Railway tunnel ground stress test in-hole rock core orientation device and test method

Abstract

A railway tunnel crustal stress test in-hole rock core orienting device is used for conveniently, quickly, efficiently and accurately obtaining the original space orientation of a rock core, ASR and other crustal stress tests based on the orienting rock core are carried out through the orienting rock core, and the size and the direction of tunnel original crustal stress are obtained. The rock core orienting device comprises an outer shell with the diameter consistent with that of the outer pipe of the coring pipe, the inner structure of the outer shell sequentially comprises an upper inner shell, a middle base and a lower annular cavity from top to bottom, and the upper end of the outer shell is connected with the drill rod through a threaded structure. An annular water inlet cavity is formed between the outer wall of the upper inner shell and the inner wall of the outer shell, and an electronic compass mounting bin is arranged in the upper inner shell; and two groups of water pressure rotary drilling marking mechanisms are mounted on the middle base in the radial direction at intervals.

Description

Technical Field

[0001] The invention relates to a railway tunnel ground stress test, and in particular to a rock core orientation device in a railway tunnel ground stress test hole and a test method. Background Art

[0002] In recent years, the scale of railway construction in the western region has been increasing year by year, and there are more and more high-altitude, deep and ultra-long railway tunnels. A large number of ultra-deep exploration drilling holes and directional exploration drilling holes have appeared in the survey stage of railway tunnels, and high-stress rock bursts and large deformation problems are prominent in the construction stage. Railway tunnels are linear projects. During the survey stage, it is necessary to obtain the ground stress distribution law of the entire tunnel through limited drilling holes. During the construction stage, due to the disturbance caused by tunnel excavation, it is necessary to obtain the ground stress state of the original rock stress zone, predict high-stress rock bursts and large deformation disasters, and guide tunnel design and construction.

[0003] The hydraulic fracturing method can only obtain the maximum principal stress on the borehole cross section, and has theoretical defects when applied to directional drilling. The stress relief method is limited in measurement depth, and the test effect is poor in soft rock sections with large deformation due to rock crushing. Both methods are cumbersome to operate on site, and the equipment is large. When applied in the rugged mountainous areas of the west, drilling is mostly done in high-altitude areas during the survey phase, and it is difficult to move the equipment uphill, which is time-consuming and labor-intensive. The construction phase is mostly in tunnel rock bursts and deformation sections, and there are problems such as cross-construction, dust pollution, and poor lighting conditions, posing a high safety risk.

[0004] In recent years, geostress testing methods such as the ASR method based on directional core drilling have been increasingly adopted on the western plateau railway due to their safety, efficiency, and freedom from depth and testing environment restrictions. This method of geostress testing first requires determining the original spatial orientation of the core before drilling. However, since the core rotates with the core barrel and drill pipe, determining the original spatial orientation of the drilled core is difficult.

[0005] Currently, there are two main approaches to determine the original spatial orientation of the core: 1. paleomagnetic measurement of the core, and 2. comparison of ultrasonic drilling imaging with core scanning images. However, these two methods are time-consuming, costly, and have large errors.

[0006] CN117868721A discloses a directional coring drill for non-destructive pigment core marking. The drill comprises an inner tube structure and an outer tube structure sleeved outside the inner tube structure. The inner and outer tube structures are coaxially arranged. A drill bit structure is axially connected to one end of the outer tube structure. One end of the drill bit structure extends into the inner tube structure and is rotatably connected to the inner tube structure. A drive connector is axially connected to the inner tube structure via an inner tube-tube conversion connector. A gap is provided between the inner and outer tube structures, through which the drive connector communicates with the drill bit structure. A non-destructive pigment marking portion is provided on the inner side of the inner tube structure. This structure creates a non-destructive directional coring drill that simultaneously applies pigment to the core surface for directional marking while drilling. While pigment marking is used to obtain the core's original spatial orientation, this method can result in poor marking due to the presence of water, mud, and other substances in the borehole. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a rock core orienting device in a railway tunnel geostress test hole to overcome the application defects of traditional hydraulic fracturing and stress relief methods in railway tunnels, conveniently, quickly, efficiently and accurately obtain the original spatial orientation of the rock core, and use the oriented rock core to carry out geostress tests such as ASR based on oriented rock core to obtain the magnitude and direction of the in-situ stress in the tunnel.

[0008] The technical solutions adopted by the present invention to solve the technical problems are as follows:

[0009] The invention provides a rock core orientation device for a railway tunnel in-situ stress test hole, characterized in that: the rock core orientation device comprises an outer shell having the same diameter as the outer tube of a core sampling tube; the internal structure of the outer shell comprises, from top to bottom, an upper inner shell, a middle base, and a lower annular cavity; the upper end of the outer shell is connected to a drill rod via a threaded structure; an annular water inlet cavity is formed between the outer wall of the upper inner shell and the inner wall of the outer shell; an electronic compass mounting compartment is provided in the upper inner shell; and two sets of hydraulic rotary drilling marking mechanisms are radially spaced apart and installed on the middle base.

[0010] The hydraulic rotary drilling marking mechanism includes a rotating shaft, a hydraulic rotating wheel and a small drill bit. The rotating shaft vertically passes through the middle base and enters the lower annular cavity. The hydraulic rotating wheel is fixedly arranged at the lower end of the rotating shaft, and the small drill bit is installed at the lower end of the hydraulic rotating wheel through a threaded structure. The rotating shaft has an axial water-filled core hole whose upper end is connected to the annular water inlet cavity, and the lower end of the axial water-filled core hole is connected to the radial water spray pipeline on the hydraulic rotating wheel.

[0011] Another technical problem to be solved by the present invention is to provide a test method using the above-mentioned rock core orientation device in the railway tunnel ground stress test hole, the method comprising the following steps:

[0012] Step S1: Determine whether the drilling hole is a deep hole in the survey and design stage or a hole drilled in the tunnel during the construction and operation stage;

[0013] Step S2: When the borehole is a deep hole in the survey and design stage, the integrity of the core of the most recent drilling pass is observed every Sm. If the core is complete, a core directional device is installed and directional coring is carried out. The depth of one directional coring should be less than 50m perpendicular to the tunnel axis. S = (500*H) / (1500+H), where H is the designed hole depth.

[0014] If the drilling is done inside a tunnel during construction or operation, when the vertical distance from the tunnel sidewall or floor to the drilling depth is greater than twice the tunnel diameter, the integrity of the core from the most recent drilling pass shall be observed. If the core is intact, a core orientation device shall be installed to conduct directional coring.

[0015] When observing the integrity of the core from the most recent drilling pass, if the core is incomplete, continue drilling until a complete core is obtained;

[0016] Step S3: When installing the in-hole core orientation device, remove the original coring tube and install the in-hole core orientation device on the lower thread of the drill pipe, and start the electronic compass;

[0017] Step S4: Use a drilling rig and a drill pipe to deliver the in-hole core orientation device to the bottom of the hole, and apply a pressure greater than 1 MPa with water through the drill pipe to start the in-hole core orientation device to work;

[0018] Step S5: Observe the depth of the drill rod descent, estimate that the core orientation device has marked an identifiable mark on the rock section at the bottom of the hole, then lift the drill rod, remove the core orientation device in the hole, replace it with a coring drill bit, and drill the marked core.

[0019] Step S6: Determine the orientation of the line connecting the two marked points of the marked core in combination with the time and orientation data recorded by the electronic compass, thereby obtaining the original spatial orientation of the core;

[0020] Step S7: Conducting a geostress test based on oriented core drilling to obtain the magnitude and direction of the in-situ stress in the tunnel.

[0021] The beneficial effects of the present invention are mainly reflected in the following aspects:

[0022] 1. The rock core orientation device in the railway tunnel ground stress test hole provided by the present invention is lowered by connecting the drill rod provided by the drilling rig, marking is performed by driving the drill bit by water pressure, and the original spatial orientation of the rock core is recorded by an electronic compass. Compared with the existing rock core orientation method, it has the advantages of convenience, speed, efficiency and accuracy.

[0023] 2. The test method of the core directional device in the railway tunnel ground stress test hole provided by the present invention includes the railway tunnel survey and design stage, construction and operation stage, vertical hole, directional hole and other stages, all drilling types and directional core point selection method. According to the characteristics of linear railway tunnel projects, directional cores are obtained in the entire tunnel and the original rock stress zone near the tunnel body, and ground stress tests based on directional cores are carried out.

[0024] 3. The rock core directional device and test method provided by the present invention for testing geostress in railway tunnels focus on the geostress testing method based on directional rock core in high-altitude, deep-buried and ultra-long railway tunnels, solving the application defects of traditional hydraulic fracturing and stress relief methods in railway tunnels and providing geostress data for railway tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] This specification includes the following six drawings:

[0026] Figure 1 This is a schematic structural diagram of a rock core orientation device in a ground stress test hole in a railway tunnel according to the present invention;

[0027] Figure 2 This is a schematic structural diagram of the outer shell of the rock core orientation device in the in-situ stress test hole of a railway tunnel according to the present invention;

[0028] Figure 3 This is a schematic diagram of the arrangement of radial water spray pipes on the hydraulic rotary wheel of the rock core orientation device in the in-situ stress test hole of a railway tunnel according to the present invention;

[0029] Figure 4 This is a schematic diagram of a core orientation device in a railway tunnel in-situ stress test hole according to the present invention drilling a mark on a core;

[0030] Figure 1-Figure 4 Components and corresponding marks are shown: outer shell 10, upper inner shell 11, middle base 12, lower annular cavity 13, annular water inlet cavity 14, sealing cover 15, electronic compass mounting compartment 16, electronic compass 20, buffer pad 21, rotating shaft 30, hydraulic rotating wheel 31, small drill bit 32, axial water filling core hole 33, radial water spray pipeline 34, elastic device 35, bearing 36, sealing ring 37.

[0031] Figure 5 Schematic diagram of the selection of directional sections for stress core sampling in deep holes during the survey and design stage of the present invention. In the figure, S is the interval distance of directional coring in the deep holes during the survey and design stage, in m; H is the designed hole depth of the deep holes during the survey and design stage, in m; θ2 is the angle between the axial direction of the directional deep hole during the survey and design stage and the axial direction of the tunnel, in degrees; and L is the distance from the last directional coring point to the intersection of the borehole and the tunnel axis, in m.

[0032] Figure 6Schematic diagram of the selection of directional sections for stress measurement core drilling in tunnels during the construction and operation stages of the present invention. In the figure, L1 is the drilling depth of the vertical drilling directional coring points in the construction and operation tunnels, in m; L2 is the drilling depth of the directional drilling directional coring points in the construction and operation tunnels, in m; θ1 is the angle between the axial direction of the directional drilling and the axial direction of the tunnel in the construction and operation tunnels, in degrees; and D is the tunnel diameter, in m. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and examples.

[0034] Reference Figures 1 to 4 The present invention's core orientation device for a railway tunnel in-situ stress test hole includes an outer shell 10 with the same diameter as the outer core tube. The internal structure of the outer shell 10, from top to bottom, consists of an upper inner shell 11, a middle base 12, and a lower annular cavity 13. The upper end of the outer shell 10 is connected to the drill pipe via a threaded structure. An annular water inlet cavity 14 is defined between the outer wall of the upper inner shell 11 and the inner wall of the outer shell 10. An electronic compass mounting compartment 16 is located within the upper inner shell 11. Two sets of hydraulic rotary drilling marking mechanisms are radially spaced apart on the middle base 12.

[0035] Reference Figure 1 The hydraulic rotary drilling marking mechanism includes a rotating shaft 30, a hydraulic rotary wheel 31, and a small drill bit 32. The rotating shaft 30 vertically passes through the central base 12 and enters the lower annular cavity 13. The hydraulic rotary wheel 31 is fixedly mounted at the lower end of the rotating shaft 30, and the small drill bit 32 is mounted on the lower end of the hydraulic rotary wheel 31 via a threaded structure. The rotating shaft 30 has an axial water-filled core hole 33 in the interior, the upper end of which communicates with the annular water inlet cavity 14. The lower end of the axial water-filled core hole 33 communicates with a radial water spray pipe 34 on the hydraulic rotary wheel 31.

[0036] Reference Figure 1 The rotating shaft 30 is mounted on the central base 12 via a bearing 36, ensuring normal rotation under water pressure. An elastic device 35 is installed between the lower portion of the rotating shaft 30 and the central base 12 to ensure stable pressure during core marking. Seals 37 are installed at the contact surface between the upper portion of the rotating shaft 30 and the central base 12, and at the contact surface between the upper portion of the elastic device 35 and the central base 12.

[0037] Reference Figure 3 There are four radial water spray pipes 34, whose water inlets and outlets form a 90° angle, and the four water outlets are evenly spaced in the tangential direction of the outer circumference of the hydraulic rotating wheel 31.

[0038] Reference Figure 1A sealing cover 15 threadedly connected to the upper end of the upper inner shell 11 is provided, an electronic compass 20 is installed in the electronic compass installation chamber 16, and a buffer pad 21 is provided between the electronic compass 20 and the chamber wall.

[0039] The outer shell 10, the upper inner shell 11 and the sealing cover 15 are made of non-magnetic materials. The electronic compass 20 is powered by a battery and is used to record the azimuth, inclination and time data of the downhole core orientation device.

[0040] Reference Figure 4 The upper end of the outer shell 10 is connected to the core tube through a thread. When the drill pipe is filled with water and a pressure of about 1 MPa is applied, the water in the drill pipe is slowly discharged through the annular water inlet cavity 14, the axial water-filled core hole 33, and the radial water spray pipeline 34 in sequence, pushing the hydraulic rotary wheel 31 to rotate and driving the small drill bit 32 to rotate, thereby forming a marking point on the core section.

[0041] Reference Figures 4 to 6 The present invention provides a method for testing a core orientation device in a railway tunnel in-situ stress test hole, comprising the following steps:

[0042] Step S1: Determine whether the drilling hole is a deep hole in the survey and design stage or a hole drilled in the tunnel during the construction and operation stage;

[0043] Step S2: When the borehole is a deep hole in the survey and design stage, the integrity of the core of the most recent drilling pass is observed every Sm. If the core is complete, a core directional device is installed and directional coring is carried out. The depth of one directional coring should be less than 50m perpendicular to the tunnel axis. S = (500*H) / (1500+H), where H is the designed hole depth.

[0044] If the drilling is done inside a tunnel during construction or operation, when the vertical distance from the tunnel sidewall or floor to the drilling depth is greater than twice the tunnel diameter, the integrity of the core from the most recent drilling pass shall be observed. If the core is intact, a core orientation device shall be installed to conduct directional coring.

[0045] When observing the integrity of the core from the most recent drilling pass, if the core is incomplete, continue drilling until a complete core is obtained;

[0046] Step S3: When installing the in-hole core orientation device, remove the original coring tube and install the in-hole core orientation device on the lower thread of the drill pipe, and start the electronic compass 20;

[0047] Step S4: Use a drilling rig and a drill pipe to deliver the in-hole core orientation device to the bottom of the hole, and apply a pressure greater than 1 MPa with water through the drill pipe to start the in-hole core orientation device to work;

[0048] Step S5: Observe the depth of the drill rod descent, estimate that the core orientation device has marked an identifiable mark on the rock section at the bottom of the hole, then lift the drill rod, remove the core orientation device in the hole, replace it with a coring drill bit, and drill the marked core.

[0049] Step S6: Determine the orientation of the line connecting the two marked points of the marked core in combination with the time and orientation data recorded by the electronic compass 20, thereby obtaining the original spatial orientation of the core;

[0050] Step S7: Conducting a geostress test based on oriented core drilling to obtain the magnitude and direction of the in-situ stress in the tunnel.

[0051] The above description is merely a diagram illustrating some principles of the core orientation device and test method for testing stress in a railway tunnel according to the present invention, and is not intended to limit the present invention to the specific structure and applicable scope shown and described. Therefore, all corresponding modifications and equivalents that may be utilized fall within the scope of the patent application of the present invention.

Claims

1. A core orientation device for testing in-situ stress in railway tunnels, characterized by: The core orientation device comprises an outer shell (10) having the same diameter as the outer tube of the core tube, wherein the internal structure of the outer shell (10) is sequentially composed of an upper inner shell (11), a middle base (12) and a lower annular cavity (13) from top to bottom, and the upper end of the outer shell (10) is connected to the drill rod via a threaded structure; an annular water inlet cavity (14) is formed between the outer wall of the upper inner shell (11) and the inner wall of the outer shell (10), and an electronic compass installation chamber (16) is provided in the upper inner shell (11); and two groups of hydraulic rotary drilling marking mechanisms are installed on the middle base (12) at intervals along the radial direction.

2. The rock core orientation device in a railway tunnel in-situ stress test hole according to claim 1, characterized in that: The hydraulic rotary drilling marking mechanism comprises a rotating shaft (30), a hydraulic rotary wheel (31) and a small drill bit (32); the rotating shaft (30) vertically passes through the middle base (12) and enters the lower annular cavity (13); the hydraulic rotary wheel (31) is fixedly arranged at the lower end of the rotating shaft (30); and the small drill bit (32) is installed at the lower end of the hydraulic rotary wheel (31) through a threaded structure; the rotating shaft (30) has an axial water-filled core hole (33) whose upper end is connected to the annular water inlet cavity (14); and the lower end of the axial water-filled core hole (33) is connected to a radial water spraying pipeline (34) on the hydraulic rotary wheel (31).

3. The rock core orientation device in a railway tunnel in-situ stress test hole according to claim 2, characterized in that: The rotating shaft (30) is mounted on the middle base (12) via a bearing (36), an elastic device (35) is provided between the lower portion of the rotating shaft (30) and the middle base (12), and a sealing ring (37) is provided at the contact surface between the upper portion of the rotating shaft (30) and the middle base (12) and at the contact surface between the upper portion of the elastic device (35) and the middle base (12).

4. The rock core orientation device in a railway tunnel in-situ stress test hole according to claim 2, characterized in that: There are four radial water spray pipes (34), the water inlets and outlets of which form a 90° angle, and the four outlets are distributed at equal intervals in the tangential direction of the outer circumference of the hydraulic rotary wheel (31).

5. The rock core orientation device in a railway tunnel in-situ stress test hole according to claim 1, characterized in that: A sealing cover (15) threadedly connected to the upper end of the upper inner shell (11) is provided, an electronic compass (20) is installed in the electronic compass installation chamber (16), and a buffer pad (21) is provided between the electronic compass (20) and the chamber wall.

6. The rock core orientation device in a railway tunnel in-situ stress test hole according to claim 1, characterized in that: The outer shell (10), the upper inner shell (11) and the sealing cover (15) are made of non-magnetic materials.

7. A test method using the core orientation device in a railway tunnel in-situ stress test hole according to any one of claims 1 to 6, comprising the following steps: Step S1: Determine whether the drilling hole is a deep hole in the survey and design stage or a hole drilled in the tunnel during the construction and operation stage; Step S2: When the borehole is a deep hole in the survey and design stage, the integrity of the core of the most recent drilling pass is observed every Sm. If the core is complete, a core directional device is installed and directional coring is carried out. The depth of one directional coring should be less than 50m perpendicular to the tunnel axis. S = (500*H) / (1500+H), where H is the designed hole depth. If the drilling is done inside a tunnel during construction or operation, when the vertical distance from the tunnel sidewall or floor to the drilling depth is greater than twice the tunnel diameter, the integrity of the core from the most recent drilling pass shall be observed. If the core is intact, a core orientation device shall be installed to conduct directional coring. When observing the integrity of the core from the most recent drilling pass, if the core is incomplete, continue drilling until a complete core is obtained; Step S3: When installing the in-hole core orientation device, remove the original coring tube and install the in-hole core orientation device on the lower thread of the drill pipe, and start the electronic compass (20); Step S4: Use a drilling rig and a drill pipe to deliver the in-hole core orientation device to the bottom of the hole, and apply a pressure greater than 1 MPa with water through the drill pipe to start the in-hole core orientation device to work; Step S5: Observe the depth of the drill rod descent, estimate that the core orientation device has marked an identifiable mark on the rock section at the bottom of the hole, then lift the drill rod, remove the core orientation device in the hole, replace it with a coring drill bit, and drill the marked core. Step S6: Determine the orientation of the line connecting the two marked points of the marked core in combination with the time and orientation data recorded by the electronic compass (20), thereby obtaining the original spatial orientation of the core; Step S7: Conducting a geostress test based on oriented core drilling to obtain the magnitude and direction of the in-situ stress in the tunnel.

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