Karst ground collapse comprehensive monitoring system

Abstract

The utility model discloses a karst ground subsidence comprehensive monitoring system belongs to ground subsidence monitoring early warning technical field. The comprehensive monitoring system includes underground water pressure monitoring system, soil mass deformation monitoring system and data acquisition system, wherein: underground water pressure monitoring system includes karst water monitoring hole and the first water pressure sensor of setting among them, fourth series water monitoring hole and the second water pressure sensor of setting among them, soil mass deformation monitoring system includes vertical optical fiber monitoring hole and the optical fiber sensor of setting among them, and data acquisition system with first water pressure sensor, second water pressure sensor and optical fiber sensor all electric connection. The utility model selects underground water as the inducing factor of ground subsidence, and simultaneously takes the underground soil mass as the monitoring object, builds the karst ground subsidence comprehensive monitoring system, and multiple monitoring means verifies each other, and is complementary to each other, can provide strong support for the early warning forecast work of karst ground subsidence disaster.

Description

Technical Field

[0001] This utility model relates to the field of ground subsidence monitoring and early warning technology, and in particular to a comprehensive monitoring system for karst ground subsidence. Background Technology

[0002] In recent years, karst ground subsidence has occurred frequently due to the influence of natural and human engineering activities. This subsidence is mainly caused by the leakage of overlying soil along the cavities of underlying soluble rock. Karst ground subsidence is characterized by its insidious and sudden occurrence. To monitor its development, it is necessary to select appropriate monitoring targets and methods, and to directly or indirectly reflect the development process of ground subsidence through dynamic changes.

[0003] Chinese patent application CN113776450B discloses a ground deformation monitoring system and method based on fiber optic technology. The system includes a fixed-point strain sensing optical cable, fiber Bragg grating thermometers, a lead optical cable, and a monitoring station. The fixed-point strain sensing optical cable is laid in a trench within the ground monitoring area and connected to the monitoring station located on the ground via the lead optical cable. Several fiber Bragg grating thermometers are installed at intervals along the fixed-point strain sensing optical cable. This ground deformation monitoring system, deployed on the ground surface, can only monitor karst ground collapses that are about to occur or have already occurred, and cannot be used for early warning and forecasting of karst ground collapse disasters. Utility Model Content

[0004] The purpose of this invention is to provide a comprehensive monitoring system for karst ground subsidence, addressing the existing technological status quo. By selecting groundwater as the inducing factor for ground subsidence and simultaneously using underground soil as the monitoring object, a comprehensive monitoring system for karst ground subsidence is established. Multiple monitoring methods are mutually verified and complementary, which can provide strong support for the early warning and forecasting of karst ground subsidence disasters.

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

[0006] A comprehensive monitoring system for karst ground subsidence includes a groundwater pressure monitoring system, a soil deformation monitoring system, and a data acquisition system;

[0007] The groundwater pressure monitoring system includes karst water monitoring holes and a first water pressure sensor installed therein, a Quaternary water monitoring hole and a second water pressure sensor installed therein. The karst water monitoring holes extend downward from the ground surface of the study area into the karst layer and pass through the karst fissure development zone or karst conduit. The Quaternary water monitoring holes extend downward from the ground surface of the study area to the bottom plate of the lowest aquifer of the Quaternary soil layer.

[0008] The soil deformation monitoring system includes a vertical fiber optic monitoring hole and a fiber optic sensor installed therein. The vertical fiber optic monitoring hole extends from the ground down into the karst layer, and the space between the fiber optic sensor and the hole wall of the vertical fiber optic monitoring hole is filled with backfill material.

[0009] The data acquisition system is electrically connected to the first water pressure sensor, the second water pressure sensor, and the fiber optic sensor.

[0010] Furthermore, the karst water monitoring wells are located at the boundaries and center of the collapse development zone within the study area, and are laid out along the direction of groundwater runoff.

[0011] Furthermore, the first water pressure sensor employs a fiber optic piezometer and a vibrating wire piezometer.

[0012] Furthermore, the second water pressure sensor employs a fiber Bragg grating piezometer.

[0013] Furthermore, the fiber optic sensor employs a distributed strain sensing optical cable.

[0014] Furthermore, the karst water monitoring well and the Quaternary water monitoring well are existing machine-drilled wells, and the vertical fiber optic monitoring well is a drilled well.

[0015] Furthermore, PE or PPR protective pipes are embedded in both the karst water monitoring hole and the Quaternary water monitoring hole.

[0016] Furthermore, the backfill material includes cement, sand and gravel, clay balls and an early-strength agent, wherein the sand and gravel is a mixture of medium sand, coarse sand and gravel.

[0017] The beneficial effects of this utility model are as follows:

[0018] This invention selects groundwater as the inducing factor for ground subsidence and uses underground soil as the monitoring object to build a comprehensive monitoring system for karst ground subsidence. It integrates monitoring of karst water pressure, Quaternary water pressure, and soil deformation in the subsidence development area of ​​the study area. The multiple monitoring methods verify and complement each other, which can provide strong support for the early warning and forecasting of karst ground subsidence disasters. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a comprehensive monitoring system for karst ground subsidence according to the present invention;

[0020] Figure 2 A structural schematic diagram showing the stage of deformation of potential karst ground collapse hazards during soil deformation monitoring and early warning.

[0021] Labeling instructions: 1. Karst water monitoring hole, 2. First water pressure sensor, 3. Quaternary water monitoring hole, 4. Second water pressure sensor, 5. Vertical fiber optic monitoring hole, 6. Fiber optic sensor. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific examples described herein are merely illustrative of the present utility model and are not intended to limit the scope of the present utility model.

[0023] Please see Figure 1 As shown, a comprehensive monitoring system for karst ground subsidence includes a groundwater pressure monitoring system, a soil deformation monitoring system, and a data acquisition system.

[0024] The groundwater pressure monitoring system includes a karst water monitoring well 1 and a first water pressure sensor 2 installed therein, a Quaternary water monitoring well 3 and a second water pressure sensor 4 installed therein. The karst water monitoring well 1 extends downward from the ground surface of the study area into the karst layer and passes through the karst fissure development zone or karst conduit. The Quaternary water monitoring well 3 extends downward from the ground surface of the study area to the bottom plate of the lowest aquifer of the Quaternary soil layer.

[0025] Specifically, karst water monitoring well 1 is located at the boundary and center of the collapse development zone within the study area and is laid out along the direction of groundwater flow. Karst water monitoring well 1 and Quaternary water monitoring well 3 are existing wells or drilling holes, and are equipped with PE or PPR protective pipes. The first water pressure sensor 2 adopts a fiber optic piezometer and a vibrating wire piezometer, and the second water pressure sensor 4 adopts a fiber optic piezometer.

[0026] More specifically, the construction steps for a groundwater pressure monitoring system are as follows:

[0027] Ten sets of groundwater pressure monitoring points (wells) with fiber optic piezometers were installed, arranged in pairs, to monitor the pressure of karst water and Quaternary water respectively; 15 groundwater pressure monitoring points (wells) with vibrating wire piezometers were installed, all monitoring the pressure of karst water. The distance between two groundwater pressure monitoring points (wells) with fiber optic piezometers or vibrating wire piezometers should be between 300 and 500 meters.

[0028] The designed depth of Quaternary water monitoring well 3 is a minimum of 20m, a maximum of approximately 40m, and an average of 30m. The designed depth of karst water monitoring well 1 is a minimum of 40m, a maximum of approximately 60m, and an average of 50m. Adjustments may be made during actual construction based on site geological conditions.

[0029] After the groundwater pressure monitoring point (hole) is drilled to completion, a PE or PPR protective pipe should be placed inside the casing. The diameter of the protective pipe should be no less than 70mm. It should be placed to the bottom of the hole. For karst water monitoring, the part below the bedrock surface 1 to 2m should be a perforated pipe with a diameter of 2 to 5mm, in a quincunx pattern. The vertical spacing between holes should be 30 to 50mm. Note that the protective pipe should be kept vertical and should not be tilted.

[0030] After the protective casing is placed to the required depth, for bedrock boreholes: tie kelp to the upper part of the PE or PPR protective casing in the aquifer section, fill with water, and after the kelp expands, slowly and evenly pour the prepared clay to the ground or pour cement mortar to the ground between the casing and the protective casing; for Quaternary soil boreholes: pour coarse sand around the PE or PPR protective casing until it reaches above the top surface of the uppermost aquifer before pouring clay or cement mortar to seal it.

[0031] While pulling out the casing, use the drill rod to hold down the protective casing to prevent it from being pulled out, and the casing should be pulled out slowly. When sealing the orifice of PE or PPR protective casing, use a piece of thick paper with a diameter larger than the protective casing to be placed 15cm below the pipe opening, and inject expanding foam into the pipe opening for sealing.

[0032] The soil deformation monitoring system includes a vertical fiber optic monitoring hole 5 and a fiber optic sensor 6 installed therein. The vertical fiber optic monitoring hole 5 extends downward from the ground into the karst layer, and the space between the fiber optic sensor 6 and the hole wall of the vertical fiber optic monitoring hole 5 is filled with backfill material.

[0033] Specifically, fiber optic sensor 6 uses a distributed strain sensing cable with a fixed point spacing of 2m, a monitoring accuracy of 0.02mm / 2m, and a monitoring range of 40mm / 2m. The vertical fiber optic deformation monitoring process is as follows: When an abnormal break occurs, it indicates that the soil near the cable has moved, the cable has been cut (pulled apart), and a karst cave has formed. Furthermore, if there are abrupt changes in the results of three comparisons, the existence and development speed of the karst cave can be determined. Vertical fiber optic monitoring hole 5 is a drilled hole. The backfill material includes cement, sand and gravel, clay balls, and an early-strength agent. The sand and gravel is a mixture of medium sand, coarse sand, and gravel.

[0034] More specifically, the construction steps for a soil deformation monitoring system are as follows:

[0035] Before deploying fiber optic sensor 6, a 2m spacing ground settlement-specific fixed-point strain sensing fiber optic cable and a metal-based cable-like strain sensing fiber optic cable are connected in series to form a loop. This is used to check if data can be collected. The cable is then connected to the counterweight guide head and lowered into the borehole. Jumpers are connected to both ends of the lead wire at the borehole opening to the corresponding fiber optic strain demodulator for monitoring. The specific construction steps are as follows:

[0036] (1) In order to ensure the safe placement of the fiber optic sensor 6 into the borehole, the borehole diameter should be greater than 110 mm. During the drilling process, the mud density should be moderate to ensure the stability of the borehole and prevent large collapses. After the borehole is formed, the borehole should be swept once and washed with clean water.

[0037] (2) Connecting the guide head: Lay out a sufficient length of fixed-point strain sensing optical cable and metal-based cable strain sensing optical cable in the area near the borehole, and thread the two optical cables into the counterweight guide head.

[0038] (3) Cable laying reel installation: Install cable laying devices on both sides of the drilling tower and install fiber optic lead wires and optical cable winding reels.

[0039] (4) Lowering the optical cable: Place the fixed metal-based strain sensing optical cable, the fixed-point strain sensing optical cable, and the counterweight guide head into the borehole. Since the borehole depth does not exceed 50m, the counterweight guide head does not require special treatment and can be lowered directly for installation. During lowering, control the lowering speed by pulling the load-bearing steel wire rope, while simultaneously pulling the optical cable to ensure it is straight but avoiding excessive stress on the optical cable to prevent damage, until the guide head is lowered to the bottom of the borehole.

[0040] (5) Temporary fixing of optical fiber: When the counterweight guide head is lowered to the bottom, reserve a sufficient length of optical fiber lead wire and temporarily wrap and fix the optical fiber lead wire outside the borehole to the drilling machine. The selected wrapping and fixing point should be a round rod with a diameter greater than 6cm.

[0041] (6) Fiber Optic Field Testing: All fiber optic sensors 6 were tested using testing instruments, and the field test results were recorded. Based on the field test results, the tension of the fixed-point strain sensing fiber optic cable and the metal-based cable-like fiber optic cable was adjusted by pulling them. The fiber optic cable adjustment was completed when the test curve no longer showed significant changes. Then, all fiber optic cables were fixed again.

[0042] (7) Borehole sealing: After the optical cable is re-fixed, the borehole is backfilled and sealed with sealing material. The sealing material is a grouting material with a grout mixing ratio determined according to the soil properties and the properties of the karst filling material. The grouting adopts a bottom-up segmented grouting method, and the process is as follows: In the intact bedrock section at the bottom of the borehole, pure cement grout is used for grouting according to the grouting sequence of the grouting process, and attention is paid to the differences in grout; during the grouting process, the grouting speed is controlled, and the hole depth is measured in time with a 3~5cm diameter plumb bob, and the grouting volume and grouting length are checked to avoid voids, incomplete backfilling, etc. The sealing and backfilling should generally be carried out in two days. After the backfilling is completed on the first day, wait for the sealing material to settle. On the second day, check the borehole again and carry out a second backfilling. Cement mortar is used for backfilling 2m below the borehole opening.

[0043] (8) Re-fixing of optical cable: After the borehole backfilling is completed, drive in a fixing pile or build a support crossbar at the borehole opening to fix the optical cable at the opening. Remove the optical cable wrapped around the drilling rig and wrap it around and fix it to the fixing pile or support crossbar. The fixed-point strain sensing optical cable and the metal-based cable optical cable should be tightened to prevent the optical cable from shrinking during the sealing material consolidation process, which would affect the subsequent testing of the optical fiber. The fixing time for the optical cable at the borehole opening is more than 2 to 3 months. During this period, the consolidation and coupling between the sealing material and the optical cable in the borehole is basically completed.

[0044] (9) Wellhead protection: After backfilling the borehole, a wellhead protection device is built above the borehole location. The distributed sensing optical cable leads and other installed wires are connected to the protection box, and the protection box is built into the wellhead protection device for protection.

[0045] (10) Precautions for backfill materials:

[0046] Backfill material should meet three conditions: First, the strength of the backfill material after consolidation should be close to that of the soil being monitored so that the deformation of the soil can be fully transmitted to the sensing optical fiber through the backfill material. If the strength is too high, small deformations of the soil cannot be detected, and if the strength is too low, the monitoring data will be inaccurate. Second, the backfill material should be highly stable, convenient and quick to install, and easy to construct. Third, the backfill material itself should not damage the sensing optical fiber and should not break the optical fiber during the backfilling process.

[0047] Based on the above three characteristics, and referring to engineering experience and indoor tests, a grouting material was selected as the backfill material, consisting of cement, sand and gravel (a mixture of medium sand, coarse sand, and gravel), and clay balls. The mixing ratio of the grout was determined according to the soil layer properties and the properties of the karst cave filling material. The sand and gravel mixture was a mixture of medium sand, coarse sand, and gravel; the main components of the sand and gravel changed accordingly with different drilling depths. The clay balls were almond-shaped, with a diameter of approximately 15mm. The mechanism of action is as follows: the medium sand, coarse sand, and gravel form a skeletal structure. After absorbing water, the clay balls expand in volume, squeezing the sand and gravel outwards, allowing the backfill material to better fill the cracks or fissures, thus improving the coupling effect between the backfill coupling material and the soil, as well as between the backfill coupling material and the sensor.

[0048] The data acquisition system is electrically connected to the first water pressure sensor 2, the second water pressure sensor 4, and the fiber optic sensor 6.

[0049] Specifically, the data acquisition system corresponding to the first water pressure sensor 2 and the second water pressure sensor 4 adopts an automated data acquisition and transmission system. According to the continuous monitoring data of multiple engineering activities, the sudden changes in karst groundwater pressure are mostly completed in a short period of time. If the monitoring frequency is greater than 1 hour, it is difficult to detect the sudden changes. Therefore, the monitoring interval for karst system groundwater pressure is required to be 20 minutes. The data acquisition system corresponding to the fiber optic sensor 6 adopts manual data acquisition, with a monitoring frequency of once per month. During the flood season, rainy season, and when abnormal situations occur, the monitoring frequency must be increased.

[0050] The comprehensive early warning and forecasting of karst ground collapse based on the above-mentioned comprehensive monitoring system includes the following steps:

[0051] Groundwater level monitoring and early warning, specifically:

[0052] As the soil cavity continues to evolve and expand, the collapsing soil mass is in a state of limit equilibrium at the point of imminent collapse. The resistance force F generated by the soil mass is equal to the inducing force of the soil mass, which is the sum of the soil mass's weight G and the suction force P generated by the drop in water level.

[0053] The formula for calculating the soil's resistance to collapse, F, is as follows:

[0054]

[0055] The formula for calculating the weight G of the soil is as follows:

[0056]

[0057] The formula for calculating the suction force P caused by the drop in water level is as follows:

[0058]

[0059] Therefore, the groundwater level fluctuation can be obtained. The calculation formula is as follows:

[0060]

[0061] In the formula: h is the collapse thickness, and d is the diameter of the collapse body. Let θ be the angle of internal friction and c be the cohesive force. For the density of soil, For the specific gravity of water, This is the coefficient of lateral pressure on the soil.

[0062] Comparison of groundwater level fluctuations Compared with the preset critical change value of groundwater level, when the groundwater level fluctuation... If the groundwater level change is less than the preset critical change value, no warning will be issued. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) An early warning will be issued if the groundwater level change is greater than or equal to a preset critical change value.

[0063] Soil deformation monitoring and early warning, specifically:

[0064] Based on monitoring data from the soil deformation monitoring system, the stage of deformation at which a potential karst land collapse hazard is located is determined, and an early warning is issued based on this stage. The stages of deformation at which a potential karst land collapse hazard is located include:

[0065] Localized sand layer disturbance stage;

[0066] The stage of intense disturbance of the sand layer and deceleration deformation of the clay layer;

[0067] The stage of clay layer erosion and uniform deformation;

[0068] The clay layer undergoes accelerated deformation and reaches the critical collapse stage.

[0069] The principle of comprehensive early warning and forecasting for karst ground subsidence is explained below:

[0070] Groundwater level changes play a crucial role in the incubation and occurrence of karst landslides, primarily through rapid changes in groundwater level and hydraulic gradient. The hydraulic gradient's impact on karst landslides is mainly manifested through erosion and seepage deformation. When the hydraulic gradient exceeds the critical value for soil seepage deformation, soil loss occurs, leading to the formation of initial soil cavities.

[0071] For example, the first terrace of a certain study area is the main subsidence area, which is dominated by a binary structure of clay above and sand below. According to the results of physical model test, the critical hydraulic gradient for seepage deformation (undercutting) of the lower sand layer is 0.31~0.73, and the critical hydraulic gradient for seepage deformation of the clay layer is 0.79~6.95.

[0072] The groundwater level monitoring and early warning method was used to calculate the karst ground subsidence that had occurred in the first terrace of the study area. The calculated groundwater level fluctuation at each subsidence point was 2-9m, showing significant variation. Specifically, the calculated values ​​were smaller for subsidence pits with larger diameters and thinner thicknesses, and vice versa. Based on the average diameter, thickness, and groundwater level variation characteristics of the subsidence pits in the study area, and referring to the numerical simulation results showing a critical groundwater level drop of 5.26m / d, a groundwater level fluctuation of 4-6m / d was chosen as the critical groundwater level change value for karst ground subsidence monitoring, early warning, and forecasting.

[0073] Based on the physical model test results of the first-level terrace binary structure collapse in this study area, due to the variable groundwater, when the hydraulic gradient of the upper Quaternary groundwater and the underlying karst groundwater reaches the critical value of the bottom sand layer, the sand layer will flow into the karst cavities below, forming initial soil cavities, and the deformation is slow (e.g., ...). Figure 2 (As shown in part a); when the hydraulic gradient continues to increase, it will cause severe disturbance and loss of the sand layer until it reaches the bottom of the upper Quaternary clay layer (as shown in part a). Figure 2 (As shown in part b); when the hydraulic gradient exceeds the critical value of the clay layer, the bottom of the clay layer will continue to erode, deforming slowly and at a relatively uniform rate (as shown in part b). Figure 2 (As shown in part c); as the clay cavities continue to expand, the soil deformation accelerates before collapse, until the entire layer collapses (as shown in part c). Figure 2 (As shown in part d in the diagram). During the clay layer erosion and uniform deformation stage and the clay layer accelerated deformation and critical collapse stage, the surface soil often exhibits certain precursory settlement deformations, such as cracks.

[0074] Therefore, monitoring changes in groundwater levels can reveal the formation and evolution of soil cavities in the early stages of karst ground subsidence, thus indirectly serving as a monitoring and early warning system. When human engineering activities cause groundwater monitoring indicators to reach warning levels without soil deformation, the project construction party can be notified in advance, and preventative advice and emergency plans can be provided to avoid subsidence and its resulting damage.

[0075] A comprehensive early warning and forecasting mechanism will be established by combining groundwater pressure monitoring and soil deformation monitoring, as detailed below:

[0076] (a) Early warning methods

[0077] Monitoring and early warning of karst ground subsidence mainly rely on monitoring data obtained from various monitoring factors in the monitoring network and macroscopic ground inspections. The early warning process can be divided into two steps: single-factor early warning from the monitoring system and manual early warning.

[0078] 1. Single-factor early warning system for monitoring

[0079] The single-factor early warning system is automatically generated by the karst ground collapse monitoring and early warning system. After acquiring monitoring data such as groundwater and soil deformation, the system draws various analytical curves based on built-in models and performs statistical calculations. When the change in the monitoring data of a certain factor reaches the early warning index, the system issues an early warning for that factor and sends the warning information to system administrators and relevant professionals for further analysis and confirmation.

[0080] 2. Manual early warning

[0081] Upon receiving an early warning message from the system, system administrators or relevant professionals should immediately notify the relevant responsible persons in their unit. The relevant responsible departments of the unit should then organize relevant technical personnel to conduct an on-site investigation and comprehensively analyze and discuss the monitoring data and investigation findings. If it is necessary to issue an early warning message, the relevant natural resources authorities should be notified immediately, and a relevant situation report should be prepared.

[0082] (II) Classification of Early Warning Levels

[0083] According to the provisions of the "Emergency Response Law of the People's Republic of China" regarding early warning levels, the early warning levels for karst ground collapse disasters are divided into four levels based on the development stage of deformation and failure, deformation rate, and probability of occurrence: Attention Level, Warning Level, Alert Level, and Alarm Level. These four levels are respectively indicated by blue, yellow, orange, and red, as shown in Table 1.

[0084] Table 1:

[0085] Warning level Early warning criteria Level 1 The deformation posing a risk of karst ground subsidence has entered an accelerated phase, with various precursory deformation characteristics becoming increasingly apparent. The probability of a large-scale subsidence occurring in the short term is very high, warranting an alert level, indicated in red, and designated as a red warning. Level 2 The deformation of the karst ground subsidence hazard has entered the stage of uniform deformation of the upper clay layer, exhibiting certain macroscopic precursor deformation characteristics. The probability of a large-scale subsidence occurring in the short term is high, classifying it as a warning level, indicated by orange, and thus designated as an orange alert. Level 3 The karst ground subsidence hazard has entered the early stage of severe disturbance of the bottom sand layer, exhibiting obvious deformation characteristics but lacking precursory surface deformation features. The probability of a large-scale subsidence occurring in the short term is relatively high, classifying it as a warning level, indicated by yellow, and designated as a yellow alert. Level 4 When the changes in groundwater monitoring data reach or exceed the warning indicators, or when the karst ground subsidence hazard is identified and the initial soil cave formation stage is observed with signs of deformation but slow deformation, the likelihood of a subsidence hazard occurring in the short term is low. This level of alert is indicated in blue and designated as a blue alert.

[0086] (III) Identification and Issuance of Early Warnings

[0087] 1. Identification and Issuance of Blue Alerts

[0088] The blue alert (attention level) level is determined by the monitoring unit after discussion among relevant technical personnel, and reported to the relevant natural resources bureau. The natural resources bureau may then report to the district / county people's government. Upon entering a blue alert phase, a disaster prevention plan for the karst ground subsidence disaster site should be prepared. Upon entering a yellow alert phase, the disaster prevention plan should be adjusted according to the specific deformation situation. Blue and yellow alerts are not publicly announced.

[0089] 2. Identification and Issuance of Yellow, Orange and Red Alerts

[0090] The issuance of yellow, orange, and red alerts requires a joint consultation meeting. First, an expert group conducts a technical consultation. Following the technical consultation, the expert group immediately submits its monitoring and early warning technical consultation opinion, making a technical determination on whether to enter an orange (or red) alert level and proposing corresponding expert group recommendations. Based on the expert group's opinion, the joint meeting conducts an administrative consultation on the early warning, forming minutes of the administrative consultation meeting, which are then submitted to the superior competent authority for approval before being released.

[0091] In summary, this invention selects groundwater as the inducing factor for ground subsidence and uses underground soil as the monitoring object to build a comprehensive monitoring system for karst ground subsidence. It integrates monitoring of karst water pressure, Quaternary water pressure, and soil deformation in the subsidence development area of ​​the study area. The multiple monitoring methods verify and complement each other, providing strong support for the early warning and forecasting of karst ground subsidence disasters.

[0092] This utility model is not limited to the specific embodiments described above. Those skilled in the art can implement this utility model using various other specific embodiments based on the content disclosed in this utility model. Therefore, any design that adopts the design structure and concept of this utility model and makes some simple changes or modifications falls within the protection scope of this utility model.

Claims

1. A comprehensive monitoring system for karst ground subsidence, characterized in that: This includes a groundwater pressure monitoring system, a soil deformation monitoring system, and a data acquisition system; The groundwater pressure monitoring system includes karst water monitoring holes and a first water pressure sensor installed therein, a Quaternary water monitoring hole and a second water pressure sensor installed therein. The karst water monitoring holes extend downward from the ground surface of the study area into the karst layer and pass through the karst fissure development zone or karst conduit. The Quaternary water monitoring holes extend downward from the ground surface of the study area to the bottom plate of the lowest aquifer of the Quaternary soil layer. The soil deformation monitoring system includes a vertical fiber optic monitoring hole and a fiber optic sensor installed therein. The vertical fiber optic monitoring hole extends from the ground down into the karst layer, and the space between the fiber optic sensor and the hole wall of the vertical fiber optic monitoring hole is filled with backfill material. The data acquisition system is electrically connected to the first water pressure sensor, the second water pressure sensor, and the fiber optic sensor.

2. The comprehensive monitoring system for karst ground subsidence according to claim 1, characterized in that: The karst water monitoring wells are located at the boundaries and center of the collapse development zone within the study area, and are laid out along the direction of groundwater runoff.

3. The comprehensive monitoring system for karst ground subsidence according to claim 1, characterized in that: The first water pressure sensor uses a fiber optic piezometer and a vibrating wire piezometer.

4. The comprehensive monitoring system for karst ground subsidence according to claim 1, characterized in that: The second water pressure sensor is a fiber optic piezometer.

5. The comprehensive monitoring system for karst ground subsidence according to claim 1, characterized in that: The fiber optic sensor uses a distributed strain sensing optical cable.

6. A comprehensive monitoring system for karst ground subsidence according to any one of claims 1 to 5, characterized in that: The karst water monitoring wells and Quaternary water monitoring wells are existing machine-drilled wells, while the vertical fiber optic monitoring wells are drilled wells.

7. The comprehensive monitoring system for karst ground subsidence according to claim 6, characterized in that: Both the karst water monitoring well and the Quaternary water monitoring well are equipped with PE or PPR protective pipes.

8. The comprehensive monitoring system for karst ground subsidence according to claim 6, characterized in that: The backfill material includes cement, sand and gravel, clay balls and early strength agent, and the sand and gravel is a mixture of medium sand, coarse sand and gravel.

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