Method for monitoring pore pressure of soil body in pit in deep foundation pit excavation process

Abstract

The invention provides a method for monitoring pore pressure of soil in a pit in the excavation process of a deep foundation pit, which comprises the following steps of: 1, forming a pore water pressure gauge mounting hole; 2, preprocessing the wireless pore water pressure gauge; thirdly, a wireless pore water pressure gauge is placed, wherein the pore water pressure gauge is placed at the bottom of the pore water pressure gauge mounting hole, and medium sand and fine sand are used for making a filtering layer around a water inlet of the wireless pore water pressure gauge; the fourth step of foundation pit excavation, wherein after the set duration, the foundation pit is excavated according to the foundation pit construction plan; 5, the wireless pore water pressure gauge is taken out, specifically, when the foundation pit is excavated to the burial depth of the wireless pore water pressure gauge, the wireless pore water pressure gauge is taken away; 6, pore water pressure data are obtained. According to the method for monitoring the pore pressure of the soil body in the pit in the deep foundation pit excavation process, electric wires cannot be generated to interfere with construction of the foundation pit, and the problem that data of an existing gap water pressure gauge are led out of the foundation pit through the electric wires to interfere with the construction of the foundation pit is solved.

Description

Technical Field

[0001] This application relates to the field of foundation pit construction monitoring technology, and in particular to a method for monitoring the pore pressure of soil in the deep foundation pit during the excavation process. Background Technology

[0002] The pore water pressure response within the foundation pit plays a crucial role in controlling pit deformation and environmental deformation. Therefore, monitoring pore pressure during foundation pit construction to understand the relationship between pore water pressure and time is essential for providing a data foundation for scientific foundation pit construction. The existing monitoring method involves burying a pore water pressure gauge at a specific depth within the foundation pit. The gauge's power cord is extended and connected to a data acquisition circuit board on the ground. This circuit board is then connected to a computer for data transmission. The acquisition circuit board includes a data acquisition unit and a data output unit. The data acquisition unit collects the water pressure data detected by the pore water pressure gauge, while the data output unit outputs the collected data to the computer in real time. However, this method has several drawbacks: the power cord running through the foundation pit can interfere with construction, and excessively long power cords can lead to signal transmission distortion. Summary of the Invention

[0003] This invention aims to provide a method for monitoring the pore pressure of soil inside a deep foundation pit during the excavation process without causing interference from electrical wires. It solves the problem that existing pore water pressure gauge data, when transmitted to the outside of the foundation pit via electrical wires, interferes with the foundation pit construction.

[0004] To achieve the above-mentioned objectives, this invention employs the following technology: a method for monitoring pore pressure in soil during deep foundation pit excavation, characterized by the following steps: First, forming a pore water pressure gauge installation hole: conducting on-site geological surveys to determine the location and depth of the borehole, and drilling a pore water pressure gauge installation hole that meets the design requirements at the designated location using a drilling rig; Second, pre-treating the wireless pore water pressure gauge: wrapping the detection head of the wireless pore water pressure gauge with a water-soaked fine sandbag, and immersing the entire wireless pore water pressure gauge in a bucket of water for at least 30 minutes in advance to remove air until installation. The process involves: 1. Removing the device from the water; 2. Placing the wireless pore water pressure gauge: The gauge is placed at the bottom of the mounting hole, and a filter layer of medium and fine sand is created around the inlet. 3. Excavating the foundation pit: After the set time, the foundation pit is excavated according to the construction plan. 4. Removing the wireless pore water pressure gauge: When the foundation pit reaches the depth to which the gauge is buried, the gauge is removed. 5. Obtaining pore water pressure data: The sealing cylinder of the wireless pore water pressure gauge is opened, the acquisition circuit board is removed, connected to a computer, and the collected data is uploaded. The pore water pressure values ​​collected by the circuit board are used to plot a curve showing the relationship between the pore water pressure value and time. The wireless pore water pressure gauge includes a pore water pressure sensor, a data acquisition circuit board, a sealed cylinder, and a tubular cable holder connected to the lower end of the sealed cylinder. The data acquisition circuit board includes a data acquisition unit, a memory, and a data output unit. The data acquisition unit is used to acquire the pore water pressure values ​​detected by the pore water pressure gauge at various times. The memory is used to store the pore water pressure values ​​detected by the pore water pressure gauge at various times. The data output unit is used to output the values ​​stored in the memory. The pore water pressure value is stored in the pore water pressure gauge connected to the lower end of the cable holder. The acquisition circuit board is installed inside the sealed cylinder, which is equipped with a battery to power the acquisition circuit board. The wires of the acquisition circuit board pass through a through-hole on the end of the sealed cylinder connected to the cable holder and are then connected to the wires of the pore water pressure gauge. The wires of the acquisition circuit board are sealed together with the through-hole. The connection point between the wires of the acquisition circuit board and the wires of the pore water pressure gauge is located inside the cable holder. This invention integrates the acquisition circuit board into the sealed cylinder along with the pore water pressure gauge, thus eliminating the need for the wires between the acquisition circuit board and the pore water pressure gauge to be led from the bottom of the foundation pit to the acquisition circuit board located on the ground, thereby preventing wire interference during construction. The cable holder allows for the coiling of long wires from the acquisition circuit board and the pore water pressure gauge, preventing electromagnetic interference from coiled wires from affecting the operation of the acquisition circuit board. Using medium and fine sand as a filter layer around the inlet of the wireless pore water pressure gauge can prevent cement slurry and other solids from clogging the inlet of the pore water pressure gauge.

[0005] Preferably, the sealing cylinder includes a cylinder body, an upper end cap detachably and sealingly connected to the upper end of the cylinder body, and a lower end cap detachably and sealingly connected to the lower end of the cylinder body. The wire passage hole is provided on the lower end cap, and the wires of the acquisition circuit board are sealed and passed through the wire passage hole. This design facilitates the manufacture of the sealing cylinder.

[0006] Preferably, the upper end cap is detachably inserted into the upper end of the cylinder, and a plurality of upper end cap fixing bolts pass through the cylinder and are threaded into the threaded holes on the upper end cap portion of the upper end cap. The upper end cap fixing bolts are distributed circumferentially along the cylinder. The lower end cap is detachably inserted into the lower end of the cylinder, and a plurality of lower end cap fixing bolts pass through the cylinder and are threaded into the threaded holes on the lower end cap portion of the lower end cap on the cylinder side. The lower end cap fixing bolts are distributed circumferentially along the cylinder. The cylinder and the end caps are reliably fixed together.

[0007] Preferably, the portion of the upper end cover inserted into the cylinder has two sealing grooves on its circumferential surface. Two upper end cover sealing rings are fitted within these grooves, sealing the upper end cover to the cylinder. Similarly, the portion of the lower end cover inserted into the cylinder has two sealing grooves on its lower circumferential surface. Two lower end cover sealing rings are fitted within these grooves, sealing the lower end cover to the cylinder. This ensures a reliable seal.

[0008] Preferably, the lower end of the wire-gathering seat has an end wall with a threaded hole. The pore water pressure gauge has a threaded head, and the wire of the pore water pressure gauge is led out from the end face of the threaded head, which is threaded into the threaded hole. The diameter of the portion of the lower end cover that passes through the cylinder is smaller than the diameter of the lower end cover itself. The lower end cover is detachably inserted into the wire-gathering seat. Several wire-gathering seat fixing bolts pass through the wire-gathering seat and are threaded into the threaded holes on the lower end cover portion of the wire-gathering seat. The connection is reliable and convenient.

[0009] Preferably, the outer end face of the upper cover is provided with a threaded hole for installing a suspension line. In the third step, a threaded head is connected to the suspension line, and the threaded head is connected to the threaded hole. The wireless pore water pressure gauge is placed into the pore water pressure gauge mounting hole through the suspension line. Soil is filled into the pore water pressure gauge mounting hole to cover the wireless pore water pressure gauge and fix it in the required posture. The suspension line is then dropped into the pore water pressure gauge mounting hole, and soil is filled until the pore water pressure gauge mounting hole is filled. This allows the present invention to easily maintain its existing posture in the soil at the site of the excavation pit.

[0010] Preferably, the wires of the acquisition circuit board are connected to one end of a waterproof cable, which is sealed within the wire-passing hole. The wires of the pore water pressure gauge are connected to the other end of the waterproof cable. The wire-passing hole, located at one end of the cable-concentrating base, has a large-diameter section. An elastic sealing ring passes through this large-diameter section, sealing the waterproof cable to the wire-passing hole. A step is formed between the large-diameter section and the wire-passing hole. Connecting the wires of the acquisition circuit board and the pore water pressure gauge via a waterproof cable, rather than directly, improves the reliability of the sealing cylinder. By creating a step with a large-diameter section at one end of the cable-concentrating base and installing a sealing ring, the sealing ring shortens axially and increases radially under water pressure, resulting in a better seal under higher water pressure. If the direction is reversed, the force causing the sealing ring to detach under high water pressure is greater, making a poor seal more likely.

[0011] Preferably, the elastic sealing ring is sealed within the wire hole by a sealing strip formed by adhesive. This improves the sealing reliability between the sealing ring and the large-diameter section. The sealing ring should not be bonded to the waterproof cable adhesive, otherwise it will be inconvenient to remove the data acquisition circuit board.

[0012] Preferably, the threading hole is a straight hole, and an annular blade extending circumferentially along the threading hole is provided at one end of the large-diameter section of the threading hole. The cross-section of the annular blade is triangular, and the annular blade protrudes from the step. The inner circumferential surface of the annular blade and the circumferential surface of the threading hole are located on the same cylindrical surface. The cutting edge direction of the annular blade is the same as the center line direction of the threading hole. The surface of the waterproof cable is provided with an insulating plastic layer, and the diameter of the waterproof cable is larger than the diameter of the threading hole. In use, the waterproof cable is passed into the threading hole from the end where the cable holder is located. During the passage, the annular blade cuts off a layer of the surface of the waterproof cable, thereby improving the sealing effect between the waterproof cable and the threading hole. The cut surface layer of the waterproof cable will compress the sealing ring, thereby improving the sealing effect of the sealing ring on the waterproof cable.

[0013] Preferably, the conductive core of the waterproof cable has a wiring hole with a larger inner end and a smaller outer end on one end face of the cable holder. The end of the wire of the pore water pressure gauge is knotted to form a clip that can pass into the wiring hole. The clip passes through the wiring hole, which is filled with conductive adhesive to form a clamp head. The clamp head bonds the wire of the pore water pressure gauge into the wiring hole. Since the wire at the cable holder end is exposed in the soil, it is prone to falling off due to soil erosion and water pressure. This connection method makes the connection more reliable.

[0014] The present invention has the following advantages: the collected data can be stored first, and then the data can be exported after retrieving the present invention, thus eliminating the need to install wires in the foundation pit and avoiding interference from wires in the foundation pit construction. Attached Figure Description

[0015] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of a wireless gap pressure gauge; Figure 3 yes Figure 2 A magnified view of a portion of point A; Figure 4 yes Figure 3 A magnified view of a portion of point B; Figure 5 yes Figure 3 A magnified view of a portion at point C; Figure 6 yes Figure 5 A magnified view of a portion at point D; Figure 7 This is a schematic diagram showing the usage status of a wireless gap pressure gauge.

[0016] In the diagram: 1. Pore water pressure gauge; 2. Acquisition circuit board; 3. Sealing cylinder; 4. Coiling seat; 5. Cylinder body; 6. Upper end cover; 7. Lower end cover; 8. Wires of acquisition circuit board; 9. Waterproof cable; 10. Threaded head; 11. Wires of pore water pressure gauge; 12. Battery; 13. Upper end cover fixing bolt; 14. Lower end cover fixing bolt; 15. Upper end cover sealing ring; 16. Lower end cover sealing ring; 17. Water inlet; 18. Coiling seat fixing bolt; 19. Threaded hole; 20. Large diameter section; 21. Elastic sealing ring; 22. Sealing strip; 23. Annular blade; 24. Cut-off waterproof cable surface layer; 25. Conductive core; 26. Wiring hole; 27. Clamping block; 28. Clamping head; 30. Step; 31. Plastic layer; 32. Medium sand; 33. Fine sand; 34. Wire mesh bag. Detailed Implementation

[0017] The present invention will now be described in conjunction with the accompanying drawings and specific embodiments, wherein the anchor rod is inclined with one end higher than the other end, which is connected to the inner retaining wall, and the lower end of the anchor rod is lower than the bottom of the inner pit.

[0018] See Figures 1 to 7A method for monitoring pore pressure in soil during deep foundation pit excavation includes the following steps: First, forming the pore water pressure gauge installation hole: Conducting on-site geological surveys to determine the location and depth of the borehole, and drilling the pore water pressure gauge installation hole at the designated location using a drilling rig, meeting the design requirements. Second, pre-treating the wireless pore water pressure gauge: Wrapping the detection head of the wireless pore water pressure gauge with a water-soaked fine sandbag, and immersing the entire wireless pore water pressure gauge in a bucket of water for at least 30 minutes beforehand to remove air, only removing it from the water at installation time. Third, placing the wireless pore water pressure gauge: Placing the pore water pressure gauge at the bottom of the installation hole, and then... The inlet 17 is surrounded by a filter layer of medium sand 32 and fine sand 33. Specifically, fine sand 33 is placed on the pore pressure gauge 1, followed by coarse sand 32, and then the coarse sand is covered with a wire mesh bag 34. The fourth step is the excavation of the foundation pit: after the set time, the foundation pit is excavated according to the foundation pit construction plan. The fifth step is to remove the wireless pore water pressure gauge: when the foundation pit is excavated to the depth of the wireless pore water pressure gauge, the wireless pore water pressure gauge is removed. The sixth step is to obtain pore water pressure data: the sealing cylinder 3 of the wireless pore water pressure gauge is opened, the acquisition circuit board 2 is taken out, connected to the computer, the pore water pressure value collected by the acquisition circuit board is uploaded, and the relationship curve between the pore water pressure value and time is plotted.

[0019] The wireless pore water pressure gauge includes a pore water pressure sensor 1, a data acquisition circuit board 2, a sealed cylinder 3, and a tubular cable holder 4 connected to the lower end of the sealed cylinder. The data acquisition circuit board includes a data acquisition unit, a storage unit, and a data output unit. The data acquisition unit acquires the water pressure data detected by the pore water pressure gauge, the storage unit stores the pore water pressure data acquired by the data acquisition unit, and the data output unit outputs the pore water pressure data stored in the storage unit. The sealed cylinder includes a cylinder body 5, a detachable and sealed upper end cap 6 connected to the upper end of the cylinder body, and a detachable and sealed lower end cap 7 connected to the lower end of the cylinder body. The lower end cap has a wire passage hole. The wire 8 of the data acquisition circuit board is connected to one end of a waterproof cable 9. The waterproof cable is sealed and passes through the wire passage hole. The pore water pressure gauge has a threaded head 10, which connects to a threaded hole at the lower end of the cable holder. The wire 11 of the pore water pressure gauge is connected to the lower end of the waterproof cable. The data acquisition circuit board is installed inside the sealed cylinder. A battery 12 is installed inside the sealed cylinder to power the data acquisition circuit board. The connection points between the wires of the data acquisition circuit board and the wires of the pore water pressure gauge are located inside the cable holder. The upper end cover is detachably inserted through the upper end of the cylinder, and several upper end cover fixing bolts 13 pass through the cylinder and are threaded into the threaded holes of the upper end cover. The upper end cover fixing bolts are distributed circumferentially along the cylinder. The lower end cover is detachably inserted through the lower end of the cylinder, and several lower end cover fixing bolts 14 pass through the cylinder and are threaded into the threaded holes of the lower end cover on the cylinder side. The lower end cover fixing bolts are distributed circumferentially along the cylinder. The upper end cover has two sealing grooves on its circumferential surface where it is inserted into the cylinder. Two upper end cover sealing rings 15 are fitted within these grooves, sealing the upper end cover to the cylinder. Similarly, the lower end cover has two sealing grooves on its lower circumferential surface where it is inserted into the cylinder. Two lower end cover sealing rings 16 are fitted within these grooves, sealing the lower end cover to the cylinder. The lower end of the cable holder has an end wall with a threaded hole. The wire of the pore water pressure gauge is led out from the end face of the threaded head. The pore water pressure gauge has an inlet 17. The diameter of the portion of the lower end cover that passes through the cylinder is smaller than the diameter of the lower end cover itself. The lower end cover is removably inserted into the cable holder. Several cable holder fixing bolts 18 pass through the cable holder and are threaded into the cable holder side threaded holes on the lower end cover. The outer end face of the upper cover is provided with a threaded hole 19 for installing a suspension line. In the third step, a threaded head is connected to the suspension line and the threaded head is connected to the threaded hole. A pore water pressure gauge installation hole is drilled to the set depth at the location where the foundation pit is set. The threaded head is connected to the suspension line and the threaded head is connected to the threaded hole. The wireless pore water pressure gauge is placed into the pore water pressure gauge installation hole through the suspension line. Soil is backfilled into the pore water pressure gauge installation hole to cover the wireless pore water pressure gauge and fix it in the required position. The suspension line is dropped into the pore water pressure gauge installation hole. Soil is backfilled until the pore water pressure gauge installation hole is filled.A large-diameter section 20 is provided at the cable concentrator's end of the cable pass-through hole. An elastic sealing ring 21 passes through the large-diameter section, sealingly connecting the waterproof cable to the cable pass-through hole. A step 30 is formed between the large-diameter section and the cable pass-through hole. The elastic sealing ring is sealed and fixed inside the cable pass-through hole by a sealing strip 22 formed by adhesive. The cable pass-through hole is a straight hole. At one end of the large-diameter section, there is an annular blade 23 extending circumferentially along the cable pass-through hole. The cross-section of the annular blade is triangular, and the annular blade protrudes from the step. The inner circumferential surface of the annular blade and the circumferential surface of the cable pass-through hole are located on the same cylindrical surface. The cutting edge of the annular blade is in the same direction as the center line of the cable pass-through hole. The surface of the waterproof cable is covered with an insulating plastic layer 31, and the diameter of the waterproof cable is larger than the diameter of the cable pass-through hole. In use, the waterproof cable is inserted into the cable pass-through hole from the end where the cable concentrator is located. During insertion, the annular blade cuts off a layer of the surface of the waterproof cable, thereby improving the sealing effect between the waterproof cable and the cable pass-through hole. The cut surface layer 24 of the waterproof cable will compress the sealing ring, thereby improving the sealing effect of the sealing ring on the waterproof cable. The conductive core 25 of the waterproof cable (the wires of a pore water pressure gauge are connected together through a conductive core, and the conductive cores are insulated from each other) has a wiring hole 26 with a larger inner end and a smaller outer end on one end face of the cable holder. The end of the wire of the pore water pressure gauge is knotted to form a clip 27 that can be inserted into the wiring hole. The clip is inserted into the wiring hole, and the wiring hole is filled with conductive glue to form a clip head 28. The clip head glues the wire of the pore water pressure gauge into the wire hole.

Claims

1. A method for monitoring pore pressure of soil within a deep foundation pit during excavation, characterized in that, Step 1: Drilling the pore water pressure gauge installation hole: Conduct on-site geological surveys to determine the location and depth of the borehole. Drill the pore water pressure gauge installation hole at the designated location using a drilling rig, ensuring it meets design requirements. Step 2: Pre-treatment of the wireless pore water pressure gauge: Wrap the detection head of the wireless pore water pressure gauge with a water-soaked fine sandbag. Immerse the entire wireless pore water pressure gauge in a bucket of water for at least 30 minutes beforehand to remove air. Remove it from the water only during installation. Step 3: Placing the wireless pore water pressure gauge: Place the pore water pressure gauge into the hole. At the bottom of the pore water pressure gauge installation hole, a filter layer of medium and fine sand is used around the inlet of the wireless pore water pressure gauge; Step 4: Excavation of the foundation pit: After the set time, the foundation pit is excavated according to the foundation pit construction plan; Step 5: Removal of the wireless pore water pressure gauge: When the foundation pit is excavated to the depth of the wireless pore water pressure gauge, the wireless pore water pressure gauge is removed; Step 6: Acquisition of pore water pressure data: The sealing cylinder of the wireless pore water pressure gauge is opened, the acquisition circuit board is taken out, connected to the computer, the pore water pressure values ​​collected by the acquisition circuit board are uploaded, and the pore water pressure values ​​are plotted against the data. The relationship curve between time; the wireless pore water pressure gauge includes a pore water pressure sensor, a data acquisition circuit board, a sealed cylinder, and a tubular cable holder connected to the lower end of the sealed cylinder. The data acquisition circuit board includes a data acquisition unit, a memory, and a data output unit. The data acquisition unit is used to acquire the pore water pressure values ​​detected by the pore water pressure gauge at various times. The memory is used to store the pore water pressure values ​​detected by the pore water pressure gauge at various times. The data output unit is used to output the pore water pressure values ​​stored in the memory. The pore water pressure gauge is connected to the lower end of the cable holder. The data acquisition circuit board is installed inside the sealed cylinder. The sealed cylinder is equipped with a battery to power the data acquisition circuit board. The wires of the data acquisition circuit board pass through a through-hole on the end of the sealed cylinder connected to the cable holder and are connected to the wires of the pore water pressure gauge. The wires of the data acquisition circuit board are sealed and connected to the through-hole. The connection point between the wires of the data acquisition circuit board and the wires of the pore water pressure gauge is located inside the cable holder. The wires of the data acquisition circuit board are sealed and connected to the through-hole.

2. The method for monitoring pore pressure of soil within a deep foundation pit during excavation according to claim 1, characterized in that, The sealing cylinder includes a cylinder body, an upper end cover that is detachably and sealingly connected to the upper end of the cylinder body, and a lower end cover that is detachably and sealingly connected to the lower end of the cylinder body. The wire passage hole is provided on the lower end cover, and the wires of the acquisition circuit board are sealed and passed through the wire passage hole.

3. The method for monitoring pore pressure of soil within a deep foundation pit during excavation according to claim 2, characterized in that, The upper end cap is detachably inserted into the upper end of the cylinder. Several upper end cap fixing bolts pass through the cylinder and are threaded into the upper end cap threaded holes on the upper end cap. The upper end cap fixing bolts are distributed circumferentially along the cylinder. The lower end cap is detachably inserted into the lower end of the cylinder. Several lower end cap fixing bolts pass through the cylinder and are threaded into the lower end cap cylinder side threaded holes on the lower end cap. The lower end cap fixing bolts are distributed circumferentially along the cylinder.

4. The method for monitoring pore pressure of soil within a deep foundation pit during excavation according to claim 3, characterized in that, The upper end cover has two sealing grooves on its circumference where it is inserted into the cylinder. The upper end cover is fitted with two sealing rings located in the two sealing grooves, which seal the upper end cover to the cylinder. The lower end cover has two sealing grooves on its circumference where it is inserted into the cylinder. The lower end cover is fitted with two sealing rings located in the two sealing grooves, which seal the lower end cover to the cylinder.

5. A method for monitoring pore pressure of soil within a deep foundation pit during excavation, as described in claim 2, 3, or 4, characterized in that... The lower end of the wire-gathering seat is provided with an end wall, and the end wall is provided with a threaded hole. The pore water pressure gauge is provided with a threaded head, and the wire of the pore water pressure gauge is led out from the end face of the threaded head. The threaded head is threadedly connected to the threaded hole. The diameter of the part of the lower end cover that passes through the cylinder is smaller than the diameter of the lower end cover. The lower end cover is detachably inserted into the wire-gathering seat. Several wire-gathering seat fixing bolts pass through the wire-gathering seat and are threadedly connected to the lower end cover portion of the wire-gathering seat side threaded hole on the lower end cover.

6. A method for monitoring pore pressure of soil within a deep foundation pit during excavation, as described in claim 1, 2, 3, or 4, characterized in that... The outer end face of the upper cover is provided with a threaded hole for installing the suspension line; in the third step, the threaded head is connected to the suspension line and connected to the threaded hole. The wireless pore water pressure gauge is placed into the pore water pressure gauge installation hole through the suspension line. Soil is filled into the pore water pressure gauge installation hole to cover the wireless pore water pressure gauge and fix it in the required position. The suspension line is dropped into the pore water pressure gauge installation hole, and the soil is filled until the pore water pressure gauge installation hole is filled.

7. A method for monitoring pore pressure of soil within a deep foundation pit during excavation, as described in claim 1, 2, 3, or 4, characterized in that... The wires of the acquisition circuit board are connected to one end of the waterproof cable, and the waterproof cable is sealed in the wire hole. The wires of the pore water pressure gauge are connected to the other end of the waterproof cable. The wire hole is located at one end of the wire concentrator and has a large diameter section. An elastic sealing ring is installed in the large diameter section. The elastic sealing ring seals the waterproof cable to the wire hole. A step is formed between the large diameter section and the wire hole.

8. The method for monitoring pore pressure of soil within a deep foundation pit during excavation according to claim 7, characterized in that, The elastic sealing ring, through a sealing strip formed by adhesive, seals the threaded portion within the wire hole. This improves the sealing reliability between the sealing ring and the large-diameter section.

9. A method for monitoring pore pressure of soil within a deep foundation pit during excavation, as described in claim 7, characterized in that... The threading hole is a straight hole. At one end of the large-diameter section, there is an annular blade extending circumferentially along the threading hole. The cross-section of the annular blade is triangular. The annular blade protrudes from the step. The inner circumferential surface of the annular blade and the circumferential surface of the threading hole are located on the same cylindrical surface. The cutting edge direction of the annular blade is the same as the center line direction of the threading hole. The surface of the waterproof cable is provided with an insulating plastic layer. The diameter of the waterproof cable is larger than the diameter of the threading hole.

10. A method for monitoring pore pressure of soil within a deep foundation pit during excavation, as described in claim 7, characterized in that... The conductive core of the waterproof cable has a wiring hole with a larger inner end and a smaller outer end on one end face of the wire base. The end of the wire of the pore water pressure gauge is knotted to form a clip that can pass into the wiring hole. The clip is inserted into the wiring hole, and the wiring hole is filled with conductive adhesive to form a clip head. The clip head bonds the wire of the pore water pressure gauge into the wire hole.

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