A construction method for deep foundation pit support structures with groundwater.

Abstract

This invention discloses a construction method for a deep foundation pit support structure with groundwater. The structure includes a diaphragm wall installed inside the foundation pit, a concrete bottom slab installed at the bottom of the pit, and compartment walls. Shear grooves are provided in both the diaphragm wall and the compartment walls, and the ends of the concrete bottom slab are connected to the shear grooves. Multiple transverse support beams are installed on the diaphragm wall. Rectangular pre-installed components are embedded within the shear grooves. Each rectangular pre-installed component includes a waterproof layer and compressed soil bricks installed inside the waterproof layer. When the waterproof layer is damaged, the compressed soil bricks expand and diffuse outwards upon contact with water. The method includes constructing the diaphragm wall, constructing the transverse support beams, underwater construction, underwater concrete bottom sealing, structural construction, and backfilling. This structure has good stability and safety, reduces the need for underwater operations, lowers construction costs, enhances the safety of the construction process, shortens the construction cycle, and saves manpower and resources.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and specifically to a construction method for a deep foundation pit support structure with groundwater. Background Technology

[0002] During the construction of foundation pits, underwater construction is often necessary when the pit is deep or the groundwater level is shallow. Underwater construction presents significant challenges due to the greater depth and pressure of the groundwater, increasing the difficulty of constructing and cleaning the shear trench. The thoroughness of the shear trench cleaning greatly affects the subsequent sealing of the bottom slab during pouring. Currently, shear trenches are typically prefabricated on precast reinforcing cages, and grout-stopping sheets are fixed inside the trenches to prevent concrete from entering during pouring. However, after this construction is completed, experienced divers are still required to clean the shear trenches, remove the grout-stopping sheets, and take underwater photographs during the excavation process. This work is highly demanding, dangerous, inefficient, and costly. Summary of the Invention

[0003] The purpose of this invention is to provide a construction method for a deep foundation pit support structure with groundwater. This structure has good stability and safety, reduces the need for underwater operations, lowers construction costs, and enhances the safety of the construction process. This method shortens the construction cycle and saves manpower and resources, and is worthy of promotion.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A construction method for a deep foundation pit support structure with groundwater is disclosed. The support structure includes a diaphragm wall installed inside the foundation pit, a concrete bottom slab installed at the bottom of the foundation pit, and compartment walls. Shear grooves are provided in both the diaphragm wall and the compartment walls. The end of the concrete bottom slab is connected to the shear groove. Multiple transverse support beams are installed on the diaphragm wall above the design water level. A guide wall is installed on the outer side of the top of the diaphragm wall, and a drainage ditch is installed on one side of the guide wall. A rectangular pre-installed component is pre-installed in the shear groove. The rectangular pre-installed component includes a waterproof layer and compressed soil bricks installed inside the waterproof layer. When the waterproof layer is damaged, the compressed soil bricks expand and diffuse outwards from the waterproof layer when exposed to water.

[0006] The construction method includes the following steps:

[0007] Step 1: Construct the diaphragm wall. First, build a fence around the foundation pit to be constructed, level the site, and then construct the diaphragm wall, guide wall, and capping beam on top of the wall; at the same time, construct the compartment walls, and backfill the upper part after the compartment walls are formed.

[0008] Step 2: Construct the transverse support beams. When the foundation pit is excavated to the preset height below the bottom elevation of each transverse support beam, stop the excavation of the foundation pit and erect each transverse support beam in sequence. Continue construction downwards after the transverse support beams are completed.

[0009] Step 3: Underwater construction. When the foundation pit is excavated down to the groundwater level, underwater excavation is used to construct the foundation pit to the bottom. The waterproof layer is damaged, causing the compressed soil bricks to spread outward. Then, a high-pressure water gun is used to clean the remaining compressed soil bricks in the waterproof layer. The shear groove is cleaned, and the cleaning effect of the inner wall of the shear groove is photographed. After cleaning, the data is transmitted back through an underwater camera for the operators to judge whether the cleaning is clean.

[0010] Step 4: Underwater concrete sealing. After the underwater excavation is completed, the flatness of the bottom of the pit is tested. If the flatness is qualified, the concrete sealing slab is poured underwater. After the concrete sealing slab at the bottom of the entire pit reaches the design strength, the pit is pumped out and the silt and scum at the bottom of the pit are cleaned. Then, a layer of crushed stone is laid on the concrete sealing slab.

[0011] Step 5: Construction of the building structure. A foundation layer and a waterproof layer are constructed on the crushed stone layer. Then, the compartment walls are demolished section by section. The reinforced concrete construction of the bottom slab, middle slab, and side walls of the building structure is carried out. Multiple transverse support beams are demolished from bottom to top until the construction of the building structure is completed.

[0012] Step 6: Backfilling construction, remove the guide wall below ground level, and backfill the top slab with soil in layers.

[0013] Preferably, the bottom of both the underground continuous wall and the compartment wall is lower than the bottom surface of the concrete sealing slab.

[0014] Preferably, the thickness of the concrete base plate is 4.5 to 5.5 m.

[0015] Preferably, the preset height value in step two is 0.5m.

[0016] Preferably, in step two, if the groundwater level rises above the lowest transverse support beam, dewatering measures should be taken in the pit to ensure that all transverse support beams can be constructed without water.

[0017] Preferably, during the dewatering operation in step four, the monitoring of the diaphragm wall should be strengthened. When the deformation or internal stress of the diaphragm wall reaches the designed dangerous value, the dewatering operation should be stopped and water should be recharged into the foundation pit.

[0018] Preferably, in step three, a mobile device is used for underwater cleaning and video recording. The mobile device includes a mounting bracket, a cross slide assembly mounted on the mounting bracket, a vertical telescopic assembly mounted on the cross slide assembly, a mounting base mounted on the vertical telescopic assembly, and a high-pressure water gun and camera mounted on the mounting base. The cross slide assembly and the vertical telescopic assembly are used to control the movement of the mounting base in three orthogonal directions to perform cleaning and video recording.

[0019] Preferably, the vertical telescopic assembly includes a support sleeve, an inner rod slidably mounted on the support sleeve, and an electric push rod for driving the inner rod to slide. One end of the electric push rod is fixedly mounted on the support sleeve, and the other end of the electric push rod is fixedly mounted on the inner rod.

[0020] Preferably, the inner rod is provided with a plurality of connecting holes, and the electric push rod is fixedly connected to the connecting holes through the pin.

[0021] In this invention, the partition walls divide the foundation pit into several independent areas, facilitating individual construction of each area. The shear grooves improve the stability of the connection between the concrete bottom slab, the diaphragm wall, and the partition walls, enhancing buoyancy resistance. The compressed soil blocks in the rectangular prefabricated components expand and diffuse upon contact with water, simplifying the cleaning of the shear grooves and improving construction efficiency. The mobile equipment replaces manual labor for underwater operations, enhancing safety, reducing costs, improving efficiency, and ensuring operational stability, thus avoiding quality issues caused by low worker skill levels. This construction method employs a sequence of first constructing the diaphragm wall and partition walls, then gradually excavating downwards, and finally constructing layer by layer from the bottom up, maximizing construction safety, preventing collapse, and shortening the construction period. Attached Figure Description

[0022] Figure 1 This is a construction diagram of step one of the present invention;

[0023] Figure 2 This is a top view of the foundation pit partitioning of the present invention;

[0024] Figure 3 This is a schematic diagram of step two of the present invention.

[0025] Figure 4 This is a schematic diagram of step three of the present invention.

[0026] Figure 5 This is a schematic diagram of step four of the present invention.

[0027] Figure 6 This is a schematic diagram of step five of the present invention.

[0028] Figure 7This is a schematic diagram of step six of the present invention.

[0029] Figure 8 This is a schematic diagram of the structure of the mobile device of the present invention;

[0030] Figure 9 This is a schematic cross-sectional view of the rectangular pre-formed part of the present invention;

[0031] In the diagram: 1. Excavation pit; 2. Diaphragm wall; 3. Concrete bottom slab; 4. Compartment wall; 5. Shear groove; 6. Horizontal support beam; 7. Guide wall; 8. Drainage ditch; 9. Rectangular pre-installed component; 10. Mobile device; 11. Mounting bracket; 12. Cross slide assembly; 13. Vertical telescopic assembly; 14. Mounting base; 15. High-pressure water gun; 16. Camera; 17. Building structure; 90. Waterproof layer; 91. Compressed adobe brick; 130. Support sleeve; 131. Inner rod; 132. Electric push rod. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings:

[0033] like Figures 1-9 The method for constructing a deep foundation pit support structure with groundwater includes a diaphragm wall 2 installed inside the foundation pit 1, specifically, the foundation pit 1 is cuboid in shape. It also includes a concrete bottom slab 3 and compartment walls 4 installed at the bottom of the foundation pit 1. Shear grooves 5 are integrally formed in both the diaphragm wall 2 and the compartment walls 4. The ends of the concrete bottom slab 3 are connected to the shear grooves 5. In one embodiment, two shear grooves 5 are vertically arranged, and the shear grooves 5 are filled simultaneously during the pouring of the concrete bottom slab 3 to improve buoyancy resistance. The thickness of the concrete bottom slab 3 is 4.5–5.5 m, specifically 4.5 m; a larger volume also provides better buoyancy resistance. The bottoms of both the diaphragm wall 2 and the compartment walls 4 are lower than the bottom surface of the concrete bottom slab 3.

[0034] Multiple transverse support beams 6 are installed on the diaphragm wall 2 above the design water level. A guide wall 7 is installed on the outer side of the top of the diaphragm wall 2, and a drainage ditch 8 is installed on one side of the guide wall 7. In this embodiment, four transverse support beams 6 are installed. A rectangular pre-installed component 9 is pre-installed in the shear groove 5. The rectangular pre-installed component 9 includes a waterproof layer 90 and compressed soil bricks 91 installed inside the waterproof layer 90. When the waterproof layer 90 is damaged, the compressed soil bricks 91 expand and diffuse outward when exposed to water. In one embodiment, the waterproof layer 90 can be a plastic film, and the compressed soil bricks 91 are highly absorbent compressed soil blocks used in flower cultivation. The compressed soil bricks 91 have a certain strength in the compressed state, which can meet the pouring strength of the diaphragm wall 2 and the compartment wall 4. When the waterproof layer 90 is damaged by human intervention, the compressed soil bricks 91 will expand and diffuse outward quickly when exposed to water, achieving automatic cleaning. The remaining part can be cleaned later by a high-pressure water gun, and the plastic film can also be easily washed and broken by the high-pressure water gun, making cleaning simple and convenient.

[0035] The method includes the following steps: Step 1, constructing the diaphragm wall 2. First, erect a fence around the foundation pit 1 to protect the construction site, and then level the site to ensure a relatively safe construction environment. Next, use mechanical equipment to construct the diaphragm wall 2, guide wall 7, and the capping beam at the top of the wall, all of which are reinforced concrete structures. Simultaneously, construct the compartment wall 4 within the foundation pit 1. After the compartment wall 4 is formed, backfill the slotted portion between its upper part and the ground surface. During construction, the bottom elevation of the compartment wall 4 is level with the bottom elevation of the diaphragm wall 2 and lower than the bottom of the foundation pit 1. In one embodiment, the compartment wall 4 divides the foundation pit 1 into 16, 24, or other numbers of sections, each section having a horizontal length of approximately 15 meters and a front-to-back width of approximately 20 meters. During construction, follow the attached... Figure 2 Construction will proceed sequentially in the direction indicated in the middle, specifically in areas I and II, which will be constructed simultaneously.

[0036] Step two: Construct the transverse support beams 6. When the excavation of the foundation pit 1 reaches a preset height below the bottom elevation of each transverse support beam 6 (in this embodiment, the preset height is 0.5m), the excavation stops, and each transverse support beam 6 is erected sequentially. The transverse support beams 6 are reinforced concrete structures. Construction continues downwards after the transverse support beams 6 are completed, until all four transverse support beams 6 are completed. In one embodiment, if the groundwater level rises above the lowest transverse support beam 6, dewatering measures should be taken to ensure that all transverse support beams 6 can be constructed without water. Specific dewatering measures can include continuous pumping.

[0037] Step 3: Underwater construction. When excavating the foundation pit 1 down to the groundwater level, underwater excavation is used to reach the bottom of the pit. Specifically, four rotary drilling rigs, two gravity grab buckets, and one jet reverse circulation drilling rig are used simultaneously for underwater earthwork excavation. The jet reverse circulation equipment is used to repeatedly clean the corners and blind areas, clean the shear groove 5, and film the cleaning effect on the inner wall of the shear groove 5. When the foundation pit 1 is excavated to the position of the shear groove 5, the waterproof layer 90 can be broken by the jet reverse circulation equipment to cause the compressed soil bricks 91 to spread outward. Then, a high-pressure water gun is used to clean the remaining compressed soil bricks 91 in the waterproof layer 90. After cleaning, the data is transmitted back by an underwater camera for the operators to judge whether the cleaning is complete. Specifically, the jet reverse circulation equipment can be mounted on the mobile device 10.

[0038] In one embodiment, a movable device 10 can be used for underwater cleaning and video recording. The movable device includes a mounting bracket 11, a cross slide assembly 12 mounted on the mounting bracket 11, a vertical telescopic assembly 13 mounted on the cross slide assembly 12, a mounting base 14 mounted on the vertical telescopic assembly 13, and a high-pressure water gun 15 and a camera 16 mounted on the mounting base 14. The cross slide assembly 12 and the vertical telescopic assembly 13 are used to control the movement of the mounting base 14 in three orthogonal directions for cleaning and video recording. Specifically, the vertical telescopic assembly 13 includes a support sleeve 130, an inner rod 131 slidably mounted on the support sleeve 130, and an electric push rod 132 that drives the inner rod 131 to slide. One end of the electric push rod 132 is fixedly mounted on the support sleeve 130, and the other end of the electric push rod 132 is fixedly mounted on the inner rod 131. Several connecting holes are provided on the inner rod 131, and one end of the electric push rod 132 is fixedly connected to the connecting holes through a pin. The operator on the ground controls the extension and retraction of the electric push rod 132 to vertically raise and lower the high-pressure water gun 15 and the camera 16.

[0039] Step four: Underwater concrete sealing. After underwater excavation is completed, the flatness of the bottom of the foundation pit 1 is tested. Once the flatness is qualified, the concrete sealing slab 3 is poured underwater. After the concrete sealing slab 3 at the bottom of the entire foundation pit 1 reaches the design strength, the foundation pit 1 is dewatered, and the silt and scum at the bottom of the pit are cleaned. Then, a layer of crushed stone is laid on the concrete sealing slab 3. In one embodiment, during the dewatering operation, the monitoring of the underground continuous wall 2 is strengthened. When the deformation or internal stress of the underground continuous wall 2 reaches the design danger value, the dewatering operation should be stopped and water should be recharged into the foundation pit 1.

[0040] Step 5: Construction of building structure 17. A cushion layer and a waterproof layer are constructed on the crushed stone layer. Then, the compartment walls 4 are demolished section by section. The bottom slab, middle slab and side wall reinforced concrete construction of building structure 17 is carried out. Multiple transverse support beams 6 are demolished from bottom to top until the construction of building structure 17 is completed.

[0041] Step six: Backfilling construction. Use mechanical equipment to remove the guide wall 7 below ground level and backfill the top slab with soil in layers. The backfilled soil should meet the planting requirements. This completes the construction of areas I and II. Then repeat steps one to six to simultaneously construct areas III and IV to the right, and continue construction in sequence until the construction of the areas is completed.

[0042] The above embodiments are merely illustrative of the concept and implementation of the present invention and are not intended to limit it. Under the concept of the present invention, technical solutions without substantial changes are still within the scope of protection.

Claims

1. A construction method for a deep foundation pit support structure with groundwater, characterized in that: The support structure includes a diaphragm wall installed inside the foundation pit, a concrete bottom slab installed at the bottom of the foundation pit, and compartment walls. Shear grooves are provided in both the diaphragm wall and the compartment walls. The end of the concrete bottom slab is connected to the shear groove. Multiple transverse support beams are installed on the diaphragm wall above the design water level. A guide wall is installed on the outer side of the top of the diaphragm wall, and a drainage ditch is installed on one side of the guide wall. Rectangular pre-installed components are pre-installed in the shear groove. The rectangular pre-installed components include a waterproof layer and compressed soil bricks installed inside the waterproof layer. When the waterproof layer is damaged, the compressed soil bricks expand and diffuse outwards when exposed to water. The construction method includes the following steps: Step 1: Construct the diaphragm wall. First, build a fence around the foundation pit to be constructed, level the site, and then construct the diaphragm wall, guide wall, and capping beam on top of the wall; at the same time, construct the compartment walls, and backfill the upper part after the compartment walls are formed. Step 2: Construct the transverse support beams. When the foundation pit is excavated to the preset height below the bottom elevation of each transverse support beam, stop the excavation of the foundation pit and erect each transverse support beam in sequence. Continue construction downwards after the transverse support beams are completed. Step 3: Underwater construction. When the foundation pit is excavated down to the groundwater level, underwater excavation is used to reach the bottom of the pit. The waterproof layer is damaged, causing the compressed soil bricks to spread outwards. A high-pressure water gun is then used to clean the remaining compressed soil bricks inside the waterproof layer. The shear groove is cleaned, and the cleaning effect on the inner wall of the shear groove is filmed. After cleaning, the data is transmitted back through an underwater camera for the operator to judge whether the cleaning is complete. A mobile device is used for underwater cleaning and filming operations. The mobile device includes a mounting bracket, a cross slide assembly mounted on the mounting bracket, a vertical telescopic assembly mounted on the cross slide assembly, a mounting base mounted on the vertical telescopic assembly, and a high-pressure water gun and camera mounted on the mounting base. The cross slide assembly and the vertical telescopic assembly are used to control the movement of the mounting base in three orthogonal directions for cleaning and filming operations. Step 4: Underwater concrete sealing. After the underwater excavation is completed, the flatness of the bottom of the pit is tested. If the flatness is qualified, the concrete sealing slab is poured underwater. After the concrete sealing slab at the bottom of the entire pit reaches the design strength, the pit is pumped out and the silt and scum at the bottom of the pit are cleaned. Then, a layer of crushed stone is laid on the concrete sealing slab. Step 5: Construction of the building structure. A foundation layer and a waterproof layer are constructed on the crushed stone layer. Then, the compartment walls are demolished section by section. The reinforced concrete construction of the bottom slab, middle slab, and side walls of the building structure is carried out. Multiple transverse support beams are demolished from bottom to top until the construction of the building structure is completed. Step 6: Backfilling construction, remove the guide wall below ground level, and backfill the top slab with soil in layers.

2. The construction method for deep foundation pit support structure with groundwater according to claim 1, characterized in that: The bottom of both the underground continuous wall and the compartment wall is lower than the bottom surface of the concrete sealing slab.

3. The construction method for a deep foundation pit support structure with groundwater according to claim 1 or 2, characterized in that: The thickness of the concrete bottom slab is 4.5 to 5.5 m.

4. The construction method for a deep foundation pit support structure with groundwater according to claim 1, characterized in that: The preset height value in step two is 0.5m.

5. The construction method for a deep foundation pit support structure with groundwater as described in claim 1 or 4, characterized in that: In step two, if the groundwater level rises above the lowest horizontal support beam, dewatering measures are taken in the pit to ensure that all horizontal support beams are constructed without water.

6. The construction method for a deep foundation pit support structure with groundwater according to claim 1, characterized in that: During the dewatering operation in step four, the monitoring of the underground continuous wall should be strengthened. When the deformation or internal stress of the underground continuous wall reaches the designed dangerous value, the dewatering operation should be stopped and water should be recharged into the foundation pit.

7. The construction method for a deep foundation pit support structure with groundwater according to claim 1, characterized in that: The vertical telescopic assembly includes a support sleeve, an inner rod slidably mounted on the support sleeve, and an electric push rod that drives the inner rod to slide. One end of the electric push rod is fixedly mounted on the support sleeve, and the other end of the electric push rod is fixedly mounted on the inner rod.

8. The construction method for a deep foundation pit support structure with groundwater according to claim 7, characterized in that: The inner rod is provided with several connecting holes, and the electric push rod is fixedly connected to the connecting holes by a pin.

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