CN111894010A - A foundation pit enclosure structure and construction method based on prefabricated slabs and diagonal braces - Google Patents

Abstract

The invention discloses a foundation pit support structure based on precast slabs and inclined struts and a construction method. The foundation pit support structure comprises prefabricated plates, a triaxial cement-soil mixing pile, a crown beam, a steel inclined strut and a connecting plate, wherein the prefabricated plates are inserted into the triaxial cement-soil mixing pile, the crown beam is anchored on the prefabricated plates in a cast-in-place mode, the connecting plate is anchored between two adjacent prefabricated plates in a cast-in-place mode, the upper end of the steel inclined strut is fixedly connected with the prefabricated plates, the lower end of the steel inclined strut is fixedly connected with a basement bottom plate, side grooves and middle grooves are formed in the connecting plate, the side grooves are symmetrically arranged in the direction of the short edge of the section of the prefabricated plates along the long edge, the middle grooves are arranged at the positions, corresponding to the basement bottom. One part of the enclosure structure can be used as a basement main body structure, and the other part can be recycled, so that the construction cost is low; the construction period is short, and the quality is controllable; the application range is wide.

Description

A foundation pit enclosure structure and construction method based on prefabricated slabs and diagonal braces

technical field

The invention relates to a foundation pit enclosure structure and a construction method, in particular to a novel foundation pit enclosure structure and construction method based on prefabricated slabs and diagonal braces.

Background technique

With the rapid increase in the number of cars in the city, buildings are generally set up with basements to facilitate the parking of cars. In order to obtain a larger basement space, the architectural design often makes the outer wall of the basement close to the red line of the building land, and the red line of the building land is often close to the surrounding buildings and roads. Excavation, must adopt the enclosure structure for the foundation pit.

The purpose of setting up the enclosure structure of the foundation pit is to ensure the stability of the foundation pit slope, facilitate earthwork excavation, and protect the safety of buildings, roads and pipelines around the foundation pit. The conventional foundation pit enclosure structure has high cost and long construction period, and is often buried in the backfill soil after the basement construction is completed, resulting in a great waste. In addition, the enclosing structure of the foundation pit buried in the ground also hinders the burying of the underground pipeline. Therefore, it is an urgent requirement for the design and construction of the foundation pit enclosure to take the enclosure structure as a part of the main structure of the basement.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the prior art, the present invention provides a foundation pit enclosure structure and a construction method with simple structure, rapid construction, low cost and recyclability.

To achieve the above object, the present invention provides the following technical solutions:

A foundation pit enclosure structure based on prefabricated slabs and diagonal braces, including prefabricated slabs, triaxial cement-soil mixing piles, crown beams, steel diagonal braces, and connecting plates, the prefabricated slabs are inserted into the triaxial cement-soil mixing piles, so The crown beam is cast-in-place anchored on the prefabricated plate, the connecting plate is cast-in-place anchored between two adjacent prefabricated slabs, the basement bottom plate is set at the bottom of the foundation pit, and the basement top plate is set at the top of the foundation pit, so the The steel diagonal brace is inclined in the foundation pit, its upper end is fixedly connected with the prefabricated plate, and its lower end is fixedly connected with the basement floor, the connecting plate is provided with a side groove and a middle groove, and the side grooves are symmetrically arranged In the direction of the short side along the long side of the cross section of the prefabricated panel, the middle groove is arranged at the position of the prefabricated panel corresponding to the basement floor, the basement floor extends and is connected to the middle groove, and the connecting plate is fixedly connected to the side grooves .

Further, the prefabricated plate is a prestressed reinforced concrete prefabricated member, and bolt holes are reserved toward the side of the foundation pit.

Further, the length of the prefabricated plate is twice the depth of the foundation pit, the top ribbed steel bar protrudes from the top of the prefabricated plate, the top ribbed steel bar is embedded in the crown beam, and the inner side of the side groove is outward. There are side ribbed steel bars protruding, the width of the side grooves is 1/2 of the width of the prefabricated plate, the middle ribbed steel bars are protruding from the inner side of the middle groove, and the width of the middle groove is the same as that of the basement floor. of the same width.

Further, the length of the top ribbed steel bar is 0.3m, the spacing is 0.5m, the depth of the side groove and the middle groove are both 0.2m, and the length of the side ribbed steel bar and the middle ribbed steel bar is 0.2m. Both are 0.1m, and the spacing is 0.2m.

Further, the width of the triaxial cement-soil mixing pile is 1.5 times the width of the prefabricated plate.

Furthermore, the crown beam is arranged on the top of the prefabricated slab and is a cast-in-place reinforced concrete structure, the height of the crown beam is 0.5m, and the width exceeds 1/3 of the width of the prefabricated slab.

Further, the steel diagonal brace is a supporting prefabricated plate, the cross section is circular, the diameter is 0.3-0.6 m, and the spacing is 2-4 m.

Further, the connecting plate is a cast-in-place reinforced concrete structure, which is used to connect two adjacent prefabricated plates, and the connecting plate is provided with a stressed steel bar, and the stressed steel bar of the connecting plate is connected to the side edge through a steel sleeve. Ribbed steel bars are mechanically connected.

A construction method for a foundation pit enclosure structure based on prefabricated slabs and diagonal braces, comprising:

Step 1: Excavate the trench for the exterior wall of the basement, first construct two sections of three-axis cement-soil mixing piles, and then insert a prefabricated board into the pile body by its own weight before the initial setting of the pile body, and repeat the cycle until all three steps are completed. Construction of shaft cement-soil mixing piles and prefabricated slabs;

Step 2: Cast in-situ concrete crown beams on top of all precast slabs, and anchor the top ribbed steel bars; after the crown beams meet the design strength requirements, excavate the basement foundation pit from the middle to the surrounding areas until the soil in the middle of the pit reaches the design strength Elevation and only the surrounding slopes remain; cast the basement floor at the bottom of the foundation pit, and reserve bolt holes on the edge of the plate; after the basement floor meets the design strength requirements, fix the steel bracing on the slope on the prefabricated slab and the basement floor;

Step 3: Excavate the remaining soil in the pit below the steel bracing and the cement and soil between the adjacent prefabricated slabs, connect the stressed steel bars of the basement floor and the ribbed steel bars in the middle through the sleeve, and continue to pour the basement floor and put it together. Extend into the groove on the side of the prefabricated board;

Step 4: Connect the stressed steel bar and the side ribbed steel bar of the connecting plate together through the sleeve, then pour the connecting plate between all the prefabricated plates from bottom to top, and finally pour the basement roof;

Step 5: After the strength of the basement roof reaches the design strength, remove the steel bracing to complete the basement construction.

Compared with the prior art, the beneficial effects of the present invention are:

(1) Part of the enclosure structure can be used as the main structure of the basement, and the other part can be recycled, so the project cost is low. The conventional enclosure structure is less recycled, and is buried in the soil when the foundation pit is backfilled, while the prefabricated panel of the present invention can be used as the structural outer wall of the basement, the earthwork of the foundation pit does not need to be backfilled, and the steel diagonal bracing can be recycled, so it has The advantage of low cost.

(2) The construction period is short and the quality is controllable. The conventional foundation pit enclosure structure adopts cast-in-place concrete, while the prestressed prefabricated slabs in the foundation pit enclosure structure of the present invention are prefabricated in the factory, with controllable quality, and are transported to the construction site and directly inserted into the three-axis mixing piles, saving concrete maintenance. The construction period is convenient for earthwork excavation. At the same time, the steel diagonal bracing adopts the assembled installation method, which further saves the construction period.

(3) Wide range of application. At present, more than 95% of the basements in the country have 1-2 floors, and the excavation depth of the foundation pit is 5-12 m, which are all applicable to the foundation pit enclosure structure of the present invention.

Description of drawings

Fig. 1 is the schematic diagram of the prefabricated plate inserted into the three-axis cement-soil mixing pile;

Figure 2 is a schematic diagram of the prefabricated panel facade and side;

Fig. 3 is the schematic diagram of the top view of the connecting plate;

Fig. 4 is the schematic diagram of connecting plate elevation;

Figure 5 shows the construction steps of the enclosure structure.

In the picture: 1. Soil in foundation pit; 2. Prefabricated slab; 3. Ribbed steel bar on top; 4. Triaxial cement-soil mixing pile; 5. Crown beam; 6. Steel diagonal brace; 7. Basement floor; 8. Basement Top plate; 9, connecting plate; 10, side groove; 11, bolt hole; 12, middle groove; 13, side ribbed steel bar; 14, middle ribbed steel bar.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

This embodiment provides a foundation pit enclosure structure based on prefabricated slabs and diagonal braces as shown in Figures 1-5. The foundation pit enclosure structure includes a prefabricated slab 2, a triaxial cement-soil mixing pile 4, a crown beam 5, Steel diagonal brace 6, connecting plate 9. The prefabricated plate 2 is inserted into the triaxial cement-soil mixing pile 4 . The crown beam 5 is cast-in-place anchored on the prefabricated plate 2 , and the top ribbed steel bar 3 is embedded in the crown beam 5 . The steel bracing 6 is connected with the prefabricated plate 2 by bolts. The steel bracing 6 bolts and connects the prefabricated plate 2 and the basement bottom plate 7 as a whole through the reserved bolt holes 11 . The connecting plate 9 is cast-in-place anchored between two adjacent prefabricated plates 2 . The basement floor 7 extends into the middle groove 12, and the stressed steel bars in the basement floor 7 and the middle ribbed steel bars 14 are connected together by steel sleeves. The connecting plate 9 connects the two adjacent prefabricated plates 2, and the stressed steel bar in the connecting plate 9 and the side ribbed steel bar 13 are connected together by a steel sleeve.

The prefabricated plate 2 is a prestressed reinforced concrete prefabricated component, and bolt holes are reserved on the side of the foundation pit. The length of the prefabricated plate 2 is twice the depth of the proposed foundation pit, and the section size is determined by the design according to the depth of the foundation pit. Two rows of top ribbed steel bars 3 protrude from the top of the prefabricated panel 2, and the length of the steel bars are both 0.3m and the spacing is 0.5m. There are two grooves on the prefabricated plate 2, the depths are both 0.2m, and the two rows of ribbed steel bars extending outward from the inside of the grooves are both 0.1m long and 0.2m apart. One of the grooves is symmetrically arranged in the direction of the short side of the prefabricated board section along the long side, that is, the side groove 10, and the width of the groove is 1/2 of the width of the prefabricated board. The other groove is arranged at the position of the prefabricated board corresponding to the basement floor, that is, the side groove 12 , and the width of the groove is the same as the designed width of the basement floor 7 .

The triaxial cement-soil mixing pile 4 is used for reinforcing the soil body at the edge of the pit and waterproofing and water-stopping, and the width is 1.5 times the width of the prefabricated plate 2 . Before the initial setting of the three-axis cement-soil mixing pile 4, insert the prefabricated board 2, and then carry out earthwork excavation after the final setting.

The crown beam 5 is on top of the prefabricated slab 2 and is a cast-in-place reinforced concrete structure. The height of the crown beam 5 is 0.5m, and the width exceeds 1/3 of the width of the prefabricated plate 2 . In order to connect all the prefabricated slabs 2 as a whole, the ribbed steel bars 3 at the top of the prefabricated slabs 2 need to be anchored into the crown beam 5 during construction.

The steel diagonal brace 6 serves to support the prefabricated panel 2 and reduce its horizontal deformation. The cross-section of the steel diagonal brace 6 is circular, with a diameter of 0.3-0.6m and a spacing of 2-4m. Both ends of the steel diagonal brace 6 are bolted to the prefabricated plate 2 and the basement floor 7 respectively.

The connecting plate 9 is a cast-in-place reinforced concrete structure, and functions to connect two adjacent prefabricated plates 2 . During construction, a steel sleeve is used to mechanically connect the stressed steel bar of the connecting plate 9 and the exposed steel bar of the side groove 10 of the prefabricated plate 2 .

The present embodiment also provides a construction method for a foundation pit enclosure structure based on prefabricated slabs and diagonal braces as shown in Figure 5, comprising the following steps:

Step 1: Excavate the trench of the basement exterior wall, first construct two sections of three-axis cement-soil mixing pile 4, and then use a crane to insert a prefabricated plate 2 into the pile body by its own weight before the initial setting of the pile body, and the cycle is repeated. Until the construction of all the three-axis cement-soil mixing piles 4 and the prefabricated slabs 2 is completed.

Step 2: One-time cast-in-place concrete crown beams 5 on top of all precast slabs 2, anchored into top ribbed steel bars 3. After the crown beam 5 reaches the design strength requirements, the basement foundation pit is excavated from the middle to the surrounding areas until the soil body 1 in the middle of the pit reaches the design elevation and only the surrounding slopes remain. The basement bottom plate 7 is cast in place at the bottom of the foundation pit, and bolt holes 11 are reserved on the edge of the plate. After the basement floor 7 reaches the design strength requirements, bolt the steel diagonal braces 6 on the prefabricated plate 2 and the basement floor 7 on the slope.

Step 3: Excavate the remaining soil 1 in the pit below the steel bracing 6 and the cement and soil between the adjacent prefabricated slabs 2, connect the stressed steel bars of the basement floor 7 and the middle ribbed steel bars 14 through the sleeve, and continue to pour The basement floor 7 is extended into the groove 10 on the side of the prefabricated board 2 .

Step 4: Connect the stressed steel bar of the connecting plate 9 and the side ribbed steel bar 13 together through the sleeve, then pour the connecting plate 9 between all the prefabricated plates 2 from bottom to top, and finally pour the basement roof 8.

Step 5: After the strength of the basement roof 8 reaches the design strength, remove the steel diagonal bracing 6 to complete the basement construction.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. a foundation pit enclosure structure based on prefabricated slabs and diagonal braces, characterized in that, comprising prefabricated slabs (2), triaxial cement-soil mixing piles (4), crown beams (5), steel diagonal braces (6) , a connecting plate (9), the prefabricated plate (2) is inserted into the triaxial cement-soil mixing pile (4), the crown beam (5) is cast-in-place anchored on the prefabricated plate (2), and the connecting plate ( 9) Cast-in-place anchoring between two adjacent prefabricated plates (2), the bottom of the foundation pit is provided with a basement bottom plate (7), the top of the foundation pit is provided with a basement top plate (8), and the steel diagonal brace ( 6) It is inclined in the foundation pit, its upper end is fixedly connected with the prefabricated plate (2), and its lower end is fixedly connected with the basement bottom plate (7), and the connecting plate (9) is provided with a side groove (10) and a central recess. The groove (12), the side grooves (10) are symmetrically arranged in the direction of the short side along the long side of the cross section of the prefabricated plate (2), and the middle groove (12) is arranged in the prefabricated plate (2) corresponding to the basement bottom plate (7) ), the basement floor (7) extends and is connected to the middle groove (12), and the connecting plate (9) is fixedly connected to the side groove (10). 2. A foundation pit enclosure structure based on prefabricated slabs and diagonal braces according to claim 1, wherein the prefabricated slab (2) is a prestressed reinforced concrete prefabricated member, which is prefabricated towards the side of the foundation pit. Leave the bolt holes. 3. A kind of foundation pit enclosure structure based on prefabricated panels and diagonal braces according to claim 1, wherein the length of the prefabricated panel (2) is twice the depth of the foundation pit, and the prefabricated panel (2) The top ribbed steel bar (3) protrudes from the top, the top ribbed steel bar (3) is embedded in the crown beam (5), and the side rib is protruded from the inner side of the side groove (10) to the outside. Rebar (13), the width of the side groove (10) is 1/2 of the width of the prefabricated plate, the inner side of the middle groove (12) is protruded with a middle ribbed steel bar (14), and the middle groove ( The width of 12) is the same as the width of the basement floor (7). 4. A foundation pit enclosure structure based on prefabricated slabs and diagonal braces according to claim 3, wherein the length of the top ribbed steel bar (3) is 0.3m, and the spacing is 0.5m. The depths of the side grooves (10) and the middle grooves (12) are both 0.2m, the lengths of the side ribbed steel bars (13) and the middle ribbed steel bars (14) are both 0.1m, and the spacing is 0.2m. 5. A foundation pit enclosure structure based on prefabricated slabs and diagonal braces according to claim 1, wherein the width of the triaxial cement-soil mixing pile (4) is 1.5 times the width of the prefabricated slab (2). times. 6. A foundation pit enclosure structure based on prefabricated slabs and diagonal braces according to claim 1, wherein the crown beam (5) is arranged on the top of the prefabricated slab (2), and is cast-in-place reinforced concrete Structure, the height of the crown beam (5) is 0.5m, and the width exceeds 1/3 of the width of the prefabricated plate (2). 7. A foundation pit enclosure structure based on prefabricated slabs and diagonal braces according to claim 1, wherein the steel diagonal braces (6) are supporting prefabricated slabs, the cross section is circular, and the diameter is 0.3 ～0.6m, spacing 2～4m. 8. A foundation pit enclosure structure based on prefabricated slabs and diagonal braces according to claim 1, wherein the connecting slab (9) is a cast-in-place reinforced concrete structure for connecting two adjacent prefabricated slabs A plate (2), the connecting plate (9) is provided with a stressed steel bar, and the stressed steel bar of the connecting plate (9) and the side ribbed steel bar (13) are mechanically connected through a steel bar sleeve. 9. a construction method based on the foundation pit enclosure structure of prefabricated panels and diagonal braces, is characterized in that, comprises: Step 1: Excavate the trench of the basement exterior wall, first construct two sections of three-axis cement-soil mixing piles (4), and then insert a prefabricated plate (2) into the pile body by its own weight before the initial setting of the pile body, and the cycle is repeated. , until the construction of all three-axis cement-soil mixing piles (4) and prefabricated slabs (2) is completed; Step 2: Cast-in-place concrete crown beams (5) on top of all prefabricated slabs (2) are anchored into the top ribbed steel bars (3). Dig the basement foundation pit until the soil (1) in the middle of the pit reaches the design elevation and only the surrounding slopes remain; cast the basement floor (7) at the bottom of the foundation pit, and reserve bolt holes (11) on the edge of the plate; wait for the basement floor (7) After reaching the design strength requirement, the steel diagonal brace (6) is fixedly installed on the prefabricated plate (2) and the basement floor (7) on the slope; Step 3: Excavate the remaining soil (1) in the pit below the steel diagonal brace (6) and the cement and soil between the adjacent prefabricated slabs (2), and connect the stressed steel bars of the basement floor (7) and the middle ribbed steel bars (14). ) are connected together by the sleeve, continue to pour the basement floor (7), and extend it into the side groove (10) of the prefabricated plate (2); Step 4: Connect the stressed steel bars (9) and the side ribbed steel bars (13) of the connecting plate (9) together through a sleeve, then pour the connecting plates (9) between all the prefabricated plates (2) from bottom to top, and finally Pouring the basement roof (8); Step 5: After the strength of the basement roof (8) reaches the design strength, the steel diagonal braces (6) are removed to complete the basement construction.

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