An inverted T-shaped dewatering well and construction method

Abstract

The application discloses an inverted T-shaped dewatering well, which comprises a horizontal pipe and a vertical pipe, the horizontal pipe comprises a horizontal outer sleeve pipe and a horizontal inner pipe, the horizontal inner pipe is coaxially sleeved in the horizontal outer sleeve pipe, the vertical pipe passes through the horizontal outer sleeve pipe and is communicated with the horizontal inner pipe, the two ends of the horizontal outer sleeve pipe and the horizontal inner pipe are respectively sealed by sealing plates, and water-permeable holes are formed in the sealing plates. A construction method for reducing the thickness of cofferdam sealing bottom by using the inverted T-shaped dewatering well is also provided. The construction method for reducing the thickness of cofferdam sealing bottom by using the inverted T-shaped dewatering well can effectively reduce the thickness of sealing bottom concrete and the amount of dredging in the cofferdam, and reduces the construction difficulty, saves the construction period and construction cost, compared with the traditional construction method for deep water area lock steel pipe pile cofferdam sealing bottom concrete.

Description

Technical Field

[0001] This invention relates to the field of cofferdam construction. More specifically, this invention relates to an inverted T-shaped dewatering well and its construction method. Background Technology

[0002] Due to its relatively simple construction process, low cost, and wide applicability, interlocking steel pipe pile cofferdams are increasingly used in deep-water foundation construction. When the water depth at the bottom of the structure constructed by the interlocking steel pipe pile cofferdam exceeds 20 meters, and the bottom is located in a highly permeable stratum, it is necessary to pour underwater concrete with a thickness of more than 4 meters to seal the bottom of the cofferdam to resist the enormous water and soil pressure on the bottom of the sealing concrete.

[0003] Due to the difficulty and high cost of constructing dewatering wells in deep water, the current practice in China for deep-water interlocked steel pipe pile cofferdams located in highly permeable strata is to pour a very thick layer of underwater sealing concrete after underwater excavation at the bottom of the cofferdam to forcibly resist the water pressure at the bottom of the cofferdam. Increasing the thickness of the sealing concrete leads to an increase in the thickness of the dredged mud inside the cofferdam, which not only increases the construction difficulty but also the construction cost. Summary of the Invention

[0004] To achieve these objectives and other advantages according to the present invention, the present invention provides an inverted T-shaped dewatering well, comprising a horizontal pipe and a vertical pipe. The horizontal pipe includes a horizontal outer pipe and a horizontal inner pipe, both of which have permeable holes on their surfaces. The horizontal inner pipe is coaxially sleeved inside the horizontal outer pipe, and the horizontal inner pipe and the horizontal outer pipe are separated by a predetermined distance. The vertical pipe is perpendicular to the horizontal outer pipe and passes through the horizontal outer pipe to connect to the horizontal inner pipe, communicating with the interior of the horizontal inner pipe. The two ends of the horizontal outer pipe and the horizontal inner pipe are respectively sealed with sealing plates, and the sealing plates have permeable holes.

[0005] Preferably, the outer surface of the horizontal inner tube is provided with a positioning rib at intervals, each positioning rib including four positioning ribs, all welded to the surface of the horizontal inner tube, and the four positioning ribs are distributed in a cross shape.

[0006] Preferably, the vertical pipe is continuously and fully welded to the horizontal inner pipe and the horizontal outer pipe.

[0007] Preferably, the space between the horizontal outer tube and the horizontal inner tube is filled with filter material; the diameter of the water-permeable holes on the sealing plate is 3mm.

[0008] On the other hand, the present invention also provides a construction method for reducing the thickness of the cofferdam bottom sealing using the inverted T-shaped dewatering well, comprising the following steps:

[0009] S1. The construction of the interlocking steel pipe piles forms a cofferdam, and the mud inside the cofferdam is dredged down to the bottom of the crushed stone filter pad layer.

[0010] S2, laying a layer of geotextile on the surface of the foundation;

[0011] S3, laying a gravel inverse filter cushion layer on the geotextile surface of the foundation;

[0012] S4, burying a circle of inverted T-shaped dewatering wells along the inner side of the cofferdam, and the horizontal pipe in the inverted T-shaped dewatering well is buried in the gravel inverse filter cushion layer, and the vertical pipe in the inverted T-shaped dewatering well is vertically upward;

[0013] S5, continuing to pour a bottom sealing concrete layer on the gravel inverse filter cushion layer;

[0014] S6, monitoring the water level in the cofferdam in real time, after the water level in the cofferdam is lower than the water level outside the cofferdam by a preset distance, cutting off the vertical pipe of the inverted T-shaped dewatering well along the water line, to ensure that the water in the dewatering well can flow naturally from the pressure relief well into the cofferdam;

[0015] S7, constructing a main structure on the bottom sealing concrete, and ensuring that the main structure and the inner wall of the cofferdam are separated by a preset distance, and the inverted T-shaped dewatering well is buried between the main structure and the inner wall of the cofferdam;

[0016] S8, after the main structure is completed, cutting off the vertical pipe of the inverted T-shaped dewatering well along the top surface of the bottom sealing concrete, and backfilling water into the cofferdam, and filling sand into the inverted T-shaped dewatering well after water balance.

[0017] Preferably, in S1, after the dredging is completed, the pile around the area where the bottom sealing concrete is poured and the steel pipe pile around the cofferdam is cleaned with a high-pressure water gun to prevent leakage due to mud in these areas.

[0018] Preferably, S5 further comprises the following operations:

[0019] After the bottom sealing concrete solidifies to the design strength, the water level in the inverted T-shaped dewatering well is monitored in real time, and when the water level exceeds a preset value, a pressure relief water pump pre-installed in the inverted T-shaped dewatering well is started to dewater, to ensure that the water level in the inverted T-shaped dewatering well is always at least 1 meter lower than the water level in the cofferdam.

[0020] Preferably, in S3, the thickness of the gravel inverse filter cushion layer is 30 cm, the gravel has a particle size of 5-50 mm, and the mud content of the gravel is less than 5%; when laying, the material is evenly spread by a bucket, the diver levels underwater, and a measuring rope is used to measure the cushion elevation every 1 meter, to ensure that the surface height difference of the cushion does not exceed 15 cm.

[0021] Preferably, an inner support is further horizontally arranged in the cofferdam, the two ends of the inner support respectively abut against the inner wall of the cofferdam, and the upper end of the vertical pipe in the inverted T-shaped dewatering well is connected to the inner support.

[0022] The present application at least comprises the following beneficial effects: the present application adopts the construction method of the pre-embedded inverted T-shaped dewatering well to reduce the thickness of the lock buckle steel pipe pile cofferdam bottom sealing concrete in the deep water area, compared with the traditional construction method of the lock buckle steel pipe pile cofferdam bottom sealing concrete in the deep water area, the thickness of the bottom sealing concrete can be effectively reduced, the amount of dredging in the cofferdam can be reduced, the construction difficulty is reduced, and the construction period and construction cost are saved.

[0023] Other advantages, objects, and features of the present application will be understood by those skilled in the art from the following description, and will be further understood by those skilled in the art upon examination of the detailed description and preferred embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0024] Fig. 1 The effect display structure diagram of the construction method for reducing the thickness of the cofferdam bottom in the present application.

[0025] Fig. 2 The structure diagram of the inverted T-shaped dewatering well. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement the present application according to the description.

[0027] The following description is used to disclose the present application so that those skilled in the art can implement the present application. The preferred embodiments in the following description are only as examples, and other obvious modifications can be thought of by those skilled in the art. The basic principles of the present application defined in the following description can be applied to other embodiments, modifications, improvements, equivalents and other technical solutions without departing from the spirit and scope of the present application.

[0028] Those skilled in the art should understand that in the disclosure of the present application, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the present application.

[0029] It can be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple, and the term "one" cannot be understood as a limitation on the number.

[0030] As Figs. 1-2As shown, a preferred embodiment of the present application provides a reverse T-shaped dewatering well 1, which comprises a horizontal pipe and a vertical pipe 1-3, the horizontal pipe comprises a horizontal outer sleeve pipe 1-1 and a horizontal inner pipe 1-2, both of which are provided with water-permeable holes on the surface, the horizontal inner pipe 1-2 is coaxially sleeved in the horizontal outer sleeve pipe 1-1, and the horizontal inner pipe 1-2 and the horizontal outer sleeve pipe 1-1 are separated by a predetermined distance (generally 15-25 cm in actual construction), the vertical pipe 1-3 is perpendicular to the horizontal outer sleeve pipe 1-1, and the vertical pipe 1-3 is connected to the horizontal inner pipe 1-2 by penetrating the horizontal outer sleeve pipe 1-1 and communicating with the inside of the horizontal inner pipe 1-2, both ends of the horizontal outer sleeve pipe 1-1 and the horizontal inner pipe 1-2 are blocked by sealing plates 1-4, and the sealing plates 1-4 are provided with water-permeable holes. The horizontal outer sleeve pipe 1-1 and the vertical pipe on both sides are welded into an eight-shaped reinforcement by using dewatering steel pipes 1-5, so as to ensure firm connection. Filter material is filled between the horizontal outer sleeve pipe 1-1 and the horizontal inner pipe 1-2.

[0031] In the above technical solution, in actual construction, the reverse T-shaped dewatering well is welded by the horizontal pipe and the vertical pipe 1-3; a single horizontal pipe comprises a horizontal outer sleeve pipe 1-1 and a horizontal inner pipe 1-2, the horizontal outer sleeve pipe 1-1 has a larger diameter, the horizontal inner pipe 1-2 has a smaller diameter, and the horizontal inner pipe 1-2 is arranged centrally in the horizontal outer sleeve pipe; the horizontal inner pipe 1-2 is a dewatering well flower pipe with a diameter of 27.3 cm, and the horizontal outer sleeve pipe 1-1 uses a dewatering well flower pipe with a diameter of 50 cm; a positioning steel bar is arranged every 1 meter outside the horizontal inner pipe 1-2, the vertical pipe is a dewatering well steel pipe with a diameter of 27.3 cm, the vertical pipe penetrates the horizontal outer sleeve pipe 1-1 and enters the inside of the horizontal inner pipe 1-2, and the length of the vertical pipe extending into the horizontal inner pipe 1-2 is 1 / 3-1 / 2 of the diameter of the horizontal inner pipe, so as to facilitate the flow of water from the horizontal inner pipe into the vertical pipe, the vertical pipe, the horizontal outer sleeve pipe 1-1 and the horizontal inner pipe 1-2 all adopt continuous full welding, the horizontal outer sleeve pipe 1-1 and the vertical pipe 1-3 on both sides are welded into an eight-shaped reinforcement by using dewatering steel pipes 1-5 with a diameter of 27.3 cm, so as to ensure firm connection, one end of the dewatering steel pipe 1-5 penetrates the horizontal outer sleeve pipe 1-1 and is welded to the horizontal inner pipe 1-2, and the dewatering steel pipe 1-5 is also welded and connected with the horizontal outer sleeve pipe 1-1, the bottom of the reverse T-shaped dewatering well is designed into a tee shape, which can effectively prevent slag or sludge from blocking a certain pipe and causing dewatering failure.

[0032] The groundwater can enter the filter material between the horizontal outer sleeve pipe 1-1 and the horizontal inner pipe 1-2 through the water-permeable holes on the surface of the horizontal outer sleeve pipe 1-1, is filtered through the filter material, flows into the horizontal inner pipe 1-2 through the water-permeable holes on the surface of the horizontal inner pipe 1-2, and finally flows into the vertical pipe to be discharged, so that the purpose of precipitation is achieved. The filter material is gravel or rubble with a diameter of 2-5 mm, which is cleaned with clean water to ensure that the mud content is less than 1%. The filter material is like a fine filter screen, which can effectively block the impurities such as silt and particles in the groundwater, and allow the clear groundwater to enter the interior of the precipitation well.

[0033] In another technical solution, a positioning rib is arranged on the outer surface of the horizontal inner pipe 1-2, and each positioning rib includes four positioning ribs, which are welded on the surface of the horizontal inner pipe 1-2, and the four positioning ribs are arranged in a cross shape.

[0034] The positioning rib is arranged in the above technical solution, each positioning rib is composed of four steel bars with a diameter of 2 cm, which are arranged in a cross shape and welded on the horizontal inner pipe 1-2, and the length of the steel bar is 9 cm, so that the horizontal inner pipe 1-2 can be smoothly put into the horizontal outer sleeve pipe 1-1 and be basically centered; the position of the horizontal inner pipe 1-2 in the horizontal outer sleeve pipe 1-1 is accurately fixed, so that the deviation, shaking or even collision damage of the horizontal inner pipe 1-2 caused by water flow impact, external force vibration and other factors during construction process or long-term use is avoided. The stability of the position of the horizontal inner pipe 1-2 ensures that the water passage of the inverted T-shaped precipitation well 1 always remains unobstructed and regular, and the normal work of the precipitation well is ensured.

[0035] In another technical solution, continuous full welding is adopted between the vertical pipe and the horizontal inner pipe 1-2 and the horizontal outer sleeve pipe 1-1. The overall structural strength of the inverted T-shaped precipitation well 1 is greatly enhanced, so that the stability of the structure can be maintained when the inverted T-shaped precipitation well 1 is subjected to external forces such as groundwater pressure and soil extrusion in a complex engineering environment.

[0036] In another technical solution, filter material is filled between the horizontal outer sleeve pipe 1-1 and the horizontal inner pipe 1-2; and the water-permeable holes with a diameter of 3 mm are arranged on the sealing plate 1-4.

[0037] In the above technical solution, the water-permeable holes with a diameter of 3 mm can not only ensure sufficient water flow to meet the demand of precipitation, but also prevent larger particles from entering the precipitation well, thereby playing a certain filtering and flow limiting role.

[0038] On the other hand, a preferred embodiment of the present application provides a construction method for reducing the thickness of the cofferdam bottom sealing, which comprises the following steps:

[0039] S1, after the completion of the construction of the bridge bored pile, the lock buckle steel pipe pile is inserted and driven to form a cofferdam 2, and the cofferdam 2 is dredged to the gravel inverted filter cushion 4 preset bottom;

[0040] S2, a layer of geotextile 3 is laid on the surface of the base;

[0041] The geotextile 3 is laid between the surface of the base and the subsequent gravel inverted filter cushion 4, which can effectively isolate the fine particles remaining in the base from the gravel. If the fine particles in the base enter the gravel inverted filter cushion 4, it will block the pores between the gravel, reducing the drainage performance of the cushion; while the geotextile 3 can block these fine particles, while not affecting the normal permeation of groundwater, ensuring that the drainage function of the gravel inverted filter cushion 4 is not disturbed.

[0042] S3, the gravel inverted filter cushion 4 is laid on the surface of the geotextile 3 of the base;

[0043] The gravel inverted filter cushion 4 is composed of granular gravel, forming a large number of interconnected pores between the gravel, which can quickly collect groundwater from the base and the surrounding area, and drain the water to the inverted T-shaped dewatering well 1 through the pores. Without this cushion, groundwater is easy to accumulate at the bottom of the bottom sealing concrete layer 5, generating a large seepage pressure, which may cause concrete cracking and leakage; while the drainage effect of the cushion can effectively release the groundwater pressure, ensuring the integrity of the bottom sealing concrete layer 5.

[0044] S4, the inverted T-shaped dewatering well 1 is buried along the inside of the cofferdam 2, and the horizontal pipe in the inverted T-shaped dewatering well 1 is buried in the gravel inverted filter cushion 4, and the vertical pipe 1-3 in the inverted T-shaped dewatering well 1 is vertically upward;

[0045] The horizontal pipe of the inverted T-shaped dewatering well 1 is buried in the gravel inverted filter cushion 4, and the groundwater collected by the cushion can directly enter the horizontal pipe and then be discharged through the vertical pipe. Compared with the traditional vertical dewatering well, the horizontal pipe has a larger contact area with the cushion, which can collect groundwater more quickly and comprehensively, improving the efficiency of dewatering. At the same time, the dewatering well is buried along the inside of the cofferdam 2, forming a ring-shaped dewatering system, which can uniformly reduce the groundwater level inside the cofferdam, avoiding the influence of local high water level on construction. The dewatering well 1 is buried in the gap between the inside of the cofferdam 2 and the subsequent main structure 6, without occupying the construction area of the main structure 6. If the dewatering well is set in the construction range of the main structure, it needs to be moved or removed later, increasing the construction process and cost; while the buried position not only ensures the dewatering function, but also reserves sufficient space for the construction of the main structure 6, simplifying the construction process and improving the construction efficiency.

[0046] S5, continue to pour the bottom sealing concrete layer 5 on the gravel inverted filter cushion 4;

[0047] The bottom sealing concrete layer 5 is directly poured on the gravel inverted filter cushion 4, and the concrete can be closely combined with the cushion to form a continuous closed structure, effectively blocking the upward penetration of groundwater from the base.

[0048] S6, monitoring the water level in the cofferdam 2 in real time, after the water level in the cofferdam 2 is lower than the water level outside the cofferdam 2 by a preset distance (usually 1-2 meters in actual construction), cutting off the vertical pipe 1-3 of the inverted T-shaped dewatering well 1 along the water line to ensure that the water in the dewatering well can flow naturally from the pressure relief well into the cofferdam 2;

[0049] When the water level in the cofferdam 2 is lower than the outside by a preset distance, the water level in the inverted T-shaped dewatering well 1 will be higher than the water level in the cofferdam, forming a natural water level difference. At this time, the vertical pipe 1-3 is cut off, and the water in the dewatering well can flow naturally into the cofferdam 2 depending on the water level difference, without the need to start additional drainage equipment (such as a water pump), reducing power consumption and construction energy costs, while avoiding the risk of drainage interruption due to equipment failure. After cutting off the vertical pipe, the water in the dewatering well flows naturally into the cofferdam, keeping the water level in the dewatering well and the cofferdam in dynamic balance, avoiding excessive external water pressure on the bottom sealing concrete layer 5 or reverse seepage due to too high water level. This dynamic balance can effectively protect the structural integrity of the bottom sealing concrete layer 5 and reduce structural damage caused by rapid changes in water level.

[0050] S7, constructing the main structure 6 on the bottom sealing concrete, and ensuring that the main structure 6 and the inner wall of the cofferdam 2 are separated by a preset distance (usually 0.5-1.5 meters in actual construction), and the inverted T-shaped dewatering well 1 is buried between the main structure 6 and the inner wall of the cofferdam 2;

[0051] S8, after the main structure 6 is completed, cutting off the vertical pipe 1-3 of the inverted T-shaped dewatering well 1 along the top surface of the bottom sealing concrete, and backfilling water into the cofferdam 2, and filling sand into the inverted T-shaped dewatering well 1 after water balance.

[0052] After the main structure 6 is completed, backfilling water into the cofferdam 2 can keep the water level inside and outside the cofferdam balanced, avoiding long-term low water level in the cofferdam causing surrounding soil settlement, and the water level outside the cofferdam being higher than the inside, which can cause water pressure difference and possibly cause the surrounding soil to move towards the cofferdam, affecting the safety of surrounding buildings or underground pipelines; water level balance can eliminate this water pressure difference and protect the stability of the surrounding environment. Filling sand into the dewatering well 1 can completely seal the well body and prevent groundwater from seeping into the main structure through the well body during subsequent use. Compared with other sealing methods (such as pouring concrete), sand has good compactness, and the filling operation is simple and low in cost, and at the same time, sand can form good combination with the surrounding soil, ensuring the permanence of the sealing effect, providing protection for the long-term stable use of the main structure 6.

[0053] The application successfully utilizes the inverted T-shaped dewatering well 1 to effectively reduce the groundwater level in the cofferdam 2, so that the bottom sealing concrete is constructed in a water-free or low-water environment, thereby reducing the thickness of the cofferdam bottom sealing. Compared with the traditional construction method, the amount of bottom sealing concrete is reduced, and the engineering cost is reduced.

[0054] In another technical solution, in the S1, after the dredging is completed, the pile around the area where the bottom sealing concrete is poured and the steel pipe pile around the cofferdam 2 are cleaned with a high-pressure water gun to prevent seepage in these areas due to mud.

[0055] In the above technical solution, the pile around the area where the bottom sealing concrete is poured and the steel pipe pile around the cofferdam 2 are cleaned with a high-pressure water gun, effectively removing the mud in these areas. This makes the combination between the pile and the steel pipe pile and the subsequent poured bottom sealing concrete more tightly, avoiding the problem of loose combination due to the presence of mud, thereby preventing seepage in these parts during the use of the cofferdam. The quality of the cofferdam bottom sealing is ensured, providing a stable and reliable construction environment for a series of subsequent constructions in the cofferdam, such as laying the gravel inverted filter cushion 4, pouring the bottom sealing concrete layer 5, and constructing the main structure 6, reducing the engineering risks caused by seepage, and ensuring the smooth progress and construction safety of the entire project.

[0056] In another technical solution, the S5 further includes the following operations:

[0057] After the bottom sealing concrete solidifies to the design strength, the water level in the inverted T-shaped dewatering well 1 is monitored in real time, and when the water level exceeds the preset value, the pre-installed pressure-reducing water pump in the inverted T-shaped dewatering well 1 is started to dewater, ensuring that the water level in the inverted T-shaped dewatering well 1 is always at least 1 meter lower than the water level in the cofferdam 2.

[0058] In the above technical solution, by monitoring the water level in the inverted T-shaped dewatering well 1 in real time and starting the pressure-reducing water pump in time to dewater when the water level exceeds the preset value, the water level in the inverted T-shaped dewatering well 1 can be effectively controlled to be at least 1 meter lower than the water level in the cofferdam 2. This operation avoids excessive pressure on the bottom sealing concrete due to high groundwater level, prevents cracks, seepage, and other problems in the bottom sealing concrete, and ensures the quality and stability of the bottom sealing concrete.

[0059] In another technical solution, in the S3, the gravel inverted filter cushion 4 has a thickness of 30 cm and uses gravel with a particle size of 5-50 mm, and the mud content of the gravel is less than 5%; during laying, the material is evenly spread by a bucket, and divers level the cushion underwater while measuring the cushion elevation every 1 meter with a measuring rope to ensure that the surface elevation difference of the cushion does not exceed 15 cm.

[0060] Another technical solution, the cofferdam is also horizontally provided with an inner support 7, the two ends of the inner support 7 are respectively abutted against the inner wall of the cofferdam, and the upper end of the vertical pipe in the inverted T-shaped dewatering well is connected to the inner support.

[0061] In the above technical solution, the inner support supports the inner wall of the cofferdam 2 at both ends, greatly enhances the overall stability of the cofferdam 2, effectively resists the action of external forces such as water pressure and soil pressure, and prevents safety accidents such as deformation, displacement and even collapse of the cofferdam 2. At the same time, the inner support plays a supporting and fixing role on the vertical pipe 1-3 of the inverted T-shaped dewatering well 1, avoids the inclination, shaking or damage of the vertical pipe 1-3 due to the impact force of water, extrusion of soil and other external forces during the dewatering process, and ensures that the dewatering well can continuously and stably dewater.

[0062] The construction method has been successfully implemented in the bridge deep water lock buckle steel pipe pile cofferdam of Nantong Tiancheng Port Coal Terminal of China Communications Second Harbor Engineering Co., Ltd.

[0063] The Nantong Tiancheng Port Coal Terminal Bridge of China Communications Second Harbor Engineering Co., Ltd. is located on the Yangtze River about 2 kilometers downstream of the Shanghai-Tongzhou Yangtze River Bridge, and the five main piers are located in the deep water area of the Yangtze River, with the bottom of the pile cap being about 15-18 meters deep. The design adopts a lock buckle steel pipe pile cofferdam construction, and the thickness of the bottom sealing concrete is originally designed according to the traditional construction process, with a thickness of 3.5-4 meters. This results in a very large amount of bottom sealing concrete and dredging, and modeling calculations show that excessive dredging depth will cause excessive deformation of the cofferdam and other adverse effects. After a long period of research, testing and innovative optimization by the technical team of the Second Harbor Engineering Bureau, the bottom of the bottom sealing concrete is buried with an inverted filter cushion and a specially designed and manufactured inverted T-shaped dewatering well for pressure relief, and the thickness of the bottom sealing concrete is uniformly optimized to 1 meter, which is a success. That is, the construction method of the inverted T-shaped dewatering well for reducing the thickness of the bottom sealing concrete of the lock buckle steel pipe pile cofferdam in the deep water area of the application file significantly reduces the thickness of the bottom sealing of the lock buckle steel pipe pile cofferdam, and the dredging depth and amount are also significantly reduced, saving the construction period and cost, and reducing the construction difficulty.

[0064] Although the embodiments of the present application have been disclosed as above, they are not limited to the application listed in the specification and the embodiments, and can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, and therefore the present application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A construction method for reducing the thickness of the cofferdam bottom sealing layer using inverted T-shaped dewatering wells, characterized in that, Includes the following steps: S1. The construction of the interlocking steel pipe piles forms a cofferdam, and the mud inside the cofferdam is dredged down to the bottom of the crushed stone filter pad layer. S2. Lay a layer of geotextile on the base surface; S3. Lay a gravel filter pad layer on the surface of the geotextile of the base; S4. Inverted T-shaped dewatering wells are buried around the inner side of the cofferdam, with the horizontal pipes in the inverted T-shaped dewatering wells buried in the crushed stone filter pad layer, and the vertical pipes in the inverted T-shaped dewatering wells pointing vertically upwards. S5. Continue pouring the bottom sealing concrete layer into the crushed stone filter pad layer; S6. Monitor the water level inside the cofferdam in real time. After the water level inside the cofferdam drops to a preset distance lower than the water level outside the cofferdam, cut the vertical pipe of the inverted T-shaped dewatering well along the water surface line to ensure that the water in the dewatering well can flow naturally into the cofferdam from the depressurization well. S7. Construct the main structure on the bottom sealing concrete, and ensure that the main structure and the inner wall of the cofferdam are separated by a preset distance. The inverted T-shaped dewatering well is buried between the main structure and the inner wall of the cofferdam. S8. After the main structure is completed, cut off the vertical pipe of the inverted T-shaped dewatering well along the top surface of the bottom sealing concrete, and refill water into the cofferdam. After the water is balanced, fill sand into the inverted T-shaped dewatering well. An inverted T-shaped dewatering well includes a horizontal pipe and a vertical pipe. The horizontal pipe includes a horizontal outer pipe and a horizontal inner pipe, both of which have permeable holes on their surfaces. The horizontal inner pipe is coaxially fitted inside the horizontal outer pipe, and the horizontal inner pipe and the horizontal outer pipe are separated by a predetermined distance. Filter media is filled between the horizontal outer pipe and the horizontal inner pipe. The vertical pipe is perpendicular to the horizontal outer pipe and passes through the horizontal outer pipe to connect to the horizontal inner pipe, communicating with the interior of the horizontal inner pipe. Both ends of the horizontal outer pipe and the horizontal inner pipe are sealed with sealing plates, and permeable holes are opened on the sealing plates.

2. The construction method for reducing the thickness of the cofferdam bottom sealing layer according to claim 1, characterized in that, In step S1, after the dredging is completed, the area around the pile foundation and the area around the steel pipe piles inside the cofferdam where the bottom sealing concrete is poured are cleaned with a high-pressure water gun to prevent leakage caused by mud inclusion in these areas.

3. The construction method for reducing the thickness of the cofferdam bottom sealing layer according to claim 1, characterized in that, S5 also includes the following operations: After the bottom sealing concrete has solidified to the design strength, the water level in the inverted T-shaped dewatering well is monitored in real time. When the water level exceeds the preset value, the pressure-reducing water pump pre-installed in the inverted T-shaped dewatering well is started to reduce the water level, ensuring that the water level in the inverted T-shaped dewatering well is always at least 1 meter lower than the water level inside the cofferdam.

4. The construction method for reducing the thickness of the cofferdam bottom sealing layer according to claim 1, characterized in that, In S3, the thickness of the crushed stone filter pad is 30cm, and crushed stone with a particle size of 5-50mm is used. The mud content of the crushed stone is less than 5%. During the laying, the material is evenly spread by a bucket, and the diver levels it underwater. At the same time, the elevation of the pad is measured every 1 meter with a measuring rope to ensure that the surface elevation difference of the pad does not exceed 15cm.

5. The construction method for reducing the thickness of the cofferdam bottom sealing layer according to claim 1, characterized in that, The cofferdam is also equipped with horizontal internal supports, with both ends of the internal supports abutting against the inner wall of the cofferdam, and the upper end of the vertical pipe in the inverted T-shaped dewatering well is connected to the internal supports.

6. The construction method for reducing the thickness of the cofferdam bottom sealing layer according to claim 1, characterized in that, The outer surface of the horizontal inner tube is provided with a positioning rib at intervals. Each positioning rib includes four positioning ribs, which are all welded to the surface of the horizontal inner tube and are distributed in a cross shape.

7. The construction method for reducing the thickness of the cofferdam bottom sealing layer according to claim 1, characterized in that, The vertical pipe is continuously and fully welded to the horizontal inner pipe and the horizontal outer pipe.

8. The construction method for reducing the thickness of the cofferdam bottom sealing layer according to claim 1, characterized in that, The diameter of the water-permeable holes opened on the sealing plate is 3mm.

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