ellipsoid primitive, the vertices of the polyhedron are divided into two parts, which are random points independently selected from the upper and lower halves of the ellipsoid primitive surface; assuming that the number of vertices selected from the upper half of the ellipsoid primitive surface is M, then the θ of these random points i and They are: Where η1 and η2 are two independent random numbers uniformly distributed in [0, 1], and δ is a variable; the remaining polyhedron vertices are independently and randomly selected from the lower half of the ellipsoidal primitive surface and are determined similarly according to the above formula; in the Cartesian coordinate system, the coordinates of the polyhedron vertices (x i ,y i ,z i ) is expressed as: Where (x0, y0, z0) is the center coordinate of the ellipsoid primitive, R1, R2, and R3 are the lengths of the three semi-major axes of the ellipsoid primitive respectively; then, call scipy.spatial.ConvexHull Calculate the geometric convex hull and use the trimesh library to export the STL mesh stone_k.stl, which is the shell of a single irregular stone; (1.2.2) Domain merging and initialization (1.2.2.1) Domain Overlay Oh=Oh soil ∪Ω rock ; Automatically adjust the initial position of the stone and adjacent soil particles to make the relative overlap δ0≤0.05d min ; (1.2.2.2) Gravity consolidation Turn on gravity g, and relax the explicit dynamics to A discrete element model of soil-rock mixture with the same porosity as the indoor porosity is obtained.

4. The method for analyzing dynamic response characteristics of impact penetration testing of a soil-rock mixture according to claim 1, wherein: The numerical solution process and control equations of the stress and failure behavior of sandy soil particles in step (2) are as follows: (2.1) Contact determination The radius expansion method is used to detect whether two particles i and j overlap, and the normal overlap is obtained: d n =R i +R j -||x ij ||; (2.2) Normal force calculation F n =k n d n ; Among them, k n is the normal contact stiffness; if δ n <0, contact failure; (2.3) Tangential force increment update Where Δu s is the tangential displacement increment of the current step, k s is the tangential stiffness; (2.4) Coulomb correction Where μ is the coefficient of kinetic friction between particles; (2.5) Rolling resistance torque Among them, k r is the rolling resistance stiffness, Δθ r is the relative roll angle increment of this step, η is the rolling resistance coefficient, R eq is the equivalent radius; (2.6) Bond strength criterion If satisfied or The contact is considered to be broken; thereafter, the contact switches to the "friction + rolling resistance" mode and no longer bears tensile stress.

5. The method for analyzing dynamic response characteristics of impact penetration testing of a soil-rock mixture according to claim 1, wherein: The specific process of the dynamic mechanical response analysis of the impact penetration process in step (3) is as follows: (3.1) Motion state of particles Track the displacement, velocity, and acceleration of particles, analyze their deformation and motion patterns, and reveal the dynamic response characteristics of the soil-rock mixture, as follows: During the impact simulation phase, the displacement u of particle k k (t), speed v k (t) and acceleration a k (t) is automatically updated by the discrete element solver in each integration step Δt; specifically, the discrete element solver first calculates the resultant force F at the previous moment. k Solve for the instantaneous acceleration a k =F k / m k , and then complete the kinematic recursion: (3.2) Penetration resistance The total contact pairs formed by the penetrometer and the surrounding particles are recorded as Γ(t); the discrete element solver automatically outputs the normal force F of each contact element at each integration step. {n,j} (t) and tangential friction F {s,j} (t); by real-time all normal forces F {n,j} (t) and tangential friction F {s,j} (t) Accumulate along the penetration axis z direction to obtain the instantaneous vertical reaction force F z (t), and simultaneously record the tip displacement s(t); the two can be paired to draw the resistance-displacement curve F z (s); peak value F of the curve z,max Represents the ultimate reaction force generated by the soil-rock mixture on the probe during the penetration process; the peak F z,max Normalized to the equivalent vertical bearing capacity according to the cross-sectional area A of the penetrometer probe: Considering the amplification of the limit value by the impact inertia, the dynamic load correction factor η=1-k is introduced v V0 / V ref Among them, k v is the empirical coefficient, V0 is the initial falling velocity of the penetrometer, and the corrected static bearing capacity is: Thus, a prediction of the bearing capacity of the soil is provided.

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