A DC electrical testing and evaluation method for underground tunnel support stability

Abstract

The present invention discloses a direct current electrical method for testing and evaluating the stability of underground tunnel support, including: before the tunnel is developed and supported, a plurality of measuring lines are evenly arranged around the tunnel to test the resistivity information of the original structure of the surrounding rock before support; drilling is performed on the area with abnormal resistivity of the surrounding rock to determine and identify its geological information such as cracks and water content; with the resistivity information of the original structure of the surrounding rock as the background, after the tunnel is supported, the resistivity information of the surrounding rock is regularly tested according to a preset cycle, and the resistivity gradient and resistivity change rate of the surrounding rock are calculated; based on the resistivity test and drilling results, the stability of the tunnel structure is evaluated. The technical solution of the present invention tests the resistivity of the tunnel by direct current electrical method to obtain the surrounding rock structure information, can identify the hidden geological defects of the tunnel surrounding rock, and then evaluate the stability of the surrounding rock, and has a good prediction ability for the possible tunnel disaster incubation process, thereby improving the accuracy of the tunnel stability evaluation.

Description

Technical Field

[0001] The invention relates to the technical field of geophysical detection of tunnel support stability, and in particular to a direct current electrical testing and evaluation method for underground tunnel support stability. Background Art

[0002] In the process of tunnel development, tunnel stability is the fundamental guarantee for the safety of development and mining, and monitoring its stability is the main basis for judging its stability.

[0003] The coal rock mass is full of cracks, which will further expand under the disturbance of tunnel development, thus causing tunnel deformation and even inducing dynamic disasters. At present, tunnel stability monitoring mainly relies on observing whether there are cracks on the tunnel surface, whether the support is deformed, or monitoring by stress gauges. The monitoring method is relatively simple and the monitoring range is small. It cannot meet the requirements of regional testing and deep coal seam monitoring, and the ability to identify internal defects of the surrounding rock around the tunnel is weak.

[0004] Therefore, there is an urgent need for a monitoring method with a wide monitoring range and a large testing depth to identify and determine the fracture fields, water-containing areas, stress concentration areas, etc. around the tunnel, and then conduct a reliability evaluation of the stability of the tunnel support. Summary of the invention

[0005] The present invention provides a direct current electrical method for testing and evaluating the stability of underground tunnel support, aiming to identify changes in the surrounding rock structure around the tunnel through the direct current electrical method, a regional testing means; to solve the technical problems that the existing monitoring methods are relatively single, the monitoring range is small, and they cannot meet the requirements of regional testing and deep coal seam monitoring, and the ability to identify internal defects of the surrounding rock around the tunnel is weak.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A direct current method for testing and evaluating the stability of underground tunnel support, comprising:

[0008] Before the tunnel is developed and supported, multiple measuring lines are evenly arranged around the tunnel, and the resistivity information of the original structure of the surrounding rock before support is tested using the arranged measuring lines;

[0009] Determine the abnormal resistivity area of ​​the surrounding rock according to the resistivity information of the original structure of the surrounding rock, drill the abnormal resistivity area of ​​the surrounding rock, identify its geological information, and determine whether the corresponding abnormal resistivity area of ​​the surrounding rock is a fracture development area and a water-bearing area; wherein the abnormal resistivity area of ​​the surrounding rock refers to the area where the resistivity value on the resistivity contour map of the original structure of the surrounding rock is higher or lower than the preset threshold value at the same depth;

[0010] With the resistivity information of the original structure of the surrounding rock as the background, after the tunnel is supported, the resistivity information of the surrounding rock is tested regularly according to the preset cycle, and the resistivity gradient and resistivity change rate of the surrounding rock are calculated;

[0011] Based on the resistivity test and drilling results, the stability of the tunnel structure was evaluated.

[0012] Furthermore, the number of the measuring lines is 8; the 8 measuring lines are evenly distributed on the roof, floor and two sides of the tunnel, each measuring line contains 64 electrodes, the electrode spacing is 1m, and the single measurement depth is greater than 20m.

[0013] Furthermore, the geological information includes fractures and water content.

[0014] Furthermore, the preset threshold is 20%.

[0015] Furthermore, the drilling of the area with abnormal resistivity of the surrounding rock to determine and identify its geological information to determine whether the corresponding area with abnormal resistivity of the surrounding rock is a fracture development area and a water-bearing area includes:

[0016] The coal rock porosity and water content are tested by drilling and coring in the area with abnormal surrounding rock resistivity. Based on the measured porosity and water content, it is determined whether the corresponding area with abnormal surrounding rock resistivity is a fracture development area and a water-containing area.

[0017] Furthermore, with the resistivity information of the original structure of the surrounding rock as the background, after the tunnel is supported, the surrounding rock resistivity information is tested regularly according to the preset cycle and the surrounding rock resistivity gradient and resistivity change rate are calculated, including:

[0018] After the tunnel is supported, the surrounding rock resistivity information is tested every three days, and the resistivity data is processed to calculate the surrounding rock resistivity gradient and resistivity change rate, and obtain the resistivity change of each test relative to the previous test;

[0019] Based on the calculated resistivity gradient and resistivity change rate of the surrounding rock, the monitoring frequency is increased to once every two days in areas where the gradient exceeds the preset gradient threshold and the change rate exceeds the preset change rate threshold.

[0020] Furthermore, based on the resistivity test and drilling results, the stability of the tunnel structure was evaluated, including:

[0021] If there is no area where the surrounding rock resistivity change rate exceeds 20% in the results of two adjacent tests, it indicates that the tunnel support is stable; otherwise, it indicates that the tunnel support is unstable.

[0022] If the abnormal low resistivity area expands near the water-bearing area, it indicates that the current area is unstable and needs to be drained and supported more effectively;

[0023] If the abnormal high resistivity area expands near the fracture development area, it indicates that the current area is unstable and the grouting and support strength needs to be strengthened;

[0024] If the resistivity increases in the non-abnormal area, it indicates that the surrounding rock has undergone significant deformation and damage, and support needs to be strengthened.

[0025] Furthermore, based on the resistivity test and drilling results, the stability of the tunnel structure is evaluated, including:

[0026] Based on the resistivity information of the original structure of the surrounding rock, the stability and support effect of the initial support tunnel are determined.

[0027] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0028] The technical solution of the present invention obtains the resistivity information of the surrounding rock before and after the tunnel support by direct current method, can identify the hidden geological defects around the tunnel, and identify the changes in the tunnel surrounding rock structure, and has a good ability to identify the development of possible disasters, thereby improving the reliability and accuracy of the tunnel support stability test and evaluation. The method provided by the present invention is applicable to coal tunnels, rock tunnels, etc., and can not only evaluate the stability of the tunnel, but also provide targeted solutions when the tunnel stability is poor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a schematic diagram of the execution flow of the direct current method for testing and evaluating the stability of underground tunnel support provided by the first embodiment of the present invention;

[0031] Figure 2 It is a schematic diagram of the execution flow of the direct current method for testing and evaluating the stability of underground tunnel support provided by the second embodiment of the present invention;

[0032] Figure 3 It is a schematic diagram of the electrical testing and drilling area for tunnel support stability.

[0033] Description of reference numerals:

[0034] 1. Tunnel; 2. Coal safety DC electrical instrument; 3. Electrode; 4. Tunnel surrounding rock; 5. Area to be tested; 6. Explosion-proof cable; 7. Detection borehole; 8. Water-containing low-resistance area; 9. Crack-containing high-resistance area. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] First embodiment

[0037] This embodiment provides a DC electrical method for testing and evaluating the stability of underground tunnel support, which is suitable for testing the internal geological defects and structural changes of the surrounding rock around the tunnel after tunnel development and evaluating the stability of tunnel support. Figure 1 As shown, the following steps are included:

[0038] S1, before the tunnel is developed and supported, multiple measuring lines are evenly arranged around the tunnel, and the resistivity information of the original structure of the surrounding rock before support is tested using the arranged measuring lines;

[0039] Among them, in this embodiment, when multiple measuring lines are evenly arranged around the tunnel, the number of measuring lines is 8; the 8 measuring lines are evenly distributed on the top plate, bottom plate and two sides of the tunnel, each measuring line contains 64 electrodes, the electrode spacing is 1m, and the single measurement depth is greater than 20m.

[0040] S2, determining the abnormal resistivity area of ​​the surrounding rock according to the resistivity information of the original structure of the surrounding rock, drilling the abnormal resistivity area of ​​the surrounding rock, determining and identifying its geological information, so as to determine whether the corresponding abnormal resistivity area of ​​the surrounding rock is a fracture development area and a water-bearing area; wherein the abnormal resistivity area of ​​the surrounding rock refers to the area where the resistivity value on the resistivity contour map of the original structure of the surrounding rock is higher or lower than the preset threshold value at the same depth;

[0041] In this embodiment, the identified geological information includes cracks and water content, etc. When the resistivity value on the resistivity contour map is higher or lower than 20% at the same depth, the area is confirmed as an abnormal area.

[0042] The specific method of drilling the area with abnormal resistivity of surrounding rock to identify its geological information and determine whether the corresponding area with abnormal resistivity of surrounding rock is a fracture development area and a water-bearing area is as follows:

[0043] The coal rock porosity and water content are tested by drilling and coring in the area with abnormal surrounding rock resistivity. Based on the measured porosity and water content, it is determined whether the corresponding area with abnormal surrounding rock resistivity is a fracture development area and a water-containing area.

[0044] S3, taking the resistivity information of the original structure of the surrounding rock as the background, after the tunnel is supported, the resistivity information of the surrounding rock is tested regularly according to the preset cycle, and the resistivity gradient and resistivity change rate of the surrounding rock are calculated;

[0045] In this embodiment, the specific implementation process of the above S3 is as follows:

[0046] After the tunnel is supported, the surrounding rock resistivity information is tested every three days, and the resistivity data is processed to calculate the surrounding rock resistivity gradient and resistivity change rate, and obtain the resistivity change of each test relative to the previous test;

[0047] Based on the calculated resistivity gradient and resistivity change rate of the surrounding rock, the monitoring frequency is increased to once every two days in areas where the gradient exceeds the preset gradient threshold and the change rate exceeds the preset change rate threshold.

[0048] S4, based on the resistivity test and drilling results, the stability of the tunnel structure is evaluated.

[0049] Among them, in this embodiment, the specific evaluation method for evaluating the stability of the tunnel structure is as follows:

[0050] According to the resistivity information of the original structure of the surrounding rock, the stability and support effect of the initial support tunnel are determined;

[0051] If there is no area where the surrounding rock resistivity change rate exceeds 20% in the results of two adjacent tests, it indicates that the tunnel support is stable; otherwise, it indicates that the tunnel support is unstable.

[0052] If the abnormal low resistivity area expands near the water-bearing area, it indicates that the current area is unstable and needs to be drained and supported more effectively;

[0053] If the abnormal high resistivity area expands near the fracture development area, it indicates that the current area is unstable and the grouting and support strength needs to be strengthened;

[0054] If the resistivity increases in the non-abnormal area, it indicates that the surrounding rock has undergone significant deformation and damage, and support needs to be strengthened.

[0055] In summary, the method of this embodiment judges the stability of tunnel support by comparing the change in resistivity caused by surrounding rock deformation before and after underground tunnel support, thereby reducing the evaluation cost and time, and solving the problems of the current visual observation method's weak ability to identify internal defects of surrounding rocks around tunnels and low accuracy. It also helps to identify the evolution process of tunnel disasters, propose targeted treatment methods, and effectively prevent disasters from occurring.

[0056] Second embodiment

[0057] See also Figure 2 and Figure 3This embodiment provides a DC electrical testing and evaluation method for underground tunnel stability, which is suitable for testing geological defects and structural changes in the surrounding rock around the tunnel after tunnel development and evaluating the stability of tunnel support. The method includes arranging electrodes in the tunnel, and regularly testing the resistivity distribution and change characteristics of the tunnel surrounding rock before and after the implementation of tunnel support, thereby determining and identifying its cracks, water content and internal deformation and damage process, and then evaluating the stability of tunnel support. Specifically, the execution process of this method is as follows Figure 2 As shown, the electrical method layout area and drilling method are as follows Figure 3 As shown, the following steps are included:

[0058] S201, after the development of the tunnel 1 but before the support, a coal safety type DC electrical method instrument 2 is arranged in the tunnel 1, and 64 electrodes 3 are inserted into the tunnel wall of the test area 5 of the tunnel surrounding rock 4 along the direction of the tunnel 1 with a pole spacing of 1m. The coal safety type DC electrical method instrument 2 and the electrodes 3 are connected together through an explosion-proof cable 6. A total of 8 tests are conducted in the tunnel 1, and each time the electrodes are located at the roof, floor and two sides of the tunnel 1;

[0059] S202, using a coal safety type direct current electrical method instrument 2 to perform resistivity testing on a test area 5 of a tunnel surrounding rock 4, and obtaining a resistivity contour map of the test area 5;

[0060] S203, the area where the resistivity value on the resistivity contour map is higher or lower than the same depth by more than 20% is regarded as a resistivity abnormal area, and a detection borehole 7 is arranged in the abnormal area;

[0061] S204, obtaining the core of the resistivity abnormal area through the detection borehole 7, and testing the porosity and water content of the coal rock to determine whether these areas are water-containing low-resistance areas 8 and fracture-containing high-resistance areas 9;

[0062] S205, testing the resistivity information of the tunnel surrounding rock 4 every three days, and processing the resistivity data to obtain the resistivity change of each test relative to the previous test;

[0063] S206: Increase the monitoring frequency to once every two days for areas with resistivity gradient greater than 1.2Ω and resistivity change rate greater than 20%;

[0064] S207, based on the resistivity test and drilling results, the stability of tunnel 1 is evaluated, wherein the evaluation method is as follows: if there is no area where the resistivity change rate of the surrounding rock exceeds 20% in the results of two adjacent tests, it indicates that the support of tunnel 1 is stable, otherwise, it indicates that the support of tunnel 1 is unstable; if the low-value resistivity abnormal area near the water-containing low-resistance area 8 expands, it indicates that the area is unstable and the drainage and support strength need to be strengthened; if the high-value resistivity abnormal area near the fracture-containing high-resistance area 9 expands, it indicates that the area is unstable and the grouting and support strength need to be strengthened; if the resistivity increases in the non-abnormal area, it indicates that the surrounding rock has undergone significant deformation and damage and the support needs to be strengthened;

[0065] S208: Improve the support method and enhance the support capacity based on the evaluation results.

[0066] Through the above test and evaluation process, the DC electrical method test of roadway support stability was realized, the stability evaluation method and corresponding solutions were proposed, and the monitoring ability and evaluation accuracy of roadway defects were improved. It is suitable for coal roadways, rock roadways, etc. It can not only evaluate the stability of roadways, but also provide targeted solutions when the stability of roadways is poor.

[0067] In addition, it should be noted that, in this article, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0068] Finally, it should be noted that the above is a preferred embodiment of the present invention. It should be pointed out that although the preferred embodiment of the present invention has been described, for those skilled in the art, once the basic creative concept of the present invention is known, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention. Therefore, the attached claims are intended to be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the embodiments of the present invention.

Claims

1. A direct current method for testing and evaluating the stability of underground tunnel support, characterized in that: include: Before the tunnel is developed and supported, multiple measuring lines are evenly arranged around the tunnel, and the resistivity information of the original structure of the surrounding rock before support is tested using the arranged measuring lines; Determine the abnormal resistivity area of ​​the surrounding rock according to the resistivity information of the original structure of the surrounding rock, drill the abnormal resistivity area of ​​the surrounding rock, identify its geological information, and determine whether the corresponding abnormal resistivity area of ​​the surrounding rock is a fracture development area and a water-bearing area; wherein the abnormal resistivity area of ​​the surrounding rock refers to the area where the resistivity value on the resistivity contour map of the original structure of the surrounding rock is higher or lower than the preset threshold value at the same depth; With the resistivity information of the original structure of the surrounding rock as the background, after the tunnel is supported, the resistivity information of the surrounding rock is tested regularly according to the preset cycle, and the resistivity gradient and resistivity change rate of the surrounding rock are calculated; Based on the resistivity test and drilling results, the stability of the tunnel structure is evaluated, including: if there is no area where the resistivity change rate of the surrounding rock exceeds 20% in the results of two adjacent tests, it indicates that the tunnel support is stable, otherwise, it indicates that the tunnel support is unstable; if the low-value resistivity abnormal area expands near the water-bearing area, it indicates that the current area is unstable and the drainage and support strength need to be strengthened; if the high-value resistivity abnormal area expands near the fracture development area, it indicates that the current area is unstable and the grouting and support strength need to be strengthened; if the resistivity increases in the non-abnormal area, it indicates that the surrounding rock has undergone significant deformation and damage and the support needs to be strengthened.

2. The DC electrical method for testing and evaluating the stability of underground tunnel support as claimed in claim 1, characterized in that: The number of the measuring lines is 8; the 8 measuring lines are evenly distributed on the roof, floor and two sides of the tunnel, each measuring line contains 64 electrodes, the electrode spacing is 1m, and the single measurement depth is greater than 20m.

3. The DC electrical method for testing and evaluating the stability of underground tunnel support as claimed in claim 1, characterized in that: The geological information includes fractures and water content.

4. The DC electrical testing and evaluation method for underground tunnel support stability according to claim 1, characterized in that: The preset threshold is 20%.

5. The DC electrical method for testing and evaluating the stability of underground tunnel support as claimed in claim 1, characterized in that: The drilling of the area with abnormal resistivity of the surrounding rock to determine and identify its geological information to determine whether the corresponding area with abnormal resistivity of the surrounding rock is a fracture development area and a water-bearing area includes: The coal rock porosity and water content are tested by drilling and coring in the area with abnormal surrounding rock resistivity. Based on the measured porosity and water content, it is determined whether the corresponding area with abnormal surrounding rock resistivity is a fracture development area and a water-containing area.

6. The DC electrical method for testing and evaluating the stability of underground tunnel support according to claim 1, characterized in that: With the resistivity information of the original structure of the surrounding rock as the background, after the tunnel is supported, the surrounding rock resistivity information is tested regularly according to the preset cycle, and the surrounding rock resistivity gradient and resistivity change rate are calculated, including: After the tunnel is supported, the surrounding rock resistivity information is tested every three days, and the resistivity data is processed to calculate the surrounding rock resistivity gradient and resistivity change rate, and obtain the resistivity change of each test relative to the previous test; Based on the calculated resistivity gradient and resistivity change rate of the surrounding rock, the monitoring frequency is increased to once every two days in areas where the gradient exceeds the preset gradient threshold and the change rate exceeds the preset change rate threshold.

7. The DC electrical method for testing and evaluating the stability of underground tunnel support as claimed in claim 1, characterized in that: Based on the resistivity test and drilling results, the stability of the tunnel structure is evaluated, including: Based on the resistivity information of the original structure of the surrounding rock, the stability and support effect of the initial support tunnel are determined.

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