A method for obtaining macro-mechanical parameters of rock mass based on wave-electricity cooperation

Abstract

The application discloses a kind of rock mass macro-mechanical parameter acquisition methods based on wave-electricity cooperation, it is related to rock mass mechanical parameter prediction technical field.The application steps are as follows: S1: according to rock mass process damage evolution analysis, and according to the integrity coefficient of rock mass, the physical index of rock mass quality and strength is reacted;S2: according to the longitudinal wave velocity of rock mass and the measured longitudinal wave velocity of rock mass in situ, the longitudinal wave velocity of rock mass is used instead of non-destructive rock wave velocity for analysis;S3: the key to determine rock mass mechanical parameter is to determine rock mass grade and structure surface category, considering rock mass joint and integrity condition, rock mass grade is determined in combination with GSI scoring method.The application determines rock mass integrity coefficient and damage variable by the detection of acoustic wave and resistivity and the combination of detection results, and determines rock mass strength and deformation parameter according to Hoek-Brown empirical criterion, and obtains the conversion relationship between rock mass and rock mass parameter based on GSI scoring standard in combination with rock mass damage analysis.

Description

Technical Field

[0001] This invention belongs to the field of rock mass mechanical parameter prediction technology, and in particular relates to a method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy. Background Technology

[0002] Engineering rock masses inevitably exist in a certain geological environment, and rock masses formed by geological movements are never absolutely intact. They always contain joints, fissures, and structural planes to varying degrees. How to determine the mechanical parameters of engineering rock masses is one of the hot issues in the geotechnical engineering field. Traditional methods for determining rock mass mechanical parameters include in-situ experimental methods, engineering analogy methods, and inversion analysis. These methods are often affected by differences in experience and human factors, and have limitations in actual engineering.

[0003] With the advancement of science and technology, geophysical exploration methods such as acoustic wave testing and resistivity testing have been continuously applied and developed in geotechnical engineering. Ultrasonic velocity and resistivity are both basic physical properties of rocks. In practical engineering such as geotechnical engineering and oil well logging, wave velocity and resistivity are often used to evaluate and characterize rock mass quality, water content, porosity, etc., and have a wide range of applications.

[0004] Under relatively stable operating conditions, the accumulation of damage within engineering rock masses follows certain patterns, with a relatively long stabilization period before failure. If the variation patterns of damage indicators during the stabilization period can be understood, cumulative damage analysis can be performed. The wave velocity and resistivity of rocks can not only reflect the changes in their internal microstructure well, but also quantitatively calculate internal damage. In other words, the wave-electric properties of rocks can more realistically reflect the relationship between microscopic damage and macroscopic parameters. The ultrasonic properties of rocks are closely related to the rock mass's own structure. The development of fissures is the main factor leading to differences in wave velocity within the rock mass, and the resistivity of rocks is also closely related to the pore structure. Analyzing the internal porosity and water content of rocks through the acoustic wave and resistivity characteristic parameters is complementary. Therefore, we designed a method for obtaining macroscopic mechanical parameters of rock masses based on wave-electric synergy. Summary of the Invention

[0005] The purpose of this invention is to provide a method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy, so as to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] This invention is a method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy.

[0008] The steps of this method are as follows:

[0009] S1: Based on the analysis of rock mass process damage evolution, and based on the rock mass integrity coefficient, physical indicators reflecting the quality and strength of the rock mass;

[0010] S2: Based on the on-site measurement of the longitudinal wave velocity of the rock block and the rock mass, the longitudinal wave velocity of the rock block is used to replace the non-destructive rock wave velocity for analysis;

[0011] S3: The key to determining the rock mass mechanical parameters is to determine the rock mass grade and structural plane category, taking into account the rock mass joints and integrity, combining the GSI scoring method to determine the rock mass grade, and comprehensively determining the structural plane status based on field investigation, geological exploration data and resistivity tests.

[0012] S4: The conversion relationship between rock mass and rock block parameters is obtained by correcting the results of statistical analysis of a large amount of measured data by Hoek-Brown and based on the GSI scoring standard.

[0013] Furthermore, the rock mass damage evolution in S1 is calculated by using in-situ and indoor rock mass wave velocity tests to determine wave velocity values ​​under different conditions, and an integrity coefficient K is introduced as appropriate. V .

[0014] Furthermore, a process damage evolution analysis of the rock mass is conducted by comprehensively considering porosity, water content, and regional characteristics. During the process damage analysis, the integrity coefficient K is calculated by comparing the measured wave velocity of the rock mass with the measured P-wave velocity of the rock block. V The calculation is performed using the following formula:

[0015]

[0016] In the formula, V Pm V represents the measured wave velocity of the rock mass. Pr The measured longitudinal wave velocity of the rock block.

[0017] The cumulative damage model study considered the influence of rock mass integrity on the cumulative damage rate, and the cumulative damage theoretical calculation considered 1-K. V Multiplier;

[0018] When using the crack density parameter f to characterize the development of internal fractures in a rock mass, the relationship between f and the rock mass integrity coefficient is as follows:

[0019] f = 1 - K V

[0020] Will Substitute into f = 1 - K V have to:

[0021]

[0022] Crack density can reflect the damage condition inside the rock mass.

[0023] Furthermore, the correction coefficient k1 in S2 can be calculated based on the measured resistivity, that is:

[0024]

[0025] If the rock has good integrity and low porosity, the wave velocity values ​​of ultrasonic waves passing through the rock block and the rock mass will be relatively similar.

[0026] Furthermore, the key to determining rock mass mechanical parameters in S3 is to determine the rock mass grade and structural plane category. Depending on the parameter selection, commonly used methods for determining the rock mass quality grade include: RMR classification method based on rock mass classification index, Q system classification method based on rock quality index, RQD classification method based on rock quality index, and GSI scoring method based on geological strength index. Considering the joint and integrity of the rock mass, the rock mass grade is determined by combining the GSI scoring method.

[0027] Based on the Hoek-Brown empirical criterion, rock mass strength and deformation parameters are determined. The earlier HB strength failure criterion is expressed as:

[0028]

[0029] In the formula: σ1 and σ2 are the maximum and minimum principal stresses (MPa) at rock failure; σ c denoted as uniaxial compressive strength (MPa); m is a material parameter, 0 < m ≤ 25;

[0030] Taking σ1=0 in the above formula, then σ3=σ t The expression for the tensile strength of the rock block can be obtained as follows:

[0031]

[0032] Analysis yielded the following expression for the Hoek-Brown material parameters, characterized by the ratio of tensile to compressive strength:

[0033]

[0034] Furthermore, considering the limitations of empirical criteria in practical engineering applications, Hoek-Brown continuously revised S4 based on statistical analysis of a large amount of measured data. The conversion formula between rock mass and rock block parameters, based on the GSI scoring standard, is as follows:

[0035]

[0036]

[0037]

[0038]

[0039]

[0040] Wherein, GSI is the geological strength index, and E m E represents the elastic modulus of the rock mass (MPa). i is the elastic modulus of the rock block (MPa); D is the construction disturbance factor, which is taken as 0-1 according to the on-site construction conditions; m b m i σ'1 and σ'3 are the Hoek-Brown constants for the rock mass and rock block, respectively; s and a are characteristic parameters of the rock mass; σ'1 and σ'3 are the maximum and minimum effective stresses (MPa) at failure; σ ci The uniaxial compressive strength of the rock block (MPa).

[0041] Furthermore, the rock mass is classified by integrity coefficient, and the structural plane is determined by combining field investigation, geological exploration data and resistivity testing technology. The predicted values ​​of rock mass parameters are then calculated by calculating the rock mass strength and deformation parameters.

[0042] The overall process first determines the longitudinal wave velocity of the rock mass based on the trans-hole ultrasonic testing method, then calculates the integrity coefficient by combining the longitudinal wave velocity of indoor rock block testing, and classifies the rock mass accordingly. Finally, the structural plane condition is determined by combining field investigation, geological exploration data and resistivity testing technology, and the predicted values ​​of rock mass parameters are calculated by calculating the rock mass strength and deformation parameters.

[0043] The present invention has the following beneficial effects:

[0044] This invention determines the rock mass integrity coefficient and damage variables by detecting acoustic waves and resistivity and combining the detection results. Based on the Hoek-Brown empirical criterion, it determines the rock mass strength and deformation parameters. At the same time, based on the GSI scoring standard, it obtains the conversion relationship between rock mass and rock block parameters. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of the method for obtaining macroscopic mechanical parameters of rock mass based on rock wave-electric synergy according to the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Please see Figure 1 As shown, the present invention is a method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy.

[0049] Damage is a continuous cumulative process. Combining empirical formulas and considering that acoustic or resistivity testing techniques can measure wave velocity or resistivity at a specific moment, the instantaneous damage to the rock mass at that moment can be calculated. After recording the instantaneous damage to the rock mass at a certain moment as the initial damage, analyzing the law of change in damage increment is an important aspect of dynamic analysis of cumulative damage. Under natural conditions, i.e., when n=0, the initial damage calculation formulas for various indicators are:

[0050]

[0051] In the formula, V Pf V represents the longitudinal wave velocity (m / s) of the undamaged rock. P(n＝0) E is the initial acoustic velocity of the rock (m / s); E0 is the elastic modulus of the undamaged rock; E (n＝0) D represents the elastic modulus of the rock in its initial state. E0 D V0 The initial damage variables are calculated based on the theoretical relationship between elastic modulus, longitudinal wave velocity and damage value, and on the basis of measured indicators.

[0052] When conducting process damage evolution analysis of rock mass, it is necessary to comprehensively consider porosity, water content, and regional characteristics. The integrity coefficient of rock mass reflects the physical indicators of rock mass quality and strength. In order to reflect the overall integrity of the rock mass under study, an integrity coefficient K based on the acoustic velocity is introduced when conducting process damage analysis. V :

[0053]

[0054] In the formula: V Pm V represents the measured wave velocity of the rock mass. Pr The measured longitudinal wave velocity of the rock block.

[0055] The cumulative damage model study considered the influence of rock mass integrity on the cumulative damage rate during the process, and the cumulative damage theoretical calculation considered (1-K) V () times coefficient.

[0056] When using the crack density parameter f to characterize the development of internal fractures in a rock mass, the relationship between f and the rock mass integrity coefficient is as follows:

[0057] f = 1 - K V (3)

[0058] (2) Substituting into (3), we get:

[0059]

[0060] In the formula: V Pm V represents the measured wave velocity of the rock mass. Pr The measured longitudinal wave velocity of the rock block.

[0061] Crack density can reflect the damage condition inside the rock mass. The theoretical relationship established by the above formula further illustrates that macro-micro damage analysis can be carried out based on the acoustic properties of the rock.

[0062] Because the P-wave velocities of rock blocks and the rock mass at the site can be measured in practice, and rock blocks have better integrity than the rock mass, the P-wave velocity of the rock blocks is used instead of the wave velocity of the undamaged rock in damage analysis. The effective damage variable for the rock mass is defined as follows: The expression:

[0063]

[0064] Furthermore, the formula for calculating the elastic modulus E is defined as follows:

[0065] D E =1-E / E0 (6)

[0066] Substituting (5) into (6) and introducing a correction coefficient k1 related to porosity, the relationship between the deformation modulus of the rock mass and the rock block can be established:

[0067]

[0068] Therefore, the strength conversion relationship between rock mass and rock block can be obtained:

[0069]

[0070] In the formula, k1 is a correction coefficient considering test error; V Pm V represents the measured wave velocity of the rock mass. Pr Measured P-wave velocity of the rock block; For the effective damage variable of the damaged material; σ represents the effective stress of the damaged material; σ represents the stress of the undamaged material.

[0071] Based on the relationship between resistivity and porosity in the Archie formula, and considering the water saturation of the pores, the correction factor k1 can be calculated based on the measured resistivity, i.e.:

[0072]

[0073] In the formula, R W R is the resistivity of the saturated solution; R is the resistivity of the unsaturated rock; S W The saturation level of unsaturated rocks.

[0074] If the rock has good integrity and low porosity, the wave velocity values ​​of ultrasonic waves passing through the rock block and the rock mass will be relatively similar.

[0075] The key to determining rock mass mechanical parameters is determining the rock mass grade and structural plane category. Depending on the parameter selection, commonly used methods for determining rock mass quality grades include: the RMR classification method based on rock mass classification indices, the Q system classification method based on rock quality indices, the RQD classification method based on rock quality indicators, and the GSI scoring method based on geological strength indices. Considering the joints and integrity of the rock mass, the rock mass grade is determined in conjunction with the GSI scoring method.

[0076] Based on the Hoek-Brown empirical criterion, rock mass strength and deformation parameters are determined. The earlier HB strength failure criterion is expressed as:

[0077]

[0078] In the formula: σ1 and σ2 are the maximum and minimum principal stresses (MPa) at rock failure; σ c denoted as uniaxial compressive strength (MPa); m is a material parameter, 0 < m ≤ 25.

[0079] Taking σ1=0 in the above formula, then σ3=σ t The expression for the tensile strength of the rock block can be obtained as follows:

[0080]

[0081] Analysis yielded the following expression for the Hoek-Brown material parameters, characterized by the ratio of tensile to compressive strength:

[0082]

[0083] Considering the limitations of empirical criteria in practical engineering applications, Hoek-Brown continuously revised the criteria based on statistical analysis of a large amount of measured data. Based on the GSI scoring standard, he derived the conversion formula between rock mass and rock block parameters, namely the generalized HB strength criterion:

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] Where GSI is the geological strength index, E m E represents the elastic modulus of the rock mass (MPa). i is the elastic modulus of the rock block (MPa); D is the construction disturbance factor, which is taken as 0-1 according to the on-site construction conditions; m b m i σ'1 and σ'3 are the Hoek-Brown constants for the rock mass and rock block, respectively; s and a are characteristic parameters of the rock mass; σ'1 and σ'3 are the maximum and minimum effective stresses (MPa) at failure; σ ci The uniaxial compressive strength of the rock block (MPa).

[0090] The advantages and effects of this invention are significant: by determining the rock mass integrity coefficient and damage variables, and combining this with laboratory tests, the Lemaitre strain equivalence hypothesis is used to assume the available effective stress. To describe the deformation behavior of damaged materials, damage variables can be introduced for calculation under damaged conditions, as shown in equation (18); based on Hooke's law (19) of the stress-strain relationship of one-dimensional undamaged elastic materials, keeping the strain ε constant, the stress σ can be expressed as the effective stress. Replace:

[0091] In the case of actual damage:

[0092] In the case of virtual lossless operation: ε=σ / E (19)

[0093] According to the strain equivalence assumption, substituting equation (18) into (19) yields the constitutive equation of the damaged material:

[0094]

[0095] After obtaining the relationship between the rock block and the rock mass parameters, the macroscopic mechanical parameters of the rock mass are predicted based on the theory of damage mechanics.

[0096] The present invention will be explained in more detail with reference to specific embodiments, but it should not be construed as limiting the main scope of the present invention to the following detection examples. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0097] The structural plane analysis first determines the longitudinal wave velocity of the rock mass based on the trans-hole ultrasonic testing method; then, it calculates the integrity coefficient by combining the longitudinal wave velocity of indoor rock blocks, and classifies the rock mass accordingly; finally, it determines the structural plane condition by combining field investigation, geological exploration data and resistivity testing technology.

[0098] Based on survey and measurement data, the relevant indicators of sandstone under natural conditions are shown in Table 1 below:

[0099] Table 1 Summary of rock block parameters in their natural state

[0100]

[0101] Based on the results in Table 1, we take K. V With GSI = 60, and without considering excavation disturbance, the rock mass strength and deformation parameters were calculated separately. The comparison of the calculation results based on wave-electric properties and the HB strength criterion is shown in Table 2.

[0102] Table 2 Comparison of predicted rock mass parameters

[0103]

[0104] As can be seen from the table, the calculated values ​​of rock mass parameters based on the wave electrical properties of rocks are close to the calculated values ​​of the classical HB strength criterion. Therefore, the method proposed in this patent can be used to predict the macroscopic mechanical parameters of rock mass.

[0105] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0106] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy, characterized in that, The steps are as follows: S1: Based on the analysis of rock mass process damage evolution, and based on the rock mass integrity coefficient, physical indicators reflecting the quality and strength of the rock mass; S2: Based on the on-site measurement of the longitudinal wave velocity of the rock block and the rock mass, the longitudinal wave velocity of the rock block is used to replace the non-destructive rock wave velocity for analysis; S3: The key to determining the rock mass mechanical parameters is to determine the rock mass grade and structural plane category, taking into account the rock mass joints and integrity, combining the GSI scoring method to determine the rock mass grade, and comprehensively determining the structural plane status based on field investigation, geological exploration data and resistivity tests. S4: Corrected by Hoek-Brown combined with statistical analysis of a large amount of measured data, and based on the GSI scoring standard, the conversion relationship between rock mass and rock block parameters is obtained; In S1, the damage evolution of the rock mass process is calculated by using in-situ and laboratory rock mass wave velocity tests to determine wave velocity values ​​under different conditions, and an integrity coefficient is introduced as needed. ; The process damage evolution analysis of the rock mass is carried out by comprehensively considering porosity, water content, and regional characteristics. During the process damage analysis, the integrity coefficient is calculated by comparing the measured wave velocity of the rock mass with the measured P-wave velocity of the rock block. The calculation is performed using the following formula: ; The cumulative damage model study considered the influence of rock mass integrity on the cumulative damage rate during the process, and the cumulative damage theoretical calculations considered... Multiplier; When using the crack density parameter f to characterize the development of internal fractures in a rock mass, the relationship between f and the rock mass integrity coefficient is as follows: ; Will Substitution have to: ; In the formula: The measured wave velocity of the rock mass; Measured P-wave velocity of the rock block; Crack density can reflect the damage condition inside the rock mass; S2 Lieutenant General Substitution Furthermore, a correction coefficient k1 related to porosity is introduced for correction, and the relationship between the deformation modulus of the rock mass and the rock block is established: ； The conversion relationship between the strength of rock mass and rock block is obtained: ； In the formula, To account for the correction factor for test error; The measured wave velocity of the rock mass; Measured P-wave velocity of the rock block; For the effective damage variable of the damaged material; The effective stress of the damaged material; For stress in non-destructive materials; Correction coefficient The conversion is based on the measured resistivity, that is: ; In the formula, The resistivity of the saturated solution; The resistivity of unsaturated rock; The degree of saturation of unsaturated rocks; If the rock has good integrity and low porosity, the wave velocity values ​​of ultrasonic waves passing through the rock block and the rock mass will be relatively similar.

2. The method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy according to claim 1, characterized in that, The key to determining the rock mass mechanical parameters in S3 is to determine the rock mass grade and structural plane category; Based on the Hoek-Brown empirical criterion, rock mass strength and deformation parameters are determined. The earlier HB strength failure criterion is expressed as: ; In the formula: and The maximum and minimum principal stresses at rock failure are given in MPa. denoted as uniaxial compressive strength of the rock block, in MPa; m is a material parameter. ; Take the above formula ,So The expression for the tensile strength of the rock block can be obtained as follows: ; Analysis yielded the following expression for the Hoek-Brown material parameters, characterized by the ratio of tensile to compressive strength: 。 3. The method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy according to claim 1, characterized in that, Considering the limitations of empirical criteria in practical engineering applications, Hoek-Brown continuously revised S4 based on statistical analysis of a large amount of measured data. The conversion formula between rock mass and rock block parameters, based on the GSI scoring standard, is as follows: ; ; ; ; ; GSI stands for Geological Strength Index. The elastic modulus of the rock mass is expressed in MPa. is the elastic modulus of the rock block, MPa; D is the construction disturbance factor, which is taken as 0-1 according to the on-site construction conditions. , are the Hoek-Brown constants for the rock mass and rock block, respectively; s and a are characteristic parameters of the rock mass. and The maximum and minimum effective stresses at failure are given in MPa. denoted as uniaxial compressive strength of the rock block, in MPa.

4. The method for obtaining macroscopic mechanical parameters of rock mass based on wave-electric synergy according to claim 1, characterized in that, The rock mass is classified by integrity coefficient, and the structural plane is determined by combining field investigation, geological exploration data and resistivity testing technology. The predicted values ​​of rock mass parameters are then calculated by calculating the rock mass strength and deformation parameters.

Images