A one-hole multi-point liquid-filled expansion pillow type borehole stress meter

Abstract

The present application relates to a kind of one-hole multi-point position liquid-filled expansion pillow type borehole stress meter, including expansion pillow, pressure detector and oil pipe, the expansion pillow is the closed tubular structure, oil pipe is connected with the one end of expansion pillow, the outer ring of the expansion pillow is equipped with the recessed tube wall and forms the avoidance slot inwards, the avoidance slot extends along the length direction of expansion pillow and is through the length direction of expansion pillow, oil pipe can be housed in the avoidance slot, the avoidance slot is at least equipped with two and is uniformly distributed along the circumference, by setting avoidance slot on expansion pillow, the oil pipe of other expansion pillow set can be passed, when measuring the stress of multiple points, multiple stress meters are loaded into one by one, the oil pipe of stress meter in deeper position needs to cross the stress meter in shallower position, oil pipe passes from avoidance slot, thus can measure the rock stress of multiple different depth positions in one hole, to increase the field practicability and applicability of borehole stress monitoring, improve the accuracy of rock burst monitoring and early warning.

Description

Technical Field

[0001] This invention relates to the field of borehole stress gauges, specifically to a multi-point fluid-filled expansion pillow-type borehole stress gauge. Background Technology

[0002] Mining operations alter the stress field of the original rock, meaning that mining activities change the stress state of the original rock, leading to a new stress state. Therefore, predicting and evaluating the rockburst hazard of coal and rock strata from a stress field perspective, and researching stress monitoring sensors for deep mining rockburst disaster areas, is of practical significance.

[0003] Currently, the most common equipment for monitoring mining-induced stress is the hydrostatic pillow-type borehole stress gauge, which has advantages such as low cost, simple construction, high stability, and the ability to perform long-term real-time online monitoring, and is widely used in mining-induced stress monitoring. However, the hydrostatic pillow-type stress gauge still faces some technical challenges, mainly: ① Due to the limitations of the oil drum structure, it can only perform unidirectional monitoring, requiring high precision in on-site installation, and its installation is somewhat arbitrary when the direction of the principal stress cannot be determined; ② It has poor coupling with the borehole, especially in boreholes prone to collapse, where installation requirements cannot be met, resulting in poor monitoring performance.

[0004] Common borehole stress gauges are typically single-point gauges, meaning only one gauge can be placed per hole due to their shape. Each gauge can only measure stress at one point. However, predicting the variation of stress fields in a large-scale surrounding rock requires monitoring stress at multiple points at different depths. Therefore, multiple holes at different depths need to be drilled to detect stress states at different depths. Borehole stress gauges are generally installed in deep blind holes with a diameter of 45–50 mm. These holes are quite deep, typically over 8 meters. Drilling multiple holes to meet the requirements for multi-point measurements increases the difficulty, cost, and material and financial resources required.

[0005] For those skilled in the art, increasing the field applicability and applicability of borehole stress monitoring and improving the accuracy of rockburst monitoring and early warning are technical problems that need to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a multi-point liquid-filled expansion pillow-type borehole stress gauge.

[0007] This invention is achieved through the following technical solution: a multi-point fluid-filled expansion pillow type borehole stress gauge is provided, including an expansion pillow, a pressure detector, and an oil pipe connecting the expansion pillow and the pressure detector. The expansion pillow is a closed circular tube structure. The oil pipe is connected to one end of the expansion pillow. The outer ring of the expansion pillow is provided with a relief groove formed by the inward indentation of the pipe wall. The relief groove extends along the length direction of the expansion pillow and penetrates the length direction of the expansion pillow. The oil pipe can be accommodated in the relief groove. There are at least two relief grooves.

[0008] The clearance groove in this design allows the oil pipes installed on other expansion pillows to pass through. When measuring stress at multiple points, multiple stress gauges are installed into the borehole one by one. The oil pipes of the stress gauges located at deeper positions need to pass over the stress gauges located at shallower positions. The oil pipes pass through the clearance groove, so it is possible to measure the stress of rock strata at multiple different depths in one borehole. At the same time, due to the clearance groove, the cross-section of the expansion pillow is made into a wave-like structure, which allows the expansion pillow to expand and open in a better circumferential direction.

[0009] As an optimization, the cross-section of the clearance groove is V-shaped. In this design, the cross-section of the clearance groove is V-shaped, and the included angle of the V-shape increases during expansion, thereby allowing the expansion pillow to expand and open more circumferentially.

[0010] As an optimization, four clearance slots are provided. In this design, four clearance slots are provided, allowing for a maximum of five stress gauges to be installed in a single borehole.

[0011] As an optimization, the position of the oil pipe within the clearance groove is lower than the minimum diameter of the expansion joint. This prevents the oil pipe from contacting the borehole wall, resulting in more accurate detection.

[0012] As an optimization, multiple clearance grooves are evenly distributed circumferentially. The even distribution of clearance grooves circumferentially ensures uniform circumferential expansion of the expansion pillow.

[0013] As an optimization, the depth of the clearance groove is 0.5 to 0.8 times the radius of the expansion pillow. In this design, the depth of the clearance groove is 0.5 to 0.8 times the radius of the expansion pillow, which facilitates the passage and installation of the oil pipe and the expansion of the expansion pillow.

[0014] As an optimization, the oil pipe is connected to the pressure detector via a three-way valve. The three-way valve in this design allows for switching between filling the expansion tank with oil and pressure detection after filling.

[0015] As an optimization, the two ends of the expansion pillow are tapered. This facilitates the guiding and installation of the expansion pillow within the borehole.

[0016] As an optimization, the oil pipe is equipped with an installation plug. The installation plug facilitates the connection of multiple stress gauges, and the stress gauge depth can be adjusted by adding more pipeline.

[0017] As an optimization, the expansion pillow has the same thickness at all points in the cross-section, so that it can be manufactured from a single seamless tube through extrusion, diameter reduction, and end capping.

[0018] The beneficial effects of this invention are as follows: The multi-point fluid-filled expansion pillow type borehole stress gauge of this invention, by setting a clearance groove along the length direction on the expansion pillow, allows oil pipes installed on other expansion pillows to pass through. When measuring stress at multiple points, multiple stress gauges are installed one by one. The oil pipe of the stress gauge located at a deeper position needs to pass over the stress gauge located at a shallower position. The oil pipe passes through the clearance groove. Therefore, it is possible to measure the rock stress at multiple different depths in one borehole, thereby increasing the field practicality and applicability of borehole stress monitoring and improving the accuracy of rockburst monitoring and early warning. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention;

[0020] Figure 2 This is a schematic cross-sectional view of the expansion pillow before stamping in this invention;

[0021] Figure 3 This is a schematic cross-sectional view of the expansion pillow after stamping according to the present invention;

[0022] Figure 4 This is a schematic cross-sectional view of the expansion pillow after stamping and its fit with the oil pipe of the present invention;

[0023] Figure 5 This is a cross-sectional schematic diagram along the length of the expansion pillow of the present invention;

[0024] Figure 6 This is a schematic diagram showing the interaction of two borehole stress gauges according to the present invention;

[0025] Figure 7 This is a schematic diagram showing the interaction of the five borehole stress gauges of the present invention;

[0026] As shown in the figure:

[0027] 1. Expansion pillow; 11. Clearance groove; 2. Oil pipe; 3. Mounting plug; 4. Pressure detector; 5. Three-way valve. Detailed Implementation

[0028] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0029] like Figures 1-7 As shown, the present invention discloses a multi-point fluid-filled expansion pillow type borehole stress gauge, including an expansion pillow 1, a pressure detector 4, and an oil pipe 2 connecting the expansion pillow 1 and the pressure detector 4. The expansion pillow 1 is a closed cylindrical structure, and the degree of expansion is controlled by the oil filling inside, so as to fully contact the coal seam or rock wall and thus enable omnidirectional detection. The two ends of the expansion pillow 1 are conical to facilitate the guiding installation of the expansion pillow in the borehole.

[0030] The expansion pillow 1 is made of materials such as stainless steel tube, copper tube, and alloy tube, which have excellent ductility and can fully accommodate the expansion of the expansion pillow 1. The expansion pillow 1 is made of a single seamless tube through extrusion, diameter reduction, and end capping, thus it can withstand higher pressure.

[0031] The oil pipe 2 is connected to one end of the expansion cushion 1, enabling the supply of hydraulic oil to the expansion cushion 1; the oil pipe 2 is equipped with an installation plug 3. Thus, the oil pipe can be lengthened or extended by the installation plug 3 to accommodate different detection depths.

[0032] The oil pipe 2 is connected to the pressure detector 4 via a three-way valve 5. When the three-way valve 5 is connected to an external oil filling device, the expansion pillow 1 can be filled with oil. After the oil filling is completed, the oil pipe 2 is connected to the pressure detector 4.

[0033] The outer ring of the expansion pillow 1 is provided with a relief groove 11 formed by the inward indentation of the tube wall, so the thickness of the expansion pillow 1 is the same at all points in the cross-section, such as... Figure 2 As shown, the depth of the clearance groove 11 is 0.5 to 0.8 times the radius of the expansion pillow 1, and the cross-section of the clearance groove 11 is V-shaped. When the expansion pillow 1 expands, the included angle of the V-shape increases to... Figure 3 , 4 The arc shape is shown. Oil pipe 2 is a rigid metal pipe, which prevents it from being squeezed and deformed.

[0034] The oil pipe 2 can be accommodated in the relief groove 11. That is, whether before or after expansion, the oil pipe 2 is located within the outer circle of the expansion pillow 1. Furthermore, the position of the oil pipe 2 in the relief groove 11 is lower than the minimum diameter (diameter before expansion) of the expansion pillow 1, so that the oil pipe 2 does not contact the borehole wall, making the detection more accurate.

[0035] The clearance groove 11 extends along the length of the expansion pillow 1 and penetrates the length of the expansion pillow 1, so that the oil pipe 2 can pass through the expansion pillow 1.

[0036] At least two clearance slots 11 are provided, and multiple clearance slots 11 are evenly distributed along the circumference. In this embodiment, four clearance slots 11 are provided.

[0037] Method of using this invention:

[0038] Before hydraulic oil is injected into the expansion pillow 1, the outer circumference of the expansion pillow 1 is smaller than the size of the borehole, allowing it to be inserted into the borehole. After the expansion pillow 1 is inserted into the designated position in the borehole drilled in the coal seam or rock wall, hydraulic oil is injected into the expansion pillow 1 through the oil pipe 2. The volume of the expansion pillow 1 increases, and the expansion pillow 1 expands circumferentially, thus making close contact with the coal seam or rock wall. The amount of oil injected is controlled to maintain the oil pressure at a certain set value. The oil pressure in the oil pipe 2 is continuously monitored by the pressure detector 4. When the stress state of the coal seam or rock wall changes during the mining process, the pressure of the coal seam or rock wall and the expansion pillow 1... The interaction force between the coal seam or rock wall and the expansion pillow 1 changes, which in turn causes changes in oil pressure. When the interaction force between the coal seam or rock wall and the expansion pillow 1 decreases, the oil pressure in the expansion pillow 1 and the oil pipe 2 decreases. When the interaction force between the coal seam or rock wall and the expansion pillow 1 increases, the oil pressure in the expansion pillow 1 and the oil pipe 2 increases. The pressure detector 4 detects the oil value in real time and calculates the stress change of the coal seam or rock wall at the detection location based on the oil pressure value. Since the expansion pillow 1 is a circular tubular structure, after it is circumferentially opened, it can make close contact with the coal seam or rock wall, thereby achieving omnidirectional detection of the borehole.

[0039] The present invention provides a clearance groove 11 along the length direction on the expansion pillow 1. The length direction of the clearance groove 11 is consistent with the length direction of the borehole and the extension direction of the oil pipe. The clearance groove 11 allows the oil pipes 2 installed on other expansion pillows 1 to pass through. The oil pipe on one stress gauge passes through other expansion pillows 1 in the path of extending towards the borehole opening and passes through the clearance grooves 11 of other expansion pillows 1. The oil pipe 2 is not squeezed by the coal seam or rock wall and has enough space to pass through. Therefore, multiple stress gauges can be arranged in one hole at the same time, and multi-point measurement can be achieved by drilling one hole.

[0040] like Figure 6 The diagram shows the structure of the two stress gauges working together in this invention. The two stress gauges are placed at corresponding positions in the borehole, one deep and one shallow. The stress gauge on the left is deeper and the stress gauge on the right is shallower. The oil pipe 2 led out from the left stress gauge is led out of the hole through the avoidance groove 11 opened in the expansion pillow 1 of the right stress gauge. Each oil pipe 2 is connected to a pressure detector 4 to detect the stress state of the coal seam or rock wall at the location of each expansion pillow 1.

[0041] like Figure 7The diagram shows a schematic of the structure of five stress gauges working together according to the present invention. When using the stress gauges provided by the present invention, 1 to 5 stress gauges can be installed in one hole, with the left side being deeper and the right side being shallower. The five stress gauges are independently distributed and do not interfere with each other. No other oil pipes 2 pass through the clearance groove 11 on the expansion pad 1 of the leftmost stress gauge. One oil pipe 2 passes through the clearance groove 11 on the expansion pad 1 of the second stress gauge from the left, and so on. Four oil pipes 2 pass through the clearance groove 11 on the expansion pad 1 of the rightmost stress gauge. The clearance groove 11 on the expansion pad 1 can accommodate a maximum of four oil pipes. The oil pipes on the rightmost stress gauge are directly led out to the outside without passing through other stress gauges. Therefore, in this embodiment, a maximum of five stress gauges can be placed in one borehole. When a stress gauge has already been placed, before inserting the subsequent stress gauge into the borehole, the oil pipe 2 led out by the previous stress gauge is first inserted into the clearance groove 11, and the stress gauge is then fed into the borehole along the direction of the oil pipe 2.

[0042] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.

Claims

1. A multi-point fluid-filled expansion pillow type borehole stress gauge, comprising an expansion pillow (1), a pressure detector (4), and an oil pipe (2) connecting the expansion pillow (1) and the pressure detector (4), characterized in that: The expansion pillow (1) is a closed cylindrical structure. The oil pipe (2) is connected to one end of the expansion pillow (1). The outer ring of the expansion pillow (1) is provided with a relief groove (11) formed by the inward indentation of the pipe wall. The relief groove (11) extends along the length direction of the expansion pillow (1) and penetrates the length direction of the expansion pillow (1). The oil pipe (2) can be accommodated in the relief groove (11). There are at least two relief grooves (11).

2. The multi-point liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The cross-section of the clearance groove (11) is V-shaped.

3. The multi-point liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The clearance slot (11) is provided in four places.

4. The multi-point liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The position of the oil pipe (2) within the clearance groove (11) is lower than the minimum diameter of the expansion pillow (1).

5. A multi-point, liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: Multiple clearance slots (11) are evenly distributed along the circumference.

6. The multi-point liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The depth of the clearance groove (11) is 0.5 to 0.8 times the radius of the expansion pillow (1).

7. The multi-point liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The oil pipe (2) is connected to the pressure detector (4) via a three-way valve (5).

8. A multi-point, liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The two ends of the expansion pillow (1) are conical.

9. A multi-point, liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The oil pipe (2) is equipped with an installation plug (3).

10. A multi-point, liquid-filled expansion pillow-type borehole stress gauge according to claim 1, characterized in that: The expansion pillow (1) has the same thickness at all points on the cross section.

Images