Rock material explosion impact data acquisition method

Abstract

The invention relates to the technical field of engineering material explosion and impact data evaluation, in particular to a rock material explosion impact data acquisition method, which comprises the following steps: correcting an initial HJC model to obtain a corrected HJC model suitable for a rock material; parameters in the corrected HJC model are determined; and acquiring rock material explosion experiment data and rock material impact experiment data based on a rock explosion experiment, an impact experiment and the corrected HJC model. According to the method, rock material impact experiment data can be accurately obtained through the corrected HJC model.

Description

Technical Field

[0001] The present application relates to the technical field of explosion and impact data evaluation of engineering materials, and in particular to a method for acquiring explosion impact data of rock materials. Background Art

[0002] In the field of civil engineering, for processes involving building materials, such as tunnel construction, it is necessary to comprehensively consider the possible conditions that may occur during the entire construction process to ensure the safety of construction. However, due to the limitation of the test volume, traditional research methods are mostly based on relevant premises, with limited factors considered, and often only partial laws are obtained, which is difficult to meet the actual needs of engineering. With the development of technology, many dynamic damage constitutive models have been proposed in recent years to describe the change process and failure mechanism of the internal force of building materials under the action of external dynamic loads during construction. The essence of the damage constitutive model is to study the constitutive relationship. The constitutive relationship refers to the relationship between the stress tensor and the strain tensor of building materials in specific application scenarios. Accordingly, a set of relations that link the parameters describing the deformation of continuous media with the parameters describing the internal force is called the constitutive equation. The constitutive equation is a comprehensive reflection of the macroscopic mechanical properties of the structure or material, and is one of the important contents of rational mechanics research.

[0003] At present, HJC is one of the most commonly used constitutive models in engineering. Compared with other models, the HJC model has a simpler constitutive relationship and fewer initial parameters, and takes into account the hydrostatic pressure, damage factor and strain rate dependence of the material. However, since the HJC model was originally proposed for concrete materials, when it is applied to concrete materials, the recommended parameter values ​​can be directly used to describe the relationship between DIF and strain rate, but the parameter values ​​in rock materials need further study. In addition to the HJC model, several other commonly used dynamic damage constitutive models such as the JH-2 model, the K&C model and the RHT model also have these shortcomings when describing the rate effect.

[0004] Rock is a common material in industries such as civil engineering and military engineering. During tunnel excavation, coal mining, and projectile impact, rock materials often show different failure modes under strong external dynamic loads. Among them, rock materials near the load usually undergo compression and shear crushing failure, while rocks at the far end undergo tension failure under the action of tensile stress, accompanied by the initiation and expansion of tensile cracks. In order to reasonably predict the fracture form of rock materials under different external loads and provide theoretical guidance for engineering, it is necessary to clarify the load action mechanism and the corresponding internal force change process of rock materials. Therefore, it is very important to adopt appropriate methods to improve the HJC model and accurately obtain the explosion impact data of rock materials through the improved HJC model. Summary of the invention

[0005] In order to enable the current HJC model to accurately obtain rock material explosion impact data, the present application provides a rock material explosion impact data acquisition method.

[0006] The embodiment of the present application is implemented as follows:

[0007] A method for acquiring rock material explosion impact data, comprising:

[0008] Based on the correction of the initial HJC model, a corrected HJC model suitable for rock materials is obtained;

[0009] Determining parameters in the modified HJC model;

[0010] Based on the rock explosion experiment and impact experiment and the modified HJC model, rock material explosion experiment data and rock material impact experiment data are obtained;

[0011] The step of modifying the initial HJC model includes:

[0012] The strength model in the initial HJC model is corrected using three limit surfaces, wherein the three limit surfaces include a maximum strength surface, a residual strength surface, and a yield surface, and the strength model after correction has continuity at the discontinuity point; wherein the maximum strength surface is represented by a piecewise function, the residual strength surface is parallel to the maximum strength surface, and the yield surface is determined based on an interpolation method between the maximum strength surface and the residual strength surface;

[0013] The yield surface is modified based on a dynamic enhancement factor, wherein the dynamic enhancement factor includes a compressive strain rate enhancement factor and a tensile strain rate enhancement factor; the compressive strain rate enhancement factor is a ratio of dynamic compressive strength to static compressive strength, and the tensile strain rate enhancement factor is a ratio of dynamic tensile strength to static tensile strength.

[0014] The damage model in the initial HJC model is modified to a total damage model after coupling tensile damage with compressive damage, and the tensile damage model is represented by an exponential tensile softening function.

[0015] In a possible implementation, the maximum intensity surface σ m Using the piecewise function shown in formula (1),

[0016]

[0017] Where: a1 and a2 are limit surface parameters, is the tensile-compression meridian ratio, which is used to describe the shape change of the failure surface as the hydrostatic pressure changes. It is expressed by formula (2):

[0018]

[0019] In a possible implementation, the residual strength surface σ r It is expressed by formula (3):

[0020]

[0021] In a possible implementation, the yield surface is expressed by equation (4):

[0022] σ y = r[D(σ r -σ m )+σ m ] (4)

[0023] Where: r is the ratio of the current meridian to the compression meridian, and Rhodes angle Related, as shown in formula (5),

[0024]

[0025] Where: |S ij | is the determinant of the deviatoric stress tensor, i.e., the third invariant.

[0026] In a possible implementation, the dynamic enhancement factor is as shown in formula (6):

[0027]

[0028] Where: is the strain rate, is the reference strain rate, W x , W y , S and F m is a related parameter, and the value of the related parameter is determined by the rock dynamic tension and compression test data; at this time, the yield surface is expressed by formula (7),

[0029]

[0030] Where: and They are the yield surface, maximum strength surface and residual strength surface after strain rate correction respectively.

[0031] In a possible implementation, in the formula (7), Take 1.0 / s.

[0032] In a possible implementation, the tensile damage model can be expressed by equation (8):

[0033]

[0034] Where: n1 and n2 are constants, ε frac is the tensile fracture strain, ε p is the equivalent plastic strain; at this time, the total damage is as shown in formula (9),

[0035] D total =1-(1-D c )(1-D t ) (9)

[0036] Where: D c Compression damage.

[0037] In a possible implementation, the state equation in the modified HJC model is represented by the following piecewise function:

[0038]

[0039] Where: μ is the volume strain, f t is the tensile strength of the material, D is the damage factor, μ crush and μ plock P crush and P lock The corresponding volume strain, where μ plock Including plastic volume strain μ lock and elastic volume strain.

[0040] In a possible implementation, the volume strain K, elastic limit hydrostatic pressure P crush and elastic limit volume strain μ crush The calculations are performed by the following three formulas:

[0041]

[0042] P crush =f c / 3

[0043] μ crush =P crush / K

[0044] Plastic compaction volume strain μ lock It is calculated by the following two formulas:

[0045] μ lock =ρ g / ρ0

[0046] ρ g =ρ0 / (1-q)

[0047] Where q is the porosity of granite. K1, K2 and K3 are determined by P>P in the state equation.lock The curve of the stage is fitted to the Hugoniot experimental data points. After obtaining the value of the pressure parameter, μ is obtained by back calculation. plock The value of

[0048] Optionally, the Hugoniot experimental data are selected from literature reference values ​​or data points are obtained by the following Hugoniot empirical formula:

[0049] Where C1 and S1 are empirical coefficients related to rock properties.

[0050] In one possible implementation, the rock material explosion test data and impact test data include at least one of the shape and size of craters and plugs, residual velocity of projectiles, reflection and transmission waveforms, brittle tensile failure of rocks, crack-related data, unit peak pressures at different positions of the blasthole, and final failure shape of the sample.

[0051] The technical solution provided by this application can at least achieve the following beneficial effects:

[0052] In view of the shortcomings of the existing constitutive model, the strength model and damage model in the initial HJC constitutive model were improved. The strain rate relationship was optimized and various parameters were determined. A modified HJC model was obtained, which can accurately describe the failure morphology of brittle rock materials under external dynamic loads. This model is helpful to accurately obtain rock material impact test data through the modified HJC model, and provide certain theoretical guidance for the future field of rock material explosion impact data evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0054] Figure 1 Schematic diagram of the constitutive relationship of the initial HJC model, where (a) represents the state equation; (b) represents the strength model; and (c) represents the damage model.

[0055] Figure 2 A schematic diagram of a flow chart of a method for acquiring rock material explosion impact data in one embodiment;

[0056] Figure 3 for Figure 2 Schematic diagram of the specific steps of step 100;

[0057] Figure 4 It is the strength model diagram after correction, where (a) shows the relationship diagram between the three limit surfaces; (b) shows the deviated plane diagram;

[0058] Figure 5 Figure 1 is a fitting curve diagram of rock material DIF data, where (a) represents DIF T The fitting curve of DIF C The fitting curve of

[0059] Figure 6 Schematic diagram of three types of tensile strain softening curves;

[0060] Figure 7 The Hugoniot data fitting results of rock materials, where Figure (a) shows the fitting results of different types of rocks; Figure (b) shows the granite fitting results based on the Hugoniot empirical formula;

[0061] Figure 8 This is the result diagram of granite limit surface parameter fitting;

[0062] Fig. 9 Schematic diagram of projectile penetrating granite target plate, where (a) is a schematic diagram of the experimental scene; (b) is a diagram of the experimental model;

[0063] Fig.10 Comparison diagram of the damage morphology of the granite target plate after impact in the experimental group, the modified HJC constitutive model group and the initial HJC constitutive model group;

[0064] Fig.11 Comparison diagram of the residual velocity of the projectile predicted by the theory and the modified HJC constitutive model and the initial HJC constitutive model;

[0065] Fig.12 The results of sensitivity analysis of the parameters of the modified HJC model;

[0066] Fig.13 The experimental scene diagram and experimental model diagram of SHPB experiment of tuffaceous sandstone;

[0067] Fig.14 This is a comparison diagram of three waves in the SHPB experiment of tuffaceous sandstone;

[0068] Fig.15 Comparison of the damage morphology of tuffaceous sandstone specimens after impact (the actual length of the steel rod is not shown), where (a) improved HJC-100μs; (b) improved HJC-160μs; (c) improved HJC-500μs; (d) modified HJC-internal damage diagram; (e) initial HJC-internal damage diagram; (f) actual state diagram in the experiment;

[0069] Fig.16 This is the experimental scene diagram and experimental model diagram of granite air-coupled single-hole blasting;

[0070] Fig.17 The comparison diagram of the damage morphology of granite single-hole blasting, where (a) represents the initial HJC-containing copper tube; (b) and (c) represent the improved HJC-containing copper tube; (d) represents the actual state diagram of the experiment; (e) represents the original HJC-without copper tube; (f) and (g) represent the improved HJC-without copper tube;

[0071] Fig.18 Figure 2 is the unit peak pressure decay law diagram, where Figure (a) represents the improved HJC; Figure (b) represents the original HJC;

[0072] Fig.19 This is a diagram of the water-coupled explosion experimental device;

[0073] Fig. 20 This is the model diagram of water-coupled blasting experiment;

[0074] Fig.21 This is the rock destruction process of water-coupled blasting, where (a) is 5μs; (b) is 10μs; (c) is 20μs; (d) is 100μs;

[0075] Fig. 22 This is a comparison diagram of the damage morphology of water-coupled blasting. DETAILED DESCRIPTION

[0076] In order to make the purpose, implementation mode and advantages of the present application clearer, the exemplary implementation mode of the present application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only part of the embodiments of the present application, not all of the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0077] It should be noted that the brief description of terms in this application is only for the convenience of understanding the embodiments described below, and is not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their ordinary and common meanings.

[0078] The terms "first", "second", "third", etc. in the specification and claims of this application and the above drawings are used to distinguish similar or similar objects or entities, and do not necessarily mean to limit a specific order or sequence, unless otherwise noted. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances.

[0079] The terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover but not exclude inclusion, for example, a product or device comprising a list of components is not necessarily limited to all the components expressly listed but may include other components not expressly listed or inherent to such product or device.

[0080] In order to clearly describe the technical solutions of the embodiments of the present application, some terms and technologies involved in the embodiments of the present application are briefly introduced below:

[0081] like Figure 1 As shown in the figure, the initial HJC constitutive model consists of the state equation, strength model and damage model, and takes into account the strain rate effect of the material. Under the strong external dynamic load, the material will be in a high pressure state and produce a large volume strain, and the state equation can be used to describe the quantitative correspondence between hydrostatic pressure and volume strain. The state equation relationship in the HJC constitutive model can be expressed by the following piecewise function. The state equation can be expressed by Figure 1 Figure (a) shows.

[0082]

[0083] Where: μ is the volume strain, f t is the tensile strength of the material, D is the damage factor, μ crush and μ plock P crush and P lock The corresponding volume strain, where μ plock Including plastic volume strain μ lock and elastic volume strain, K1, K2 and K3 are all unknown parameters.

[0084] pass Figure 1 As shown in Figure (a), when the hydrostatic pressure P is greater than 0, the material will first experience the elastic stage; when P is greater than the pore collapse pressure P crush After that, the internal micropores begin to be gradually compacted and enter the plastic compaction stage; when P reaches the pore compaction pressure P lock After that, the internal air is discharged, and the internal micropores have been completely squeezed and compacted, thus entering the plastic complete compaction stage; when P is less than 0, there will be a -f after the elastic stretching stage. t The cutoff pressure of (1-D) can be regarded as the ideal elastic-plastic tension stage.

[0085] As the hydrostatic pressure increases, the material strength will gradually increase. In the initial HJC constitutive model, the material strength is expressed by equivalent stress, and the normalized equivalent stress is expressed by the following strength equation. Correspondingly, the strength model diagram can be found in Figure 1 Figure (b) in .

[0086]

[0087] Where: * is the normalized equivalent stress, P * is the normalized hydrostatic pressure, A, B, and N are strength-related parameters (limit surface parameters). C is a strain rate-related parameter, is the characteristic strain rate, is the reference strain rate, S max is the maximum normalized equivalent stress.

[0088] In addition, the damage model is calculated by accumulating the equivalent plastic strain and the plastic volume strain. Specifically, the damage model D can be expressed by the following formula:

[0089]

[0090] Where: Δε p and Δμ p are the equivalent plastic strain increment and plastic volume strain increment, respectively. and are the fracture plastic strain and fracture volume strain respectively. The damage model diagram can be found in Figure 1 Figure (c) in Figure 2. As the strain rate and damage level increase, the strength of the material will increase and decrease to a certain extent, respectively. However, as the hydrostatic pressure increases, the effect of the A(1-D) part on the strength gradually decreases, which leads to a small difference in the strength of the intact and fully damaged units under high hydrostatic pressure.

[0091] Since the above initial HJC constitutive model was originally proposed for concrete materials, the recommended parameter values ​​can be directly used to describe it when it is applied to concrete materials, but the parameter values ​​in rock materials need further study.

[0092] It should be noted that the stress-strain relationship of materials under static and dynamic action is different. The main reason is that the different strain rates lead to changes in material strength. In addition, the initial HJC constitutive model also ignores the influence of the third invariant of the deviatoric stress tensor on the yield surface. Based on this, this application proposes a method for acquiring rock material explosion impact data, such as Figure 2 As shown, the specific solutions include the following:

[0093] Step 100, based on the correction of the initial HJC model, a corrected HJC model suitable for rock materials is obtained. Figure 3 As shown, this step specifically includes step 110 to step 130:

[0094] Step 110, using three limit surfaces to correct the strength model in the initial HJC model, wherein the three limit surfaces include the maximum strength surface σ m , residual strength surface σ r and yield surface σ y , the intensity model after correction has continuity at the discontinuity point.

[0095] First, see Figure 4 In Figure (a), the maximum intensity surface σ m Using the piecewise function expression shown in formula (1), it can be seen that the formula ensures continuity at the discontinuity points.

[0096]

[0097] Where: a1 and a2 are limit surface parameters, f c Represents the static compressive strength, is the tensile and compressive meridian ratio, Used to describe the change in shape of the failure surface as the hydrostatic pressure P changes; see Figure 2 Figure (b) in It can be expressed as formula (2), and linear interpolation is used at the discontinuity points.

[0098]

[0099] Secondly, the residual strength surface σ r With the maximum strength surface σ m is an approximately parallel relationship, then σ r It can be expressed using formula (3).

[0100]

[0101] After that, the yield surface σ y The yield surface σ is determined by interpolating between the maximum strength surface and the residual strength surface. y It is expressed by formula (4).

[0102] σ y = r[D(σ r -σ m )+σ m ] (4)

[0103] Where: r is the ratio of the current meridian to the compression meridian, and Rhodes angle The specific correlation is as shown in formula (5).

[0104]

[0105] Where: |S ij | is the determinant of the deviatoric stress tensor, i.e., the third invariant.

[0106] It can be understood that by introducing the relationship between the third invariant of the deviator stress tensor, the Rhodes angle and the meridian, it is helpful to make a reasonable correction to the yield surface, improve the problem that the initial HJC model cannot describe the shape change of the yield surface when it transitions from low pressure to high pressure due to not considering the influence of the Rhodes angle, so that the HJC model finally obtained by this scheme can be applicable to rock materials, so that the blasting impact data of rock materials can be accurately obtained through the final HJC model.

[0107] Step 120, modifying the yield surface based on a dynamic enhancement factor, wherein the dynamic enhancement factor includes a compression strain rate enhancement factor and a tensile strain rate enhancement factor; the compression strain rate enhancement factor is a ratio of dynamic compressive strength to static compressive strength, and the tensile strain rate enhancement factor is a ratio of dynamic tensile strength to static tensile strength.

[0108] Specifically, since the compression strain rate enhancement factor is the ratio of dynamic compressive strength to static compressive strength, and the tensile strain rate enhancement factor is the ratio of dynamic tensile strength to static tensile strength, the dynamic enhancement factor can be expressed as follows:

[0109]

[0110] Where DIF C and DIF T are the compression strain rate enhancement factor and the tensile strain rate enhancement factor, respectively. c '、f c 、f t ' and f t They respectively represent the dynamic compressive strength, static compressive strength, dynamic tensile strength and static tensile strength of the material.

[0111] Since the initial HJC constitutive model was originally proposed for concrete materials, the relationship between the dynamic enhancement factor DIF and the strain rate is basically based on the CEB-FIB recommended value, which has two inevitable problems: First, the recommended value is reasonable for concrete materials, but it is often difficult to determine for rock materials. In addition, previous studies have found that both concrete and rock materials have an upper limit value of DIF, which is ignored by existing models, so it is easy to overestimate DIF under high strain rate conditions, but this problem has not been effectively solved at present, so this application performs step 120.

[0112] In this step, the dynamic enhancement factor DIF can be expressed by formula (6):

[0113]

[0114] In the formula, is the strain rate, is the reference strain rate, W x , S, F m and W y are related parameters.

[0115] Currently, for W x , W y , S and F m The reference values ​​are limited to concrete materials. Therefore, this application is based on fitting a large number of rock dynamic tensile test and compression test data to determine the DIF of rock materials shown in formula (6): T and DIF C Variation with strain rate.

[0116] The process of determining the relationship between DIFT and DIFC in equation (6) as a function of strain rate can be found in Figure 5 As shown, through analysis Figure 5 It can be seen that the strain rate of rock material is 10 0 / s, DIF begins to increase rapidly, so the rock Take 1.0 / s, when the strain rate reaches 10 4 / hour, DIF T It approaches the limit value of 8.56. DIF at different strain rates C The experimental data are basically within the prediction curve of the tensile-compressive strength ratio of 0.1 to 0.3, and when the strain rate reaches 10 4 / , the corresponding limit value can be predicted. It can be seen that the experimental data of tensile DIF and compression DIF are consistent with the DIF determined in this application. T and DIF C The fitting degree of the relationship changing with strain rate is higher.

[0117] Based on formula (6), the yield surface is modified, that is, the modified yield surface can be expressed by formula (7):

[0118]

[0119] In formula (7): and They are the yield surface, maximum strength surface and residual strength surface after strain rate correction, respectively. It can be understood that the tension and compression selection of DIF is positively and negatively correlated with the hydrostatic pressure.

[0120] Since step 120 uses DIF to modify the yield surface, that is, the strain rate dependence effect of the material is taken into account, the HJC model finally obtained in this application can be accurately applied to rock materials.

[0121] The description process of the material compression damage by the initial HJC model does not reasonably consider the brittle tensile damage of geotechnical materials under external dynamic loads, so the present application also performs step 130.

[0122] Step 130, the damage model in the initial HJC model is modified to a total damage model after coupling tensile damage and compressive damage, and the tensile damage model is represented by an exponential tensile softening function.

[0123] It should be noted that the tensile strain softening of materials mainly includes three forms: linear softening, bilinear softening and exponential softening. The three different forms of tensile strain softening can be found in Figure 6 .

[0124] Since rock materials are more in line with the exponential softening form, this application uses the exponential tensile softening function shown in the following formula (8) to describe the tensile damage of rock materials.

[0125]

[0126] In formula (8), n1 and n2 are constants, and n1 can be 3.0 and n2 can be 6.93; ε frac is the tensile fracture strain. p is the equivalent plastic strain.

[0127] By coupling tensile damage with compressive damage, the total damage model can be obtained. The total damage model can be expressed by formula (9):

[0128] D total =1-(1-D c )(1-D t ) (9)

[0129] In formula (9): D c is compression damage, which is consistent with the damage calculation method in the initial HJC model, that is, Where: Δε p and Δμ p is the equivalent plastic strain increment and plastic volume strain increment, and are the fracture plastic strain and fracture volume strain.

[0130] After the correction of the above steps 110-130, the new HJC model applicable to geotechnical materials obtained in the present application can be expressed as the following three parts:

[0131] Part I: The state equation can be expressed by the following piecewise function:

[0132]

[0133] Where: μ is the volume strain, f t is the tensile strength of the material, D is the damage factor, μ crush and μ plock P crush and P lock The corresponding volume strain, where μ plock Including plastic volume strain μ lock and elastic volume strain.

[0134] Part II: Strength model, the strength model is obtained by passing the maximum strength surface σ m , residual strength surface σ r and yield surface σ y means, specifically:

[0135]

[0136] In the above formula: a1 and a2 are limit surface parameters, is the tensile and compressive meridian ratio, Used to describe the change in shape of the failure surface as the hydrostatic pressure changes; The above formula (2) shows that the relationship between the third invariant of the deviator stress tensor, the Rhodes angle and the meridian can be seen in the above formula (5). The dynamic enhancement factor DIF can be expressed by the above formula (6), which will not be repeated here. and They are the yield surface, maximum strength surface and residual strength surface after strain rate correction respectively.

[0137] The third part is the damage model. The damage model can be expressed by the following formula: D total =1-(1-D c )(1-D t ),in, D c for Δε p and Δμ p is the equivalent plastic strain increment and plastic volume strain increment, and are the fracture plastic strain and fracture volume strain.

[0138] It can be seen from the above complete new HJC model applicable to geotechnical materials that the new HJC model applicable to geotechnical materials in this application includes pressure parameters K, K1, K2, K3, P crush , P lock , μ crush , μ lock and μ plock , limit surface parameters a1 and a2, rate effect parameters W x , S, F mand W y , damage parameters D1, D2 and ε frac And the basic mechanical parameters f c 、f t , G, ρ0 and Poisson's ratio γ. Among them, the rate effect parameter It can be directly taken as 1.0 / s. The remaining parameters to be determined can be determined by the following step 200:

[0139] Step 200, determining various parameters in the modified HJC model (ie, a new HJC model suitable for geotechnical materials).

[0140] Specifically, (1) the parameters in the state equation are determined as follows:

[0141] Volume strain K, elastic limit hydrostatic pressure P crush and elastic limit volume strain μ crush They can be calculated by the following three formulas:

[0142]

[0143] P crush =f c / 3

[0144] μ crush =P crush / K

[0145] Plastic compaction volume strain μ lock It can be calculated by the following two formulas:

[0146] μ lock =ρ g / ρ0

[0147] ρ g =ρ0 / (1-q)

[0148] Where q is the porosity of granite.

[0149] K1, K2 and K3 are determined by P>P in the state equation lock The curve of the stage is fitted to the Hugoniot experimental data points. The Hugoniot experimental data of some rocks can be found from the research of previous scholars. For rock materials lacking Hugoniot experimental data, the data points can be obtained by the Hugoniot empirical formula shown in formula (10).

[0150]

[0151] In the formula, C1 and S1 are empirical coefficients related to rock properties. It should be noted that the Hugoniot experimental data of most rock materials are fitted using formula (10). The fitting results can be found in Figure 7 As shown in Figure (a), the fitting curve is consistent with the experimental data points, proving that the calculation of the Hugoniot data points by the above formula is reasonable. Therefore, the Hugoniot data points can be calculated by the above formula, and the C1 and S1 of granite are 2100m / s and 1.65 respectively. The equation of state P>P lock The results of the fitting of the Hugoniot data points can be found in Figure 7 From the figure (b) in Figure 2, we can get the value of the pressure parameter, and based on this, we can get μ by back calculation. plock The value of .

[0152] (2) The parameters in the strength model are determined as follows:

[0153] Since the effective stress values ​​of the last two sections of the maximum strength surface are both less than the compressive strength of the material, the triaxial test data cannot be used to determine the strength-related parameters a1 and a2. For rock materials, the expression of the first section of the maximum strength surface is used to fit the triaxial test data of rock. Taking granite as an example, the fitting results based on triaxial test data can be found in Figure 8 In the granite strength model, a1 is 0.454 and a2 is 0.055. x , S, F m and W y Determined by fitting.

[0154] (3) Determination of parameters in the damage model:

[0155] ε frac The value of is related to the unit size of the numerical model, so it can be calculated by the following formula:

[0156]

[0157] Where: G f is the fracture energy (take 80Nm / m 2 ). e is the equivalent unit size, which can be approximated in three-dimensional analysis by taking the cube root of the unit volume. t is the tensile strength of the material.

[0158] D1 and D2 mainly control the range and size of compression damage, and can be set to 0.04 and 1.0 respectively based on empirical values, and then adjusted according to specific applicable scenarios.

[0159] Step 300: Obtain rock explosion test data and impact test data based on the rock explosion test and impact test and the modified HJC model. As an example, a projectile penetration granite target plate test, a SHPB test of tuffaceous sandstone, a granite air-coupled explosion test, and a water-coupled explosion test can be simulated.

[0160] It should be noted that when obtaining the explosion test data and impact test data of rock materials through the modified HJC constitutive model, it is necessary to introduce the modified HJC constitutive model into the LS-DYNA material library, and obtain the strain increment through the experimental parameters in the rock explosion test and impact test. The strain increment can be used to represent the current strain, volume strain, deviatoric strain, equivalent strain and other physical quantities. Based on these physical quantities and combined with the yield criterion, it is judged whether the material yields, and the stress value is cyclically updated. Among them, the judgment of tensile and compressive damage is based on hydrostatic pressure, and then the required rock material explosion test data and impact test data are obtained through the state equation, damage model and strength model in the modified HJC constitutive model. And the rock material explosion test data and impact test data include but are not limited to the shape and size of the crater and the impact plug, the residual velocity of the projectile, the reflection and transmission waveform, the brittle tensile failure of the rock, crack-related data, the unit peak pressure at different positions of the blast hole, and the final failure form of the sample. The specific calculation process is as follows:

[0161] (1) Projectile penetration test on granite target

[0162] like Fig. 9 As shown in the figure, the following experimental conditions are set to simulate the projectile penetrating the granite target plate experiment: the compressive strength of the granite used in the experiment is 163MPa, the tensile strength is 7.1MPa, and the Young's modulus is 54GPa. The target plate size is 60cm×60cm×10cm, the bottom radius and length of the steel projectile are 1.0cm and 9.49cm respectively, and the CRH of the projectile is 3.0. The density of the projectile can be approximately calculated from the mass of the projectile (197g) to be 7.85g / cm 3 Since the model is symmetrical, a 1 / 4 model is established this time, and a symmetric boundary is added at the symmetric surface position; at the same time, a fixed constraint is added at the boundary of the model. The parameter values ​​of the improved HJC model for the above granite in this application are shown in Table 1.

[0163] Table 1. Parameters of the improved HJC model for impacted granite target

[0164]

[0165] like Fig.10As shown in the figure, in the experiment, after the projectile hit the target plate, a certain range of front craters were formed on the impact surface; after the compression and shear crushing zone and tunnel zone in the middle of the target plate were formed, the rock in the rear crater peeled off and formed a conical plug. By comparison, it can be seen that compared with the original HJC constitutive model (i.e., the initial HJC model), the morphology and size of the front and rear craters and the conical plug calculated by the improved HJC constitutive model (i.e., the modified HJC constitutive model) are very consistent with the experiment, which can better characterize the actual rupture mode of the target plate after the projectile penetrates.

[0166] See also Fig.11 The article on the projectile penetration experiment gives a theoretical model for predicting the residual velocity of a projectile after penetrating the target plate, and its calculation results can be well fitted by the Recht-Ipson formula shown in the following formula.

[0167] V r =a(V s -Vb 12 ) 1 / 2

[0168] Where: V r 、V s and V b1 are the residual velocity, initial velocity and limit piercing velocity respectively, and a is the correlation coefficient.

[0169] By comparing the HJC, RHT and theoretically predicted residual velocity of the projectile before and after the improvement, it can be seen that the residual velocity of the projectile calculated by the improved HJC and the original HJC is closer to the theoretical prediction result, while the RHT calculation result is significantly lower than the theoretical prediction result when the initial velocity of the projectile is high. The reason for the above results is that the RHT model does not take into account the upper limit of the DIF of the material, and overestimates the strength of the rock target plate at high strain rates, which makes the residual velocity of the projectile too small. The improved HJC takes into account the upper limit of DIF at high strain rates, and the present application makes a reasonable determination of the strain rate related parameters of the rock material, so its calculation results are more accurate. It is worth noting that although the original HJC also did not take into account the upper limit of the material DIF, due to the parameter S in its strength model max The upper limit of the strength surface is controlled, so the calculated results are also consistent with the theoretical prediction results.

[0170] In order to provide a reference for parameter adjustment in the subsequent application of the constitutive model, the parameter sensitivity analysis was performed with the projectile residual velocity as the objective function. The model parameters were adjusted up and down by 20% to observe the change pattern of the projectile residual velocity. We believe that the parameters that make the projectile residual velocity change by more than 20% are extremely sensitive parameters, the parameters that make the projectile residual velocity change between 10% and 20% are relatively sensitive parameters, and the remaining parameters are insensitive parameters. The results of parameter sensitivity analysis can be found in Fig.12 From the figure, we can see that the extremely sensitive parameters are ρ0, f t , a1 and ε frac , among which a1 has the most significant impact on the result. The more sensitive parameters are f c , G, F m , W x , W y , P lock , μ crush and a2.

[0171] (2) SHPB experiment of tuffaceous sandstone

[0172] The tuffaceous sandstone sample was taken from a tunnel in Xinjiang. The rock compressive and tensile strengths are 60MPa and 4MPa respectively, and the shear modulus is 10.08GPa. Fig.13 , the rock was processed into a standard cylindrical specimen with a diameter of 75mm and a height of 37.5mm. The processing unevenness of the specimen was less than 0.05mm, and the end face of the specimen was kept perpendicular to the axis. A dynamic splitting experiment was carried out using the SHPB system. The lengths of the incident rod and the transmission rod were 5m and 4m respectively, and the impact velocity was 4.95m / s. In order to keep consistent with the experiment as much as possible, the actual incident waveform was extracted and applied to the beginning of the incident rod. A non-reflecting boundary was applied to the tail end of the transmission rod to simulate the absorption effect of the energy-absorbing rod on the transmitted wave. The parameter values ​​of the improved HJC model in this application for the above-mentioned tuffaceous sandstone are shown in Table 2.

[0173] Table 2. Parameters of the improved HJC model for tuffaceous sandstone samples

[0174]

[0175] See also Fig.14 , the waveform diagram was extracted for comparison. Since the actual incident waveform of the experiment was directly extracted and applied to the beginning of the incident rod, the incident waveform used in the numerical simulation is consistent with the incident waveform of the experiment. The peak value of the transmission strain calculated by the original HJC is very close to the experimental result, but it cannot well predict the progressive softening stage after the tensile peak. The reflection and transmission waveforms calculated by the improved HJC in this application are more consistent with the experimental results, where Tr represents the projection strain; Re represents the reflection strain.

[0176] See also Fig.15 When the incident wave reaches the sample, compression and shear crushing zones are generated at both ends of the sample, accompanied by the initiation of cracks in the middle. As the stress wave continues to propagate, two main cracks and several secondary cracks are formed in the middle of the sample. As the main crack penetrates, the rock in the middle of the sample peels off. Finally, a macroscopic fracture surface is formed in the middle of the sample. Compared with the original HJC, the improved HJC can better predict the brittle tensile failure of rocks.

[0177] (3) Granite air-coupled explosion experiment

[0178] See also Fig.16 , a single-hole charge explosion experiment of granite was simulated. The diameter and height of the granite sample are 14.4cm and 15.0cm respectively, and a blasthole with a diameter of 0.645cm was drilled in the center of the sample. In order to prevent the gas from entering the cracks after the explosion and causing more serious damage, a copper tube with a thickness of 0.06cm was placed on the hole wall. Since the axial length of the explosive is much larger than its diameter, it can be considered as a plane strain problem. Based on this, a quasi-three-dimensional numerical model was established, in which the rock and the copper tube were considered as Lagrangian units, the air and the explosive were considered as ALE units, and the fluid-solid coupling algorithm was used for calculation. The parameter values ​​of the improved HJC model for the above-mentioned granite in this application are shown in Table 3.

[0179] Table 3. Parameters of the improved HJC model for air-coupled explosion of granite

[0180]

[0181] The type of explosive used in the experiment is PETN explosive. In the process of obtaining the corresponding data through the modified HJC constitutive model, the JWL state equation (EOS) shown below is usually used to express it. The specific parameter values ​​are shown in Table 4.

[0182]

[0183] Where: P J is the detonation pressure; V is the relative volume of the detonation product; E is the initial specific internal energy; A, B, R1, R2 and ω J is the JWL state equation parameter.

[0184] Table 4. PETN explosive parameters

[0185] <![CDATA[Density (kg / m 3 )]]> Explosive speed (m / s) A(GPa) B(GPa) <![CDATA[R1]]> <![CDATA[R2]]> <![CDATA[ω J ]]> <![CDATA[P CJ (GPa)]]> E(GPa) 1320 6690 586 21.6 5.81 1.77 0.282 16 7.38

[0186] The comparison between the corresponding data obtained by the modified HJC constitutive model and the experimental results is shown in Fig.17 After the explosives were detonated, the rock near the blast hole produced a crack-intensive zone under the action of the explosion shock wave. As the stress wave propagated to the far end, the rock under the action of the equivalent circumferential tensile stress underwent obvious radial crack expansion. Fig.17There are no typical circumferential tensile cracks in (d), but approximately circumferential microcracks can be seen distributed around the specimen. Even though the literature does not clearly explain the boundary conditions of the specimen, it can be roughly determined from the analysis of the above experimental results that the specimen was fixed at the boundary with a steel plate or other materials. However, perhaps due to the low flatness around the specimen, the specimen and the steel plate did not fit completely together, and some stress waves were still reflected at the boundary. Under the action of weak radial tensile stress waves, circumferential microcracks initiated in the rock specimen. In view of this, this application considered both non-reflecting boundary and free boundary conditions when using the improved HJC for calculation, and the calculation results are as follows. Fig.17 As shown in Figures (b) and (c) in the figure. The improved HJC can not only characterize the crack-intensive zone and radial tensile cracks around the blasthole, but also the annular cracks caused by radial tensile stress. The fracture mode of the rock sample after the explosion is basically consistent with the experimental results. In contrast, the original HJC can only characterize the compression and shear damage area near the blasthole, but cannot simulate the radial and annular tensile cracks. Fig.17 As shown in Figures (e) and (g), after the copper tube was removed, the damage degree of the rock near the blasthole calculated by the improved HJC increased significantly, and the crack distribution range increased, while the original HJC calculation results were basically consistent with those with the copper tube. Based on this preliminary judgment, the copper tube has little effect on the hole wall pressure, and mainly plays a role in preventing the explosive gas from entering the rock cracks. After the copper tube was removed, the increase in the degree of rock damage near the blasthole was not caused by the increase in hole wall pressure, but by the further expansion of the existing tensile microcracks under the action of the gas wedge.

[0187] In order to further verify the above hypothesis, the peak pressure of the unit at different positions away from the blasthole was extracted, and the peak pressure attenuation formula shown below was used for correlation fitting.

[0188] P r =P0(r e / r b ) -a

[0189] Where: P r is the peak pressure of the unit, P0 is the peak pressure at the pore wall, r e is the distance from the blast hole, r b is the blasthole radius, and a is the attenuation exponent.

[0190] See also Fig.18 The unit peak pressure attenuation law obtained by HJC calculation before and after the improvement is consistent with the empirical formula, and the copper tube has little effect on the peak pressure value and attenuation law, which also verifies that the above conjecture about the reason for the increase in rock damage at the hole wall after the removal of the copper tube is correct.

[0191] (4) Granite water coupled explosion experiment

[0192] In order to calculate the blasting effect of the improved HJC under different coupling media, a simulation of the granite water coupling blasting experiment was carried out. The granite used in the experiment has a compressive strength of 150MPa, a tensile strength of 7.5MPa, and a density of 2660kg / m 3 The bottom diameter of the cylindrical rock sample is 14.5 cm and the height is 14.6 cm. A blasthole with a diameter of 0.9 cm and a height of 13.6 cm was drilled in the center of the sample. Fig.19 The parameter values ​​of the improved HJC model for the granite mentioned above are shown in Table 5. The parameters of the PETN explosive used in the experiment are shown in Table 6. The line charge density is 3.2 g / m. According to these basic data, the diameter of the explosive can be calculated to be 0.165 cm. The columnar explosive is wrapped with a water hose and filled into the blast hole, and the explosive is detonated by a detonating cord.

[0193] Table 5. Parameters of the improved HJC model for water-coupled explosion of granite

[0194]

[0195] Table 6. PETN explosive parameters

[0196] <![CDATA[Density (kg / m 3 )]]> Explosive speed (m / s) A(GPa) B(GPa) <![CDATA[R1]]> <![CDATA[R2]]> <![CDATA[ω J ]]> <![CDATA[P CJ (GPa)]]> E(GPa) 1500 7450 625.3 23.29 5.25 1.6 0.28 22 8.56

[0197] See also Fig. 20 , a three-dimensional numerical model consistent with the experiment was established. Since the specimen in the experiment was placed directly on the ground, a normal constraint was added to the bottom of the model. Since no circumferential cracks appeared on the top of the specimen after the blast, a non-reflecting boundary was added to the periphery of the model. In order to avoid the calculation termination problem caused by large unit deformation, an air coupling domain consistent with the size of the rock specimen was established. In this way, the water inside the blasthole is mainly used as the explosion transmission medium, and the air overlapping with the rock is mainly used as the flow space in the fluid-solid coupling algorithm. In this model, water is described by the *MAT_NULL and GRUNEISEN state equations.

[0198] See also Fig.21 After the explosive was detonated, the rock near the blasthole wall was first crushed by the blast shock wave. Subsequently, the blast shock wave decayed into a stress wave. As the stress wave continued to propagate to the far end in the form of a cylinder, radial tensile cracks were generated in the sample under the action of equivalent tensile stress. As the solution time increased, the cracks continued to expand and eventually formed a penetration in the sample. Since the damage basically stopped evolving after the calculation time exceeded 100μs, the calculation results at 100μs can characterize the final failure form of the sample.

[0199] See also Fig. 22 After the explosion experiment, the sample showed a crushing area near the blast hole and several radial cracks. By comparing the top damage of the sample obtained by the experiment and the improved HJC calculation, it can be seen that the sample in the experiment showed an asymmetric fracture phenomenon, while the fracture form of the sample calculated by the improved HJC was relatively uniform. The reasons for the above phenomenon may be the following two points: First, the rock in reality contains a large number of microcracks, and the rock is considered as a homogeneous material in the process of obtaining the corresponding data through the modified HJC constitutive model, which may cause a certain deviation between the calculation results and the experimental results. Secondly, given that the experimental results show that the degree of damage on one side is obviously greater than that on the other side, it may also be due to a certain eccentricity of the explosive during loading, which leads to uneven distribution of explosion energy. However, the rock explosion rupture mode calculated by the improved HJC is basically consistent with the experiment, and the calculation results can be considered reasonable. Compared with the improved HJC, the original HJC can only characterize the crushing area near the blast hole, and the overall damage is quite different from the experiment. Not only that, by comparison Fig.15 As can be seen from Figures (d) to (f) in the figure, the improved HJC is also better than the original HJC in simulating the explosion microcracks inside the sample, which further verifies the accuracy of the improved HJC in explosion calculations.

[0200] It can be seen from the above step 300 that as long as the parameter values ​​in the rock material explosion test and the impact test are substituted into the modified HJC model of the present application, the modified HJC model can be used to accurately obtain the rock material explosion test data and the rock material impact test data.

[0201] In summary, this application improves the strength model and damage model of the initial HJC model, and also involves the optimization of the strain rate relationship and the determination of various parameters, thereby obtaining an HJC model that can accurately describe the failure morphology of brittle rock materials under external dynamic loads. This model provides certain theoretical guidance for the future field of rock material explosion impact data evaluation, and also has broad application prospects in many actual case analyses in civil engineering and military engineering (such as tunnel excavation, mining, and projectile impact).

[0202] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0203] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for acquiring rock material explosion impact data, characterized in that: include: Based on the correction of the initial HJC model, a corrected HJC model suitable for rock materials is obtained; Determining parameters in the modified HJC model; Based on the rock explosion experiment and impact experiment and the modified HJC model, rock material explosion experiment data and rock material impact experiment data are obtained; The step of modifying the initial HJC model includes: The strength model in the initial HJC model is corrected using three limit surfaces, wherein the three limit surfaces include a maximum strength surface, a residual strength surface, and a yield surface, and the strength model after correction has continuity at the discontinuity point; wherein the maximum strength surface is represented by a piecewise function, the residual strength surface is parallel to the maximum strength surface, and the yield surface is determined based on an interpolation method between the maximum strength surface and the residual strength surface; The yield surface is modified based on a dynamic enhancement factor, wherein the dynamic enhancement factor includes a compression strain rate enhancement factor and a tensile strain rate enhancement factor; the compression strain rate enhancement factor is a ratio of dynamic compressive strength to static compressive strength, and the tensile strain rate enhancement factor is a ratio of dynamic tensile strength to static tensile strength; The damage model in the initial HJC model is modified to a total damage model after coupling tensile damage with compressive damage, and the tensile damage model is represented by an exponential tensile softening function.

2. The method according to claim 1, characterized in that The maximum intensity surface σ m Using the piecewise function shown in formula (1), Where: a1 and a2 are limit surface parameters, is the tensile-compression meridian ratio, which is used to describe the shape change of the failure surface as the hydrostatic pressure changes. It is expressed by formula (2):

3. The method according to claim 2, characterized in that The residual strength surface σ r It is expressed by formula (3):

4. The method according to claim 3, characterized in that The yield surface is expressed by equation (4): s y =r[D(σ r -s m )+s m ] (4) Where: r is the ratio of the current meridian to the compression meridian, which is related to the Rhodes angle θ, as shown in formula (5). Where: |S ij | is the determinant of the deviatoric stress tensor, i.e., the third invariant.

5. The method according to claim 4, characterized in that The dynamic enhancement factor is shown in formula (6): Where: is the strain rate, is the reference strain rate, W x , W y , S and F m is a related parameter, and the value of the related parameter is determined by the rock dynamic tension and compression test data; at this time, the yield surface is expressed by formula (7), Where: and They are the yield surface, maximum strength surface and residual strength surface after strain rate correction respectively.

6. The method according to claim 5, characterized in that In the formula (7), Take 1.0 / s.

7. The method according to claim 1, characterized in that The tensile damage model is expressed by equation (8): Where: n1 and n2 are constants, ε frac is the tensile fracture strain, ε p is the equivalent plastic strain; at this time, the total damage is as shown in formula (9), D total =1-(1-D c )(1-D t ) (9) Where: D c Compression damage.

8. The method according to claim 1, characterized in that The state equation in the modified HJC model is expressed by the following piecewise function: Where: μ is the volume strain, f t is the tensile strength of the material, D is the damage factor, μ crush and μ plock P crush and P lock The corresponding volume strain, where μ plock Including plastic volume strain μ lock and elastic volume strain.

9. The method according to claim 8, characterized in that The volume strain K, elastic limit hydrostatic pressure P crush and elastic limit volume strain μ crush The calculations are performed by the following three formulas: P crush =f c / 3 m crush =P crush / K Plastic compaction volume strain μ lock It is calculated by the following two formulas: m lock =ρ g / p0 r g =ρ0 / (1-q) Where q is the porosity of granite; K1, K2 and K3 are determined by P>P in the state equation. lock The curve of the stage is fitted to the Hugoniot experimental data points. After obtaining the value of the pressure parameter, μ is obtained by back calculation. plock The value of Optionally, the Hugoniot experimental data are selected from literature reference values ​​or data points are obtained by the following Hugoniot empirical formula: Where C1 and S1 are empirical coefficients related to rock properties.

10. The method according to claim 1, characterized in that The rock material explosion test data and impact test data include at least one of the shape and size of craters and plugs, residual velocity of projectiles, reflection and transmission waveforms, brittle tensile failure of rocks, crack-related data, unit peak pressures at different positions of blastholes, and final failure shape of the sample.

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