Same-hole multi-stage pore water pressure observation device and installation method thereof

Abstract

The invention relates to a same-hole multi-stage pore water pressure observation device and an installation method of the same-hole multi-stage pore water pressure observation device. Comprising a plurality of digital osmotic pressure probe assemblies arranged in a monitoring hole from bottom to top, an interstage osmotic cylinder assembly connected between two adjacent digital osmotic pressure probe assemblies, and a watertight joint assembly used for connecting the adjacent digital osmotic pressure probe assembly and interstage osmotic cylinder assembly; the digital osmotic pressure probe assembly comprises a hollow water permeable cylinder, a pore water pressure gauge assembly arranged in the water permeable cylinder, a high-permeability material filled between the inner wall of the water permeable cylinder and the pore water pressure gauge assembly, and water permeable geotechnical cloth wrapping the high-permeability material; and a multi-core cable is electrically connected between the adjacent pore water pressure gauge assemblies. The same-hole multi-stage pore water pressure observation device and the installation method thereof have the advantages that the pore water pressure monitoring equipment and the backfill material are integrally designed, prefabricated and installed, the field installation technology is simplified, and the monitoring cost is reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of pore water pressure monitoring, and specifically relates to a same-hole multi-stage pore water pressure observation device and an installation method thereof. Background Art

[0002] Pore ​​water pressure is the pressure exerted by the water in soil, rock or other porous media. This pressure acts between particles or pores and is divided into static pore water pressure and excess static pore water pressure. Pore water pressure has an important influence on the mechanical properties and stability of rock and soil. Therefore, pore water pressure observation has become the main monitoring content in geotechnical engineering. It is widely used in slope engineering, dam engineering, foundation and roadbed engineering, foundation pit excavation, soft foundation vacuum preloading, and is an important data support for geotechnical deformation and stability analysis.

[0003] At present, the special instrument for pore water pressure observation is the pore water pressure gauge, also known as the piezometer. When in use, it is necessary to drill a hole and install the piezometer in the hole. The quality of the burial of the piezometer directly affects the subsequent observation effect and needs to meet the following key technical requirements: (1) Accurately install the piezometer at the designed depth; (2) Ensure that the seepage around the piezometer is unobstructed; (3) Ensure that the water pressure of the formation where the piezometer is located is isolated from the water pressure of other formations, and the water pressures of each layer are not connected up and down and interfere with each other. To achieve the above technical requirements, people usually adopt a step-by-step layered burial method: (1) Use auxiliary tools such as drill rods and hanging rods to lower the piezometer to the specified depth; (2) Put medium and coarse sand around the piezometer to form a sand pad filter layer; (3) Put bentonite or highly disintegrating clay balls to form a sealing layer.

[0004] In order to more accurately grasp the law of changes in pore water pressure inside rock and soil with depth, many engineering projects need to bury multiple (i.e. multi-level) piezometers at different soil depths. Compared with the traditional single-hole single-point arrangement, the same-hole multi-level arrangement (i.e., densely installing multiple piezometers in a single borehole) can not only effectively reduce the total number of boreholes and save project costs, but more importantly, all observation data are derived from the same monitoring profile, and the data at different observation points are more relevant and consistent.

[0005] When implementing a multi-level arrangement plan for the same hole, it is first necessary to ensure that the piezometers at each depth are laterally connected to the corresponding rock and soil layers, so that the pore water pressure in the same layer of rock and soil can be transmitted to the piezometer without pressure gradient loss. The current process is to fill sand around the piezometer, and the sand particles are in contact with the rock and soil pore walls, thereby effectively transmitting the pore water pressure. Secondly, since the pore water pressures of strata at different depths are different, it is also necessary to ensure the vertical isolation between the piezometers to prevent water from flowing between the upper and lower piezometers. To this end, it is necessary to fill clay and other materials between the upper and lower piezometers, and ensure that the piezometers at each depth work independently by burying them in steps and isolating them in layers.

[0006] The traditional step-by-step layered burial method has complex processes, cumbersome operation procedures, and is time-consuming. In addition, when encountering complex geological conditions such as deep hole operations and soft soil layers, the precise placement of backfill materials becomes particularly difficult to control. This directly leads to the difficulty in building an effective seepage filter layer around the pore water pressure gauge probe, and the upper and lower pore water pressure gauge probes face the problem of difficult or incomplete sealing, which affects the installation quality and cannot ensure the accuracy of the measured data. For this reason, it is urgent to innovate the design of multi-stage pore water pressure observation devices in the same hole and to innovate and simplify the traditional burial process to achieve reliable burial of pore water pressure gauges and ensure the accuracy of the measured values. Summary of the invention

[0007] In view of this, the present application provides a same-hole multi-stage pore water pressure observation device and an installation method thereof, so as to simplify the complex installation and burial process of the same-hole multi-stage pore water pressure gauges, shorten the operation time, and solve the problem of limited pore water pressure data measurement accuracy caused by the difficulty of backfill material placement.

[0008] In the first aspect, the present application provides a same-hole multi-stage pore water pressure observation device, which adopts the following technical solution: A same-hole multi-stage pore water pressure observation device, comprising: a plurality of digital osmotic pressure probe assemblies arranged in a monitoring hole from bottom to top, a stage interval osmotic cylinder assembly connected between two adjacent digital osmotic pressure probe assemblies, and a watertight joint assembly for connecting adjacent digital osmotic pressure probe assemblies and the stage interval osmotic cylinder assemblies; Each of the digital osmotic pressure probe assemblies comprises a long and hollow water-permeable cylinder, a pore water pressure gauge assembly disposed in the water-permeable cylinder, a high-permeability material filled between the inner wall of the water-permeable cylinder and the gap between the pore water pressure gauge assembly, and a water-permeable geotextile wrapping the high-permeability material; A multi-core cable is electrically connected between adjacent pore water pressure gauge assemblies, and the multi-core cable passes through the stage interval seepage tube assembly between adjacent pore water pressure gauge assemblies.

[0009] By adopting the above technical solution, the present application integrates the backfill material into the preparation process of the pore water pressure observation device: on the one hand, the coarse sand pad filter layer is prefabricated directly inside the digital seepage pressure probe assembly; on the other hand, the inter-stage seepage cylinder assembly is integrated and prepared in the factory to form an efficient sealing layer. This design concept changes the traditional method of separating the factory preparation of the pore water pressure observation device and the on-site backfilling of high-permeability materials, and realizes the integrated design, preparation and installation of the monitoring equipment and backfill materials. During on-site installation, no additional backfilling steps are required, which greatly simplifies the installation process, shortens the operation time, and can significantly improve the standardization and normalization level of buried installation, ensuring the accuracy and reliability of pore water pressure monitoring.

[0010] The same-hole multi-stage pore water pressure observation device provided in the present application can arrange multi-stage digital seepage pressure probe assemblies at a high density in a single borehole, such as arranging one digital seepage pressure probe assembly every 3 meters. This can not only effectively reduce the number of monitored boreholes and save project costs, but also all observation data are derived from the same monitoring profile, and the observation data at different observation points are more correlated and consistent.

[0011] Traditional pore water pressure meters use a split-line system, and each probe requires an independent cable. If n probes are installed, n cables are required, which is costly and cumbersome to install. This application uses the digitalization of the digital seepage pressure probe assembly and bus design to allow all probes in a single borehole to share a multi-core cable (two cores for power supply and two cores for data transmission), which greatly reduces the observation cost and simplifies the installation process.

[0012] Optionally, the interstage seepage cylinder assembly includes one section of seepage isolation cylinder or multiple sections of seepage isolation cylinders connected in series; Each of the seepage-isolating tubes comprises a central tube and a grid cage which are arranged concentrically from the inside to the outside, and a water-absorbing and swelling material wrapped by a water-soluble film is filled between the central tube and the grid cage; The multi-core cable extends from both ends of the central tube and is respectively connected to two adjacent pore water pressure gauge assemblies.

[0013] By adopting the above technical solution, the combination of the grid cage and the water-soluble film is used to provide a supporting skeleton and external wrapping for the water-swelling material, which is convenient for transportation and installation. The water-soluble film melts when it encounters water in the hole, and is used to clear the contact path between the water and the water-swelling material. The powdered water-swelling material will quickly expand and solidify in the seepage-proof cylinder after absorbing water, and is used to replace traditional bentonite or highly disintegrating clay balls to form an efficient sealing layer, effectively isolating the upper and lower layers of water, and ensuring that the water pressure in the formation where the digital seepage pressure probe assembly is located is isolated from the water pressure in other formations.

[0014] Optionally, the side wall of the water-permeable cylinder is provided with a plurality of water-permeable holes, and cylinder covers are provided at the upper and lower ends of the water-permeable cylinder, and the cylinder covers are provided with joint pipes for connecting one end of the watertight joint assembly; The multi-core cable connected to the pore water pressure gauge assembly passes through the joint pipe and extends into the stage interval seepage cylinder assembly, and the inner wall of the joint pipe is provided with potting glue.

[0015] By adopting the above technical solution, the water-permeable holes can ensure smooth water seepage around the pore water pressure gauge assembly, the joint pipe is used to connect with the watertight joint assembly, and the potting glue is used to seal the stainless steel joint pipe to prevent leakage of high-permeability materials.

[0016] Optionally, the watertight joint assembly includes a threaded sleeve and a silicone ring gasket arranged with upper and lower openings; The threaded sleeve is provided with a transverse plate which divides it into two upper and lower chambers, and the central opening of the transverse plate is used for the multi-core cable to pass through; The silicone ring pads are laid on both sides of the transverse plate, and the chambers on both sides of the transverse plate are used to threadedly connect the joint pipe and the stage interval seepage cylinder assembly.

[0017] By adopting the above technical solution, the silicone ring gasket serves as a separation layer to prevent the water-swelling material from invading the gap between the digital osmosis probe assembly and the hole wall during the water swelling process, thereby affecting the smooth water seepage around the digital osmosis probe assembly.

[0018] Optionally, the pore water pressure meter assembly includes a packaging shell, a small lock nut, a large lock nut, a collection circuit board, a pore water pressure sensor electrically connected to the collection circuit board and its signal line, and a probe multi-core cable electrically connected to the collection circuit board; Part of the probe multi-core cable, the signal line and the acquisition circuit board are all located in the packaging shell, the small lock nut is used to block the signal line from extending out of the packaging shell, and the large lock nut is used to block the probe multi-core cable from extending out of the packaging shell.

[0019] By adopting the above technical solution, the package shell is closely matched with the small lock nut and the large lock nut to form a closed chamber for encapsulating the multi-core cables of some probes, the cables of the pore water pressure sensor, and the acquisition circuit board. In harsh environments, it can provide waterproof protection for the electronic components and cable interfaces inside the acquisition circuit to ensure the safe operation of the acquisition circuit.

[0020] Optionally, the acquisition circuit board includes: MCU microcontroller with integrated storage module; An excitation frequency sweep module, a signal processing module, and a temperature acquisition module electrically connected to the MCU microcontroller; A bus communication module and a power supply module electrically connected to the MCU microcontroller; The pore water pressure sensor is electrically connected to the excitation frequency sweep module, the signal processing module and the temperature acquisition module.

[0021] By adopting the above technical solution, the MCU microcontroller is used to control the excitation frequency sweep module, signal processing module, temperature acquisition module, and bus communication module to independently complete the collection, storage and upload of pore water pressure and ambient temperature, and the reception and response of host computer commands. The excitation frequency sweep module is used for the excitation and frequency sweep of the pore water pressure sensor. The signal processing module is used for filtering, amplifying and ADC conversion of the string signal, and sends the digital quantity of the vibrating string frequency to the MCU microcontroller. The temperature acquisition module is used to collect the ambient temperature signal of the vibrating string pore water pressure meter, convert it into a digital quantity, and send it to the MCU microcontroller. The bus communication module is connected to the data transmission bus in the multi-core cable, and is used for data interaction between the MCU microcontroller and the ground acquisition station.

[0022] Optionally, the high permeability material is medium-coarse sand, the water-swellable material is a water-swellable resin, and the collection circuit board is externally sealed and coated with epoxy resin.

[0023] By adopting the above technical solution, medium-coarse sand is placed around the pore water pressure gauge assembly, and a coarse sand pad filter layer is prefabricated inside the digital osmotic pressure probe assembly. The water-absorbing and swelling resin material expands rapidly within a few hours after contacting water, and the maximum volume can increase to 700 times, tightly filling the entire borehole space to form a sealing layer, which can effectively isolate the upper and lower connections and mutual leakage between adjacent digital osmotic pressure probes. Epoxy resin is used for waterproof protection of the collection circuit board.

[0024] Optionally, the multiple digital seepage probe assemblies, the seepage isolation tube and the watertight joint assembly are all pre-prepared in an integrated manner.

[0025] By adopting the above technical solution, the factory preparation of the multi-stage pore water pressure observation device in the same hole and the on-site backfilling of the backfill material are integrated, which greatly simplifies the installation process and solves the problem of difficult to ensure the backfill quality under complex geological conditions. In addition, the integrated preparation design also facilitates the flexible splicing, assembly, disassembly and transportation of the digital seepage pressure probe components, ensuring that the probes at all levels can be accurately installed to the predetermined depth under the hole, improving installation efficiency and monitoring accuracy.

[0026] Optionally, when the inter-stage seepage tube assembly includes multiple sections of seepage-isolating tubes connected in series, each seepage-isolating tube is connected with the watertight joint assembly; The watertight joint assembly also includes a fastening screw, and the threaded sleeve is provided with a threaded hole corresponding to the fastening screw.

[0027] By adopting the above technical solution, when the stage interval seepage tube assembly includes multiple sections of seepage isolation tubes connected in series, adjacent seepage isolation tubes are also connected using watertight joint assemblies, and the threaded sleeve and the seepage isolation tube are tightened and fixed by the fastening screws.

[0028] In a second aspect, the present application provides a method for installing a same-hole multi-stage pore water pressure observation device, which adopts the following technical solution: A method for installing a same-hole multi-stage pore water pressure observation device, used for the aforementioned same-hole multi-stage pore water pressure observation device, comprises the steps of: According to the observation design requirements, the drilling rig is called to drill holes at the site to be measured, and the borehole casing is used to protect the well wall. The drilling depth reaches a depth of one section of the seepage barrier tube deeper than the design depth. The drill rod is pulled out, and a temporary working platform is built near the hole mouth 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 assemblies, each section of seepage isolation tube and each watertight joint assembly are transported to the site; Before burying, soak all digital osmotic pressure probe components in clean water for more than 24 hours to exhaust the air in the detection head inside the digital osmotic pressure probe components; Before burying, assemble each seepage-blocking tube in the interval seepage tube assembly on the ground, and first connect two adjacent seepage-blocking tubes through a watertight joint assembly; Using wellhead equipment, pull ropes and other auxiliary devices, the first-stage interval seepage tube assembly is placed into the monitoring hole and connected to the first-stage digital seepage pressure probe assembly at the upper end through a watertight joint assembly by adopting a step-by-step installation method; then the second-stage interval seepage tube assembly is placed into the monitoring hole and connected to the upper end of the first-stage digital seepage pressure probe assembly through a watertight joint assembly; this is done in sequence until all digital seepage pressure probe assemblies, interval seepage tube assemblies and watertight joint assemblies are sunk into the hole; Install the ground collection station, debug and test the working status of the probes of each level of digital osmotic pressure probe assembly and the integrity of data transmission, ensure that each digital osmotic pressure probe assembly probe works normally, and the data transmission and clock synchronization are accurate; The casing is lifted out of the hole and the hole is fully injected with water. The water-swellable material expands in volume when it comes into contact with water, forming a sealing layer between the digital pressure probe assemblies at each level, thereby isolating the formation water pressure of the digital pressure probe assemblies at each level from each other, and preventing the pore water pressure gauge assemblies at each level from being connected up and down or leaking from each other.

[0029] In summary, the present application includes at least one of the following beneficial technical effects: The present application includes at least one of the following beneficial technical effects: it avoids the separation problem in the traditional pore water pressure observation method, that is, the preparation of the pore water pressure observation device and the application of the backfill material are regarded as two independent links. At the same time, it avoids the problem that the burial process is complicated and lengthy due to the traditional step-by-step layered burial strategy, and the backfill quality is difficult to guarantee under complex working environments.

[0030] This application integrates the backfill material into the preparation process of the pore water pressure observation device to achieve the integrated design, preparation and installation of the observation device and the backfill material. Specifically, a coarse sand cushion layer is directly prefabricated inside the permeable cylinder, and a novel material combination of water-swellable material and water-soluble film is introduced and formed in the cavity of the seepage-proof cylinder to replace the traditional bentonite or highly disintegrating clay balls to form an efficient sealing layer. This design concept has changed the traditional construction mode, so that no additional backfill materials are required for on-site installation, and the installation process can be greatly simplified. More importantly, through the factory preparation model, the standardization and normalization of buried installation can be ensured, the installation quality can be effectively guaranteed, and the pore water pressure monitoring data can be more accurate and reliable, providing solid technical support for engineering monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structure of a same-hole multi-stage pore water pressure observation device embodying the present application; Figure 2 is a schematic diagram of the structure of a digital osmotic pressure probe assembly embodying the present application; Figure 3 is a cross-sectional view of a digital osmotic pressure probe assembly embodying the present application; Figure 4 It is a schematic diagram of a circuit module of a same-hole multi-stage pore water pressure observation device of the present application; Figure 5 It is a structural schematic diagram of the stage interval seepage cylinder assembly embodying the present application; Figure 6 is a cross-sectional view of a stage interval seepage cylinder assembly embodying the present application; Figure 7 is a schematic diagram of an exploded structure of a watertight joint assembly embodying the present application; Figure 8 is a cross-sectional view of the combined structure of the watertight joint assembly embodying the present application; Fig. 9 It is a schematic diagram of the initial installation state of the same-hole multi-stage pore water pressure observation device of the present application; Fig.10 It is a schematic diagram of the installation state of the same-hole multi-stage pore water pressure observation device of the present application; Fig.11 It is a schematic diagram of the installation completion state of the same-hole multi-stage pore water pressure observation device of the present application.

[0032] Description of reference numerals: 1. Monitoring hole; 10. Digital seepage pressure probe assembly; 11. Water permeable cylinder; 111. Water permeable hole; 112. Cylinder cover; 113. Joint pipe; 12. Pore water pressure gauge assembly; 121. Package shell; 122. Small lock nut; 123. Large lock nut; 124. Collection circuit board; 125. Pore water pressure sensor; 126. Signal line; 127. Probe multi-core cable; 13. Highly permeable materials; 14. Permeable geotextiles; 2. Inter-stage seepage tube assembly; 20. Seepage isolation tube; 21. Central tube; 22. Grid cage; 23. Water-soluble film; 24. Water-absorbing swelling material; 30. Watertight joint assembly; 31. Threaded sleeve; 311. Horizontal plate; 32. Silicone ring gasket; 33. Fastening screw; 40. Multi-core cable; 100. Ground collection station. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1-Figure 11 This application is described in further detail.

[0034] The embodiment of the present application discloses a device for observing multi-stage pore water pressure in the same hole.

[0035] See also Figure 1 , Figure 2 and Figure 3 A monitoring hole 1 is drilled on the site to be tested. A multi-level pore water pressure observation device for the same hole includes: multiple digital seepage pressure probe assemblies 10 (one digital seepage pressure probe assembly 10 is shown in the figure) arranged at intervals from the hole mouth to the bottom of the monitoring hole 1. The multiple digital seepage pressure probe assemblies 10 together constitute a linearly distributed pore water pressure observation array to observe the pore water pressure change law at different depths on the same monitoring section in real time. The first-level digital seepage pressure probe assembly 10 and the ground collection station 100, as well as the adjacent digital seepage pressure probe assemblies 10, are electrically connected through a multi-core cable 40.

[0036] The distance between two adjacent digital osmotic pressure probe assemblies 10 is not limited, and a step interval osmotic cylinder assembly 2 is connected between the two. The adjacent digital osmotic pressure probe assemblies 10 and the step interval osmotic cylinder assembly 2 are connected by a watertight joint assembly 30 (see Figure 7 and Figure 8 ).

[0037] The digital seepage pressure probe assembly 10 includes a long tubular and hollow water-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 provided in the water-permeable cylinder 11, and a plurality of crescent-shaped water-permeable holes 111 for water in the formation to enter the water-permeable cylinder 11 are evenly spaced on the side wall of the water-permeable cylinder 11. The inner wall of the water-permeable cylinder 11 and the pores of the pore water pressure gauge assembly 12 are filled with a high permeability material 13, which is medium-coarse sand, and the high permeability material 13 is wrapped with a permeable geotextile 14 on the outside, which is a non-woven geotextile.

[0038] Figure 2 The figure shows the situation that the water-permeable geotextile 14 directly wraps the high-permeability material 13 , but it is not limited to this. Of course, the water-permeable geotextile 14 can also be wrapped on the outside of the water-permeable cylinder 11 , thereby indirectly wrapping the high-permeability material 13 .

[0039] The upper and lower ends of the water-permeable cylinder 11 are provided with cylinder covers 112, which can be threadedly connected or welded to the water-permeable cylinder 11. A stainless steel joint pipe 113 for connecting one end of the watertight joint assembly 30 is welded on the cylinder cover 112. The multi-core cable 40 connected to the pore water pressure gauge assembly 12 passes through the cylinder cover 112 and the joint pipe 113 in sequence, and a potting glue is provided on the inner wall of the joint pipe 113 to seal the stainless steel joint pipe 113 to prevent the high permeability material 13 from leaking.

[0040] The pore water pressure meter assembly 12 includes a packaging shell 121, a small lock nut 122, a large lock nut 123, a collection circuit board 124, a pore water pressure sensor 125 electrically connected to the collection circuit board 124 and a signal line 126 thereof, and a probe multi-core cable 127 electrically connected to the collection circuit board 124. The probe multi-core cable 127 is connected to the multi-core cable 40 outside the packaging shell 121.

[0041] The probe multi-core cable 127, part of the signal line 126 and the acquisition circuit board 124 are all located in the package shell 121. The small lock nut 122 is used to block the interface where the signal line 126 extends out of the package shell 121, and the large lock nut 123 is used to block the interface between the probe multi-core cable 127 and the package shell 121. The package shell 121, the small lock nut 122 and the large lock nut 123 form a closed chamber to ensure the safety of the electronic components and cable interfaces inside the acquisition circuit board 124 in a harsh environment.

[0042] The pore water pressure sensor 125 uses a high-precision vibrating string pore water pressure meter sold on the market. The multi-core cable 40 uses a multi-core signal line, and uses four cores. Among them, two cores are power supply cables, which are used to power the pore water pressure sensor 125 and the acquisition circuit board 124; two cores are data transmission buses, which are used for data transmission between the acquisition circuit board 124 and the ground acquisition station 100.

[0043] Please also read Figure 4 The acquisition circuit board 124 includes an MCU microcontroller integrated with a storage module. The MCU microcontroller can calculate 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. Among them, the MCU microcontroller and the storage module are composed of an STM32 single-chip microcomputer, a memory and its peripheral circuits. By manipulating the excitation frequency sweep module, the signal processing module, the temperature acquisition module, and the bus communication module, the pore water pressure and ambient temperature can be collected, stored and uploaded, and the host computer instructions can be received and responded to. The excitation frequency sweep module is used for the excitation and frequency sweep of the vibrating string pore water pressure meter, and the signal processing module is used for filtering, amplifying and ADC conversion of the string signal, and sending the digital vibrating string frequency to the MCU microcontroller. The temperature acquisition module is used to collect the ambient temperature signal of the vibrating string pore water pressure meter, convert it into a digital quantity, and send it to the MCU microcontroller. The bus communication module is connected to the data transmission bus in the multi-core cable 40, and is used 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.

[0044] The acquisition circuit board 124 is installed in a sealed chamber formed by the packaging shell 121, the small lock nut 122, and the large lock nut 123, and is respectively welded to the signal line 126 of the pore water pressure sensor 125 and the multi-core cable 40, and is sealed and waterproofed by epoxy resin. 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 multi-core cable 127 of the probe, ensuring that the cable connection is stable and the waterproof performance is excellent.

[0045] The combination of the permeable geotextile 14 , the stainless steel permeable tube 11 , and the high permeability material 13 can ensure smooth water seepage around the pore water pressure sensor 125 .

[0046] See also Figure 1 , Figure 5 and Figure 6 The stage interval seepage tube assembly 2 includes a section of seepage tube 20 or multiple sections of seepage tube 20 connected in series. Figure 1The diagrams respectively illustrate the cases where the inter-stage seepage cylinder assembly 2 includes one seepage isolation cylinder 20 or two seepage isolation cylinders 20 connected in series. The inter-stage seepage cylinder assembly 2 located below the digital seepage pressure probe assembly 10 includes one seepage isolation cylinder 20, and the inter-stage seepage cylinder assembly 2 located above the digital seepage pressure probe assembly 10 includes two seepage isolation cylinders 20. The length and quantity of the inter-stage seepage cylinder assembly 2 are prepared according to the monitoring design requirements. A customized example is as follows: the digital seepage pressure probe assembly 10 is 0.6m long, the seepage isolation cylinder 20 is 1.2m long, and one digital seepage pressure probe assembly 10 is installed every two seepage isolation cylinders 20, forming a digital seepage pressure probe array layout with a spacing of 3 meters.

[0047] Each seepage-proof tube 20 includes a central tube 21 and a grid cage 22 which are concentrically arranged from the inside to the outside. The multi-core cable 40 is extended and laid in the central tube 21. The internal chamber of the central tube 21 is used for routing the multi-core cable 40 and is sealed with potting glue. The chamber between the central tube 21 and the grid cage 22 is an outer chamber, which is used to fill the water-absorbing swelling material 24. The water-absorbing swelling material 24 is in powder form before encountering water and is wrapped by a water-soluble film 23. The multi-core cable 40 in the central tube 21 is connected to watertight male and female joints at both ends, and the multi-core cable 40 on the pore water pressure gauge assembly 12 is also connected to watertight male and female joints at both ends.

[0048] The multi-core cables 40 in the adjacent digital seepage pressure probe assemblies 10 and the multi-core cables 40 in the central tube 21 of the seepage isolation tube 20 are connected by watertight male and watertight female plugs. The multi-core cables 40 in the central tubes 21 of two adjacent seepage isolation tubes 20 are also connected by watertight male and watertight female plugs.

[0049] The water-soluble film 23 is a film-like material that is easily degraded when in contact with water, such as a water-soluble film. Small holes are provided on the water-soluble film 23 to facilitate monitoring of water infiltration into the hole 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 when in contact with water, but also cause the water-absorbing and swelling material 24 to burst the water-soluble film 23 during the swelling process, thereby further accelerating the seepage isolation process of the borehole.

[0050] The outer diameter of the grid cage 22 of the seepage-proof tube 20 is the same as the outer diameter of the water-permeable tube 11 , and the outer diameter of the central tube 21 is the same as the outer diameter of the stainless steel joint tube 113 .

[0051] The water-swellable material 24 may be made of a water-swellable resin, which begins to swell 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 drilled hole space to form a sealing layer, effectively preventing the adjacent digital osmosis probe assemblies 10 from being connected up and down and leaking each other.

[0052] Please also read Figure 7 and Figure 8External threads are provided at the ends of both sides of the central tube 21, and the external threads are used to connect the watertight joint assembly 30. The watertight joint assembly 30 includes a threaded sleeve 31 and a silicone ring pad 32 with upper and lower openings. A horizontal plate 311 is provided in the threaded sleeve 31 to divide it into two upper and lower chambers.

[0053] The central opening of the horizontal plate 311 is used for passing the multi-core cable 40, and the two sides of the horizontal plate 311 are respectively paved with silicone ring pads 32, and the chambers on both sides of the horizontal plate 311 are respectively used to thread the joint pipe 113 and the central pipe 21 of the inter-stage seepage tube assembly 2. Specifically, one chamber is used to insert and thread the central pipe 21 of the digital seepage pressure probe assembly 10, and the other chamber is used to insert and thread the joint pipe 113 on the cylinder cover 112 of the water-permeable cylinder 11. The threaded sleeve 31 is provided with threaded holes for inserting fastening screws 33 on the upper and lower sides, respectively tightening the outer wall of the joint pipe 113 and the outer wall of the central pipe 21.

[0054] The silicone ring pad 32 serves as a separation layer to prevent the water-swellable material 24 from invading the gap between the digital osmotic pressure probe assembly 10 and the hole wall during the water swelling process, thereby affecting the smooth water seepage around the digital osmotic pressure probe assembly 10 .

[0055] When the inter-stage seepage tube assembly 2 includes multiple sections of seepage isolation tubes 20 connected in series, adjacent seepage isolation tubes 20 are also connected using watertight joint assemblies 30 in the same manner as described above.

[0056] The multi-stage pore water pressure observation device in the same hole adopts the factory-integrated preparation method. The assembly of multiple digital seepage pressure probe components 10 and their internal circuit welding packaging, the assembly of each unit of the seepage isolation tube 20 and their internal circuit routing packaging, and the watertight joint component 30 are all completed in advance in the factory, simplifying the tedious assembly process on site.

[0057] The entire multi-core cable 40 is divided into the cables in the water-permeable cylinder 11 and the cables in the seepage-blocking cylinder 20. Each section is routed and packaged in the inner cavity of the water-permeable cylinder 11 and the inter-stage seepage cylinder assembly 2 to avoid friction damage to the cables due to cable exposure during transportation and installation. The joints between the water-permeable cylinder 11 and the inter-stage seepage cylinder assembly 2 of each section of the cable are connected by watertight male and watertight female plugs. The joints between the seepage-blocking cylinder 20 and the water-permeable cylinder 11 of each inter-stage seepage cylinder assembly 2 are provided with watertight joint assemblies 30, which are plugged and assembled during on-site installation and provide waterproof performance. In the unassembled state, the male and female ports of the watertight joint assembly 30 are protected by protective caps and protective plugs, respectively.

[0058] The embodiment of the present application also discloses an installation method for the above-mentioned same-hole multi-stage pore water pressure observation device.

[0059] See also Fig. 9 , Fig.10 and Fig.11A method for installing a same-hole multi-stage pore water pressure observation device, used for the above-mentioned same-hole multi-stage pore water pressure observation device, comprises the following steps: S1, according to the observation design requirements, the drilling rig is called to drill holes at the site to be tested, and the borehole casing is used to protect the well wall to prevent the hole from collapsing. When the hole is drilled to a depth of 20 meters deeper than the design depth, the drill rod is pulled out, and a temporary working platform is built near the hole mouth, and all the equipment and materials required for installation are prepared.

[0060] S2, customize the multi-stage pore water pressure observation device in the same hole and transport it to the site in a disassembled form. The number of digital seepage probe assemblies 10, the length and number of the interval seepage tube assemblies 2 between two adjacent digital seepage probe assemblies 10 are prepared according to the monitoring design requirements. A customized example is as follows: the overall length of the digital seepage probe assembly 10 is 0.6m, each section of the seepage tube 20 is 1.2m long, and a digital seepage probe assembly 10 is installed every two sections of the seepage tube 20, forming a digital seepage probe array layout with a spacing of 3 meters.

[0061] S3, before burying, soak all digital osmosis pressure probe assemblies 10 in clean water on the ground for more than 24 hours to remove the air in the detection head inside the digital osmosis pressure probe assembly 10.

[0062] S4, at the same time, before burying, assemble each seepage-proof tube 20 in the inter-stage seepage-proof tube assembly 2 on the ground. First, the connecting tube ends of two adjacent seepage-proof tubes 20 are butted with a watertight joint assembly 30, and then the internal thread of the threaded sleeve 31 is used for rotation connection and tightened with a fastening screw 33. The multi-core cable 40 in the central tube 21 of the two adjacent seepage-proof tubes 20 is also assembled by plugging a watertight male connector and a watertight female connector.

[0063] S5, using wellhead equipment, pull ropes and other auxiliary devices, adopt a step-by-step installation method to assemble and sink the multi-stage digital seepage probe assembly 10 and the inter-stage seepage tube assembly 2 into the monitoring hole 1. Specifically, 1) select a section of seepage tube 20 as the lower sealing layer, tie the seepage tube 20 with a pull rope, and then sink it into the hole, leaving its end above the hole mouth, and fix it with wellhead equipment. The pull rope is used to assist in installation to prevent the structure from falling into the hole, and to facilitate the removal of the equipment when it is stuck. 2) Use a watertight joint assembly 30 to connect the seepage tube 20 with the first-stage digital seepage probe assembly 10 (containing the first-stage vibrating wire pore water pressure gauge, such as Figure 43) Slowly lower the pull rope and sink the first-stage digital seepage probe assembly 10 into the monitoring hole 1, leaving its end above the hole mouth, and fix it with a hole mouth tool. 4) Connect the watertight joint assembly 30 to the first-stage digital seepage probe assembly 10 and connect it to the next-stage interval seepage tube assembly 2, then make a threaded connection and tighten the screws 33 to fix it, sink the next-stage interval seepage tube assembly 2 into the monitoring hole 1, leaving its port at the hole mouth, and fix it with a hole mouth tool. 5) Continue to assemble the second-stage digital seepage probe assembly 10 (containing the second-stage vibrating string pore water pressure gauge). The multi-core cables 40 in the adjacent digital seepage probe assemblies 10 and the multi-core cables 40 in the central tube 21 of the seepage isolation tube 20 are connected by watertight male and watertight female plugs.

[0064] In sequence, until the last stage of digital seepage pressure probe assembly 10 (including the last stage of vibrating wire pore water pressure meter, such as Figure 4 As shown) and the stage interval seepage tube assembly 2 and the watertight joint assembly 30 are sunk into the hole.

[0065] S6, installing the ground acquisition station 100, debugging and testing the working status of each level of probes and the integrity of data transmission, ensuring that each probe works normally and data transmission and clock synchronization are accurate.

[0066] S7, the casing is lifted out of the hole and water is injected into the hole. The water-swellable material 24 expands in volume when exposed to water, and a sealing layer is formed between the digital osmotic pressure probe assemblies 10 at each level, so that the formation water pressures of the digital osmotic pressure probe assemblies 10 at each level are isolated from each other, and the pore water pressure gauge assemblies 12 at each level are not connected up and down and do not leak from each other.

[0067] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A device for observing multi-level pore water pressure in the same hole, characterized in that: include: A plurality of digital osmotic pressure probe assemblies (10) arranged in intervals from bottom to top in the monitoring hole (1), a step-interval osmotic cylinder assembly (2) connected between two adjacent digital osmotic pressure probe assemblies (10), and a watertight joint assembly (30) for connecting adjacent digital osmotic pressure probe assemblies (10) and the step-interval osmotic cylinder assembly (2); Each of the digital osmotic pressure probe assemblies (10) comprises a long and hollow water-permeable cylinder (11), a pore water pressure gauge assembly (12) arranged in the water-permeable cylinder (11), a high-permeability material (13) filled between the inner wall of the water-permeable cylinder (11) and the gap between the pore water pressure gauge assembly (12), and a permeable geotextile (14) wrapping the high-permeability material (13); A multi-core cable (40) is electrically connected between adjacent pore water pressure gauge assemblies (12), and the multi-core cable (40) passes through the stage interval seepage tube assemblies (2) between adjacent pore water pressure gauge assemblies (12).

2. The same-hole multi-stage pore water pressure observation device according to claim 1 is characterized in that: The inter-stage seepage cylinder assembly (2) comprises a section of seepage-isolating cylinder (20) or a plurality of sections of seepage-isolating cylinders (20) connected in series; Each of the seepage-isolating tubes (20) comprises a central tube (21) and a grid cage (22) which are arranged concentrically from the inside to the outside, and a water-absorbing and swelling material (24) wrapped by a water-soluble film (23) is filled between the central tube (21) and the grid cage (22); The multi-core cable (40) extends from both ends of the central tube (21) and is respectively connected to two adjacent pore water pressure gauge assemblies (12).

3. The same-hole multi-stage pore water pressure observation device according to claim 2 is characterized in that: The side wall of the water-permeable cylinder (11) is provided with a plurality of water-permeable holes (111); the upper and lower ends of the water-permeable cylinder (11) are provided with cylinder covers (112); and the cylinder covers (112) are each provided with a joint pipe (113) for connecting one end of the watertight joint assembly (30); The multi-core cable (40) connected to the pore water pressure gauge assembly (12) passes through the joint pipe (113) and extends into the inter-stage seepage cylinder assembly (2); a potting glue is provided on the inner wall of the joint pipe (113).

4. The same-hole multi-stage pore water pressure observation device according to claim 3 is characterized in that: The watertight joint assembly (30) comprises a threaded sleeve (31) with upper and lower openings and a silicone ring gasket (32); The threaded sleeve (31) is provided with a transverse plate (311) for dividing the threaded sleeve into two upper and lower chambers, and a central opening of the transverse plate (311) is used for the multi-core cable (40) to pass through; The silicone ring pads (32) are laid on both sides of the transverse plate (311), and the chambers on both sides of the transverse plate (311) are used to threadedly connect the joint pipe (113) and the stage interval seepage cylinder assembly (2).

5. The same-hole multi-stage pore water pressure observation device according to claim 2, characterized in that: The pore water pressure meter assembly (12) comprises a packaging shell (121), a small lock nut (122), a large lock nut (123), a collection circuit board (124), a pore water pressure sensor (125) electrically connected to the collection circuit board (124) and a signal line (126) thereof, and a probe multi-core cable (127) electrically connected to the collection circuit board (124); Part of the probe multi-core cable (127), the signal line (126) and the acquisition circuit board (124) are all located in the packaging shell (121); the small lock nut (122) is used to block the signal line (126) from protruding from the packaging shell (121); and the large lock nut (123) is used to block the probe multi-core cable (127) from protruding from the packaging shell (121).

6. The same-hole multi-stage pore water pressure observation device according to claim 5, characterized in that: The acquisition circuit board (124) comprises: MCU microcontroller with integrated storage module; An excitation frequency sweep module, a signal processing module, and a temperature acquisition module electrically connected to the MCU microcontroller; A bus communication module and a power supply module electrically connected to the MCU microcontroller; A 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 same-hole multi-stage pore water pressure observation device according to claim 5, characterized in that: The high permeability material (13) is medium-coarse sand, the water-absorbing and swelling material (24) is a water-absorbing and swelling resin, and the collection circuit board (124) is sealed and coated with epoxy resin.

8. The same-hole multi-stage pore water pressure observation device according to any one of claims 2 to 7, characterized in that: The multiple digital seepage probe assemblies (10), the seepage isolation tube (20), and the watertight joint assembly (30) are all pre-prepared in an integrated manner.

9. The same-hole multi-stage pore water pressure observation device according to claim 4, characterized in that: When the inter-stage seepage tube assembly (2) comprises a plurality of seepage-isolating tubes (20) connected in series, each of the seepage-isolating tubes (20) is connected with the watertight joint assembly (30); The watertight joint assembly (30) further comprises 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 same-hole multi-stage pore water pressure observation device, used for the same-hole multi-stage pore water pressure observation device according to any one of claims 2 to 8, characterized in that: Includes steps: According to the observation design requirements, a drilling rig is used to drill a hole at the site to be measured, and a borehole casing is used to protect the well wall. The drilling depth reaches a point deeper than the design depth by one section of the seepage barrier tube (20), the drill rod is pulled out, and a temporary working platform is built near the hole mouth 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, a corresponding number of digital seepage probe assemblies (10), each section of the seepage isolation tube (20) and each watertight joint assembly (30) are transported to the site; Before burying, all digital osmotic pressure probe assemblies (10) are soaked in clean water for more than 24 hours to discharge the air in the detection head inside the digital osmotic pressure probe assembly (10); Before burying, the individual seepage-blocking tubes (20) in the inter-stage seepage-blocking tube assembly (2) are assembled on the ground, and two adjacent seepage-blocking tubes (20) are first connected via a watertight joint assembly (30); By using wellhead tools, pull ropes and other auxiliary devices, the first-stage interval seepage tube assembly (2) is placed into the monitoring hole (1) and connected to the first-stage digital seepage pressure probe assembly (10) at the upper end thereof via a watertight joint assembly (30); the second-stage interval seepage tube assembly (2) is then placed into the monitoring hole (1) and connected to the upper end of the first-stage digital seepage pressure probe assembly (10) via a watertight joint assembly (30); and this is done in sequence until all the digital seepage pressure probe assemblies (10), the interval seepage tube assemblies (2) and the watertight joint assembly (30) are sunk into the hole; Installing a ground collection station (100), debugging and testing the working status of each level of the digital osmotic pressure probe assembly (10) and the integrity of data transmission, ensuring that each digital osmotic pressure probe assembly (10) works properly and that data transmission and clock synchronization are accurate; The casing is lifted out of the hole and water is injected into the hole. The water-swellable material (24) expands in volume when it comes into contact with water, forming a sealing layer between the digital seepage pressure probe assemblies (10) of each level, thereby isolating the formation water pressure of the digital seepage pressure probe assemblies (10) of each level from each other, and preventing the pore water pressure gauge assemblies (12) of each level from being connected to each other and from leaking from each other.

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