A rock mass ground stress three-dimensional measuring device

Abstract

The application discloses a kind of rock mass ground stress three-dimensional measuring devices, it includes spherical shell (1), ground stress measuring unit (2) is arranged inside spherical shell (1), ground stress measuring unit (2) includes the ball internal strain layer (21) for measuring the stress in one pressure direction and the cross member (22) for measuring other two stresses on normal plane, cross member (22) end is the rolling conductive structure (23) in contact with the inner wall of spherical shell (1), cross member (22) center intersection position is equipped with data acquisition transmission unit (3) for recording ground stress measurement value.The technical effect of the application is: can measure three-dimensional stress in rock mass space, directly reflect original ground stress in rock mass.

Description

Technical Field

[0001] This invention belongs to the field of geostress measurement technology, specifically relating to a three-dimensional geostress measurement device for rock mass, which achieves three-dimensional geostress measurement of rock mass through the deformation of a spherical shell and the assistance of a positioning spring. Background Technology

[0002] Rock masses, as natural geological formations, play a vital role in human economic and social development and engineering construction. Due to factors such as crustal movement, rock masses contain complex initial geostresses, and understanding the magnitude and direction of these stresses is extremely important for engineering construction activities.

[0003] Whether using direct or indirect methods to measure in-situ stress, current in-situ stress measurement equipment is mostly designed for one or two directions at the point being measured, while equipment for measuring in-situ stress in all three directions at a single point is rare. For example, the indirect method—the stress relief method—is widely used both domestically and internationally for single-point in-situ stress measurement. This method can achieve three-dimensional in-situ stress measurement of rock mass through a single borehole at a single point. Although it has high accuracy, this method also has some shortcomings:

[0004] The quality requirements for the rock mass at the measurement point are high. When the rock mass is broken or the core is shredded, it is difficult to install sensors or remove intact cores. At the same time, it is necessary to extract the core for indoor testing to measure parameters such as elastic modulus and Poisson's ratio. However, the mechanical parameters measured indoors are not completely equivalent to the in-situ parameters in actual engineering. Summary of the Invention

[0005] In view of the problems existing in the prior art, the technical problem to be solved by the present invention is to provide a three-dimensional rock mass stress measurement device, which can measure the three-dimensional stress in the rock mass space and directly reflect the original stress in the rock mass.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solution, which includes a spherical shell, a ground stress measurement unit, and a data acquisition and transmission unit. The ground stress measurement unit is arranged inside the spherical shell. The ground stress measurement unit includes an inner strain layer for measuring the stress in one compressive direction and a cross-shaped component for measuring two other stresses on a plane with the compressive direction as the normal. The ends of the cross-shaped component are rolling conductive structures that contact the inner wall of the spherical shell. A data acquisition and transmission unit for recording the ground stress measurement values ​​is provided at the central intersection position of the cross-shaped component.

[0007] Preferably, the spherical shell includes an upper hemisphere and a lower hemisphere, the two hemispheres are connected by a pre-set interface thread on the hemisphere interface, and the inner layer of the spherical shell is attached with an inner strain layer.

[0008] Preferably, the cross-shaped component is a cross-shaped rigid structure, including a positioning tube, a strain spring and a guide rod. The positioning tube is disconnected in the middle and then connected by the strain spring. The two ends of the strain spring are inserted into the two sections of the positioning tube by spring fixing rings. The guide rod passes through the inner ring of the strain spring. The positioning tube is sleeved around the extension section of the guide rod and the strain transmission wire passes through the inner hole.

[0009] Compared with the prior art, the advantages of the present invention are:

[0010] 1. The measuring device is spherical in shape, so the data will not be affected by the anisotropy of the shape during stress measurement;

[0011] 2. This measuring device can measure three-dimensional stress in the rock mass space;

[0012] 3. Because this measuring device uses a cross-shaped component combining a guide tube and a strain spring, it can measure both compressive and tensile stress. Attached Figure Description

[0013] The accompanying drawings of this invention are described below:

[0014] Figure 1 This is a schematic diagram of the structure of the present invention;

[0015] Figure 2 This is a schematic diagram of the hemispherical interface.

[0016] Figure 3 A schematic diagram of a strain measurement structure for a rigid "cross" component;

[0017] Figure 4 This is an enlarged view of the rolling conductive structure;

[0018] Figure 5 This is a graph showing the relationship between radial stress and shell thickness on the outer shell of a sphere.

[0019] Figure 6 This is a graph showing the relationship between the circumferential stress and the thickness of the spherical shell.

[0020] Figure 7 A simulation diagram showing the deformation characteristics of a spherical shell with a radius of 4.

[0021] Figure 8 A simulation diagram showing the deformation characteristics of a spherical shell under load.

[0022] Figure 9 This is a simulation diagram of the deformation characteristics of the thickness of the spherical shell.

[0023] In the diagram, 1. Sphere shell, 11. Upper hemisphere, 12. Lower hemisphere, 13. Hemisphere interface, 14. Interface thread; 2. Ground stress measurement unit, 21. Inner strain layer, 22. Cross-shaped component; 221. Positioning tube, 222. Strain spring, 223. Guide rod; 23. Rolling conductive structure, 231. Hemisphere shell constraint, 232. Metal sphere, 233. Conductive tray; 26. Strain transmission wire, 27. Spring fixing ring; 3. Data acquisition and transmission unit. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0025] To clearly describe the invention, this patent application uses the directional terms "upper" and "lower" for distinction. The terms "upper" and "lower" are determined based on the arrangement of the above figures. When the actual use direction of the invention changes, the terminology of the orientation will change accordingly, and this should not be regarded as a limitation on the scope of patent protection.

[0026] like Figure 1 As shown, the present invention includes a spherical shell 1, a geostress measurement unit 2, and a data acquisition and transmission unit 3. The spherical shell 1 is a rock mass geostress bearing device. The geostress measurement unit 2 is installed inside the spherical shell 1. The geostress measurement unit 2 includes an inner strain layer 21 for measuring stress in a certain compressive direction and a cross-shaped component 22 for measuring two other stresses on a plane with the compressive direction as the normal. The ends of the cross-shaped component 22 are rolling conductive structures 23 that contact the inner wall of the spherical shell 1. The data acquisition and transmission unit 3 is located at the center intersection of the cross-shaped component 22 for recording the geostress measurement values. The data acquisition and transmission unit 3 is used to record the strain data collected during the rock mass stress measurement, obtain the corresponding stress data through calculation (see the literature "Wireless Transmission Technology of Penetration Data in Deep Buried Environment", He Bo, North University of China, 2020), and transmit the data to an external receiver.

[0027] like Figure 2 As shown, the spherical shell 1 consists of an upper hemisphere 11 and a lower hemisphere 12. The two hemispheres are connected by a pre-set interface thread 14 on the hemispherical interface 13. An inner strain layer 21 is attached to the inner layer of the spherical shell. The spherical shell 1 is a thin-shell structure made of steel. The function of the spherical shell is to deform under the action of ground stress. The inner strain layer 21 transmits the measured strain data to the data acquisition and transmission unit 3 through the conductive metal ball 233 and the strain transmission wire 26.

[0028] The stress in a certain compressive direction is related to the deformation of the spherical shell, and the stress is determined by the strain layer inside the spherical shell. As an example of simulation analysis, the strain layer 21 inside the spherical shell is made of nickel-chromium alloy and completely covers the inner layer of the spherical shell. The signal of the strain layer 21 inside the spherical shell is a single output.

[0029] like Figure 1 and Figure 3 As shown, the cross-shaped component 22 is a rigid cross-shaped structure, including a positioning tube 221, a strain spring 222, and a guide rod 223. The positioning tube 221 is broken in the middle and connected by the strain spring 222. The two ends of the strain spring 222 are inserted into the two sections of the positioning tube 221 through spring fixing rings 27. Specifically, one end of the large end face of the spring fixing ring 27 is welded to the strain spring 222, and the other end is inserted into the positioning tube 221 and connected with a pin. The guide rod 223 passes through the inner ring of the strain spring 222. The positioning tube 221 is sleeved around the extension of the guide rod 223, and the strain transmission wire 26 passes through the inner hole of the guide rod 223.

[0030] The positioning tube 221 is a sleeve that can extend and retract with the deformation of the strain spring 222. The guide rod 223 serves to maintain the strain guidance of the strain spring, preventing it from deviating from the straight line, and to protect the strain transmission wire. The strain transmission wire 26 is a parallel data transmission line. A strain wire (not shown in the figure) is provided parallel to the strain spring 222. The strain wire can convert the deformation of the strain spring into a change in resistance.

[0031] like Figure 1 and Figure 4 As shown, the rolling conductive structure 23 includes a hemispherical shell constraint 231, a metal ball 232, and a conductive tray 233. The hemispherical shell constraint 231 is an incomplete spherical shell containing the metal ball 232. Its function is to constrain the metal ball to roll tightly against the strain layer 21 inside the sphere when the spherical shell is subjected to force. The conductive tray 233 is a concave disc-shaped metal sheet. Its front side abuts against the metal ball 232 as it rolls inside the spherical shell, and its back side is connected to the strain transmission wire 26. Under the frame of the conductive tray 233, the metal ball 232 can achieve both the rolling positioning of the cross-shaped component 22 and the connection of data transmission of the strain layer 21 inside the sphere. The hemispherical shell constraint 231 is connected to the end of the positioning tube 221, and the end of the guide rod 223 is connected to the metal tray 233.

[0032] The two ends of the cross-shaped component 22 are in contact with the spherical shell through metal balls. It remains stable when not under stress. When the spherical shell is subjected to stress, the metal balls at both ends of the cross-shaped component roll and drive the cross-shaped component, causing it to stop at a position perpendicular to the direction of pressure. The data acquisition and transmission unit 3 can be fixed to the center intersection of the cross-shaped components 22 using screws.

[0033] Utilizing the deformation of the spherical shell 1 under stress, and with the rolling of the metal ball 232 and the extension of the strain spring 222, the cross-shaped component 22 moves towards a plane perpendicular to the direction of the force on the spherical shell, thus indirectly forming a three-dimensional spatial coordinate system. The strain obtained by the strain transmission wire 26 through the metal ball 232 is the strain of the spherical shell detected by the strain layer 21 inside the sphere; the strain spring 222, which was previously under a specific compression, will deform under the corresponding tensile and compressive stress conditions. The spring deformation is equivalent to acting on the strain wire (the strain wire is made of nickel-chromium alloy). The change in resistance caused by the change in the elongation of the strain wire is used to obtain the strain value of the cross-shaped component. The corresponding spherical shell strain and cross-shaped component strain are transmitted to the data acquisition and transmission unit 3 through the strain transmission wire 26 and the strain wire.

[0034] The process of measuring the three-dimensional stress of rock mass using this invention is as follows:

[0035] 1. Preparatory work: Determine the elastic coefficient of the strain layer material and strain spring inside the sphere, set the pre-deformation value of the strain spring, store the above parameters in the data acquisition and transmission unit after the calculation program is written, and start stress measurement. The thickness t of the spherical shell and the pressure it is subjected to meet the following conditions: (See the literature "Calculation and analysis of stress intensity of self-reinforced external pressure spherical shell", Qu Wenxin, Gu Lang, Ma Libin, Shipbuilding Engineering, 2015, 37(10):98-101)

[0036]

[0037] The spherical shell is designed as an ideal elastoplastic material, σ s Let P be the yield limit of the spherical shell. To ensure measurement accuracy, the stress on the spherical shell must not exceed its yield limit, thus yielding the critical pressure P that the spherical shell can withstand. c Meanwhile, R out R in Let t be the inner diameter and outer diameter of the spherical shell, respectively. The difference between the two is the thickness t of the spherical shell.

[0038] Within the aforementioned pressure range, the radial stress and circumferential stress experienced by the spherical shell are:

[0039]

[0040]

[0041] σ r ' is radial stress, σ θ It is the circumferential stress, P is the pressure on the spherical shell, and r is the distance from any point inside the spherical shell to the center of the sphere. The circumferential stress is a stress component in the first direction of the point to be measured.

[0042] When r→Rin At that time, the radial stress experienced by the strain layer inside the sphere is:

[0043]

[0044] Therefore, the radial strain generated by the spherical shell can be obtained as:

[0045]

[0046] The strain in the cross-shaped component produced by the spherical shell is:

[0047]

[0048] In the formula, x and y represent the two directions of the cross-shaped component. For a spherical shell, the strain in both directions is the same, but in actual engineering, different situations may arise due to varying resistance. E1 and E2 are the tensile and compressive elastic moduli of the strain layer, respectively, and μ1 and μ2 are the tensile and compressive Poisson's ratios of the strain layer, respectively. Based on the above strain, by substituting the material constants of the corresponding strain layer and strain spring within the sphere, the stress data in the corresponding directions can be obtained.

[0049] The following example illustrates the use of a spherical shell with an outer radius of 8.5 cm, an inner radius of 7.5 cm, a load of 5 MPa, a nickel-chromium alloy as the strain layer material, and an elastic modulus and Poisson's ratio of 200 GPa and 0.25 respectively (assuming the elastic deformation range is the same for tension and compression parameters). The strain spring is also designed with a nickel-chromium alloy elastic modulus of 200 GPa.

[0050] Substituting the above parameters, the radial stress and circumferential stress of the spherical shell are 7.3 MPa and 0.91 MPa, respectively. Furthermore, the radial strain and the strain in the direction of the cruciform component are 3.42 e. -5 -5.71e -6 Thus, the stress in the direction of the cross-shaped component is 1.14 MPa.

[0051] like Figure 5 and Figure 6 As shown, the radial and circumferential stresses of the spherical shell vary with the thickness of the shell.

[0052] Figure 5 In the figure, 5.0 mm to 15.0 mm represents the thickness of the spherical shell, and the curve shows the variation of radial stress along the shell thickness.

[0053] The stress directions of radial stress and circumferential stress are determined by setting a contact position sensor in the strain layer 21 inside the sphere. The plane with the line connecting this position and the center of the sphere as the normal is the location of the cross-shaped stress.

[0054] 2. Under known stress conditions, the measuring device of the present invention is tested to verify whether the above process can be implemented normally. If a fault occurs, the measuring device is adjusted. After it is correct, the rock mass stress can be measured in actual operation.

[0055] 3. Drill a hole at the location where ground stress measurement is required, then place the measuring device of the present invention into the hole and seal it. Select the measurement time as needed to perform stress measurement, and transmit the data to the receiving antenna through the electromagnetic wave transmitting antenna in the data acquisition and transmission unit.

[0056] To demonstrate the principle of this method—that a spherical shell will deform laterally under radial force—the numerical calculation software ABAQUS was used to analyze the influence of variations in the spherical shell's radius, thickness, and load magnitude on its deformation characteristics.

[0057] like Figure 7 As shown, simulated deformation diagrams are displayed for radii of the spherical shell at 17cm, 19cm, 21cm, and 23cm. When the thickness of the spherical shell is 1cm, under a pressure of 5MPa, the upper and lower ends of the spherical shell deform towards the center of the sphere. The amount of deformation increases with the increase of the radius of the spherical shell, starting from a maximum value of 1.278e. -2 mm increased to 2.575e -2 mm. Simultaneously, the spherical shell deforms outwards from the center of the sphere in the direction perpendicular to the compression direction, and with increasing size, the maximum deformation in the direction perpendicular to the compression direction increases from 2.943e. -1 mm increased to 9.132e -1 mm.

[0058] like Figure 8 As shown, the simulated deformation diagrams of the spherical shell under loads of 5MPa, 10MPa, 15MPa, and 20MPa are presented. When the thickness of the spherical shell is 1cm and the size of the spherical shell is 17cm, the upper and lower ends deform towards the center of the sphere under pressure. The amount of deformation increases with the increase of pressure, starting from a maximum value of 1.278e. -2 mm increased to 5.113e -2 mm. Simultaneously, the spherical shell deforms outwards from the center of the sphere in the direction perpendicular to the pressure, and the maximum deformation in the direction perpendicular to the pressure increases from 2.943e... -1 mm increased to 1.177e 0 mm.

[0059] like Figure 9 As shown, simulated deformation diagrams are displayed for spherical shell thicknesses of 1cm, 2cm, 3cm, and 4cm. When the spherical shell is 17cm in size, under a pressure of 5MPa, both ends of the shell deform towards the center. The amount of deformation decreases with increasing thickness, starting from a maximum value of 1.278e.-2 mm decreased to 6.436e -4 mm. Simultaneously, the spherical shell deforms outwards from the center of the sphere in the direction perpendicular to the compression. With increasing thickness, the maximum deformation in the direction perpendicular to the compression increases from 2.943e. -1 mm decreased to 2.558e -3 mm.

Claims

1. A three-dimensional rock mass stress measuring device, characterized in that: It includes a spherical shell (1), a ground stress measurement unit (2) and a data acquisition and transmission unit (3). The ground stress measurement unit (2) is set inside the spherical shell (1). The ground stress measurement unit (2) includes a spherical strain layer (21) for measuring the stress in one compressive direction and a cross-shaped component (22) for measuring two other stresses on a plane with the compressive direction as the normal. The end of the cross-shaped component (22) is a rolling conductive structure (23) that contacts the inner wall of the spherical shell (1). The data acquisition and transmission unit (3) for recording the ground stress measurement value is provided at the center intersection of the cross-shaped component (22). The spherical shell (1) is the stress-bearing body of the rock mass, and the strain layer (21) inside the sphere completely covers the inner layer of the spherical shell. The strain layer (21) inside the sphere reflects the strain of the spherical shell (1) in the direction of compression inside the sphere under the action of rock mass stress; When the spherical shell (1) is deformed by force, the rolling conductive structure (23) drives the cross-shaped component (22) to move inside the spherical shell (1), so that the cross-shaped component (22) is positioned in the plane with the direction of pressure as the normal; the cross-shaped component (22) detects the strain of the spherical shell in the x and y directions in the plane with the direction of pressure as the normal; The radial strain in the compressive direction is: , The strain in the direction of the cross-shaped component is: , In the formula, σ r σ is the stress in the compressive direction inside the sphere. θ Let x and y represent the circumferential stress of the spherical shell, x and y represent the two directions of the cross-shaped component, E1 and E2 represent the tensile and compressive elastic moduli of the strain layer inside the sphere, and μ1 and μ2 represent the tensile and compressive Poisson's ratios of the strain layer inside the sphere, respectively. Substituting the material constants of the corresponding strain layer and strain spring inside the sphere, the stress data in the corresponding directions are obtained. The cross-shaped component (22) is a cross-shaped rigid structure, including a positioning tube (221), a strain spring (222) and a guide rod (223). The positioning tube (221) is broken in the middle and then connected by the strain spring (222). The two ends of the strain spring (222) are inserted into the two sections of the positioning tube (221) through spring fixing rings (27). The guide rod (223) passes through the inner ring of the strain spring (222). The positioning tube (221) is sleeved around the extension section of the guide rod (223), and the strain transmission wire (26) passes through the inner hole. The strain wire is provided parallel to the strain spring (222). The rolling conductive structure (23) includes a hemispherical shell constraint (231), a metal ball (232) and a conductive tray (233). The hemispherical shell constraint (231) contains a metal ball (232), which rolls close to the strain layer (21) inside the ball. The conductive tray (233) abuts against the rolling metal ball (232) on the front and is connected to the strain transmission wire (26) on the back. The hemispherical shell constraint (231) is connected to the end of the positioning tube (221), and the end of the guide rod (223) is connected to the conductive tray (233).

2. The three-dimensional rock mass stress measuring device according to claim 1, characterized in that: The spherical shell (1) consists of an upper hemisphere (11) and a lower hemisphere (12). The two hemispheres are connected by a pre-set interface thread (14) on the hemisphere interface (13). The inner layer of the spherical shell is attached with an inner strain layer (21).

3. The three-dimensional rock mass stress measuring device according to claim 2, characterized in that: The inner strain layer (21) is made of nickel-chromium alloy. The inner strain layer (21) is in rolling contact with the rolling conductive structure (23) to output the strain signal of the inner strain layer (21).

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