Coal mine working face mining-induced stress testing method based on static expanding agent
By using static expansion agents in the borehole to construct a rigid connection interface, the problem of inaccurate monitoring of traditional borehole stress gauges under complex coal seam geological conditions is solved, and high-precision mining stress measurement and dynamic disaster warning are achieved.
Patent Information
- Application Number
- CN202510914660.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-03
- Publication Date
- 2025-10-10
AI Technical Summary
Traditional borehole stress gauges are difficult to accurately monitor mining stress under complex coal seam geological conditions. They are affected by the adaptability of the aperture, the reliability of the equipment placement, and the stability of the contact interface, resulting in inaccurate dynamic disaster warnings.
A static expansion agent is used to form a closed space in the borehole. During the solidification process, the static expansion agent forms a rigid connection with the coal body around the borehole, constructing an active contact interface to achieve stress transfer, avoiding dependence on the borehole diameter and collapse.
It achieves high-precision mining stress monitoring under different coal mine conditions, reduces construction difficulty and equipment loss, and provides reliable early warning of dynamic disasters in deep coal mines.
Smart Images
Figure CN120759636A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a coal mine working face mining stress testing method based on a static expansion agent, and belongs to the technical field of coal mine production safety. Background Art
[0002] Accurately monitoring the distribution and variation of mining stress at the working face is a key technical means to provide early warning of dynamic disasters such as rock burst and coal wall spalling. The current mainstream mining stress testing method in the industry mainly relies on borehole stress gauges for monitoring. This type of equipment injects hydraulic medium into the borehole, causing the stress gauge body to expand and fit the hole wall. When the surrounding rock stress subsequently changes, the surrounding rock stress can be transmitted to the stress gauge to change its internal hydraulic conditions, thereby converting the surrounding rock stress changes into hydraulic signals inside the equipment for collection. However, this traditional borehole stress gauge has exposed significant adaptability defects in actual engineering applications. The core problem is the inherent contradiction between the expansion capacity of the stress gauge and the complex geological conditions of the coal seam.
[0003] Coal seams in coal mines are generally characterized by well-developed bedding and unevenly distributed fractures. The accuracy of borehole diameter control during drilling is significantly affected by geological conditions. Traditional borehole stress gauges have a limited effective expansion range, requiring the difference between the borehole diameter and the gauge diameter to be controlled within a limited range. If the difference between the initial diameter of the gauge and the borehole diameter exceeds its expansion range, the expansion of the sensor alone will make it difficult to achieve uniform and close contact with the borehole wall. Consequently, stresses in the surrounding rock cannot be accurately transmitted to the gauge, seriously compromising the reliability of dynamic disaster warnings. Because existing stress measurement methods place extremely stringent requirements on borehole diameter accuracy, drilling operations in complex areas such as soft coal seams and fault fracture zones require significant time. Furthermore, another significant challenge facing coal seam drilling is the risk of hole collapse, which is particularly prominent in deep mining and high-stress areas. Due to the low compressive strength of the coal mass, the hole wall is unstable after formation, and disturbances caused by the drill bit during drilling can easily cause hole wall collapse. The outer diameter of a traditional borehole stress gauge is close to the borehole diameter. Once a collapse occurs, the broken coal and rock particles will quickly fill the gap, causing a sharp increase in the stress gauge's pushing resistance, making it difficult to install the stress gauge at the predetermined position. In addition, even if the stress gauge overcomes the collapse obstacle and reaches the designated position, the residual rock chips in the borehole will cause poor contact after the subsequent expansion of the stress gauge, which will still seriously affect the test accuracy. The reason is that the traditional stress gauge relies on its own expansion force to squeeze the rock chips and cannot effectively compact the loose particles, resulting in the formation of a "rock chip buffer layer" between the stress gauge and the hole wall, which ultimately makes the mining stress monitoring during the working face mining process inaccurate. In summary, the systematic defects of traditional mining stress testing technology in terms of aperture adaptability, equipment positioning reliability and contact interface stability have become a technical shortcoming that restricts the safe mining of deep coal mines.
[0004] Therefore, how to provide a new working face mining stress testing method that can achieve high-precision monitoring of mining stress without considering the size of the borehole diameter and whether there is a risk of collapse, and is applicable to different coal mine conditions, is the research direction required by the present invention. Summary of the Invention
[0005] In response to the problems existing in the above-mentioned prior art, the present invention provides a coal mine working face mining stress testing method based on static expansion agent. By actively constructing a stable contact interface, it can achieve high-precision monitoring of mining stress without considering the size of the borehole diameter and whether there is a collapse hole, and is suitable for different coal mine conditions.
[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for testing mining stress of a coal mine working face based on a static expansion agent, comprising the following steps:
[0007] Step 1: Select the stress test location: First, determine the stress test depth of the coal seam and drill a hole in the coal seam in the area not affected by mining until the test depth is reached;
[0008] Step 2: Borehole pressure measurement layout: Connect the pressure measuring device and the sealing device, and extend both into the borehole so that the borehole pressure measuring device reaches the required test depth. Then connect the special pressure gauge and pressure pump to the pressure measuring device;
[0009] Step 3: Sealing and Expansion Agent Injection: The sealing device is expanded to press and seal against the borehole wall, placing the pressure measuring device in a closed space. The closed space is then filled with static expansion agent. After the static expansion agent solidifies, it couples the exterior of the pressure measuring device with the coal body surrounding the borehole to form a rigid connection.
[0010] Step 4. Monitoring of coal mining stress: Before monitoring, first inject hydraulic oil into the pressure measuring device through the pressure pump until the pressure measuring device reaches the required pressure value, then turn off the pressure pump and maintain the current pressure as the initial pressure value; when the mining stress caused by the working face mining affects the coal body around the borehole, the stress on the coal body is transmitted to the pressure measuring device through the static expansion agent. The pressure measuring device is squeezed and deformed by the stress, and then pressurizes the internal hydraulic oil. The special pressure gauge obtains the actual pressure value in real time, and the actual pressure value is subtracted from the initial pressure value to obtain the real-time mining stress value. The above-mentioned special pressure gauge has been corrected and debugged through preliminary experiments. The actual pressure value it displays is the sum of the internal hydraulic pressure value and the deformation pressure borne by the hydraulic cavity (that is, the original real-time hydraulic value plus the deformation pressure borne by the hydraulic cavity is the actual pressure value). The reason for using a dedicated pressure gauge is that when the hydraulic cavity is subjected to stress from the surrounding rock mass, it itself will bear a portion of the stress value, that is, it will bear a certain stress when the hydraulic cavity is not deformed. Only after it is deformed will the remaining stress be used as pressure to apply pressure to the hydraulic oil. Therefore, if only the changes in the internal hydraulic oil are measured, the stress changes cannot be accurately obtained. Therefore, it is necessary to consider the deformation pressure borne by the hydraulic cavity to ensure the accuracy of stress measurement.
[0011] Furthermore, the pressure measuring device is a hydraulic chamber, which is made of high-strength alloy steel; the sealing device includes a sealing bag, a grouting pipe, an injection pipe and a hollow fixed rod, the grouting pipe is used to inject grouting into the sealing bag to make it expand and seal the borehole to form a closed space, and the injection pipe passes through the sealing bag to inject a static expansion agent into the closed space; one end of the hollow fixed rod is fixedly connected to the hydraulic chamber, and the other end passes through the sealing bag and is provided with a connector, which is used to make the hydraulic chamber and the sealing device extend into the borehole synchronously.
[0012] Furthermore, it also includes a protective cap, a three-way joint, a stop valve, a one-way valve and a push rod. The protective cap is installed on the end face of the hydraulic chamber extending into the borehole, and is used to protect the hydraulic chamber during the process of extending into the borehole; the special pressure gauge and the pressure pump are respectively connected to the two ports of the three-way joint through the hydraulic pipe, and the remaining port of the three-way joint is connected to the hydraulic chamber through the hydraulic pipe through the hollow fixed rod; the stop valve is installed on the hydraulic pipe between the pressure pump and the three-way joint, and is used to control the on-off between the pressure pump and the hydraulic chamber; the one-way valve is installed on the injection pipe, and is used to prevent the static expansion agent from flowing back when it is injected into the closed space; one end of the push rod is connected to the connector, and is used to push the pressure measuring device and the sealing device into the borehole. Through these structures, it can be effectively ensured that the pressure measuring device and the sealing device are installed in the required position, and that the two devices can play the required role, and ultimately achieve accurate monitoring of mining stress.
[0013] Furthermore, in step 3, when injecting the static expansion agent, the static expansion agent injection is completed when the static expansion agent fills the enclosed space and the pressure reaches 1 MPa. This ensures that when the static expansion agent solidifies, the outer portion of the pressure measuring device can be coupled to the coal body around the borehole to form a rigid connection.
[0014] Furthermore, the initial pressure value of the pressure measuring device in step 4 is 5 MPa. This pressure value ensures that the hydraulic cavity is in full contact with the static expansion agent, ensuring a rigid connection between the pressure measuring device, the static expansion agent, and the coal body around the borehole, thereby achieving stable transmission of mining stress.
[0015] Compared with the prior art, the present invention first forms a closed space inside the borehole through a sealing device, places the pressure measuring device in the closed space, and then fills the closed space with a static expansion agent. The expansion stress generated by the static expansion agent during the solidification process can actively fill the irregular gap between the inner wall of the borehole and the pressure measuring device and overcome the influence of drill cuttings, forming an integral structure that matches the mechanical properties of the coal seam, so that the outside of the pressure measuring device is coupled with the coal body around the borehole to form a rigid connection, forming an active contact interface construction method. This method does not need to consider the matching degree between the borehole diameter and the pressure measuring device, so that the size of the borehole diameter can be adjusted as needed during drilling. In addition, since the borehole does not need to be matched, the borehole diameter can be constructed larger in special cases such as soft coal seams. In this way, even if the borehole collapses, the pressure measuring device can be sent to the required test depth position of the borehole due to the larger aperture. In addition, in this method of the present invention, the drill cuttings generated by the collapse of the borehole inside the borehole can be solidified and filled with static expansion agent to form an integral structure, and will not affect the subsequent mining stress test accuracy. Therefore, the mining stress testing method constructed by the present invention breaks through the inherent mode of "equipment size matching-passive expansion fitting", and realizes the transformation from adaptive technology relying on drilling accuracy to technology of active control of contact interface through the innovative principle of "active expansion anchoring-interface coupling-full medium stress transfer". Its core advantage is not only to solve the engineering problems such as hole collapse, aperture deviation, and rock debris interference in soft coal seams, but also to build a monitoring system coordinated with coal seam deformation through the synergistic effect of static expansion agent and grouting sealing, which provides reliable technical support for the accurate early warning of dynamic disasters such as rock burst in deep coal mines, significantly reduces the construction difficulty and equipment loss while improving the monitoring accuracy, and has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a schematic diagram of the construction layout of the present invention.
[0017] In the figure: 1-coal body, 2-drill hole, 3-protective cap, 4-hydraulic chamber, 5-hollow fixing rod, 6-sealing bag, 7-check valve, 8-grouting pipe, 9-push rod, 10-liquid injection pipe, 11-special pressure gauge, 12-tee joint, 13-hydraulic pipe, 14-stop valve, 15-pressure pump, 16-connector. DETAILED DESCRIPTION
[0018] The present invention will be further described below.
[0019] like Figure 1 As shown, the present invention includes the following steps:
[0020] Step 1: Select the stress test location: First, determine the stress test depth of the coal seam and drill a coal seam in the coal body 1 in the area not affected by mining until the test depth is reached.
[0021] Step 2. Borehole pressure measurement layout: connect the pressure measuring device to the sealing device, and extend both into the borehole so that the borehole pressure measuring device reaches the required test depth, and then connect the special pressure gauge 11 and the pressure pump 15 to the pressure measuring device; the pressure measuring device is a hydraulic chamber 4, which is made of high-strength alloy steel; the sealing device includes a sealing bag 6, a grouting pipe 8, an injection pipe 10 and a hollow fixed rod 5. The grouting pipe 8 is used to grout the sealing bag 6 to expand it to seal the borehole 2 to form a closed space. The injection pipe 10 passes through the sealing bag 6 to inject a static expansion agent into the closed space; one end of the hollow fixed rod 5 is fixedly connected to the hydraulic chamber 4, and the other end passes through the sealing bag 6 and is provided with a connector 16, which is used to make the hydraulic chamber and the sealing device extend into the borehole synchronously.
[0022] Step 3: Sealing and expansion agent injection construction: The sealing device is expanded to press and seal against the borehole wall, placing the pressure measuring device in a closed space. Static expansion agent is then injected into the closed space. The static expansion agent injection is completed when the closed space is filled with the static expansion agent and the pressure reaches 1 MPa. Wait for more than a week for the static expansion agent to solidify. The static expansion agent will couple the outside of the pressure measuring device with the coal body around the borehole to form a rigid connection.
[0023] Step 4: Coal mining stress monitoring: Before monitoring, hydraulic oil is first injected into the pressure measuring device through the pressure pump 15 until the pressure measuring device reaches 5MPa. The pressure pump 15 is then turned off and the current pressure is maintained as the initial pressure value. This pressure value is used to ensure that the hydraulic chamber 4 is completely pressed into contact with the static expansion agent, ensuring that the pressure measuring device, the static expansion agent, and the coal body around the borehole are rigidly connected, achieving stable transmission of mining stress. When the mining stress caused by the working face mining affects the coal body around the borehole, the stress on the coal body is transmitted to the pressure measuring device through the static expansion agent. The pressure measuring device is squeezed and deformed by the stress, and then pressurizes the internal hydraulic oil. The dedicated pressure gauge 11 obtains the actual pressure value in real time. The actual pressure value is subtracted from the initial pressure value to obtain the real-time mining stress value. The above-mentioned dedicated pressure gauge 11 has been corrected and debugged through preliminary experiments. The actual pressure value it displays is the sum of the internal hydraulic pressure value and the deformation pressure borne by the hydraulic chamber. The reason for using a dedicated pressure gauge 11 is that when the hydraulic chamber 4 is subjected to stress from the surrounding rock mass, it itself will bear a portion of the stress value, that is, it will bear a certain stress when the hydraulic chamber 4 is not deformed. Only after it is deformed will the remaining stress be used as pressure to apply pressure to the hydraulic oil. Therefore, if only the changes in the internal hydraulic oil are measured, the stress changes cannot be accurately obtained. Therefore, it is necessary to consider the deformation pressure borne by the hydraulic chamber 4 to ensure the accuracy of stress measurement.
[0024] As an improvement of the present invention, it also includes a protective cap 3, a three-way joint 12, a stop valve 14, a one-way valve 7 and a push rod 9. The protective cap 3 is installed on the end face of the hydraulic chamber 4 extending toward the borehole 2, and is used to protect the hydraulic chamber 4 during the process of extending into the borehole 2; the special pressure gauge 11 and the pressure pump 15 are respectively connected to the two ports of the three-way joint 12 through the hydraulic pipe 13, and the remaining port of the three-way joint 12 is connected to the hydraulic chamber 4 through the hydraulic pipe 13 through the hollow fixed rod 5; the stop valve 14 is installed on the hydraulic pipe 13 between the pressure pump 15 and the three-way joint 12, and is used to control the on-off between the pressure pump 15 and the hydraulic chamber 4; the one-way valve 7 is installed on the injection pipe 10, and is used to prevent the static expansion agent from flowing back when it is injected into the closed space; one end of the push rod 9 is connected to the connector 16, and is used to push the pressure measuring device and the sealing device into the borehole 2. Through these structures, it can be effectively ensured that the pressure measuring device and the sealing device are installed to the required position, and that the two devices can play the required role, and ultimately achieve accurate monitoring of mining stress.
[0025] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for testing mining stress of coal mine working face based on static expansion agent, characterized in that: The following steps are involved: Step 1: Select the stress test location: First, determine the stress test depth of the coal seam and drill a hole in the coal seam in the area not affected by mining until the test depth is reached; Step 2: Borehole pressure measurement layout: Connect the pressure measuring device and the sealing device, and extend both into the borehole so that the borehole pressure measuring device reaches the required test depth. Then connect the special pressure gauge and pressure pump to the pressure measuring device; Step 3: Sealing and Expansion Agent Injection: The sealing device is expanded to press and seal against the borehole wall, placing the pressure measuring device in a closed space. The closed space is then filled with static expansion agent. After the static expansion agent solidifies, it couples the exterior of the pressure measuring device with the coal body surrounding the borehole to form a rigid connection. Step 4. Coal mining stress monitoring: Before monitoring, first inject hydraulic oil into the pressure measuring device through the pressure pump until the pressure measuring device reaches the required pressure value, then turn off the pressure pump and maintain the current pressure as the initial pressure value; when the mining stress caused by the working face mining affects the coal body around the borehole, the stress on the coal body is transmitted to the pressure measuring device through the static expansion agent, and the pressure measuring device is squeezed and deformed by the stress, and then pressure is applied to the internal hydraulic oil. The dedicated pressure gauge obtains the actual pressure value in real time, and the actual pressure value is subtracted from the initial pressure value to obtain the real-time mining stress value.
2. The method for testing mining stress of a coal mine working face based on a static expansion agent according to claim 1, characterized in that: The pressure measuring device is a hydraulic chamber, which is made of high-strength alloy steel; the sealing device includes a sealing bag, a grouting pipe, a liquid injection pipe and a hollow fixed rod, the grouting pipe is used to inject grouting into the sealing bag to make it expand and seal the borehole to form a closed space, and the liquid injection pipe passes through the sealing bag to inject a static expansion agent into the closed space; one end of the hollow fixed rod is fixedly connected to the hydraulic chamber, and the other end passes through the sealing bag and is provided with a connector, which is used to make the hydraulic chamber and the sealing device extend into the borehole synchronously.
3. The method for testing mining stress of coal mine working face based on static expansion agent according to claim 2, characterized in that: It also includes a protective cap, a three-way joint, a stop valve, a one-way valve and a push rod. The protective cap is installed on the end face of the hydraulic chamber extending into the borehole, and is used to protect the hydraulic chamber during the process of extending into the borehole; the special pressure gauge and the boosting pump are respectively connected to the two ports of the three-way joint through hydraulic pipes, and the remaining port of the three-way joint is connected to the hydraulic chamber through a hydraulic pipe through a hollow fixed rod; the stop valve is installed on the hydraulic pipe between the boosting pump and the three-way joint, and is used to control the on-off between the boosting pump and the hydraulic chamber; the one-way valve is installed on the injection pipe, and is used to prevent the static expansion agent from flowing back when it is injected into the closed space; one end of the push rod is connected to the connector, and is used to push the pressure measuring device and the sealing device into the borehole.
4. The method for testing mining stress of coal mine working face based on static expansion agent according to claim 1, characterized in that: In step three, when injecting the static expansion agent, the injection of the static expansion agent is completed when the static expansion agent fills the closed space and the pressure reaches 1 MPa.
5. The method for testing mining stress of coal mine working face based on static expansion agent according to claim 1, characterized in that: The initial pressure value of the pressure measuring device in step 4 is 5 MPa.