CN114775664B - A steel sheet pile cofferdam construction method for deep foundation pit and steel sheet pile cofferdam - Google Patents

Abstract

The application relates to a steel sheet pile cofferdam construction method for a deep foundation pit and a steel sheet pile cofferdam, and relates to the technical field of cofferdam construction. The steel sheet pile cofferdam construction method comprises the steps of firstly obtaining geological information of a construction site, determining a construction area, setting a guide structure in the construction area, then sequentially inserting and driving steel sheet piles under the guide of the guide structure, selecting water cutters or air cutters to alternately guide holes according to the obtained geological information in the inserting and driving process so as to assist the steel sheet piles to be inserted and driven to a preset depth, excavating a foundation pit after closure of the steel sheet piles is completed, setting a plurality of inner supporting structures from top to bottom in the excavating process, and finally injecting back cover concrete towards the bottom of the foundation pit along the outer side wall of the steel sheet piles to finish back cover of the foundation pit. The construction method of the steel sheet pile cofferdam provided by the application realizes that the steel sheet pile can be inserted and driven to a deeper depth under the combined assistance of the water knife and the air knife, has good water-proof effect, and reduces the difficulty of construction hoisting.

Description

A steel sheet pile cofferdam construction method for deep foundation pit and steel sheet pile cofferdam

Technical Field

The present application relates to the technical field of cofferdam construction, and in particular to a steel sheet pile cofferdam construction method and a steel sheet pile cofferdam for a deep foundation pit.

Background Art

A cofferdam refers to a temporary water retaining structure built around a foundation pit for the purpose of constructing permanent facilities during the construction of bridges, ports and water conservancy projects. Its main function is to prevent water and soil from entering the construction site of the building so that drainage and soil discharge construction can be carried out within the cofferdam, allowing foundation pit excavation and building construction to be carried out under dry conditions.

There are many types of cofferdams. Commonly used cofferdams include earth and rock cofferdams, wooden cofferdams, steel sheet pile cofferdams, steel pipe pile cofferdams, and combined cofferdams of steel sheet piles and steel pipe piles. In large-scale construction, commonly used cofferdams are steel sheet pile cofferdams, steel pipe pile cofferdams, and combined cofferdams of steel sheet piles and steel pipe piles. The corresponding cofferdams are selected according to the scale of construction and the geological environment of construction. Generally, steel sheet piles have many advantages such as high strength, light weight, good water-proofing, long service life, high safety, low space requirements, and significant environmental protection effects. In addition, the construction is simple, the construction period is short, it can be reused, and the construction cost is low. Its construction process is much simpler than that of steel pipe piles and combined cofferdams. Therefore, the use of steel sheet piles is quite extensive. However, steel sheet piles are limited by the insertion depth. At present, the deepest insertion depth of steel sheet piles does not exceed 10 meters, otherwise deformation problems will occur, which will affect the isolation effect of the cofferdam.

Therefore, in the related technology, steel pipe pile cofferdams are often used for cofferdams with larger scale and deeper depth, because the steel pipe pile cofferdams have a greater insertion depth than steel sheet piles, are not easily deformed, and can be applied to hard soil layers. However, the overall construction of steel pipe pile cofferdams is very difficult, the soil squeezing effect is large during the insertion process, the overall construction period is long, and the construction cost is high.

Summary of the invention

The embodiments of the present application provide a steel sheet pile cofferdam construction method and a steel sheet pile cofferdam for a deep foundation pit, so as to solve the problem in the related art that the steel sheet piles cannot adapt to the cofferdam construction of a deep foundation pit and are easily deformed during the insertion process, thereby affecting the cofferdam performance.

In a first aspect, a steel sheet pile cofferdam construction method for a deep foundation pit is provided, the steps comprising:

Obtain geological information of the construction site and determine the construction area;

Providing a guide structure within the construction area;

The steel sheet piles are inserted and driven in sequence under the guidance of the guide structure, and during the insertion and driving process, a water jet or an air jet is selected to alternately guide holes according to the acquired geological information to assist the steel sheet piles to be inserted and driven to a preset depth;

The steel sheet piles are connected together, the foundation pit is excavated, and a plurality of internal support structures are arranged from top to bottom during the excavation process;

The bottom sealing concrete is injected along the outer side wall of the steel sheet pile toward the bottom of the foundation pit to complete the bottom sealing of the foundation pit.

In some embodiments, the step of setting a guide structure at a preset position in the construction area includes:

Determine the driving points of the steel sheet piles in sequence within the construction area;

Sequentially driving a plurality of steel pipe piles on the inner side and the outer side of a circle of driving points along the arrangement track of the driving points, and after driving is completed, respectively setting guide I-beams on the tops of the steel pipe piles located on the inner side and the outer side;

A plurality of spacing reinforcement bars are slidably arranged on the guide I-beams located at the inner and outer sides.

In some embodiments, the step of inserting the steel sheet piles in sequence under the guidance of the guide structure further includes:

Adjust one of the limiting steel bars to one side of the corresponding insertion point;

The steel sheet piles are driven in, and during the driving process, the guide I-beams located on the inner and outer sides are respectively used to assist in correcting the position of the steel sheet piles in the direction from the inner side to the outer side, and the limiting steel bars are also used to assist in correcting the position of the steel sheet piles in the left-right direction.

In some embodiments, during the driving process, water jet or air knife is selected to alternately guide holes according to the acquired geological information to assist the driving of the steel sheet pile to a preset depth, and the steps include:

Determine the geological information of the current drilling depth. If the geological information of the current drilling depth is hard plastic clay or gravel soil, use a water knife to guide the hole. If the geological information of the current drilling depth is muddy siltstone or strongly weathered rock, use an air knife to guide the hole.

During the driving process, water jet or air knife is selected to alternately drill holes according to the geological information until the steel sheet pile is driven to the preset depth.

In some embodiments, before inserting the steel sheet pile, the method further includes:

A vertically arranged hole-introducing pipe is arranged on the inner wall of the web of the steel sheet pile along its length direction, and at least two downwardly arranged hole-introducing nozzles are arranged at the bottom end of the hole-introducing pipe;

A vertically arranged grouting pipe is arranged on the outer wall of the web of the steel sheet pile along its length direction.

In some embodiments, before inserting the steel sheet pile, the method further includes:

Applying a waterproofing agent on the buckle of the steel sheet pile;

The waterproofing agent includes silicate cement, quartz sand, anti-seepage material fly ash, silicone hydrophobic powder, HPMC cellulose, polyurethane single-component single-component two-component type I, polyurethane single-component two-component type II, cement-based permeable crystallization, polymer cement waterproof coating JS, and the mass ratio of each component is 52:38:5:75:3:10:5:5:10. The quartz sand includes 100-mesh quartz sand and 200-mesh quartz sand, and the mass ratio of 100-mesh quartz sand to 200-mesh quartz sand is 15:4.

In some embodiments, the steps of setting up multiple internal support structures from top to bottom during the excavation process include:

Steel purlins are set along the inner wall of the steel sheet pile cofferdam;

An internal supporting structure is provided on the steel purlin;

Continue to dig downwards, and sequentially set the steel perimeter purlins and the inner support structure. The greater the digging depth, the smaller the distance between two adjacent steel perimeter purlins or inner support structures.

In a second aspect, a steel sheet pile cofferdam for a deep foundation pit is provided, comprising:

The cofferdam body comprises a plurality of steel sheet piles connected end to end, each of the steel sheet piles is provided with a hole-guiding assembly and a liquid injection assembly, the hole-guiding assembly is used to select a water knife or an air knife to alternately guide holes according to the geological information of the construction site to assist the steel sheet piles to be driven to a preset depth, and the liquid injection assembly is used to inject bottom sealing concrete along the outer side wall of the steel sheet pile toward the bottom of the foundation pit to complete the bottom sealing of the foundation pit;

A guide structure is arranged along the circumference of the cofferdam body, and the guide structure is used to guide the steel sheet piles when they are inserted.

In some embodiments, the guide structure includes a plurality of steel pipe piles, a portion of the steel pipe piles are arranged at intervals on the inner side of the steel pipe piles along the arrangement track of the steel sheet piles, and the remaining portion of the steel pipe piles are arranged at intervals on the outer side of the steel pipe piles along the arrangement track of the steel sheet piles, and a plurality of guide I-beams are provided on the tops of the steel pipe piles located on the inner and outer sides, and a plurality of spaced limiting steel bars are slidably provided on the guide I-beams located on the inner and outer sides;

The guide I-beam is used to limit the deviation of the steel sheet piles in the inner or outer direction when they are driven in, and the limit steel bar is used to limit the deviation of the steel sheet piles in the left or right direction when they are driven in.

In some embodiments, each buckle of the steel sheet pile is coated with a waterproofing agent, which includes silicate cement, quartz sand, anti-seepage material fly ash, silicone hydrophobic powder, HPMC cellulose, polyurethane one-component single-two-component type I, polyurethane one-component two-component type II, cement-based permeable crystallization, polymer cement waterproof coating JS, and the mass ratio of each component is 52:38:5:75:3:10:5:5:10, and the quartz sand includes 100 mesh quartz sand and 200 mesh quartz sand, and the mass ratio of 100 mesh quartz sand and 200 mesh quartz sand is 15:4.

The beneficial effects of the technical solution provided by this application include:

The embodiment of the present application provides a steel sheet pile cofferdam construction method for a deep foundation pit, in which a guide structure is first arranged in the construction area, and then the steel sheet piles are inserted and driven in sequence under the guidance of the guide structure according to the geological information of the construction site obtained, and in the process of inserting and driving, a water knife or an air knife is selected to alternately guide holes according to the geological information obtained to assist the steel sheet piles to be inserted and driven to a preset depth, and a plurality of internal support structures are arranged from top to bottom in the process of excavating the foundation pit, and finally, bottom sealing concrete is injected toward the bottom of the foundation pit along the outer wall of the steel sheet pile to complete the bottom sealing of the foundation pit. With the joint assistance of water jet and air knife, the weir construction method can achieve that the steel sheet piles can be driven deeper and will not be deformed during the driving process, so as to ensure the basic performance of the cofferdam; in addition, the amount of soil taken and the use of concrete are greatly reduced in the entire construction process, and the water-proof effect is good. Since the steel sheet piles are relatively light in weight, the difficulty of construction and hoisting is also reduced; finally, the steel sheet piles themselves are used as mother piles for drilling and grouting, avoiding the problem of loose soil layer caused by the subsequent withdrawal of the mother piles, which affects the driving of the steel sheet piles and the basic performance of the cofferdam.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

FIG1 is a flow chart of a steel sheet pile cofferdam construction method for a deep foundation pit provided in an embodiment of the present application;

FIG2 is a top view of a steel sheet pile cofferdam for a deep foundation pit provided in an embodiment of the present application.

In the figure: 1-cofferdam body, 2-steel sheet piles, 3-guide structure, 30-guide I-beam, 31-limiting steel bar.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

The embodiment of the present application provides a steel sheet pile cofferdam construction method for deep foundation pits, which can solve the problem in the related art that steel sheet piles cannot adapt to the cofferdam construction of deep foundation pits and are easily deformed during the insertion process, thereby affecting the cofferdam performance.

As shown in Figure 1, the steps of the steel sheet pile cofferdam construction method include: first, obtaining the geological information of the construction site and determining the construction area, then setting a guide structure 3 in the construction area, and inserting the steel sheet piles 2 in sequence under the guidance of the guide structure 3, and selecting a water knife or an air knife to alternately guide holes according to the acquired geological information during the insertion process to assist the steel sheet piles 2 to be inserted to a preset depth, and then completing the closure of the steel sheet piles 2, excavating the foundation pit, and setting a plurality of internal support structures from top to bottom during the excavation process, and finally injecting bottom sealing concrete along the outer wall of the steel sheet pile 2 toward the bottom of the foundation pit to complete the bottom sealing of the foundation pit.

The present steel sheet pile cofferdam construction method adopts the combined use of water jets and air knives. According to the specific geological conditions of the construction site, with the joint assistance of water jets and air knives, the steel sheet piles 2 can be driven to a deeper depth, thus overcoming the problem of deformation that may occur with increasing depth during the driving process, so that the steel sheet piles will not be deformed during the driving process, thereby ensuring the basic performance of the cofferdam. In addition, compared with other cofferdam forms, the present steel sheet pile cofferdam construction method greatly reduces the amount of soil taken and the use of concrete during the entire construction process, and the water-isolating effect is more prominent than that of steel pipe piles. Since the steel sheet piles 2 are relatively light in weight, the difficulty of construction hoisting is also reduced, thereby reducing the construction difficulty. Finally, the steel sheet piles 2 themselves are used as mother piles for guide holes and grouting, thereby avoiding the problem that the soil layer may become loose during the later extraction of the mother piles driven alone, thereby affecting the driving of the steel sheet piles 2 and the basic performance of the cofferdam.

Furthermore, a guide structure 3 is set at a preset position in the construction area, and the steps mainly include:

Determine the insertion points of the steel sheet piles 2 in sequence within the construction area;

A plurality of steel pipe piles are sequentially driven inwardly and outwardly of a circle of determined driving points along the arrangement track of the driving points, and after driving is completed, guide I-beams 30 are respectively arranged on the tops of the steel pipe piles located inwardly and outwardly;

A plurality of spacing reinforcement bars 31 are slidably mounted on the guide I-beams 30 located at the inner and outer sides.

Furthermore, the steel sheet piles 2 are inserted in sequence under the guidance of the guide structure 3, and the steps also include:

Adjust one of the limiting steel bars 31 to one side of the corresponding insertion point;

When inserting the steel sheet pile 2, the guide I-beams 30 located on the inside and outside are used to assist in correcting the position of the steel sheet pile 2 from the inside to the outside during the inserting process, and the limiting steel bar 31 is used to assist in correcting the position of the steel sheet pile 2 along the left and right direction.

Specifically, each driving point is determined in the construction area, and each driving point is marked and effectively protected after verification. Subsequently, a plurality of steel pipe piles are driven in sequence along the arrangement trajectory of the driving points on the inner and outer sides of a circle of determined driving points, and preliminary positioning is performed using the driven steel pipe piles. The directions of the steel pipe piles on the inner and outer sides correspond to the shape of the cofferdam, that is, they both form a square structure. A guide I-beam 30 is set on the steel pipe piles on each side of the inner and outer sides. After the guide I-beam 30 is set, A limit steel bar 31 that can slide along the length direction of the guide I-beam 30 is set on the side. When the steel sheet pile 2 starts to be driven, the side walls of the inner and outer guide I-beams 30 are used to assist in correcting the position of the steel sheet pile 2 from the inside to the outside, that is, as a reference to prevent the steel sheet pile 2 from deviating to the outside or inside during the driving process. Similarly, the limit steel bar 31 is used to assist in correcting the position of the steel sheet pile 2 along the left and right directions to prevent the steel sheet pile 2 from deviating to the left and right directions during the driving process. The guide I-beam 30 and the limit steel bar 31 serve as guide position and elevation control marks during pile driving, which can ensure that the driven steel sheet piles 2 on the same side are in a straight line.

Furthermore, in the process of driving and inserting, water jet or air knife is selected to alternately guide holes according to the acquired geological information to assist the steel sheet pile 2 in driving and inserting to a preset depth, and the steps include:

Determine the geological information of the current drilling depth. If the geological information of the current drilling depth is hard plastic clay or gravel soil, use a water knife to guide the hole. If the geological information of the current drilling depth is muddy siltstone or strongly weathered rock, use an air knife to guide the hole.

During the driving process, water jet or air knife is selected to alternately drill holes according to geological information until the steel sheet pile 2 is driven to a preset depth.

Furthermore, before inserting the steel sheet pile 2, the method further includes:

A vertically arranged hole-introducing pipe is arranged on the inner wall of the web of the steel sheet pile 2 along its length direction, and at least two hole-introducing nozzles arranged downward are arranged at the bottom end of the hole-introducing pipe;

A vertical grouting pipe is arranged on the outer wall of the web of the steel sheet pile 2 along its length direction.

Since the geology of some construction sites is relatively complex, air knives or water knives are selectively used to guide holes according to the specific geological information corresponding to different depths. Specifically, if the insertion and driving cannot be in place due to the underlying hard plastic clay or gravel soil environment, high-pressure water jetting is used to assist in the insertion and driving of steel sheet piles 2. By spraying high-pressure water flow, the soil layer in the cavity of the steel sheet pile 2 is impacted, so that the surrounding soil is liquefied after being disturbed, reducing the resistance encountered by the steel sheet pile 2 when it is driven into the soil layer, thereby reducing the possibility of distortion and damage of the steel sheet pile 2 during the insertion and driving process, reducing construction costs, speeding up construction progress, and ensuring construction quality. If the underlying soil is too deep, the steel sheet pile 2 will be easily damaged. The geological environment changes to higher strength soil such as muddy siltstone and strongly weathered rock. At this time, it is difficult to use a water knife to drill a hole. Therefore, the water knife is replaced with an air knife, and a high-pressure gas blow is used to assist the insertion of the steel sheet pile 2. The high-pressure gas will form an air zone in a water-free state at the pile head of the steel sheet pile 2. After isolating the water, the high-pressure gas directly damages the rock formation and floats under the influence of water buoyancy. During the entire drilling process, the geology is liquefied again. This high-pressure gas underwater drilling process has a more direct impact on the geology and more efficient soil disturbance. It can significantly increase the depth of the steel sheet pile 2 into the soil and ensure that the steel sheet pile 2 is driven deeper.

Specifically, compared with the related art that uses a separate mother pile as a guide hole steel plate, the steel sheet pile 2 that needs to be driven in the present steel sheet pile cofferdam construction method is directly used as the guide hole mother pile. Therefore, the steel sheet pile 2 that needs to be driven in is not only a structural component of the cofferdam, but also a mother pile for setting the guide hole pipe and the grouting pipe. As a structural component of the cofferdam, it does not need to be pulled out from the soil layer after the guide hole is completed. While reducing the construction process, it also avoids damaging the soil layer structure during the pulling out process, affecting the subsequent driving of the steel sheet pile 2.

Specifically, a vertically arranged lead-in hole pipe is arranged along the inner wall of the web of the steel sheet pile 2 along its length direction. The lead-in hole pipe is common when using a water knife and an air knife. The lead-in hole pipe is fixed along the length direction of the steel sheet pile 2 by a fixing buckle. Two nozzles are welded at the bottom of the lead-in hole pipe at a distance of about 20 cm from the bottom of the steel sheet pile 2. The nozzle is pointed and the nozzle diameter is about 1 cm. The top of the lead-in hole pipe is connected to a high-pressure water pump or a high-pressure air pump. When using a water knife, first use a vibrating hammer to drive the steel sheet pile 2 into the soil layer 1~2m, and then turn on the high-pressure water pump. The pressure of the high-pressure water pump is controlled at 5~10Mpa, and the nozzle terminal pressure is maintained at 300~500Mpa. It can be tested or adjusted according to the actual situation on site, and water jetting is used to assist the steel sheet pile 2 to sink until it reaches the designed elevation and parked at the designed elevation for 5~10s. When using an air knife, connect the high-pressure air pump. After turning on the high-pressure air pump, the air pump pressure is controlled at 3~15Mpa, and the nozzle terminal pressure is maintained at 300~500Mpa. The specific test or adjustment can be carried out according to the actual situation on site. After the pressure of the high-pressure air pump is basically stable, continue to sink the pile until the designed elevation is reached. Finally, park the steel sheet pile 2 at the designed elevation for 5-10s.

Furthermore, before inserting the steel sheet pile 2, the method further includes:

Apply waterproofing agent on the buckle of steel sheet pile 2;

The waterproofing agent includes silicate cement, quartz sand, anti-seepage material fly ash, silicone hydrophobic powder, HPMC cellulose, polyurethane one-component one-two component type I, polyurethane one-component two-component type II, cement-based penetrating crystallization, polymer cement waterproof coating JS, and the mass ratio of each component is 52:38:5:75:3:10:5:5:10. The quartz sand includes 100 mesh quartz sand and 200 mesh quartz sand, and the mass ratio of 100 mesh quartz sand to 200 mesh quartz sand is 15:4.

Specifically, for the steel sheet pile 2, the closure is mainly carried out by the buckle locks of two adjacent steel sheet piles 2, and the buckle locks are tightly connected and are also rigidly contacted, which has a greater risk of leakage. Therefore, in order to ensure the tightness of the connection between the buckle locks of the steel sheet pile 2 and reduce the possibility of underwater leakage, before the steel sheet pile 2 is inserted, a waterproofing agent is applied to the buckle locks of each steel sheet pile 2. The waterproofing agent is a waterproofing agent prepared for this type of cofferdam, and its components mainly include silicate cement, quartz sand, anti-seepage material fly ash, silicone hydrophobic powder, HPMC cellulose, polyurethane single component single and double component type I, polyurethane single component double component type II, cement-based permeable crystallization, polymer cement waterproof coating JS, and the mass ratio of each component is 52:38:5:75:3:10:5:5:10, wherein the quartz sand includes two different mesh sizes of quartz sand, 100 mesh quartz sand and 200 mesh quartz sand. Among them, the mass of silicate cement is 480~540g, the mass of quartz sand is 360~400g, the mass of anti-seepage material fly ash is 40~60g, the mass of silicone hydrophobic powder is 720~760g, the mass of HPMC cellulose is 20~40g, the mass of polyurethane one-component single-component and two-component type I is 80~120g, the mass of polyurethane one-component and two-component type II is 40~60g, the mass of cement-based permeable crystallization is 40~60g, and the mass of polymer cement waterproof coating JS is 80~120g.

Furthermore, multiple internal support structures are arranged from top to bottom during the excavation process, and the steps include:

Steel purlins are arranged along the inner wall of the steel sheet pile 2 cofferdam;

An internal support structure is provided on the steel perimeter purlin;

Continue to dig downwards and set steel purlins and internal support structures in sequence. The greater the digging depth, the smaller the distance between two adjacent steel purlins or internal support structures.

Specifically, after the steel sheet pile 2 is driven, excavate to 0.5m below the bottom elevation of the first internal support structure, and install the first internal support structure. After the first internal support structure is installed, continue to excavate downward to 0.5m below the bottom of the second internal support structure, and install the second internal support structure. After the second internal support structure is installed, continue to excavate downward to 0.5m below the bottom of the third internal support, and install the third internal support structure. Repeat this process in sequence. Generally, according to the scale of most deep foundation pits at present, it is sufficient to set up about four internal support structures, but the specific number of internal support structures can be determined according to the actual construction depth and scale. Among them, since the scale of deep foundation pits is generally large, in order to ensure the stability of the structure, generally before installing each layer of internal support structure, a steel perimeter purlin structure will be set up first, and then the corresponding internal support structure will be installed on the steel perimeter purlin to ensure that the structure has sufficient strength and stability.

Furthermore, when the foundation pit is excavated to about 15m, a fine-rolled threaded steel tie rod is added to the corresponding surrounding purlin. Because the deeper the excavation depth, the greater the soil pressure on both sides. Under the action of soil pressure, the lower part of the steel sheet pile 2 tends to tilt toward the foundation pit, while the upper part of the steel sheet pile 2 tends to tilt toward the surrounding of the foundation pit. However, the internal support structure can only provide resistance to the inward pressure of the surrounding soil, and cannot resist the outward tilting trend of the top. Therefore, it is necessary to use steel bars to provide tension to resist the upper part of the steel sheet pile 2 from tilting toward the surrounding of the foundation pit. The fine-rolled threaded steel tie rod can provide sufficient tensile strength, so that the force of the foundation pit in the poor stratum is more reasonable, and the safety of the foundation pit is greatly improved. Specifically, after the corresponding surrounding purlin is installed, the steel pipe support with a flange is connected through the reserved bolt hole. At this time, the steel pipe support with a flange is connected to the surrounding purlin and the steel sheet pile 2 through the fine-rolled threaded steel, so that the steel pipe support becomes a tension and compression rod without affecting the removal of the steel pipe support.

The present application also provides a steel sheet pile cofferdam for deep foundation pits, as shown in Figure 2, the steel sheet pile cofferdam mainly includes a cofferdam body 1 and a guide structure 3, wherein the cofferdam body 1 includes a plurality of steel sheet piles 2 connected end to end, and each steel sheet pile 2 is provided with a hole-guiding assembly and a liquid injection assembly, the hole-guiding assembly is used to select a water knife or an air knife to alternately guide holes according to the geological information of the construction site to assist the steel sheet piles 2 to be driven to a preset depth, and the liquid injection assembly is used to inject bottom sealing concrete along the outer wall of the steel sheet pile 2 toward the bottom of the foundation pit to complete the bottom sealing of the foundation pit; the guide structure 3 is arranged along the circumference of the cofferdam body 1, and the guide structure 3 is used to guide the steel sheet piles 2 when they are driven.

Furthermore, the guide structure 3 includes a plurality of steel pipe piles, a part of which is arranged at intervals on the inner side of the steel pipe piles along the arrangement trajectory of the steel sheet piles 2, and the remaining part of the steel pipe piles is arranged at intervals on the outer side of the steel pipe piles along the arrangement trajectory of the steel sheet piles 2, and a plurality of guide I-beams 30 are provided on the tops of the steel pipe piles located on the inner and outer sides, and a plurality of spaced limiting steel bars 31 are slidably arranged on the guide I-beams 30 located on the inner and outer sides; wherein, the guide I-beams 30 are used to limit the deviation of the steel sheet piles 2 in the inner or outer direction when being driven, and the limiting steel bars 31 are used to limit the deviation of the steel sheet piles 2 in the left and right directions when being driven.

Furthermore, for the steel sheet pile 2, the closure is mainly carried out by the buckle of two adjacent steel sheet piles, and the buckle is tightly connected and is also rigid contact, which has a greater risk of leakage. Therefore, in order to ensure the tightness of the connection between the buckle of the steel sheet pile 2 and reduce the possibility of underwater leakage, before the steel sheet pile 2 is inserted, a waterproofing agent is applied to the buckle of each steel sheet pile 2. The waterproofing agent includes silicate cement, quartz sand, anti-seepage material fly ash, silicone hydrophobic powder, HPMC cellulose, polyurethane single component single and double component type I, polyurethane single component double component type II, cement-based permeable crystallization, polymer cement waterproof coating JS, and the mass ratio of each component is A: B: C: D: E: F: G: H: I, and the quartz sand includes 100 mesh quartz sand and 200 mesh quartz sand, and the mass ratio of 100 mesh quartz sand and 200 mesh quartz sand is 15:4.

Among them, the functional implementation of each structure in the above-mentioned steel sheet pile cofferdam corresponds to the various steps in the above-mentioned steel sheet pile cofferdam construction method, and its remaining functions and implementation processes will not be repeated here one by one.

In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims (3)

1. A steel sheet pile cofferdam construction method for a deep foundation pit, characterized in that the steps include: Obtain geological information of the construction site and determine the construction area; Providing a guide structure (3) in the construction area; The steel sheet piles (2) are inserted in sequence under the guidance of the guide structure (3), and during the insertion and driving process, a water jet or an air knife is selected to alternately guide holes according to the acquired geological information, so as to assist the steel sheet piles (2) to be inserted and driven to a preset depth; The steel sheet piles (2) are connected together, the foundation pit is excavated, and a plurality of internal support structures are arranged from top to bottom during the excavation process; Injecting bottom sealing concrete along the outer side wall of the steel sheet pile (2) toward the bottom of the foundation pit to complete the bottom sealing of the foundation pit; Before inserting the steel sheet pile (2), the method further comprises: A vertically arranged hole-introducing pipe is arranged on the inner wall of the web of the steel sheet pile (2) along its length direction, and at least two hole-introducing nozzles arranged downward are arranged at the bottom end of the hole-introducing pipe; A grouting pipe is vertically arranged on the outer wall of the web of the steel sheet pile (2) along its length direction; Before inserting the steel sheet pile (2), the method further comprises: Applying a waterproofing agent on the buckle of the steel sheet pile (2); The waterproofing agent includes silicate cement, quartz sand, anti-seepage material fly ash, silicone hydrophobic powder, HPMC cellulose, polyurethane single-component single-component type I, polyurethane single-component type II, cement-based permeable crystallization, polymer cement waterproof coating JS, and the mass ratio of each component is 52:38:5:75:3:10:5:5:10. The quartz sand includes 100-mesh quartz sand and 200-mesh quartz sand, and the mass ratio of 100-mesh quartz sand to 200-mesh quartz sand is 15:4. The steps of setting up multiple inner support structures from top to bottom during the excavation process include: Steel purlins are arranged along the inner wall of the steel sheet pile (2) cofferdam; An internal supporting structure is provided on the steel purlin; Continue digging downwards, and sequentially set the steel perimeter purlins and the inner support structure, and the greater the digging depth, the smaller the distance between two adjacent steel perimeter purlins or inner support structures; When the foundation pit is excavated to 15m, install the precision-rolled threaded steel tie rod on the corresponding steel purlin to connect the steel purlin and the steel sheet pile; During the driving process, a water jet or an air jet is selected to alternately guide holes according to the acquired geological information to assist in driving the steel sheet pile (2) to a preset depth, the steps comprising: Determine the geological information of the current drilling depth. If the geological information of the current drilling depth is hard plastic clay or gravel soil, use a water knife to guide the hole. If the geological information of the current drilling depth is muddy siltstone or strongly weathered rock, use an air knife to guide the hole. During the driving process, a water knife or an air knife is selected to alternately drill holes according to the geological information until the steel sheet pile (2) is driven to the preset depth; The nozzle of the orifice-introducing nozzle is pointed, and the diameter of the nozzle is 1 cm; When using a water jet, connect the top of the orifice tube to a high-pressure water pump with a pressure of 5-10 MPa, and keep the terminal pressure of the orifice nozzle at 300-500 MPa. When using an air knife, connect the top of the orifice tube to a high-pressure air pump with an air pump pressure of 3-15 MPa, and maintain the nozzle terminal pressure at 300-500 MPa. 2. A steel sheet pile cofferdam construction method for a deep foundation pit according to claim 1, characterized in that the guide structure (3) is provided at a preset position in the construction area, and the steps include: Determining the driving points of the steel sheet piles (2) in sequence within the construction area; Sequentially driving a plurality of steel pipe piles on the inner side and the outer side of a circle of driving points along the arrangement track of the driving points, and after driving is completed, respectively setting guide I-beams (30) on the tops of the steel pipe piles located on the inner side and the outer side; A plurality of spaced-apart limiting steel bars (31) are slidably mounted on the guide I-beams (30) located on the inner and outer sides. 3. A steel sheet pile cofferdam construction method for a deep foundation pit according to claim 2, characterized in that the steel sheet piles (2) are inserted and driven in sequence under the guidance of the guide structure (3), and the steps further include: Adjusting one of the limiting steel bars (31) to one side of the corresponding insertion point; The steel sheet pile (2) is driven in, and during the driving process, the guide I-beams (30) located on the inner side and the outer side are respectively used to assist in correcting the position of the steel sheet pile (2) in the direction from the inner side to the outer side, and the limiting steel bar (31) is also used to assist in correcting the position of the steel sheet pile (2) in the left-right direction.