Ground stress testing equipment and method based on distributed double-sided pressure hydraulic pillow monitoring

Abstract

The present invention provides a ground stress testing device and method based on distributed double-sided pressure hydraulic pillow monitoring. The device includes: 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 at different installation angles buried in each borehole; the double-sided pressure hydraulic pillow includes a main body, a pressure plate, a pressure-bearing liquid, a pressure conversion device connection port, a one-way valve, and a sealing nut connecting screw; the one-way valve and sealing nut are used to inject the pressure-bearing liquid into the main body of the double-sided pressure hydraulic pillow; a pressure conversion device is installed at the pressure conversion device connection port and is used to sense the pressure of the pressure-bearing liquid; a cable is connected to the pressure conversion device for communicating and transmitting the sensed pressure data to a data acquisition instrument at the orifice; and a data processing device is used to calculate ground stress in different dimensions based on the pressure data. The present invention can solve the problem that the combination of one-way hydraulic pillows affects the grouting quality, thereby resulting in insufficient representativeness of the test results.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical testing, and in particular to a ground stress testing device based on distributed double-sided pressure hydraulic pillow monitoring and an implementation method thereof. Background Art

[0002] In-situ stress is one of the factors controlling deformation and failure of surrounding rock in underground engineering projects. Under high to extremely high in-situ stress conditions, hard and brittle rock masses are prone to rockbursts, while weak rock masses are prone to large deformation and failure. Acquiring in-situ stress data for typical weak rock masses, such as those in fault zones, has become an urgent engineering challenge.

[0003] Currently, methods for measuring in-situ stress in weak rock masses include three-dimensional pressure cells, hydraulic borehole stress gauges, and combined unidirectional hydraulic pillows. The combined unidirectional hydraulic pillow directly measures the unidirectional compressive stress in the weak rock mass and combines this with the calculation of two-dimensional stress. However, practical applications have shown that the combined planes of the combined unidirectional hydraulic pillow can affect the grouting backfill effect, which in turn affects the stress coupling between the rock mass and the pillow, and the test results. Summary of the Invention

[0004] In view of the shortcomings of existing combined unidirectional hydraulic pillows in measuring ground stress in weak rock masses, the present invention provides a ground stress monitoring device and implementation method based on a distributed double-sided pressure hydraulic pillow, which realizes double-sided pressure of the hydraulic pillow, signal conversion, and improved test sensitivity. Multiple double-sided pressure hydraulic pillows can be arranged in the borehole, realizing the function of combined testing of rock stress field. The present invention can solve the problem that the combination of unidirectional hydraulic pillows affects the grouting quality, thereby resulting in insufficient representativeness of the test results.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A ground stress testing device based on distributed double-sided pressure hydraulic pillow monitoring, comprising:

[0007] Double-sided pressure hydraulic pillows are buried in drilled holes on the side walls or face of the tunnel, with at least three double-sided pressure hydraulic pillows at different installation angles buried in each drilled hole. The double-sided pressure hydraulic pillows include a main body, a pressure-bearing plate, a pressure-bearing liquid, a pressure conversion device connection port, a one-way valve, and sealing nut connection screws. The main body is a square frame structure, with the pressure-bearing plates covering both sides of the main body, and the pressure-bearing liquid located inside the main body.

[0008] A mounting rod detachably connected to both ends of the main body;

[0009] The one-way valve and the sealing nut are connected to the one-way valve and the sealing nut connecting screws, and are used to inject the pressurized liquid into the main body of the double-sided pressure hydraulic pillow;

[0010] The double-sided pressure hydraulic pillow is buried in the borehole by grouting, and the space between the borehole and the double-sided pressure hydraulic pillow is filled with cement and stone to couple the stress fields of the rock mass and the double-sided pressure hydraulic pillow.

[0011] A pressure conversion device, installed at the connection port of the pressure conversion device, for sensing the pressure of the pressurized liquid;

[0012] an electric cable, communicatively connected to the pressure conversion device, for transmitting the sensed pressure data to a data acquisition instrument at the orifice;

[0013] The data processing device is used to draw the pressure change curve of the double-sided hydraulic pillow over time based on the pressure data transmitted by the data acquisition instrument, and 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 pressure hydraulic pillow nj ; Combine the measurement results of the double-sided pressure hydraulic pillow and calculate the ground stress in different dimensions according to the test arrangement.

[0014] Furthermore, the main body is made of metal material, and the pressure plate is a paper steel plate.

[0015] Furthermore, 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.

[0016] Furthermore, the double-sided pressure hydraulic pillow also includes a lower connecting thread and an upper connecting thread provided 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.

[0017] Furthermore, the pressure-bearing liquid is hydraulic oil, water, or a mixture of hydraulic oil and water.

[0018] Furthermore, the data processing device is specifically used for:

[0019] The unidirectional compressive stress σ obtained by calculating a single double-sided pressure hydraulic pillow combination according to formula (1) is: nj ;

[0020] The plane stress measurement result of the drilled cross section is (2):

[0021] σnj=a j ·p j +bj (1)

[0022]

[0023] Where, σ n1 , σ n2 , and σ n3 is the unidirectional compressive stress in the normal direction of three double-sided hydraulic pillows in a borehole, σ1 is the major principal stress of the borehole cross section, σ2 is the minor principal stress of the borehole cross section, and angle ɑ is the maximum principal stress direction angle, which is the angle with axis x. i The angle from the start to the maximum principal stress direction is counterclockwise, σ nj is the unidirectional compressive stress of the double-sided hydraulic pillow with serial number j;

[0024] When calculating three-dimensional stress, the geodetic coordinate system o-xyz and the drilling coordinate system o are established. i -x i y i z i , the observation value equation of a single double-sided pressure hydraulic pillow is shown in formula (3):

[0025] 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)

[0026] Where, σ x , σ y , σ z , τ xy , τ yz and τ zx is the spatial stress component in the coordinate system O-xyz; A k1 ~A k6 is the stress coefficient, and its value is shown in formula (4), where α j is the inclination angle of the j-th double-sided hydraulic pillow, β0 is the x-axis orientation of the coordinate system O-xyz, β i Axial orientation of the borehole for burying the equipment;

[0027]

[0028] Where, α j is the installation angle of the double-sided pressure hydraulic pillow, β iis the direction of the double-sided hydraulic pillow plane; suppose there are a double-sided hydraulic pillows, solve the optimal value of stress component σ x , σ y ,…τ zx The normal equations of are shown in formula (5):

[0029]

[0030] Where σ* is the observed value, which is the left side term of formula (3).

[0031] A method for testing ground stress based on distributed double-sided pressure hydraulic pillow monitoring, characterized in that the above-mentioned equipment is used, and the method includes the following steps:

[0032] Step 1: Determine the test plan based on the distributed double-sided pressure hydraulic pillow: determine the number of drill holes and the drilling arrangement, the arrangement and number of double-sided pressure hydraulic pillows, and achieve the test requirements through the combination of hydraulic pillows and drilling arrangement to realize the measurement of 1D to 3D ground stress information;

[0033] Step 2: Preparation and calibration test of double-sided pressure hydraulic pillow, including the following steps:

[0034] (1) Air tightness test of double-sided pressure hydraulic pillow: After the double-sided pressure hydraulic pillow is processed, connect the one-way valve and sealing nut to the double-sided pressure hydraulic pillow body through the one-way valve and sealing nut connecting screws, connect the other end to the oil pump, and inject pressurized liquid into the double-sided pressure hydraulic pillow through the one-way valve. During the injection process, the air must be completely exhausted through the connection port of the pressure conversion device. Then connect the pressure conversion device, pre-pressurize the double-sided pressure hydraulic pillow and maintain the pressure for a long time to test the air tightness of the hydraulic pillow;

[0035] (2) Pressure calibration test: Under the rock mass stress state of the press or simulated field test conditions, the double-sided pressure hydraulic pillow is calibrated to obtain the relationship between the test load and output pressure under a specific preload pressure, and the fitting coefficient a in the relationship between the test load and output pressure is obtained. j and b j ;

[0036] Step 3: Hydraulic pillow installation and data observation, including the following steps:

[0037] (1) Drilling preparation: Drilling is carried out according to the drilling arrangement plan to ensure that the hole diameter is suitable and the holes are drilled according to the predetermined plan;

[0038] (2) Installation: Install multiple calibrated and numbered double-sided pressure hydraulic pillows in the drilled holes, and record the installation depth and angle data of the double-sided pressure hydraulic pillows;

[0039] (3) Grouting backfill: Grouting backfill is performed on the borehole to integrate the observation device with the rock mass. The physical parameters of the grout material should be as consistent as possible with the rock mass parameters.

[0040] (4) Stress observation: Continuously observe the pressure changes of each double-sided pressure pillow and record the pressure change data over time;

[0041] Step 4: Stress calculation, including the following steps:

[0042] (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 pressure hydraulic pillow nj ;

[0043] (2) Combine the measurement results of the double-sided pressure hydraulic pillow and calculate the ground stress in different dimensions according to the test arrangement.

[0044] Furthermore, step four specifically includes:

[0045] The unidirectional compressive stress σ obtained by a single double-sided hydraulic pillow combination nj is (1), and the plane stress measurement result of the drilled cross section is (2),

[0046] σnj=a j ·p j +b j (1)

[0047]

[0048] Where σ n1 , σ n2 , and σ n3 is the unidirectional compressive stress in the normal direction of three double-sided hydraulic pillows in a borehole, σ1 is the major principal stress of the borehole cross section, σ2 is the minor principal stress of the borehole cross section, and angle ɑ is the maximum principal stress direction angle, which is the angle with axis x. i The angle from the start to the maximum principal stress direction is counterclockwise, σ nj is the unidirectional compressive stress of the double-sided hydraulic pillow with serial number j;

[0049] When calculating three-dimensional stress, the geodetic coordinate system o-xyz and the drilling coordinate system o are established. i -x i y i z i , the observation value equation of a single double-sided pressure hydraulic pillow is shown in formula (3):

[0050] 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)

[0051] Where σ x , σ y , σ z , τ xy , τ yz and τ zx is the spatial stress component in the coordinate system O-xyz; A k1 ~A k6 is the stress coefficient, and its value is shown in formula (4), where α j is the inclination angle of the j-th double-sided hydraulic pillow, β0 is the x-axis orientation of the coordinate system O-xyz, β i Axial orientation of the borehole for burying the equipment;

[0052]

[0053] Where, α j is the installation angle of the double-sided pressure hydraulic pillow, β i is the direction of the double-sided hydraulic pillow plane; suppose there are a double-sided hydraulic pillows, solve the optimal value of stress component σ x , σ y ,…τ zx The normal equations of are shown in formula (5):

[0054]

[0055] Where σ* is the observed value, which is the left side term of formula (3).

[0056] The present invention has the following beneficial effects:

[0057] ① The cables and grouting channels of a single hydraulic pillow are rationally arranged to achieve double-sided pressure on the hydraulic pillow and to extend it along the borehole axis. The double-sided pressure hydraulic pillow has the same force measurement principle as the combined unidirectional hydraulic pillow and can bear pressure on both sides. Compared with the unidirectional hydraulic pillow of the same hydraulic pillow size and under the same pressure conditions, it has a larger force-bearing area, can fully couple with the rock mass, and can generate more sensitive pressure feedback. It is a new design for the unidirectional combined hydraulic pillow structure;

[0058] ② Multiple double-sided pressure hydraulic pillows are distributed along the borehole axis. The hydraulic pillows are dispersed, and both sides are bathed in slurry during grouting. After the stone is formed, both sides can withstand pressure. The combined unidirectional hydraulic pillow has a dense and compact structure, and the slurry is easily unevenly distributed between the hydraulic pillows. The double-sided pressure hydraulic pillow has a better grouting effect than the unidirectional hydraulic pillow, reflects the rock stress sensitively, and has a good monitoring effect.

[0059] ③The pressure conversion device and the one-way valve solve the problems of hydraulic preloading, full sealing of the liquid and hydraulic measurement. The pressure conversion device is used to convert the test pressure into an electrical signal on site, reducing the measurement error caused by the pressure loss caused by the long oil pipe.

[0060] ④ The distributed double-sided pressure hydraulic pillow is flexible in arrangement and can obtain 1D to 3D ground stress data. The present invention specifically provides a calculation method for 3D stress measurement using a distributed hydraulic pillow, which can fully meet the needs of survey and design for ground stress data;

[0061] ⑤ This invention addresses the drawback of combined unidirectional hydraulic pillow measurement technology, which can easily lead to incomplete grouting. Through technological innovation, it effectively enhances the stress coupling between the rock mass stress field and the hydraulic pillow, making the hydraulic pillow more sensitive to pressure and reducing measurement errors. Reliable geostress detection technology for weak rock masses is currently unavailable, and this technology can effectively improve its detection effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a schematic diagram of a three-dimensional ground stress detection arrangement based on distributed double-sided pressure hydraulic pillow monitoring according to an embodiment of the present invention;

[0063] Figure 2 (a) is a front view of a double-sided pressure hydraulic pillow according to an embodiment of the present invention, (b) is a top view of a double-sided pressure hydraulic pillow according to an embodiment of the present invention, and (c) is a left view of a double-sided pressure hydraulic pillow according to an embodiment of the present invention;

[0064] Figure 3 is a pressure calibration curve of a double-sided pressure hydraulic pillow in an embodiment of the present invention;

[0065] Figure 4 The relationship between a single double-sided pressure hydraulic pillow and the rock mass and its coordinate system axis ox after the double-sided pressure hydraulic pillow is buried in the embodiment of the present invention i y i Schematic diagram;

[0066] Figure 5 The embodiment of the present invention is a single double-sided pressure hydraulic pillow and a drilling coordinate system ox i y i z i , the relationship diagram of the geodetic coordinate system o-xyz.

[0067] The reference numerals in the figures are described as follows:

[0068] 1—tunnel, 2—drill hole, 3—grouting pipe, 4—mounting 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—pressure plate, 83—pressure liquid, 84—lower connecting thread, 85—upper connecting thread, 86—connecting port of pressure conversion device, 87—cable conduit, 88—check valve and sealing nut connecting screw, 89—grouting channel. DETAILED DESCRIPTION

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0070] like Figure 1 As shown, an embodiment of the present invention provides a ground stress testing device based on distributed double-sided pressure hydraulic pillow monitoring. At least three boreholes 2 with different inclinations and azimuths are provided on the side wall or face of the tunnel 1. The three boreholes in this embodiment are named ZK1, ZK2 and ZK3, respectively, for burying double-sided pressure hydraulic pillows 8. The axial angles of each borehole 2 should intersect at a large angle, and preferably be arranged perpendicular to each other. At least three double-sided pressure hydraulic pillows 8 with different installation angles are buried in each borehole 2, preferably arranged at an angle of 60°. Each borehole 2 in this embodiment can obtain two-dimensional stress data of a borehole cross section, and the entire implementation plan is an embodiment of a three-dimensional ground stress acquisition plan. The double-sided pressure hydraulic pillow 8 is communicatively connected to the data acquisition instrument at the orifice, and the data acquisition instrument is communicatively connected to the data processing device.

[0071] like Figure 2 As shown in Figures (a) and (b), this embodiment provides a double-sided pressure-bearing hydraulic pillow (i.e., double-sided pressure-bearing hydraulic pillow 8). Both sides of the double-sided pressure-bearing hydraulic pillow 8 are capable of pressure-bearing deformation, with cable conduits and grouting pipes located on either side. The double-sided pressure-bearing hydraulic pillow 8 includes a main body 81, a pressure-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 one-way valve and sealing nut connecting screw 88, and a grouting channel 89.

[0072] The main body 81 is a square frame structure made of metal. The pressure plates 82, which can be made of paper steel plates of varying thicknesses, cover both sides of the main body 81. The main body 81 and pressure plates 82 of the double-sided pressure-bearing hydraulic pillow can be fabricated using single-sided welding or integral 3D printing. The pressure-bearing liquid 83 is located within the main body 81.

[0073] Please also refer to Figure 1 、 Figure 2 and Figure 4 The cable conduit 87 and the grouting channel 89 are fixed to the side of the main body 81.

[0074] The pressure conversion device connection port 86 is used to install the pressure conversion device 7. The pressure of the pressure-bearing liquid 83 of the double-sided pressure hydraulic pillow 8 is sensed by the pressure conversion device 7. The relevant information is connected to the data acquisition instrument at the port via the cable 5. The cable 5 should be placed in the cable conduit 87 when passing through other double-sided pressure hydraulic pillows. The data acquisition instrument transmits the pressure data to the data processing device to calculate the ground stress in different dimensions.

[0075] The one-way valve and sealing nut connecting screw 88 is used to connect the one-way valve and sealing nut 6, and the one-way valve and sealing nut 6 is used to inject pressurized liquid 83 into the main body 81 of the double-sided pressure hydraulic pillow 8. The pressurized liquid 83 is hydraulic oil, water or a mixture of hydraulic oil and water.

[0076] The grouting channel 89 of the double-sided pressure hydraulic pillow 8 is connected to the grouting pipe 3 to the outside of the hole. The double-sided pressure hydraulic pillow 8 is buried in the borehole 2 by grouting, and the space between the borehole 2 and the double-sided pressure hydraulic pillow 8 is filled with cement stone 9. The cement stone 9 is used to couple the stress field of the rock mass and the double-sided pressure hydraulic pillow 8.

[0077] The mounting rod 4 is formed by connecting rods of equal length and adopts a threaded connection form. The specifications of the connecting threads are consistent with the upper connecting threads 85 and the lower connecting threads 84 of the double-sided pressure hydraulic pillow 8.

[0078] The embodiment of the present invention further provides a method for testing ground stress based on distributed double-sided pressure hydraulic pillow monitoring, which is performed using the above-mentioned equipment. The method includes the following steps:

[0079] Step 1. Determine the test plan based on the distributed double-sided pressure hydraulic pillow: determine the number of drill holes and the drilling arrangement plan, the double-sided pressure hydraulic pillow arrangement plan and the number. The test requirements can be met through the combination of hydraulic pillows and drilling arrangements, and the measurement of 1D to 3D ground stress information can be realized.

[0080] The double-sided pressure hydraulic pillow combination refers to the combination of double-sided pressure hydraulic pillows according to the measurement requirements, which can be used to measure the unidirectional stress in any radial direction of the borehole or the plane stress of the borehole cross section. Figure 4 As shown in the figure, unidirectional stress measurement can be performed; a single borehole uses three or more double-sided pressure hydraulic pillows with different installation angles (for example Figure 1 The three double-sided pressure hydraulic pillows shown in the figure can be used to measure the plane stress of the borehole cross section.

[0081] The drilling arrangement refers to arranging multiple test boreholes on the tunnel wall or face according to the test requirements, which are numbered i; installing three or more double-sided pressure hydraulic pillows (numbered j) with different installation angles in a single test borehole, and obtaining multiple unidirectional compressive stresses or plane stresses in the borehole cross section. The plane stresses obtained by drilling more than three holes in different directions can be combined to calculate the spatial three-dimensional stress.

[0082] Step 2: Preparation and calibration test of double-sided pressure hydraulic pillow, including the following steps:

[0083] (1) Air tightness test of double-sided pressure hydraulic pillow 8: After the double-sided pressure hydraulic pillow is processed, the one-way valve and sealing nut 6 are connected to the double-sided pressure hydraulic pillow body 81 through the one-way valve and sealing nut connecting screws 88, and the other end is connected to the oil pump. The pressurized liquid 83 is injected into the double-sided pressure hydraulic pillow 8 through the one-way valve. During the injection process, the air must be completely exhausted through the pressure conversion device connection port 86. Then the pressure conversion device 7 is connected to pre-pressurize the double-sided pressure hydraulic pillow 8 and maintain the pressure for a long time to test the air tightness of the hydraulic pillow.

[0084] (2) Pressure calibration test: Under the rock mass stress state of the press or simulated field test conditions, the double-sided pressure hydraulic pillow 8 is calibrated to obtain the relationship between the test load and output pressure under a specific preload pressure, that is, Figure 3 The fitting coefficient a in the relationship j and b j ;

[0085] Step 3: Hydraulic pillow installation and data observation, including the following steps:

[0086] (1) Drilling preparation: Drilling is carried out according to the drilling arrangement plan to ensure that the hole diameter is suitable and the holes are drilled according to the predetermined plan;

[0087] (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 (α j );

[0088] (3) Grouting backfill: Grouting backfill is performed on the borehole to integrate the observation device with the rock mass. The physical parameters of the grout material should be as consistent as possible with the rock mass parameters.

[0089] (4) Stress observation: Continuously observe the pressure changes of each double-sided pressure pillow 8 and record the pressure change data over time;

[0090] Step 4: Stress calculation, including the following steps:

[0091] (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 pressure hydraulic pillow nj ;

[0092] (2) Combine the measurement results of the double-sided pressure hydraulic pillow and calculate the ground stress in different dimensions according to the test arrangement.

[0093] Generally speaking, the cavern has a disturbing effect on the initial stress field of the nearby rock mass, and the buried measurement device has an "embedding 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 shown i y i , axis x i 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 (1), Figure 4 The plane stress measurement results of the drilled hole cross section are shown as formula (2).

[0094] σnj=a j ·p j +b j (1)

[0095]

[0096] Where, σ n1 , σ n2 , and σ n3 is the unidirectional compressive stress in the normal direction of three double-sided hydraulic pillows in a borehole, σ1 is the major principal stress of the borehole cross section, σ2 is the minor principal stress of the borehole cross section, and angle ɑ is the maximum principal stress direction angle, which is the angle with axis x. i The angle of the starting counterclockwise rotation to the direction of maximum principal stress.

[0097] Three-dimensional stress calculation requires the establishment of Figure 5 The geodetic coordinate system o-xyz and the borehole coordinate system o i -x i y i z i , where the relationship between the pressure surface of the j-th double-sided pressure hydraulic pillow and the earth and borehole coordinate system is shown in the figure. The observation value equation of a single double-sided pressure hydraulic pillow is shown in formula (3). x , σ y , σ z , τxy , τ yz and τ zx is the spatial stress component in the coordinate system O-xyz; A k1 ~A k6 is the stress coefficient, and its value is shown in formula (4), where α j is the inclination angle of the j-th double-sided pressure hydraulic pillow (or buried borehole), β0 is the x-axis orientation of the coordinate system O-xyz, β i Axial orientation of the borehole for burying the equipment;

[0098] 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)

[0099] A k1 ~A k6 The value of is shown in formula (4);

[0100]

[0101] Where σ nj is the normal stress of the double-sided hydraulic pillow with serial number j, α j is the installation angle of the double-sided pressure hydraulic pillow, β i is the direction of the double-sided hydraulic pillow plane; suppose there are a double-sided hydraulic pillows, solve the optimal value of stress component σ x , σ y ,…τ zx The normal equations of are shown in formula (5):

[0102]

[0103] Where σ* is the observed value, which is the left-hand term of equation (3). After the optimal stress component value is solved, further calculations can be performed on the observed value residuals and standard errors, as well as the magnitude and direction of the three-dimensional principal stresses. This description will not be repeated in this invention.

[0104] The main innovations and beneficial effects of the present invention are as follows:

[0105] ①The double-sided pressure hydraulic pillow has the same force measurement principle as the combined unidirectional hydraulic pillow and can bear pressure on both sides. It is a new design of the unidirectional combined hydraulic pillow structure.

[0106] ② Double-sided hydraulic pillows bear pressure on both sides, which can improve the monitoring effect better than single-sided hydraulic pillows;

[0107] ③ The double-sided pressure hydraulic pillow has a larger pressure-bearing area under the condition of the same diameter drilling, which can fully couple with the rock mass to achieve more ideal experimental results.

[0108] ④ The distributed double-sided pressure hydraulic pillow is flexible in layout and can obtain 1D to 3D ground stress data, meeting the ground stress data requirements of survey and design;

[0109] ⑤ Improve the ground stress testing technology of weak rock masses.

[0110] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A ground stress testing device based on distributed double-sided pressure hydraulic pillow monitoring, characterized in that: include: Double-sided pressure hydraulic pillows are buried in drilled holes on the side walls or face of the tunnel, with at least three double-sided pressure hydraulic pillows at different installation angles buried in each drilled hole. The double-sided pressure hydraulic pillows include a main body, a pressure-bearing plate, a pressure-bearing liquid, a pressure conversion device connection port, a one-way valve, and sealing nut connection screws. The main body is a square frame structure, with the pressure-bearing plates covering both sides of the main body, and the pressure-bearing liquid located inside the main body. A mounting rod detachably connected to both ends of the main body; The one-way valve and the sealing nut are connected to the one-way valve and the sealing nut connecting screws, and are used to inject the pressurized liquid into the main body of the double-sided pressure hydraulic pillow; The double-sided pressure hydraulic pillow is buried in the borehole by grouting, and the space between the borehole and the double-sided pressure hydraulic pillow is filled with cement and stone to couple the stress fields of the rock mass and the double-sided pressure hydraulic pillow. A pressure conversion device, installed at the connection port of the pressure conversion device, for sensing the pressure of the pressurized liquid; an electric cable, communicatively connected to the pressure conversion device, for transmitting the sensed pressure data to a data acquisition instrument at the orifice; The data processing device is used to draw the pressure change curve of the double-sided hydraulic pillow over time based on the pressure data transmitted by the data acquisition instrument, and 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 pressure hydraulic pillow nj ; Combine the measurement results of the double-sided pressure hydraulic pillow and calculate the ground stress in different dimensions according to the test arrangement.

2. The ground stress testing equipment based on distributed double-sided pressure hydraulic pillow monitoring according to claim 1 is characterized in that: The main body is made of metal material, and the pressure plate is a paper steel plate.

3. The ground stress testing equipment based on distributed double-sided pressure 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 ground stress testing equipment based on distributed double-sided pressure hydraulic pillow monitoring according to claim 1 is characterized in that: The double-sided pressure hydraulic pillow also includes a lower connecting thread and an upper connecting thread provided at both ends of the main body. 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 pressure-bearing liquid as claimed in claim 1 is hydraulic oil, water or a mixture of hydraulic oil and water.

6. The ground stress testing equipment based on distributed double-sided pressure hydraulic pillow monitoring according to claim 1, characterized in that: The data processing device is specifically used for: The unidirectional compressive stress σ obtained by calculating a single double-sided pressure hydraulic pillow combination according to formula (1) is: nj ; The plane stress measurement result of the drilled cross section is (2): σnj=a j ·p j +b j (1) Where: σ n1 , σ n2 , and σ n3 is the unidirectional compressive stress in the normal direction of three double-sided hydraulic pillows in a borehole, σ1 is the major principal stress of the borehole cross section, σ2 is the minor principal stress of the borehole cross section, and angle ɑ is the maximum principal stress direction angle, which is the angle with axis x. i The angle from the start to the maximum principal stress direction is counterclockwise, σ nj is the unidirectional compressive stress of the double-sided hydraulic pillow with serial number j; When calculating three-dimensional stress, the geodetic coordinate system o-xyz and the drilling coordinate system o are established. i -x i y i z i , the observation value equation of a single double-sided pressure hydraulic pillow is shown in formula (3): s nj =A k1 s x +A k2 s y +A k3 s z +A k4 t xy +A k5 t yz +A k6 t zx (3) Where σ x , σ y , σ z , τ xy , τ yz and τ zx is the spatial stress component in the coordinate system O-xyz; A k1 ~A k6 is the stress coefficient, and its value is shown in formula (4), where α j is the inclination angle of the j-th double-sided hydraulic pillow, β0 is the x-axis orientation of the coordinate system O-xyz, β i Axial orientation of the borehole for burying the equipment; Where, α j is the installation angle of the double-sided pressure hydraulic pillow, β i is the direction of the double-sided hydraulic pillow plane; suppose there are a double-sided hydraulic pillows, solve the optimal value of stress component σ x ,σ y ,…τ zx The normal equations of are shown in formula (5): Where σ* is the observed value, which is the left side term of formula (3).

7. A ground stress testing method based on distributed double-sided pressure hydraulic pillow monitoring, characterized in that: The method is carried out using the device according to any one of claims 1 to 6, and comprises the following steps: Step 1: Determine the test plan based on the distributed double-sided pressure hydraulic pillow: determine the number of drill holes and the drilling arrangement, the arrangement and number of double-sided pressure hydraulic pillows, and achieve the test requirements through the combination of hydraulic pillows and drilling arrangement to realize the measurement of 1D to 3D ground stress information; Step 2: Preparation and calibration test of double-sided pressure hydraulic pillow, including the following steps: (1) Air tightness test of double-sided pressure hydraulic pillow: After the double-sided pressure hydraulic pillow is processed, connect the one-way valve and sealing nut to the double-sided pressure hydraulic pillow body through the one-way valve and sealing nut connecting screws, connect the other end to the oil pump, and inject pressurized liquid into the double-sided pressure hydraulic pillow through the one-way valve. During the injection process, the air must be completely exhausted through the connection port of the pressure conversion device. Then connect the pressure conversion device, pre-pressurize the double-sided pressure hydraulic pillow and maintain the pressure for a long time to test the air tightness of the hydraulic pillow; (2) Pressure calibration test: Under the rock mass stress state of the press or simulated field test conditions, the double-sided pressure hydraulic pillow is calibrated to obtain the relationship between the test load and output pressure under a specific preload pressure, and the fitting coefficient a in the relationship between the test load and output pressure is obtained. j and b j ; Step 3: Hydraulic pillow installation and data observation, including the following steps: (1) Drilling preparation: Drilling is carried out according to the drilling arrangement plan to ensure that the hole diameter is suitable and the holes are drilled according to the predetermined plan; (2) Installation: Install multiple calibrated and numbered double-sided pressure hydraulic pillows in the drilled holes, and record the installation depth and angle data of the double-sided pressure hydraulic pillows; (3) Grouting backfill: Grouting backfill is performed on the borehole to integrate the observation device with the rock mass. The physical parameters of the grout material should be as consistent as possible with the rock mass parameters. (4) Stress observation: Continuously observe the pressure changes of each double-sided pressure pillow and record the pressure change data over time; Step 4: Stress calculation, including the following steps: (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 pressure hydraulic pillow nj ; (2) Combine the measurement results of the double-sided pressure hydraulic pillow and calculate the ground stress in different dimensions according to the test arrangement.

8. The ground stress testing method based on distributed double-sided pressure hydraulic pillow monitoring according to claim 7 is characterized in that: Step 4 specifically includes: The unidirectional compressive stress σ obtained by a single double-sided hydraulic pillow combination nj is (1), and the plane stress measurement result of the drilled cross section is (2), σnj=a j ·p j +b j (1) Where σ n1 , σ n2 , and σ n3 is the unidirectional compressive stress in the normal direction of three double-sided hydraulic pillows in a borehole, σ1 is the major principal stress of the borehole cross section, σ2 is the minor principal stress of the borehole cross section, and angle ɑ is the maximum principal stress direction angle, which is the angle with axis x. i The angle from the start to the maximum principal stress direction is counterclockwise, σ nj is the unidirectional compressive stress of the double-sided hydraulic pillow with serial number j; When calculating three-dimensional stress, the geodetic coordinate system o-xyz and the drilling coordinate system o are established. i -x i y i z i , the observation value equation of a single double-sided pressure hydraulic pillow is shown in formula (3): s nj =A k1 s x +A k2 s y +A k3 s z +A k4 t xy +A k5 t yz +A k6 t zx (3) Where σ x , σ y , σ z , τ xy , τ yz and τ zx is the spatial stress component in the coordinate system O-xyz; A k1 ~A k6 is the stress coefficient, and its value is shown in formula (4), where α j is the inclination angle of the j-th double-sided hydraulic pillow, β0 is the x-axis orientation of the coordinate system O-xyz, β i Axial orientation of the borehole for burying the equipment; Where, α j is the installation angle of the double-sided pressure hydraulic pillow, β i is the direction of the double-sided hydraulic pillow plane; suppose there are a double-sided hydraulic pillows, solve the optimal value of stress component σ x ,σ y ,…τ zx The normal equations of are shown in formula (5): Where σ* is the observed value, which is the left side term of formula (3).

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