A method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing

Abstract

The present invention discloses a method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing, comprising: dividing the sandy grade of sandy dolomite into two categories: first-class sandy grade and second-class sandy grade; testing the first-class sandy grade dolomite using a first in-situ testing method to obtain a first in-situ testing result; determining the uniaxial compressive strength of the first-class sandy grade dolomite rock mass according to the first in-situ testing result; and / or testing the second-class sandy grade dolomite using a second in-situ testing method to obtain a second in-situ testing result; determining the uniaxial compressive strength of the second-class sandy grade dolomite rock mass according to the second in-situ testing result. Compared with the traditional indoor test method, the present invention has less disturbance to the rock mass, the test instrument is easy to carry, can better reflect the actual situation of the engineering site, and is more representative.

Description

Technical Field

[0001] The invention relates to a method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing, and belongs to the technical field of geotechnical engineering and water conservancy and hydropower engineering. Background Art

[0002] Dolomite sandification refers to a special geological phenomenon in which the strength of the original dolomite in the stratum gradually decreases compared with the fresh and intact dolomite under the long-term and multi-stage internal and external dynamic geological effects, and the rock mass gradually breaks into fine sand, gravel or fragments. When constructing underground projects in sandy dolomite strata, they are often threatened by sudden geological disasters such as landslides and sudden water and sand inrush. As an important parameter in various rock mass projects, uniaxial compressive strength is widely used in various rock mass engineering construction and stability evaluation of rock slopes. Therefore, it is of great significance to efficiently and reasonably obtain the uniaxial compressive strength of sandy dolomite of different grades at the engineering site for the design and arrangement of prevention and control measures in engineering construction.

[0003] In the process of obtaining the uniaxial compressive strength of sandy dolomite of different grades, the traditional indoor test method is time-consuming and laborious. The test equipment is bulky and complicated to operate, and it is impossible to arrange the test facilities on site. At the same time, it is difficult to make the standard samples required for the test. It is impossible to make standard samples for dolomite with a high degree of sandification, and the transportation of the samples will cause the various indicators of the rock mass to change over time. It is impossible to fully simulate the occurrence state of sandy dolomite at the construction site, and it is impossible to obtain the uniaxial compressive strength of sandy dolomite of different grades in time. Therefore, it is urgent to establish a method that can efficiently and reasonably obtain the uniaxial compressive strength of sandy dolomite of different grades at the construction site. Summary of the invention

[0004] The present invention provides a method for obtaining the uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing, so as to obtain the uniaxial compressive strength of dolomite rock masses of two grades.

[0005] The technical solution of the present invention is:

[0006] According to one aspect of the present invention, a method for obtaining the uniaxial compressive strength of sandified dolomite of different grades based on in-situ testing is provided, comprising: dividing the sandification grade of the sandified dolomite into two categories: a first sandification grade and a second sandification grade; testing the first sandification grade dolomite using a first in-situ testing method to obtain a first in-situ testing result; determining the uniaxial compressive strength of the first sandification grade dolomite rock mass based on the first in-situ testing result; testing the second sandification grade dolomite using a second in-situ testing method to obtain a second in-situ testing result; determining the uniaxial compressive strength of the second sandification grade dolomite rock mass based on the second in-situ testing result.

[0007] The degree of sandification of the dolomite of the first sandification grade is less than that of the dolomite of the second sandification grade.

[0008] The method adopts a first in-situ test method to test the first type of sandy dolomite, obtains a first in-situ test result, and determines the uniaxial compressive strength of the first type of sandy dolomite rock mass according to the first in-situ test result, including: performing n point load tests and rebound tests on the first type of sandy dolomite within a test range; obtaining a size-corrected rock point load strength index I according to the point load test; s(50) ; Based on the size-corrected rock point load intensity index I s(50) Obtain the uniaxial compressive strength of rock mass based on point load strength; calculate the average uniaxial compressive strength UCS of rock mass based on point load strength according to multiple uniaxial compressive strength UCS1 of rock mass based on point load strength m1 ; Based on the rebound test, the rebound value obtained from each rebound test is obtained; Based on the rebound value, the uniaxial compressive strength UCS2 of the rock mass based on the rebound value is obtained; Based on multiple uniaxial compressive strengths UCS2 of the rock mass based on the rebound value, the average uniaxial compressive strength UCS of the rock mass based on the rebound value is calculated m2 ; Based on the average uniaxial compressive strength UCS based on the point load strength m1 , determine the first coefficient of variation A1; based on the average uniaxial compressive strength UCS based on the rebound value m2 , determine the second coefficient of variation A2; compare the first coefficient of variation A1 and the second coefficient of variation A2. If the two values ​​are different, the average uniaxial compressive strength corresponding to the coefficient of variation with a smaller result is used as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass; if the two values ​​are the same, the average uniaxial compressive strength corresponding to the first coefficient of variation A1 is selected as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass.

[0009] For point load test: take samples at n test positions within the test range, perform point load test, and obtain the effective point load strength index I s(50) , if the effective point load intensity index I s(50) If the number of sampling is less than 7, re-sampling shall be carried out from the original test positions of all failed rock samples; if the number of sampling is equal to 3 times, but the load intensity index I of all effective points is s(50) If the number is still less than 7, the test range only uses the average uniaxial compressive strength of the rock mass based on the rebound value obtained by the rebound test as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass.

[0010] UCS1 = 22.82·I s(50) 0.75 ; Among them, UCS1 is the uniaxial compressive strength of rock mass based on point load strength; I s(50)is the size-corrected rock point load strength index.

[0011] Said Among them, A1 is the first coefficient of variation; σ1 is the standard deviation of the uniaxial compressive strength UCS1 of the rock mass based on the point load strength; UCS m1 It is the average value of the uniaxial compressive strength UCS1 of the rock mass based on multiple point load strengths.

[0012] The UCS2=α·3.201·R-α46.59; wherein R is the rebound value; UCS2 is the uniaxial compressive strength of the rock mass based on the rebound value; and α is the correction coefficient.

[0013] Said Among them, A2 is the second coefficient of variation; σ2 is the standard deviation of the uniaxial compressive strength UCS2 of the rock mass based on the rebound value; UCS m2 It is the average value of multiple rock uniaxial compressive strength UCS2 based on rebound values.

[0014] The second in-situ test method is used to test the second type of sandy dolomite to obtain a second in-situ test result, and the uniaxial compressive strength of the second type of sandy dolomite rock mass is determined based on the second in-situ test result, including: performing a needle penetration test on the second type of sandy dolomite within a test range; and calculating the uniaxial compressive strength UCS3 of the rock mass based on the needle penetration ratio based on an average value of the obtained needle penetration ratio as the uniaxial compressive strength of the second type of sandy dolomite rock mass.

[0015] According to another aspect of the present invention, there is also provided a device for obtaining the uniaxial compressive strength of sandified dolomite of different grades based on in-situ testing, comprising: a classification module for dividing the sandification grade of the sandified dolomite into two categories: a first sandification grade and a second sandification grade; a first determination module for testing the first sandification grade dolomite using a first in-situ testing method to obtain a first in-situ testing result; and determining the uniaxial compressive strength of the first sandification grade dolomite rock mass based on the first in-situ testing result; and / or a second determination module for testing the second sandification grade dolomite using a second in-situ testing method to obtain a second in-situ testing result; and determining the uniaxial compressive strength of the second sandification grade dolomite rock mass based on the second in-situ testing result.

[0016] The beneficial effects of the present invention are as follows: the testing equipment involved in the present invention is easy to carry and can be quickly carried out at the engineering site; specifically, the present invention divides the sandification grade of sandy dolomite into two categories, and adopts different in-situ testing methods for the two categories; further, the coefficient of variation is introduced to measure the degree of variation of the results of the uniaxial compressive strength of sandy dolomite of different grades estimated by the point load test and the rebound test; compared with the traditional qualitative empirical method, the influence on the rock mass disturbance is small, the testing instrument is easy to carry, can better reflect the actual situation of the engineering site, and is more representative. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flowchart of an embodiment of the present invention;

[0018] Figure 2 It is a schematic diagram of an irregular specimen;

[0019] Figure 3 Schematic diagram of the measurement position before and after sample failure. DETAILED DESCRIPTION

[0020] The invention is further described below in conjunction with the accompanying drawings and embodiments, but the content of the invention is not limited to the scope of the embodiments.

[0021] Example 1: Figure 1-3 As shown, a method for obtaining the uniaxial compressive strength of sandified dolomite of different grades based on in-situ testing includes: dividing the sandification grade of the sandified dolomite into two categories: a first sandification grade and a second sandification grade; testing the first sandification grade dolomite using a first in-situ testing method to obtain a first in-situ testing result; determining the uniaxial compressive strength of the first sandification grade dolomite rock mass based on the first in-situ testing result; and / or testing the second sandification grade dolomite using a second in-situ testing method to obtain a second in-situ testing result; determining the uniaxial compressive strength of the second sandification grade dolomite rock mass based on the second in-situ testing result.

[0022] Optionally, the sandification degree of the dolomite of the first sandification grade is less than that of the dolomite of the second sandification grade.

[0023] Optionally, the first in-situ test method is used to test the first type of sandy dolomite to obtain a first in-situ test result, and the uniaxial compressive strength of the first type of sandy dolomite rock mass is determined according to the first in-situ test result, including: performing n point load tests and rebound tests on the first type of sandy dolomite within a test range; obtaining a size-corrected rock point load strength index I according to the point load test; s(50) ; Based on the size-corrected rock point load intensity index I s(50)Obtain the uniaxial compressive strength of rock mass based on point load strength; calculate the average uniaxial compressive strength UCS of rock mass based on point load strength according to multiple uniaxial compressive strength UCS1 of rock mass based on point load strength m1 ; Based on the rebound test, the rebound value obtained from each rebound test is obtained; Based on the rebound value, the uniaxial compressive strength UCS2 of the rock mass based on the rebound value is obtained; Based on multiple uniaxial compressive strengths UCS2 of the rock mass based on the rebound value, the average uniaxial compressive strength UCS of the rock mass based on the rebound value is calculated m2 ; Based on the average uniaxial compressive strength UCS based on the point load strength m1 , determine the first coefficient of variation A1; based on the average uniaxial compressive strength UCS based on the rebound value m2 , determine the second coefficient of variation A2; compare the first coefficient of variation A1 and the second coefficient of variation A2. If the two values ​​are different, the average uniaxial compressive strength corresponding to the coefficient of variation with a smaller result is used as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass; if the two values ​​are the same, the average uniaxial compressive strength corresponding to the first coefficient of variation A1 is selected as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass.

[0024] Optionally, for point load test: sampling is performed at n test positions within the test range, and point load test is performed to obtain the effective point load strength index I s(50) , if the effective point load intensity index I s(50) If the number of sampling is less than 7, re-sampling shall be carried out from the original test positions of all failed rock samples; if the number of sampling is equal to 3 times, but the load intensity index I of all effective points is s(50) If the number is still less than 7, the test range only uses the average uniaxial compressive strength of the rock mass based on the rebound value obtained by the rebound test as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass.

[0025] Optionally, the UCS1=22.82·I s(50) 0.75 ; Among them, UCS1 is the uniaxial compressive strength of rock mass based on point load strength; I s(50) is the size-corrected rock point load strength index.

[0026] Optionally, the Among them, A1 is the first coefficient of variation; σ1 is the standard deviation of the uniaxial compressive strength UCS1 of the rock mass based on the point load strength; UCS m1 It is the average value of the uniaxial compressive strength UCS1 of the rock mass based on multiple point load strengths.

[0027] Optionally, UCS2=α·3.201·R-α46.59, wherein R is the rebound value; UCS2 is the uniaxial compressive strength of the rock mass based on the rebound value; and α is the correction coefficient.

[0028] Optionally, the Among them, A2 is the second coefficient of variation; σ2 is the standard deviation of the uniaxial compressive strength UCS2 of the rock mass based on the rebound value; UCS m2 It is the average value of multiple rock uniaxial compressive strength UCS2 based on rebound values.

[0029] Optionally, the second in-situ testing method is used to test the second type of sandification grade dolomite to obtain a second in-situ test result, and the uniaxial compressive strength of the second type of sandification grade dolomite rock mass is determined based on the second in-situ test result, including: performing a needle penetration test on the second type of sandification grade dolomite within the test range; and calculating the uniaxial compressive strength UCS3 of the rock mass based on the needle penetration ratio based on an average value of the obtained needle penetration ratio as the uniaxial compressive strength of the second type of sandification grade dolomite rock mass.

[0030] Furthermore, an optional implementation manner of the present invention is described below.

[0031] Specifically: the six grades of dolomite sandification are divided into two categories: the first grade of sandification and the second grade of sandification.

[0032] Step 1: Selection of the field test range of sandy dolomite and determination of the sandification grade of dolomite within the range, specifically including the following steps:

[0033] First, the test range is selected at the project site according to the construction plan and site layout, and the test range is numbered and recorded. Then, the sandy dolomite within the field test range is graded based on the geological survey data, design data and construction data. The sandy dolomite is graded into six levels: slightly sandy, weakly sandy lower section, weakly sandy upper section, strongly sandy lower section, strongly sandy upper section, and severely sandy. It should be noted that other sandy grade classification methods can also be used to grade the sandy dolomite. According to the results of the classification, it is divided into two categories. The degree of sandification of dolomite that meets the first sandy grade is less than that of dolomite that meets the second sandy grade.

[0034] Step 2: Select the corresponding in-situ test method according to the results of different dolomite sandification grades and select a representative in-situ test location within the field test range, which specifically includes the following steps:

[0035] Since point load test can easily destroy the strongly sandified upper section and severely sandified dolomite specimens, and rebound test can easily cause the surface of the test area to break, making it impossible to obtain values, a needle penetrometer is introduced to conduct needle penetration test on the strongly sandified upper section and severely sandified dolomite. At the same time, in order to avoid the breakage of the penetration needle during the needle penetration test, the slightly sandified, weakly sandified lower section, weakly sandified upper section and strongly sandified lower section are not involved in the needle penetration test. It should be noted that if other grading methods are used to divide the sandy dolomite grades, the breakage of the penetration needle is used as the boundary condition, and all sandification levels higher than the boundary of the break point are regarded as the second type of sandification grades.

[0036] Point load tests and rebound tests were conducted within the test range for slightly sandy, weakly sandy lower section, weakly sandy upper section and strongly sandy lower section dolomite. 21 point load tests and rebound tests were conducted within the test range, for a total of 42 in-situ tests. 42 positions uniformly selected in the test range according to 6×7 were used as representative in-situ test positions. The selected positions were numbered and recorded. The in-situ test conducted at each position was different from the in-situ tests conducted at the four surrounding positions, that is, if a point load test was conducted at a certain position, the four surrounding positions were all rebound tested (taking the 6×7 area as an example, the point load test area and the rebound test area were arranged alternately up and down, left and right. For example, the first column was alternating from top to bottom according to the point load test area and the rebound test area, and the second column was alternating from top to bottom according to the rebound test area and the point load test area; in this way, the 6 columns were arranged alternately from left to right in the first column and the second column).

[0037] For the strongly sandified upper section and severely sandified dolomite, needle penetration tests were carried out within the test range. The test range was divided into 9 test areas according to the shape of a "well", and 3 to 10 needle penetration tests were carried out in each test area.

[0038] Step 3: Conduct in-situ testing based on the results of dolomite sandification classification, including the following steps:

[0039] 1. The first in-situ test method test:

[0040] Point load tests were conducted at 21 representative in-situ test locations for slightly sandy, weakly sandy lower, weakly sandy upper, and strongly sandy lower dolomites. The result calculation formulas were based on the relevant formulas in the Test Procedures for Physical and Mechanical Properties of Rocks (DZ / T0276.1-2015) and the Engineering Rock Classification Standard (GB50218 / T-2014). Rebound tests were conducted at the remaining 21 representative in-situ test locations.

[0041] First, rock blocks are collected at representative in-situ test locations to make samples. Each group of samples should have uniform size and the same water content. The samples are properly processed to make them approximately cubic in shape. Their length (L), width (W), and height (H) are measured. The samples are described on the record sheet, including their number, size, color, sampling location, and degree of sandification. Because no fine processing is performed when samples are collected on site, all samples are considered irregular specimens. Irregular specimens such as Figure 2 The present invention is the first to simultaneously introduce three in-situ test technologies into the estimation of uniaxial compressive strength of sandy dolomite of different grades, effectively making up for the disadvantage of the difficulty in making standard specimens for traditional standard indoor rock mechanics tests.

[0042] For irregular dolomite block specimens, the length (L), width (W), and height (H) of the specimen should satisfy L ≥ W ≥ H, with the average width W of the specimen perpendicular to the line connecting the loading points on the failure surface being f The sample height is generally controlled between 25 mm and 100 mm instead of the sample width W. Calculate the average width W of the dolomite sample on the failure surface perpendicular to the line connecting the loading points f , the average width W of the specimen failure surface perpendicular to the line connecting the loading points f Calculate as follows:

[0043]

[0044] Where: W f It is the average width of the line perpendicular to the loading point on the failure surface of the specimen, in mm; W1 is the width of the upper end of the minimum cross-section of the specimen through the loading point, in mm; W2 is the width of the lower end of the minimum cross-section of the specimen through the loading point, in mm.

[0045] Check whether the upper and lower loading cones of the point load tester are accurately aligned, place the sample between the cones, make the loading cones closely contact the shortest side direction of the sample, i.e. the H direction, and make the contact point as close to the center of the sample as possible. When loading the point load tester, the middle part of the rock sample should be trimmed so that it is not too uneven or tilted.

[0046] Load the sample at a uniform speed that can cause the sample to fail within 10s to 60s until the sample fails, and record the sample failure load P. If the failure surface only passes through one loading point, local failure will occur and the test will be considered invalid. Figure 3 The distance D′ between the loading points at the moment of sample failure is measured. D′ is the distance between the loading points at the moment of sample failure after the upper and lower cone ends penetrate, and the unit is millimeter (mm).

[0047] Calculation of equivalent circle diameter D of irregular dolomite specimen e , equivalent circle diameter D eCalculate as follows:

[0048]

[0049] Where: D e is the equivalent circle diameter, in mm; W f It is the average width of the line perpendicular to the loading points on the failure surface of the specimen, in mm; D′ is the distance between the loading points at the moment of specimen failure, in mm.

[0050] Calculation of the uncorrected rock point load strength index I for dolomite s , uncorrected rock point load intensity index I s Calculate as follows:

[0051]

[0052] Where: I s is the uncorrected rock point load strength index, in MPa; P is the specimen failure load, in kN; D e is the equivalent circle diameter, in mm.

[0053] Calculate the irregular sample size correction factor f of dolomite. The irregular sample size correction factor f is calculated according to the following formula:

[0054]

[0055] Where: f is the correction coefficient; m is the correction index, which is determined by the empirical value of the same type of rock and is generally taken as 0.4 to 0.45. In this method, based on the measured data, the P~(D e ) 2 Relationship diagram, and use the graphical method to determine m is 0.45; D e is the equivalent circle diameter, in mm.

[0056] Calculation of the size-corrected point load strength index I of dolomite s(50) , the corrected point load intensity index I s(50) Calculate as follows:

[0057] I s(50) =f×I s

[0058] Where: I s(50) is the rock point load strength index after size correction, in MPa; f is the correction factor; I s It is the uncorrected rock point load strength index, in MPa.

[0059] Rebound tests were carried out on the remaining 21 representative in-situ test locations within the test range of slightly sandy dolomite, weakly sandy lower section, weakly sandy upper section and strongly sandy upper section. First, 21 rebound tests were carried out at the representative in-situ test locations. When conducting the rebound test, the rebound hammer was kept perpendicular to the rock surface of the representative in-situ test location. If the rock surface at the test location was rough and undulating, it was trimmed without damaging the dolomite rock mass. Then a rebound test was carried out to ensure that all 21 test locations had a rebound value R. Finally, the rebound value R obtained from each rebound test was recorded.

[0060] 2. Second in-situ test method test:

[0061] For the strongly sandified upper section and the severely sandified dolomite, needle penetration tests were carried out in the 9 divided areas. According to the on-site test conditions, representative areas with relatively flat bedding planes and uniform properties were selected in the 9 areas for in-situ needle penetration tests. Before the test, loose parts on the surface were removed with a geological hammer or other tools, and the test area was leveled. Then 3 to 10 needle penetration tests were carried out, and the test points were spaced more than 10 mm apart. The needle penetrometer model used in this method is the soft rock needle penetrometer SH-70 produced by Maruta Seisakusho Co., Ltd. of Japan. When conducting the needle penetration test on site, first place the penetration needle. Take out the penetration needle in the back cover, remove the presser and loosen the chuck, insert the penetration needle into the chuck and tighten it, then scratch the presser along the notch of the presser, and then scratch the end of the presser to the "0" penetration scale, and at the same time scratch the indicator ring along the back cover to the end, so that the penetration force returns to "0";

[0062] During the penetration test, keep the presser vertical to the test point. When any of the following two conditions is met, the test can be stopped and data recorded. If the penetration amount D is greater than 10mm or the penetration force F is greater than 100N due to improper operation, the test data should be discarded.

[0063] Case 1: When the penetration D scale reaches 10mm but the penetration force F has not yet reached 100N;

[0064] Case 2: When the penetration force F reaches 100N but the penetration amount D has not yet reached 10mm.

[0065] Eliminate invalid data (large discreteness), record the penetration amount and penetration force of each penetration test, and when cracks occur on the rock surface during penetration, the test data should be discarded. However, when cracks occur when the penetration needle is pulled out, the data at this point is valid.

[0066] After the test, the needle penetration ratio NPI is calculated according to the penetration volume D and the penetration force F. The needle penetration ratio NPI is calculated as follows:

[0067] When D = 10mm, F ≤ 100N; NPI = F / 10;

[0068] Where: F is the penetration force, unit is N; NPI is the needle penetration ratio, unit is N / mm.

[0069] When F=100N, D≤10mm; NPI=100 / D;

[0070] Where: D is the penetration amount, unit is mm; NPI is the needle penetration ratio, unit is N / mm.

[0071] Finally, the average value of the needle penetration ratio NPI of the strongly sandy upper section and the severely sandy dolomite is calculated. m .

[0072] Step 4: Calculation of uniaxial compressive strength of sandy dolomite of different grades, including the following steps:

[0073] 1. Uniaxial compressive strength of the first type of sandy grade dolomite rock mass:

[0074] For slightly sandy, weakly sandy lower section, weakly sandy upper section, and strongly sandy lower section dolomite, on the basis of collecting and collating point load test data, the uniaxial compressive strength UCS1 of the rock mass based on the point load strength within the dolomite test range is calculated by formula. The uniaxial compressive strength UCS1 is calculated as follows:

[0075] UCS1=22.82·I s(50) 0.75

[0076] Where: UCS1 is the uniaxial compressive strength of rock mass based on point load strength, in MPa; I s(50) It is the rock point load strength index after size correction, in MPa.

[0077] Point load tests were performed on 21 specimens, and the test failure data were eliminated. After the test failure data were eliminated, the final effective point load strength index I s(50) When the number is greater than or equal to 16, the 3 highest and 3 lowest values ​​are deleted, and the above formula is used to calculate the uniaxial compressive strength UCS1 of the rock mass based on the point load strength within the dolomite test range. Based on multiple uniaxial compressive strengths UCS1 of the rock mass based on the point load strength, the average uniaxial compressive strength UCS of the rock mass based on the point load strength is calculated. m1 , the result is rounded to 3 significant figures. After eliminating the test failure data, the final effective point load intensity index I s(50) When the number is greater than or equal to 7 and less than 16, only one highest value and one lowest value are deleted, and the remaining data are regarded as the final effective point load intensity index I s(50) , using the final effective point load intensity index Is(50) Calculate the uniaxial compressive strength UCS1 of the rock mass based on the point load strength and calculate the average uniaxial compressive strength UCS m1 , the result is rounded to 3 significant figures; if the test failure data is removed, the final effective point load intensity index I s(50) When the number is greater than 0 and less than 7, the existing point load intensity index I is retained. s(50) , resample from the original sampling position of all failed rock samples, number them and conduct point load test. If the sampling number is equal to 3 times, but all the point load strength index I s(50) If the number is still less than 7, the uniaxial compressive strength value is estimated using only the rebound test in this test range.

[0078] Based on multiple size-corrected rock point load intensity indices I s(50) The average value of the uniaxial compressive strength of the rock mass within the dolomite test range is calculated to determine the coefficient of variation A1, which is calculated as follows:

[0079]

[0080] Where: A1 is the coefficient of variation; σ1 is the standard deviation of the uniaxial compressive strength UCS1 of the rock mass based on the point load strength, in MPa; UCS m1 It is the average value of the uniaxial compressive strength UCS1 of the rock mass based on multiple point load strengths, in MPa.

[0081] On the basis of the rebound test data, the uniaxial compressive strength UCS2 of the rock mass based on the rebound value in the test range of slightly sandy, weakly sandy lower section, weakly sandy upper section and strongly sandy lower section is calculated by formula. The uniaxial compressive strength UCS2 is calculated as follows:

[0082] UCS2=α·3.201·R-α46.59

[0083] Where: R is the rebound value; UCS2 is the uniaxial compressive strength of the rock mass based on the rebound value, in MPa; α is the correction coefficient, which is taken as 0.5 in this method according to the difference between sandy dolomite and fresh intact dolomite.

[0084] The 21 rebound test results were sorted, and the remaining rebound values ​​after removing the 3 highest and 3 lowest values ​​were regarded as the final effective rebound value R. The final effective rebound value R was used to calculate the uniaxial compressive strength UCS2 of the rock mass based on the rebound value within the dolomite test range, and the average uniaxial compressive strength UCS of the rock mass based on the rebound value was calculated based on multiple uniaxial compressive strengths UCS2 of the rock mass based on the rebound value. m2 , the result is rounded to 3 significant figures.

[0085] The coefficient of variation A2 is determined based on the average value of the uniaxial compressive strength of the rock mass within the dolomite test range calculated based on multiple rebound values ​​R. The coefficient of variation A2 is calculated as follows:

[0086]

[0087] Where: A2 is the coefficient of variation; σ2 is the standard deviation of the uniaxial compressive strength UCS2 of the rock mass based on the rebound value, in MPa; UCS m2 It is the average value of multiple rock uniaxial compressive strength UCS2 based on rebound values, in MPa.

[0088] Compare the size of the coefficient of variation A1 and A2. When A1 is less than or equal to A2, use multiple size-corrected rock point load intensity indexes I s(50) Calculated average uniaxial compressive strength UCS of dolomite within the test range m1 represents the uniaxial compressive strength of the sandy dolomite within the test range of the sandy dolomite; when A2 is less than A1, multiple rebound values ​​R m Calculated average uniaxial compressive strength UCS of dolomite within the test range m2 Represents the uniaxial compressive strength of sandy dolomite within the test range of this sandy dolomite.

[0089] 2. Uniaxial compressive strength of the second type of sandy grade dolomite rock mass:

[0090] For the strongly sandy upper section and severely sandy dolomite, the uniaxial compressive strength UCS3 of the rock mass within the dolomite test range is calculated by formula arrangement. The uniaxial compressive strength UCS3 is calculated as follows:

[0091] logUCS3=0.978logNPI m +2.621

[0092] Where: NPI m The value is the average value of needle penetration ratio NPI, in N / mm; UCS3 value is uniaxial compressive strength, in MPa.

[0093] Through the above steps, the experimental data are given as follows:

[0094] (1) Xiaopu 2# branch cave (initially judged to be weakly sandy)

[0095] Table 1

[0096]

[0097] Table 2

[0098]

[0099] Table 3

[0100]

[0101] Table 4

[0102]

[0103] It can be seen from Tables 1 to 4 above that the average value of 41.685 MPa corresponding to the coefficient of variation of 0.173 is selected as the uniaxial compressive strength of the dolomite rock mass.

[0104] (2) Xiaopu 2# branch cave (preliminary judgment: severe sandification)

[0105] Table 5

[0106]

[0107] It can be seen from Table 5 that the uniaxial compressive strength of the dolomite rock mass is 1.190 MPa.

[0108] Embodiment 2: A device for obtaining the uniaxial compressive strength of sandified dolomite of different grades based on in-situ testing, comprising: a classification module, which divides the sandification grade of the sandified dolomite into two categories: a first sandification grade and a second sandification grade; a first determination module, which is used to test the first sandification grade dolomite using a first in-situ testing method to obtain a first in-situ testing result; and determine the uniaxial compressive strength of the first sandification grade dolomite rock mass based on the first in-situ testing result; and / or a second determination module, which is used to test the second sandification grade dolomite using a second in-situ testing method to obtain a second in-situ testing result; and determine the uniaxial compressive strength of the second sandification grade dolomite rock mass based on the second in-situ testing result.

[0109] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0110] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0111] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing, characterized in that: include: The sandification grade of sandy dolomite is divided into two categories: the first sandification grade and the second sandification grade; A first in-situ test method is used to test the first type of sandy dolomite to obtain a first in-situ test result; based on the first in-situ test result, the uniaxial compressive strength of the first type of sandy dolomite rock mass is determined; The second in-situ test method is used to test the second type of sandy dolomite to obtain the second in-situ test results; based on the second in-situ test results, the uniaxial compressive strength of the second type of sandy dolomite rock mass is determined; The sandification degree of the dolomite of the first sandification grade is less than that of the dolomite of the second sandification grade; The first in-situ test method is used to test the first type of sandy dolomite to obtain a first in-situ test result, and the uniaxial compressive strength of the first type of sandy dolomite rock mass is determined according to the first in-situ test result, including: For the first type of sandy grade dolomite, point load test and rebound test were carried out n times within the test range; Based on the point load test, the rock point load strength index I after size correction is obtained s(50) ; Based on the size-corrected rock point load intensity index I s(50) Obtain the uniaxial compressive strength of rock mass based on point load strength; calculate the average uniaxial compressive strength UCS of rock mass based on point load strength according to multiple uniaxial compressive strength UCS1 of rock mass based on point load strength m1 ; According to the rebound test, the rebound value obtained from each rebound test is obtained; according to the rebound value, the uniaxial compressive strength UCS2 of the rock mass based on the rebound value is obtained; according to multiple uniaxial compressive strengths UCS2 of the rock mass based on the rebound value, the average uniaxial compressive strength UCS of the rock mass based on the rebound value is calculated m2 ; Based on the average uniaxial compressive strength UCS based on the point load strength m1 , determine the first coefficient of variation A1; based on the average uniaxial compressive strength UCS based on the rebound value m2 , determine the second coefficient of variation A2; Compare the first coefficient of variation A1 and the second coefficient of variation A2. If the two coefficients are different, the average uniaxial compressive strength corresponding to the coefficient of variation with the smaller result is used as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass; if the two coefficients are the same, the average uniaxial compressive strength corresponding to the first coefficient of variation A1 is selected as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass; The second in-situ test method is used to test the second type of sandy dolomite to obtain a second in-situ test result, and the uniaxial compressive strength of the second type of sandy dolomite rock mass is determined based on the second in-situ test result, including: performing a needle penetration test on the second type of sandy dolomite within a test range; and calculating the uniaxial compressive strength UCS3 of the rock mass based on the needle penetration ratio based on an average value of the obtained needle penetration ratio as the uniaxial compressive strength of the second type of sandy dolomite rock mass.

2. The method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing according to claim 1 is characterized in that: For point load test: take samples at n test positions within the test range, perform point load test, and obtain the effective point load strength index I s(50) , if the effective point load intensity index I s(50) If the number is less than 7, re-sampling shall be carried out from the original test positions of all failed rock samples; If the number of sampling is equal to 3 times, but all effective point load intensity index I s(50) If the number is still less than 7, the test range only uses the average uniaxial compressive strength of the rock mass based on the rebound value obtained by the rebound test as the uniaxial compressive strength of the first type of sandification grade dolomite rock mass.

3. The method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing according to claim 1 is characterized in that: UCS1 = 22.82·I s(50) 0.75 ; Among them, UCS1 is the uniaxial compressive strength of rock mass based on point load strength; I s(50) is the size-corrected rock point load strength index.

4. The method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing according to claim 1 is characterized in that: Said Among them, A1 is the first coefficient of variation; σ1 is the standard deviation of the uniaxial compressive strength UCS1 of the rock mass based on the point load strength; UCS m1 It is the average value of the uniaxial compressive strength UCS1 of the rock mass based on multiple point load strengths.

5. The method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing according to claim 1, characterized in that: The UCS2=α·3.201·R-α46.59; wherein R is the rebound value; UCS2 is the uniaxial compressive strength of the rock mass based on the rebound value; and α is the correction coefficient.

6. The method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing according to claim 1, characterized in that: Said Among them, A2 is the second coefficient of variation; σ2 is the standard deviation of the uniaxial compressive strength UCS2 of the rock mass based on the rebound value; UCS m2 It is the average value of multiple rock mass uniaxial compressive strength UCS2 based on rebound values.

7. A device for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing, used in the method for obtaining uniaxial compressive strength of sandy dolomite of different grades based on in-situ testing as claimed in claim 1, characterized in that: include: The division module divides the sandification grade of sandy dolomite into two categories: the first sandification grade and the second sandification grade; A first determination module is used to test the first type of sandy dolomite using a first in-situ test method to obtain a first in-situ test result; and determine the uniaxial compressive strength of the first type of sandy dolomite rock mass according to the first in-situ test result; The second determination module is used to test the second type of sandy dolomite using a second in-situ test method to obtain a second in-situ test result; and determine the uniaxial compressive strength of the second type of sandy dolomite rock mass based on the second in-situ test result.

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