A three-dimensional rock stress in-situ monitoring instrument and monitoring method for underground rock formation

Abstract

The application discloses a kind of three-dimensional rock stress in-situ monitor for underground rock formation and monitoring method, device includes horizontally arranged X-axis stress ring, Y-axis stress ring and Z-axis stress ring;The center of the X-axis stress ring and Y-axis stress ring is equipped with circular cavity, X-axis stress ring is equipped with X-axis stress gauge in the circular cavity, Y-axis stress ring is equipped with Y-axis stress gauge in the circular cavity, the X-axis stress gauge and Y-axis stress gauge are horizontally arranged, and are respectively fixed along X, Y axis direction;The X-axis stress ring and Y-axis stress ring are placed in stack, and the gap is directly reserved between the two, the top of the two is also equipped with connecting ring after stacking, the top of the connecting ring is equipped with connecting pipe;The Z-axis stress ring is equipped at the top of connecting pipe, it is vertically arranged, and is equipped with circular cavity in the center, Z-axis stress gauge is equipped in the circular cavity of Z-axis stress ring, the Z-axis stress gauge is vertically arranged, is fixed along Z axis direction, and the rock stress in three directions is measured respectively.

Description

Technical Field

[0001] This invention belongs to the field of stress monitoring technology, and more specifically, relates to a three-dimensional in-situ rock stress monitoring instrument and method for underground rock strata. Background Technology

[0002] Under normal circumstances, the geological body under underground engineering construction is in a state of stress equilibrium under gravity and compression. However, artificial construction activities, such as blasting and tunnel boring, disrupt this stress equilibrium, causing stress redistribution and uncontrollable release, leading to deformation and collapse of the geological body. In-situ stress is a crucial parameter for the stability of surrounding rock and engineering design in underground engineering, affecting operational safety. Real-time monitoring and analysis are essential, especially in environments with intense tectonic activity and deep burial. An ideal in-situ stress monitoring method should provide highly reliable measurements and be simple and accurate to implement.

[0003] Determining the properties of rock, a fundamental aspect of engineering design, is a crucial indicator at each stage, directly impacting project safety and cost. Indicators related to rock stress include compressive strength, tensile strength, flexural strength, elastic modulus and Poisson's ratio, and shear strength. These indicators are typically determined using core sampling and in-situ testing methods. Core sampling is a laboratory testing method, primarily studying the microstructure, strength, and deformation characteristics of rock. However, any laboratory test result represents characteristic values ​​under specific environmental conditions and has limitations. In-situ testing primarily studies the structure, strength, and deformation characteristics of rock masses. In-situ testing is an indispensable and crucial tool, forming a vital foundation for understanding the stress state of surrounding rock, the changing patterns during tunnel construction and excavation, and controlling its mechanical behavior.

[0004] Currently, most in-situ testing of ground stress uses the stress relief method with hollow inclusions for monitoring. However, hollow inclusions can only perform absolute measurements rather than long-term trend monitoring, and cannot obtain the stress changes during the tunneling process. Moreover, hollow inclusions are expensive, which limits their engineering applications. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a three-dimensional in-situ rock stress monitoring instrument and method for underground rock strata. By setting stress rings in the X, Y, and Z directions, the stress in the rock strata is measured in each of the three directions. Without using strain gauges, the force values ​​are directly measured, and the direction of force is clearly defined. This not only accurately captures the differences in stress magnitude in different directions, avoiding cognitive biases caused by neglecting stress in a particular direction, but also simultaneously determines the action posture of each stress component in the actual geological space. It clearly defines the correspondence between the XYZ axes and geological elements such as the strike, dip, and dip angle of the underground rock mass, thereby comprehensively and accurately reconstructing the spatial distribution characteristics of underground stress and providing complete and reliable basic data for subsequent analysis of how stress affects the rock mass.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a three-dimensional rock stress in-situ monitoring instrument for underground rock strata is provided, comprising a horizontally arranged X-axis stress ring, Y-axis stress ring and Z-axis stress ring;

[0007] The X-axis stress ring and the Y-axis stress ring are provided with a circular cavity at their center. An X-axis stress gauge is provided in the circular cavity of the X-axis stress ring, and a Y-axis stress gauge is provided in the circular cavity of the Y-axis stress ring. The X-axis stress gauge and the Y-axis stress gauge are both horizontally arranged and fixed along the X and Y axes, respectively.

[0008] The X-axis stress ring and the Y-axis stress ring are stacked together with a gap between them. After they are stacked, a connecting ring is provided at the top, and a connecting pipe is provided at the top of the connecting ring.

[0009] The Z-axis stress ring is located at the top of the connecting pipe and is vertically positioned with a circular cavity in the center. A Z-axis stress gauge is installed inside the circular cavity of the Z-axis stress ring. The Z-axis stress gauge is vertically positioned and fixed along the Z-axis direction to measure the stress of the rock strata in three directions.

[0010] Furthermore, the X-axis stress ring, Y-axis stress ring, and connecting ring are provided with multiple connecting holes along their circumference, and connecting screws are provided in the connecting holes. The connecting screws pass through the connecting holes of the X-axis stress ring, Y-axis stress ring, and connecting ring simultaneously, so that they are concentrically arranged.

[0011] The connecting screw is provided with multiple nuts, which are respectively located on both sides of the X-axis stress ring, the Y-axis stress ring and the connecting ring, and are fixed at intervals.

[0012] Furthermore, the X-axis stress ring and the Y-axis stress ring are provided with through mounting holes on their sides, and a fixing hole is also provided on their top surface. The fixing hole extends into the mounting hole, and an adjustable fixing rod is provided in the fixing hole.

[0013] The X-axis stress gauge and the Y-axis stress gauge are respectively installed in the mounting holes of the X-axis stress ring and the Y-axis stress ring on the inner ring, and the X-axis stress gauge and the Y-axis stress gauge are fixed by tightening the fixing rod.

[0014] Furthermore, the Z-axis stress ring is provided with load-bearing plates on both the upper and lower sides, and perforated tubes are connected to both the upper and lower load-bearing plates;

[0015] The flower tube is a hollow tube with holes on its surface, which are reserved for grouting.

[0016] The perforated tube is sleeved with the connecting tube to form a vertical connection with the X-axis stress ring and the Y-axis stress ring;

[0017] The extension line of the Z-axis stress gauge coincides with the central axis of the X-axis stress ring and the Y-axis stress ring.

[0018] Furthermore, the X-axis stress gauge, Y-axis stress gauge, and Z-axis stress gauge all use vibrating wire sensors to measure micro-strain;

[0019] The X-axis stress ring, Y-axis stress ring and Z-axis stress ring are provided with polyurethane foam covering areas. The polyurethane foam covering areas are arranged in pairs, symmetrically arranged on both sides of the stress gauge length direction, and distributed at 90 degrees.

[0020] According to a second aspect of the present invention, a method for in-situ monitoring of three-dimensional rock stress in underground rock strata is provided, specifically including the following steps:

[0021] S100: At the target monitoring rock stratum depth, drill precision mounting holes that match the outer diameters of the X-axis stress ring and Y-axis stress ring of the monitoring instrument, record the actual inclination angle and azimuth angle of the borehole axis, and select a clear structural surface or geographical orientation as a reference to mark its relative position at the borehole opening and inside the borehole.

[0022] S200: On the surface work platform, the X-axis stress ring, Y-axis stress ring and connecting ring are stacked and concentrically fixed in sequence according to the drawing requirements by connecting screws and nuts. The connecting pipe is connected to the flower pipe, and the Z-axis stress ring and load-bearing plate are assembled.

[0023] S300: Lower the assembled and calibrated monitoring instrument to the predetermined monitoring depth in the borehole. During the lowering process, refer to the reference orientation marked in step S100 and adjust the attitude of the monitoring instrument in real time to ensure that the measurement directions of the X-axis stress gauge and the Y-axis stress gauge are aligned with the preset geological structure coordinates.

[0024] S400: After the mechanical anchoring of the X and Y axes is completed, the high-pressure grouting pump is used to inject the grouting material through the grouting holes on the perforated pipe connected to the reserved grouting pipeline on the Z-axis stress ring assembly, so as to realize the rigid coupling of the monitoring instrument with the rock mass in the Z-axis direction.

[0025] S500: Keep the monitor stationary, start the continuous acquisition mode, monitor and record the frequency and temperature data of the X, Y, and Z triaxial stress gauges in real time, and save the readings at this time as the initial zero point value of stress monitoring when the rate of change of the triaxial sensor readings is less than the preset threshold.

[0026] S600: Adjust the data acquisition instrument to long-term automatic monitoring mode, set the data acquisition time interval according to the monitoring requirements, automatically acquire the real-time frequency readings and temperature readings of the X, Y, and Z triaxial stress gauges, initialize the zero point value of the acquired real-time data and perform temperature correction, and then substitute it into the calibration coefficients of each stress gauge to calculate the increment or absolute amount of rock stress in the three orthogonal directions of X, Y, and Z, thereby obtaining complete data on the evolution of the three-dimensional stress field at the monitoring point over time.

[0027] Furthermore, step S500 specifically includes the following steps:

[0028] S501: Set the monitor's operating mode to high-frequency sampling and start continuously collecting data according to preset parameters;

[0029] S502: At each stress gauge, the original vibrating wire frequency is corrected using temperature data to eliminate the influence of temperature drift on the reference value calibration.

[0030] S503: Enables sliding window data buffering, stores the frequency data after temperature compensation for the most recent N cycles into a queue, and continuously calculates the dispersion index within the data window through sliding window statistical analysis.

[0031] S504: Compares the statistical analysis results of the X, Y, and Z channels with the preset stress stability threshold in real time;

[0032] S505: When it is confirmed that the statistical indicators of all channels are below the stable threshold for M consecutive windows, calculate the average value of the data in the last stable window, and write it as the final zero point value into the non-volatile memory, and enter the long-term monitoring mode.

[0033] Further, in step S502, in Raw frequencies are collected at all times. and temperature Then, immediately call the temperature calibration coefficient. The compensated frequency, after eliminating the effect of temperature drift, was calculated. Specifically:

[0034] ,

[0035] in, To calibrate the reference temperature, Indicates the first Secondary sampling.

[0036] Furthermore, in step S503, during the sliding window data buffering process, whenever there is new data... Calculate the window when data enters. Standard deviation of N data points This is used to quantify the dispersion or instability of the current reading, specifically:

[0037] ,

[0038] in, window A single frequency data point within, window The arithmetic mean of N data points.

[0039] Furthermore, step S600 specifically includes the following steps:

[0040] S601: Runs long-interval polling scheduling, wakes up the stress meter and collects data according to the set steady-state interval. This is the system's baseline operating power consumption mode.

[0041] S602: After each data acquisition, a multi-step data conversion is performed, sequentially completing temperature compensation, reference frequency subtraction, and stress value conversion by calling calibration coefficients;

[0042] S603: Compare the calculated new stress value with the stress value of the previous steady-state cycle, calculate the rate of change, and compare it with the preset event trigger threshold.

[0043] S604: Once it is confirmed that the stress change rate of any channel exceeds the limit, immediately execute finite state machine control to switch the system state from steady-state inspection mode to high-frequency event capture mode, and simultaneously adjust the sampling interval to high frequency;

[0044] S605: In high-frequency mode, monitor the stress change rate of the high-frequency data stream. When the change rate falls back below the safety threshold and remains stable for a preset period of time, the system automatically degrades and returns to steady-state inspection mode.

[0045] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0046] 1. The three-dimensional rock stress in-situ monitoring instrument of the present invention measures the stress of rock strata in the three directions by setting stress rings in the X, Y, and Z directions. It does not use strain gauges but directly measures the force value, and the direction of force is clear. It can accurately capture the difference in stress magnitude in different directions, avoiding cognitive bias caused by ignoring stress in a certain direction. It can also simultaneously determine the action posture of each stress component in the actual geological space, and clearly define the correspondence between the XYZ axes and geological elements such as strike, dip, and dip angle of the underground rock mass. Thus, it can comprehensively and accurately restore the spatial distribution characteristics of underground stress, and provide complete and reliable basic data for subsequent analysis of the stress effect on the rock mass.

[0047] 2. The three-dimensional rock stress in-situ monitoring instrument of the present invention uses a bidirectional stress ring composed of an X-axis stress gauge and a Y-axis stress gauge to replace the hollow inclusion in the horizontal direction. The stress change is reflected by monitoring the micro-strain of the stress ring. In terms of construction, two unidirectional stress rings that match the borehole are placed perpendicular to each other to realize stress monitoring in the X and Y directions in the borehole.

[0048] 3. The three-dimensional rock stress in-situ monitoring instrument of the present invention has a Z-axis force gauge installed on the plane perpendicular to the bidirectional stress ring. The design still uses the stress ring to measure the stress value. Under the same stress conditions, the deformation of the stress ring is much greater than the deformation of the rod-shaped sensitive body. To accurately measure the stress at a certain distance in the borehole, the stress ring type force gauge requires the minimum anchoring force, thereby improving the accuracy of Z-axis stress measurement. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the structure of a three-dimensional in-situ rock stress monitoring instrument for underground rock strata according to an embodiment of the present invention;

[0050] Figure 2 This is a front view of a bidirectional stress ring structure of a three-dimensional in-situ rock stress monitoring instrument for underground rock strata, according to an embodiment of the present invention.

[0051] Figure 3 This is a top view of a two-way stress ring structure of a three-dimensional in-situ rock stress monitoring instrument for underground rock strata, according to an embodiment of the present invention.

[0052] Figure 4 This is a top view of the X-axis stress gauge structure of a three-dimensional in-situ rock stress monitoring instrument for underground rock strata according to an embodiment of the present invention;

[0053] Figure 5 This is a schematic diagram of the Z-axis stress ring structure of a three-dimensional rock stress in-situ monitoring instrument for underground rock strata according to an embodiment of the present invention;

[0054] Figure 6This is a schematic diagram of the polyurethane foam covering area of ​​a three-dimensional rock stress in-situ monitoring instrument for underground rock strata according to an embodiment of the present invention;

[0055] Figure 7 This is a schematic flowchart of a three-dimensional in-situ rock stress monitoring method for underground rock strata according to an embodiment of the present invention.

[0056] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-X-axis stress ring, 2-Y-axis stress ring, 3-X-axis stress gauge, 4-Y-axis stress gauge, 5-connecting screw, 6-nut, 7-connecting ring, 8-connecting pipe, 9-Z-axis stress ring, 10-Z-axis stress gauge, 11-bearing plate, 12-floral pipe. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0058] Example 1

[0059] like Figure 1As shown in the figure, this embodiment of the invention provides a three-dimensional in-situ rock stress monitoring instrument for underground rock strata, including a horizontally arranged X-axis stress ring 1, Y-axis stress ring 2, and Z-axis stress ring 9. The X-axis stress ring 1 and Y-axis stress ring 2 have a circular cavity at their center. An X-axis stress gauge 3 is installed inside the circular cavity of the X-axis stress ring 1, and a Y-axis stress gauge 4 is installed inside the circular cavity of the Y-axis stress ring 2. Both the X-axis stress gauge 3 and Y-axis stress gauge 4 are horizontally arranged and fixed along the X and Y axes, respectively. The X-axis stress ring 1 and Y-axis stress ring 2 are stacked, with a gap between them. A connecting ring 7 is provided at the top of the stacked rings, and a connecting pipe 8 is provided at the top of the connecting ring 7. The Z-axis stress ring 9 is located at the top of the connecting pipe 8, is vertically arranged, and has a circular cavity at its center. A Z-axis stress gauge 10 is installed inside the circular cavity of the Z-axis stress ring 9, and the Z-axis stress gauge 10 is vertically arranged and fixed along the Z-axis. By setting stress loops in the X, Y, and Z directions, the stress in the rock strata in each of the three directions is measured directly without using strain gauges. The force direction is clearly defined, which can accurately capture the differences in stress magnitude in different directions, avoiding cognitive bias caused by ignoring stress in a certain direction. At the same time, it can simultaneously determine the behavior of each stress component in the actual geological space, clearly define the correspondence between the XYZ axes and geological elements such as strike, dip, and dip angle of the underground rock mass, and thus comprehensively and accurately restore the spatial distribution characteristics of underground stress, providing complete and reliable basic data for subsequent analysis of how stress affects the rock mass.

[0060] like Figure 2-4 As shown, the X-axis stress ring 1, Y-axis stress ring 2, and connecting ring 7 are provided with multiple connecting holes along their circumference. Connecting screws 5 are installed in the connecting holes, passing through the connecting holes of the X-axis stress ring 1, Y-axis stress ring 2, and connecting ring 7 simultaneously, ensuring their concentric arrangement. Multiple nuts 6 are provided on the connecting screws 5, respectively located on both sides of the X-axis stress ring 1, Y-axis stress ring 2, and connecting ring 7, fixing them at intervals. The X-axis stress ring 1 and Y-axis stress ring 2 have through mounting holes on their sides, and fixing holes extending into the mounting holes on their top surfaces. Adjustable fixing rods are installed in the fixing holes. The X-axis stress gauge 3 and Y-axis stress gauge 4 are respectively installed in the mounting holes of the X-axis stress ring 1 and Y-axis stress ring 2 at both ends, and are fixed by tightening the fixing rods. In the horizontal direction, a bidirectional stress ring composed of an X-axis stress gauge 3 and a Y-axis stress gauge 4 is used to replace the hollow inclusion. The stress change is reflected by monitoring the micro-strain of the stress ring. In terms of construction, two unidirectional stress rings that match the borehole are placed perpendicular to each other to realize stress monitoring in the X and Y directions inside the borehole.

[0061] The connecting ring 7 and the connecting tube 8 are integrally formed, and a cavity is provided in the center of the connecting ring 7, with the connecting tube protruding upward.

[0062] like Figure 5 As shown, the Z-axis stress ring 9 has support plates 11 on both its upper and lower sides, and each support plate 11 is connected to a perforated tube 12. The perforated tube 12 is a hollow tube with holes on its surface, serving as pre-reserved grouting holes. The perforated tube 12 is sleeved with the connecting tube 8 to form a vertical connection with the X-axis stress ring 1 and the Y-axis stress ring 2. The extension line of the Z-axis stress gauge 10 coincides with the central axis of the X-axis stress ring 1 and the Y-axis stress ring 2. A Z-axis force gauge 10 is installed on a plane perpendicular to the bidirectional stress ring. The design still uses the stress ring to measure the stress value. Under the same stress conditions, the deformation of the stress ring is much greater than that of the rod-shaped sensitive body. To accurately measure the stress at a certain distance in the borehole, the stress ring type force gauge requires a minimum anchoring force, thereby improving the accuracy of Z-axis stress measurement.

[0063] like Figure 6 As shown, the X-axis stress gauge 3, Y-axis stress gauge 4, and Z-axis stress gauge 10 all use vibrating wire sensors to measure micro-strain. The X-axis stress ring 1, Y-axis stress ring 2, and Z-axis stress ring 9 are provided with polyurethane foam covered areas. These polyurethane foam covered areas are arranged in pairs, symmetrically positioned on both sides of the stress gauge's length direction, and distributed at 90-degree angles. The polyurethane foam covered areas are positioned within a ±45° range on both sides of the stress ring, allowing them to deform freely within the borehole space and effectively shielding against external forces applied vertically.

[0064] This in-situ stress monitoring instrument is mechanically anchored or bonded grouting anchored, and is divided into two categories according to different rock types:

[0065] 1. Rocks: Hard rocks that are unweathered to moderately weathered, relatively hard rocks, and soft rocks that are unweathered to slightly weathered are classified as rocks;

[0066] 2. Soil type: Various rocks that are strongly weathered to completely weathered, moderately weathered soft rocks, and extremely soft rocks are considered as soil.

[0067] For rock, the conventional anchoring method is to use grouting material injection. For downward drilling, grouting pipes can be arranged at the bottom for grouting. Structurally, the stress rings of the X and Y axes are equipped with cavities for mortar to pass through. The connecting pipes of the X, Y and Z axes are designed as perforated perforated pipes for mortar to pass through. After the grout has completely solidified, the stress gauge is integrated with the borehole.

[0068] For soil types, small hydraulic anchors are installed at the fixed points of the X, Y axis stress gauges and Z axis stress gauges, and hydraulic oil pipes are led to the borehole opening. The hydraulic anchor has three actuators that move synchronously, and each actuator has a spike installed at the front end. During installation, hydraulic oil is injected into the oil pipe to make the actuator of the hydraulic anchor extend and penetrate the borehole wall to fix the instrument.

[0069] The grouting material is cement mortar, cement paste, or fine aggregate concrete. Due to the limitations of the instrument's structure, the delivery channel for the grouting material is relatively narrow, so cement paste is preferred for construction.

[0070] Example 2

[0071] like Figure 7 As shown, this embodiment of the invention provides a method for in-situ monitoring of three-dimensional rock stress in underground rock strata, specifically including the following steps:

[0072] S100: At the target monitoring rock stratum depth, drill precision mounting holes that match the outer diameters of the X-axis stress ring 1 and Y-axis stress ring 2 of the monitoring instrument, record the actual inclination angle and azimuth angle of the borehole axis, and select a clear structural surface or geographical orientation as a reference to mark its relative position at the borehole opening and inside the borehole.

[0073] S200: On the surface work platform, X-axis stress ring 1, Y-axis stress ring 2 and connecting ring 7 are stacked and concentrically fixed in sequence according to the drawing requirements by connecting screw 5 and nut 6. Connecting pipe 8 and flower pipe 12 are sleeved together. Z-axis stress ring 9 and bearing plate 11 are assembled.

[0074] S300: Lower the assembled and verified monitoring instrument to the predetermined monitoring depth in the borehole. During the lowering process, refer to the reference orientation marked in step S100 and adjust the attitude of the monitoring instrument in real time to ensure that the measurement directions of X-axis stress gauge 3 and Y-axis stress gauge 4 are aligned with the preset geological structure coordinates.

[0075] S400: After the mechanical anchoring of the X and Y axes is completed, the grouting material is injected through the grouting holes on the grouting holes on the grouting pipe 12 connected to the pre-reserved grouting pipe to the stress ring 9 assembly on the Z axis, so as to realize the rigid coupling of the monitoring instrument with the rock mass in the Z axis direction.

[0076] S500: Keep the monitor stationary, start the continuous acquisition mode, monitor and record the frequency and temperature data of the X, Y, and Z triaxial stress gauges in real time, and save the readings at this time as the initial zero point value of stress monitoring when the rate of change of the triaxial sensor readings is less than the preset threshold.

[0077] S600: Adjust the data acquisition instrument to long-term automatic monitoring mode, set the data acquisition time interval according to the monitoring requirements, automatically acquire the real-time frequency readings and temperature readings of the X, Y, and Z triaxial stress gauges, initialize the zero point value of the acquired real-time data and perform temperature correction, and then substitute it into the calibration coefficients of each stress gauge to calculate the increment or absolute amount of rock stress in the three orthogonal directions of X, Y, and Z, thereby obtaining complete data on the evolution of the three-dimensional stress field at the monitoring point over time.

[0078] Step S500 specifically includes the following steps:

[0079] S501: Set the monitor's operating mode to high-frequency sampling and start continuously collecting data according to preset parameters;

[0080] S502: At each stress gauge, the original vibrating wire frequency is corrected using temperature data to eliminate the influence of temperature drift on the reference value calibration.

[0081] S503: Enables sliding window data buffering, stores the frequency data after temperature compensation for the most recent N cycles into a queue, and continuously calculates the dispersion index within the data window through sliding window statistical analysis.

[0082] S504: Compares the statistical analysis results of the X, Y, and Z channels with the preset stress stability threshold in real time;

[0083] S505: When it is confirmed that the statistical indicators of all channels are below the stable threshold for M consecutive windows, calculate the average value of the data in the last stable window, and write it as the final zero point value into the non-volatile memory, and enter the long-term monitoring mode.

[0084] In step S502, Raw frequencies are collected at all times. and temperature Then, immediately call the temperature calibration coefficient. The compensated frequency, after eliminating the effect of temperature drift, was calculated. Specifically:

[0085] ,

[0086] in, To calibrate the reference temperature, Indicates the first Secondary sampling.

[0087] In step S503, during the sliding window data buffering process, whenever there is new data... Calculate the window when data enters. Standard deviation of N data points This is used to quantify the dispersion or instability of the current reading, specifically:

[0088] ,

[0089] in, window A single frequency data point within, window The arithmetic mean of N data points.

[0090] In step S504, multi-channel stability is compared in each... At any given time, simultaneously obtain the window standard deviations of the X, Y, and Z channels. And compare them with a preset frequency stability threshold. A comparison is performed. The current window is only considered when the stability of all three channels meets the condition. Only then is it marked as a stable state.

[0091] In step S505, the overall stability status of the three channels is continuously monitored. When a stable state is detected for M consecutive cycles, it is determined that the rock mass stress has reached initial equilibrium, and the last stability window is immediately calculated. Arithmetic mean of N data points This will be used as the final reference frequency. Write to memory and automatically switch to long-term monitoring mode.

[0092] Step S600 specifically includes the following steps:

[0093] S601: Runs long-interval polling scheduling, wakes up the stress meter and collects data according to the set steady-state interval. This is the system's baseline operating power consumption mode.

[0094] S602: After each data acquisition, a multi-step data conversion is performed, sequentially completing temperature compensation, reference frequency subtraction, and stress value conversion by calling calibration coefficients;

[0095] S603: Compare the calculated new stress value with the stress value of the previous steady-state cycle, calculate the rate of change, and compare it with the preset event trigger threshold.

[0096] S604: Once it is confirmed that the stress change rate of any channel exceeds the limit, immediately execute finite state machine control to switch the system state from steady-state inspection mode to high-frequency event capture mode, and simultaneously adjust the sampling interval to high frequency;

[0097] S605: In high-frequency mode, monitor the stress change rate of the high-frequency data stream. When the change rate falls back below the safety threshold and remains stable for a preset period of time, the system automatically degrades and returns to steady-state inspection mode.

[0098] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-dimensional in-situ rock stress monitoring instrument for underground rock strata, characterized in that, It includes horizontally arranged X-axis stress ring (1), Y-axis stress ring (2) and Z-axis stress ring (9); The X-axis stress ring (1) and the Y-axis stress ring (2) are provided with a circular cavity at their center. The X-axis stress ring (1) is provided with an X-axis stress gauge (3) and the Y-axis stress ring (2) is provided with a Y-axis stress gauge (4). The X-axis stress gauge (3) and the Y-axis stress gauge (4) are both horizontally arranged and fixed along the X and Y axes, respectively. The X-axis stress ring (1) and Y-axis stress ring (2) are stacked and a gap is reserved between them. After they are stacked, a connecting ring (7) is provided at the top. A connecting pipe (8) is provided at the top of the connecting ring (7). The Z-axis stress ring (9) is located at the top of the connecting pipe (8). It is vertically set and has a circular cavity in the center. The Z-axis stress ring (9) has a Z-axis stress gauge (10) inside the circular cavity. The Z-axis stress gauge (10) is vertically set and fixed along the Z-axis direction to measure the rock stress in three directions. The Z-axis stress ring (9) is provided with a bearing plate (11) on both the upper and lower sides, and a perforated tube (12) is connected to both the upper and lower bearing plates (11). The flower tube (12) is a hollow tube with holes on its surface, which are reserved for grouting. The flower tube (12) is sleeved with the connecting tube (8) to form a vertical connection with the X-axis stress ring (1) and the Y-axis stress ring (2); The extension line of the Z-axis stress gauge (10) coincides with the central axis of the X-axis stress ring (1) and the Y-axis stress ring (2); The X-axis stress gauge (3), Y-axis stress gauge (4) and Z-axis stress gauge (10) all use vibrating wire sensors to measure micro-strain; The X-axis stress ring (1), Y-axis stress ring (2) and Z-axis stress ring (9) are provided with polyurethane foam covering areas. The polyurethane foam covering areas are arranged in pairs, symmetrically arranged on both sides of the stress gauge length direction, and distributed at ninety degrees. The polyurethane foam covering areas are set within ±45° on both sides of the stress ring, so that they can deform freely in the space of the borehole and effectively shield the external force applied in the vertical direction. The connecting ring (7) and the connecting tube (8) are integrally formed, and a cavity is provided in the center of the connecting tube, which protrudes upward.

2. The three-dimensional in-situ rock stress monitoring instrument for underground rock strata according to claim 1, characterized in that, The X-axis stress ring (1), Y-axis stress ring (2) and connecting ring (7) are provided with multiple connecting holes along their circumference. Connecting screws (5) are provided in the connecting holes. The connecting screws (5) pass through the connecting holes of the X-axis stress ring (1), Y-axis stress ring (2) and connecting ring (7) at the same time, so that they are concentrically arranged. The connecting screw (5) is provided with a plurality of nuts (6), which are respectively located on both sides of the X-axis stress ring (1), the Y-axis stress ring (2) and the connecting ring (7), and are fixed at intervals.

3. The three-dimensional in-situ rock stress monitoring instrument for underground rock strata according to claim 2, characterized in that, The X-axis stress ring (1) and Y-axis stress ring (2) are provided with through mounting holes on their sides, and their top surfaces are also provided with fixing holes that extend into the mounting holes. The fixing holes are provided with adjustable fixing rods. The X-axis stress gauge (3) and Y-axis stress gauge (4) are respectively installed in the mounting holes of the X-axis stress ring (1) and Y-axis stress ring (2) in the inner ring, and the X-axis stress gauge (3) and Y-axis stress gauge (4) are fixed by tightening the fixing rod.

4. A method for in-situ monitoring of three-dimensional rock stress in underground rock strata, implemented using a three-dimensional rock stress in-situ monitoring instrument for underground rock strata as described in any one of claims 1-3, characterized in that, Specifically, the following steps are included: S100: At the target monitoring rock depth, drill precision mounting holes that match the outer diameter of the X-axis stress ring (1) and Y-axis stress ring (2) of the monitoring instrument, record the actual inclination angle and azimuth angle of the borehole axis, and select a clear structural surface or geographical orientation as a reference to mark its relative position at the borehole opening and inside the borehole. S200: On the surface working platform, the X-axis stress ring (1), Y-axis stress ring (2) and connecting ring (7) are stacked and concentrically fixed in sequence according to the drawing requirements by connecting screw (5) and nut (6), connecting pipe (8) is sleeved with flower pipe (12), and Z-axis stress ring (9) and bearing plate (11) are assembled. S300: Lower the assembled and verified monitoring instrument to the predetermined monitoring depth in the borehole. During the lowering process, refer to the reference orientation marked in step S100 and adjust the attitude of the monitoring instrument in real time to ensure that the measurement directions of the X-axis stress gauge (3) and the Y-axis stress gauge (4) are aligned with the preset geological structure coordinates. S400: After the mechanical anchoring of the X and Y axes is completed, the grouting material is injected through the grouting hole on the grouting hole on the grouting pipe (12) on the Z-axis stress ring (9) assembly via the reserved grouting pipe, so as to realize the rigid coupling of the monitoring instrument with the rock mass in the Z-axis direction. S500: Keep the monitor stationary, start the continuous acquisition mode, monitor and record the frequency and temperature data of the X, Y, and Z triaxial stress gauges in real time, and save the readings at this time as the initial zero point value of stress monitoring when the rate of change of the triaxial sensor readings is less than the preset threshold. S600: Adjust the data acquisition instrument to long-term automatic monitoring mode, set the data acquisition time interval according to the monitoring requirements, automatically acquire the real-time frequency readings and temperature readings of the X, Y, and Z triaxial stress gauges, initialize the zero point value of the acquired real-time data and perform temperature correction, and then substitute it into the calibration coefficients of each stress gauge to calculate the increment or absolute amount of rock stress in the three orthogonal directions of X, Y, and Z, thereby obtaining complete data on the evolution of the three-dimensional stress field at the monitoring point over time.

5. A method for in-situ monitoring of three-dimensional rock stress in underground strata according to claim 4, characterized in that, Step S500 specifically includes the following steps: S501: Set the monitor's operating mode to high-frequency sampling and start continuously collecting data according to preset parameters; S502: At each stress gauge, the original vibrating wire frequency is corrected using temperature data to eliminate the influence of temperature drift on the reference value calibration. S503: Enables sliding window data buffering, stores the frequency data after temperature compensation for the most recent N cycles into a queue, and continuously calculates the dispersion index within the data window through sliding window statistical analysis. S504: Compares the statistical analysis results of the X, Y, and Z channels with the preset stress stability threshold in real time; S505: When it is confirmed that the statistical indicators of all channels are below the stable threshold for M consecutive windows, calculate the average value of the data in the last stable window, and write it as the final zero point value into the non-volatile memory, and enter the long-term monitoring mode.

6. A method for in-situ monitoring of three-dimensional rock stress in underground strata according to claim 5, characterized in that, In step S502, Raw frequencies are collected at all times. and temperature Then, immediately call the temperature calibration coefficient. The compensated frequency, after eliminating the effect of temperature drift, was calculated. Specifically: ， in, To calibrate the reference temperature, Indicates the first Secondary sampling.

7. A method for in-situ monitoring of three-dimensional rock stress in underground strata according to claim 6, characterized in that, In step S503, during the sliding window data buffering process, whenever there is new data... Calculate the window when data enters. Standard deviation of N data points This is used to quantify the dispersion or instability of the current reading, specifically: ， in, window A single frequency data point within, window The arithmetic mean of N data points.

8. A method for in-situ monitoring of three-dimensional rock stress in underground strata according to claim 7, characterized in that, Step S600 specifically includes the following steps: S601: Runs long-interval polling scheduling, wakes up the stress meter and collects data according to the set steady-state interval. This is the system's baseline operating power consumption mode. S602: After each data acquisition, a multi-step data conversion is performed, sequentially completing temperature compensation, reference frequency subtraction, and stress value conversion by calling calibration coefficients; S603: Compare the calculated new stress value with the stress value of the previous steady-state cycle, calculate the rate of change, and compare it with the preset event trigger threshold. S604: Once it is confirmed that the stress change rate of any channel exceeds the limit, immediately execute finite state machine control to switch the system state from steady-state inspection mode to high-frequency event capture mode, and simultaneously adjust the sampling interval to high frequency; S605: In high-frequency mode, monitor the stress change rate of the high-frequency data stream. When the change rate falls back below the safety threshold and remains stable for a preset period of time, the system automatically degrades and returns to steady-state inspection mode.

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