A foundation pit retaining structure and construction method

Abstract

The present invention discloses a foundation pit retaining structure and a construction method. A foundation pit retaining structure includes a foundation pit, and a number of retaining piles are evenly spaced around the foundation pit. The tops of the number of retaining piles are fixedly connected by a capping beam. A number of support assemblies are arranged in the foundation pit, and the support assemblies are supported on one side of the retaining piles. The support assemblies are connected into a whole by a connecting beam; a reinforced cushion assembly is arranged around the bottom of the foundation pit, and the bottom of the support assembly passes through the reinforced cushion assembly and is embedded deep in the soil layer; a construction method of a foundation pit retaining structure includes retaining pile construction, first support construction, excavation of the first layer of soil, excavation of the second layer of soil and foundation pit backfilling. This structure is stable and reliable, applicable to foundation pit excavations of various specifications, especially suitable for reducing the construction deformation of deeper foundation pits, and some structures can be recycled. During the whole construction process, the construction of the foundation pit retaining structure is organically combined with the construction of the building structure inside the pit, and the whole foundation pit construction process is safe and orderly with a short construction period.

Description

Technical Field

[0001] The present invention relates to the technical field of underground engineering construction, and particularly relates to a foundation pit retaining structure and a construction method thereof. Background Technique

[0002] With the continuous development and construction of cities, foundation pit projects are gradually developing in the direction of greater depth and scale, and the construction environment is becoming increasingly complex. For large-area deep foundation pit projects, in engineering practice, a support or pile-anchor system is often adopted. When the excavation area of the foundation pit is large, due to the excessive slenderness ratio of the support, it is often necessary to construct in separate pits, which will inevitably have a greater impact on the construction period and economy. At the same time, the setting of the internal support system also has many restrictions on earth excavation. The pile-anchor system often needs to occupy the space outside the site, which has a greater impact on the surrounding environment and has many restrictions in urban construction. Therefore, these two systems often have certain limitations in engineering applications. Foundation pit projects are generally temporary underground structures. How to adopt a reasonable retaining and support system while ensuring safety and comprehensively considering factors such as economy and construction period is a problem that should be considered in the design of foundation pit projects.

[0003] After retrieval, it is found that a Chinese patent with the application number CN 106013172 B discloses a combined retaining structure of double-row piles and inclined struts for deep soft soil foundation pits and a construction method thereof. In this patent, a bottom support pier is set at the connection between the inclined strut and the foundation raft to transmit the support force to the bottom plate. Although this patent adopts an inclined strut, the inclined strut does not extend deep into the soil layer, so the ability to control deformation is poor. At the same time, when constructing this patent, soil needs to be left on the edge of the pit for later excavation, and the bottom plate needs to be constructed in two times, which has a greater impact on the construction period. Moreover, if there are buildings on the edge of the pit, the construction difficulty of the foundation pit is greater.

[0004] A Chinese patent with the application number CN 211922637 U discloses an A-shaped double-row pile foundation pit support with inclined struts between piles. The retaining structure of this patent mainly uses the front-row piles as the retaining structure and the rear-row piles as the support structure, and inclined struts are set between the front-row and rear-row piles. Since the front-row piles are single piles, the stability and deformation resistance of the retaining structure are poor, and it is often applicable to relatively shallow foundation pits with one basement floor. At the same time, the inclined struts between piles only support to the center position of the rear-row piles, which is likely to cause engineering risks such as the breakage of the rear-row piles, and the rear-row piles need to penetrate the structural bottom plate, which has high requirements for the waterproofing of the bottom plate.

[0005] The Chinese patent with the application number CN 114197483 A discloses a foundation pit retaining structure and its construction method. The invention includes a plurality of columns, grouting inclined support pipes and connecting inclined support pipes. By opening insertion holes in the capping beam, a common inclined support pipe is movably connected in the insertion holes. A fixing mechanism is provided between the common inclined support pipe and the capping beam, and an adjusting mechanism is provided between the grouting inclined support pipe and the connecting inclined support pipe. The top of the grouting inclined support pipe is movably connected with a rotating pipe, which solves the problems in the prior art that the grouting inclined support pipe inclined support combination structure cannot actively control the deformation of the foundation pit, and the fixed connection of the inclined support pipe cannot be retracted, which increases the structural use cost. However, the invention does not solve the problems such as the mutual relationship between the grouting inclined support pipe and the main underground structure.

[0006] In summary, the existing similar foundation pit support forms mainly adopt two combinations: double-row piles + inclined supports or single-row piles + inclined supports. Both of these retaining forms have certain limitations: in the double-row piles + inclined support combination, the inclined support generally supports on the bottom slab, the soil needs to be left on the pit side and then excavated later, and the bottom slab needs to be constructed in two times, which has a greater impact on the construction period. At the same time, the inclined support supports on the bottom slab, and the force transmission is poor, and the effect of controlling the foundation pit deformation is poor, which has a certain limitation on the excavation depth of the foundation pit; in the single-row piles + inclined support combination, the ability of the single-row piles to control deformation and stability is poor, and the inclined support needs to penetrate the bottom slab, which has a high waterproof requirement for the bottom slab. Generally, it is also applicable to relatively shallow foundation pits. Summary of the Invention

[0007] The purpose of the present invention is to provide a foundation pit retaining structure and its construction method. The structure is fixedly connected into a whole in the foundation pit, comprehensively solves the foundation pit waterproof problem, and the retaining process is stable and reliable. It is applicable to the excavation of foundation pits of various specifications, especially suitable for reducing the construction deformation of deeper foundation pits. During the whole construction process, the construction of the foundation pit retaining structure is organically combined with the construction of the building structure in the pit, so that the whole foundation pit project can be carried out safely and orderly.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A foundation pit retaining structure includes a foundation pit. A number of retaining piles are evenly spaced around the foundation pit. The tops of the number of retaining piles are fixedly connected by a capping beam. A number of support assemblies are arranged in the foundation pit. The support assemblies support on one side of the retaining piles, and the support assemblies are connected into a whole by a connecting beam; a reinforced cushion assembly is arranged around the bottom of the foundation pit, and the bottom of the support assembly passes through the reinforced cushion assembly and is inserted deep into the soil layer.

[0010] The support assembly includes a first support that is obliquely supported between the capping beam and the bottom of the foundation pit. The first support is arranged corresponding to the retaining pile, and a second support is also abutted and supported between the first support and the retaining pile. The first support includes a diagonal support pipe with a pouring head at the bottom. The top end of the diagonal support pipe is anchored at the capping beam, and the bottom end of the diagonal support pipe is inserted deep into the soil layer. The second support includes a support cross beam that abuts between the retaining pile and the first support, and a steel column with its top supported at the bottom of the support cross beam. The bottom end of the steel column is inserted deep into the soil layer.

[0011] The reinforced cushion assembly includes a reinforced cushion and a plurality of inserted bars evenly spaced at the bottom of the reinforced cushion. The reinforced cushion is formed by double-sided and double-directional reinforcement and concrete pouring, and is laid around the bottom surface of the foundation pit and is inserted into the soil layer at the bottom of the foundation pit through the inserted bars.

[0012] Preferably, a number of vertical water-stop piles are arranged between the retaining pile and the side wall of the foundation pit.

[0013] Preferably, a number of anchor bars are arranged around the top of the diagonal support pipe, and the anchor bars are tied into one body with the steel bar structure in the capping beam.

[0014] Preferably, one end of the support cross beam is fixedly connected to the retaining pile through a double-ply waling, and the other end of the support cross beam is fixedly connected to the diagonal support pipe.

[0015] Preferably, the double-ply waling is a quadrilateral structure made of I-beam, channel steel or steel plate; the support cross beam is a rod-shaped structure made of circular steel pipe or square steel pipe.

[0016] Preferably, the connecting beam is made of I-beam or channel steel and is connected between adjacent support cross beams.

[0017] Preferably, a building structure inside the pit is arranged on the upper side of the reinforced cushion assembly. The building structure inside the pit includes a bottom slab. The building structure inside the pit is connected to the retaining pile through a load transfer belt. The diagonal support pipe obliquely passes through the building structure inside the pit and the reinforced cushion assembly in sequence and is inserted deep into the soil layer. A water-stop steel plate is arranged at the intersection position of the diagonal support pipe and the middle of the bottom slab.

[0018] Preferably, one end of the load transfer belt is pre-embedded and poured on one side of the building structure inside the pit, and the other end of the load transfer belt is anchored into the retaining pile; the load transfer belt includes a bottom slab load transfer belt and a middle floor load transfer belt. The main body of the bottom slab load transfer belt is arranged on the upper part of the reinforced cushion assembly. One end of the bottom slab load transfer belt is pre-embedded and poured at one end of the bottom slab, and the other end of the bottom slab load transfer belt is anchored into the retaining pile; one side of the steel bars of the middle floor load transfer belt is anchored into the middle floor, and the other side is welded to the main bars of the retaining pile through suspension bars; the middle floor load transfer belt is arranged in the gap of the first support and is arranged at equal intervals along the perimeter of the foundation pit.

[0019] A construction method for a foundation pit retaining structure includes the following steps:

[0020] Step 1: Construction of retaining piles. According to the drawing surveying and mapping for lofting, mark and position the retaining piles and vertical water-stop piles on site, and complete the construction of the retaining piles and vertical water-stop piles.

[0021] Step 2: Construction of the first support. After jacking the inclined support pipe to a specified depth in the soil layer, first pour graded broken stones into the inclined support pipe, and then pour pure cement into the inclined support pipe until the top of the inclined support pipe. Several anchor bars are evenly connected around the top of the inclined support pipe by welding. The anchor bars are tied and concreted with the steel bar structure in the capping beam.

[0022] Step 3: Excavation of the first layer of soil. Excavate the soil layer in layers and blocks to the design position of the support crossbeam, install several groups of the second support, and fixedly connect adjacent second supports through the connecting beam. All the second supports in the foundation pit are connected into a whole.

[0023] Step 4: Excavation of the second layer of soil. Excavate in layers and blocks to the bottom of the foundation pit, construct the reinforced cushion assembly, then construct the bottom slab and the bottom slab load transfer belt. A water-stop steel plate is set at the intersection of the middle part of the bottom slab and the inclined support pipe. After the strength of the bottom slab and the bottom slab load transfer belt reaches the requirement, remove the connecting beam and the second support; continue to construct the middle floor and the middle floor load transfer belt. After the strength of the middle floor and the middle floor load transfer belt reaches the requirement, cut one end of the inclined support pipe flush with the top surface of the bottom slab and the other end flush with the side surface of the retaining pile.

[0024] Step 5: Backfilling of the foundation pit. Construct the building structure in the pit to ±0.000, and backfill the foundation pit.

[0025] In the present invention, the foundation pit retaining structure is fixedly connected into a whole by several groups of support components. The whole structure is stable and reliable, improving the safety of the foundation pit retaining, having low requirements for the construction environment, being applicable to the excavation of foundation pits of various specifications, and especially applicable to reducing the construction deformation of deeper foundation pits.

[0026] The first support includes an inclined support pipe. The inclined support pipe can not only play a supporting role, but also serve as a perfusion channel after being in place. Pour graded broken stones and pure cement into the inclined support pipe from the top of the inclined support pipe to form a casting head at the bottom of the inclined support pipe, so as to increase the contact area between the first support and the soil layer, achieve the purpose of increasing the connection strength and preventing subsidence. Compared with precast concrete piles, it has good economy and the inclined support pipe part can be recycled.

[0027] The second support is arranged between the first support and the retaining pile, increasing the support strength of the first support, preventing the first support from deforming, reducing the deformation of the foundation pit side wall, and improving the safety and reliability of the whole foundation pit retaining structure.

[0028] The reinforced cushion assembly is arranged around the bottom of the foundation pit, which can effectively reduce the bottom deformation when the foundation pit is excavated to the bottom.

[0029] A number of vertical water-stop piles are arranged between the retaining piles and the side wall of the foundation pit to play the roles of waterproofing and soil retaining;

[0030] The construction method of the foundation pit retaining structure is organically combined with the construction of the foundation pit excavation and the in-pit building structure. The foundation pit excavation is not restricted, the construction process is simple, the construction period is short, and the economy is good. Brief Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 It is a top view of the overall structure of the present invention;

[0033] Figure 3 It is a welding schematic diagram between the support assembly and the connecting beam of the present invention;

[0034] Figure 4 It is a connection schematic diagram between the inclined strut pipe and the capping beam of the present invention;

[0035] Figure 5 It is a welding schematic diagram between the support cross beam and the inclined strut pipe of the present invention;

[0036] Figure 6 It is a welding schematic diagram between the support cross beam and the steel column of the present invention;

[0037] Figure 7 It is a schematic diagram of the in-pit building structure provided on the overall structure of the present invention;

[0038] Figure 8 It is a connection schematic diagram between the in-pit building structure and the retaining pile;

[0039] Figure 9 It is a schematic diagram of the setting of the water-stop steel plate;

[0040] Figure 10 It is a construction schematic diagram corresponding to Step 1;

[0041] Figure 11 It is a construction schematic diagram corresponding to Step 2;

[0042] Figure 12 It is a construction schematic diagram corresponding to Step 3;

[0043] Figure 13 It is one of the construction schematic diagrams corresponding to Step 4;

[0044] Figure 14 It is another construction schematic diagram corresponding to Step 4;

[0045] Figure 15 It is the third construction schematic diagram corresponding to Step 4;

[0046] Figure 16It is the construction schematic diagram corresponding to Step 5.

[0047] In the figure: 1, retaining piles; 2, support components; 3, in-pit building structures; 4, reinforced cushion components; 5, load transfer belts; 6, connecting beams; 10, capping beams; 11, vertical water-stop piles; 20, first supports; 21, second supports; 30, water-stop steel plates; 31, floor slabs; 40, reinforced cushions; 41, inserted bars; 50, floor slab load transfer belts; 51, middle floor slab load transfer belts; 200, inclined support pipes; 201, pouring heads; 210, support cross beams; 211, steel columns; 212, double-ply purlins. Specific implementation manners

[0048] The following further describes the present invention in conjunction with the accompanying drawings:

[0049] Example 1:

[0050] As Figure 1 and Figure 2 shown, a foundation pit retaining structure includes a foundation pit. A number of retaining piles 1 are evenly and spacedly arranged around the foundation pit. The tops of the number of retaining piles 1 are fixedly connected through a capping beam 10. The retaining piles 1 are cast-in-place piles, and the pile diameter, pile length, and reinforcement of the cast-in-place piles are determined through calculation. A number of groups of support components 2 are arranged in the foundation pit. The support components 2 are supported on one side of the retaining piles 1. The support components 2 are connected into a whole through connecting beams 6. The interaction between the support components 2 will generate support forces and tensile forces, preventing a single group of support components 2 from tipping over, improving the stability of the support components 2, and increasing the reliability during the retaining support of the foundation pit. As Figure 3 shown, the support components 2 and the connecting beams 6 are connected by welding. The connecting beams 6 are connected between adjacent two support cross beams 210. In specific implementation, the connecting beams 6 are made of I-beams or channel steels. Reinforced cushion components 4 are arranged around the bottom of the foundation pit. The bottoms of the support components 2 pass through the reinforced cushion components 4 and are inserted deep into the soil layer. The reinforced cushion components 4 include a reinforced cushion 40 and a number of inserted bars 41 evenly and spacedly arranged at the bottom of the reinforced cushion 40. The reinforced cushion 40 is formed by double-sided two-way reinforcement and concrete pouring. The concrete selected for the reinforced cushion 40 is not less than C30, with C12@200 double-sided two-way reinforcement built-in. The inserted bars are C12 steel bars with a length of 1500 mm, the interval of the inserted bars is 1 m, and the inserted bars are anchored 150 mm deep into the reinforced cushion. The reinforced cushion 40 is laid around the bottom surface of the foundation pit and is plugged into the soil layer at the bottom of the foundation pit through the inserted bars 41.

[0051] The support assembly 2 includes a first support 20 that is obliquely supported between the capping beam 10 and the bottom of the foundation pit. The first support 20 is arranged corresponding to the retaining pile 1. The included angle between the first support 20 and the retaining pile 1 is greater than 35°. A second support 21 is also abutted and supported between the first support 20 and the retaining pile 1. The first support 20 includes a diagonal bracing pipe 200, and the diagonal bracing pipe 200 can be a circular steel pipe or a square steel pipe. The diagonal bracing pipe 200 can not only play a supporting role, but also serve as a grouting channel after the diagonal bracing pipe 200 is in place. Gradation gravel and pure cement are grouted into the diagonal bracing pipe 200 from the top of the diagonal bracing pipe 200 to form a pouring head at the bottom of the diagonal bracing pipe 200, so as to increase the contact area between the first support and the soil layer, achieve the purpose of increasing the connection strength and preventing subsidence. Compared with precast concrete piles, it has good economy and the diagonal bracing pipe 200 can be partially recycled. The top end of the diagonal bracing pipe 200 is anchored at the capping beam 10. In a more optimal embodiment, as shown in Figure 4, several anchor bars are arranged around the top of the diagonal bracing pipe 200, and the anchor bars are tied into one body with the steel bar structure in the capping beam 10. Therefore, in specific implementation, the first support 20 and the capping beam 10 are poured simultaneously, and the bottom of the diagonal bracing pipe 200 is inserted deep into the soil layer; the second support 21 includes a support cross beam 210 that abuts between the retaining pile 1 and the first support 20, and a steel column 211 whose top end is supported at the bottom of the support cross beam 210. As Figure 5 and Figure 6 shown, the support cross beam 210 is welded to the diagonal bracing pipe 200, and the support cross beam 210 is welded to the steel column 211. The weld thickness is not less than 10mm, and the bottom end of the steel column 211 is inserted deep into the soil layer.

[0052] Embodiment 2

[0053] As Figure 1 and Figure 2 shown, for a foundation pit retaining structure, several vertical water-stop piles 11 are arranged between the retaining pile 1 and the side wall of the foundation pit to play the role of waterproofing and soil retaining. The vertical water-stop piles 11 are three-axis mixing piles, and the three-axis mixing piles are arranged in a socketed hole manner. The pile bottom elevation is below 7m of the bottom of the foundation pit.

[0054] In this example, one end of the support cross beam 210 is fixedly connected to the retaining pile 1 through a double-ply purlin 212, and the other end of the support cross beam 210 is fixedly connected to the diagonal bracing pipe 200 by welding. The double-ply purlin 212 is a quadrilateral structure made of I-beam, channel steel, steel plate or other section steels. Specifically, a section steel with a size of (height × width × web thickness × flange thickness) 2H700×300×13×24 is selected and made into a double-ply. One end of the double-ply purlin 212 is pre-buried and poured on one side of the retaining pile 1, and the other end of the double-ply purlin 212 is fixedly connected to the support cross beam 210 by welding. The support cross beam 210 is a rod-shaped structure made of a circular steel pipe or a square steel pipe. Specifically, the support cross beam 210 is a circular steel pipe with a diameter of 609mm and a wall thickness of 16mm.

[0055] As Figure 7 and Figure 8 shown, a building structure 3 in the pit is arranged on the upper side of the reinforced cushion component 4. The building structure 3 in the pit includes a bottom slab 31. The building structure 3 in the pit is connected to the retaining pile 1 through a force transfer belt 5. The inclined support pipe 200 sequentially passes through the building structure 3 in the pit and the reinforced cushion component 4 and is inserted into the deep soil layer. A water stop steel plate 30 is arranged at the intersection position of the inclined support pipe 200 and the middle part of the bottom slab 31. As Figure 9 shown, the inclined support pipe 200 passes through the water stop steel plate 300, and the outer wall of the inclined support pipe 200 is welded to the water stop steel plate 300 as a whole. One end of the force transfer belt 5 is pre-buried and cast on one side of the building structure 3 in the pit, and the other end of the force transfer belt 5 is anchored into the retaining pile 1. The force transfer belt 5 includes a bottom slab force transfer belt 50 and a middle floor force transfer belt 51. The main body of the bottom slab force transfer belt 50 is arranged on the upper part of the reinforced cushion component 4. One end of the bottom slab force transfer belt 50 is pre-buried and cast at one end of the bottom slab 31, and the other end of the bottom slab force transfer belt 50 is anchored into the retaining pile 1. The middle floor force transfer belt 51 is cast simultaneously with the middle floor. One side of the steel bars of the middle floor force transfer belt 51 is anchored into the middle floor, and the other side is welded to the main bars of the retaining pile 1 through suspender bars. The middle floor force transfer belt 51 is arranged in the gap of the first support 20 and is arranged at equal intervals along the perimeter of the foundation pit.

[0056] A construction method for a foundation pit retaining structure includes the following steps:

[0057] Step 1, construction of the retaining pile 1. As Figure 10 shown, according to the drawing surveying and mapping lofting, the positions of the retaining pile 1 and the vertical water stop pile 11 are marked on the site, and the construction of the retaining pile 1, the capping beam 10 and the vertical water stop pile 11 is completed;

[0058] Step 2, construction of the first support 20. As Figure 11 shown, after the inclined support pipe 200 is jacked into the soil layer to the specified depth, first graded gravel is poured into the inclined support pipe 200, and then pure cement is poured into the inclined support pipe 200 to the top of the inclined support pipe 200. A number of anchor bars are evenly connected around the top of the inclined support pipe 200 by welding, and the anchor bars are tied and cast with the steel bar structure in the capping beam 10;

[0059] Step 3, excavation of the first layer of soil. As Figure 12 shown, the soil layer is excavated in layers and blocks to the design position of the support cross beam 210, and a number of groups of second supports 21 are erected. The adjacent second supports 21 are fixedly connected through the connecting beam 6, and all the second supports 21 in the foundation pit are connected into a whole. In this example, the steel columns 211 and the connecting beam 6 are both selected as I-beams with a specification of (dimensions: height × width × web thickness × flange thickness) H400×400×13×21;

[0060] Step 4, excavation of the second layer of soil. As Figure 13 and Figure 14As shown in the figure, the excavation is carried out in layers and blocks to the bottom of the foundation pit. The reinforced cushion component 4 is constructed, and then the bottom slab 31 and the bottom slab load transfer belt 50 are constructed. A water stop steel plate 30 is arranged at the intersection of the middle of the bottom slab 31 and the inclined support pipe 200; after the bottom slab 31 and the bottom slab load transfer belt 50 reach 80% of the designed strength, the connecting beam 6 and the second support 21 are removed, and the middle floor and the middle floor load transfer belt 51 are continuously constructed. After the middle floor and the middle floor load transfer belt 51 reach 80% of the designed strength, one end of the inclined support pipe 200 is cut off flush with the top surface of the bottom slab 31, and the other end is cut off flush with the side surface of the retaining pile 1;

[0061] Step Five, backfill the foundation pit. As Figure 16 shown in the figure, construct the in-pit building structure 3 to the plus-minus zero level and carry out the backfill of the foundation pit.

[0062] The above embodiments are only several descriptions of the concept and implementation of the present invention, and are not intended to limit it. Under the concept of the present invention, the technical solutions without substantial transformation are still within the protection scope.

Claims

1. A foundation pit retaining structure, comprising a foundation pit, and a plurality of retaining piles (1) are evenly spaced around the foundation pit. The retaining piles (1) are cast-in-place piles, and the tops of the plurality of retaining piles (1) are fixedly connected through a capping beam (10). It is characterized in that: Several groups of support components (2) are arranged in the foundation pit. The support components (2) are supported on one side of the retaining pile (1), and the support components (2) are connected into a whole through the connecting beam (6); a reinforced cushion component (4) is arranged around the bottom of the foundation pit, and the bottom of the support component (2) passes through the reinforced cushion component (4) and is inserted deep into the soil layer; The support component (2) includes a first support (20) obliquely supported between the capping beam (10) and the bottom of the foundation pit. The first support (20) is arranged corresponding to the retaining pile (1), and a second support (21) is also abutted and supported between the first support (20) and the retaining pile (1); the first support (20) includes a diagonal brace pipe (200), a pouring head (201) is arranged at the bottom of the diagonal brace pipe (200), the top end of the diagonal brace pipe (200) is anchored at the capping beam (10), and the bottom of the diagonal brace pipe (200) is inserted deep into the soil layer; the second support (21) includes a support cross beam (210) abutted between the retaining pile (1) and the first support (20), and a steel column (211) with the top end supported at the bottom of the support cross beam (210), and the bottom end of the steel column (211) is inserted deep into the soil layer; the included angle between the first support (20) and the retaining pile (1) is greater than 35°; The reinforced cushion component (4) includes a reinforced cushion (40) and a plurality of inserted bars (41) evenly spaced at the bottom of the reinforced cushion (40). The reinforced cushion (40) is made of double-sided two-way reinforcement and concrete pouring, and the reinforced cushion (40) is laid around the bottom surface of the foundation pit and is inserted into the soil layer at the bottom of the foundation pit through the inserted bars (41); A number of vertical water-stop piles (11) are arranged between the retaining pile (1) and the side wall of the foundation pit; The connecting beam (6) is made of I-beam or channel steel, and the connecting beam (6) is connected between two adjacent support cross beams (210).

2. The foundation pit retaining structure according to claim 1, characterized in that: A number of anchor bars are arranged around the top of the diagonal brace pipe (200), and the anchor bars are tied into one body with the steel bar structure in the capping beam (10).

3. The foundation pit retaining structure according to claim 1, characterized in that: One end of the support cross beam (210) is fixedly connected with the retaining pile (1) through a double-spliced purlin (212), and the other end of the support cross beam (210) is fixedly connected with the diagonal brace pipe (200).

4. The foundation pit retaining structure according to claim 3, characterized in that: The double-spliced purlin (212) is a quadrilateral structure made of I-beam, channel steel or steel plate; the support cross beam (210) is a rod-shaped structure made of round steel pipe or square steel pipe.

5. The foundation pit retaining structure according to any one of claims 1 to 4, characterized in that: A building structure (3) inside the pit is arranged on the upper side of the reinforced cushion component (4). The building structure (3) inside the pit includes a floor slab (31). The building structure (3) inside the pit is connected with the retaining pile (1) through a load transfer belt (5). The diagonal brace pipe (200) is obliquely inserted through the building structure (3) inside the pit and the reinforced cushion component (4) and is inserted deep into the soil layer. A water-stop steel plate (30) is arranged at the intersection position of the diagonal brace pipe (200) and the middle of the floor slab (31).

6. The foundation pit retaining structure according to claim 5, characterized in that: One end of the force transfer belt (5) is pre-embedded and cast on one side of the building structure (3) in the pit, and the other end of the force transfer belt (5) is anchored into the retaining pile (1); the force transfer belt (5) includes a bottom plate force transfer belt (50) and a middle floor force transfer belt (51). The main body of the bottom plate force transfer belt (50) is arranged on the upper part of the reinforced cushion assembly (4). One end of the bottom plate force transfer belt (50) is pre-embedded and cast at one end of the bottom plate (31), and the other end of the bottom plate force transfer belt (50) is anchored into the retaining pile (1); one side of the steel bars of the middle floor force transfer belt (51) is anchored into the middle floor, and the other side is welded to the main bars of the retaining pile (1) through suspension bars; the middle floor force transfer belt (51) is arranged in the gap of the first support (20) and is arranged at equal intervals along the perimeter of the foundation pit.

7. A construction method of a foundation pit retaining structure according to any one of claims 1 to 6, characterized in that, It includes the following steps: Step 1: Construction of the retaining pile (1). According to the drawing surveying and mapping lofting, mark and position the retaining pile (1) and the vertical water stop pile (11) on site, and complete the construction of the retaining pile (1), the capping beam (10) and the vertical water stop pile (11). Step 2: Construction of the first support (20). After the inclined support pipe (200) is jacked into the soil layer to the specified depth, first pour graded gravel into the inclined support pipe (200), and then pour pure cement into the inclined support pipe (200) until the top of the inclined support pipe (200). Several anchor bars are evenly connected around the top of the inclined support pipe (200) by welding, and the anchor bars are tied and cast with the steel bar structure in the capping beam (10). Step 3: Excavation of the first layer of soil. Excavate the soil layer in layers and blocks to the design position of the support cross beam (210), erect several groups of second supports (21), and fixedly connect the adjacent second supports (21) through the connecting beam (6). All the second supports (21) in the foundation pit are connected into a whole. Step 4: Excavation of the second layer of soil. Excavate in layers and blocks to the bottom of the foundation pit, construct the reinforced cushion assembly (4), and then construct the bottom plate (31) and the bottom plate force transfer belt (50). A water stop steel plate (30) is set at the intersection of the middle of the bottom plate (31) and the inclined support pipe (200); after the strength of the bottom plate (31) and the bottom plate force transfer belt (50) reaches the requirement, remove the connecting beam (6) and the second support (21), and continue to construct the middle floor and the middle floor force transfer belt (51). After the strength of the middle floor and the middle floor force transfer belt (51) reaches the requirement, cut one end of the inclined support pipe (200) flush with the top surface of the bottom plate (31) and the other end flush with the side surface of the retaining pile (1). Step 5: Backfilling of the foundation pit. Construct the building structure (3) in the pit to ±0, and backfill the foundation pit.

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