A method for determining rock mass disturbance coefficient under freezing-thawing and mining disturbance

Abstract

This invention belongs to the field of geotechnical engineering technology, specifically disclosing a method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance effects. The method involves selecting rock samples from high-altitude and cold regions, screening them using ultrasonic waves, and grouping and numbering them; after drying the numbered rock samples, the porosity is tested. P 0 and uniaxial compressive strength σ c0 Test the saturated P-wave velocity of rock samples after vacuum saturation treatment. V p0 Rock samples subjected to vacuum saturation treatment were subjected to different numbers of freeze-thaw cycles; the porosity of the rock samples after different numbers of freeze-thaw cycles was measured. P N Longitudinal wave velocity V pN and uniaxial compressive strength σ cN Rock samples with different freeze-thaw cycles were subjected to true triaxial unloading tests to measure different initial confining pressure values. σ 3 and target unloading confining pressure σ Confining pressure at failure of rock sample at 3' σ d The rock mass disturbance coefficient is defined based on data obtained from pre- and post-freeze-thaw tests and unloading tests. D The present invention is characterized by low computational complexity, a scientifically sound process, and accurate and reliable results.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, specifically relating to a method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance effects, which involves minimal calculation, a scientifically sound process, and accurate and reliable results. Background Technology

[0002] In cold-region mining, water conservancy, transportation, and municipal engineering projects, rock masses are often subjected to the dual effects of freeze-thaw cycles and mining disturbances, which significantly deteriorates their mechanical properties and integrity. The rock mass disturbance coefficient D, an important parameter in the Hoek-Brown empirical criterion, reflects the degree of disturbance to the rock mass under natural geological conditions caused by engineering activities. It is used to describe the differences in mechanical properties (such as strength and elastic modulus) and structural integrity between disturbed and undisturbed rock masses.

[0003] In the Hoek-Brown empirical criterion, the rock mass disturbance coefficient D The value range of is 0 to 1: where, when D When = 0, it indicates that the rock mass is undisturbed; while when D When the value is 1, it indicates that the rock mass is completely disturbed. Currently, due to the rock mass disturbance coefficient... D The determination of the perturbation coefficient lacks precise theoretical basis and relies solely on limited practical experience. Therefore, how to achieve the perturbation coefficient through relevant experimental methods remains a challenge. D Quantitative characterization of rocks has always been a key focus of research in the field of rock engineering. In particular, rocks in high-altitude and cold regions are more strongly affected by the disturbances caused by engineering activities such as blasting and mechanical vibration during mining after experiencing freeze-thaw cycles.

[0004] In existing technologies, many scholars mainly use the wave velocity of the rock before and after disturbance to define the rock mass disturbance coefficient. D However, since rock is an anisotropic material, the perturbation coefficient cannot be calculated from a single scale. DThis results in significant dispersion. To address this, a CT image and 3D reconstruction technique has been developed, combining CT image sequences from freeze-thaw-disturbance coupled tests with the Black Top-Hat algorithm to enhance crack features and achieve 3D visualization and reconstruction of internal rock mass damage. While this technique can non-destructively acquire the 3D structure of the rock mass, accurately quantify parameters such as porosity and crack aperture, reveal the self-similarity of damage evolution, and achieve spatial resolution up to the micrometer level, enabling the identification of initial microcracks, it also suffers from drawbacks such as high equipment costs, limited rock sample size, complex data processing, and difficulty in simulating real-world stress environments. Furthermore, an SHPB coupled test system based on a freeze-thaw cycle and dynamic disturbance coupled loading system using a freeze-thaw-confining pressure loading system, a controllable high-frequency pendulum impact system, a two-sided hydraulic propulsion system, and a multi-channel high-speed data acquisition system has been developed. While the aforementioned technology innovatively integrates freeze-thaw, confining pressure, and high-frequency disturbance modules to achieve multi-field coupled simulation, and the pendulum impact system can precisely control disturbance parameters (frequency, amplitude, number of impacts), and can directly output dynamic stress-strain curves for easy calculation of disturbance coefficients, it also suffers from several drawbacks: the patented equipment is not yet widely available (exclusively at Shenzhen University), high-cycle testing is time-consuming (>10,000 impacts require several hours), and low-amplitude signal noise interference is significant. Secondly, there is the integrated ultrasonic and borehole camera observation technology, which uses ultrasonic wave velocity to invert the rock mass integrity index and combines it with borehole camera footage to identify fracture development; and the microseismic monitoring technology, which uses sensor networks to capture acoustic emission signals generated by rock mass fractures, locate damage sources, and calculate energy release rates. These two in-situ monitoring technologies also have limitations, such as the inability of the integrated ultrasonic and borehole camera observation technology to distinguish the independent effects of freeze-thaw and mining disturbances, and the susceptibility of microseismic monitoring technology to environmental noise interference, requiring complex data processing. Additionally, there are issues related to the introduction of damage variables. D Describing fracture density, combined with the permeability coefficient evolution equation ( k = k 0 e αD This method utilizes numerical simulation techniques to quantify the seepage-damage coupling effect, creating a damage mechanics model. While its theoretical framework is rigorous and can reveal microscopic mechanisms, it faces challenges in parameter inversion, requiring experimental verification.

[0005] Therefore, current research focuses on the rock mass disturbance coefficient under the coupled effects of freeze-thaw cycles and mining in high-altitude and cold regions. D There is still a lack of a method that yields accurate results and has a scientifically sound process for determining the [specific parameters]. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance effects, which involves minimal computation, a scientifically sound process, and yields accurate and reliable results.

[0007] The method for determining the rock mass disturbance coefficient under the effects of freeze-thaw cycles and mining disturbances of the present invention is implemented as follows: it includes the steps of rock sample collection, pre-freeze-thaw testing, pre-freeze-thaw treatment, freeze-thaw treatment, post-freeze-thaw treatment, unloading test, and defining the disturbance coefficient. The specific contents of each step are as follows: A. Rock sample collection: Select rock samples from high-altitude and cold regions, then use an ultrasonic velocity tester to screen qualified rock samples, and then group and number the qualified rock samples. B. Pre-freeze-thaw test: The previously numbered rock samples were first dried, then cooled to room temperature, and the porosity of the dried rock samples was then tested and recorded. P 0 and uniaxial compressive strength s c0 ; C. Pre-freeze-thaw treatment: The rock sample is subjected to vacuum saturation treatment, and then the saturated P-wave velocity of the treated rock sample is tested. V p0 ; D. Freeze-thaw treatment: The rock samples that have undergone vacuum saturation treatment are subjected to freeze-thaw cycles of different numbers; E. Post-freeze-thaw treatment: Porosity of rock samples after different preset freeze-thaw cycles N was tested. P N Longitudinal wave velocity V pN and uniaxial compressive strength s cN ; F. Unloading Test: Rock samples that have reached the preset number of freeze-thaw cycles N are subjected to a true triaxial unloading test to measure different initial confining pressure values. s 3 and target unloading confining pressure value s Confining pressure at failure of rock sample at 3' s d ; G. Define the disturbance coefficient: Based on the rock sample data obtained before and after freeze-thaw cycles and from true triaxial unloading tests, define the rock mass disturbance coefficient. D The formula for calculating ' is: In the formula: K The rock damage coefficient under freeze-thaw and mining disturbance is derived from the freeze-thaw damage factor. D f With unloading damage factor D d Sure: in: In the formula: D f1 , D f2 , D f3 These are the strength damage factor, wave velocity damage factor, and microstructure damage factor of freeze-thawed rocks, respectively.

[0008] Furthermore, in step F, the initial confining pressure value for the true triaxial unloading test is set according to the actual stress level at the construction site. s 3 With the target unloading confining pressure value s 3', then test with the same initial confining pressure value. s 3. Confining pressure values ​​at rock sample failure s d .

[0009] Furthermore, in step F, the confining pressure value before rock mining unloading is selected as the initial confining pressure value. s 3. Select the confining pressure value after rock mining unloading as the target unloading confining pressure value. s 3'.

[0010] Furthermore, in step A, the target rock sample is taken from the same fresh and intact rock in a typical rock stratum at a high-altitude cold region engineering site. All rock samples are cut and polished into the same size shape and structure along the original rock stratum direction. Then, rock samples with visual defects or joint differences are first removed, followed by rock samples with large density differences. Then, rock samples with large wave velocity differences are removed using ultrasonic velocity detection. Finally, the remaining qualified rock samples are grouped and numbered.

[0011] Furthermore, in step A, the height, diameter, and mass of the rock sample are measured to calculate the density of the rock sample, and rock samples with large density differences are discarded; the ultrasonic velocity of the rock sample is measured using a non-metallic ultrasonic detector, and rock samples with large wave velocity differences are discarded.

[0012] Further, in step B, the drying process involves placing the numbered rock samples in a vacuum drying oven, drying them at a constant temperature of 105–110°C for 24–48 hours, and weighing the rock samples. The drying process continues, and the weight of the rock samples is weighed every 12 hours until the weight of the rock samples no longer changes.

[0013] Furthermore, in step B, at least three rock samples that have been dried and cooled to room temperature are selected for uniaxial compressive strength testing, and the average value of the data obtained from the three rock sample tests is calculated as the uniaxial compressive strength of the rock sample. sc0 .

[0014] Further, in step C, the dried rock sample is first placed in a dried vacuum saturation device, then a vacuum pump is used to evacuate the device to 0.05–0.20 MPa and maintain the pressure for 5 hours. Then, the water injection valve is slowly opened, maintaining the vacuum level within the device during the water injection process. Distilled water is forced into the vacuum saturation device using atmospheric pressure until it completely submerges the rock sample, after which the valve is closed. The evacuation is then stopped, and the sample is allowed to stand for 36 hours. Finally, the saturated longitudinal wave velocity of the rock sample is measured. V p0 .

[0015] Furthermore, in step D, firstly, based on the average winter temperature and average temperature of other seasons in the selected rock sample location over the past 20 years, the freezing and thawing temperatures of the automatic freeze-thaw cycler are set; secondly, the freezing time is determined according to the "Standard for Test Methods of Engineering Rock Mass GB / T 50266-2013"; and finally, the preset number of freeze-thaw cycles N is determined based on the importance of the rock engineering.

[0016] Further, in step E, before testing the rock samples, the rock samples that have reached the preset number of freeze-thaw cycles N are first dried; for rock samples that have undergone different numbers of freeze-thaw cycles N, at least three samples with the same number of freeze-thaw cycles N are selected for uniaxial compressive strength testing, and then the average value of the data obtained from each rock sample test is calculated as the uniaxial compressive strength of the rock sample with the corresponding number of freeze-thaw cycles N. s cN .

[0017] The present invention has the following beneficial effects: 1. This invention innovatively introduces multi-dimensional damage factor coupling, through the strength before and after freeze-thaw ( s c0 and s cN ), longitudinal wave velocity ( V p0 and V pN ), porosity ( P 0 and P N ), calculate the intensity damage factor respectively D f1 Wave velocity damage factor D f2 Microstructural damage factor D f3 And synthesized into a freeze-thaw damage factor through formula (3). D f Then, combining the true triaxial unloading test data (initial confining pressure) s 3 , breaking the confining pressure s d Calculate the unloading damage factor D d Finally, the comprehensive damage coefficient K is coupled through formula (2), and then substituted into formula (1) to obtain the rock mass disturbance coefficient. D′ Therefore, by using multi-parameter collaborative quantification, compared with traditional empirical methods and single evaluation methods to determine the rock mass disturbance coefficient, it not only avoids the one-sidedness of a single index, but also effectively overcomes the problem of inaccurate calculation results caused by rock anisotropy, significantly reduces the dispersion of the results, improves the reliability of the results, and makes the rock mass disturbance coefficient D′ more consistent with the actual damage state of the rock mass.

[0018] 2. To address the problem that existing in-situ monitoring technologies (such as ultrasound and microseismic monitoring) struggle to distinguish between the individual effects of freeze-thaw cycles and mining disturbances, leading to ambiguity in the physical meaning of the disturbance coefficient, this invention achieves decoupling through step-by-step testing and comparative analysis. Specifically, it quantifies the damage to the rock mass caused by different freeze-thaw cycles (N times) during the freeze-thaw treatment stage. D f This eliminates mining disturbance interference; while in the true triaxial unloading test, mining disturbance (confining pressure unloading) is applied to "rock samples subjected to preset freeze-thaw cycles," and the damage caused by unloading is quantified separately. D d ); and finally clarified through formula (2) D f and D d The coupling relationship between freeze-thaw cycles and mining disturbances was revealed, demonstrating a synergistic effect. This achievement marks the first time that "independent quantification and coupled analysis" of freeze-thaw cycles and mining disturbances has been realized, providing a theoretical basis for "targeted prevention and control of certain types of disturbances" in cold-region engineering.

[0019] 3. Given that existing technologies suffer from high equipment costs (such as CT 3D reconstruction, SHPB coupling system), patent exclusivity (such as Shenzhen University pendulum system), or complex operation (such as microseismic data processing), they are difficult to promote in ordinary engineering projects. This invention not only relies on conventional rock mechanics equipment such as vacuum drying oven, freeze-thaw cycle machine, uniaxial / true triaxial testing machine, and ultrasonic detector for core testing, without the need for special customization, thus lowering the hardware threshold; moreover, the process from rock sample collection to unloading test strictly follows the "Standard for Engineering Rock Mass Testing Methods GB / T 50266-2013", with strong reproducibility and easy for engineers to master; and the rock mass disturbance coefficient is directly calculated through clear formulas (1) to (5). D′ This avoids the complex three-dimensional reconstruction of CT technology or the noise filtering of microseismic monitoring, and reduces the reliance on professional data processing capabilities.

[0020] 4. Existing indoor tests often neglect real-world stress conditions (e.g., freeze-thaw tests lack confining pressure, and SHPB is difficult to simulate on-site unloading paths), leading to large deviations between the disturbance coefficient and actual engineering conditions. This invention optimizes the stress environment through precise simulation: during the freeze-thaw treatment stage, freezing / thawing temperatures are set based on nearly 20 years of temperature data from the engineering site to ensure freeze-thaw damage is consistent with the on-site environment; then, a true triaxial unloading test is conducted using the "confining pressure before mining unloading" as the initial confining pressure. s 3 The target unloading confining pressure is "the confining pressure after mining unloading". s 3′ It accurately reproduces the stress path during the mining process, thus ensuring that the final results closely match the actual stress environment on site and enhancing the engineering guidance.

[0021] 5. Existing technologies, such as CT 3D reconstruction equipment, are costly, and SHPB high-cycle testing is time-consuming, making it difficult to meet the practical needs of large-scale engineering testing. This invention addresses these issues through a low-cost, high-efficiency process design: for example, by abandoning high-cost equipment and using conventional testing instruments, the testing cost per set of rock samples can be effectively reduced; the number of freeze-thaw cycles N can be flexibly set according to the importance of the project (not forcing high cycles), and the duration of a single true triaxial unloading test is relatively short, thus significantly shortening the testing cycle; and standardized screening of rock sample collection and pretreatment (density, wave velocity, and appearance defects removal) ensures the consistency of rock samples, thereby reducing repeated tests and further improving efficiency. Ultimately, this significantly reduces testing costs and time, facilitating large-scale application.

[0022] In summary, this invention integrates methods for evaluating the degree of rock freeze-thaw damage and the degree of damage from mining unloading, and establishes the first freeze-thaw-unloading coupled damage model. K = D f + D d This research fills a gap in the study of multi-disturbance synergistic mechanisms. Through technological innovations such as "multi-dimensional damage coupling, decoupling of disturbance factors, on-site stress simulation, and low cost and easy operation," it effectively solves the problems of discrete results, ambiguous mechanisms, equipment dependence, and poor engineering applicability in existing technologies. It provides an accurate, reliable, and easily promoted technical solution for determining the rock mass disturbance coefficient under the coupling effect of freeze-thaw and mining in high-altitude and cold regions, and has important guiding significance for the stability assessment and safety design of mines, tunnels, and other projects in cold regions. Attached Figure Description

[0023] Figure 1 This is a flowchart of the method for determining the rock mass disturbance coefficient under the effects of freeze-thaw cycles and mining disturbances according to the present invention. In the diagram: S100 - Rock sample collection, S200 - Pre-freeze-thaw test, S300 - Pre-freeze-thaw treatment, S400 - Freeze-thaw treatment, S500 - Post-freeze-thaw treatment, S600 - Unloading test, S700 - Define disturbance coefficient. Figure 2 The rock mass disturbance coefficients under different unloading confining pressures in the examples are shown. D The fitted curve of the functional relationship between ' and the number of freeze-thaw cycles N. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this does not limit the present invention in any way. Any changes or improvements made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0025] like Figure 1 As shown, the method for determining the rock mass disturbance coefficient under the effects of freeze-thaw cycles and mining disturbances of the present invention includes the following steps: rock sample collection, pre-freeze-thaw testing, pre-freeze-thaw treatment, freeze-thaw treatment, post-freeze-thaw treatment, unloading test, and definition of the disturbance coefficient. The specific contents of each step are as follows: A. Rock sample collection: Select rock samples from high-altitude and cold regions, then use an ultrasonic velocity tester to screen qualified rock samples, and then group and number the qualified rock samples. B. Pre-freeze-thaw test: The previously numbered rock samples were first dried, then cooled to room temperature, and the porosity of the dried rock samples was then tested and recorded. P 0 and uniaxial compressive strength s c0 ; C. Pre-freeze-thaw treatment: The rock sample is subjected to vacuum saturation treatment, and then the saturated P-wave velocity of the treated rock sample is tested. V p0 ; D. Freeze-thaw treatment: The rock samples that have undergone vacuum saturation treatment are subjected to freeze-thaw cycles of different numbers; E. Post-freeze-thaw treatment: Porosity of rock samples after different preset freeze-thaw cycles N was tested. P N Longitudinal wave velocity V pN and uniaxial compressive strength s cN ; F. Unloading Test: Rock samples that have reached the preset number of freeze-thaw cycles N are subjected to a true triaxial unloading test to measure different initial confining pressure values. s 3 and target unloading confining pressure value s Confining pressure at failure of rock sample at 3' s d ; G. Define the disturbance coefficient: Based on the rock sample data obtained before and after freeze-thaw cycles and from true triaxial unloading tests, define the rock mass disturbance coefficient. D The formula for calculating ' is: In the formula: K The rock damage coefficient under freeze-thaw and mining disturbance is derived from the freeze-thaw damage factor. D f With unloading damage factor D d Sure: in: In the formula: D f1 , D f2 , D f3 These are the strength damage factor, wave velocity damage factor, and microstructure damage factor of freeze-thawed rocks, respectively.

[0026] In step F, the initial confining pressure value for the true triaxial unloading test is set according to the actual stress level at the construction site. s 3. Target unloading confining pressure value s 3', then test with the same initial confining pressure value. s 3. Confining pressure values ​​at rock sample failure s d .

[0027] In step F, the confining pressure value before rock mining unloading is selected as the initial confining pressure value. s 3. Select the confining pressure value after rock mining unloading as the target unloading confining pressure value. s 3'.

[0028] In step A, the target rock sample is taken from the same fresh and intact rock in a typical rock stratum at a high-altitude cold region engineering site. All rock samples are cut and polished into the same size and shape along the original rock stratum direction. Then, rock samples with visual defects or joint differences are first removed, followed by rock samples with large density differences. Then, rock samples with large wave velocity differences are removed by ultrasonic detection. Finally, the remaining qualified rock samples are grouped and numbered.

[0029] In step A, all rock samples are cut and polished into cylinders with a height of 100 mm and a diameter of 50 mm.

[0030] In step A, rock samples with wave velocities between 2700 and 3100 m / s and no obvious surface cracks are selected as qualified rock samples.

[0031] In step A, the height, diameter, and mass of the rock sample are measured to calculate the density of the rock sample, and rock samples with large density differences are discarded; the ultrasonic velocity of the rock sample is measured using a non-metallic ultrasonic detector, and rock samples with a longitudinal wave velocity difference exceeding 400 m / s are discarded.

[0032] In step A, rock samples with large density differences are removed according to GB / T 50266-2013 "Standard for Test Methods of Engineering Rock Mass": samples with a density range exceeding 5% of the average value or a coefficient of variation (standard deviation / average value) greater than 3% are removed from the same group of rock samples.

[0033] In step B, the drying process involves placing the numbered rock samples in a vacuum drying oven, drying them at a constant temperature of 105–110°C for 24–48 hours, and weighing the rock samples. The drying process continues, and the weight of the rock samples is weighed every 12 hours until the weight of the rock samples no longer changes.

[0034] In step B, at least three rock samples that have been dried and cooled to room temperature are selected for uniaxial compressive strength testing, and the average value of the data obtained from the three rock sample tests is calculated as the uniaxial compressive strength of the rock sample. s c0 .

[0035] In step C, the dried rock sample is first placed in a dry vacuum saturation device. Then, a vacuum pump is used to evacuate the device to 0.05–0.20 MPa and maintain the pressure for 5 hours. Subsequently, the water injection valve is slowly opened, and the vacuum level inside the device is kept constant during the water injection process. Distilled water is forced into the vacuum saturation device by atmospheric pressure until it completely submerges the rock sample. The valve is then closed, the evacuation is stopped, and the sample is left to stand for 36 hours. Finally, the saturated longitudinal wave velocity of the rock sample is measured. V p0 .

[0036] In step D, firstly, based on the average winter temperature and average temperature of other seasons in the selected rock sample location over the past 20 years, the freezing and thawing temperatures of the automatic freeze-thaw cycler are set. Secondly, the freezing time is determined according to the "Standard for Test Methods of Engineering Rock Mass GB / T 50266-2013". Finally, the preset number of freeze-thaw cycles N is determined based on the importance of the rock engineering.

[0037] In step D, the number of preset freeze-thaw cycles N is determined based on the importance of the rock engineering: the number of preset freeze-thaw cycles is determined comprehensively based on the engineering safety level, the severity of the engineering environment, and the rock properties; when there are no specific requirements for the engineering, the number of freeze-thaw cycles for Class I rock mass tests in GB / T 502013 "Standard for Test Methods of Rock Mass in Engineering" shall be followed.

[0038] In step E, before testing the rock samples, the rock samples that have reached the preset number of freeze-thaw cycles N are dried. For rock samples that have undergone different numbers of freeze-thaw cycles N, at least three samples with the same number of freeze-thaw cycles N are selected for uniaxial compressive strength testing. The average value of the data obtained from each rock sample test is then calculated as the uniaxial compressive strength of the rock sample with the corresponding number of freeze-thaw cycles N. s cN .

[0039] Example

[0040] Using data from Wang Chengxiang's dissertation "Study on Damage Characteristics and Loading / Unloading Mechanical Behavior of Sandstone under Freeze-Thaw Cycles" as an example, the method for determining the disturbance coefficient of rock mass under freeze-thaw and mining disturbance effects of this invention is adopted to determine the disturbance coefficient D' of the corresponding rock mass. The process is as follows.

[0041] S100: Select a fresh, intact rock from a typical rock stratum at a high-altitude, cold-region engineering site. Cut and grind it along the original stratum into several standard cylindrical rock samples with a base diameter of 50 mm and a height of 100 mm. Then, first, remove rock samples with visual defects or joint differences. Next, measure the mass of the rock samples and calculate the density of the rock samples based on the aforementioned dimensions. Remove samples from the same group whose density range exceeds 5% of the average value, or whose coefficient of variation (standard deviation / average value) is greater than 3%. Then, use a non-metallic ultrasonic detector to test the ultrasonic velocity of the rock samples. Remove rock samples with a longitudinal wave velocity range exceeding 400 m / s and obvious surface cracks. Preferably, select rock samples with a wave velocity between 2700 and 3100 m / s and no obvious surface cracks as qualified rock samples. Finally, group and number the qualified rock samples.

[0042] S200: Place the previously numbered rock samples in a vacuum drying oven, then dry them at a constant temperature of 105–110℃ for 24–48 hours and weigh the rock samples. Continue drying and weigh the rock samples every 12 hours until the weight of the rock samples no longer changes (accuracy of 0.001g) to complete the drying process. Then cool to room temperature, and then test and record the porosity of the dried rock samples. P 0 and uniaxial compressive strength s c0 At least three rock samples, after being dried and cooled to room temperature, were selected for uniaxial compressive strength testing. The average value of the data obtained from the three rock sample tests was calculated as the uniaxial compressive strength of the rock sample. s c0 .

[0043] S300: Place the previously dried rock sample into a dry vacuum saturation cylinder, then use a vacuum pump to evacuate the cylinder to 0.05–0.20 MPa and maintain the pressure for 5 hours. Next, slowly open the water injection valve, maintaining a constant vacuum level within the cylinder during the water injection process. Use atmospheric pressure to force distilled water into the vacuum saturation cylinder until the rock sample is completely submerged, then close the valve. Stop evacuating and allow the sample to stand for 36 hours. Finally, measure the saturated longitudinal wave velocity of the rock sample. V p0 .

[0044] S400: Based on the average winter temperature and other season average temperatures of the selected rock sample location over the past 20 years, first set the freezing temperature of the automatic freeze-thaw cycler to -30℃ and the thawing temperature to 30℃; then, according to the "Standard for Test Methods of Engineering Rock Mass GB / T 50266-2013", determine the freezing time to be 4 hours and the thawing time to be 4 hours; subsequently, select the number of freeze-thaw cycles as 0, 20, 40, and 60 times respectively, based on the importance of the rock engineering; finally, place the vacuum-saturated rock sample into the automatic freeze-thaw cycler and perform freeze-thaw cycle treatment according to the aforementioned parameters.

[0045] S500: First, the rock sample that has reached the preset number of freeze-thaw cycles N is dried. Then, the porosity of the rock sample after different preset number of freeze-thaw cycles N is tested. P N Longitudinal wave velocity V pN Among them, at least three rock samples with the same number of freeze-thaw cycles N are selected for uniaxial compression tests. The average uniaxial compressive strength of the three rock samples is then calculated as the uniaxial compressive strength of the rock sample after N freeze-thaw cycles. s cN .

[0046] S600: Extract rock samples that have reached the preset number of freeze-thaw cycles N, and select the confining pressure value of 10 MPa before rock mining unloading as the initial confining pressure value. s 3. The confining pressure value of 0 MPa after mining and unloading is taken as the target unloading confining pressure value. s 3', Conduct a true triaxial unloading test: A constant axial pressure was used to unload the confining pressure. The axial stress was applied to 70% of the peak compressive strength of the rock sample under a confining pressure of 10 MPa using a stress-controlled method. The confining pressure was then applied to the test set value of 10 MPa, and then unloaded until the rock sample failed. The confining pressure value at the time of rock sample failure was recorded. s d .

[0047] G700: Define the rock mass disturbance coefficient based on rock sample data obtained before and after freeze-thaw cycles and from true triaxial unloading tests. D The formula for calculating ' is: In the formula: K The rock damage coefficient under freeze-thaw and mining disturbance is derived from the freeze-thaw damage factor. D f With unloading damage factor D d Sure: in:

[0048] In the formula: D f1 , D f2 , D f3 These are the strength damage factor, wave velocity damage factor, and microstructure damage factor of freeze-thawed rocks, respectively.

[0049] like Figure 1 As shown, based on the aforementioned data, a fitting curve of the functional relationship between the rock mass disturbance coefficient D' and the number of freeze-thaw cycles N under different unloading confining pressures is plotted.

[0050] The basic parameters in the embodiments are shown in Table 1, and the calculated data of the rock mass disturbance coefficient D' are shown in Table 2.

[0051] Table 1. Rock damage data from freeze-thaw-unloading tests

[0052] Table 2 Calculation data of rock mass disturbance coefficient D'

[0053] analyze: Based on the calculation results of the rock mass disturbance coefficient D' in Tables 1 and 2, the following plots are drawn: Figure 2 The linear fitting curve shown is derived from... Figure 2 It can be known that R 2 =0.99, the linear fitting result is very good, which verifies the feasibility of the method.

[0054] comprehensive Figure 2 As shown in Tables 1 and 2, the defined rock mass disturbance coefficient D' comprehensively considers the strength damage, wave velocity damage, microstructure damage and unloading damage generated by the rock during freeze-thaw cycles and mining. It can predict the rock mass structure disturbance and damage under freeze-thaw and mining operations at different cycle numbers, and the error is small, with high accuracy.

[0055] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance effects, characterized in that: The process includes rock sample collection, pre-freeze-thaw testing, pre-freeze-thaw treatment, freeze-thaw treatment, post-freeze-thaw treatment, unloading test, and definition of disturbance coefficients. The specific details of each step are as follows: A. Rock sample collection: Select rock samples from high-altitude and cold regions, then use an ultrasonic velocity tester to screen qualified rock samples, and then group and number the qualified rock samples. B. Pre-freeze-thaw test: The previously numbered rock samples were first dried, then cooled to room temperature, and the porosity of the dried rock samples was then tested and recorded. P 0 and uniaxial compressive strength σ c0 ; C. Pre-freeze-thaw treatment: The rock sample is subjected to vacuum saturation treatment, and then the saturated P-wave velocity of the treated rock sample is tested. V p0 ; D. Freeze-thaw treatment: The rock samples that have undergone vacuum saturation treatment are subjected to freeze-thaw cycles of different numbers; E. Post-freeze-thaw treatment: Porosity of rock samples after different preset freeze-thaw cycles N was tested. P N Longitudinal wave velocity V pN and uniaxial compressive strength σ cN ; F. Unloading Test: Rock samples that have reached the preset number of freeze-thaw cycles N are subjected to a true triaxial unloading test to measure different initial confining pressure values. σ 3 and target unloading confining pressure value σ Confining pressure at failure of rock sample at 3' σ d ; G. Define the disturbance coefficient: Based on the rock sample data obtained before and after freeze-thaw cycles and from true triaxial unloading tests, define the rock mass disturbance coefficient. D The formula for calculating ' is: In the formula: K The rock damage coefficient under freeze-thaw and mining disturbance is derived from the freeze-thaw damage factor. D f With unloading damage factor D d Sure: in: In the formula: D f1 , D f2 , D f3 These are the strength damage factor, wave velocity damage factor, and microstructure damage factor of freeze-thawed rocks, respectively.

2. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 1, characterized in that: In step F, the initial confining pressure value for the true triaxial unloading test is set according to the actual stress level at the construction site. σ 3. Target unloading confining pressure value σ 3', then test with the same initial confining pressure value. σ 3. Confining pressure values ​​at rock sample failure σ d .

3. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 2, characterized in that: In step F, the confining pressure value before rock mining unloading is selected as the initial confining pressure value. σ 3. Select the confining pressure value after rock mining unloading as the target unloading confining pressure value. σ 3'.

4. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 1, characterized in that: In step A, the target rock sample is taken from the same fresh and intact rock in a typical rock stratum at a high-altitude cold region engineering site. All rock samples are cut and polished into the same size and shape along the original rock stratum direction. Then, rock samples with visual defects or joint differences are first removed, followed by rock samples with large density differences. Then, rock samples with large wave velocity differences are removed by ultrasonic detection. Finally, the remaining qualified rock samples are grouped and numbered.

5. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 4, characterized in that: In step A, the height, diameter, and mass of the rock sample are measured to calculate the density of the rock sample, and rock samples with large density differences are discarded; the ultrasonic velocity of the rock sample is measured using a non-metallic ultrasonic detector, and rock samples with a longitudinal wave velocity difference exceeding 400 m / s are discarded.

6. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 1, characterized in that: In step B, the drying process involves placing the numbered rock samples in a vacuum drying oven, drying them at a constant temperature of 105–110°C for 24–48 hours, and weighing the rock samples. The drying process continues, and the weight of the rock samples is weighed every 12 hours until the weight of the rock samples no longer changes.

7. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 6, characterized in that: In step B, at least three rock samples that have been dried and cooled to room temperature are selected for uniaxial compressive strength testing, and the average value of the data obtained from the three rock sample tests is calculated as the uniaxial compressive strength of the rock sample. σ c0 .

8. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 1, characterized in that: In step C, the dried rock sample is first placed in a dry vacuum saturation device. Then, a vacuum pump is used to evacuate the device to 0.05–0.20 MPa and maintain the pressure for 5 hours. Subsequently, the water injection valve is slowly opened, and the vacuum level inside the device is kept constant during the water injection process. Distilled water is forced into the vacuum saturation device by atmospheric pressure until it completely submerges the rock sample. The valve is then closed, the evacuation is stopped, and the sample is left to stand for 36 hours. Finally, the saturated longitudinal wave velocity of the rock sample is measured. V p0 .

9. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance as described in claim 1, characterized in that: In step D, firstly, based on the average winter temperature and average temperature of other seasons in the selected rock sample location over the past 20 years, the freezing and thawing temperatures of the automatic freeze-thaw cycler are set. Secondly, the freezing time is determined according to the "Standard for Test Methods of Engineering Rock Mass GB / T50266-2013". Finally, the preset number of freeze-thaw cycles N is determined based on the importance of the rock engineering.

10. The method for determining the rock mass disturbance coefficient under freeze-thaw and mining disturbance effects according to any one of claims 1 to 9, characterized in that: In step E, the rock sample that has reached the preset number of freeze-thaw cycles N is dried before the rock sample is tested. For rock samples subjected to different freeze-thaw cycles N, at least three samples with the same number of freeze-thaw cycles N were selected for uniaxial compressive strength testing. The average value of the data obtained from each rock sample test was then calculated as the uniaxial compressive strength of the rock sample with the corresponding number of freeze-thaw cycles N. σ cN .

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