Weak rock mass crustal stress testing equipment based on distributed hydraulic pillow monitoring

Abstract

A weak rock mass crustal stress testing device based on distributed hydraulic pillow monitoring comprises double-face pressed hydraulic pillows buried in drill holes in the side wall or the tunnel face of a tunnel, and at least three double-face pressed hydraulic pillows with different installation angles are buried in each drill hole; the double-sided pressed hydraulic pillow comprises a main body, pressure-bearing plates, pressure-bearing liquid, a pressure conversion device connecting port, a one-way valve and a sealing nut connecting screw, the pressure-bearing plates cover the two sides of the main body, and the pressure-bearing liquid is located in the main body; the two ends of the main body are detachably connected with mounting rods; the one-way valve and sealing nut connecting screw is connected with the one-way valve and the sealing nut; the double-faced pressed hydraulic pillows are buried in a grouting mode; a pressure conversion device is installed on the pressure conversion device connector and connected with a data acquisition instrument through a cable. The utility model can solve the problems that the grouting quality is influenced by the combination of the one-way hydraulic pillows, and the representativeness of the test result is insufficient.

Description

Technical Field

[0001] The utility model relates to the field of geotechnical tests, and specifically relates to a soft rock in-situ stress testing device based on distributed hydraulic pillow monitoring. Background Art

[0002] In-situ stress is one of the controlling factors for the deformation and failure of surrounding rocks in underground engineering. Under high to extremely high in-situ stress conditions, brittle rocks are prone to rock bursts, and soft rocks are prone to large deformation failures of soft rocks. With the advancement of long-distance water diversion projects, transportation projects, and deep mine projects in China, large deformations of surrounding rocks of soft rocks and frequent accidents of TBM tunneling jamming have occurred. Obtaining in-situ stress data of typical soft rocks such as fault zones has become an engineering problem that urgently needs to be solved.

[0003] Currently, the methods for measuring in-situ stress of soft rocks include triaxial pressure cells, hydraulic borehole stress meters, and combined single-direction hydraulic pillows. Among them, the combined single-direction hydraulic pillow directly measures the unidirectional compressive stress of soft rocks and calculates the two-dimensional stress by combination. Practical applications show that when the planes of the combined single-direction hydraulic pillows are put together, it is easy to affect the grouting backfill effect, and further affect the stress coupling between the rock mass and the hydraulic pillow and the test effect. Summary of the Utility Model

[0004] Aiming at the deficiencies of the existing combined single-direction hydraulic pillow in measuring in-situ stress of soft rocks, the utility model provides a soft rock in-situ stress testing device based on distributed hydraulic pillow monitoring, which realizes double-sided compression of the hydraulic pillow, signal conversion, improves the test sensitivity, can arrange multiple double-sided compressed hydraulic pillows in the borehole, and realizes the function of combined testing of the rock mass stress field. The utility model can solve the problem that the combination of single-direction hydraulic pillows affects the grouting quality, thereby resulting in insufficient representativeness of the test results.

[0005] To achieve the above object, the utility model adopts the following technical solutions:

[0006] A soft rock in-situ stress testing device based on distributed hydraulic pillow monitoring, comprising: double-sided compressed hydraulic pillows buried in the side walls or faces of the tunnels, and at least three double-sided compressed hydraulic pillows with different installation angles are buried in each borehole; the double-sided compressed hydraulic pillow includes a main body, a bearing plate, a bearing liquid, a pressure conversion device connection port, a one-way valve, and a sealing nut connection screw. The main body is a square frame structure, the bearing plates cover both sides of the main body, and the bearing liquid is located inside the main body; installation rods are detachably connected to both ends of the main body; the one-way valve and the sealing nut connection screw are connected to the one-way valve and the sealing nut, and the one-way valve and the sealing nut are used to inject the bearing liquid into the main body of the double-sided compressed hydraulic pillow; space cement stones are filled between the borehole and the double-sided compressed hydraulic pillow; a pressure conversion device is installed at the pressure conversion device connection port, and the pressure conversion device is connected to a data acquisition instrument through a cable.

[0007] Furthermore, the main body is made of metal material, and the bearing plate is made of paper steel plate.

[0008] Furthermore, the double-sided compression hydraulic pillow further includes a cable pipeline and a grouting channel fixed to the side of the main body. The grouting channel is connected to a grouting pipe until outside the orifice. Cement stones are formed by grouting into the space between the double-sided compression hydraulic pillow and the drilling hole through the grouting pipe and the grouting channel. When the cable passes through other double-sided compression hydraulic pillows, it is placed in the cable pipeline and passes through.

[0009] Furthermore, the double-sided compression hydraulic pillow further includes lower connection threads and upper connection threads provided at both ends of the main body. The specifications of the connection threads at both ends of the installation rod are consistent with the upper connection threads and the lower connection threads of the double-sided compression hydraulic pillow.

[0010] Furthermore, the pressure-bearing liquid is hydraulic oil, water, or a mixed liquid of hydraulic oil and water.

[0011] The utility model reasonably arranges the cables and grouting channels of a single hydraulic pillow, realizes double-sided compression of the hydraulic pillow and can be spread along the axis of the drilling hole. The double-sided compression hydraulic pillow has the same force-measuring principle as the combined single-direction hydraulic pillow, can be double-sided compressed, has a larger force-bearing area than the single-direction hydraulic pillow under the same hydraulic pillow size and the same compression conditions, can be fully coupled with the rock mass, and can generate a more sensitive pressure feedback. It is a brand-new design for the structure of the single-direction combined hydraulic pillow; multiple double-sided compression hydraulic pillows are spread along the axial direction of the drilling hole, the hydraulic pillows are dispersed, and when grouting, they are double-sided bathed in the grouting material. After solidification, they can bear pressure on both sides, while the structure of the combined single-direction hydraulic pillow is dense and compact, and it is easy for the grouting liquid to be unevenly distributed among the hydraulic pillows. The double-sided compression hydraulic pillow has a better grouting effect than the single-direction hydraulic pillow, is sensitive to reflecting the rock mass stress, and has a good monitoring effect; the pressure conversion device and the one-way valve can solve the problems of hydraulic preloading, full sealing of the liquid, and measurement of the hydraulic pressure. The test pressure is locally converted into an electrical signal by using the pressure conversion device, reducing the measurement error caused by the pressure loss due to the long oil pipe. Description of the Drawings

[0012] Figure 1 is a schematic diagram of the three-dimensional in-situ stress detection layout based on the distributed double-sided compression hydraulic pillow monitoring in an embodiment of the utility model;

[0013] Figure 2 In (a), it is the front view of the double-sided compression hydraulic pillow in an embodiment of the utility model, (b) is the top view of the double-sided compression hydraulic pillow in an embodiment of the utility model, and (c) is the left view of the double-sided compression hydraulic pillow in an embodiment of the utility model;

[0014] Figure 3 is the pressure calibration curve of the double-sided compression hydraulic pillow in an embodiment of the utility model;

[0015] Figure 4 It is the relationship between a single double-sided pressure hydraulic pillow and the rock mass and its coordinate system axis o-x after the single double-sided pressure hydraulic pillow is buried in the embodiments of the present utility model. i y i Schematic diagram;

[0016] Figure 5 It is the relationship between a single double-sided pressure hydraulic pillow and the drilling coordinate system o-x in the embodiments of the present utility model. i y i z i And the relationship diagram of the geodetic coordinate system o-xyz.

[0017] The reference numerals in the figure are described separately as follows:

[0018] 1 - Tunnel, 2 - Borehole, 3 - Grouting pipe, 4 - Installation rod, 5 - Cable, 6 - Check valve and sealing nut, 7 - Pressure conversion device, 8 - Double-sided pressure hydraulic pillow, 9 - Cement stone, 81 - Main body, 82 - Bearing plate, 83 - Pressurized liquid, 84 - Lower connection thread, 85 - Upper connection thread, 86 - Pressure conversion device connection port, 87 - Cable conduit, 88 - Check valve and sealing nut connection screw, 89 - Grouting channel. Specific implementation manner

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. Usually, the components of the embodiments of the present utility model described and illustrated herein can be arranged and designed in various different configurations.

[0020] As Figure 1 shown, the embodiments of the present utility model provide a weak rock mass in-situ stress testing device based on distributed hydraulic pillow monitoring. At least three boreholes 2 with different dip angles and azimuth angles are provided on the side wall or the heading face of the tunnel 1. The three boreholes in this embodiment are respectively named ZK1, ZK2, and ZK3 for burying the double-sided pressure hydraulic pillow 8. The axial angles of each borehole 2 should intersect at large angles, preferably arranged perpendicular to each other. Each borehole 2 buries at least 3 double-sided pressure hydraulic pillows 8 with different installation angles, and it is advisable to arrange them at a 60° angle. Each borehole 2 in this embodiment can obtain two-dimensional stress data of a borehole cross-section, and the entire implementation scheme is an embodiment of a three-dimensional in-situ stress acquisition scheme. The double-sided pressure hydraulic pillow 8 is communicatively connected to the data acquisition instrument at the hole mouth.

[0021] As Figure 2As shown in (a) and (b) of the figure, this embodiment provides a double-sided pressure-bearing hydraulic pillow (i.e., the double-sided pressure-bearing hydraulic pillow 8). Both sides of the double-sided pressure-bearing hydraulic pillow 8 can bear pressure and deform, and the cable conduit and the grouting pipe are arranged on both sides. The double-sided pressure-bearing hydraulic pillow 8 includes a main body 81, a bearing plate 82, a pressure-bearing liquid 83, a lower connecting thread 84, an upper connecting thread 85, a pressure conversion device connection port 86, a cable conduit 87, a check valve and a sealing nut connecting screw 88, and a grouting channel 89.

[0022] The main body 81 is a square frame structure and is made of metal material. The bearing plate 82 can be a paper steel plate with different thicknesses and covers both sides of the main body 81. The main body 81 and the bearing plate 82 of the double-sided pressure-bearing hydraulic pillow can be processed by single-sided welding or formed by integral 3D printing; the pressure-bearing liquid 83 is located inside the main body 81.

[0023] Please refer to Figure 1 、 Figure 2 and Figure 4 together. The cable conduit 87 and the grouting channel 89 are fixed to the side of the main body 81.

[0024] The pressure conversion device connection port 86 is used to install the pressure conversion device 7. The pressure of the pressure-bearing liquid 83 in the double-sided pressure-bearing hydraulic pillow 8 is sensed by the pressure conversion device 7, and the relevant information is connected by the cable 5 to the data acquisition instrument at the orifice. When the cable 5 passes through other double-sided pressure-bearing hydraulic pillows, it should be placed in the cable conduit 87 and pass through. The data acquisition instrument transmits the pressure data to the data processing device to calculate the in-situ stress in different dimensions.

[0025] The check valve and the sealing nut connecting screw 88 are used to connect the check valve and the sealing nut 6. The check valve and the sealing nut 6 are used to inject the pressure-bearing liquid 83 into the main body 81 of the double-sided pressure-bearing hydraulic pillow 8. The pressure-bearing liquid 83 is hydraulic oil, water, or a mixed liquid of hydraulic oil and water.

[0026] The grouting channel 89 of the double-sided pressure-bearing hydraulic pillow 8 is connected to the grouting pipe 3 until outside the orifice. The double-sided pressure-bearing hydraulic pillow 8 is buried in the drill hole 2 by grouting, and the space between the drill hole 2 and the double-sided pressure-bearing hydraulic pillow 8 is filled with cement stone 9. The cement stone 9 is used to couple the stress fields of the rock mass and the double-sided pressure-bearing hydraulic pillow 8.

[0027] The installation rod 4 is connected by rods of equal length and adopts a threaded connection form. The specification of the connecting thread is the same as that of the upper connecting thread 85 and the lower connecting thread 84 of the double-sided pressure-bearing hydraulic pillow 8.

[0028] When using the present utility model for in-situ stress testing based on distributed double-sided pressure-bearing hydraulic pillow monitoring, the following steps are included:

[0029] Step 1. Determine the test plan based on the distributed double-sided compression hydraulic pillow: Determine the number of drill holes and the drill hole layout plan, the layout plan and quantity of the double-sided compression hydraulic pillows. Through the combination of hydraulic pillows and drill hole layout, the test requirements can be met, and the measurement of 1D to 3D in-situ stress information can be achieved.

[0030] The combination of the double-sided compression hydraulic pillows refers to the combination of the double-sided compression hydraulic pillows according to the measurement requirements. The unidirectional stress in any radial direction of the measurement drill hole or the plane stress of the drill hole cross-section can be selected. A single double-sided compression hydraulic pillow ( Figure 4 as shown) can perform unidirectional stress measurement; for a single drill hole, three or more double-sided compression hydraulic pillows with different installation angles (such as Figure 1 the combination of 3 double-sided compression hydraulic pillows shown) can perform the measurement of the plane stress of the drill hole cross-section.

[0031] The drill hole layout refers to arranging multiple test drill holes on the tunnel wall or the heading face according to the test requirements, numbered as i; installing three or more double-sided compression hydraulic pillows (numbered as j) with different installation angles in a single test drill hole, multiple unidirectional compressive stresses or plane stresses in the drill hole cross-section can be obtained, and the spatial three-dimensional stress can be calculated by combining the plane stresses obtained from more than three drill holes in different directions.

[0032] Step 2. Prepare and calibrate the double-sided compression hydraulic pillow, including the following steps:

[0033] (1) Air tightness test of the double-sided compression hydraulic pillow 8: After the double-sided compression hydraulic pillow is processed, connect the one-way valve and the sealing nut 6 to the main body 81 of the double-sided compression hydraulic pillow through the connecting screw 88 of the one-way valve and the sealing nut, connect the other end to the oil pump, inject the pressure-bearing liquid 83 into the double-sided compression hydraulic pillow 8 through the one-way valve. During the injection process, exhaust completely through the pressure conversion device connection port 86, and then connect the pressure conversion device 7, apply pre-pressure to the double-sided compression hydraulic pillow 8 and maintain the pressure for a long time to check the air tightness of the hydraulic pillow.

[0034] (2) Pressure calibration test: Under the condition of the pressure machine or simulating the stress state of the rock mass in the field test, conduct a calibration test on the double-sided compression hydraulic pillow 8 to obtain the relationship between the test loading and the output pressure under a specific preloading pressure, that is, Figure 3 the fitting coefficients a j and b j in the relational expression;

[0035] Step 3. Bury the hydraulic pillow and observe the data, including the following steps:

[0036] (1) Drill hole preparation: Carry out drill hole construction according to the drill hole layout plan, ensure that the hole diameter is suitable, and drill the hole according to the predetermined plan;

[0037] (2) Installation: Install several double-sided hydraulic pillows that have been calibrated and numbered (j) in the drilled holes, and record the installation depth and angle data of the double-sided hydraulic pillows (α j );

[0038] (3) Grouting backfill: Grouting backfill is performed on the borehole to make the observation device and the rock mass condense into one. The physical parameters of the grout material should be as consistent as possible with the rock mass parameters;

[0039] (4) Stress observation: Continuously observe the pressure changes of each double-sided pressure pillow 8 and record the pressure change data over time;

[0040] Step 4: Stress calculation, including the following steps:

[0041] (1) Draw the pressure variation curve of the double-sided hydraulic pillow over time to determine the stable stress p of the hydraulic pillow j , and then according to the fitting coefficient a obtained from the pressure calibration test j and b j The value of the hydraulic pillow stability stress p in the stable stage j Back-calculation of the uniaxial compressive stress σ of the rock mass reflected by the double-sided hydraulic pillow n j;

[0042] (2) Combine the measurement results of the double-sided hydraulic pillow and calculate the ground stress in different dimensions according to the test arrangement.

[0043] Generally speaking, caverns have a disturbing effect on the initial stress field of nearby rock masses, and the burial of measuring devices has an "embedded effect" on the measurement, both of which affect the accuracy of the measurement results. The device design and test layout should try to avoid the above influences. Figure 4 and Figure 5 The plane coordinate system ox of the drilled cross section is shown i y i , axis x i is horizontal to the right, axis y i Vertically upward. Without considering the above effects, Figure 4 The unidirectional compressive stress obtained by the single double-sided pressure hydraulic pillow combination is shown in formula (1), Figure 4 The plane stress measurement results of the drilled hole cross section are shown in formula (2).

[0044] σ nj =a j ·p j +b j (1)

[0045]

[0046] In the formula, σ n1 , σ n2 , and σn3 is the unidirectional compressive stress in the normal direction of three double-sided compressed hydraulic pillows in a borehole, σ 1 is the major principal stress of the borehole cross-section, σ 2 is the minor principal stress of the borehole cross-section, the angle ɑ is the major principal stress direction angle, which is the angle rotated counterclockwise from the axis x i to the major principal stress direction.

[0047] Three-dimensional stress calculation requires the establishment of a geodetic coordinate system o-xyz and a borehole coordinate system o Figure 5 as shown, where the bearing surface of the jth double-sided compressed hydraulic pillow has the relationship with the geodetic and borehole coordinate systems as shown in the figure. The observed value equation of a single double-sided compressed hydraulic pillow is shown in Equation (3). In the equation, σ i -x i y i z i , where σ x , σ y , σ z , τ xy , τ yz and τ zx are the spatial stress components in the coordinate system O-xyz; A k1 ~A k6 are stress coefficients, and their values are shown in Equation (4), where α j is the inclination angle of the jth double-sided compressed hydraulic pillow (or the buried borehole), β 0 is the azimuth of the x-axis of the coordinate system O-xyz, and β i is the axial azimuth of the equipment buried borehole;

[0048] σ nj =A k1 σ x +A k2 σ y +A k3 σ z +A k4 τ xy +A k5 τ yz +A k6 τ zx (3)

[0049] A k1 ~A k6 take the values shown in Equation (4);

[0050] A k1 =sin 2 (β 0 -β i )

[0051] A k2 =cos 2 (β0 -β i )

[0052] A k3 =cos 2 α j

[0053] A k4 =-sin2(β 0 -β i )]sin 2 α j (4)

[0054] A k5 =cos(β 0 -β i )sin2α j

[0055] A k6 =-sin(β 0 -β i )sin2α j

[0056] In the formula, σ nj is the normal stress of the double-sided compression hydraulic pillow with serial number j, α j is the installation angle of the double-sided compression hydraulic pillow, and β i is the trend of the plane of the double-sided compression hydraulic pillow; assuming there are a double-sided compression hydraulic pillows in total, solve the optimal values of the stress components σ x , σ y , … τ zx The normal equations are shown in Equation (5):

[0057]

[0058] In the formula, σ* is the observed value and is the left side term of Equation (3). After solving the optimal values of the stress components, the calculation of the residuals and standard errors of the observed values, and the calculation of the three-dimensional principal stress magnitudes and their directions can be further carried out. This utility model will not elaborate further.

[0059] The above is only the specific implementation manner of this utility model, but the protection scope of this utility model is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by this utility model should be covered within the protection scope of this utility model.

Claims

1. A soft rock mass in-situ stress testing device based on distributed hydraulic pillow monitoring, characterized in that: include: A double-sided pressure hydraulic pillow buried in a borehole on the side wall or face of a tunnel, with at least three double-sided pressure hydraulic pillows of different installation angles buried in each borehole; the double-sided pressure hydraulic pillow comprises a main body, a pressure-bearing plate, a pressure-bearing liquid, a pressure conversion device connection port, a one-way valve and a sealing nut connecting screw, the main body is a square frame structure, the pressure-bearing plate covers both sides of the main body, and the pressure-bearing liquid is located inside the main body; the two ends of the main body are detachably connected with a mounting rod; the one-way valve and the sealing nut connecting screws are connected to the one-way valve and the sealing nut, and the one-way valve and the sealing nut are used to inject pressure liquid into the main body of the double-sided pressure hydraulic pillow; the double-sided pressure hydraulic pillow is buried by grouting, and cement stones are filled between the borehole wall and the double-sided pressure hydraulic pillow; the pressure conversion device connection port is installed with a pressure conversion device, and the pressure conversion device is connected to a data acquisition instrument via a cable.

2. The soft rock mass in-situ stress testing device based on distributed hydraulic pillow monitoring according to claim 1 is characterized in that: The main body is made of metal material, and the pressure-bearing plate is a paper steel plate.

3. The soft rock mass in-situ stress testing device based on distributed hydraulic pillow monitoring according to claim 1 is characterized in that: The double-sided pressure hydraulic pillow also includes a cable conduit and a grouting channel fixed to the side of the main body. The grouting channel is connected to the grouting pipe to the outside of the hole. The space between the double-sided pressure hydraulic pillow and the drill hole is grouted through the grouting pipe and the grouting channel to form cement stone. When the cable passes through other double-sided pressure hydraulic pillows, it is placed in the cable conduit.

4. The soft rock mass in-situ stress testing device based on distributed hydraulic pillow monitoring according to claim 1, characterized in that: The double-sided pressure hydraulic pillow also includes a lower connecting thread and an upper connecting thread arranged at both ends of the main body, and the specifications of the connecting threads at both ends of the mounting rod are consistent with the upper connecting thread and the lower connecting thread of the double-sided pressure hydraulic pillow.

5. The soft rock mass in-situ stress testing device based on distributed hydraulic pillow monitoring according to claim 1, characterized in that: The pressure-bearing liquid is hydraulic oil, water or a mixed liquid of hydraulic oil and water.

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