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

Abstract

The invention provides ground stress testing equipment and method based on distributed double-sided compression hydraulic pillow monitoring. The equipment comprises double-sided compression hydraulic pillows and drill holes buried in the side wall or the tunnel face of a tunnel, and at least three double-sided compression hydraulic pillows with different installation angles are buried in each drill hole; the double-face pressed hydraulic pillow comprises a main body, a pressure bearing plate, pressure bearing liquid, a pressure conversion device connector, a one-way valve and a sealing nut connecting screw. The one-way valve and the sealing nut are used for injecting pressure-bearing liquid into the main body of the double-sided pressed hydraulic pillow; the pressure conversion device is mounted at the pressure conversion device connector and is used for sensing the pressure of the pressure-bearing liquid; the cable is in communication connection with the pressure conversion device and is used for transmitting the sensed pressure data to a data acquisition instrument at the orifice; and the data processing device is used for calculating crustal stress of different dimensions according to the pressure data. The device can solve the problem that the testing result is insufficient in representativeness due to the fact that the grouting quality is influenced by the combination of the one-way hydraulic pillows.

Description

Technical Field

[0001] The 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] Geostress is one of the controlling factors of deformation and damage of surrounding rock in underground projects. Under high to extremely high geostress conditions, hard and brittle rock mass is prone to rock bursts, and weak rock mass is prone to large deformation and damage. With the advancement of long-distance water diversion projects, transportation projects and deep mining projects in my country, large deformation of surrounding rock in weak rock mass and TBM tunneling machine jam accidents frequently occur. The acquisition of geostress data of typical weak rock mass such as fault zones has become an engineering problem that needs to be solved urgently.

[0003] At present, there are three-way pressure box, hydraulic drilling stress meter and combined unidirectional hydraulic pillow for measuring in-situ stress of soft rock mass. Among them, the combined unidirectional hydraulic pillow directly measures the unidirectional compressive stress of soft rock mass and combines and calculates the two-dimensional stress. The actual application shows that the combination of the planes of the combined unidirectional hydraulic pillow is easy to affect the grouting backfill effect, and then affect the stress coupling and test effect of the rock mass and hydraulic pillow. Summary of the invention

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

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

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

[0007] A double-sided pressure hydraulic pillow is buried in a borehole on the side wall or face of a tunnel, and at least three double-sided pressure hydraulic pillows with different installation angles are 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;

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

[0009] A one-way valve and a sealing nut, connected to the one-way valve and the sealing nut connecting screws, are used to inject 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 field 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 with time according to 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 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 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.

[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) nj ;

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

[0021] σnj=a j ·p j+b j (1)

[0022]

[0023] In the formula, σ n1 , σ n2 , and σ n3 is the uniaxial compressive stress in the normal direction of the 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 in counterclockwise rotation, 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 i -x i y i z i , the observed 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] In the formula, 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 jth 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] In the formula, 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] In the formula, σ* is the observed value, which is the left 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 comprises 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 plan, the double-sided pressure hydraulic pillow arrangement plan and number, meet the test requirements through the combination of hydraulic pillows and drilling arrangements, and 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, the one-way valve and the sealing nut are connected to the double-sided pressure hydraulic pillow body through the one-way valve and the sealing nut connecting screws, and the other end is connected to the oil pump. The pressurized liquid is injected 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 the pressure conversion device is connected, and the double-sided pressure hydraulic pillow is pre-pressurized and the pressure is maintained for a long time to test the air tightness of the hydraulic pillow;

[0035] (2) Pressure calibration test: Under the rock 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 the output pressure under a specific preload pressure, and the fitting coefficient a in the relationship between the test load and the 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 construction is carried out according to the drilling arrangement plan to ensure that the hole diameter is suitable and the drilling is carried out 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 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;

[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 hydraulic pillow nj ;

[0043] (2) Combine the measurement results of the double-sided 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] In the formula, σ n1 , σ n2 , and σ n3 is the uniaxial compressive stress in the normal direction of the 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, 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 i -x i y i z i , the observed 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] In the formula, 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 jth double-sided hydraulic pillow, β0 is the x-axis orientation of the coordinate system O-xyz, β i The axial orientation of the hole for burying the equipment;

[0052]

[0053] In the formula, 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] In the formula, σ* is the observed value, which is the left 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 arranged reasonably to realize the double-sided pressure of the hydraulic pillow and to be spread along the axis of the borehole. The double-sided pressure hydraulic pillow has the same force measurement principle as the combined unidirectional hydraulic pillow and can be pressurized on both sides. Under the same hydraulic pillow size and the same pressure conditions, it has a larger force bearing area than the unidirectional hydraulic pillow, can be fully coupled with the rock mass, and can produce 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 spread along the borehole axis. The hydraulic pillows are dispersed. During grouting, both sides are bathed in slurry. After stone formation, both sides can bear 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, which 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 flexibly arranged and can obtain 1D to 3D ground stress data. The present invention specifically provides a calculation method for three-dimensional stress measurement of distributed hydraulic pillows, which can fully meet the needs of survey and design for ground stress data;

[0061] ⑤ The present invention aims at the shortcoming that the combined one-way hydraulic pillow measurement technology easily leads to incomplete grouting. Through technical innovation, the stress coupling effect between the rock stress field and the hydraulic pillow is effectively improved, so that the hydraulic pillow produces a more sensitive pressure response and reduces the measurement error. There is no reliable ground stress detection technology for weak rock mass, and this technology can effectively improve its detection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It 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 in an embodiment of the present invention, (b) is a top view of a double-sided pressure hydraulic pillow in an embodiment of the present invention, and (c) is a left view of a double-sided pressure hydraulic pillow in 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 single double-sided pressure hydraulic pillow is buried in the embodiment of the present invention i y i Schematic diagram;

[0066] Figure 5 The single double-sided pressure hydraulic pillow and the drilling coordinate system ox in the embodiment of the present invention 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—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—pressure plate, 83—pressure liquid, 84—lower connecting thread, 85—upper connecting thread, 86—connecting port of pressure conversion device, 87—cable pipe, 88—check valve and sealing nut connecting screws, 89—grouting channel. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 here 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 the face of the tunnel 1. The three boreholes in this embodiment are named ZK1, ZK2 and ZK3, respectively, for burying the 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 implementation plan 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 (a) and (b), this embodiment provides a double-sided pressure hydraulic pillow (i.e., double-sided pressure hydraulic pillow 8), both sides of which are capable of pressure-bearing deformation, and the cable conduit and the grouting pipe are arranged on both sides. The double-sided pressure 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 a 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 plate 82 can be a paper steel plate of different thicknesses, covering both sides of the main body 81. The main body 81 and the pressure plate 82 of the double-sided pressure hydraulic pillow can be processed by single-sided welding or integral 3D printing; the pressure-bearing liquid 83 is located inside the main body 81.

[0073] Please also read 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 orifice by the cable 5, wherein the cable 5 should be placed in the cable tube 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 mouth. The double-sided pressure hydraulic pillow 8 is buried in the borehole 2 by grouting. The space between the borehole 2 and the double-sided pressure hydraulic pillow 8 is filled with cement stones 9. The cement stones 9 are used to couple the stress fields 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 is threadedly connected. 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 device. The method comprises 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 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 selected to measure the unidirectional stress in any radial direction of the borehole or the plane stress in the cross section of the borehole. Figure 4 As shown in the figure, unidirectional stress measurement can be performed; a single borehole uses three or more double-sided hydraulic pillows with different installation angles (for example Figure 1 The three double-sided pressure hydraulic pillow combination 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 cave wall or the face according to the test requirements, which are numbered i; installing 3 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 cross section of the borehole. The plane stresses obtained by drilling holes in more than 3 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 the double-sided pressure hydraulic pillow 8: After the double-sided pressure hydraulic pillow is processed, the one-way valve and the sealing nut 6 are connected to the double-sided pressure hydraulic pillow body 81 through the one-way valve and the 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 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 the 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 construction is carried out according to the drilling arrangement plan to ensure that the hole diameter is suitable and the drilling is carried out 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 of the double-sided hydraulic pillows (α j );

[0088] (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;

[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 hydraulic pillow nj ;

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

[0093] 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).

[0094] σnj=a j ·p j +b j (1)

[0095]

[0096] In the formula, σ n1 , σ n2 , and σ n3 is the uniaxial compressive stress in the normal direction of the 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 starting from 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 jth double-sided pressure hydraulic pillow (or buried borehole), β0 is the x-axis orientation of the coordinate system O-xyz, β i The axial orientation of the hole 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] In the formula, 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] Wherein, σ* is the observed value, which is the left term of formula (3). After the optimal value of the stress component is solved, the residual and standard error of the observed value, the value of the three-dimensional principal stress and its direction can be further calculated, which will not be described in detail in the present invention.

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

[0105] ① 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. 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-bearing hydraulic pillow has a larger pressure-bearing area under the same diameter drilling conditions, which can be fully coupled with the rock mass to achieve more ideal experimental results.

[0108] ④ The distributed double-sided pressure hydraulic pillow is flexibly arranged and can obtain 1D to 3D ground stress data to meet the needs of survey and design for ground stress data;

[0109] ⑤ Improve the geostress testing technology of soft rock masses.

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

Claims

1. A ground stress testing device based on distributed double-sided pressure hydraulic pillow monitoring, characterized in that: include: A double-sided pressure hydraulic pillow is buried in a borehole on the side wall or face of a tunnel, and at least three double-sided pressure hydraulic pillows with different installation angles are 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; A mounting rod detachably connected to both ends of the main body; A one-way valve and a sealing nut, connected to the one-way valve and the sealing nut connecting screws, are used to inject 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 field 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 with time according to 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 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-bearing 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 as claimed in claim 1 is 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 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 as claimed in claim 1 is 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) nj ; The plane stress measurement result of the drilled cross section is (2): σnj=a j ·p j +b j (1) Where: n1 , σ n2 , and σ n3 is the uniaxial compressive stress in the normal direction of the 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 in counterclockwise rotation, 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 i -x i y i z i , the observed 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) In the formula, 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 jth double-sided hydraulic pillow, β0 is the x-axis orientation of the coordinate system O-xyz, β i The axial orientation of the hole for burying the equipment; In the formula, 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): In the formula, σ* is the observed value, which is the left term of formula (3).

7. A method for testing ground stress 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 plan, the double-sided pressure hydraulic pillow arrangement plan and number, meet the test requirements through the combination of hydraulic pillows and drilling arrangements, and 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, the one-way valve and the sealing nut are connected to the double-sided pressure hydraulic pillow body through the one-way valve and the sealing nut connecting screws, and the other end is connected to the oil pump. The pressurized liquid is injected 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 the pressure conversion device is connected, and the double-sided pressure hydraulic pillow is pre-pressurized and the pressure is maintained for a long time to test the air tightness of the hydraulic pillow; (2) Pressure calibration test: Under the rock 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 the output pressure under a specific preload pressure, and the fitting coefficient a in the relationship between the test load and the output pressure is obtained. j and b j ; Step 3: Hydraulic pillow installation and data observation, including the following steps: (1) Drilling preparation: Drilling construction is carried out according to the drilling arrangement plan to ensure that the hole diameter is suitable and the drilling is carried out 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 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; (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 hydraulic pillow nj ; (2) Combine the measurement results of the double-sided hydraulic pillow and calculate the ground stress in different dimensions according to the test arrangement.

8. The method for testing ground stress based on distributed double-sided pressure hydraulic pillow monitoring as claimed in claim 7, 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) In the formula, σ n1 , σ n2 , and σ n3 is the uniaxial compressive stress in the normal direction of the 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, 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 i -x i y i z i , the observed 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) In the formula, 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 jth double-sided hydraulic pillow, β0 is the x-axis orientation of the coordinate system O-xyz, β i The axial orientation of the hole for burying the equipment; In the formula, 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): In the formula, σ* is the observed value, which is the left term of formula (3).

Images