Device and method for eliminating excess pore water pressure around underwater static pressure pipe pile

Abstract

The invention discloses a device and a method for eliminating water pressure of an ultra-static pore around an underwater static pressure pipe pile. The device comprises a radial drainage channel, an axial drainage channel and a synchronous synergistic unit, the radial drainage channel is arranged on the outer wall of the pipe pile and used for radially guiding and discharging ultra-static pore water in soil around the pile to a free water area. The axial drainage channel comprises an in-pile guide drainage pipe and an overwater pumping drainage system and is used for pumping and draining pore water near the lower end of the pipe pile upwards through a hollow cavity of the pipe pile; the synchronous synergy unit comprises a magnetic field excitation unit, an electrode system, a power supply and a controller. The technical problem that in the prior art, hole pressure is relieved mainly through measures such as press-in force rate control, sand well arrangement or vacuum drainage, but hole pressure is still difficult to dissipate quickly in a soil body with an extremely low permeability coefficient under the underwater condition is solved.

Description

Technical Field

[0001] This invention belongs to the field of basic engineering and soft soil treatment technology in near-shore or river and lake areas, specifically relating to a device and method for eliminating excess pore water pressure around underwater static pressure pipe piles during construction. Background Technology

[0002] When constructing underwater static pressure pipe piles in soft clay or silty soil, the radial soil squeezing effect of the pile causes severe shear dilation / contraction of the soil near the pile, leading to a sharp increase in pore water pressure and the formation of excess pore water pressure. The pore pressure in saturated soft soil dissipates slowly, and the bearing capacity of the pipe pile increases slowly over time. If the excess pore water pressure cannot be dissipated in time, it will lead to a decrease in the effective stress around the pile, resulting in a short-term artificially high bearing capacity at the lower end of the pipe pile. During pile testing, the excess pore water pressure in the surrounding soil may not have completely dissipated, and the ultimate bearing capacity of the pipe pile may not have been reached. Simultaneously, it causes mutual interference between adjacent piles, promotes negative skin friction in the pile group, increases soil and water disturbance, and increases post-construction settlement and lateral displacement. The excess pore water pressure caused by static pressure pile driving under thixotropic conditions in saturated soft soil will damage the soft soil structure, reducing the soil's bearing capacity. Furthermore, the dissipation of excess pore water pressure will trigger consolidation and settlement of the surrounding soil, resulting in negative friction between the surrounding soil and the pile, causing the actual ultimate bearing capacity to be lower than the bearing capacity calculated from geological survey data. Summary of the Invention

[0003] The purpose of this invention is to provide a device and method for eliminating excess pore water pressure around underwater static pressure pipe piles, which solves the problem that existing technologies mainly rely on measures such as controlling the rate of indentation, setting up sand wells, or vacuum drainage to reduce pore pressure, but these measures are still difficult to quickly dissipate pore pressure in underwater conditions and soils with extremely low permeability.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0005] On the one hand, the present invention provides a device for eliminating excess static pore water pressure around the pile during underwater static pressure pipe pile construction, including a radial drainage channel, an axial drainage channel and a synchronous enhancement unit;

[0006] The radial drainage channel is set on the outer wall of the pipe pile 1 to guide excess pore water in the soil around the pile radially and discharge it to the free water area; the radial drainage channel includes: pile body pressure relief groove 5 and filter-discharge integrated sleeve 10; the pile body pressure relief groove 5 is opened on the outer wall of the pipe pile, and the filter-discharge integrated sleeve 10 covers the outer wall of the pipe pile and communicates with the pile body pressure relief groove 5.

[0007] The axial drainage channel includes: an in-pile guide pipe 11, which is installed in the hollow cavity of the pipe pile. The upper end of the in-pile guide pipe 11 is connected to a water pumping system, which is used to pump the pore water at the lower end of the pipe pile upward through the hollow cavity of the pipe pile; a water-permeable reverse filter assembly 6 is installed at the lower end of the pipe pile.

[0008] The synchronous enhancement unit includes a magnetic field excitation unit 9, an electrode system 16, and a power controller 17. The magnetic field excitation unit 9 and the electrode system 16 are disposed on the outer wall of the pile body. The power controller 17 is used to supply power to and control the magnetic field excitation unit 9 and the electrode system 16. The magnetic field excitation unit 9 is used to excite an alternating magnetic field and induce an electric field in the soil around the pile. The electrode system 16 is used to form a closed conductive loop in the soil to generate an electro-permeability effect, driving pore water to migrate to the radial drainage channel and the axial drainage channel.

[0009] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a pile surface filter integrated sleeve 10 covering the working section 0.5 to 6.0 meters from the top of the pipe pile. From the inside out, it includes an adhesion layer 2, a longitudinal water-conducting layer 3, and a filter layer 4. The longitudinal water-conducting layer 3 has a micro-groove or mesh structure. The filter layer 4 is a composite layer of woven geotextile or non-woven fabric and fine sand.

[0010] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a pile body pressure relief groove 5, which consists of multiple shallow grooves longitudinally opened along the outer wall of the pile body. The grooves are 1-2 mm deep and 4-8 mm wide, arranged in an equidistant spiral pattern or equidistant straight pattern. The pile body pressure relief groove 5 is located between the surface of the pile body and the adhesion layer 2 of the integrated filter sleeve 10.

[0011] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a permeable filter assembly 6 comprising a pressure relief hole or a circumferential shallow groove 8, which is located on the pile shoe 18 of the pipe pile, and a filter layer 14 covering the outer surface of the pile shoe; a one-way check valve 7 is provided between the permeable filter assembly 6 and the internal drainage pipe 11; the permeable filter assembly 6 is filled with gravel with a particle size of 5-20 mm, which forms a high-porosity water collection and pressure equalization layer to collect pore water entering through the pressure relief hole or circumferential shallow groove 8, and, with the cooperation of the filter layer 14, prevents fine soil particles from entering the internal drainage pipe 11, while also reducing the direct impact of water flow on the one-way check valve 7.

[0012] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a one-way check valve 7 that automatically opens and closes based on the difference between the pore water pressure at the lower end of the pipe pile and the opening and closing pressure range of the one-way check valve 7 itself. The one-way check valve 7 is installed between the pile guide pipe 11 and the multi-hole cap pile tip guide head, connected in series along the water flow direction. Its inlet end is connected to the multi-hole cap pile tip guide head, and its outlet end is connected to the pile guide pipe 11, used to control the unidirectional entry of pore water into the pile cavity.

[0013] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a pumping system comprising a pumping pump collection tank 13 and a turbidity meter; the pile-in-pile guide pipe 11 is a PVC or PE pipe with a diameter of 50-75 mm, the lower end of the pile-in-pile guide pipe 11 is connected to the one-way check valve 7, and the upper end is connected to the pumping system via a pumping hose connector 12; the pumping flow rate of the pumping system is 10-40 cubic meters per hour.

[0014] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a magnetic field excitation unit 9, which is a ring or strip electromagnetic coil used to generate an alternating magnetic field with a frequency of 5-50 Hz and a magnetic induction intensity of 10-50 millitalas; and an electrode system 16, which is a corrosion-resistant electrode attached to the outer wall of the pile.

[0015] In a second aspect, the present invention provides a method for eliminating excess pore water pressure around underwater static pressure pipe piles, comprising:

[0016] Step 1: Install the integrated filter sleeve 10 and the pile body pressure relief groove 5 on the outer wall of the pipe pile. The pile body pressure relief groove 5 is treated with sandblasting and primer, and the bonding strength meets ≥0.6 MPa. Seal the end of the pipe pile.

[0017] Step 2: Install a one-way check valve 7 between the permeable filter assembly 6 and the internal drainage pipe 11 of the pile, and conduct a water pressure test. The water pressure test shall meet the following requirements: opening and closing pressure 0.02~0.05 MPa and leakage ≤1%; install a pumping interface, pressure gauge and flow meter at the top of the pipe pile.

[0018] Step 3: Install electromagnetic coils and electrode systems 16 in the corresponding sections of the integrated filter and filtration system 10 on the pile surface, and lead the interface of the electromagnetic coils and electrode systems 16 to the top of the pile.

[0019] Step 4: Install a pore pressure gauge on the side of the pipe pile to monitor the real-time pore pressure, and control the magnetic field and static pressure in a closed loop; seal and insulate the pile body 1 from the electrode system 16.

[0020] Step 5: Underwater positioning and staged control of penetration rate and static pressure.

[0021] Step Six: Simultaneously start the pumping system and the magnetic field excitation unit 9; start the water pump to maintain the negative pressure inside the pile cavity at -5 to -25 kPa or a stable outflow of 5 to 20 m³ / h. When the turbidity is >200 NTU, reduce the backwash water volume; when the pore pressure approaches the control threshold, start the magnetic field excitation unit to form a magnetic field, satisfying a magnetic field strength of 10 to 50 mT, an AC frequency of 10 to 20 Hz, an applied voltage of 20 to 40 V, and energize for 5 to 20 minutes.

[0022] Step 7: After the water pressure reaches the design elevation, close the one-way check valve 7 and stop pumping; seal the inner cavity interface with quick-setting grout and cure for ≥24 hours.

[0023] Step 8: After the pore pressure dissipates to the threshold, proceed with the subsequent construction.

[0024] The aforementioned method for eliminating excess pore water pressure around underwater static pressure pipe piles includes, in step five, the underwater positioning and graded control of the penetration rate static pressure process, which includes: real-time recording of the pressing force of the pile driving equipment, propulsion control, pile group construction interval, and pause and pressure release operations; in the propulsion control, the penetration rate is graded and controlled between 2 and 10 mm / s, and when the peak pore pressure reaches 70% of the set control threshold, it is reduced to 2 to 4 mm / s.

[0025] The beneficial effects of this invention are as follows: This invention provides a device and method for eliminating excess pore water pressure around underwater static pressure pipe piles. By adjusting the magnetic field strength and frequency, it can achieve "directional and controllable" pressure release acceleration, thereby significantly reducing the peak pore pressure by 30-60% and accelerating its dissipation rate by 50-80%. During construction, the indentation force is more stable, the penetration efficiency is improved by 10-25%, and the interval time between pile group construction can be effectively shortened by 4-6 hours. In addition, this method can reduce the development of over-compaction and negative friction, minimize disturbance to adjacent piles, and help control post-construction settlement. Combined with the design of a detachable and replaceable filter sleeve, it further enhances its adaptability and flexibility to different soil layers and construction vessels and equipment. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the pile cross-section structure in Embodiment 1 of the present invention;

[0027] Figure 2 This is a partially enlarged schematic diagram of the pile cross-section structure in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the overall structure of the device in Embodiment 1 of the present invention;

[0029] Figure 4 This is a schematic diagram of the pile shoe structure in Embodiment 1 of the present invention;

[0030] Figure 5 This is a schematic diagram of the permeable reverse filter assembly at the lower end of the pipe pile in Embodiment 1 of the present invention.

[0031] Explanation of reference numerals in the attached drawings: 1-Pile body; 2-Adhesion layer; 3-Longitudinal water guiding layer; 4-Filter layer; 5-Pile body pressure relief trench; 6-Pile lower end permeable reverse filter assembly; 7-One-way check valve; 8-Pile lower end circumferential pressure relief trench; 9-Electromagnetic excitation unit; 10-Integrated filter and discharge sleeve; 11-Pile internal guide pipe; 12-Drainage hose connector; 13-Drainage pump water collection tank; 14-Reverse filter layer; 15-Crushed stone; 16-Electrode system; 17-Power controller; 18-Pile shoe. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0033] Example 1:

[0034] This embodiment provides a device and method for eliminating excess pore water pressure around underwater static pressure pipe piles.

[0035] The device for eliminating excess pore water pressure around underwater static pressure pipe piles includes: a radial drainage channel, an axial drainage channel, and a synchronous enhancement unit.

[0036] The radial drainage channel is set on the outer wall of the pipe pile 1 to guide excess pore water in the soil around the pile radially and discharge it to the free water area; the radial drainage channel includes: a pile body pressure relief groove 5 and an integrated filter and discharge sleeve 10; the pile body pressure relief groove 5 is opened on the outer wall of the pipe pile, and the integrated filter and discharge sleeve 10 covers the outer wall of the pipe pile and is connected to the pile body pressure relief groove 10.

[0037] The axial drainage channel includes: an in-pile drainage pipe 11 and a water-based pumping system, used to pump pore water near the lower end of the pipe pile upwards through the hollow cavity of the pipe pile; the permeable filter assembly 6 is disposed at the lower end of the pipe pile and connected to the in-pile drainage pipe 11, and the water-based pumping system is installed on the water and connected to the in-pile drainage pipe 11; a one-way check valve 7 is provided between the permeable filter assembly 6 and the in-pile drainage pipe 11.

[0038] The synchronous enhancement unit includes: a magnetic field excitation unit 9, an electrode system 16, and a power supply and controller 18; the magnetic field excitation unit 9 and the electrode system 16 are disposed on the outer wall of the pile body, and the power supply controller 17 is used to supply power to and control the magnetic field excitation unit 9 and the electrode system 16. The magnetic field excitation unit 9 is used to excite an alternating magnetic field and induce an electric field in the soil around the pile, and the electrode system 16 is used to form a closed conductive loop in the soil to generate an electro-permeability effect, driving pore water to migrate to the radial drainage channel and the axial drainage channel.

[0039] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a pile surface filter integrated sleeve 10 covering the working section 0.5 to 6.0 meters above the pile tip, comprising an adhesion layer 2, a longitudinal water-conducting layer 3, and a filter layer 4; the longitudinal water-conducting layer 3 has a microgroove or mesh structure with a thickness of 0.5 to 1.5 mm; the filter layer 4 is a composite layer of woven geotextile or non-woven fabric and fine sand with a thickness of 1.5 to 4 mm and an equivalent pore size O95 of 0.07 to 0.20 mm.

[0040] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes six shallow grooves 5 along the pile body direction, with a groove depth of 1-2 mm and a groove width of 4-8 mm, arranged in an equidistant spiral pattern or equidistant straight pattern. The pile body pressure relief grooves 5 are located between the pile body surface and the adhesion layer 2 of the integrated pile surface filter sleeve 10.

[0041] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a permeable filter assembly 6 comprising: a pressure relief hole or circumferential shallow groove 8 and a filter layer 14; the pressure relief hole or circumferential shallow groove 8 is located on the pile shoe 18, and the filter layer 14 covers the surface of the pile shoe; the filter layer 14 is composed of stainless steel mesh and non-woven fabric; the permeable filter assembly 6 is filled with gravel with a particle size of 5-20 mm, which forms a high-porosity water collection and pressure equalization layer to collect pore water entering through the pressure relief hole or circumferential shallow groove 8, and, with the cooperation of the filter layer 14, prevents fine soil particles from entering the pile drainage pipe 11, while also reducing the direct impact of water flow on the one-way check valve 7.

[0042] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a one-way check valve 7 that automatically opens and closes based on the difference between the pore water pressure at the lower end of the pipe pile and the opening and closing pressure range of the one-way check valve 7 itself. The one-way check valve 7 is installed between the pile guide pipe 11 and the multi-hole cap pile tip guide head, connected in series along the water flow direction. Its inlet end is connected to the multi-hole cap pile tip guide head, and its outlet end is connected to the pile guide pipe 11, used to control the unidirectional entry of pore water into the pile cavity. The opening and closing pressure of the one-way check valve 7 is controlled at 0.02~0.05 MPa.

[0043] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes an above-water pumping system comprising: a pumping pump collection tank 13 and a turbidity meter; the pile-mounted drainage pipe 11 is a PVC or PE pipe with a diameter of 50-75 mm, the lower end of which is connected to the one-way check valve 7, and the upper end is connected to the above-water pumping system via a pumping hose connector 12; the above-water pumping system can maintain a single-pile pumping flow rate of 10-40 cubic meters per hour and form a negative pressure of -5 to -25 kPa in the pile cavity.

[0044] The aforementioned device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction includes a magnetic field excitation unit 9, which is a ring or strip electromagnetic coil capable of generating an alternating magnetic field with a frequency of 5-50 Hz and a magnetic induction intensity of 10-50 millitalas; and an electrode system 16, which is a corrosion-resistant electrode attached to the outer wall of the pile.

[0045] The aforementioned device for eliminating excess pore water pressure around underwater static pressure pipe piles has an adjustable power supply and controller that supports DC 0~60V / AC 5~50Hz output, is equipped with current / magnetic field sensors and overcurrent protection, and the single power-on time can be set to 5~20min.

[0046] The method for eliminating excess static pore water pressure around underwater static pressure pipe piles includes:

[0047] Step 1: Install the integrated filter sleeve 10 and the pile body pressure relief groove 5 on the outer wall of the pipe pile. The pile body pressure relief groove 5 is treated with sandblasting and primer, and the bonding strength meets ≥0.6 MPa. Seal the end of the pipe pile.

[0048] Step 2: Install the drain pipe and one-way check valve 7 at the tip of the pipe pile and conduct a water pressure test. The water pressure test shall meet the following requirements: opening and closing pressure 0.02~0.05 MPa and leakage ≤1%. The top of the pile is also equipped with a pumping interface, a pressure gauge and a flow meter interface.

[0049] Step 3: Install electromagnetic coils and electrode systems 16 in the corresponding sections of the integrated filter and filtration sleeve 10 on the pile surface, and lead the interface to the top of the pile.

[0050] Step 4: Install a pore pressure gauge on the side of the pipe pile to monitor the real-time pore pressure, and control the magnetic field and static pressure in a closed loop; completely seal and insulate the pile body 1 from the electrode system 16, and the power supply of the device is equipped with leakage protection and remote short circuit function.

[0051] Step 5: Underwater positioning and staged control of penetration rate and static pressure.

[0052] Step Six: Simultaneously start the pumping system and the magnetic field excitation unit 9; start the water pump to maintain the negative pressure inside the pile cavity at -5 to -25 kPa or a stable outflow of 5 to 20 m³ / h. When the turbidity is >200 NTU, reduce the backwash water volume; when the pore pressure approaches the control threshold, start the magnetic field excitation unit to form a magnetic field, satisfying a magnetic field strength of 10 to 50 mT, an AC frequency of 10 to 20 Hz, an applied voltage of 20 to 40 V, and energize for 5 to 20 minutes.

[0053] Step 7: After reaching the design elevation, close the one-way check valve 7 and stop pumping; seal the inner cavity interface with quick-setting grout and cure for ≥24 hours.

[0054] Step 8: After the pore pressure dissipates to the threshold, proceed with the subsequent construction.

[0055] The aforementioned method for eliminating excess pore water pressure around underwater static pressure pipe piles includes, in step five, the underwater positioning and graded control of the penetration rate static pressure process, which includes: real-time recording of the pressing force of the pile driving equipment, propulsion control, pile group construction interval, and pause and pressure release operations; in the propulsion control, the penetration rate is graded and controlled between 2 and 10 mm / s, and when the peak pore pressure reaches 70% of the set control threshold, it is reduced to 2 to 4 mm / s.

[0056] To ensure construction safety and effectiveness, the penetration process follows the "hole pressure-rate linkage control": 50% to 60% of the initial effective overburden stress σ′v0 at the same depth is used as the hole pressure control line. When Δu is detected to be close to the control line at r=50mm, the penetration rate is reduced and a short pause is made. Simultaneously, pumping and electromagnetic pulses can be used. Only when the hole pressure drops to within 10% of σ′v0 or close to the initial value ±20kPa can the installation of adjacent piles or superstructure components be carried out.

[0057] Example 2:

[0058] This embodiment of the project is located in a coastal mudflat area, mainly composed of soft clay-silty clay layers with local thin layers of silt. A single pile serves as the main load-bearing component of the photovoltaic support structure, with a diameter of 0.30m, a length of 12m, and a designed embedment depth of 6m. The remaining portion is the section exposed above ground and connected to the upper structure. Taking precast concrete pipe piles as an example, 4-6 shallow grooves are machined on the outer wall as pressure relief trenches 5, each 1.0-1.5mm deep and 4-6mm wide. An integrated filter and drainage sleeve 10 (working section length 3.0m) is installed 0.5-3.5m above the pile tip. Its filter layer 4 is made of non-woven / woven geotextile with a surface density of 200-350g / m² and an equivalent pore size of 0.08-0.15mm. The adhesion layer 2 is an epoxy or polyurethane primer, and the longitudinal water-conducting layer 3 is a 0.5-1.0mm microgroove or mesh. A permeable reverse filter assembly 6 is installed at the lower end of the pipe pile, with pressure relief holes of 10-16mm in diameter evenly distributed around the perimeter and a hole spacing of 150-250mm. It is wrapped with a stainless steel mesh and non-woven fabric composite reverse filter layer 14, and filled with 5-10mm graded crushed stone to form a "miniature water filter cap", which is connected to a one-way check valve 7. The drainage pipe 11 inside the pile is made of Φ40-50mm PVC or PE pipe, and the upper end is connected to the drainage pump collection tank 13 through the drainage hose connector 12.

[0059] The specific construction steps are as follows:

[0060] Step 1: Prefabrication and Assembly: Complete the trench processing, seal the filter sleeve 10, and test the water tightness and opening / closing pressure of the guide head and check valve 7;

[0061] Step 2: Positioning and penetration: Initial penetration rate 4-6 mm / s, set hole pressure control line Δu≤0.5-0.6σ′v0;

[0062] Step 3: Synchronous drainage: During the penetration process, maintain a drainage rate of 6-10 m³ / h, and control the negative pressure in the pile cavity at -5 to -20 kPa;

[0063] Step 4: Electromagnetic pulse (optional): When passing through a thin layer of silt or when the pressure fluctuation increases, activate 9 to perform pulse excitation at 10-15Hz, 10-20mT, and 5-10min.

[0064] Step 5: Completion and Sealing: After reaching the design elevation, close the check valve 7, stop pumping, and seal the pile top interface with quick-setting grout. Curing time: ≥24 hours.

[0065] Step Six: Construction of Adjacent Piles and Installation of the Upper Structure: The installation of adjacent piles or supports can only be carried out after the monitored borehole pressure drops to within 10% of σ′v0 or is close to the initial value ±20kPa.

[0066] In this embodiment, after adopting the above-mentioned structure and process, the peak value of the penetration pressure is significantly reduced, the pressure dissipation time is shortened, and the construction efficiency of the pile group interval is improved, thus meeting the requirements of the solar-fishery complementary photovoltaic support for rapid pile formation and stable load bearing.

[0067] The device of this invention is mainly applied in the underwater static pressure pipe pile construction stage. When the pipe pile penetrates saturated soft soil under static pressure, the soil around the pile is compacted and disturbed, generating excess pore water pressure. If this pressure cannot be released in time, it can easily lead to problems such as temporary reduction in soil strength, delayed development of pile-surround friction, and localized water inrush and sand inclusion. To address this, this device constructs a "radial drainage channel" on the outer wall of the pipe pile and an "axial drainage channel" at the lower end of the pipe pile and within the pile cavity. Furthermore, it enhances pore water migration through a synchronous enhancement unit, thereby forming a three-dimensional pressure relief and drainage system of external discharge and internal extraction.

[0068] I. Working principle of radial drainage channel: The integrated filter and drainage sleeve is wrapped around the working section above the pile tip. Its adhesive layer reliably fixes the sleeve to the outer wall of the pipe pile and seals local gaps to prevent flow around and detachment; the filter layer (such as a composite layer of woven / non-woven geotextile and fine sand) is in direct contact with the soil around the pile and undertakes the reverse filtration function, allowing pore water to enter while blocking the migration of fine particles, reducing the risk of siltation in the trench and water guiding layer; the longitudinal water guiding layer adopts a low-resistance channel structure such as micro-groove / mesh, which is connected to the pressure relief trench of the pile body, and collects and guides the pore water entering the sleeve along the direction of the pile body.

[0069] When the pore water pressure around the pile increases, the pore water first passes through the filter layer and enters the longitudinal water-conducting layer under the action of pressure difference, and is then guided into the pressure relief trench of the pile body. The pressure relief trench is arranged along the direction of the pile body (it can be equidistant straight lines or spiral lines), which not only increases the water collection area and shortens the distance for water to flow into the trench, but also provides a continuous external wall drainage "main channel", so that the pore water is discharged upward along the trench (or along the trench to the drainage area connected to the free water area) to the free water area, realizing rapid radial pressure relief and local consolidation of the soil around the pile.

[0070] II. Working principle of axial drainage channel: A permeable filter component is installed at the lower end of the pipe pile. Its pressure relief hole or circumferential shallow groove is opened at the lower end of the pile shoe / pipe pile to form a multi-point water inlet interface near the pile tip, so that pore water in the high head area at the lower end of the pipe pile can enter the interior of the component; the filter layer (such as stainless steel mesh + non-woven fabric composite) is covered on the lower end surface of the pipe pile, which intercepts fine particles while ensuring water permeability; the interior of the component is filled with crushed stone with a particle size of 5~20 mm to form a high permeability crushed stone skeleton and water collection space, providing a stable water passage and supporting the filter layer, reducing head loss and local flow velocity concentration, and reducing sand inclusion and blockage from the source.

[0071] A one-way check valve is installed between the permeable filter assembly and the drainage pipe inside the pile. When the pore water pressure at the lower end of the pipe pile reaches the check valve's opening and closing pressure (0.02~0.05MPa) under the action of the negative pressure of pumping and the head difference, the check valve opens, and the pore water enters the drainage pipe inside the pile through the assembly and is transported upward along the hollow cavity of the pipe pile. When pumping is intermittent or the external head rises, the check valve automatically closes to prevent backflow of water inside the pile, backflow of fine particles, and reverse siltation in the channel, thereby maintaining the one-way stability and long-term unobstructed flow of the axial drainage channel.

[0072] The water-based pumping system connects to the internal drainage pipe of the pile via a pumping hose connector. The pumping pump's collection tank maintains a pumping flow rate of 10~40 m³ / h above the water, creating a negative pressure environment of -5~-25 kPa within the pile's cavity. This negative pressure not only increases the driving force for axial drainage but also works synergistically with radial drainage: pumping from the lower end of the pipe pile reduces the water head at the bottom, promoting the convergence of deep pore water around the pile towards the lower end; simultaneously, a turbidity meter monitors the turbidity of the pumped water, used to determine the effectiveness of the reverse filtration and the pumping stage (e.g., a change from turbid to clear indicates that fine particles are effectively intercepted and the pore water gradually stabilizes).

[0073] III. Mechanism of Synchronous Enhancement Unit: The magnetic field excitation unit, located on the outer wall of the pile, generates an alternating magnetic field of 5~50Hz and 10~50mT, inducing an electric field in the soil surrounding the pile. The electrode system, power supply, and controller together form a closed conductive circuit, causing the pore water in the soil to undergo an electro-permeability effect under the action of the electric field, driving the pore water to migrate from the high-pressure zone to the radial and axial drainage channels. This enhancement mechanism is particularly effective for low-permeability fine-grained soils, improving the mobility and migration rate of pore water without significantly increasing external mechanical energy, further accelerating the dissipation of excess pore water pressure.

[0074] In summary, this device achieves zoned diversion, graded filtration, and integrated pressure relief drainage in the area around the pile and at the bottom of the pipe pile through a combination of "external wall reverse filtration and drainage + reverse filtration and water collection at the bottom of the pipe pile and pumping inside the pile + simultaneous enhancement of electromagnetic / electroosmosis". This forms a continuous, anti-clogging, and controllable drainage path, thereby effectively reducing the excess static pore water pressure around the pile and shortening its dissipation time throughout the static pressure pile driving process.

Claims

1. A device for eliminating excess pore water pressure around underwater static pressure pipe piles during construction, characterized in that, Includes radial drainage channels, axial drainage channels, and synchronous enhancement units; The radial drainage channel is set on the outer wall of the pipe pile (1) to guide the excess pore water in the soil around the pile radially and discharge it to the free water area; the radial drainage channel includes: a pile body pressure relief trench (5) and an integrated filter and discharge sleeve (10); the pile body pressure relief trench (5) is opened on the outer wall of the pipe pile, and the integrated filter and discharge sleeve (10) covers the outer wall of the pipe pile and is connected to the pile body pressure relief trench (5); The axial drainage channel includes: an in-pile guide pipe (11), which is installed in the hollow cavity of the pipe pile. The upper end of the in-pile guide pipe (11) is connected to the water pumping system, which is used to pump the pore water at the lower end of the pipe pile upward through the hollow cavity of the pipe pile; a water-permeable reverse filter assembly (6) is installed at the lower end of the pipe pile. The synchronous enhancement unit includes: a magnetic field excitation unit (9), an electrode system (16), and a power controller (17); the magnetic field excitation unit (9) and the electrode system (16) are disposed on the outer wall of the pile body, and the power controller (17) is used to supply power to and control the magnetic field excitation unit (9) and the electrode system (16). The magnetic field excitation unit (9) is used to excite an alternating magnetic field and induce an electric field in the soil around the pile, and the electrode system (16) is used to form a closed conductive loop in the soil to generate an electro-permeability effect, driving pore water to migrate to the radial drainage channel and the axial drainage channel.

2. The device for eliminating excess static pore water pressure around the pile during underwater static pressure pipe pile construction according to claim 1, characterized in that, The integrated pile surface filter sleeve (10) covers the working section 0.5 to 6.0 meters from the top of the pipe pile, and includes an adhesive layer (2), a longitudinal water guiding layer (3) and a filter layer (4) from the inside to the outside; the longitudinal water guiding layer (3) is a micro-groove or mesh structure; the filter layer (4) is a composite layer of woven geotextile or non-woven fabric and fine sand.

3. The device for eliminating excess static pore water pressure around the pile during underwater static pressure pipe pile construction according to claim 1, characterized in that, The pile body pressure relief groove (5) consists of multiple shallow grooves longitudinally opened along the outer wall of the pile body. The grooves are 1-2 mm deep and 4-8 mm wide, arranged in equidistant spiral patterns or equidistant straight patterns. The pile body pressure relief groove (5) is located between the surface of the pile body and the adhesion layer (2) of the integrated filter sleeve (10).

4. The device for eliminating excess static pore water pressure around the pile during underwater static pressure pipe pile construction according to claim 1, characterized in that, The permeable filter assembly (6) includes a pressure relief hole or a circumferential shallow groove (8), which is opened on the pile shoe (18) of the pipe pile, and the filter layer (14) covers the outer surface of the pile shoe; a one-way check valve (7) is provided between the permeable filter assembly (6) and the pile drainage pipe (11); the permeable filter assembly (6) is filled with gravel with a particle size of 5-20 mm, which forms a high porosity water collection and pressure equalization layer, used to collect pore water entering through the pressure relief hole or circumferential shallow groove (8), and prevent fine soil particles from entering the pile drainage pipe (11) under the cooperation of the filter layer (14), while reducing the direct impact of water flow on the one-way check valve (7).

5. The device for eliminating excess static pore water pressure around the pile during underwater static pressure pipe pile construction according to claim 1, characterized in that, The one-way check valve (7) provides the difference between the pore water pressure at the lower end of the pipe pile and the opening and closing pressure range of the one-way check valve (7) itself to automatically realize the opening and closing of the valve; the one-way check valve (7) is set between the pile guide pipe (11) and the multi-hole cap pile tip guide head, and is installed in series along the water flow direction. Its inlet end is connected to the multi-hole cap pile tip guide head, and its outlet end is connected to the pile guide pipe (11), which is used to control the pore water to enter the pile cavity in one direction.

6. The device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction according to claim 1, characterized in that, The water pumping system includes a pumping pump collection tank (13) and a turbidity meter; the in-pile guide pipe (11) is a PVC or PE pipe with a diameter of 50-75 mm. The lower end of the in-pile guide pipe (11) is connected to the one-way check valve (7), and the upper end is connected to the water pumping system through a pumping hose connector (12); the pumping flow rate of the water pumping system is 10-40 cubic meters per hour.

7. The device for eliminating excess pore water pressure around the pile during underwater static pressure pipe pile construction according to claim 1, characterized in that, The magnetic field excitation unit (9) is a ring or strip electromagnetic coil used to generate an alternating magnetic field with a frequency of 5~50 Hz and a magnetic induction intensity of 10~50 millitalas; the electrode system (16) is a corrosion-resistant electrode attached to the outer wall of the pile body.

8. A method for eliminating excess pore water pressure around underwater static pressure pipe piles, characterized in that, include: Step 1: Install the integrated filter sleeve (10) and the pile body pressure relief groove (5) on the outer wall of the pipe pile. The pile body pressure relief groove (5) is treated with sandblasting and primer. The bonding strength meets ≥0.6 MPa. Seal the end of the pipe pile. Step 2: Install a one-way check valve (7) between the permeable filter assembly (6) and the drainage pipe (11) inside the pile, and conduct a water pressure test. The water pressure test shall meet the following requirements: opening and closing pressure 0.02~0.05 MPa and leakage ≤1%; install a pumping interface, pressure gauge and flow meter at the top of the pipe pile. Step 3: Install electromagnetic coils and electrode systems (16) in the corresponding section of the integrated filter and filtration sleeve (10) on the pile surface, and lead the interface of the electromagnetic coils and electrode systems (16) to the top of the pile; Step 4: Install a pore pressure gauge on the side of the pipe pile to monitor the real-time pore pressure, and control the magnetic field and static pressure in a closed loop; seal and insulate the pile body (1) from the electrode system (16); Step 5: Underwater positioning and staged control of penetration rate and static pressure; Step 6: Simultaneously start the pumping system and the magnetic field excitation unit (9); start the water pump to maintain the negative pressure inside the pile cavity at -5 to -25 kPa or a stable outflow of 5 to 20 m³ / h. When the turbidity is >200 NTU, reduce the backwash water volume. When the pore pressure approaches the control threshold, start the magnetic field excitation unit to form a magnetic field, satisfying a magnetic field strength of 10 to 50 mT, an AC frequency of 10 to 20 Hz, an applied voltage of 20 to 40 V, and energize for 5 to 20 minutes. Step 7: After the water pressure reaches the design elevation, close the one-way check valve (7) and stop pumping; seal the inner cavity interface with quick-setting grout and cure for ≥24 hours; Step 8: After the pore pressure dissipates to the threshold, proceed with the subsequent construction.

9. The method for eliminating excess pore water pressure around underwater static pressure pipe piles according to claim 8, characterized in that, In step five, the underwater positioning and graded control of the penetration rate static pressure process includes: real-time recording of the pressing force of the pile driving equipment, propulsion control, pile group construction interval, and pause and pressure release operations; in the propulsion control, the penetration rate is graded and controlled at 2~10 mm / s, and when the peak pore pressure reaches 70% of the set control threshold, it is reduced to 2~4 mm / s.

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