A method for testing rock damage and crack distribution around impact drilling holes

Abstract

The present invention relates to the technical field of rock damage detection methods, and in particular to a method for testing rock damage and crack distribution around impact drilling rock breaking holes, comprising: impact drilling on the rock surface to obtain a central borehole to form cracks; selecting a sampling area on the rock surface; dyeing the sampling area to display cracks; obtaining the length of the damage range of the rock surface around the hole; determining the length of the coring range around the hole according to the length of the damage range of the rock surface around the hole; obtaining a core sample around the hole within the length of the coring range around the hole; obtaining a control core sample in an area far from the central borehole; analyzing the characteristics of the core sample around the hole and the control core sample, and dividing the damage area according to the degree of damage. The present invention improves the accuracy of rock damage range detection by analyzing the damage characteristics of the rock around the impact drilling hole and comparing the parameters with the rock in the unaffected area, and has guiding significance for the parameter design of deep drilling reaming drill tools and large-diameter pile foundation construction reaming rock breaking drill tools.

Description

Technical Field

[0001] The invention relates to the technical field of rock damage detection methods, and in particular to a method for testing rock damage and crack distribution around a percussion drilling rock breaking hole. Background Art

[0002] When percussion drilling is used in hard rock formations, the rock around the hole will be damaged to a certain extent due to the unloading of the rock borehole and the impact stress wave, which is mainly manifested as the development of cracks inside the rock. The damage to the rock around the hole is beneficial for reaming drilling in deep drilling and large-diameter reaming drilling around shallow holes. The damage to the rock around the hole caused by percussion drilling reduces the strength of the rock to a certain extent, which is beneficial to the reaming drilling of the reamer or reaming wing.

[0003] Rock damage detection methods in the prior art rarely involve this field, and the research and detection of the damage degree and strength weakening distribution law of the rock around the hole are mostly carried out by using small-sized samples cut separately at a reduced scale, which has many interference factors and poor accuracy. Therefore, studying the damage law of the rock around the hole during impact drilling has guiding significance for the parameter design of deep drilling reaming tools and large-diameter pile foundation construction reaming and rock breaking tools. It is necessary to accurately detect the damage degree and strength weakening distribution law of the rock around the hole. Summary of the invention

[0004] The purpose of the present invention is to provide a method for testing rock damage and crack distribution around impact drilling rock breaking holes, which can carry out in-situ detection of rock damage during impact drilling to improve the accuracy of detecting the damage degree and strength weakening distribution law of the rock around the hole.

[0005] In order to solve the above technical problems, the present invention provides a method for testing rock damage and crack distribution around a percussion drilling rock breaking hole.

[0006] The method for testing rock damage and crack distribution around a percussion drilling rock-breaking hole of the present invention comprises:

[0007] Impact drilling is performed on the rock surface to obtain a center hole to form a crack;

[0008] selecting a sampling area on the rock surface;

[0009] staining the sampled area to reveal the cracks;

[0010] Obtain the length of the damage range on the rock surface around the hole;

[0011] Determine the length of the coring range around the hole according to the length of the rock surface damage range around the hole;

[0012] Obtaining a core sample around the hole within the length of the coring range around the hole;

[0013] Obtain control core samples in areas away from the central borehole;

[0014] The characteristics of the core samples around the holes and the control core samples were analyzed, and the damaged areas were divided according to the degree of damage.

[0015] Further, the selecting a sampling area on the rock surface includes:

[0016] On the rock surface along the circumference of the central borehole, a plurality of areas of a set width arranged at intervals along the circumference of the central borehole are selected as the sampling areas.

[0017] Furthermore, obtaining a core sample around the hole within the length of the coring range around the hole includes:

[0018] In the sampling area, a circumferential core sample is drilled at a set distance along the radial direction of the central borehole, the set width is not less than the diameter of the circumferential core sample, and the diameter of the circumferential core sample is equal to the diameter of the control core sample.

[0019] Furthermore, the step of dyeing the sampling area to display the cracks comprises:

[0020] Evenly spray the penetrant on the sampling area;

[0021] After the penetrant has dried, the sampling area is sprayed with a developer.

[0022] Furthermore, the obtaining of the length of the rock surface damage range around the hole includes:

[0023] The maximum distance between the crack in the sampling area and the peripheral edge of the central borehole is obtained, and the maximum distance is the length of the damage range of the rock surface around the hole.

[0024] Furthermore, the length of the coring range around the hole is a set multiple of the length of the rock surface damage range around the hole, and the value range of the set multiple is 1.3-1.8.

[0025] Furthermore, before obtaining the hole circumference core sample, the central borehole is filled with a supporting medium.

[0026] Furthermore, the drilling direction of the core sample around the hole is parallel to the axial direction of the central drill hole.

[0027] Furthermore, the analyzing the characteristics of the core sample around the hole and the control core sample and dividing the damaged area according to the degree of damage includes:

[0028] At least three indicators are used to perform characteristic analysis on the hole-surrounding core sample and the control core sample to obtain multiple hole-surrounding rock damage range lengths, and the average of the two smaller values ​​is selected as the actual hole-surrounding rock damage range length.

[0029] Furthermore, three indices are used to perform characteristic analysis on the hole core sample and the control core sample, namely, crack distribution index, rock wave velocity index and rock sample mechanical property index.

[0030] Furthermore, starting from the peripheral edge of the central borehole, the damaged areas are divided into a high damage area, a medium damage area and a low damage area in sequence;

[0031] The high damage zone is the actual damage range length of the rock around the hole within the first set ratio range, the moderate damage zone is the actual damage range length of the rock around the hole within the second set ratio range, and the low damage zone is the actual damage range length of the rock around the hole within the third set ratio range.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] By using colored penetrant testing on the rock surface around the hole, the damage range around the impact rock breaking hole can be quickly determined, which is convenient for determining the radial sampling length around the hole, saving time and cost for subsequent rock damage detection.

[0034] By analyzing the damage characteristics of the rock around the impact drilling hole and comparing the parameters with the rocks in the unaffected area, the accuracy of rock damage range detection is improved. This has guiding significance for the parameter design of deep drilling reaming drill tools and large-diameter pile foundation construction reaming and rock breaking drill tools, and can more accurately obtain the damage degree and strength weakening distribution law of the rock around the hole.

[0035] Furthermore, for the rock core samples taken, multiple indicators such as crack distribution, rock wave velocity and mechanical properties of rock samples are used to jointly analyze the rock damage characteristics around the impact drilling hole. Non-destructive crack observation and wave velocity measurement are carried out first, and then the mechanical properties test of the rock samples is carried out. This allows the detection to be completed in one sampling and sample preparation, reducing the detection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of an embodiment of a method for testing rock damage and crack distribution around a percussion drilling rock breaking hole of the present invention;

[0037] Figure 2 It is a schematic diagram of the distribution of the colored penetration detection area on the surface of the rock around the hole in the method for testing the rock damage and crack distribution around the impact drilling rock breaking hole of the present invention;

[0038] Figure 3 Schematic diagram of radial core sampling of rock around a hole in the method for testing rock damage and crack distribution around a rock breaking hole by impact drilling of the present invention;

[0039] Figure 4It is a schematic diagram of the preparation of the core sample around the hole of the impact drilling rock breaking hole and crack distribution test method of the present invention;

[0040] Figure 5 It is a schematic diagram of the preparation of a control core sample for the test method of rock damage and crack distribution around the impact drilling rock breaking hole of the present invention;

[0041] Figure 6 The present invention is a schematic diagram of calculating the fractal dimension of cracks by using the box counting dimension method in the rock damage and crack distribution testing method around the impact drilling rock breaking hole of the present invention.

[0042] 1. Center drill hole; 2. Rock surface; 3. Sampling area; 4. Core sample around the hole; 41. Disc core sample around the hole; 42. Cylindrical core sample around the hole; 5. Control core sample; 51. Control disc core sample; 52. Control cylindrical core sample; 6. Counting box; 7. Non-counting box. DETAILED DESCRIPTION

[0043] The following will describe the rock damage and crack distribution test method around the impact drilling rock breaking hole of the present invention in conjunction with the schematic diagram, wherein the preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art can modify the present invention described herein and still achieve the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation of the present invention.

[0044] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings). In the description of the present invention, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0045] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0046] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to facilitate and clearly assist in illustrating the purpose of the embodiments of the present invention.

[0047] The following is attached to the instruction manual Figure 1 To Attachment Figure 6 , the rock damage and crack distribution testing method around the impact drilling rock breaking hole of the present invention is introduced.

[0048] In one embodiment, if Figure 1 As shown, the rock damage and crack distribution test method around the impact drilling rock breaking hole includes:

[0049] S100: impact drilling on the rock surface to get a center hole to form a crack;

[0050] S200: selecting a sampling area on the rock surface;

[0051] S300: dyeing the sampling area to display the crack;

[0052] S400: Obtain the length of the damage range of the rock surface around the hole;

[0053] S500: determining the length of the coring range around the hole according to the length of the rock surface damage range around the hole;

[0054] S600: Acquire a core sample around the hole within the length of the coring range around the hole;

[0055] S700: Obtain a control core sample in an area away from the central borehole;

[0056] S800: Analyze the characteristics of the core sample around the hole and the control core sample, and divide the damaged area according to the degree of damage.

[0057] In step S100, a down-the-hole hammer impact drilling can be used to obtain a central borehole 1, such as a pneumatic or hydraulic down-the-hole hammer, or an electric down-the-hole hammer. It is preferred to drill on a flat rock surface 2 that is completely exposed on site. In this embodiment, the rock is granite. In other embodiments, the method can also be used to test other types of rocks. The drilling depth is not less than 0.5 meters, and the diameter of the borehole generally needs to be greater than the diameter of the hole core sample 4 in the subsequent steps. For example, the diameter of the drilled central borehole 1 is 450 mm, and the drilling depth is 500 mm.

[0058] In step S200, in one embodiment, a cleaning agent is first used to clean the rock surface 2 to remove pollutants on the rock surface 2. After the rock surface 2 is dried, multiple areas of a set width arranged circumferentially and spaced along the central borehole 1 are selected on the rock surface 2 as the sampling areas 3. The set width is not less than the diameter of the core sample 4 around the hole.

[0059] For example, Figure 2 As shown, in this embodiment, four symmetrical areas with a width of 60 mm are selected as the sampling areas 3, namely T1, T2, T3 and T4. Among them, the diameter of the core sample 4 around the hole is 50 mm, and the set width of the sampling area 3 is 60 mm. In other embodiments, three or five areas can also be selected as the sampling areas 3.

[0060] In step S300, in one of the embodiments, in order to show the scope of the cracks, the penetrant is evenly sprayed on the four sampling areas 3. The retention time of the penetrant is related to the permeability of the rock. For rocks with extremely poor permeability, the required penetration time is not less than 2 hours. After the penetrant is dry, the developer is continued to be sprayed on the penetrant sprayed area to fully color the cracks on the surface 2 of the rock being tested.

[0061] In step S400, in order to obtain the damage range length of the rock surface 2 around the hole, the maximum distance between the crack in each stained sampling area 3 and the edge of the hole around the central borehole 1 is measured, thereby obtaining multiple measurement values, and the maximum value of the multiple measurement values ​​is selected as the damage range length of the rock surface 2 around the hole, which is recorded as L T1 .

[0062] In step S500, the length of the coring range around the hole is determined according to the length of the damage range of the rock surface 2 around the hole. Specifically, the length of the coring range around the hole is a set multiple of the length of the damage range of the rock surface 2 around the hole, and the value range of the set multiple is 1.3-1.8. Preferably, in this embodiment, the length of the coring range around the hole is 1.5 times the length of the damage range of the rock surface 2 around the hole. In other embodiments, it can also be 1.4 times or 1.6 times according to different types of rocks.

[0063] When coring, a core drill can be used for drilling, and the actual drilling sampling length is not less than 250 mm, and the core is taken out after being cut by the coring drill bit. The two ends of the obtained hole core sample 4 are uneven surfaces. In order to facilitate subsequent testing, the two end surfaces need to be polished flat. In this embodiment, the drilling sampling length is 250 mm.

[0064] In step S600, in one embodiment, as Figure 3 As shown, in order to ensure the integrity of the drilled hole core sample 4, when sampling, a hole core sample 4 is drilled at a set distance along the radial direction of the central drill hole 1 in each area of ​​the set width, and the set distance is not less than 10 mm. In the present embodiment, a hole core sample 4 is drilled every 10 mm.

[0065] The set width is not less than the diameter of the hole core sample 4, and the diameter of the hole core sample 4 is equal to the diameter of the control core sample 5. For example, the diameter of the hole core sample 4 is 50 mm, the set width of the sampling area 3 is 60 mm, and the diameter of the control core sample 5 is equal to the diameter of the hole core sample 4, which is also 50 mm.

[0066] In one embodiment, as an in-situ test method, the drilling direction of the core sample around the hole is parallel to the axial direction of the central borehole. The in-situ test method refers to a test conducted directly in the on-site foundation soil layer. Since the on-site ground is generally flat, it is more convenient to sample by making the drilling direction of the core sample around the hole parallel to the axial direction of the central borehole.

[0067] In another embodiment, the drilling direction of the circumferential core sample can be made perpendicular to the axial direction of the central borehole. Specifically, a circumferential core sample can be drilled in each area in a direction perpendicular to the axial direction of the central borehole. In this case, the length of the circumferential core sample is the length of the circumferential coring range. Of course, this requires the topography of the on-site foundation, and there needs to be an operating space on the side of the central borehole for drilling the circumferential core sample, such as a pit on the side of the central borehole.

[0068] In one of the embodiments, preferably, in order to avoid the core sampling failure caused by the thin hole wall, low strength and poor support near the edge of the center borehole 1, the center borehole 1 needs to be filled with a supporting medium of a certain strength before coring to enhance the supporting property of the hole wall of the center borehole 1.

[0069] Specifically, the supporting medium may be concrete or other supporting medium. After the concrete is filled, it is necessary to wait for 7 days and then drill from the center borehole 1 along the borehole radial direction at equal intervals of 10 mm.

[0070] In one of the embodiments, in step S700 , in order to prevent the characteristics of the rock itself from interfering with the test results, a control core sample 5 is obtained in an area away from the central borehole 1 .

[0071] For example, sampling is performed at a position 12100 mm away from the central borehole, and the distance between the sampling position and the central borehole 1 is five times the length of the damage range of the rock surface 2 around the hole. The core is cut off by a coring drill bit and then taken out, and both end faces of the obtained control core sample 5 are polished and smoothed.

[0072] In this embodiment, the control core sample 5 is drilled after the central borehole 1 is drilled. In other embodiments, the control core sample 5 can also be drilled before the central borehole 1 is drilled, that is, the order of obtaining the control core sample 5 and drilling the central borehole 1 is changed.

[0073] In one of the embodiments, in step S800, in order to improve the accuracy of detection, when analyzing the characteristics of the circumference core sample 4 and the control core sample 5, at least three indicators are used to perform characteristic analysis on the circumference core sample 4 and the control core sample 5, and multiple circumference rock damage widths are obtained, and the average of the two smaller values ​​is selected as the actual circumference rock damage width.

[0074] In this embodiment, three indices are used to perform characteristic analysis on the hole core sample 4 and the control core sample 5, namely, crack distribution index, rock wave velocity index and rock sample mechanical property index.

[0075] Before the analysis, the hole core sample 4 and the control core sample 5 are processed to facilitate the subsequent testing process.

[0076] For example, Figure 4 As shown, each hole circumference core sample 4 obtained is continuously and equidistantly cut into three hole circumference disc samples with a height of 25 mm and three hole circumference cylindrical samples with a height of 50 mm. The three hole circumference disc core samples 41 and the three hole circumference cylindrical samples in the same hole are each a group. For the same group of samples, during the test, the average value of the three samples is recorded as the measured rock damage parameter, and the distance from each group of disc core samples to the hole circumference of the central borehole 1 is recorded.

[0077] Correspondingly, if Figure 5 As shown, the control core sample 5 is also cut into three control disc samples with a height of 25 mm and three control cylindrical samples with a height of 50 mm at equal intervals.

[0078] For the hole-circumference disc specimen and the control disc specimen, as well as the hole-circumference cylindrical specimen and the control cylindrical specimen, the upper and lower bottom surfaces of the specimens are used as observation surfaces and are ground and polished, and the parallelism of the upper and lower surfaces is not greater than 0.1 mm.

[0079] In one embodiment, when crack distribution index is used for feature analysis, a cleaning agent is first sprayed on the observation surface of the disc sample (including the hole circumference disc sample and the control disc sample) to remove pollutants on the observation surface; after drying, a penetrant is sprayed to improve the permeability of the rock cracks. The penetrant needs to be evenly sprayed on the observation surface, and the penetration time and drying time are not less than 36 hours; then the sample is immersed in the developer solution at room temperature for more than 30 minutes, and then cleaned and dried at room temperature for more than 30 minutes. An optical camera with image magnification is used to observe and record the impact cracks of the hole circumference disc sample and the control disc sample in turn, and a two-dimensional image of the rock crack is obtained and converted into a binary image.

[0080] For the acquired binary image, such as Figure 6 As shown in the figure, the box counting method is used to calculate the fractal dimension D of the crack around the hole at different radial distances from the hole. f The fractal dimension D of the crack of the control disk specimen f0 . Fractal dimension of hole crack D f The value range is 1~2, and the larger the value, the richer the crack development.

[0081] For the selected calculation area, first select a suitable pixel value of the box side length r, and calculate the number of boxes N(r) covering the target crack in the calculation area, that is, the counting box 6; the box that does not cover the target crack is the non-counting box 7. According to the following formula (1), calculate the fractal dimension D of the crack around the hole f and the control crack fractal dimension D f0 .

[0082] In this embodiment, the crack fractal dimension can be calculated using the Hausdorff dimension (a mathematical tool for describing the complexity of fractal geometric shapes) method and the self-similarity dimension method.

[0083] The crack fractal dimension can be replaced by the crack distribution area percentage, and the crack distribution area percentage of the binary image of the selected area is calculated. When the crack distribution area percentage of the disc sample along the hole circumference is not more than 10% different from the crack distribution area percentage of the control disc sample, the distance from the hole circumference of the hole circumference disc sample to the central borehole 1 is the hole circumference rock damage distance L. T2 In one embodiment, in order to reduce the error, at least two radial regions L are measured. T2 , take the average value.

[0084] The diameter of the hole circumference disk sample in this embodiment is 50 mm, that is, the radial distance interval of the crack fractal dimension is 50 mm. f The radial distance varies from 1.18 to 1.65, and the fractal dimension D of the control crack of the disc specimen is f0 The average value is 1.12, and the fractal dimension of the crack around the hole is D f The minimum value of the crack fractal dimension D f0 The difference is less than 10%. The distance from the hole circumference disc sample to the hole circumference of the central borehole 1 corresponding to the minimum value is 600 mm. The rock damage distance L T2 is 600 mm.

[0085] (1)

[0086] Where N(r) is the number of boxes covering the target crack, r is the side length of the box, and A is a constant. For the acquired binary image, the side length r can be selected to be a suitable value between 1 and 100 pixels.

[0087] In one embodiment, when the rock wave velocity index is used for characteristic analysis, the longitudinal wave velocity V of the cylindrical core sample 42 along the radial direction of the hole is measured by a wave velocity testing instrument. P , and obtain the variation range of the wave velocity of the cylindrical core sample 42 around the hole with the radial distance. At the same time, the longitudinal wave velocity V0 of the control cylindrical core sample 52 is measured by the wave velocity testing instrument. P The difference with V0 value is no more than 10% and V P No longer changes with increasing distance, then V P When the V0 point is reached for the first time, the corresponding distance to the periphery of the central borehole 1 is the rock damage distance L around the impact drilling hole. T3 In one embodiment, in order to reduce the error, at least two radial regions L are measured. T3 , take the average value. T3 It is 420mm.

[0088] During the measurement, the wave velocity test uses a non-metallic ultrasonic tester, and the test sample is placed between the transmitting transducer and the receiving transducer. In order to ensure good contact between the transducer surface and the upper and lower end faces of the rock, a layer of lubricating grease is evenly applied to both ends of the rock sample (i.e., cylindrical core sample). During the test, the tester excites the ultrasonic wave, and it enters the rock core sample from the transmitting transducer. The receiving transducer receives the ultrasonic signal, and the longitudinal wave velocity of the sample is obtained through data analysis. The wave velocity of each rock sample is tested 3 times, and 3 samples are tested, and the average value is taken as the longitudinal wave velocity corresponding to the rock at that distance.

[0089] In one embodiment, when the mechanical property index of the rock sample is used for characteristic analysis, the hole circumference disc core sample 41 and the control disc core sample 51 are used as test objects, and the Brazilian tensile strength of the two is measured; when the tensile strength of the hole circumference disc core sample 41 increases with the radial distance to a difference of no more than 10% from the tensile strength of the control disc core sample 51, the distance from the hole circumference of the hole circumference disc core sample 41 to the central borehole 1 is the impact drilling hole circumference rock damage distance L T4 In one embodiment, in order to reduce the error, at least two radial regions L are measured. T4 , take the average value. T4 is 540 mm.

[0090] In one embodiment, for the three hole-circumferential rock damage widths L obtained by testing, T2 , L T3 , L T4 , taking the average of the two smaller values ​​as the rock damage width around the impact drilling hole, which can better guide the design of hole expansion drilling parameters, then the rock damage width around the impact drilling hole L measured in this embodiment is T It is 480mm, that is, for a 450mm granite impact drilling hole, the actual damaged width of the rock around the hole is 480mm.

[0091] In one embodiment, starting from the peripheral edge of the central borehole 1, the damage areas are divided into a high damage area, a medium damage area and a low damage area in sequence;

[0092] The high damage zone is the actual damage width of the rock around the hole within the first set proportion range, the moderate damage zone is the actual loss width of the rock around the hole within the second set proportion range, and the low damage zone is the actual loss width of the rock around the hole within the third set proportion range.

[0093] Among them, the highly damaged area indicates that the cracks inside the rock are fully developed, and the mechanical properties of the rock are greatly reduced, with a decrease of more than 50%; the moderately damaged area indicates that the cracks inside the rock are significantly developed, the mechanical properties of the rock are significantly lower, and the drillability of the rock is significantly improved; the cracks inside the rock in the low-damage area are relatively developed, and the rock strength is reduced, which is conducive to rock crushing.

[0094] In this embodiment, 0<the first set ratio range≤20%; 20%<the second set ratio range<60%, 60%≤the second set ratio range≤100%. In other embodiments, different set ratio ranges may be used according to different rock types or other different factors.

[0095] In this embodiment, the rock damage width L around the impact drilling hole is T The diameter of the hole is 480mm, and the damage width areas along the radial direction can be divided into high damage area, medium damage area and low damage area according to the damage width areas of 0~96mm, 96~288mm and 288~480mm respectively.

[0096] Through the above detection method, the present invention can bring the following beneficial effects:

[0097] (1) The use of color penetrant testing on the rock surface around the hole can quickly determine the damage range around the impact rock breaking hole, facilitate the determination of the radial sampling length around the hole, and save time and cost for subsequent rock damage detection.

[0098] (2) For the rock core samples taken, non-destructive crack observation and wave velocity measurement are first carried out, and then the mechanical properties test of the rock samples is carried out. This allows the testing to be completed in one sampling and sample preparation, reducing the testing cost.

[0099] (3) The damage characteristics of the rock around the impact drilling hole are analyzed by using multiple indicators such as crack distribution, rock wave velocity and mechanical properties of rock samples, and the parameters are compared with those of the rocks in the unaffected area. This improves the accuracy of rock damage range detection and has guiding significance for the parameter design of deep drilling reaming tools and large-diameter pile foundation construction reaming and rock breaking tools. It can more accurately obtain the damage degree and strength weakening distribution law of the rock around the hole.

[0100] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for testing rock damage and crack distribution around a percussion drilling hole, characterized in that: include: Impact drilling is performed on the rock surface to obtain a center hole to form a crack; Select sampling areas on the rock surface including: On the rock surface along the circumference of the central borehole, a plurality of areas of a set width arranged at intervals along the circumference of the central borehole are selected as the sampling areas; staining the sampled area to reveal the cracks; Obtain the length of the rock surface damage range around the hole, including: Obtaining the maximum distance between the crack in the sampling area and the edge of the central borehole, the maximum distance being the length of the rock surface damage range around the hole; Determine the coring range length around the hole according to the rock surface damage range length around the hole, wherein the coring range length around the hole is a set multiple of the rock surface damage range length around the hole, and the value range of the set multiple is 1.3-1.8; Obtaining a core sample around the hole within the length of the hole coring range includes: Drilling a core sample around the hole at a set distance in the radial direction of the central borehole in the sampling area, wherein the set width is not less than the diameter of the core sample around the hole; Obtaining a control core sample in an area away from the central borehole, wherein the diameter of the core sample around the borehole is equal to the diameter of the control core sample; Analyze the characteristics of the hole core sample and the control core sample, divide the damage area according to the degree of damage, use crack distribution index, rock wave velocity index and rock sample mechanical property index to perform characteristic analysis on the hole core sample and the control core sample, obtain multiple hole rock damage range lengths, and select the average of the two smaller values ​​as the actual hole rock damage range length; Each hole circumference core sample obtained is continuously and equidistantly cut into three hole circumference disc samples and three hole circumference cylindrical samples. The three hole circumference disc samples and three hole circumference cylindrical samples in the same hole are each a group. For the same group of samples, when testing, the average value of the three samples is recorded as the measured rock damage parameter, and the distance from each group of samples to the hole circumference of the central drill hole is recorded; the control core sample is also continuously and equidistantly cut into three control disc samples and three control cylindrical samples; When crack distribution index is used for feature analysis, an optical camera with image magnification is used to observe and record the impact cracks of the hole circumference disc sample and the control disc sample in turn, and a two-dimensional image of the rock crack is obtained and converted into a binary image; when the crack distribution area percentage of the hole circumference disc sample differs from that of the control disc sample by no more than 10%, the distance from the hole circumference of the hole circumference disc sample to the central drill hole is the hole circumference rock damage range length L T2 ; When the rock wave velocity index is used for characteristic analysis, the wave velocity test instrument is used to measure the longitudinal wave velocity V of the cylindrical sample around the hole along the radial direction of the hole. P , obtain the range of variation of wave velocity of cylindrical specimen around hole with radial distance, and at the same time, use wave velocity test instrument to measure longitudinal wave velocity V0 of control cylindrical specimen respectively. P The difference with V0 value is no more than 10% and V P No longer changes with increasing distance, then V P When the V0 point is reached for the first time, the corresponding distance to the periphery of the central borehole is the length of the rock damage range around the impact drilling hole, L. T3 ; When the mechanical properties of rock samples are used for characteristic analysis, the hole circumference disc sample and the control disc sample are used as test objects to measure the Brazilian tensile strength of the two. When the tensile strength of the hole circumference disc sample increases with the radial distance to a point where the difference with the tensile strength of the control disc sample is no more than 10%, the distance from the hole circumference of the hole circumference disc sample to the central drill hole is the length L of the rock damage range around the hole during impact drilling. T4 .

2. The method for testing rock damage and crack distribution around impact drilling holes according to claim 1, characterized in that: The step of dyeing the sampling area to show the cracks comprises: Evenly spray the penetrant on the sampling area; After the penetrant has dried, the sampling area is sprayed with a developer.

3. The method for testing rock damage and crack distribution around impact drilling holes according to claim 1, characterized in that: Prior to obtaining the peripheral core sample, the central borehole is filled with a supporting medium.

4. The method for testing rock damage and crack distribution around impact drilling holes according to claim 1, characterized in that: Starting from the peripheral edge of the central borehole, the damaged areas are divided into a high damage area, a medium damage area and a low damage area in sequence; The high damage zone is the actual damage range length of the rock around the hole within the first set ratio range, the moderate damage zone is the actual damage range length of the rock around the hole within the second set ratio range, and the low damage zone is the actual damage range length of the rock around the hole within the third set ratio range.

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