Steel lattice inclined strut and support pile combined foundation pit support construction method

Abstract

The invention discloses a steel lattice inclined strut and support pile combined foundation pit support construction method. The method comprises the following steps that 1, construction preparation is conducted; step 2, constructing a support pile and an inclined strut support pile; 3, excavating earth in the middle of the foundation pit; 4, constructing a top beam, a bracket and an inclined strut support structure; 5, steel lattice inclined struts are installed and constructed; and 6, foundation pit earth excavation and retaining wall construction are carried out. The construction period influence is small, cross construction confusion is avoided, and many defects of a traditional inner supporting system are overcome. The steel lattice inclined throwing support is simple in structure, flexible in arrangement and relatively convenient and fast to mount and dismount, inclined support materials can be partially and repeatedly utilized, only a small part of space in a foundation pit can be occupied, and a new process technology is provided for foundation pit supporting construction.

Description

Technical Field

[0001] The invention relates to the field of foundation pit support construction methods, in particular to a foundation pit support construction method combining steel lattice diagonal braces and support piles. Background Art

[0002] With the development of urban high-rise buildings and underground space construction, more and more deep foundation pit projects are close to existing dense buildings and traffic arteries, which puts forward very strict requirements on the stability and displacement control of foundation pit support. The restricted enclosure structure shall not exceed the land red line requirements, and its support form mostly adopts support piles plus internal support structure system.

[0003] The Chinese invention patent application with application publication number CN 104947682 A discloses a foundation pit support construction method and device thereof. The patent adopts a support system composed of supporting piles and diagonal braces, and uses the existing concrete basement floor structure as the diagonal brace fulcrum to form a support system. The foundation pit earthwork is excavated in sections, and the diagonal braces are removed after the underground structure construction is completed. The installation of the diagonal braces for the foundation pit support of this construction method must be implemented after the concrete structure of the basement floor reaches a certain strength. After the installation of the diagonal braces is completed, the construction of the remaining earthwork and structure around the basement can be carried out. The interval time for the construction of the basement floor concrete structure is relatively long, which affects the construction period. In addition, after the construction of the basement concrete floor structure in the middle of the foundation pit, the excavation and transportation of the surrounding earthwork will be affected. In order to overcome the above shortcomings, a foundation pit support construction method combining steel lattice diagonal braces and supporting piles is developed. Summary of the invention

[0004] The invention provides a foundation pit support construction method combining steel lattice diagonal braces and supporting piles, so as to solve the problems of great influence on construction period and chaotic cross-construction existing in the foundation pit support construction method in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A foundation pit support construction method combining steel lattice diagonal bracing and supporting piles comprises the following steps: Step 1: Construction preparation Prepare foundation pit support construction equipment and steel lattice diagonal braces; Step 2: Construction of support piles and diagonal support piles According to the design drawings in the construction plan, the support piles and the diagonal bracing piles are positioned and laid out respectively. After verification, a rotary drilling rig is used to dig pile holes at the respective positioning and laying-out positions of the support piles and the diagonal bracing piles, and pile foundation steel cages are placed in the pile holes, and pile foundation concrete is poured, thereby obtaining support piles and diagonal bracing piles; Step 3: Excavation of the middle part of the foundation pit According to the outline of the building basement and the position of the diagonal support structure, the earth excavation line is measured and laid out. The earth excavation range is the inner side of the diagonal support structure. Then, earth excavation is carried out according to the earth excavation line. The slope of the foundation pit is excavated by slope laying to ensure the stability of the slope. Step 4: Construction of crown beam, corbel and diagonal brace support structure. The process is as follows: (4.1) When the concrete strength of the supporting piles and diagonal bracing piles around the foundation pit reaches 80%, start the construction of the crown beam and corbel on the supporting piles, as well as the diagonal bracing structure on the diagonal bracing piles; (4.2) Use an excavator to remove the soil on the supporting piles and the diagonal bracing piles to expose the pile bodies; according to the designed elevation of the top of the supporting piles and the diagonal bracing piles, remove the concrete at the pile heads of the supporting piles and the diagonal bracing piles, and adjust the reserved anchor steel bars exposed at the pile heads of the supporting piles and the diagonal bracing piles.

[0006] (4.3) Install the crown beam and corbel on the upper part of the support piles, and install the diagonal brace support structure formwork on the upper part of the diagonal brace support piles, and tie the steel bars respectively, and install the embedded steel plates on the corbel and diagonal brace support structure to fix the steel lattice diagonal brace; after checking that everything is correct, pour the crown beam, corbel and diagonal brace support structure concrete; Step 5: Installation and construction of steel lattice diagonal braces. The process is as follows: The steel lattice diagonal brace 1 manufactured in the factory is transported to the construction site to verify the specifications, dimensions and material quality.

[0007] The steel lattice brace is lifted by a crane and placed between the corresponding corbel and the brace support structure to adjust and fix the steel lattice brace. The steel lattice brace and the brace support structure use flexible ends. The jack is installed and the pre-tightening force is fixed by adjusting the pre-tightening nut. 10% of the designed pre-loaded axial force is applied. The steel wedge is inserted into the gap between the steel lattice brace and the embedded steel plate of the brace support structure. The steel plate is filled to ensure that the steel plate does not shift and the steel lattice brace is stressed. After the adjustment is qualified, it is fixed firmly by electric welding. Then, the connection is filled with fine stone concrete and vibrated to be dense, which plays a protective and uniform stress role; the steel lattice brace and the embedded steel plate of the crown beam corbel are welded firmly. A water-blocking steel plate is set at the intersection of the steel lattice brace and the basement concrete wall panel to stop the water of the basement concrete wall panel.

[0008] Step 6: Excavation of foundation pit and wall construction After the steel lattice diagonal bracing is completed, the excavator excavates the remaining earth around the foundation pit in layers and sections until the foundation pit base elevation is reached. During the excavation process, the foundation pit retaining wall is constructed on the side of the supporting piles. Drainage pipes are set on the retaining wall between the supporting piles to drain the water in the soil layer and reduce the pressure on the retaining wall side. Drainage ditches and water collection wells are set around the foundation pit.

[0009] In the further step 3, the earth excavation sequence is: excavate the earth in layers from the middle of the building basement to the periphery until the inner excavation line of the diagonal support structure 5 is reached, then stop the earth excavation and keep the earth around the foundation pit.

[0010] In the further step 5, a water-blocking steel plate is arranged at the intersection of the steel lattice diagonal brace and the basement concrete wall slab to play a role in water blocking the basement concrete wall slab.

[0011] Compared with the prior art, the present invention has the following advantages: The present invention adopts a foundation pit support system composed of supporting piles and steel lattice diagonal braces, which is composed of supporting piles + steel lattice diagonal braces + diagonal brace support structure + diagonal brace support piles. After the diagonal braces are erected, they do not affect the overall pouring of the bottom plate concrete, have little impact on the construction period, avoid cross-construction chaos, and overcome many shortcomings of the traditional internal support system. The steel lattice diagonal brace has a simple structure, flexible layout, and is relatively easy to install and disassemble. The diagonal brace material can be partially reused and only occupies a small part of the space in the foundation pit, providing a new process technology for foundation pit support construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a construction flow chart of the present invention.

[0013] Figure 2 It is a side view of the present invention.

[0014] Figure 3 It is a plan view of the present invention.

[0015] Figure 4 It is a side view of the diagonal brace support structure of the present invention.

[0016] Figure 5 1 is a structural diagram of a steel lattice diagonal brace of the present invention, wherein (a) is a front view, (b) is a top view, and (c) is a schematic diagram of the position of a water-blocking steel plate. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0018] like Figure 1 As shown, this embodiment discloses a foundation pit support construction method combining steel lattice diagonal bracing and supporting piles, comprising the following steps: Step 1: Construction preparation Based on the geological survey report, foundation pit depth, surrounding environment, building shape and other factors, after in-depth research, the foundation pit support form was determined and the construction plan was optimized.

[0019] Prepare foundation pit support construction equipment, such as pile foundation drilling machines, excavators, etc.

[0020] According to the design drawings of steel lattice inclined support 1, the factory is commissioned to process and manufacture. Figure 5 As shown in (a) and (b), the steel lattice diagonal brace 1 is composed of angle steel 11 and tie plates 12, wherein the angle steel 11 forms a rectangle, and the tie plates 12 are welded and fixed to the outer periphery of the rectangle, thereby forming the steel lattice diagonal brace 1, and steel plates are arranged at both ends of the steel lattice diagonal brace 1.

[0021] Step 2: Construction of support piles 2 and diagonal support piles 6 According to the design drawings in the construction plan, the support piles 2 and the diagonal support piles 6 are positioned and laid out respectively. After verification, a rotary drilling machine is used to dig pile holes at the respective positioning and laying positions of the support piles 2 and the diagonal support piles 6. When digging holes, the top elevations of the support piles 2 and the diagonal support piles 6 are controlled. Then, the pile foundation steel cage is dug out and placed in the pile hole, and the pile foundation concrete is poured, thereby obtaining the support piles 2 and the diagonal support piles 6.

[0022] Step 3: Excavation of the middle part of the foundation pit After the construction of the support piles 2 and the diagonal brace support piles 6 is completed, the foundation pit earthwork excavation is carried out. According to the outline of the building basement and the position of the diagonal brace support structure 5, the earthwork excavation line is measured and laid out. The earthwork excavation range is the inner side of the diagonal brace support structure position 5. Then, earthwork excavation is carried out according to the earthwork excavation line. The slope of the foundation pit earthwork is excavated in layers from the middle of the building basement to the surrounding periphery until the excavation line inside the diagonal brace support structure 5 is reached. The earthwork excavation is stopped and the earthwork around the foundation pit is retained.

[0023] Step 4: Construction of the crown beam 3, the corbel 4 and the diagonal support structure 5. The process is as follows: (4.1) When the concrete strength of the supporting piles 2 and the diagonal bracing piles 6 around the foundation pit reaches 80%, start the construction of the cap beam 3 and corbel 4 on the supporting piles 2, and the diagonal bracing structure 5 on the diagonal bracing piles 6.

[0024] (4.2) Use an excavator to dig away the soil on the supporting pile 2 and the diagonal bracing pile 6 to expose the pile body; according to the designed elevation of the pile top of the supporting pile 2 and the diagonal bracing pile 6, break the pile head concrete of the supporting pile 2 and the diagonal bracing pile 6, and adjust the reserved anchor steel bars exposed at the pile head of the supporting pile 2 and the diagonal bracing pile 6.

[0025] (4.3) Support the crown beam 3 and the corbel 4 on the upper part of the supporting pile 2, and support the diagonal brace support structure 5 formwork on the upper part of the diagonal brace support pile 6, and tie the steel bars respectively, and install the embedded steel plates on the corbel 4 and the diagonal brace support structure 5 to fix the steel lattice diagonal brace 1; after checking that everything is correct, pour the concrete of the crown beam 3, the corbel 4 and the diagonal brace support structure 5.

[0026] Step 5: Figure 3 , Figure 4 As shown, the installation and construction process of the steel lattice diagonal brace 1 is as follows: The steel lattice diagonal brace 1 manufactured in the factory is transported to the construction site to verify the specifications, dimensions and material quality.

[0027] The steel lattice brace 1 is lifted by a crane and placed between the corresponding corbel 4 and the brace support structure 5, and the steel lattice brace 1 is adjusted and fixed. The steel lattice brace 1 and the brace support structure 5 use flexible ends, and the jack is installed and the pre-tightening force is fixed by adjusting the pre-tightening nut. 10% of the designed pre-loaded axial force is applied, and the steel wedge is inserted into the gap between the steel lattice brace 1 and the embedded steel plate of the brace support structure 5. The gap is filled with the steel plate to ensure that the steel plate does not shift, so that the steel lattice brace 1 is stressed. After the adjustment is qualified, it is fixed firmly by electric welding, and then the connection is filled with fine stone concrete, and vibrated and compacted to play a protective and uniform stress role; the steel lattice brace 1 and the embedded steel plate of the crown beam corbel 4 are welded firmly. A water-blocking steel plate 13 is set at the intersection of the steel lattice brace 1 and the basement concrete wall panel to play a water-stopping role for the basement concrete wall panel.

[0028] Use a crane to lift the steel lattice brace 1 to the corresponding position, adjust the steel lattice brace 1, install a jack on the loose end of the steel lattice brace 1 and fix the pre-tightening force by adjusting the pre-tightening nut, apply 10% of the designed pre-loaded axial force, insert a steel wedge into the gap between the steel lattice brace 1 and the embedded steel plate of the brace support structure 5, and when the steel plate is filled, ensure that the steel plate does not shift so that the steel lattice brace 1 is stressed. After the adjustment is qualified, it is firmly fixed by electric welding, and then filled with fine stone concrete and vibrated to be dense, which plays a protective and uniform stress role. Figure 5 As shown in (c), a water-blocking steel plate 13 is arranged at the intersection of the steel lattice diagonal brace 1 and the basement concrete wall slab to stop water from entering the basement concrete wall slab.

[0029] Step 6: Excavation of foundation pit and construction of retaining wall 7 After the construction of the steel lattice diagonal brace 1 is completed, the excavator excavates the remaining earth around the foundation pit in layers and sections until the foundation pit base 9 is elevated. During the excavation process, the foundation pit retaining wall 7 is constructed on the side of the supporting piles 2. Drain pipes 8 are set on the retaining wall 7 between the supporting piles 2 to drain water in the soil layer and reduce the pressure on the side of the retaining wall 7. Drainage ditches and water collection wells are set around the foundation pit, and the final foundation pit support structure is as follows: Figure 2 shown.

[0030] After the foundation pit support construction is completed, the relevant personnel of the supervision unit, design unit, and exploration unit are organized to inspect and accept the foundation pit support project. After the acceptance is qualified, the basement structure of the building is constructed. After the basement structure construction is completed, the steel lattice diagonal brace 1 is cut off, and the earth between the basement and the foundation pit is backfilled and compacted in layers.

[0031] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. The various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction, and such combinations should also be regarded as the contents disclosed in the present disclosure as long as they do not violate the concept of the present invention. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0032] The present invention is not limited to the specific details of the above-mentioned embodiments. Within the technical concept of the present invention and without departing from the design concept of the present invention, various modifications and improvements made to the technical solution of the present invention by technical personnel in this field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the claims.

Claims

1. A foundation pit support construction method combining steel lattice diagonal bracing and supporting piles, characterized in that: The following steps are involved: Step 1: Construction preparation Prepare foundation pit support construction equipment and steel lattice diagonal braces; Step 2: Construction of support piles and diagonal support piles According to the design drawings in the construction plan, the support piles and the diagonal bracing piles are positioned and laid out respectively. After verification, a rotary drilling rig is used to dig pile holes at the respective positioning and laying-out positions of the support piles and the diagonal bracing piles, and pile foundation steel cages are placed in the pile holes, and pile foundation concrete is poured, thereby obtaining support piles and diagonal bracing piles; Step 3: Excavation of the middle part of the foundation pit According to the outline of the building basement and the position of the diagonal support structure, the earth excavation line is measured and laid out. The earth excavation range is the inner side of the diagonal support structure. Then, earth excavation is carried out according to the earth excavation line. The slope of the foundation pit is excavated by slope laying to ensure the stability of the slope. Step 4: Construction of crown beam, corbel and diagonal brace support structure. The process is as follows: (4.1) When the concrete strength of the supporting piles and diagonal bracing piles around the foundation pit reaches 80%, start the construction of the crown beam and corbel on the supporting piles, as well as the diagonal bracing structure on the diagonal bracing piles; (4.2) Use an excavator to remove the soil on the supporting piles and the diagonal bracing piles to expose the pile bodies; according to the designed elevation of the top of the supporting piles and the diagonal bracing piles, remove the concrete at the pile heads of the supporting piles and the diagonal bracing piles, and adjust the reserved anchoring steel bars exposed at the pile heads of the supporting piles and the diagonal bracing piles; (4.3) Install the crown beam and corbel on the upper part of the support piles, and install the diagonal brace support structure formwork on the upper part of the diagonal brace support piles, and tie the steel bars respectively, and install the embedded steel plates on the corbel and diagonal brace support structure to fix the steel lattice diagonal brace; after checking that everything is correct, pour the crown beam, corbel and diagonal brace support structure concrete; Step 5: Installation and construction of steel lattice diagonal braces. The process is as follows: Use a crane to lift the steel lattice brace, place it between the corresponding corbel and brace support structure, and adjust and fix the steel lattice brace. The steel lattice brace and the brace support structure use flexible ends. Install the jack and fix the pre-tightening force by adjusting the pre-tightening nut. Apply 10% of the designed pre-axial force. Insert a steel wedge into the gap between the steel lattice brace and the embedded steel plate of the brace support structure. Fill it with a steel plate to ensure that the steel plate does not shift so that the steel lattice brace is stressed. After qualified adjustment, fix it firmly with electric welding, fill the joint with fine stone concrete, and vibrate it to compact it to protect it and evenly bear the force. The steel lattice brace and the embedded steel plate of the crown beam corbel are firmly welded. Set a water-blocking steel plate at the intersection of the steel lattice brace and the basement concrete wall slab to stop the water flow of the basement concrete wall slab. Step 6: Excavation of foundation pit and wall protection construction After the steel lattice diagonal bracing is completed, the excavator excavates the remaining earth around the foundation pit in layers and sections until the foundation pit base elevation is reached. During the excavation process, the foundation pit retaining wall is constructed on the side of the supporting piles. Drainage pipes are set on the retaining wall between the supporting piles to drain the water in the soil layer and reduce the pressure on the retaining wall side. Drainage ditches and water collection wells are set around the foundation pit.

2. The method for foundation pit support construction of a combination of steel lattice diagonal braces and supporting piles according to claim 1 is characterized in that: In step 3, the order of earth excavation is: excavate the earth in layers from the middle of the building basement to the periphery until the inner excavation line of the diagonal support structure 5 is reached, stop the earth excavation, and retain the earth around the foundation pit.

3. The method for foundation pit support construction of steel lattice diagonal braces and supporting piles according to claim 1 is characterized in that: In step 5, a water-blocking steel plate is installed at the intersection of the steel lattice diagonal brace and the basement concrete wall slab to play a water-blocking role for the basement concrete wall slab.

Images