Rock dynamic strength criterion establishment method based on confining pressure-strain rate coupling effect

Abstract

The invention provides a rock dynamic strength criterion establishment method based on a confining pressure-strain rate coupling effect, and relates to the technical field of rock mass engineering, the method comprises the following steps: obtaining a power function relationship between confining pressure and a coupling coefficient as well as between a strain rate and the coupling coefficient based on test data, the coupling coefficient being used for representing the coupling effect of the confining pressure and the strain rate; constructing a coupling effect model according to the coupling effect of the confining pressure and the strain rate and the power function relationship; and constructing a rock dynamic strength model based on the confining pressure effect, the strain rate effect and the coupling effect model. Based on the relation between the confining pressure and the coupling coefficient and between the strain rate and the coupling coefficient, the rock dynamic strength criterion is established by comprehensively considering the confining pressure effect, the strain rate effect and the coupling effect, so that the problem that the dynamic strength in the wide confining pressure and wide strain rate range cannot be estimated according to the existing dynamic rock strength criterion is solved; and errors caused by neglecting the coupling effect in the existing dynamic rock strength criterion are eliminated.

Description

Technical Field

[0001] The present application relates to the field of rock engineering technology, and in particular to a method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect. Background Art

[0002] As mining depths and tunneling depths increase, accurately characterizing the mechanical properties of rock under the coupled effects of in-situ stress and strain rate is crucial for efficient excavation and disaster prevention and mitigation in deep underground projects. Traditional static rock strength criteria underestimate rock strength during assessments because they fail to account for the dynamic strength enhancement effects caused by blasting impact. Therefore, dynamic rock strength criteria are introduced for evaluation. Currently, research on dynamic rock strength criteria is relatively limited, and existing dynamic failure criteria are mostly based on classic rock failure criteria, such as the Mohr-Coulomb (MC) strength criterion and the Hoek-Brown (HB) strength criterion.

[0003] Although the existing dynamic rock strength criterion has basic theoretical value in the analysis of rock dynamic properties, it ignores the influence of the interaction between confining pressure and strain rate. Therefore, it is difficult to accurately estimate the dynamic strength of rock under complex working conditions and over a wide range of confining pressure and strain rate. Summary of the Invention

[0004] The purpose of this application is to address the deficiencies in the above-mentioned prior art and provide a method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect. Based on the relationship between confining pressure, strain rate and coupling coefficient, the rock dynamic strength criterion is established by comprehensively considering the confining pressure effect, strain rate effect and coupling effect. This solves the problem that the existing dynamic rock strength criterion cannot estimate the dynamic strength within a wide confining pressure and strain rate range, and eliminates the error caused by the existing dynamic rock strength criterion ignoring the coupling effect.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of the present application are as follows: In one aspect of an embodiment of the present application, a method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect is provided, the method comprising: Based on the test data, the relationship between confining pressure, strain rate and coupling coefficient is a power function relationship. The coupling coefficient is used to characterize the coupling effect between confining pressure and strain rate. A coupling effect model is constructed based on the coupling effect of confining pressure and strain rate and the power function relationship; Based on the confining pressure effect, strain rate effect and coupling effect models, a rock dynamic strength model is constructed.

[0006] Optionally, based on the confining pressure effect, strain rate effect, and coupling effect models, constructing a rock dynamic strength model includes: Constructing a confining pressure model based on confining pressure effect ,in, is confining pressure; Constructing a strain rate model based on strain rate effect ,in, is the strain rate; The rock dynamic strength model constructed based on the confining pressure model, strain rate model and coupling effect model is: ,in, is the dynamic triaxial compressive strength of rock, It is a coupling effect model.

[0007] Optionally, ,in, is the coupling coefficient, is the coupling coefficient, is the coupling growth coefficient, is the unconfined compressive strength of rock, is the characteristic strain rate; Coupling effect model .

[0008] Optionally, ,in, is the maximum principal stress, is the unconfined compressive strength of rock, is the intact rock constant; Confining pressure model .

[0009] Optionally, ,in, is the dynamic growth factor, is the strain rate growth coefficient, is the characteristic strain rate; Strain rate model .

[0010] Optionally, the rock dynamic strength model is: ,in, is the unconfined compressive strength of rock, is the intact rock constant, is the strain rate growth coefficient, is the characteristic strain rate, is the coupling coefficient, is the coupling growth coefficient.

[0011] Optionally, the method further comprises: Determined based on static uniaxial compression test data, static triaxial compression test data and confining pressure model and ; Based on dynamic uniaxial compression test data, as well as Sure and ,in, is the dynamic growth factor, is the dynamic uniaxial compressive strength of rock; Based on static uniaxial compression test data, static triaxial compression test data, dynamic uniaxial compression test data, dynamic triaxial compression test data, rock dynamic strength model, 、 、 and Sure and .

[0012] Optionally, the method further comprises: Determined based on static uniaxial compression test data, static triaxial compression test data and confining pressure model and ; Based on dynamic uniaxial compression test data, as well as Sure and ,in, is a dynamic growth factor, which can represent the exponential factor of the damage degree of rock at different strain rates. is the dynamic uniaxial compressive strength of rock; based on 、 as well as Sure and .

[0013] Optionally, the rock dynamic strength model is used to characterize the rock dynamic strength under confining pressures ranging from 0 to 225 MPa and a strain rate of 10 -6 to 600s -1 Dynamic triaxial compressive strength of rock within.

[0014] Optionally, the power function relationship between the confining pressure, strain rate, and coupling coefficient obtained based on the test data includes: Based on the test data, multiple stress-strain curves at different loading rates are drawn, where any two stress-strain curves at different loading rates have different confining pressure conditions; Based on the stress-strain curves at different loading rates, the dynamic strength-strain rate logarithmic relationship curves under different confining pressures were obtained; The linear slopes of the dynamic strength-strain rate logarithmic relationship curves under different confining pressures were extracted and fitted to obtain linear slope-confining pressure relationship curves, wherein the linear slopes of the linear slope-confining pressure relationship curves were normalized; According to the linear slope-confining pressure relationship curve, it is determined that the relationship between confining pressure, strain rate and coupling coefficient is a power function relationship.

[0015] The beneficial effects of this application include: The present application provides a method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect. The method comprises: determining, based on experimental data, that the relationship between confining pressure, strain rate, and the coupling coefficient is a power function relationship, where the coupling coefficient is used to characterize the coupling effect between confining pressure and strain rate; constructing a coupling effect model based on the coupling effect between confining pressure and strain rate and the power function relationship; and constructing a rock dynamic strength model based on the confining pressure effect, strain rate effect, and coupling effect model. Based on the relationship between confining pressure and strain rate and the coupling coefficient, a rock dynamic strength criterion is established by comprehensively considering the confining pressure effect, strain rate effect, and coupling effect. This solves the problem that existing dynamic rock strength criteria cannot estimate dynamic strength within a wide range of confining pressure and strain rate, and eliminates the errors caused by the existing dynamic rock strength criteria ignoring the coupling effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A schematic flow chart of a method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect provided in an embodiment of the present application; Figure 2 This is one of the schematic diagrams of stress-strain curves at different loading rates provided in the embodiments of the present application; Figure 3 The second schematic diagram of stress-strain curves at different loading rates provided in the embodiment of the present application; Figure 4 Schematic diagram of the dynamic strength changes of granite and green sandstone under different confining pressures provided in the embodiments of this application; Figure 5 Schematic diagram of dynamic strength changes of granite and red sandstone under different confining pressures provided in the embodiments of this application; Figure 6 A schematic diagram of a curve showing changes in normalized slope and normalized intercept with confining pressure provided in an embodiment of the present application; Figure 7 This is one of the schematic diagrams of stress-strain curves under different confining pressures provided in the embodiments of the present application; Figure 8 The second schematic diagram of stress-strain curves under different confining pressures provided in an embodiment of the present application; Figure 9 A schematic diagram of the relationship between dynamic strength and confining pressure of granite at different strain rates provided in the embodiments of this application; Figure 10 A schematic diagram of the relationship between dynamic strength and confining pressure of red sandstone at different strain rates provided in the embodiments of this application; Figure 11 The curve of the coupling coefficient as a function of confining pressure and strain rate provided in the embodiment of the present application; Figure 12 This is a schematic diagram comparing theoretical values and experimental values provided in the examples of this application; Figure 13 The second schematic diagram for comparing theoretical values and experimental values provided in the embodiments of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0019] Currently, research on dynamic strength criteria for rock is relatively limited. Existing dynamic failure criteria for rock are mostly based on existing classical rock failure criteria, such as the Mohr-Coulomb (MC) strength criterion and the Hoek-Brown (HB) strength criterion. Research has found that these criteria ignore the interplay between confining pressure and strain rate effects, and a unified dynamic strength criterion applicable to a wide range of confining pressures and strain rates has yet to be established.

[0020] In view of this, one aspect of the embodiments of the present application provides a method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect, such as Figure 1 As shown, the method includes: S10: Based on the experimental data, the relationship between the confining pressure, strain rate and coupling coefficient is a power function relationship. The coupling coefficient is used to characterize the coupling effect between confining pressure and strain rate.

[0021] S20: A coupling effect model is constructed based on the coupling effect of confining pressure and strain rate and the power function relationship.

[0022] S30: Construct a rock dynamic strength model based on the confining pressure effect, strain rate effect and coupling effect model.

[0023] This application studies the influence of confining pressure effect and strain rate effect on dynamic strength, as well as the coupling effect between the two. In the process of studying the coupling effect, the functional relationship between confining pressure and strain rate and the coupling coefficient was clarified, thereby constructing a coupling effect model. Then, a rock dynamic strength criterion considering the confining pressure-strain rate coupling effect was established by comprehensively considering the confining pressure effect, strain rate effect and coupling effect, namely, the rock dynamic strength model. In this way, the factors taken into account by the rock dynamic strength model are more comprehensive, and the degree of influence of confining pressure and strain rate on rock strength can be more accurately evaluated, thereby eliminating the error caused by the existing rock dynamic strength criterion ignoring the coupling effect. On this basis, the rock dynamic strength model has been verified to be able to cover a wider range of confining pressure and a wider range of strain rates, thereby improving the problem that the existing dynamic rock strength criterion cannot estimate the dynamic strength within a wide range of confining pressure and strain rate.

[0024] In summary, the rock dynamic strength model established in this application can be applied to a wide range of confining pressure and strain rate. To better understand the difference between its application range and that of the existing dynamic rock strength criteria, the following examples are given: the rock dynamic strength model established in this application can be applied to a confining pressure range of 0 to 225 MPa and a strain rate range of 10 -6 to 600s -1 Therefore, the rock dynamic strength model established in this application can more accurately predict or evaluate the rock dynamic strength under the conditions of confining pressure of 0 to 225 MPa and strain rate of 10 -6 to 600s -1 Dynamic triaxial compressive strength of rock within.

[0025] For a better understanding of this application, the following is a detailed description of this application: First, the test data and the coupling effect of confining pressure and strain rate are analyzed to facilitate the construction of the coupling effect model, which provides a basis for the construction of the rock dynamic strength model in S30. The construction of the coupling effect model is divided into S10 and S20: S10: Based on the experimental data, the relationship between the confining pressure, strain rate and coupling coefficient is a power function relationship. The coupling coefficient is used to characterize the coupling effect between confining pressure and strain rate.

[0026] First, test data is acquired. Then, through analysis and processing, a functional relationship is derived that accurately describes the distribution trend of the test data. This functional relationship then determines that the relationship between confining pressure, strain rate, and the coupling coefficient is a power function. It should be understood that the coupling coefficient characterizes the coupling effect between confining pressure and strain rate, that is, the influence of their interaction.

[0027] S20: A coupling effect model is constructed based on the coupling effect of confining pressure and strain rate and the power function relationship.

[0028] Based on the coupling effect relationship between confining pressure and strain rate, and combined with the power function relationship obtained by S10 (representing the functional relationship between confining pressure, strain rate and coupling coefficient), a coupling effect model related to confining pressure, strain rate and coupling coefficient can be constructed. This coupling effect model can accurately represent the coupling effect relationship between confining pressure and strain rate.

[0029] S30: Construct a rock dynamic strength model based on the confining pressure effect, strain rate effect and coupling effect model.

[0030] Analysis of the experimental data reveals that both the confining pressure effect and the strain rate effect significantly enhance the dynamic strength of rock. However, due to the coupled effects of confining pressure and strain rate, the two exhibit a mutually inhibitory relationship. Specifically, as confining pressure increases, the strain rate's effectiveness in enhancing the dynamic strength of rock decreases; similarly, as the strain rate increases, the effectiveness of confining pressure on the dynamic strength of rock also decreases. Based on this, a dynamic strength model of rock is constructed by combining the confining pressure and strain rate effects, building upon the coupled effect model.

[0031] Alternatively, test data can be obtained by testing with relevant testing equipment, such as using static uniaxial compression test equipment, static triaxial compression test equipment, dynamic uniaxial compression test equipment, and dynamic triaxial compression test equipment to test rock specimens. The required test data can be obtained using test loading data and relevant sensors. The aforementioned testing equipment can be selected from equipment well known in the art.

[0032] Optionally, the power function relationship between the confining pressure, strain rate, and coupling coefficient obtained based on the test data includes: S11: Based on the test data, a plurality of stress-strain curves at different loading rates are plotted, wherein any two stress-strain curves at different loading rates have different confining pressure conditions.

[0033] S12: Based on the stress-strain curves at multiple different loading rates, the dynamic strength-strain rate logarithmic relationship curves under different confining pressures are obtained.

[0034] S13: extracting the linear slope of the dynamic strength-strain rate logarithmic relationship curve under different confining pressures, and fitting to obtain the linear slope-confining pressure relationship curve, wherein the linear slope of the linear slope-confining pressure relationship curve is normalized.

[0035] S14: According to the linear slope-confining pressure relationship curve, it is determined that the relationship between the confining pressure, strain rate and coupling coefficient is a power function relationship.

[0036] Specifically: For example Figure 2 (a) and (b) and Figure 3 In (c) and (d), stress-strain curves at different loading rates are drawn based on the test data (e.g. Figure 2 They are drawn in , , , , , , , ,for example Figure 3 They are drawn in , , , , , , , ,),and Figure 2 Confining pressure condition in (a) is 10MPa, Figure 2 Confining pressure conditions in (b) is 20MPa, Figure 3 Confining pressure condition in (c) is 30MPa, Figure 3 Confining pressure condition in (d) To illustrate the effect of strain rate on the mechanical properties of rock samples, stress-strain curves under different loading rates are plotted, as shown in Figure 2. Figure 2 and Figure 3 As shown in Figure 2, the dynamic strength increases with the increase of strain rate. When the strain rate is 10 3 ~10 0 s -1 When the confining pressure changes between The dynamic strength under 10MPa varies from 249.78 to 346.63MPa, and under confining pressure conditions The dynamic strength under 20MPa varies from 315.64 to 387.40MPa, and under confining pressure conditions The dynamic strength under 30MPa varies from 411.04 to 483.51MPa and under confining pressure conditions The dynamic strength variation range at 40MPa is 465.03~515.13MPa.

[0037] The dynamic strength of rock has a strong strain rate effect and has a good correlation with the logarithm of the strain rate. Figure 2 and Figure 3The maximum stress point of each curve in Figure 4 As shown in (a), the dynamic strength (equal to the maximum principal stress) under different confining pressures is plotted. )-strain rate logarithm ( ) relationship curve (wherein, the curve in this article should be understood in a broad sense, including but not limited to straight lines, curved lines, etc.), indicating the relationship between the pressure and the pressure under different conditions ( MPa, 20MPa, 30MPa and 40MPa) and the relationship between the dynamic strength of granite and the logarithm of the strain rate, such as MPa, , ;for example MPa, , ;for example MPa, , ;for example MPa, , As the strain rate increases, the dynamic strength increases linearly; as the confining pressure increases, the slope of the line a n Gradually decreases, the intercept b n Gradually getting bigger, a n It can reflect the strength of the strain rate effect. b n Indicates the strain rate is 1s -1 Furthermore, several sets of dynamic triaxial compression test data with medium and high strain rates are provided, such as Figure 4 As shown in (b), the test was carried out in the range of 1000~5000GPa / s loading rate and 7~28MPa confining pressure. Figure 5 (c) in 10 -4 ~10 0 s -1 The strain rate and confining pressure range of 20~170MPa were tested. Figure 5 Middle (d) 40~160s -1 The strain rate and confining pressure range of 5~15MPa were tested, and the same reference was made to the Figure 2 and Figure 3 get Figure 4 The curve method shown in (a) gives Figure 4 (b) and Figure 5 The above test results cover a wide range of confining pressure and strain rate.

[0038] Analysis shows that the test data above used different test equipment and different loading conditions, but the test conclusions are highly consistent: for the dynamic triaxial compression test, under fixed confining pressure, the dynamic strength of the rock increases linearly with the increase in the logarithm of the strain rate (load rate), and increases faster at lower confining pressures, indicating that confining pressure has an inhibitory effect on the strain rate effect.

[0039] In order to illustrate the influence of confining pressure effect on strain rate effect, the linear slope of the dynamic strength-strain rate logarithmic relationship curve under different confining pressures was extracted, and the linear slope-confining pressure relationship curve was fitted. The linear slope of the linear slope-confining pressure relationship curve was normalized, such as extracting Figure 5 The slope of the straight line in (c) is normalized and fitted to obtain Figure 6 Zhongyu Figure 5 The corresponding curve in (c) , ), from this curve, it can be concluded that the power function fitting effect is more appropriate, thus determining that the relationship between confining pressure, strain rate and coupling coefficient is a power function type relationship, and the same can be extracted Figure 4 The slope of the line (a) in Figure 4 The slope of the straight line in (b) and Figure 5 The slope of the straight line in (d) is treated similarly. It should be understood that Figure 6 Zhongyu Figure 4 The curve corresponding to (a) , )、 Figure 4 The corresponding curve in (b) , )as well as Figure 5 The curve corresponding to (d) , ), although more points are not shown, it can also be fitted with a power function type. Figure 6 As shown in (a) and (b), the slope With the intercept b n (Can be extracted Figure 4 The intercept of (a) in Figure 4 The intercept of (b) in Figure 5 The intercept and Figure 5 The intercepts in (d) are all normalized to avoid the influence of different strain rate test ranges. Figure 6 (a) shows the normalized slope As the overall pressure The nonlinearity decreases and the power function fitting effect is better, which shows that in a wider range of confining pressure, the growth of the influence of confining pressure on the strain rate effect gradually slows down. Figure 6(b) shows the normalized intercept b n With the confining pressure The two sets of high strain rate data both showed negative values, indicating that it is not accurate to use high strain rate data to estimate the dynamic strength at medium strain rate.

[0040] Next, we will explain the influence of confining pressure on the mechanical properties of rock specimens: For example, according to experimental data, Figure 7 (a) and (b) and Figure 8 In (c) and (d), different confining pressures ( MPa, 20MPa, 30MPa and 40MPa), and Figure 7 The strain rate condition in (a) is 10 -3 s -1 , Figure 7 The strain rate condition in (b) is 10 -2 s -1 , Figure 8 The strain rate condition in (c) is 10 -1 s -1 , Figure 8 The strain rate condition in (d) is 10 0 s -1 In order to illustrate the influence of confining pressure on the mechanical properties of rock samples, stress-strain curves under different confining pressure conditions were drawn, such as Figure 7 and Figure 8 As shown in the figure, the dynamic strength gradually increases with the increase of confining pressure. When the confining pressure varies between 10 and 40 MPa, the dynamic strength changes in the range of 249.78 to 465.03 MPa, 277.38 to 483.14 MPa, 304.40 to 503.99 MPa, and 346.63 to 515.13 MPa, respectively. Compared with the effect of strain rate, the strength increase is greater.

[0041] like Figure 9 As shown in (a), the dynamic strength of granite (equal to the maximum principal stress ) and the confining pressure, for example, , ; , Under the condition of fixed strain rate, the dynamic strength increases linearly with the confining pressure. The slope of the fitting line is negatively correlated with the strain rate, while the intercept is positively correlated with the strain rate. Figure 9 (b) and Figure 10The same conclusion can be drawn from (c).

[0042] Optionally, when constructing a rock dynamic strength model based on the confining pressure effect, strain rate effect, and coupling effect models, the corresponding models can be first constructed according to the confining pressure effect and strain rate effect, and then the rock dynamic strength model can be constructed in combination with the coupling effect model. Specifically: S31: Constructing a confining pressure model based on confining pressure effects ,in, For confining pressure.

[0043] When the rock is in a static triaxial compression state, the rock strength is only affected by the confining pressure effect and increases with the increase of confining pressure. The confining pressure model can be constructed using the rock static strength criterion. .

[0044] S32: Constructing a strain rate model based on strain rate effects ,in, is the strain rate.

[0045] When the rock is in a dynamic uniaxial compression state, the rock strength is only affected by the strain rate effect and increases with the increase of the strain rate. The rock dynamic strength model can be used to construct the strain rate model. , mainly including three types: power type, exponential type and logarithmic type.

[0046] S33: The rock dynamic strength model constructed based on the confining pressure model, strain rate model and coupling effect model is: ,in, is the dynamic triaxial compressive strength of rock, It is a coupling effect model.

[0047] When the rock is in a dynamic triaxial compression state, the rock strength is affected by the confining pressure and the strain rate effect. It gradually increases with the increase of confining pressure and strain rate. The influence of the two on the dynamic strength of the rock can be expressed as According to the test data, it is found that with the increase of confining pressure, the effect of strain rate on the dynamic strength of rock decreases ( Figure 4 and Figure 5 ); At the same time, with the increase of strain rate, the effect of confining pressure on the dynamic strength of rock weakens ( Figure 8 ), indicating that there is a mutual inhibition relationship between the strengthening effects of the two on the dynamic strength of rocks.

[0048] Alternatively, for intact rocks, ,in, is the maximum principal stress, is the unconfined compressive strength of rock, is the complete rock constant; the confining pressure model is obtained .

[0049] The confining pressure effect is described by the HB criterion. Compared with the MC criterion, it can better reflect the nonlinear characteristics of rock strength under high ground stress conditions. In addition, the generalized HB criterion can describe the structural characteristics of the rock mass, providing a basis for further establishing the dynamic strength criterion of the rock mass.

[0050] Optionally, ,in, is the dynamic growth factor, is the strain rate growth coefficient, is the characteristic strain rate; and then the strain rate model is obtained .

[0051] The strain rate model has a variable power law exponent, which provides greater flexibility in describing the rate effect of rock strength.

[0052] Alternatively, the influence of confining pressure-strain rate coupling effect should be considered for the dynamic strength of rock under confining pressure conditions, and the degree of coupling has a power function relationship with the confining pressure within a wide range of confining pressure. ,in, is the coupling coefficient, is the coupling coefficient, is the coupling growth coefficient, is the unconfined compressive strength of rock, is the characteristic strain rate; based on the coupling effect of confining pressure and strain rate, the coupling effect model is obtained .

[0053] Figure 11 The curves of the coupling coefficient changing with confining pressure and strain rate are shown. When the strain rate is fixed, the coupling coefficient gradually increases with the confining pressure; when the confining pressure is fixed, the coupling coefficient gradually increases with the strain rate; with the increase of confining pressure and strain rate, the influence of the coupling effect gradually increases.

[0054] Alternatively, the rock dynamic strength criterion considering the confining pressure-strain rate coupling effect can be obtained by integrating the confining pressure effect, strain rate effect and coupling effect. For example, the rock dynamic strength model derived from the previous confining pressure model, strain rate model and coupling effect model is: ,in, is the unconfined compressive strength of rock, is the intact rock constant, is the strain rate growth coefficient, is the characteristic strain rate, is the coupling coefficient, is the coupling growth coefficient.

[0055] The dynamic strength criterion contains six parameters, including static mechanical parameters and , dynamic mechanical parameters and , coupling effect parameters and ; Fitting parameters are shown in Table 1.

[0056] Table 1 Fitting parameters of rock dynamic strength criterion Optionally, the method further comprises: Determined based on static uniaxial compression test data, static triaxial compression test data and confining pressure model and ; Based on dynamic uniaxial compression test data, as well as Sure and ,in, is the dynamic growth factor, is the dynamic uniaxial compressive strength of rock; Based on static uniaxial compression test data, static triaxial compression test data, dynamic uniaxial compression test data, dynamic triaxial compression test data, rock dynamic strength model, 、 、 and Sure and .

[0057] For example, first perform a static uniaxial compression test and a static triaxial compression test, perform at least one set of static uniaxial compression tests, and obtain a first data ( ), static triaxial compression tests need to be performed under different confining pressure conditions for multiple groups to obtain multiple second data ( ); Then, based on the confining pressure model, the first data and all the second data are fitted together to obtain the static strength parameters ( ).

[0058] Then do dynamic uniaxial compression test, do multiple sets of tests under different strains, and obtain multiple third data ( ). Combined Can calculate multiple DIF ,right DIF The dynamic strength parameters ( and ).

[0059] Finally, do a dynamic triaxial compression test, such as doing multiple groups, to obtain multiple test fourth data ( ), all the first, second, third and fourth data are fitted through the rock dynamic strength model established above, and two coupling effect parameters are obtained ( and ).

[0060] Specifically, according to the specifications of the International Society for Rock Mechanics (ISRM), standardized sample preparation and performance testing are required for complete rock cores or large rocks obtained on site. Static compression tests use φ50×100mm cylinders and impact tests use φ50×25mm or φ50×50mm cylinders. The parallelism error of the two end faces is required to be ≤0.02mm, and the side straightness deviation is required to be ≤0.3mm.

[0061] Static uniaxial and triaxial compression tests were carried out on φ50×100 mm standard specimens using a multifunctional rock testing system.

[0062] Static uniaxial compression test: After the specimen is installed, it is loaded at a constant displacement rate of 0.001 mm / s until failure. The axial stress-strain curve is recorded simultaneously, and the uniaxial compressive strength is obtained. Static triaxial compression test: Use a stress rate of 0.5 MPa / s to apply confining pressure to the target value. After the confining pressure stabilizes, start axial displacement loading. Load until failure at a constant displacement rate of 0.001 mm / s. Simultaneously record the axial stress-strain curve and obtain the triaxial compressive strength under different confining pressures. The peak strength data under different confining pressures were fitted by the confining pressure model to calculate and .

[0063] Dynamic uniaxial and dynamic triaxial compression tests were carried out on standard specimens of φ50×25 mm or φ50×50 mm using a Hopkinson bar test system.

[0064] Dynamic uniaxial compression test: A uniaxial impact test is performed on rock samples at different impact velocities using a Hopkinson bar impact test system. A set of strain gauges is attached to the incident rod and the transmission rod to collect dynamic strain data. The strain data is processed using the three-wave method to obtain the dynamic strain data at different strain rates. According to the formula Calculate the different strain rates DIF The strain rate model is used to analyze the DIF Perform fitting and obtain and .

[0065] Dynamic triaxial compression test: The improved Hopkinson bar impact test system is used to conduct triaxial impact tests on rock samples at different impact velocities. The improved Hopkinson bar impact test system is equipped with a confining pressure system. The pressure is applied to the target value by a manual hydraulic press to obtain the pressure at different strain rates and different confining pressures. .

[0066] According to the rock dynamic strength model, the rock static uniaxial compressive strength, static triaxial compressive strength, dynamic uniaxial compressive strength and dynamic triaxial compressive strength are fitted to obtain and .

[0067] The coupling effect is mainly caused by the combined effects of high confining pressure and high strain rate. The acquisition of its parameters usually relies on dynamic triaxial compression test. However, since the application of dynamic triaxial compression test technology is not yet popular, when dynamic triaxial impact test cannot be carried out, the following formula can be used to calculate the coupling effect. and At the same time, the rationality of the parameter values can be verified based on this formula.

[0068] Optionally, the method further comprises: Determined based on static uniaxial compression test data, static triaxial compression test data and confining pressure model and ; Based on dynamic uniaxial compression test data, as well as Sure and ,in, is a dynamic growth factor, which can represent the exponential factor of the damage degree of rock at different strain rates. is the dynamic uniaxial compressive strength of rock; based on 、 as well as Sure and .

[0069] The above test data reveals that the coupling effect occurs under conditions of relatively high confining pressure and strain rate. This means that the only way to obtain coupling effect parameters is to conduct dynamic compression tests on rock under constrained conditions. However, triaxial dynamic compression testing technology is not widely available, which poses a challenge in obtaining coupling effect parameters in practical engineering applications. Confining pressure and strain rate are external factors influencing the coupling effect, while rock properties are internal factors influencing the coupling effect. Different rock types inevitably have different degrees of coupling effects, making it crucial to establish a relationship between coupling effect parameters and rock property parameters. The value depends on many factors, such as grain size, mineral composition, etc., which can fully reflect the type of rock.

[0070] Two coupling effect parameters and and rock parameters There is a good linear relationship. Therefore, when there is no triaxial dynamic compression test data of rock, two rock parameters can be used approximately. The fitting expression is used to calculate the coupling effect parameters and At the same time, the rationality of the parameter values can be verified based on this linear relationship.

[0071] Optionally, the mean absolute percentage error (MAPE) is used to evaluate the estimation effect of the rock dynamic strength model on the experimental data: ,in, is the experimental value of rock dynamic strength, is the theoretical value of rock dynamic strength, Is a positive integer.

[0072] Combine Figure 12 (a) and (b) in Figure 13 (c) and (d) in the figure are the results of fitting the dynamic strength model of rock to four types of rocks. The MAPEs of the theoretical and experimental strength values of the rock dynamic strength model are 9.85%, 10.72%, 5.14% and 7.48%, respectively; while the MAPEs of the theoretical and experimental strength values of the existing rock dynamic strength criterion are 16.84%, 29.76%, 30.72% and 26.30%, respectively; by comparing the fitting data of the four groups, the accuracy of the confining pressure-strain rate coupled rock dynamic strength criterion (rock dynamic strength model) proposed in this application is 65% higher than that of the traditional model, indicating that the proposed dynamic strength criterion can well estimate the dynamic strength of rock in a wide range of confining pressure and strain rate.

[0073] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to necessarily being implemented using the above specific details.

[0074] The system block diagrams referred to in this application are intended only as illustrative examples and are not intended to require or imply that the systems must be connected, arranged, or configured in the manner shown in the block diagrams. Words such as "including," "comprising," "having," and the like are open-ended words that mean "including but not limited to," and are used interchangeably therewith. The words "or" and "and" as used herein mean the words "and / or," and are used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" as used herein means the phrase "such as, but not limited to," and is used interchangeably therewith.

[0075] It should also be noted that in the apparatus, device, and method of the present application, each component or each step can be decomposed and / or recombined, and such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0076] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0077] The above description has been provided for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect, characterized in that: The method comprises: Based on the test data, the relationship between the confining pressure, strain rate and coupling coefficient is a power function relationship. The coupling coefficient is used to characterize the coupling effect between confining pressure and strain rate. Constructing a coupling effect model according to the coupling effect of the confining pressure and the strain rate and the power function relationship; Based on the confining pressure effect, strain rate effect and the coupling effect model, a rock dynamic strength model is constructed.

2. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to claim 1, characterized in that: The construction of the rock dynamic strength model based on the confining pressure effect, the strain rate effect and the coupling effect model includes: Confining pressure model is constructed based on the confining pressure effect ,in, is confining pressure; Constructing a strain rate model based on the strain rate effect ,in, is the strain rate; The rock dynamic strength model constructed according to the confining pressure model, the strain rate model and the coupling effect model is: ,in, is the dynamic triaxial compressive strength of rock, is the coupling effect model.

3. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to claim 2, characterized in that: ,in, is the coupling coefficient, is the coupling coefficient, is the coupling growth coefficient, is the unconfined compressive strength of rock, is the characteristic strain rate; The coupling effect model .

4. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to claim 2, wherein: ,in, is the maximum principal stress, is the unconfined compressive strength of rock, is the intact rock constant; The confining pressure model .

5. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to claim 2, wherein: ,in, is the dynamic growth factor, is the strain rate growth coefficient, is the characteristic strain rate; The strain rate model .

6. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to any one of claims 2 to 5, characterized in that: The rock dynamic strength model is: ,in, is the unconfined compressive strength of rock, is the intact rock constant, is the strain rate growth coefficient, is the characteristic strain rate, is the coupling coefficient, is the coupling growth coefficient.

7. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to claim 6, characterized in that: The method further comprises: Determined based on static uniaxial compression test data and static triaxial compression test data and the confining pressure model and ; Based on dynamic uniaxial compression test data, as well as Sure and ,in, is the dynamic growth factor, is the dynamic uniaxial compressive strength of rock; Based on the static uniaxial compression test data, the static triaxial compression test data, the dynamic uniaxial compression test data, the dynamic triaxial compression test data, the rock dynamic strength model, 、 、 and Sure and .

8. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to claim 6, characterized in that: The method further comprises: Determined based on static uniaxial compression test data and static triaxial compression test data and the confining pressure model and ; Based on dynamic uniaxial compression test data, as well as Sure and ,in, is the dynamic growth factor, is the dynamic uniaxial compressive strength of rock; based on 、 as well as Sure and .

9. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to claim 6, wherein: The rock dynamic strength model is used to characterize the rock dynamic strength under confining pressures ranging from 0 to 225 MPa and a strain rate of 10 -6 to 600s -1 Dynamic triaxial compressive strength of rock within.

10. The method for establishing a rock dynamic strength criterion based on the confining pressure-strain rate coupling effect according to any one of claims 2 to 5, characterized in that: The power function relationship between the confining pressure, strain rate and coupling coefficient obtained based on the test data includes: Drawing a plurality of stress-strain curves at different loading rates based on the test data, wherein any two stress-strain curves at different loading rates have different confining pressure conditions; Based on the stress-strain curves at different loading rates, a dynamic strength-strain rate logarithmic relationship curve under different confining pressures is obtained; Extracting the linear slope of the dynamic strength-strain rate logarithmic relationship curve under different confining pressures, and fitting to obtain a linear slope-confining pressure relationship curve, wherein the linear slope of the linear slope-confining pressure relationship curve is normalized; According to the linear slope-confining pressure relationship curve, it is determined that the relationship among the confining pressure, strain rate and coupling coefficient is a power function relationship.

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