Multistage-in-one-hole pore water pressure observation device and mounting method therefor

Abstract

A multistage-in-one-hole pore water pressure observation device, comprising: a plurality of digital piezometer probe assemblies (10) arranged in a monitoring hole (1) from bottom to top, an inter-stage hydraulic isolation cylinder assembly (2) connected between each two adjacent digital piezometer probe assemblies (10), and watertight joint assemblies (30) used for connecting adjacent digital piezometer probe assemblies (10) and inter-stage hydraulic isolation cylinder assemblies (2). Each digital piezometer probe assembly (10) comprises a hollow water-permeable cylinder (11), a pore water pressure meter assembly (12) arranged in the water-permeable cylinder (11), a high-permeability material (13) filled in a gap between an inner wall of the water-permeable cylinder (11) and the pore water pressure meter assembly (12), and a water-permeable geotextile (14) wrapping the high-permeability material (13). Multi-core cables (40) are electrically connected between the adjacent pore water pressure meter assemblies (12). The device has the characteristics of integrated design, prefabrication and installation of the pore water pressure monitoring apparatuses and the backfill material, thereby simplifying an on-site installation process and reducing monitoring costs. Also provided is a mounting method for the multistage-in-one-hole pore water pressure observation device.

Description

A multi-stage pore water pressure monitoring device with the same borehole and its installation method Technical Field

[0001] This application belongs to the technical field of pore water pressure monitoring, specifically relating to a multi-stage pore water pressure monitoring device with the same pore and its installation method. Background Technology

[0002] Pore ​​water pressure is the pressure exerted by water present in soil, rock, or other porous media, and it has a significant impact on the mechanical properties and stability of soil and rock masses. Therefore, pore water pressure monitoring has become a major monitoring component in geotechnical engineering, providing crucial data support for the analysis of soil and rock deformation and stability.

[0003] Currently, the specialized instrument for observing pore water pressure is the pore water pressure gauge, also known as a piezometer. In use, a borehole needs to be drilled, and the piezometer needs to be installed and buried in the borehole. The quality of the piezometer's installation directly affects the subsequent observation results.

[0004] To more accurately understand the variation of pore water pressure with depth within soil and rock masses, many engineering projects require the installation of multiple (i.e., multi-stage) piezometers at different soil depths. Compared to the traditional single-hole, single-point arrangement, the multi-stage arrangement within the same borehole (i.e., densely installing multiple piezometers within a single borehole) not only effectively reduces the total number of boreholes and saves project costs, but more importantly, all observation data originates from the same monitoring profile, resulting in greater correlation and consistency between data from different observation points.

[0005] When implementing a multi-stage arrangement of piezometers within the same borehole, it is first necessary to ensure lateral connectivity between the piezometers at each depth and the corresponding soil and rock layers. This allows the pore water pressure in the soil and rock layers to be transmitted to the piezometers with minimal pressure gradient loss. Current methods involve filling the piezometers with sand, which effectively transmits pore water pressure through contact between the sand particles and the borehole walls. Secondly, since the pore water pressure varies at different depths, vertical isolation between the piezometers is also crucial to prevent cross-contamination. Therefore, materials such as clay are filled between the upper and lower piezometers, and a step-by-step, layered isolation approach is used to ensure that each piezometer operates independently.

[0006] Traditional step-by-step, layered installation methods are complex, cumbersome, and time-consuming. Furthermore, when encountering complex geological conditions such as deep-hole operations or soft soil layers, the precise application of backfill material becomes particularly difficult to control. This directly leads to the difficulty in constructing an effective permeable filter layer around the pore water pressure gauge probe, and problems with sealing or inadequate sealing between the upper and lower pore water pressure gauge probes, thus affecting installation quality and compromising the accuracy of measurement data. Summary of the Invention

[0007] In view of this, this application provides a multi-stage pore water pressure observation device and its installation method, which simplifies the complex installation and burial process of multi-stage pore water pressure gauges, shortens the operation time, and solves the problem of limited pore water pressure data measurement accuracy caused by the difficulty of backfill material placement.

[0008] In a first aspect, this application provides a multi-stage pore water pressure monitoring device with the same borehole, which adopts the following technical solution:

[0009] A multi-stage pore water pressure monitoring device with the same hole includes: a plurality of digital osmosis probe assemblies arranged at intervals from bottom to top in the monitoring hole; a staged infiltration cylinder assembly connected between two adjacent digital osmosis probe assemblies; and a watertight connector assembly for connecting the adjacent digital osmosis probe assemblies and the staged infiltration cylinder assembly.

[0010] Each of the digital osmosis probe components includes a long, hollow permeable cylinder, a pore water pressure gauge component disposed inside the permeable cylinder, a highly permeable material filling the gap between the inner wall of the permeable cylinder and the pore water pressure gauge component, and a permeable geotextile wrapping the highly permeable material.

[0011] The adjacent pore water pressure gauge assemblies are electrically connected by a multi-core cable, which passes through the interstage percolation cylinder assembly between the adjacent pore water pressure gauge assemblies.

[0012] The multi-stage pore water pressure monitoring device provided in this application can be used to arrange multi-stage digital pore pressure probe components in a single borehole at a high density, such as arranging one digital pore pressure probe component every 3 meters. This can not only effectively reduce the number of monitoring boreholes and save project costs, but also ensure that all observation data originate from the same monitoring profile, making the observation data from different observation points more correlated and consistent.

[0013] Traditional pore water pressure gauges use a split-wire system, requiring an independent cable for each probe. Installing n probes necessitates n cables, resulting in high costs and cumbersome installation. This application utilizes a digital pore water pressure probe assembly with a bus design, allowing all probes within a single borehole to share a single multi-core cable (two cores for power supply and two cores for data transmission), significantly reducing observation costs and simplifying the installation process.

[0014] Optionally, the staged permeable tube assembly includes one permeable tube or multiple permeable tubes connected in series;

[0015] Each of the aforementioned seepage-proof cylinders includes a central tube and a grid cage arranged concentrically from the inside to the outside, with the space between the central tube and the grid cage filled with a water-absorbing and expanding material wrapped in a water-soluble film;

[0016] The multi-core cable extends from both ends of the central tube and connects to two adjacent pore water pressure gauge assemblies respectively.

[0017] Optionally, the side wall of the permeable cylinder is provided with a plurality of permeable holes, and the upper and lower ends of the permeable cylinder are provided with cylinder caps, and each cylinder cap is provided with a connector pipe for connecting one end of the watertight connector assembly.

[0018] The multi-core cable connected to the pore water pressure gauge assembly passes through the connector tube and extends into the stage interval seepage cylinder assembly. The inner wall of the connector tube is provided with potting compound.

[0019] Optionally, the watertight connector assembly includes a threaded sleeve with openings at the top and bottom and a silicone ring gasket;

[0020] The threaded sleeve is provided with a horizontal plate that divides it into upper and lower chambers, and the horizontal plate has a central hole for the multi-core cable to pass through.

[0021] The silicone ring gaskets are laid on both sides of the horizontal plate, and the chambers on both sides of the horizontal plate are used for threaded connection of the connector pipe and the staged permeation cylinder assembly.

[0022] Optionally, the pore water pressure gauge assembly includes an encapsulation shell, a small lock nut, a large lock nut, a data acquisition circuit board, a pore water pressure sensor and its signal line electrically connected to the data acquisition circuit board, and a probe multi-core cable electrically connected to the data acquisition circuit board.

[0023] The multi-core cable of the probe, the signal line, and the acquisition circuit board are all located inside the encapsulation shell. The small lock nut is used to block the signal line from extending out of the encapsulation shell, and the large lock nut is used to block the multi-core cable of the probe from extending out of the encapsulation shell.

[0024] Optionally, the acquisition circuit board includes:

[0025] MCU microcontroller with integrated storage module;

[0026] The excitation frequency sweep module, signal processing module, and temperature acquisition module are all electrically connected to the MCU microcontroller.

[0027] The bus communication module and power supply module are electrically connected to the MCU microcontroller.

[0028] The pore water pressure sensor is electrically connected to the excitation frequency sweep module, the signal processing module, and the temperature acquisition module.

[0029] Optionally, the highly permeable material is medium-coarse sand, the water-absorbing and swelling material is water-absorbing and swelling resin, and the outer sealing coating of the acquisition circuit board is epoxy resin.

[0030] Optionally, the plurality of digital osmotic pressure probe assemblies, the diaphragm cylinder, and the watertight connector assembly are all prefabricated as an integrated unit.

[0031] Optionally, when the staged permeable tube assembly includes multiple permeable tubes connected in series, the watertight joint assembly is connected between each permeable tube.

[0032] The watertight connector assembly also includes a fastening screw, and the threaded sleeve has a threaded hole corresponding to the fastening screw.

[0033] Secondly, this application provides an installation method for a multi-stage pore water pressure monitoring device with the same borehole.

[0034] In summary, this application includes at least one of the following beneficial technical effects:

[0035] This application includes at least one of the following beneficial technical effects:

[0036] This application integrates backfill material into the fabrication process of the pore water pressure monitoring device, achieving integrated design, fabrication, and installation of the monitoring device and backfill material. Specifically, a coarse sand cushion layer is prefabricated directly inside the permeable cylinder, while a novel material combination of water-absorbing and expanding material and a water-soluble film is introduced and formed within the cavity of the permeable cylinder, replacing traditional bentonite or highly disintegrating clay balls to form a highly efficient sealing layer. This design concept changes the traditional construction mode, eliminating the need for additional backfill material during on-site installation and greatly simplifying the installation process. More importantly, the factory-prepared model ensures standardized and regulated installation, effectively guaranteeing installation quality and making the pore water pressure monitoring data more accurate and reliable, providing solid technical support for engineering monitoring. Attached Figure Description

[0037] Figure 1 is a schematic diagram of the overall structure of a multi-stage pore water pressure monitoring device with the same hole, as described in this application.

[0038] Figure 2 is a structural schematic diagram illustrating the digital osmotic pressure probe assembly of this application;

[0039] Figure 3 is a cross-sectional view illustrating the digital osmotic pressure probe assembly of this application;

[0040] Figure 4 is a schematic diagram of the circuit module of the multi-stage pore water pressure observation device of this application;

[0041] Figure 5 is a structural schematic diagram of the staged infiltration cylinder assembly embodying this application;

[0042] Figure 6 is a cross-sectional view illustrating the staged infiltration cylinder assembly of this application;

[0043] Figure 7a is an exploded structural diagram illustrating the watertight joint assembly of this application;

[0044] Figure 7b is a cross-sectional view of the combined structure of the watertight connector assembly of this application;

[0045] Figure 8 is a schematic diagram of the initial installation state of the multi-stage pore water pressure monitoring device of this application.

[0046] Figure 9 is a schematic diagram illustrating the installation status of the multi-stage pore water pressure monitoring device of this application.

[0047] Figure 10 is a schematic diagram showing the completed installation state of the multi-stage pore water pressure monitoring device of this application.

[0048] Explanation of reference numerals in the attached diagram: 1. Monitoring hole; 10. Digital osmosis probe assembly; 11. Permeable cylinder; 111. Permeable hole; 112. Cylinder cover; 113. Connector pipe; 12. Pore water pressure gauge assembly; 121. Encapsulation shell; 122. Small lock nut; 123. Large lock nut; 124. Data acquisition circuit board; 125. Pore water pressure sensor; 126. Signal line; 127. Probe multi-core cable; 13. Highly permeable material; 14. Permeable geotextile; 2. Staged permeable cylinder assembly; 20. Permeable cylinder; 21. Central tube; 22. Grid cage; 23. Water-soluble film; 24. Water-absorbing and expanding material; 30. Watertight connector assembly; 31. Threaded sleeve; 311. Horizontal plate; 32. Silicone ring gasket; 33. Fastening screw; 40. Multi-core cable; 100. Ground data acquisition station. Detailed Implementation

[0049] The present application will be further described in detail below with reference to Figures 1-10.

[0050] This application discloses a multi-level pore water pressure monitoring device with the same hole.

[0051] Please refer to Figures 1, 2, and 3. A monitoring well 1 is drilled on the site to be tested. A multi-stage pore water pressure observation device with the same well includes: multiple digital pore pressure probe assemblies 10 (one digital pore pressure probe assembly 10 is shown in the figure) spaced apart from the wellhead to the bottom of the monitoring well 1. The multiple digital pore pressure probe assemblies 10 together form a linearly distributed pore water pressure observation array to observe the pore water pressure variation pattern at different depths on the same monitoring profile in real time. The first-stage digital pore pressure probe assembly 10 and the ground acquisition station 100, as well as adjacent digital pore pressure probe assemblies 10, are electrically connected by multi-core cables 40.

[0052] The distance between two adjacent digital osmosis probe assemblies 10 is unlimited, and they are connected by a stepped-interval infiltration cylinder assembly 2. Adjacent digital osmosis probe assemblies 10 and stepped-interval infiltration cylinder assemblies 2 are connected by a watertight connector assembly 30 (see Figures 7a and 7b).

[0053] The digital pore pressure probe assembly 10 includes a long, hollow, tubular permeable cylinder 11, the diameter of which is slightly smaller than the aperture of the monitoring hole 1. A pore water pressure gauge assembly 12 for monitoring pore water pressure is installed inside the permeable cylinder 11. Multiple crescent-shaped permeable holes 111 are evenly spaced on the sidewall of the permeable cylinder 11 to allow water from the formation to enter the permeable cylinder 11. The inner wall of the permeable cylinder 11 and the pores of the pore water pressure gauge assembly 12 are filled with a highly permeable material 13, which is medium-coarse sand. The highly permeable material 13 is wrapped with a permeable geotextile 14, which is a non-woven geotextile.

[0054] Figure 2 illustrates the case where the permeable geotextile 14 directly wraps the highly permeable material 13, but it is not limited to this. Of course, the permeable geotextile 14 can also wrap the outside of the permeable cylinder 11, thereby indirectly wrapping the highly permeable material 13.

[0055] The permeable cylinder 11 has caps 112 at both ends, which can be threaded or welded to the permeable cylinder 11. A stainless steel connector tube 113 for connecting one end of the watertight connector assembly 30 is welded to the cap 112. The multi-core cable 40 connected to the pore water pressure gauge assembly 12 passes through the cap 112 and the connector tube 113 in sequence. The inner wall of the connector tube 113 is coated with potting compound to seal the stainless steel connector tube 113 and prevent leakage of highly permeable materials 13.

[0056] The pore water pressure gauge assembly 12 includes a housing 121, a small lock nut 122, a large lock nut 123, a data acquisition circuit board 124, a pore water pressure sensor 125 electrically connected to the data acquisition circuit board 124 and its signal line 126, and a probe multi-core cable 127 electrically connected to the data acquisition circuit board 124. The probe multi-core cable 127 is connected to a multi-core cable 40 outside the housing 121.

[0057] The probe multi-core cable 127, some signal lines 126, and the acquisition circuit board 124 are all located inside the enclosure 121. A small lock nut 122 is used to seal the interface where the signal line 126 extends out of the enclosure 121, and a large lock nut 123 is used to seal the interface between the probe multi-core cable 127 and the enclosure 121. The enclosure 121, along with the small lock nut 122 and the large lock nut 123, forms a sealed chamber, ensuring the safety of the electronic components and cable interfaces inside the acquisition circuit board 124 in harsh environments.

[0058] The pore water pressure sensor 125 is a commercially available high-precision vibrating wire pore water pressure gauge. The multi-core cable 40 is a multi-core signal cable, using four of its cores. Two cores are for power supply, used to power the pore water pressure sensor 125 and the acquisition circuit board 124; the other two cores are for data transmission, used for data transmission between the acquisition circuit board 124 and the ground acquisition station 100.

[0059] Please refer to Figure 4. The acquisition circuit board 124 includes an MCU microcontroller with an integrated storage module. The MCU microcontroller can perform calculations on the received data, and the storage module is used for data storage. The MCU microcontroller is electrically connected to an excitation frequency sweep module, a signal processing module, a temperature acquisition module, a bus communication module, and a power supply module. The MCU microcontroller and storage module consist of an STM32 microcontroller, a memory, and its peripheral circuits. By controlling the excitation frequency sweep module, signal processing module, temperature acquisition module, and bus communication module, the system can autonomously complete the acquisition, storage, and uploading of pore water pressure and ambient temperature, as well as the reception and response to commands from the host computer. The excitation frequency sweep module is used for the excitation and frequency sweep of the vibrating wire pore water pressure gauge. The signal processing module is used for filtering, amplifying, and ADC conversion of the wire signal, and sends the digital vibrating wire frequency to the MCU microcontroller. The temperature acquisition module is used to acquire the ambient temperature signal from the vibrating wire pore water pressure gauge, convert it into a digital value, and send it to the MCU microcontroller. The bus communication module is connected to the data transmission bus in the multi-core cable 40 for data interaction between the MCU microcontroller and the ground acquisition station 100. The power supply module is connected to the power supply cable in the multi-core cable 40 to provide power to the MCU microcontroller.

[0060] The acquisition circuit board 124 is installed in a sealed cavity formed by the encapsulation shell 121, small lock nut 122, and large lock nut 123, and is soldered to the signal line 126 of the pore water pressure sensor 125 and the multi-core cable 40, respectively, and sealed with epoxy resin for waterproofing. The small lock nut 122 and the large lock nut 123 respectively lock the signal line 126 of the pore water pressure sensor 125 and the probe multi-core cable 127, ensuring a stable cable connection and excellent waterproof performance.

[0061] The combination of permeable geotextile 14, stainless steel permeable cylinder 11, and highly permeable material 13 ensures smooth water seepage around the pore water pressure sensor 125.

[0062] Please refer to Figures 1, 5, and 6. The staged perforated cylinder assembly 2 includes one perforated cylinder 20 or multiple perforated cylinders 20 connected in series. Figure 1 illustrates the cases where the staged perforated cylinder assembly 2 includes one perforated cylinder 20 or two perforated cylinders 20 connected in series. The staged perforated cylinder assembly 2 located below the digital osmotic pressure probe assembly 10 includes one perforated cylinder 20, and the staged perforated cylinder assembly 2 located above the digital osmotic pressure probe assembly 10 includes two perforated cylinders 20. The length and number of staged perforated cylinder assemblies 2 are prepared according to the monitoring design requirements. A customized example is as follows: the digital osmotic pressure probe assembly 10 is 0.6m long, the perforated cylinders 20 are 1.2m long, and one digital osmotic pressure probe assembly 10 is installed every two perforated cylinders 20, forming a digital osmotic pressure probe array layout with a 3-meter interval.

[0063] Each diaphragm cylinder 20 includes a central pipe 21 and a grid cage 22 arranged concentrically from the inside out. A multi-core cable 40 extends and is laid inside the central pipe 21. The internal cavity of the central pipe 21 is used for the multi-core cable 40 and is sealed with potting compound. The cavity between the central pipe 21 and the grid cage 22 is the outer cavity, which is filled with a water-absorbing and expanding material 24. Before encountering water, the water-absorbing and expanding material 24 is in powder form and is wrapped by a water-soluble film 23. The multi-core cable 40 in the central pipe 21 is connected to both ends with watertight male and female connectors. The multi-core cable 40 on the pore water pressure gauge assembly 12 is also connected to both ends with watertight male and female connectors.

[0064] The multi-core cable 40 in the adjacent digital osmosis probe assembly 10 and the multi-core cable 40 in the central tube 21 of the diaphragm cylinder 20 are connected by a watertight male and a watertight female connector. The multi-core cables 40 in the central tube 21 of the two adjacent diaphragm cylinders 20 are also connected by a watertight male and a watertight female connector.

[0065] The water-soluble film 23 is a thin-film material that is easily degraded by water, such as a water-soluble membrane. Small pores are provided on the water-soluble film 23 to facilitate monitoring of water infiltration into the borehole 1. When the water-soluble film 23 dissolves slowly, the infiltrating water can not only accelerate the swelling time of the water-absorbing and swelling material 24 upon contact with water, but also cause the water-absorbing and swelling material 24 to rupture the water-soluble film 23 during the swelling process, thereby further accelerating the seepage prevention process of the borehole.

[0066] The outer diameter of the grid cage 22 of the seepage barrier 20 is the same as the outer diameter of the permeable cylinder 11, and the outer diameter of the central pipe 21 is the same as the outer diameter of the stainless steel joint pipe 113.

[0067] The water-absorbing and expanding material 24 can be made of water-absorbing and expanding resin. This material begins to expand after being exposed to water for several hours, with a maximum expansion volume of 700 times. It can extend out of the grid cage 22 and completely occupy the entire borehole space to form a sealing layer, effectively preventing vertical communication and mutual leakage between adjacent digital pressure probe assemblies 10.

[0068] Please refer to Figures 7a and 7b together. The ends of the central tube 21 are provided with external threads, which are used to connect the watertight connector assembly 30. The watertight connector assembly 30 includes a threaded sleeve 31 with openings at the top and bottom and a silicone ring gasket 32. The threaded sleeve 31 is provided with a horizontal plate 311 that divides it into two chambers, upper and lower.

[0069] A central opening in the horizontal plate 311 allows the multi-core cable 40 to pass through. Silicone ring gaskets 32 are installed on both sides of the horizontal plate 311. The chambers on both sides of the horizontal plate 311 are used for threaded connections to the connector tube 113 and the central tube 21 of the staged permeation cylinder assembly 2, respectively. Specifically, one chamber is used to insert and thread-connect the central tube 21 of the digital osmosis probe assembly 10, and the other chamber is used to insert and thread-connect the connector tube 113 on the cap 112 of the permeation cylinder 11. The threaded sleeve 31 has threaded holes at both the top and bottom for inserting fastening screws 33, which respectively press against the outer walls of the connector tube 113 and the central tube 21.

[0070] The silicone ring gasket 32 ​​serves as a separation layer to prevent the water-absorbing and swelling material 24 from invading the gap between the digital osmotic probe assembly 10 and the pore wall during the process of swelling upon contact with water, thus affecting the smooth water seepage around the digital osmotic probe assembly 10.

[0071] When the staged seepage tube assembly 2 includes multiple seepage tubes 20 connected in series, adjacent seepage tubes 20 are also connected using a watertight joint assembly 30, in the same manner as described above.

[0072] The multi-stage pore water pressure monitoring device adopts a factory-integrated manufacturing method. The assembly of multiple digital pore pressure probe components 10 and their internal circuit welding and encapsulation, the assembly of each unit of the seepage barrier 20 and their internal circuit wiring and encapsulation, and the watertight joint component 30 are all completed in the factory in advance, simplifying the cumbersome on-site assembly process.

[0073] The entire multi-core cable is divided into 40 sections: cables in the permeable cylinder 11 and cables in the permeable barrier cylinder 20. Each section is routed and encapsulated within the permeable cylinder 11 and the intermediate permeable barrier assembly 2 to prevent cable exposure and friction damage during transportation and installation. The joints between the permeable cylinder 11 and the intermediate permeable barrier assembly 2 use watertight male and female connectors. Watertight connector assemblies 30 are installed at the joints between the permeable barrier cylinder 20 and the permeable cylinder 11 in each intermediate permeable barrier assembly 2. These are assembled on-site and provide waterproofing. In the unassembled state, the male and female connectors of the watertight connector assemblies 30 are protected by caps and plugs, respectively.

[0074] This application also discloses an installation method for the above-described multi-stage pore water pressure monitoring device.

[0075] Please refer to Figures 8, 9, and 10. An installation method for the above-mentioned multi-stage pore water pressure monitoring device includes the following steps:

[0076] S1. According to the observation design requirements, the drilling rig is deployed to drill a borehole at the site to be measured, and the borehole casing is used to protect the well wall and prevent borehole collapse. The borehole reaches a depth 20 mm deeper than the design depth using a section of the seepage barrier. The drill rod is then pulled out, and a temporary working platform is erected near the borehole opening. All the necessary equipment and materials for installation are prepared.

[0077] S2, a customized multi-stage pore water pressure monitoring device was transported to the site in disassembled form. The number of digital pore pressure probe assemblies 10, and the length and number of the interstage infiltration tube assemblies 20 between adjacent digital pore pressure probe assemblies 10, were all prepared according to the monitoring design requirements. One customized example is as follows: the overall length of the digital pore pressure probe assembly 10 is 0.6m, each infiltration tube 20 is 1.2m long, and one digital pore pressure probe assembly 10 is installed every two infiltration tubes 20, forming a digital pore pressure probe array layout with a 3-meter interval.

[0078] S3. Before installation, soak all digital piezometric probe assemblies 10 in clean water for more than 24 hours on the ground to remove air from the probe heads inside the digital piezometric probe assemblies 10.

[0079] S4. Simultaneously, before burying, each of the permeable tubes 20 in the staged permeable tube assembly 2 is assembled on the ground. First, the ends of the connecting tubes of two adjacent permeable tubes 20 are connected by a watertight connector assembly 30, and then the internal thread of the threaded sleeve 31 is rotated for connection and the fastening screw 33 is used to tighten and fix it. The multi-core cable 40 in the central tube 21 of the two adjacent permeable tubes 20 is also assembled by using a watertight male and watertight female plug-in connection method.

[0080] S5. Using wellhead tools, pull ropes, and other auxiliary devices, the multi-stage digital osmosis probe assembly 10 and the stage-separated pore water pressure gauge assembly 2 are assembled and lowered into the monitoring borehole 1 using a step-by-step installation method. Specifically, 1) Select a section of pore water pressure gauge 20 as the lower sealing layer, tie the pore water pressure gauge 20 with a pull rope, and then lower it into the borehole, leaving its end above the borehole opening, and fix it with wellhead tools. The pull rope is used to assist in the installation, prevent the structure from falling into the borehole, and facilitate the removal of the equipment if it gets stuck. 2) Use the watertight connector assembly 30 to connect the pore water pressure gauge 20 to the last stage digital osmosis probe assembly 10 (which contains the last stage vibrating wire pore water pressure gauge, as shown in Figure 4) with threaded connections and tighten the fastening screws 33. 3) Slowly lower the pull rope to lower the last stage digital osmosis probe assembly 10 into the monitoring borehole 1, leaving its end above the borehole opening, and fix it with borehole tools. 4) Connect the watertight connector assembly 30 to the last-stage digital osmosis probe assembly 10 and connect it to the next-stage spacer cylinder assembly 2. Then, tighten the threaded connection and fasten the screws 33. Place the connected next-stage spacer cylinder assembly 2 into the monitoring hole 1, leaving its port at the hole opening, and fix it using the hole opening tool. 5) Continue assembling the penultimate-stage digital osmosis probe assembly 10 (containing the second-stage vibrating wire pore water pressure gauge). The multi-core cable 40 in the adjacent digital osmosis probe assembly 10 and the multi-core cable 40 in the central tube 21 of the spacer cylinder 20 are connected using a watertight male and watertight female connector.

[0081] The process continues sequentially until the first-stage digital osmotic pressure probe assembly 10 (containing the first-stage vibrating wire pore water pressure gauge, as shown in Figure 4) and the stage interval seepage cylinder assembly 2 and watertight joint assembly 30 are submerged in the hole.

[0082] S6, install ground acquisition station 100, debug and test the working status of each level of probe and the integrity of data transmission, and ensure that each probe works normally and that data transmission and clock synchronization are accurate.

[0083] S7, pull the casing out of the hole and fill the hole with water. The water-absorbing and expanding material 24 expands in volume when it comes into contact with water, forming a sealing layer between the digital osmosis probe assemblies 10 at each level, thus isolating the formation water pressure of the digital osmosis probe assemblies 10 at each level from each other, and preventing vertical communication and mutual leakage between the pore water pressure gauge assemblies 12 at each level.

[0084] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A multi-stage pore water pressure monitoring device with a single borehole, characterized in that, include: Multiple digital osmotic pressure probe assemblies (10) are spaced apart from bottom to top in the monitoring hole (1), a staged infiltration cylinder assembly (2) is connected between two adjacent digital osmotic pressure probe assemblies (10), and a watertight connector assembly (30) is used to connect the adjacent digital osmotic pressure probe assemblies (10) and the staged infiltration cylinder assembly (2). Each of the digital permeability probe assemblies (10) includes a long and hollow permeable cylinder (11), a pore water pressure gauge assembly (12) disposed inside the permeable cylinder (11), a highly permeable material (13) filling the gap between the inner wall of the permeable cylinder (11) and the pore water pressure gauge assembly (12), and a permeable geotextile (14) wrapping the highly permeable material (13); A multi-core cable (40) is electrically connected between adjacent pore water pressure gauge assemblies (12), the multi-core cable (40) passing through the interstage percolator assembly (2) between adjacent pore water pressure gauge assemblies (12).

2. The multi-stage pore water pressure monitoring device according to claim 1, characterized in that, The staged permeable tube assembly (2) includes a single permeable tube (20) or multiple permeable tubes (20) connected in series; Each of the aforementioned seepage-proof cylinders (20) includes a central tube (21) and a grid cage (22) arranged concentrically from the inside to the outside, and the space between the central tube (21) and the grid cage (22) is filled with a water-absorbing and expanding material (24) wrapped by a water-soluble film (23); The multi-core cable (40) extends from both ends of the central tube (21) and connects to two adjacent pore water pressure gauge assemblies (12).

3. The multi-stage pore water pressure monitoring device according to claim 2, characterized in that, The permeable cylinder (11) has multiple permeable holes (111) on its side wall. The permeable cylinder (11) has cylinder caps (112) at its upper and lower ends. Each cylinder cap (112) has a connector pipe (113) for connecting one end of the watertight connector assembly (30). The multi-core cable (40) connected to the pore water pressure gauge assembly (12) passes through the connector tube (113) and extends into the stage interval seepage cylinder assembly (2). The inner wall of the connector tube (113) is provided with potting compound.

4. The multi-stage pore water pressure monitoring device according to claim 3, characterized in that, The watertight connector assembly (30) includes a threaded sleeve (31) with openings at the top and bottom and a silicone ring gasket (32); The threaded sleeve (31) is provided with a horizontal plate (311) that divides it into upper and lower chambers. The horizontal plate (311) has a central opening for the multi-core cable (40) to pass through. The silicone ring gaskets (32) are respectively laid on both sides of the horizontal plate (311), and the chambers on both sides of the horizontal plate (311) are respectively used for threaded connection of the connector pipe (113) and the staged permeation cylinder assembly (2).

5. The multi-stage pore water pressure monitoring device according to claim 2, characterized in that, The pore water pressure gauge assembly (12) includes an encapsulation shell (121), a small lock nut (122), a large lock nut (123), a data acquisition circuit board (124), a pore water pressure sensor (125) electrically connected to the data acquisition circuit board (124) and its signal line (126), and a probe multi-core cable (127) electrically connected to the data acquisition circuit board (124). The probe multi-core cable (127), the signal line (126), and the acquisition circuit board (124) are all located inside the encapsulation shell (121). The small lock nut (122) is used to block the signal line (126) from extending out of the encapsulation shell (121), and the large lock nut (123) is used to block the probe multi-core cable (127) from extending out of the encapsulation shell (121).

6. The multi-stage pore water pressure monitoring device according to claim 5, characterized in that, The acquisition circuit board (124) includes: MCU microcontroller with integrated storage module; The excitation frequency sweep module, signal processing module, and temperature acquisition module are all electrically connected to the MCU microcontroller. The bus communication module and power supply module are electrically connected to the MCU microcontroller. The pore water pressure sensor (125) is electrically connected to the excitation frequency sweep module, the signal processing module and the temperature acquisition module.

7. The multi-stage pore water pressure monitoring device according to claim 5, characterized in that, The highly permeable material (13) is medium-coarse sand, the water-absorbing and swelling material (24) is water-absorbing and swelling resin, and the acquisition circuit board (124) is externally sealed with epoxy resin.

8. The multi-stage pore water pressure monitoring device according to any one of claims 2 to 7, characterized in that, The multiple digital osmotic pressure probe assembly (10), the diaphragm cylinder (20), and the watertight connector assembly (30) are all prefabricated as an integrated unit.

9. The multi-stage pore water pressure monitoring device according to claim 4, characterized in that, When the staged permeable tube assembly (2) includes multiple permeable tubes (20) connected in series, the watertight joint assembly (30) is connected between each permeable tube (20); The watertight connector assembly (30) also includes a fastening screw (33), and the threaded sleeve (31) is provided with a threaded hole corresponding to the fastening screw (33).

10. A method for installing a multi-stage pore water pressure monitoring device as described in any one of claims 2-9, characterized in that, Includes the following steps: According to the observation design requirements, the drilling rig was selected to drill holes at the site to be measured, and the well wall was protected by the drilling casing. The drilling depth reached a length of one section of the seepage barrier (20) deeper than the design depth. The drill rod was pulled out, and a temporary working platform was built near the hole opening to prepare the equipment and materials required for installing the multi-stage pore water pressure observation device in the same hole. According to the monitoring design requirements, the corresponding number of digital seepage probe components (10), each section of seepage barrier cylinder (20) and each watertight joint component (30) were transported to the site; Before installation, soak all digital pressure probe assemblies (10) in clean water for more than 24 hours to remove the air from the probe head inside the digital pressure probe assembly (10); Before installation, each of the permeable tubes (20) in the graded permeable tube assembly (2) is assembled on the ground, and two adjacent permeable tubes (20) are connected by a watertight joint assembly (30). The installation is carried out in stages. The first stage interstage infiltration cylinder assembly (2) is placed into the monitoring hole (1) and connected to the first stage digital osmosis probe assembly (10) at the upper end through the watertight connector assembly (30). Then the second stage interstage infiltration cylinder assembly (2) is placed into the monitoring hole (1) and connected to the upper end of the first stage digital osmosis probe assembly (10) through the watertight connector assembly (30). This process is repeated until all digital osmosis probe assemblies (10), interstage infiltration cylinder assemblies (2), and watertight connector assemblies (30) are submerged in the hole. Install the ground acquisition station (100) and test the working status and data transmission integrity of the digital osmosis probe components (10) at all levels; The casing is pulled out of the hole and filled with water. The water-absorbing and expanding material (24) expands in volume when it comes into contact with water, forming a sealing layer between the digital osmotic pressure probe components (10) at each level. This completes the isolation of the formation water pressure between the digital osmotic pressure probe components (10) at each level, and prevents vertical communication and mutual leakage between the pore water pressure gauge components (12) at each level.

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