Method for accelerating construction of ramp located at foundation pit boundary through lattice type profile steel inclined supporting device

Abstract

The invention discloses a method for accelerating construction of a ramp located at the boundary of a foundation pit through a lattice type profile steel inclined supporting device. The slope construction process includes the steps of basement foundation bottom plate and inclined strut base installation, basement outer wall and top plate construction completion, support dismantling (the rest of structures on the periphery can be constructed), outer wall water prevention and backfilling, slope bottom plate cushion layer and water prevention, slope bottom plate construction and slope wall plate and top plate structure construction. The rest structures on the periphery are constructed in advance, and ramp wallboards and top plate structures are not constructed in two times; the construction process of the foundation pit supporting system covering ramp is rapid and efficient, and a reliable and feasible technical scheme is provided for similar construction.

Description

Technical Field

[0001] This invention belongs to the field of foundation pit support replacement and relates to a method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device. Specifically, it is applied to situations where the construction of the ramp is slow and affects the construction of the surrounding structure in the foundation pit support system covering the ramp. Background Technology

[0002] Currently, in basement structures, ramp construction is typically scheduled after the basement structure is completed, or even after the superstructure is topped out. In the conditions considered in this invention, the ramp structure is located at the boundary of the foundation pit, and the foundation pit support system covers the ramp. The conventional construction process is as follows: basement foundation → completion of basement exterior walls and roof slab → completion of exterior wall waterproofing and backfilling → ramp base slab bedding and waterproofing → completion of ramp base slab → completion of ramp exterior walls and external support strip → completion of temporary internal support within the ramp → removal of reinforced concrete support → subsequent ramp structure and other areas within the support coverage area. Construction of above-ground and underground structures; however, the above approach has the following disadvantages: 1. The construction process is very long, the foundation pit is exposed for a long time, which affects the safety of the foundation pit; 2. The working space is narrow, the operating range of large construction machinery is limited, and the cross-operation of material transportation, formwork installation, and rebar binding is difficult; 3. During the period from the construction of the slope bottom slab to the completion of the curing of the replacement support belt, the support cannot be removed, and other above-ground and underground structures within the support coverage area cannot be constructed, which slows down the overall progress; 4. There is a construction step of replacing the support. In order to ensure the stability of the foundation pit support, the slope construction may need to be coordinated with the foundation pit support (such as soil nailing walls and piles). If the support strength is insufficient or the construction sequence is unreasonable, slope collapse is likely to occur. Simultaneously, the construction of the ramp structure may disturb the support system, increasing safety risks. 5. Due to support limitations, the ramp wall panels cannot be constructed in one go, resulting in poor flatness of the cantilevered wall panels. Subsequent structural work requires waiting for the supports to be removed before construction can continue, adding a horizontal construction joint and increasing the risk of leakage. 6. The ramp base is prone to water accumulation, silt, or weak soil layers, requiring replacement and compaction. There is a risk of uneven settlement with other structures, leading to subsequent structural settlement and cracking. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a method for accelerating the construction of a ramp located at the boundary of a foundation pit by replacing the original reinforced concrete support system with a deep foundation pit lattice steel internal inclined bracing support system when the basement foundation slab is completed but the ramp cannot be constructed yet. This method avoids the reinforced concrete support affecting the construction of other underground and above-ground structures within its coverage area.

[0004] The technical solution of this invention is: a method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device, comprising the following steps: Step (1): Before all construction processes, jet grouting piles, three-axis cement mixing piles and bored piles are driven into the required positions in sequence. After the jet grouting piles, triaxial cement mixing piles and bored piles are driven into place, the slope protection and intercepting ditch on the top of the retaining wall will be constructed, and the concrete support construction will be carried out simultaneously. Step (2): After the concrete support is poured, earthwork excavation begins; then, the cushion layer and the bottom slab are poured on the other side of the bored pile to form the foundation slab. Step (3): Set graded crushed stone backfill between the foundation slab and the bored pile; lay out the positioning line, pour the inclined support pier on the foundation slab according to the positioning, and pre-embed the inclined support connecting parts; After the prepared lattice bracing is processed and passes inspection, it is hoisted to the predetermined position and welded to the bracing connecting embedded parts and the bored piles located at the bracing support piers. Step (4): At this time, the lattice bracing and concrete support exist simultaneously. The concrete support is statically removed. After the concrete support is removed and cleared, the reinforcement, formwork and subsequent concrete pouring work of the ramp basement exterior wall begins. After the basement exterior walls are poured, subsequent construction will proceed, including the structural construction of the basement floor slab and the basement roof slab, and the completion of the remaining ramp structure. Step (5): After the ramp structure, the first basement floor slab and the basement roof slab are poured and cured, the grid bracing outside the basement exterior wall is statically removed and backfilled together with the earthwork. The part inside the basement exterior wall is chiseled, cut and removed and cleaned. Step (6): Next, the inclined support pier is chiseled away and the reinforcing bars are cut off. After rust removal, anti-rust paint is applied. The bottom slab is poured for the second time, and waterproofing construction of the bottom slab is carried out again in this area or other waterproofing measures are taken.

[0005] Furthermore, the jet grouting piles, triaxial cement mixing piles and bored piles driven in step (1) are used as retaining structures to resist the soil and water pressure outside the foundation pit during the subsequent foundation pit excavation process, so as to prevent the foundation pit from collapsing. The slope protection is used to protect the slope of the foundation pit and prevent the slope of the foundation pit from becoming unstable and collapsing; The intercepting ditch is used for draining surface water outside the foundation pit to prevent water from entering the foundation pit; The concrete supports are used to provide horizontal reaction forces and limit the displacement of the enclosure structure.

[0006] Furthermore, the intercepting ditch in step (1) is connected to the slope protection, and the slope protection is connected to the three-axis cement mixing pile.

[0007] Furthermore, in step (2), after the concrete support is poured and the concrete strength reaches 100%, earthwork excavation will begin.

[0008] Furthermore, in step (3), the crushed stone backfill between the foundation slab and the bored pile is used to improve the bearing capacity of the shallow foundation below the foundation bottom, improve the stability of the foundation, and transfer stress to protect the foundation and retaining structure.

[0009] Furthermore, in step (3), steel bars and stirrups are installed inside the inclined support pier to ensure strength during subsequent support processes.

[0010] Furthermore, the lattice bracing mentioned in step (3) includes reinforcing angle steel, main support steel, and gusset plates. The main support steel is reinforced with welded angle steel and gusset plates. Among them, the reinforcing angle steel is located at the nodes or connections of the lattice steel, which uniformly transmits axial force and shear force, reduces stress concentration, and ensures that the load is reasonably distributed among the lattice steel. The gusset plate is used to bear the shear force generated when the lattice steel is subjected to load and bends around the virtual axis, thus distributing the load.

[0011] Furthermore, the static removal of the concrete support in step (4) is to avoid damaging the lattice bracing; Subsequent construction began 48 hours after the basement exterior walls were poured.

[0012] Furthermore, in step (5), after static cutting of the lattice bracing, some lattice steel remains on the basement exterior wall; the structure containing this part of the lattice steel is chiseled away, steel bars are added and welded; then the location is poured and vibrated a second time, and subsequent waterproofing construction is strengthened.

[0013] Furthermore, in step (6), high-strength polymer mortar is used for the second pouring of the base plate.

[0014] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: 1. When the basement foundation slab is completed but the ramp cannot be constructed, this invention replaces the original reinforced concrete support system with a deep foundation pit lattice-type steel internal inclined bracing support system, avoiding the impact of reinforced concrete support on the construction of other underground and above-ground structures within its coverage area; 2. The deep foundation pit lattice-type steel internal inclined bracing support system consists of the basement floor slab and base, the original support system's supporting capping beam or waler beam, and newly installed lattice-type steel inclined bracing. It can transmit the lateral forces of the soil on the retaining piles and capping beam to the base and basement floor slab through the lattice-type steel inclined bracing. After this system takes effect, the original reinforced concrete support can be removed; 3. After the support system is replaced, the ramp and other above-ground and underground structures are no longer constrained by the original reinforced concrete support system and can be constructed independently. During ramp construction, the top of the exterior wall can be completed in one go and poured together with the top slab. Attached Figure Description

[0015] Figure 1 This is a schematic cross-section of the structure of the present invention. Figure 1 ; Figure 2 This is a schematic cross-section of the structure of the present invention. Figure 2 ; Figure 3 This is a cross-sectional view of the concrete support for the base plate of the present invention; Figure 4 This is a schematic diagram of the pre-embedded diagonal brace of the present invention; Figure 5 This is a schematic diagram showing the connection between the diagonal brace and the cap beam and waler beam of the present invention; In the diagram, 1 is the basement roof slab, 2 is the concrete support, 3 is the first basement floor slab, 4 is the lattice brace, 5 is the brace support pier, 6 is the foundation slab, 7 is the graded crushed stone backfill, 8 is the jet grouting pile, 9 is the triaxial cement mixing pile, 10 is the bored cast-in-place pile, 11 is the intercepting ditch, 12 is the slope protection, 13 is the basement exterior wall, 14 is the brace connecting embedded part, 15 is the reinforcing angle steel, 16 is the main support steel, and 17 is the connecting plate. Detailed Implementation

[0016] The specific technical solution of the present invention will be further described in detail below with reference to specific examples.

[0017] As shown in the figure, the present invention provides a method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device. The optimized ramp construction process is as follows: basement foundation slab and inclined support base → installation of steel inclined supports → completion of basement exterior wall and roof construction → support removal (the remaining surrounding structures can be constructed) → exterior wall waterproofing and backfilling → ramp base slab cushion layer and waterproofing → ramp base slab → ramp wall panel and roof structure; the construction of the remaining surrounding structures is advanced, and the ramp wall panel and roof structure are no longer constructed in two stages. The purpose of this invention is to allow for the construction of the ramp structure immediately after the foundation slab 6 has been poured, the graded crushed stone backfill 7 has been completed, and the concrete supports 2 have been removed. This is achieved by using a lattice-type steel diagonal brace (4, diagonal brace piers 5, diagonal brace connecting embedded parts 14, reinforcing angle steel 15, main support steel 16, and connecting plates 17) to withstand the soil pressure transmitted from the outside of the jet grouting piles 8, the triaxial cement mixing piles 9, and the bored piles 10. Simultaneously, since the ramp structure, basement roof slab 1, first basement floor slab 3, and basement exterior walls 13 are not yet fully constructed, this method can protect the foundation pit and personnel safety. Specifically, the following steps are included: Step (1): Before all construction processes, jet grouting piles 8, three-axis cement mixing piles 9 and bored piles 10 are driven into the required positions in sequence to form a retaining structure to resist the soil and water pressure on the outside of the foundation pit during the subsequent excavation process, so as to prevent the foundation pit from collapsing. Slope protection 12 is constructed on the top of the retaining wall to protect the slope of the foundation pit and prevent the slope of the foundation pit from becoming unstable and collapsing; then, intercepting ditch 11 is constructed to drain surface water outside the foundation pit and prevent water from entering the foundation pit. Step (2): After the jet grouting piles 8, the three-axis cement mixing piles 9 and the bored piles 10 of the pile foundation retaining structure are completed, the construction of concrete support 2 is carried out simultaneously with the intercepting ditch 11 and the slope protection 12. The main function of concrete support 2 is to provide horizontal reaction force, limit the displacement of the retaining structure, and transfer the water and soil pressure on the outside of the retaining structure to the other components, thereby reducing structural deformation. After the concrete support 2 is poured and the concrete strength reaches 100%, earthwork excavation will begin; then, the cushion layer and the base slab will be poured in sequence to form the foundation slab 6. Step (3): Graded crushed stone backfill 7 is set between the foundation slab 6 and the bored pile 10. Its function is to improve the bearing capacity of the shallow foundation below the foundation bottom surface, and its good permeability can quickly drain groundwater or water accumulation, improve the stability of the foundation, and transfer stress to protect the foundation and retaining structure. Lay out the positioning lines, and pour the inclined bracing piers 5 on the foundation slab 6 according to the positioning, and pre-embed the inclined bracing connecting parts 14; wherein, the inclined bracing piers 5 need to be equipped with sufficient steel bars and stirrups to ensure the strength in the subsequent support process. Step (4): Use the main support steel 16 as the primary material for processing the lattice brace 4, and weld the reinforcing angle steel 5 and the gusset plate 17. Among them, the reinforcing angle steel 15 is located at the node or connection of the lattice steel, which can uniformly transmit axial force and shear force, reduce stress concentration, and ensure that the load is reasonably distributed among the lattice steel. The gusset plate 17 bears the shear force generated when the lattice steel is subjected to load and bends around the virtual axis, thus distributing the load. Step (5): After the lattice bracing 4 is processed and passes the inspection by the testing unit, use the on-site tower crane and truck crane to lift it to the predetermined position and weld it between the bracing connecting embedded part 14 and the bored pile 10 located at the bracing support pier 5. Since the lattice brace 4 and the concrete support 2 exist at the same time, the concrete support 2 needs to be statically removed to avoid damaging the lattice brace 4. After the concrete support 2 is removed and cleared, the work of reinforcing steel, formwork and subsequent concrete pouring of the outer wall 13 of the ramp basement will begin. Step (6): 48 hours after the basement exterior wall 13 is poured, the subsequent construction will begin; the structural construction of the basement floor slab 3 and the basement roof slab 1 will be carried out in sequence, and the remaining ramp structure will be completed. After the ramp structure, the first basement floor slab 3 and the basement roof slab 1 are poured and cured, the grid bracing 4 outside the basement exterior wall 13 is statically removed and backfilled together with the earthwork. The part inside the basement exterior wall 13 is chiseled, cut and removed and cleared. Step (7): After static cutting of the lattice brace 4, some lattice steel remains on the basement exterior wall 13; the structure where this part of the lattice steel is located is chiseled away, steel bars are added and welded; then the location is poured and vibrated again, and subsequent waterproofing construction is strengthened. The inclined support pier 5 should be chiseled away and the reinforcing steel cut off. After rust removal, apply anti-rust paint. Use high-strength polymer mortar to pour the base slab a second time, and redo the base slab waterproofing in this area, or take other waterproofing measures.

[0018] Working principle: In the basement stage after the completion of the retaining pile foundation structure, support structure, and earthwork excavation, the construction of ramp structures is generally delayed in the actual construction process. After the foundation slab is completed, the ramp cannot be constructed directly like other structures. Moreover, in a large number of commercial buildings, the number of projects with car ramps located in the corner area of ​​the foundation pit is quite significant. It is necessary to wait for the completion of the basement exterior walls 13 and basement roof slab 1 in other areas before excavating and constructing the ramp area. Furthermore, due to the complexity of the retaining design of large or deep foundation pits, some key areas have concrete supports, which can hinder the construction of the ramp structure. It may even be necessary to wait until the superstructure is completed before conducting secondary excavation and construction of the ramp.

[0019] To expedite the construction of this structure, part of the concrete support 2 will be removed, and steel diagonal bracing (grid diagonal bracing 4) will be used to replace the support to protect the foundation pit and ensure the safety of construction personnel. Before installing the steel diagonal bracing, embedded parts (diagonal bracing connection embedded parts 14) need to be installed on the base slab and retaining piles, and diagonal bracing piers 5 need to be poured as diagonal bracing feet. Finally, the installation and fixing welding operations will be carried out. The concrete support must not be removed before the construction of the steel diagonal bracing is completed, as this will lead to instability of the foundation pit. After the ramp structure is completed, since the lattice columns themselves are made by welding, static cutting is used on the lattice columns outside the structure. Then, the exterior walls and ramp base plate are repaired according to the above method, which can greatly save the construction period. However, this invention requires secondary pouring of the basement ramp exterior walls and base plate, which is prone to gaps and is almost unavoidable. It is necessary to raise the standards and requirements for waterproofing the exterior walls and basement in the later stage to avoid water leakage from the exterior walls and base plate.

Claims

1. A method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device, characterized in that, Includes the following steps: Step (1): Before all construction processes, jet grouting piles (8), three-axis cement mixing piles (9) and bored piles (10) are driven into the required positions in sequence. After the jet grouting piles (8), the three-axis cement mixing piles (9) and the bored piles (10) are driven into the ground, the slope protection (12) and the intercepting ditch (11) are constructed on the top of the retaining wall, and the concrete support (2) is constructed simultaneously. Step (2): After the concrete support (2) is poured, earthwork excavation begins; then, the cushion layer and the bottom plate are poured on the other side of the bored pile (10) to form the foundation slab (6). Step (3): Set graded crushed stone backfill (7) between the foundation slab (6) and the bored pile (10); lay out the positioning line, pour the inclined support pier (5) on the foundation slab (6) according to the positioning, and pre-embed the inclined support connecting parts (14). After the prepared lattice bracing (4) is processed and inspected and qualified, it is hoisted to the predetermined position and welded to the bracing connecting embedded part (14) and the bored pile (10) located at the bracing support (5). Step (4): At this time, the lattice bracing (4) and the concrete support (2) exist simultaneously. The concrete support (2) is statically removed. After the concrete support (2) is removed and cleared, the reinforcement, formwork and subsequent concrete pouring work of the outer wall (13) of the ramp basement will begin. After the basement exterior wall (13) is poured, subsequent construction will be carried out, including the construction of the basement floor slab (3) and the basement roof slab (1) in sequence, and the remaining ramp structure will be completed. Step (5): After the ramp structure, the first basement floor slab (3) and the basement roof slab (1) have been poured and cured, the grid bracing (4) outside the basement exterior wall (13) is statically removed and backfilled together with the soil. The part inside the basement exterior wall (13) is chiseled, cut and removed and cleared. Step (6): Next, chisel away the inclined support pier (5) and cut off the reinforcing bars. After removing the rust, apply anti-rust paint. Then, pour the bottom slab for the second time and carry out waterproofing construction on the bottom slab in this area or take other waterproofing measures.

2. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, The jet grouting piles (8), triaxial cement mixing piles (9) and bored piles (10) driven in step (1) are used as retaining structures to resist the soil and water pressure outside the foundation pit during the subsequent foundation pit excavation process, so as to prevent the foundation pit from collapsing. The slope protection (12) is used to protect the slope of the foundation pit and prevent the slope of the foundation pit from becoming unstable and collapsing; The intercepting ditch (11) is used for draining surface water outside the foundation pit to prevent water from entering the foundation pit; The concrete support (2) is used to provide horizontal reaction force and limit the displacement of the enclosure structure.

3. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, The intercepting ditch (11) in step (1) is connected to the slope protection (12), and the slope protection (12) is connected to the three-axis cement mixing pile (9).

4. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, In step (2), after the concrete support (2) is poured and the concrete strength reaches 100%, earthwork excavation will begin.

5. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, In step (3), the crushed stone backfill (7) between the foundation slab (6) and the bored pile (10) is used to improve the bearing capacity of the shallow foundation below the foundation bottom, improve the stability of the foundation, and transfer stress to protect the foundation and retaining structure.

6. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, In step (3), steel bars and stirrups are installed inside the inclined support pier (5) to ensure the strength during the subsequent support process.

7. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, The lattice bracing (4) mentioned in step (3) includes reinforcing angle steel (15), main support steel (16) and gusset plate (17). The main support steel (16) is welded with reinforcing angle steel (15) and gusset plate (17). Among them, the reinforcing angle steel (15) is located at the node or connection of the lattice steel, which uniformly transmits axial force and shear force to reduce stress concentration and ensures that the load is reasonably distributed between the lattice steel. The gusset plate (17) bears the shear force generated when the lattice steel is subjected to load and bends around the virtual axis, thus distributing the load.

8. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, In step (4), the concrete support (2) is statically removed to avoid damaging the lattice brace (4). Subsequent construction will begin 48 hours after the basement exterior wall (13) is poured.

9. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, In step (5), after static cutting of the lattice brace (4), some lattice steel remains on the basement exterior wall (13); the structure where this part of the lattice steel is located is chiseled away, steel bars are added and welded; then the location is poured and vibrated a second time, and subsequent waterproofing construction is strengthened.

10. The method for accelerating the construction of a ramp located at the boundary of a foundation pit using a lattice-type steel inclined support device according to claim 1, characterized in that, In step (6), high-strength polymer mortar is used for the second pouring of the base plate.

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