Liquid nitrogen freezing temperature control inter-pile water stop steel sheet pile system and using method thereof

Abstract

According to the liquid nitrogen freezing temperature control inter-pile water stop steel sheet pile system, U-shaped flanges are arranged on the two sides of each steel sheet pile, the bending directions of the U-shaped flanges of every two adjacent steel sheet piles are opposite, the U-shaped flanges of every two adjacent steel sheet piles are buckled to form a tubular cavity, and the multiple steel sheet piles are connected end to end to define a protective curtain; the liquid nitrogen distribution pipe extends to the bottom of the steel sheet pile in the axial direction of the tubular cavity, liquid nitrogen distribution holes are evenly distributed in the side wall of the liquid nitrogen distribution pipe, and a sealing structure corresponding to the lower portion of the underground water-rich layer is arranged in the liquid nitrogen distribution pipe. Benefited from the efficient freezing effect of the liquid nitrogen, a section of waterproof frozen soil structure is rapidly formed in a water-rich stratum section, a sealing structure is arranged, and the elevation of a liquid nitrogen freezing area can be adjusted according to different water-rich layers, so that the splicing seam of every two adjacent steel sheet piles is sealed through the liquid nitrogen according to different soil body conditions; and the requirement for assembly precision of the steel sheet pile is not high, and therefore wide popularization can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid nitrogen freezing, and in particular relates to a liquid nitrogen freezing temperature-controlled inter-pile water-stop steel sheet pile system and a use method thereof. Background Art

[0002] At present, steel sheet piles are widely used in construction projects due to their simple structure and low price. However, as the construction progresses, water seepage and permeability problems caused by structural changes are inevitable, which have a certain impact on the safety of the project. Therefore, the development and application of liquid nitrogen frozen steel sheet piles can effectively solve the water seepage and permeability problems of traditional steel sheet piles during use and ensure construction safety, which is of great significance.

[0003] At present, my country's steel sheet water stop piles rely on their cofferdam effect and pile body sealing to prevent water from entering. This traditional method relies on the structure of the steel sheet piles themselves, has high quality requirements, and has limited water stop effect. In water-rich strata, moisture in the soil will still pass through the water stop barrier through the connection gaps between the steel sheet piles, causing a certain impact on construction. Although the joints between the steel sheet piles are designed to be waterproof, in actual construction, there may be a risk of water leakage in the joints, especially in projects with high water pressure, and additional waterproofing measures need to be taken to ensure sealing.

[0004] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art. The present invention provides a liquid nitrogen freezing temperature-controlled inter-pile water-stop steel sheet pile system and a method for using the same.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A liquid nitrogen freezing temperature-controlled inter-pile water-stopping steel sheet pile system, comprising:

[0008] Steel sheet piles, each of which is provided with a U-shaped flange on both sides, the U-shaped flanges of two adjacent steel sheet piles are bent in opposite directions, the U-shaped flanges of two adjacent steel sheet piles are buckled together to form a tubular cavity, and a plurality of the steel sheet piles are connected end to end to form a protective curtain;

[0009] A liquid nitrogen distribution pipe, the liquid nitrogen distribution pipe extending along the axial direction of the tubular cavity to the bottom of the steel sheet pile, a side wall of the liquid nitrogen distribution pipe is provided with evenly distributed liquid nitrogen distribution holes, and a sealing structure corresponding to the bottom of the underground water-rich layer is provided inside the liquid nitrogen distribution pipe;

[0010] The liquid nitrogen distribution pipe is correspondingly connected to a liquid nitrogen storage tank so as to guide the liquid nitrogen to the U-shaped flange through the liquid nitrogen distribution hole, and conduct it through the steel sheet piles to form a closed liquid nitrogen water-stopping curtain on both sides thereof.

[0011] Preferably, the plurality of liquid nitrogen distribution pipes are connected to a liquid nitrogen main pipe via solenoid valves respectively, and the liquid nitrogen main pipe is connected to the corresponding liquid nitrogen storage tank via a liquid nitrogen compression pump.

[0012] Preferably, linear temperature sensors are provided on both sides of the steel sheet piles, and the length of the linear temperature sensors matches the length of the steel sheet piles;

[0013] A displacement meter corresponding to the steel sheet pile is provided to monitor the horizontal displacement of the steel sheet pile.

[0014] Preferably, the linear temperature sensor and the array displacement meter are connected to signal transmitters respectively, the signal transmitters are communicatively connected to a controller, and the controller is connected to the solenoid valve and the liquid nitrogen compression pump respectively.

[0015] Preferably, the sealing structure is a hot melt adhesive, and its axial length is not less than 5 cm.

[0016] Preferably, the steel sheet piles include multiple sections spliced ​​along the longitudinal direction, and two adjacent sections of the steel sheet piles are fixed by bolts.

[0017] A method for using a liquid nitrogen freezing temperature-controlled pile water-stop steel sheet pile system, wherein freezing and water-stopping are performed by using any of the liquid nitrogen freezing temperature-controlled pile water-stop steel sheet pile systems, comprising the following steps:

[0018] Step S1, hoisting the steel sheet pile to the construction area, and strengthening the U-shaped flange during the hoisting process;

[0019] Step S2, determine the position and depth of the steel sheet piles around the foundation pit according to the construction drawing, the pile positioning axis should be offset 5 to 10 cm to the land side, the pile positioning axis should be 20 cm away from the construction area, and a rectangular area is formed by multiple steel sheet piles;

[0020] Step S3, by distributing the double-sided guide frames in parallel on both sides of the steel sheet pile positioning axis, driving a guide pile every 2 to 4 meters, and attaching a guide beam between the guide pile and the steel sheet pile;

[0021] Step S4, determining the underground water-rich layer according to geological data, setting the range of liquid nitrogen freezing, and setting a sealing structure below the underground water-rich layer in the liquid nitrogen distribution pipe;

[0022] Step S5, check the parameters of the liquid nitrogen storage tank. When excavating above the water-rich soil layer, supply liquid nitrogen into the liquid nitrogen distribution pipe through the liquid nitrogen compression pump, and reduce and maintain the liquid nitrogen delivery power after forming a liquid nitrogen water-stop curtain;

[0023] Step S6, continue to excavate the foundation pit, and monitor the temperature of the liquid nitrogen water-stop curtain and the horizontal displacement of the steel sheet piles at the same time. When the construction reaches the floor layer, stop the liquid nitrogen delivery, melt the frozen soil through self-heating of the soil, and pull out the steel sheet piles.

[0024] Preferably, after the pile driving positioning axis is determined, the starting point and the end point of the pile driving are set on site, the observation point of the positioning axis is set on its extension line, and an array displacement meter is set at the observation point to monitor the horizontal displacement of the steel sheet pile;

[0025] When the horizontal displacement of the steel sheet pile is greater than 2% of the pile length, liquid nitrogen is transported to the liquid nitrogen distribution pipe at maximum power.

[0026] Preferably, the sealing structure is a hot melt adhesive having an axial length of not less than 5 cm, and a hot melt gun is used to inject the hot melt adhesive through the liquid nitrogen distribution holes on the side wall of the liquid nitrogen distribution tube to form a seal inside the liquid nitrogen distribution tube.

[0027] Beneficial effects: Thanks to the efficient freezing effect of liquid nitrogen, a waterproof frozen soil structure is quickly formed in the water-rich stratum section. A sealing structure is set up, and the elevation of the liquid nitrogen freezing area can be adjusted for different water-rich layers to cope with different soil conditions. The joints between two adjacent steel sheet piles are sealed by liquid nitrogen, and the assembly accuracy of the steel sheet piles themselves is not high, so it can be widely promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0029] Figure 1 This is a schematic diagram of the top view of the liquid nitrogen frozen steel plate in the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of the liquid nitrogen frozen steel sheet pile in the present invention;

[0031] Figure 3 It is a schematic diagram of the arrangement of the liquid nitrogen freezing section in the present invention;

[0032] Figure 4 It is a soil temperature curve diagram in a specific embodiment of the present invention;

[0033] In the figure: 1. Liquid nitrogen storage tank; 2. Liquid nitrogen compression pump; 3. Steel sheet pile; 4. Liquid nitrogen distribution pipe; 5. Liquid nitrogen main pipe; 6. Quick interface; 7. Linear temperature sensor; 8. Signal transmitter; 9. Ground breaking quilt; 10. Bolt; 11. Upper soil layer; 12. Water-rich soil layer; 13. Lower soil layer; 14. Rock layer; 15. Solenoid valve; 16. Sealing structure. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0035] In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, they can be fixed connections or detachable connections; they can be directly connected or indirectly connected through intermediate components. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0037] Conventional steel sheet piles 3 are sealed and fixed to each other by the flanges on adjacent sides to stop water. The advantage is that the structure is simple, but the production process of the steel sheet piles 3 is relatively high. During storage and transportation, attention should be paid to anti-corrosion and ensuring the tightness of the interface. Therefore, it is not conducive to wide application, and this connection method is inconvenient to turn corners, that is, this structure cannot form a closed rectangle. If it cannot be connected at the transition point, it will not only affect the integrity of the steel sheet piles 3, but also lose the anti-seepage effect at the corners. Therefore, an improved technical solution is needed to address the above-mentioned deficiencies in the existing technology.

[0038] like Figure 1-4 As shown, the present application provides a liquid nitrogen freezing temperature-controlled pile water-stop steel sheet pile 3 system, including steel sheet piles 3 and liquid nitrogen distribution pipes 4. The steel sheet piles 3 can be straight plates or groove-shaped structures, such as trapezoidal grooves, so as to increase the structural strength of the steel sheet piles 3. The steel sheet piles 3 can be galvanized steel plates, or have an anti-rust layer coated on the outside.

[0039] The steel sheet piles 3 are provided with U-shaped flanges on both sides, and the U-shaped flanges are formed into a semicircular structure by U-shaped flipping. The U-shaped flanges on both sides of the same steel sheet pile 3 can be in the same direction or in opposite directions. No matter which form, in the multiple steel sheet piles 3 spliced ​​with each other, the bending directions of the U-shaped flanges of two adjacent steel sheet piles 3 are opposite to each other, and the U-shaped flanges of two adjacent steel sheet piles 3 are interlocked with each other to form a tubular cavity by splicing. The diameter of the tubular cavity is the corresponding diameter of the U-shaped flange, and the diameter is larger than the outer diameter of the liquid nitrogen distribution pipe 4. Multiple steel sheet piles 3 are connected end to end to form a protective curtain. The protective curtain can be square, circular or other shapes, and is prefabricated and assembled according to the shape of the part to be excavated. The liquid nitrogen distribution pipe 4 is set along the axial direction of the tubular cavity, and the liquid nitrogen distribution pipe 4 extends along the axial direction of the tubular cavity to At the bottom of the steel sheet pile 3, the upper end of the liquid nitrogen distribution pipe 4 extends upward from the upper edge of the steel sheet pile 3, and the length of the liquid nitrogen distribution pipe 4 exposed upward from the steel sheet pile 3 is 1m. Evenly distributed liquid nitrogen distribution holes are provided on the side wall of the liquid nitrogen distribution pipe 4, and the liquid nitrogen distribution holes are located inside the soil layer. The uppermost liquid nitrogen distribution hole is below 0.5 meters below the ground. A sealing structure 16 corresponding to the underground water-rich layer is provided in the liquid nitrogen distribution pipe 4; the soil layers above the sealing structure 16 are all liquid nitrogen freezing areas, and the liquid nitrogen is transported from the liquid nitrogen distribution hole to the U-shaped flange, thereby sealing the gap between the two U-shaped flanges that are buckled together by freezing, and then the heat is conducted to the steel sheet pile 3, and a closed liquid nitrogen water-stop curtain is formed with the steel sheet pile 3 as a medium, and the liquid nitrogen water-stop curtain forms a frozen soil layer on both sides of the steel sheet pile 3.

[0040] Liquid nitrogen is stored in the liquid nitrogen storage tank 1. A pressure gauge is provided at the outlet of the liquid nitrogen storage tank 1 to display the internal liquid nitrogen reserves. The liquid nitrogen distribution pipe 4 is correspondingly connected to the liquid nitrogen storage tank 1 to guide the liquid nitrogen to the U-shaped flange through the liquid nitrogen distribution hole to form a liquid nitrogen water-stop curtain.

[0041] In an optional embodiment, the liquid nitrogen main pipe 5 can be an annular tube (circular ring or square ring) or a tube body with closed ends and bent into a ring shape. The liquid nitrogen main pipe 5 is connected to the outlet of the liquid nitrogen storage tank 1 through a main valve. The shape of the liquid nitrogen main pipe 5 is adapted to the shape of the steel sheet piles 3. The liquid nitrogen main pipe 5 is provided with interfaces corresponding to each liquid nitrogen distribution pipe 4. Multiple liquid nitrogen distribution pipes 4 are respectively connected to the liquid nitrogen main pipe 5 in a detachable manner through solenoid valves 15. The outlet of the liquid nitrogen storage tank 1 is provided with a solenoid valve 15. The liquid nitrogen main pipe 5 is connected to the liquid nitrogen storage tank 1 through a liquid nitrogen compression pump 2, thereby realizing liquid nitrogen transportation through the liquid nitrogen compression pump 2.

[0042] In this embodiment, a linear temperature sensor 7 is used to monitor the temperature of the liquid nitrogen water-stop curtain. The length of the linear temperature sensor 7 is adapted to the length of the steel sheet pile 3. A linear temperature sensor 7 is provided on both sides of each steel sheet pile 3, and the linear temperature sensor 7 is close to the steel sheet pile 3.

[0043] After the pile positioning axis is determined, the starting point and end point of the pile driving can be set on site, and the observation point of the positioning axis is set on its extension line. The horizontal displacement of the steel sheet pile 3 is monitored by a displacement meter at each observation point. Specifically, if it is found that the steel sheet pile 3 exceeds 2% of the pile length due to different soil pressures on both sides, the power of the liquid nitrogen compression pump 2 is adjusted to the maximum power at the same time to make the liquid nitrogen freezing reach the maximum rate.

[0044] In an optional embodiment, the linear temperature sensor 7 and the array displacement meter are connected to a signal transmitter 8, and the signal transmitter 8 is communicatively connected to a controller. The controller may be a PLC, a handheld monitor, a mobile terminal (such as a mobile phone) or a PC. The signal transmitter 8 is connected to the controller via a network, and remote monitoring can be realized, so that construction personnel can replenish liquid nitrogen in time. The controller is connected to a solenoid valve 15 and a liquid nitrogen compression pump 2, and can intelligently control the liquid nitrogen compression pump 2 and the solenoid valves 15 corresponding to each liquid nitrogen distribution pipe 4 according to the displacement and temperature monitoring results, thereby reducing liquid nitrogen loss, improving the stability of the water-stop curtain, and real-time monitoring of the structural morphology changes of the steel sheet piles 3 during engineering construction. By increasing the amount of liquid nitrogen added, the problem of water leakage and seepage caused by gaps in the interface during construction or uneven temperature in the soil layer of the steel sheet piles 3 can be quickly solved.

[0045] In an optional embodiment, the steel sheet pile 3 passes downward through the upper soil layer 11 and then through the water-rich soil layer 12 and then extends into the lower soil layer 13. The length extending to the lower soil layer 13 can be about 2m, and generally should not extend into the rock layer 14. The sealing structure 16 is hot melt adhesive, and its axial length is not less than 5cm. A hot melt gun is used to inject the liquid nitrogen into the liquid nitrogen distribution pipe 4 through the liquid nitrogen distribution hole on the side of the liquid nitrogen distribution pipe 4, and then the liquid nitrogen distribution pipe 4 is manufactured according to the elevation of the water-rich soil layer.

[0046] In an optional embodiment, the steel sheet pile 3 includes multiple sections spliced ​​along the longitudinal direction, which can be 3-4 sections, and the length of each section can be 3-4 meters. The adjacent sections of the steel sheet pile 3 overlap each other, and the overlapping part can be 10-20 cm. The overlapping part is provided with screw holes for fixing by bolts 10.

[0047] In an optional embodiment, the present application further provides a method for using a liquid nitrogen freezing temperature-controlled pile water-stop steel sheet pile 3 system, wherein freezing and water-stopping by using any of the above liquid nitrogen freezing temperature-controlled pile water-stop steel sheet pile 3 systems comprises the following steps:

[0048] Step S1, use the three-point lifting method to lift the steel sheet pile 3 to the construction area, and strengthen the U-shaped flange during the lifting process; Step S2, determine the position and depth of the steel sheet pile 3 around the foundation pit according to the construction drawing, the pile positioning axis should be offset 5 to 10 cm to the land side, and the pile positioning axis should be 20 cm away from the construction area. A rectangular area is formed by multiple steel sheet piles 3 to enclose the foundation pit to be excavated. Step S3, a double-sided guide frame is arranged in parallel on both sides of the steel sheet pile 3 positioning axis, a guide pile is driven every 2 to 4 meters, and a guide beam is attached between the guide pile and the steel sheet pile 3. The double-sided guide frame can be a double-sided purlin bracket. Step S4, determine the underground water-rich layer and construction requirements according to geological data, so as to determine the freezing range of liquid nitrogen freezing, seal the liquid nitrogen distribution pipe 4 according to the freezing length, and set a sealing below the underground water-rich layer in the liquid nitrogen distribution pipe 4. Sealing structure 16, the area above the sealing structure 16 is a freezing area. The steel sheet piles 3 and the liquid nitrogen distribution pipe 4 are made of metal and can efficiently transfer heat. The temperature of the surrounding soil drops rapidly, and then the moisture in the soil can be quickly frozen to form a closed and impermeable ice-soil structure. A water-stopping curtain is formed for the underground water-rich layer, thereby isolating the water in the soil outside the structure and preventing water from seeping into the foundation pit. Step S5, check the parameters of the liquid nitrogen storage tank 1 through a pressure gauge. As the foundation pit is excavated, when the foundation pit is excavated above the water-rich soil layer, liquid nitrogen is supplied to the liquid nitrogen distribution pipe 4 at full power through the liquid nitrogen compression pump 2. After the liquid nitrogen water-stopping curtain is formed, the liquid nitrogen delivery power is reduced and maintained; Step S6, continue to excavate the foundation pit, and monitor the temperature of the liquid nitrogen water-stopping curtain and the horizontal displacement of the steel sheet piles 3 at the same time. When the construction reaches the floor layer, stop the liquid nitrogen delivery, melt the frozen soil through the self-heating of the soil, and pull out the steel sheet piles 3.

[0049] In an optional embodiment, during the construction of the steel sheet pile 3, after the pile positioning axis is determined, the starting point and end point of the pile are set on site, the observation point of the positioning axis is set on its extension line, and an array displacement meter is set at the observation point to monitor the horizontal displacement of the steel sheet pile 3; when the horizontal displacement of the steel sheet pile 3 is greater than 2% of the pile length, liquid nitrogen is transported to the liquid nitrogen distribution pipe 4 at maximum power, thereby ensuring the consolidation capacity of the water-stop curtain and improving stability. The sealing structure 16 is hot melt adhesive, and the hot melt adhesive is injected using a hot melt gun before the liquid nitrogen distribution pipe 4 is installed, and the hot melt adhesive solidifies inside the liquid nitrogen distribution pipe 4 to form a seal. The axial length of the hot melt adhesive can be 5-10cm.

[0050] In an optional embodiment, actual construction guidance is provided based on the above system and usage method. For example, a certain construction project requires excavation of a 30m×10m×4.1m foundation pit. After detection, the underground water-rich layer is located at 6m to 9.6m below the natural ground (during the survey period) and the standard penetration test N value is below 25 in the soft stratum; the steel sheet pile 3 uses a U-shaped steel sheet pile 3 with a cross-sectional size of 500mm×110mm and a length of 4m. The upper and lower parts are connected by a bolt 10 connection method. A total of 3 steel sheet piles 3 are spliced ​​into a steel sheet pile 3 with a length of 12m; the foundation pit excavation mainly adopts the slope excavation method, the first layer of miscellaneous fill is completely excavated, and the second layer of medium and coarse sand is sloped at 1:0.5 to 1:1. In order to prevent surface water from infiltrating or flowing back into the foundation pit, a 1000mm×1000mm drainage ditch is constructed around the foundation pit; the specific construction operation of the liquid nitrogen steel sheet pile 3 system is as follows:

[0051] Use 3-point lifting, and the lifting points are set at the 1m, 2m, and 3m positions of the steel sheet piles 3 in sequence, so that the bending moment caused by the deadweight can be minimized. When the steel sheet piles 3 need to be stacked, sleepers should be inserted between every two layers of steel sheet piles 3, and the total stacking height cannot exceed 2m. In order to facilitate the binding of wire ropes, the spacing between adjacent steel sheet piles 3 should be between 20cm and 50cm. When the steel sheet piles 3 are lifted, care should be taken to prevent plastic deformation caused by deadweight, and it is necessary to reinforce the U-shaped flange.

[0052] According to the construction drawings, the position and depth of the steel sheet piles 3 are determined around the foundation pit. Since the soil pressure generated by the backfill may cause the steel sheet piles 3 to tilt forward, the pile positioning axis should be offset 5 to 10 cm to the land side. The pile positioning axis is 20 cm away from the construction area, forming a rectangular area of ​​30.6 m × 12.6 m. After the pile positioning axis is determined, the starting and end points of the piles can be set on site, and the observation point of the positioning axis is set on its extension line.

[0053] On both sides of the parallel steel sheet pile 3 positioning axis, a guide pile is driven in every 2 to 4 meters, and a guide beam is attached between the guide pile and the steel sheet pile 3; in addition, an integral guide frame made into a frame structure can also be used; the guide frame and guide beam are usually made of H-shaped steel, and its size (section height) is 250 to 350 mm. According to the site conditions, a single-sided guide frame (i.e., a single-sided purlin bracket) can also be used; but when the section of the driven steel sheet pile 3 is large and the pile length is long, a clamping guide frame will be used in principle, and the spacing between the guide beams on both sides should be the section height of the steel sheet pile 3 wall plus 2 to 5 cm, that is, 13 to 16 cm.

[0054] According to geological data, the underground aquifer is 6m to 9.6m below the surface. In order to achieve efficient water stopping, the liquid nitrogen water-stopping barrier needs to be at least 0.5m above and below the aquifer. Therefore, the lower part of the liquid nitrogen water-stopping barrier is set at 5.5m to 10.1m below the surface. A portion of 1m of steel sheet piles 3 are exposed on the ground. The three 4m steel sheet piles 3 are numbered as No. 1, 2, and 3 steel sheet piles 3 in the order of being buried in the ground. At 0.9m from the bottom of No. 1 steel sheet pile 3, a hot melt gun is used to inject a 5cm hot melt adhesive segment through the flower holes on the surface of the liquid nitrogen distribution pipe 4, and all the upper parts of the hot melt adhesive segment are frozen. In this way, the range of liquid nitrogen freezing can be set more flexibly, which is convenient for achieving the purpose of water stopping under different working conditions. The lower end of the liquid nitrogen distribution pipe 4 is provided with a soil-breaking cap 9 with a tip pointing to the soil layer for easy insertion into the soil layer.

[0055] The steel sheet pile 3 needs to be straightened to ensure that it is straight and not twisted and deformed. The pile driver uses a static pressure pile driver. Compared with the vibration hammer construction, it can transmit the force to the front end of the pile more accurately and effectively. The construction process only requires a crane to assist and cooperate, which meets the construction environment with strict noise control and limited site. First, the reaction base is weighted to provide the pressure for the first 1 to 4 piles. The steel sheet pile 3 is lifted by a crane and sent into the static pressure pile driver. When the upper edge of the No. 1 steel sheet pile 3 is 0.5m away from the upper surface of the static pile driver, the No. 2 steel sheet pile 3 is hoisted and aligned with the No. 1 steel sheet pile 3, and the liquid nitrogen distribution pipe 4 is aligned with the interface. The liquid nitrogen distribution pipe 4 at the upper end of the No. 1 steel pipe pile is inserted into the lower end of the liquid nitrogen distribution pipe 4 of the No. 2 steel sheet pile 3 to form a continuous closed structure. Start to connect the No. 2 steel sheet pile 3, pay attention to aligning the vertically connected steel sheet piles 3, and use bolts 10 to connect, the same as the connection between No. 2 and No. 3 below. The pile driver moves on its own to complete the pressing of all the steel sheet piles 3. After the steel sheet piles 3 are pressed in and closed, the earth is excavated and the water is lowered to about 1m below the support to be installed to install the inner support. After excavation and lowering the water to the designed elevation, the cushion layer concrete is poured. After the concrete reaches the strength, the main project is constructed. According to the geological conditions that may occur in different areas, the static pressure pile driver can be equipped with different auxiliary devices to ensure the smooth pressing of the steel sheet piles 3.

[0056] According to the axis network of the construction drawing, the pile positions are numbered, and the pressure and temperature in the liquid nitrogen storage tank 1 are checked to see if they are within the specified range. After the inspection, the matching female buckle is tightened on the threaded port of the liquid nitrogen distribution pipe 4, and the male buckle of the quick interface 6 is installed on the liquid nitrogen main pipe 5. In order to increase the tightness of the structure, an appropriate amount of liquid raw tape can be applied to the thread of the quick interface 6 before tightening. The liquid raw tape can effectively increase the tightness of the interface under anaerobic conditions; the installer wears anti-cold gloves, connects the input end of the liquid nitrogen compression pump 2 to the liquid nitrogen storage tank 1, and the output end is connected to the liquid nitrogen main pipe 5 through the internal thread connector; after ensuring that the male buckle and the female buckle are locked, open the corresponding solenoid valve 15, start the inspection of the master control transmitter, and report the corresponding steel sheet pile 3 number to the monitoring personnel. At this time, the monitoring personnel at a distance check whether the handheld monitor can detect the master control transmitter signal, and enter the corresponding steel sheet pile 3 number in the handheld monitor, which can efficiently monitor the real-time working conditions of liquid nitrogen freezing.

[0057] The liquid nitrogen compressor 2 performs liquid nitrogen freezing at maximum power. After freezing for 2 hours, a relatively stable ice-soil structure can be formed. At this time, the liquid nitrogen delivery power is reduced to the maintenance rate (meaning that liquid nitrogen can stabilize the soil in a frozen state at this rate), and the foundation pit is continued to be excavated. At the same time, the internal temperature is monitored by the built-in linear temperature sensor 7. The soil freezing temperature T f To ensure the tightness of the frozen soil, the lower limit temperature T is set to -6℃. D The freezing limit temperature is -8℃. U -5℃. When the frozen soil temperature reaches -8℃, reduce the liquid nitrogen delivery. At this time, a tight and impermeable frozen soil layer has been formed around the steel sheet pile 3. Reduce the power of the liquid nitrogen compression pump 2 to 50% of the maximum power. At this time, the liquid nitrogen delivery rate can keep the soil stable and fluctuate within [-8℃, -5℃] under the current environment. As the soil environment changes during the excavation process, the soil insulation performance will be reduced, causing the temperature of the frozen soil to rise. The internal temperature of the soil is monitored by sensors at all times. When the temperature rises back to -5℃, start to increase the liquid nitrogen freezing, increase the power of the liquid nitrogen compression pump 2 to 80% of the maximum power, and continue for 1h. When the temperature drops close to -8℃, restore the power of the liquid nitrogen compression pump 2 to 50% of the maximum power to maintain the soil temperature within a reasonable range. On the basis of maintaining the airtightness of the frozen soil, reduce the loss of liquid nitrogen. When some liquid nitrogen freezing piles need to adjust the liquid nitrogen delivery rate, they can be controlled separately by adjusting the opening and closing size of the solenoid valve 15 at the liquid nitrogen delivery pipe. The freezing process of each pile position corresponds to the flow range [L0, L1]. During the freezing process, the above measures are taken according to the internal temperature cycle of the frozen soil until the freezing process is completed.

[0058] During the construction process, the horizontal displacement of the steel sheet pile 3 is constantly monitored by using an array displacement meter. If the horizontal displacement L of the steel sheet pile 3 exceeds the specification due to the different soil pressures on both sides, that is, it is greater than 2% of the pile length, that is, 24 cm, the electromagnetic valve 15 at the liquid nitrogen delivery pipe should be fully opened immediately, and the power of the liquid nitrogen compression pump 2 should be adjusted to the maximum power to make the liquid nitrogen freeze at the maximum rate. At this time, the lower limit temperature T D To -15℃, sufficient strength is formed, the surrounding soil is frozen to the maximum extent, and a stable ice-soil structure is formed, which can ensure the stability of the steel sheet pile 3 to a certain extent. The liquid nitrogen surplus is monitored by the pressure gauge on the liquid nitrogen storage tank 1, and the liquid nitrogen is replaced in time to ensure sufficient liquid nitrogen supply.

[0059] When the main construction is completed to the floor layer, disconnect the liquid nitrogen supply, remove the liquid nitrogen delivery pump, and melt the previously frozen soil through heat conduction of the soil, weakening the connection between the soil and the steel sheet piles 3. During this period, the temperature around the steel sheet piles 3 can be monitored in real time through a handheld monitor. When the temperature reaches above 0°C for 12 hours, the steel sheet piles 3 can be pulled out. When pulled out, the connection between the liquid nitrogen distribution pipes 4 will be separated due to the force between the connected steel sheet piles 3. Stack the steel sheet piles 3 as required, use a high-pressure water gun to rinse the steel sheet piles 3, remove the surface soil and other debris, find the hot melt adhesive seal, use a thin wire to pierce the hot melt adhesive segment or use alcohol, gasoline and other organic solvents to soak the hot melt adhesive segment to separate it from the liquid nitrogen distribution pipe 4.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A liquid nitrogen freezing temperature control pile water-stop steel sheet pile system, characterized in that: include: Steel sheet piles, each of which is provided with a U-shaped flange on both sides, the U-shaped flanges of two adjacent steel sheet piles are bent in opposite directions, the U-shaped flanges of two adjacent steel sheet piles are buckled together to form a tubular cavity, and a plurality of the steel sheet piles are connected end to end to form a protective curtain; A liquid nitrogen distribution pipe, the liquid nitrogen distribution pipe extending along the axial direction of the tubular cavity to the bottom of the steel sheet pile, a side wall of the liquid nitrogen distribution pipe is provided with evenly distributed liquid nitrogen distribution holes, and a sealing structure corresponding to the bottom of the underground water-rich layer is provided inside the liquid nitrogen distribution pipe; The liquid nitrogen distribution pipe is correspondingly connected to a liquid nitrogen storage tank so as to guide the liquid nitrogen to the U-shaped flange through the liquid nitrogen distribution hole, and conduct it through the steel sheet piles to form a closed liquid nitrogen water-stopping curtain on both sides thereof.

2. The liquid nitrogen freezing temperature control pile water-stopping steel sheet pile system according to claim 1 is characterized in that: The plurality of liquid nitrogen distribution pipes are connected to a liquid nitrogen main pipe through solenoid valves respectively, and the liquid nitrogen main pipe is connected to the liquid nitrogen storage tank through a liquid nitrogen compression pump.

3. The liquid nitrogen freezing temperature control pile water-stopping steel sheet pile system according to claim 2 is characterized in that: Linear temperature sensors are respectively provided on both sides of the steel sheet pile, and the length of the linear temperature sensor is adapted to the length of the steel sheet pile; A displacement meter corresponding to the steel sheet pile is provided to monitor the horizontal displacement of the steel sheet pile.

4. The liquid nitrogen freezing temperature control pile water-stopping steel sheet pile system according to claim 3 is characterized in that: The linear temperature sensor and the array displacement meter are connected to signal transmitters respectively, the signal transmitters are communicatively connected to a controller, and the controller is connected to the solenoid valve and the liquid nitrogen compression pump respectively.

5. The liquid nitrogen freezing temperature control pile water-stop steel sheet pile system according to claim 1, characterized in that: The sealing structure is a hot melt adhesive, and its axial length is not less than 5 cm.

6. The liquid nitrogen freezing temperature control pile water-stopping steel sheet pile system according to claim 1 is characterized in that: The steel sheet piles include multiple sections spliced ​​in the longitudinal direction, and two adjacent sections of the steel sheet piles are fixed by bolts.

7. A method for using a liquid nitrogen freezing temperature-controlled pile water-stop steel sheet pile system, wherein freezing and water-stopping are performed by using the liquid nitrogen freezing temperature-controlled pile water-stop steel sheet pile system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1, hoisting the steel sheet pile to the construction area, and strengthening the U-shaped flange during the hoisting process; Step S2, determine the position and depth of the steel sheet piles around the foundation pit according to the construction drawing, the pile positioning axis should be offset 5 to 10 cm to the land side, the pile positioning axis should be 20 cm away from the construction area, and a rectangular area is formed by multiple steel sheet piles; Step S3, by distributing the double-sided guide frames in parallel on both sides of the steel sheet pile positioning axis, driving a guide pile every 2 to 4 meters, and attaching a guide beam between the guide pile and the steel sheet pile; Step S4, determining the underground water-rich layer according to geological data, setting the range of liquid nitrogen freezing, and setting a sealing structure below the underground water-rich layer in the liquid nitrogen distribution pipe; Step S5, check the parameters of the liquid nitrogen storage tank. When excavating above the water-rich soil layer, supply liquid nitrogen into the liquid nitrogen distribution pipe through the liquid nitrogen compression pump, and reduce and maintain the liquid nitrogen delivery power after forming a liquid nitrogen water-stop curtain; Step S6, continue to excavate the foundation pit, and monitor the temperature of the liquid nitrogen water-stop curtain and the horizontal displacement of the steel sheet piles at the same time. When the construction reaches the floor layer, stop the liquid nitrogen delivery, melt the frozen soil through self-heating of the soil, and pull out the steel sheet piles.

8. The method for using the liquid nitrogen freezing temperature-controlled pile water-stopping steel sheet pile system according to claim 7, characterized in that: After the pile positioning axis is determined, the starting point and end point of the pile are set on site, the observation point of the positioning axis is set on its extension line, and an array displacement meter is set at the observation point to monitor the horizontal displacement of the steel sheet pile; When the horizontal displacement of the steel sheet pile is greater than 2% of the pile length, liquid nitrogen is transported to the liquid nitrogen distribution pipe at maximum power.

9. The method for using the liquid nitrogen freezing temperature-controlled pile water-stopping steel sheet pile system according to claim 7, characterized in that: The sealing structure is hot melt adhesive, and its axial length is not less than 5 cm. A hot melt gun is used to inject the hot melt adhesive through the liquid nitrogen distribution holes on the side wall of the liquid nitrogen distribution pipe to form a seal inside the liquid nitrogen distribution pipe.

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