Building construction foundation pit supporting structure and supporting method thereof

Abstract

The invention discloses a building construction foundation pit supporting structure and a supporting method thereof. The structure comprises a foundation, fender posts, water stop piles, supporting piles, a top beam, a waist beam, anchor cables, a slope protection concrete layer, a soil nailing wall concrete layer, a gravel cushion layer, a water suction pump, a water suction pipe, a well lid, a deepened bearing platform, a reinforced brick tire film and a well casing. The method comprises the steps of 1, field leveling; step 2, enclosure system construction; thirdly, a water stop system is constructed; fourthly, well point dewatering construction is conducted; 5, layered earth excavation is conducted; sixthly, a pit bottom cushion layer is constructed; the pit bottom multi-layer composite cushion layer structure is designed, the gravel cushion layer with the appropriate thickness is laid at the pit bottom so that redundant water can be rapidly removed, the foundation bearing capacity can be enhanced, then the reinforced thickened concrete cushion layer is additionally arranged on the gravel cushion layer, and the overall strength and rigidity of the cushion layer are improved through a reinforcing mesh or a fiber reinforced material; upper loads are effectively dispersed, and pit bottom soil is prevented from further extrusion deformation.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit support, and in particular to a construction foundation pit support structure and a support method thereof. Background Art

[0002] Foundation pit support is a technology widely used in civil engineering, mainly used to improve the foundation stability of buildings. The construction of medium and high-rise buildings, underground transportation, underground pipelines and other projects in cities requires a large number of foundation pit support projects; these projects are often located in the city center or prosperous areas, with complex construction conditions, and the requirements for foundation pit support technology are also correspondingly increased.

[0003] The existing support structures and methods have the following defects: First, after the foundation pit is excavated, if the local soil at the bottom of the pit is soft strata such as silt and silty soil, these soils have the characteristics of strong fluidity and low bearing capacity, which can easily cause adverse geological phenomena such as soil squeezing, uplift and upwelling of the silty soil at the bottom of the pit. These phenomena will not only pose a serious threat to the stability of the foundation pit, but may also cause the foundation settlement and cracking of surrounding buildings, thereby affecting the safety of the entire construction area; Second, the current support structures and methods often lack a complete and efficient support, support, water-stopping and drainage system; the support structure is mainly used to resist the soil pressure on the side wall of the foundation pit, while the support system is used to support the support structure to prevent it from becoming unstable due to soil pressure; however, in the absence of effective water-stopping measures, groundwater may seep in and cause the foundation pit to collapse. Penetrate into the foundation pit, increase the load of the support structure, and even cause the failure of the support structure; at the same time, if the drainage system is not perfect, the accumulated water in the foundation pit cannot be discharged in time, which will also have an adverse effect on the stability of the foundation pit and the construction efficiency; third, the existing support structures and methods have poor adaptability and are difficult to adapt to different construction environments and geological conditions; with the acceleration of urbanization and the continuous development of underground space, the scale and complexity of foundation pit projects are also increasing; however, the existing support structures and methods are often too single and fixed, and cannot be flexibly adjusted and optimized according to different geological conditions, groundwater levels and construction requirements; this leads to the actual construction, which often requires a lot of manpower, material and financial resources to deal with various emergencies and problems, seriously affecting the construction efficiency and project quality. Summary of the invention

[0004] The object of the present invention is to provide a foundation pit support structure and a support method thereof for solving the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a construction foundation pit support structure, including a foundation, wherein retaining piles, water-stop piles and supporting piles are arranged in the foundation, a crown beam and a waist beam are fixedly connected to the supporting piles, a concrete retaining wall is fixedly connected to an outer wall on one side of the foundation, and the concrete retaining wall is fixedly connected to the supporting piles and the waist beam, an anchor cable is fixedly connected to the waist beam, and the anchor cable is arranged in the foundation, a deepened pedestal is opened on the foundation, a foundation beam is arranged in the deepened pedestal, a reinforced brick membrane is fixedly connected to the inner wall of the deepened pedestal, a sand and gravel cushion layer is arranged on the surface of the foundation, and a reinforced thickened concrete cushion layer is arranged on the sand and gravel cushion layer.

[0006] As a further technical solution of the present invention, a first steel mesh is fixedly connected to the outer wall of one side of the foundation, a slope protection concrete layer is fixedly connected to the first steel mesh, a first drainage hole is opened on the slope protection concrete layer, a fixed steel bar is fixedly connected to the outer wall of one side of the foundation, a second steel mesh is arranged on the fixed steel bar, a soil nail wall concrete layer is fixedly connected to the second steel mesh, and a second drainage hole is opened on the soil nail wall concrete layer.

[0007] As a further technical solution of the present invention, a first drainage ditch and a second drainage ditch are respectively opened on the foundation at positions corresponding to the slope protection concrete layer and the soil nail wall concrete layer.

[0008] As a further technical solution of the present invention, a drainage well hole is opened on the foundation, a well pipe is sleeved in the drainage well hole, a fine gravel filter material layer is arranged in the gap between the well pipe and the drainage well hole, a water pump is arranged in the well pipe, the output end of the water pump is fixedly connected to a water pump pipe, and the other end of the water pump pipe is arranged in the second drainage ditch, and a well cover is arranged in the drainage well hole.

[0009] As a further technical solution of the present invention, a first steel cage is arranged in the retaining pile, a second steel cage is arranged in the supporting pile, and a third steel cage is arranged in the cap beam.

[0010] A construction foundation pit support method, comprising step 1, site leveling; step 2, enclosure system construction; step 3, water stop system construction; step 4, well point dewatering construction; step 5, layered earth excavation; step 6, pit bottom cushion construction;

[0011] In the above step 1, debris and vegetation in the construction area are removed, and the land is leveled and compacted to ensure that the ground is solid and flat;

[0012] In the above step 2, the side walls of the foundation pit are supported by retaining piles to prevent soil collapse, and bored cast-in-place piles are used for construction to ensure that the verticality, depth and spacing of the retaining piles meet the design requirements;

[0013] In the above step 3, a water-stop curtain is formed around the foundation pit to prevent groundwater from seeping into the foundation pit, and water-stop piles are constructed on the inner side of the retaining piles by high-pressure jet grouting to form an effective water-stop curtain;

[0014] In the above step 4, a well point dewatering system is set up in the foundation pit, and groundwater is pumped out by pumping equipment;

[0015] In the above step 5, the soil in the foundation pit is gradually excavated until the designed depth is reached. After each layer of excavation, the retaining structure is promptly supported to ensure the stability of the side wall of the foundation pit;

[0016] In the above step six, a cushion layer is laid at the bottom of the foundation pit, and the foundation pile is deepened.

[0017] As a further technical solution of the present invention, in step four, a drilling machine is used to drill a drainage well hole in the foundation pit, the well pipe is lowered, a fine gravel filter layer is backfilled in the gap between the well pipe and the drainage well hole, and a water pump is set at the bottom of the drainage well hole to pump out the groundwater through the pumping pipe and discharge it through the second drainage ditch.

[0018] As a further technical solution of the present invention, in the step five, the first layer of earth excavation is carried out, a lane is reserved, the third steel cage is installed on the supporting piles and concrete is poured to carry out crown beam construction, and steel mesh is tied to the pit wall and the supporting piles, reinforcement is planted on the piles, reinforcement is welded, and C20 fine stone concrete is sprayed to obtain the first layer of concrete retaining wall. After seven days of curing, the next layer of earth excavation is carried out, the second layer of earth excavation is carried out, the first waist beam and anchor cable are constructed, the drilling rig drills holes on the pit wall, the anchor rods are lowered and the holes are grouting, the anchor cables are tensioned and locked after the waist beam construction, and then the second layer of concrete retaining wall is laid, and the main support structure is completed in sequence.

[0019] As a further technical solution of the present invention, in the step five, continue to excavate and set the slope protection concrete layer, first carry out slope trimming, rivet on the slope surface and hang the first steel mesh, reserve the first drainage hole and then spray concrete, after the slope protection concrete layer reaches 70% of the design strength, carry out the next layer of excavation and set the soil nail wall concrete layer, after excavation, the slope is trimmed, holes are drilled on the slope surface to install fixed steel bars and hang the second steel mesh, reserve the second drainage hole and spray concrete, and after the soil nail wall concrete layer is cured to 70% of the design strength, the bottom of the pit is constructed.

[0020] As a further technical solution of the present invention, in step six, excavation is carried out in the foundation pit to deepen the pedestal, holes are drilled at the bottom of the pit to install foundation beams, a concrete layer is poured on the surface of the bottom of the pit, and a reinforced brick membrane is built on the edge of the foundation pit, a sand and gravel cushion layer is laid on the surface of the foundation pit, and a reinforced and thickened concrete cushion layer is poured on the sand and gravel cushion layer.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention is designed with a multi-layer composite cushion structure at the bottom of the pit. A sand and gravel cushion of suitable thickness is laid at the bottom of the pit to quickly remove excess moisture and enhance the bearing capacity of the foundation. Subsequently, a reinforced and thickened concrete cushion is added on the sand and gravel cushion. A steel mesh or fiber-reinforced material is used to increase the overall strength and rigidity of the cushion, effectively dispersing the upper load and preventing further squeezing and deformation of the soil at the bottom of the pit. A deepened pedestal is set, and a reinforced brick membrane is built at the edge of the foundation pit to effectively prevent soil erosion and collapse at the edge of the foundation pit, and a flat and stable working surface is provided for subsequent concrete pouring. A complete foundation pit support system is formed by closely combining the four parts of the support system, the support system, the water-stopping system and the drainage system, thereby ensuring safety during the foundation pit excavation process. At the same time, it has the advantage of strong applicability and can be flexibly adjusted and optimized according to different geological conditions, groundwater levels and construction requirements, thereby meeting the needs of various foundation pit projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0024] Figure 2 for Figure 1 Schematic diagram of the enlarged structure of the A area in the middle;

[0025] Figure 3 It is a schematic diagram of the top view structure of the present invention;

[0026] Figure 4 It is a side view structural schematic diagram of the present invention;

[0027] Figure 5 It is a side view cutaway structural schematic diagram of the present invention;

[0028] Figure 6 for Figure 5 Schematic diagram of the enlarged structure of the middle B area;

[0029] Figure 7 for Figure 5 Schematic diagram of the enlarged structure of the middle C area;

[0030] Figure 8 The figure is a flow chart of the method of the present invention.

[0031] In the figure: 1. foundation; 2. retaining piles; 3. water-stop piles; 4. supporting piles; 5. crown beam; 6. waist beam; 7. anchor cable; 8. concrete retaining wall; 9. first steel mesh; 10. slope protection concrete layer; 11. first drainage hole; 12. first drainage ditch; 13. fixed steel bars; 14. second steel mesh; 15. soil nail wall concrete layer; 16. second drainage hole; 17. second drainage ditch; 18. sand and gravel cushion layer; 19. reinforced and thickened concrete cushion layer; 20. precipitation well hole; 21. fine gravel filter layer; 22. water pump; 23. water pump; 24. manhole cover; 25. deepened pedestal; 26. foundation beam; 27. reinforced brick membrane; 28. first steel cage; 29. ​​second steel cage; 30. third steel cage; 31. well pipe. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Please see attached Figure 1 -Attached Figure 7An embodiment of the present invention is as follows: a construction foundation pit support structure comprises a foundation 1, wherein the foundation 1 is provided with retaining piles 2, water stop piles 3 and supporting piles 4, the supporting piles 4 are fixedly connected with a crown beam 5 and a waist beam 6, a concrete retaining wall 8 is fixedly connected with an outer wall on one side of the foundation 1, and the concrete retaining wall 8 is fixedly connected with the supporting piles 4 and the waist beam 6, an anchor cable 7 is fixedly connected with the waist beam 6, and the anchor cable 7 is arranged in the foundation 1, a deepening cap 25 is opened on the foundation 1, a foundation beam 26 is arranged in the deepening cap 25, a reinforced brick membrane 27 is fixedly connected with the inner wall of the deepening cap 25, and a sand and gravel cushion layer is arranged on the surface of the foundation 1 18, a reinforced thickened concrete cushion layer 19 is arranged on the gravel cushion layer 18; a first steel mesh 9 is fixedly connected to the outer wall of one side of the foundation 1, a slope protection concrete layer 10 is fixedly connected to the first steel mesh 9, a first drainage hole 11 is opened on the slope protection concrete layer 10, a fixed steel bar 13 is fixedly connected to the outer wall of one side of the foundation 1, a second steel mesh 14 is arranged on the fixed steel bar 13, a soil nail wall concrete layer 15 is fixedly connected to the second steel mesh 14, and a second drainage hole 16 is opened on the soil nail wall concrete layer 15. The slope protection concrete layer 10 is used to increase the stability of the foundation pit slope, prevent the slope from collapsing, reduce the scouring and erosion of the slope by rainwater, and reduce The risk of soil erosion is reduced, thereby protecting the environment around the foundation pit. The soil nail wall concrete layer 15 is tightly combined with the soil through grouting to form an integral force-bearing structure, which can effectively improve the stability and bearing capacity of the soil, improve the structural strength and deformation resistance of the slope soil, and reduce the lateral deformation of the soil; the first drainage ditch 12 and the second drainage ditch 17 are respectively opened at the positions corresponding to the slope protection concrete layer 10 and the soil nail wall concrete layer 15 on the foundation 1, and the first drainage ditch 12 and the second drainage ditch 17 are used for drainage; a drainage well 20 is opened on the foundation 1, and a well pipe 31 is sleeved in the drainage well 20, and the well pipe 31 and the drainage well 20 are spaced apart. A fine gravel filter layer 21 is arranged in the gap, a water pump 22 is arranged in the well pipe 31, the output end of the water pump 22 is fixedly connected to a water pump 23, and the other end of the water pump 23 is arranged in the second drainage ditch 17, a well cover 24 is arranged in the precipitation well hole 20, the water pump 22 and the water pump 23 are used for pumping groundwater, and the fine gravel filter layer 21 is used for filtering groundwater; a first steel cage 28 is arranged in the retaining pile 2, a second steel cage 29 is arranged in the supporting pile 4, and a third steel cage 30 is arranged in the crown beam 5. The first steel cage 28, the second steel cage 29 and the third steel cage 30 are used to reinforce the structural strength of the concrete member.

[0034] Please see attached Figure 8 The present invention provides an embodiment: a construction foundation pit support method, comprising step one, site leveling; step two, enclosure system construction; step three, water stop system construction; step four, well point dewatering construction; step five, layered earth excavation; step six, pit bottom cushion construction;

[0035] In the above step 1, debris and vegetation in the construction area are removed, and the land is leveled and compacted to ensure that the ground is solid and flat;

[0036] In the above step 2, the side walls of the foundation pit are supported by retaining piles 2 to prevent soil collapse, and bored cast-in-place piles are used for construction to ensure that the verticality, depth and spacing of the retaining piles 2 meet the design requirements;

[0037] In the above step 3, a water-stop curtain is formed around the foundation pit to prevent groundwater from seeping into the foundation pit, and a water-stop pile 3 is constructed inside the retaining pile 2 by adopting a high-pressure jet grouting method to form an effective water-stop curtain;

[0038] In the above step 4, a well point dewatering system is set up in the foundation pit, a dewatering well hole 20 is drilled in the foundation pit using a drilling machine, a well pipe 31 is suspended, a fine gravel filter material layer 21 is backfilled in the gap between the well pipe 31 and the dewatering well hole 20, and a pumping pump 22 is set at the bottom of the dewatering well hole 20 to pump out the groundwater through the pumping pipe 23 and discharge it through the second drainage ditch 17;

[0039] In the above step five, the soil in the foundation pit is gradually excavated until the designed depth is reached. After each layer of excavation, the retaining structure is supported in time to ensure the stability of the side wall of the foundation pit. The first layer of earthwork is excavated, a lane is reserved, the third steel cage 30 is installed on the supporting pile 4, and concrete is poured to construct the crown beam 5, and the steel mesh is tied to the pit wall and the supporting pile 4, the pile is planted with steel bars, the reinforcement is welded, and C20 fine stone concrete is sprayed to obtain the first layer of concrete retaining wall 8. After seven days of curing, the next layer of earthwork is excavated, the second layer of earthwork is excavated, the first waist beam 6 and the anchor cable 7 are constructed, the drilling rig drills holes on the pit wall, the anchor rods are lowered, and then grouting is performed in the holes. , after the construction of the waist beam 6, the anchor cable 7 is tensioned and locked, and then the second layer of concrete retaining wall 8 is laid, and the main supporting structure is completed in sequence, and the excavation is continued and the slope protection concrete layer 10 is set. First, the slope is trimmed, and the first steel mesh 9 is hung on the slope surface with rivets, and the first drainage hole 11 is reserved and then concrete is sprayed. After the slope protection concrete layer 10 is cured to reach 70% of the design strength, the next layer is excavated and the soil nail wall concrete layer 15 is set. After excavation, the slope is trimmed, and holes are drilled on the slope surface to install fixed steel bars 13 and hang the second steel mesh 14. The second drainage hole 16 is reserved and concrete is sprayed. After the soil nail wall concrete layer 15 is cured to 70% of the design strength, the bottom of the pit is constructed;

[0040] In the above step six, a cushion layer is laid at the bottom of the foundation pit, and a deepening cap 25 is constructed. The foundation pit is excavated to deepen the cap 25, holes are drilled at the bottom of the pit to install a foundation beam 26, a concrete layer is poured on the surface of the bottom of the pit, and a reinforced brick membrane 27 is built on the edge of the foundation pit. A sand and gravel cushion layer 18 is laid on the surface of the foundation pit, and a reinforced and thickened concrete cushion layer 19 is poured on the sand and gravel cushion layer 18.

[0041] Based on the above, the advantages of the present invention are: when the present invention is used for foundation pit support, firstly, debris, vegetation, etc. on the foundation 1 in the construction area are cleared, and the land is leveled and compacted to ensure that the ground is solid and flat; the side walls of the foundation pit are supported by the retaining piles 2 to prevent soil collapse, and the bored pile method is used for construction, a first steel cage 28 is set in the hole, and concrete is poured to ensure that the verticality, depth and spacing of the retaining piles 2 meet the design requirements, and a second steel cage 29 is drilled and set, and concrete is poured to obtain the supporting piles 4; a water-stop curtain is formed around the foundation pit to prevent groundwater from seeping into the foundation pit, and a water-stop pile 3 is constructed on the inner side of the retaining pile 2, and a high-pressure rotary jet pile method is used for construction to form An effective water-stop curtain; a well point dewatering system is set up in the foundation pit, a drilling machine is used to drill a dewatering well hole 20 in the foundation pit, a well pipe 31 is suspended, a fine gravel filter layer 21 is backfilled in the gap between the well pipe 31 and the dewatering well hole 20, and a pump 22 is set at the bottom of the dewatering well hole 20, groundwater is pumped out through a pumping pipe 23, and discharged through the second drainage ditch 17; the soil in the foundation pit is gradually excavated until the designed depth is reached, and after each layer of excavation, the retaining structure is supported in time to ensure the stability of the side wall of the foundation pit, the first layer of earthwork is excavated, a lane is reserved, the third steel cage 30 is installed on the supporting pile 4, and concrete is poured to construct the crown beam 5, and steel mesh is tied on the pit wall and the supporting pile 4, and the pile The upper reinforcement is planted and welded, and C20 fine stone concrete is sprayed to obtain the first layer of concrete retaining wall 8. After seven days of curing, the next layer of earthwork is excavated, the second layer of earthwork is excavated, the first waist beam 6 and anchor cable 7 are constructed, the drilling rig drills holes on the pit wall, the anchor rods are lowered and the holes are grouting, after the waist beam 6 is constructed, the anchor cable 7 is tensioned and locked, and then the second layer of concrete retaining wall 8 is laid, and the main supporting structures are completed in sequence, and excavation is continued and the slope protection concrete layer 10 is set. First, the slope is trimmed, and the first steel mesh 9 is hung on the slope surface with rivets, and concrete is sprayed after reserving the first drainage hole 11. After the slope protection concrete layer 10 reaches 70% of the design strength, the next layer of excavation is carried out and the soil nail wall concrete layer 15 is set. After excavation, the slope is trimmed , drill holes on the slope to install fixed steel bars 13 and hang a second steel mesh 14, reserve a second drainage hole 16 for spraying concrete, and carry out pit bottom construction after the soil nail wall concrete layer 15 is cured to 70% of the design strength; lay a cushion layer at the bottom of the foundation pit, and deepen the cap 25, excavate the foundation pit to deepen the cap 25, drill holes at the bottom of the pit to install foundation beams 26, pour a concrete layer on the surface of the pit bottom, and build a reinforced brick membrane 27 at the edge of the foundation pit, lay a sand and gravel cushion layer 18 on the surface of the foundation pit, and pour a reinforced and thickened concrete cushion layer 19 on the sand and gravel cushion layer 18; the first drainage ditch 12 is used to collect and discharge the water discharged from the first drainage hole 11, and the manhole cover 24 is used to close the precipitation well hole 20 to prevent blockage.

Claims

1. A foundation pit support structure for construction, comprising a foundation (1), characterized in that: The foundation (1) is provided with retaining piles (2), water-stopping piles (3) and supporting piles (4); the supporting piles (4) are fixedly connected with a crown beam (5) and a waist beam (6); a concrete retaining wall (8) is fixedly connected to an outer wall of one side of the foundation (1); the concrete retaining wall (8) is fixedly connected to the supporting piles (4) and the waist beam (6); an anchor cable (7) is fixedly connected to the waist beam (6); and the anchor cable (7) is arranged in the foundation (1); a deepened pedestal (25) is provided on the foundation (1); a foundation beam (26) is arranged in the deepened pedestal (25); a reinforced brick membrane (27) is fixedly connected to the inner wall of the deepened pedestal (25); a gravel cushion layer (18) is provided on the surface of the foundation (1); and a reinforced thickened concrete cushion layer (19) is provided on the gravel cushion layer (18).

2. A construction foundation pit support structure according to claim 1, characterized in that: A first steel mesh (9) is fixedly connected to an outer wall on one side of the foundation (1), a slope protection concrete layer (10) is fixedly connected to the first steel mesh (9), a first drainage hole (11) is provided on the slope protection concrete layer (10), a fixed steel bar (13) is fixedly connected to an outer wall on one side of the foundation (1), a second steel mesh (14) is arranged on the fixed steel bar (13), a soil nail wall concrete layer (15) is fixedly connected to the second steel mesh (14), and a second drainage hole (16) is provided on the soil nail wall concrete layer (15).

3. A construction foundation pit support structure according to claim 2, characterized in that: A first drainage ditch (12) and a second drainage ditch (17) are respectively provided on the foundation (1) at positions corresponding to the slope protection concrete layer (10) and the soil nail wall concrete layer (15).

4. A construction foundation pit support structure according to claim 1, characterized in that: A drainage well hole (20) is provided on the foundation (1), a well pipe (31) is sleeved in the drainage well hole (20), a fine gravel filter material layer (21) is provided in the gap between the well pipe (31) and the drainage well hole (20), a water pump (22) is provided in the well pipe (31), an output end of the water pump (22) is fixedly connected to a water pump pipe (23), and the other end of the water pump pipe (23) is provided in a second drainage ditch (17), and a well cover (24) is provided in the drainage well hole (20).

5. A construction foundation pit support structure according to claim 1, characterized in that: A first steel cage (28) is arranged in the enclosure pile (2), a second steel cage (29) is arranged in the support pile (4), and a third steel cage (30) is arranged in the cap beam (5).

6. A method for supporting a foundation pit for construction, comprising step 1, site leveling; step 2, construction of a retaining system; step 3, construction of a water stop system; step 4, construction of well point dewatering; step 5, layered earth excavation; step 6, construction of a pit bottom cushion layer; characterized in that: In the above step 1, debris and vegetation in the construction area are removed, and the land is leveled and compacted to ensure that the ground is solid and flat; In the above step 2, the side walls of the foundation pit are supported by retaining piles (2) to prevent soil collapse, and bored cast-in-place piles are used for construction to ensure that the verticality, depth and spacing of the retaining piles (2) meet the design requirements; In the above step 3, a water-stop curtain is formed around the foundation pit to prevent groundwater from seeping into the foundation pit, and water-stop piles (3) are constructed inside the retaining piles (2) by using a high-pressure jet grouting method to form an effective water-stop curtain; In the above step 4, a well point dewatering system is set up in the foundation pit, and groundwater is pumped out by pumping equipment; In the above step 5, the soil in the foundation pit is gradually excavated until the designed depth is reached. After each layer of excavation, the retaining structure is promptly supported to ensure the stability of the side wall of the foundation pit; In the above step 6, a cushion layer is laid at the bottom of the foundation pit, and the construction of deepening the foundation cap (25) is carried out.

7. A construction foundation pit support method according to claim 6, characterized in that: In the step 4, a drainage well hole (20) is drilled in the foundation pit using a drilling machine, a well pipe (31) is lowered, a fine gravel filter material layer (21) is backfilled in the gap between the well pipe (31) and the drainage well hole (20), and a pump (22) is arranged at the bottom of the drainage well hole (20), and groundwater is pumped out through a pumping pipe (23) and discharged through a second drainage ditch (17).

8. A construction foundation pit support method according to claim 6, characterized in that: In the step 5, the first layer of earthwork is excavated, a lane is reserved, a third steel cage (30) is installed on the supporting pile (4), and concrete is poured to construct the crown beam (5), and steel mesh is tied to the pit wall and the supporting pile (4), reinforcement is planted on the pile, reinforcement is welded, and C20 fine stone concrete is sprayed to obtain the first layer of concrete retaining wall (8). After seven days of curing, the next layer of earthwork is excavated, the second layer of earthwork is excavated, the first waist beam (6) and anchor cable (7) are constructed, a drilling rig drills holes on the pit wall, anchor rods are lowered and grouting is performed in the holes, after the waist beam (6) is constructed, the anchor cable (7) is tensioned and locked, and then the second layer of concrete retaining wall (8) is laid, and the main supporting structure is completed in sequence.

9. A construction foundation pit support method according to claim 8, characterized in that: In the step 5, excavation is continued and a slope protection concrete layer (10) is set. First, the slope is trimmed, rivets are punched on the slope surface and a first steel mesh (9) is hung. After a first drainage hole (11) is reserved, concrete is sprayed. After the slope protection concrete layer (10) is cured to reach 70% of the design strength, the next layer is excavated and a soil nail wall concrete layer (15) is set. After excavation, the slope is trimmed, holes are punched on the slope surface to install fixed steel bars (13) and a second steel mesh (14) is hung. After a second drainage hole (16) is reserved, concrete is sprayed. After the soil nail wall concrete layer (15) is cured to reach 70% of the design strength, pit bottom construction is carried out.

10. A construction foundation pit support method according to claim 6, characterized in that: In the step six, the foundation pit is excavated to deepen the cap (25), holes are drilled at the bottom of the pit to install the foundation beam (26), a concrete layer is poured on the surface of the bottom of the pit, and a reinforced brick membrane (27) is built on the edge of the foundation pit, a sand and gravel cushion layer (18) is laid on the surface of the foundation pit, and a reinforced and thickened concrete cushion layer (19) is poured on the sand and gravel cushion layer (18).

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