A deep foundation pit support structure on a slope and its construction method

Abstract

This invention discloses a deep foundation pit support structure on a slope, comprising: a vertically arranged transverse cast-in-place pile group; longitudinal cast-in-place pile groups at both ends of the transverse cast-in-place pile group near the bottom of the slope; two longitudinal cast-in-place pile groups perpendicular to the sides of the transverse cast-in-place pile group; both the transverse and longitudinal cast-in-place pile groups consist of several vertically arranged cast-in-place piles; the tops of the transverse cast-in-place pile group and the two longitudinal cast-in-place pile groups are connected to each other by a capping beam; the capping beam has a bracing at one end of its two opposite short sides and the end furthest from its long side; corner braces are provided between the two short sides and the long side of the capping beam; one end of each corner brace is connected to the middle of the short side of the capping beam, and the other end is connected to the long side of the capping beam; the end faces of the two short sides of the capping beam are connected to one end of an end support through a head plate; the other end of the end support cooperates with a support seat set in the slope; the end support has a set inclination angle; and oblique end supports are provided on the capping beam to transmit eccentric loads and maintain the external stability of the foundation pit.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering technology, and specifically relates to a deep foundation pit support structure on a slope and its construction method. Background Technology

[0002] An excavation pit is a pit dug at the foundation design location according to the base elevation and foundation plan dimensions. Before excavation, an excavation plan should be determined based on geological and hydrological data and the condition of nearby buildings, and waterproofing and drainage work should be carried out. For shallow excavations, slope protection can be used to stabilize the soil slope, and the slope should be determined according to relevant construction regulations. For deeper excavations or those near buildings, excavation pit wall support methods, shotcrete wall protection methods, and even methods such as diaphragm walls and interlocking column-type bored piles can be used to prevent the outer soil layer from collapsing. For excavations without the influence of nearby buildings, the wellpoint method can be used to lower the groundwater level, and open excavation with slope protection can be adopted. In cold regions, natural freezing methods can be used for excavation, etc. The most common problem encountered during the excavation of foundation pits is the issue of pit support. Foundation pits are categorized as shallow or deep. Generally, common support methods for shallow pits include anchor bracing, inclined column bracing, continuous vertical bracing, intermittent horizontal bracing, discontinuous horizontal bracing, short column diaphragm bracing, and temporary retaining wall support. Common support methods for deep pits include soil nailing wall support, sheet pile support, cement-soil wall support, pile internal bracing, pile soil anchor support, and retaining wall with grouting or diaphragm wall support. There are various and flexible methods for foundation pit support, and the choice must be made based on specific circumstances. The specific method adopted depends on factors such as the soil quality and groundwater level.

[0003] For example, Chinese invention patent application number 202010264912.5 discloses a foundation pit support system, including a pre-excavated support and protection pit body with a depth, length, and width not less than the planned depth of the foundation pit. The support and protection pit body has an upward-sloping slope on its vertical surface. A bottom waterproof trough is set at the bottom of the slope and the support and protection pit body. A high-strength drainage support device is set on the inner side of the bottom waterproof trough and the slope. This reduces the risk of soil collapse outside the planned area of ​​the foundation pit. It also uses a slope support plate in conjunction with a slope to carry out support work outside the planned area of ​​the foundation pit. This reduces the risk of the support device collapsing due to changes in terrain and geology when carrying out support work according to the original planned area. It is suitable for foundation pit construction work under special geological conditions and for foundation pit support work in such special terrain, which is a dangerous geological area with loose soil and prone to geological disasters.

[0004] However, some projects face land shortages, and some buildings and structures inevitably need to be built on the slopes of factory or station areas. Due to the large excavation depth of some buildings and structures, such as water tanks, oil tanks, and pumping stations, deep foundation pit support is required on the slopes. Using traditional vertical piles on slopes can lead to problems such as insufficient anchorage depth, inability to construct the upper part of the cast-in-place piles, and large eccentric loads on the overall pile structure, resulting in construction difficulties and low slope safety. Summary of the Invention

[0005] This invention provides a deep foundation pit support structure and its construction method on slopes, aiming to solve the problems of insufficient anchorage depth, inability to construct the upper part of the cast-in-place piles, and large eccentric load on the overall pile structure when using traditional vertical piles on slopes, resulting in construction difficulties and low slope safety.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A deep foundation pit support structure on a slope includes: a vertically arranged transverse cast-in-place pile group; longitudinal cast-in-place pile groups are arranged at both ends of the transverse cast-in-place pile group near the bottom of the slope; the two longitudinal cast-in-place pile groups are perpendicular to the sides of the transverse cast-in-place pile group; the length of the longitudinal cast-in-place pile group is less than half that of the transverse cast-in-place pile group; both the transverse and longitudinal cast-in-place pile groups consist of several vertical cast-in-place piles of equal height and spacing; the tops of the transverse cast-in-place pile group and the two longitudinal cast-in-place pile groups are connected to each other by a capping beam; a brace is provided at the two opposite short sides of the capping beam away from the long side; corner braces are provided between the two short sides and the long side of the capping beam; one end of the corner brace is connected to the middle of the short side of the capping beam, and the other end is connected to the long side of the capping beam; the angle between the corner brace and the short side of the capping beam is 45°; the end faces of the two short sides of the capping beam are connected to one end of an end support through a head plate; the other end of the end support cooperates with a support seat set in the slope; the end support has a set inclination angle.

[0008] Furthermore, the angle between the end support and the horizontal plane is 30°-60°.

[0009] Furthermore, the cast-in-place pile further comprises: cylindrical concrete, wherein a plurality of reinforcing cages are arranged inside the cylindrical concrete, the plurality of reinforcing cages are arranged in a circular pattern coaxial with the cylindrical concrete, the inner circle of the plurality of reinforcing cages is provided with spirally distributed dense hoops, the dense hoops extending from the upper end to the lower end of the plurality of reinforcing cages, the outer circle of the plurality of reinforcing cages is provided with a plurality of horizontally spaced reinforcing hoops, the top of the cast-in-place pile extends into the capping beam, and the top of the cast-in-place pile is provided with a plurality of radial connecting reinforcing bars, the connecting reinforcing bars also being located inside the capping beam.

[0010] Furthermore, protective plate assemblies are installed on the side of both the transverse and longitudinal cast-in-place pile groups closest to the foundation pit, and the protective plate assemblies are located at the lower part of the cap beam.

[0011] Furthermore, the protective plate assembly further includes: slab-shaped concrete, wherein a plurality of horizontally spaced protective reinforcing bars are provided inside the slab-shaped concrete, the protective horizontal reinforcing bars are connected to the main reinforcing bars of the adjacent reinforcing cages in the cast-in-place piles that form the transverse cast-in-place pile group or the longitudinal cast-in-place pile group, a plurality of vertically spaced protective vertical reinforcing bars are provided inside the slab-shaped concrete and on the side of the protective horizontal reinforcing bars away from the foundation pit, and a plurality of horizontally spaced protective channel steels are provided on the side wall of the slab-shaped concrete near the foundation pit.

[0012] Furthermore, the support base further includes: a support base plate, a support block is provided on the upper part of the support base plate, and a receiving cavity for accommodating the end support is provided on the support block.

[0013] Furthermore, the support block is provided with several parallel horizontal support bars inside, and several parallel longitudinal support bars are provided below the horizontal support bars. The horizontal support bars and the longitudinal support bars are perpendicular to each other, and both the horizontal support bars and the longitudinal support bars are located below the receiving cavity.

[0014] The present invention also provides a construction method for a deep foundation pit support structure on a slope, comprising the following steps:

[0015] Step 1: First, construct the support base at the toe of the slope;

[0016] Step 2: After the support base construction is completed, proceed with the construction of the transverse and longitudinal cast-in-place pile groups;

[0017] Step 3: After the construction of the transverse and longitudinal cast-in-place pile groups is completed, the cap beam is poured. The cap beam connects all the cast-in-place piles in the transverse and longitudinal cast-in-place pile groups to form a complete pile row.

[0018] During the construction of the cap beam, corner bracing, counter bracing, and end support are constructed.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] 1. The deep foundation pit support structure on the slope described in this invention connects the cast-in-place piles to form a pile row as a whole through a capping beam. The inner side of the capping beam is provided with bracing and corner bracing to maintain the internal stability of the foundation pit. External end supports are provided at the ends of the capping beam. One side of the end support is connected to the capping beam, and the other side is inserted into the inner support seat at the slope toe for support, so as to transfer the eccentric load and maintain the external stability of the foundation pit. This can effectively solve the safety problem of pile row support on the slope.

[0021] 2. The deep foundation pit support structure on the slope described in this invention, by limiting the angle between the end support and the horizontal plane to 30°-60°, can adapt to most slope inclinations and can effectively guide the eccentric load to the support seat through the end support.

[0022] 3. The deep foundation pit support structure on the slope described in this invention improves the overall strength and stiffness of the cast-in-place piles by combining cylindrical concrete and reinforcing cages, making them better able to withstand external loads and tangential forces. The addition of denser hoops and reinforced stirrups effectively controls the shrinkage and expansion of concrete, reduces cracking and deformation, and thus increases the stability of the cast-in-place piles. The radial connecting steel bars facilitate the connection between the cast-in-place piles and the capping beam, improving construction efficiency and quality. Furthermore, the load borne by the cast-in-place piles can be better transferred to the capping beam, and then from the capping beam to the end supports, thereby improving the overall stability of the support structure.

[0023] 4. The deep foundation pit support structure on a slope described in this invention improves the safety of the foundation pit edge area through the installation of protective plate groups. The protective plate groups can effectively prevent soil collapse in the foundation pit edge area, further improving the protection capability of the support structure. The installation of protective horizontal and vertical steel bars can increase the overall strength and stiffness of the protective plate, and improve its bending and shear resistance. The protective plate is installed on the side of the cast-in-place piles close to the foundation pit, thereby enhancing the stability of the cast-in-place pile group. The installation of protective channel steel can also further improve the protection capability of the protective plate group.

[0024] 5. The deep foundation pit support structure on a slope described in this invention improves the load-bearing capacity and stability of the support base through its structural design. The addition of transverse and longitudinal reinforcing bars increases the overall strength and stiffness of the support base, making it better able to withstand external loads, thereby improving its load-bearing capacity and stability. The support base plate increases the contact area between the support base and the ground, thus better transferring the load borne by the support base to the earth and increasing its stability. Furthermore, the support base has accommodating cavities that cooperate with the end supports, which can accommodate different end support inclination angles and ensure the stability of the cooperation between the support base and the end supports. Attached Figure Description

[0025] Figure 1 This is a top view of a deep foundation pit support structure on a slope as described in this invention;

[0026] Figure 2 This is a cross-sectional view of a deep foundation pit support structure on a slope as described in this invention;

[0027] Figure 3 This is a schematic diagram of a cast-in-place pile for a deep foundation pit support structure on a slope, as described in this invention.

[0028] Figure 4 This is a top view of a cast-in-place pile of a deep foundation pit support structure on a slope, as described in this invention.

[0029] Figure 5 This is a schematic diagram of a protective plate assembly for a deep foundation pit support structure on a slope, as described in this invention.

[0030] Figure 6 This is a schematic diagram of a protective plate assembly for a deep foundation pit support structure on a slope, as described in this invention.

[0031] Figure 7 This is a schematic diagram of a protective plate assembly for a deep foundation pit support structure on a slope, as described in this invention.

[0032] Figure 8 This is a schematic diagram of a support base for a deep foundation pit support structure on a slope, as described in this invention.

[0033] Figure 9 This is a schematic diagram of a support base for a deep foundation pit support structure on a slope, as described in this invention.

[0034] In the diagram: 1. Horizontal cast-in-place pile group; 2. Longitudinal cast-in-place pile group; 3. Cap beam; 4. Corner brace; 5. Opposite brace; 6. End support; 7. Support seat; 8. Excavation pit outline; 9. End plate; 10. Slope surface; 101. Cast-in-place pile; 102. Cylindrical concrete; 103. Main reinforcement of the steel cage; 104. Densified stirrups; 105. Reinforcing stirrups; 106. Connecting reinforcement; 107. Protective plate group; 108. Slab concrete; 109. Protective horizontal reinforcement; 110. Protective vertical reinforcement; 111. Protective channel steel; 701. Support base plate; 702. Support block; 703. Supporting horizontal reinforcement; 704. Supporting longitudinal reinforcement; 705. Receiving cavity. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present application and with reference to the accompanying drawings.

[0036] like Figure 1-2As shown, a deep foundation pit support structure on a slope includes: a vertically arranged transverse cast-in-place pile group 1; longitudinal cast-in-place pile groups 2 are arranged at both ends of the transverse cast-in-place pile group 1 near the bottom of the slope; the two longitudinal cast-in-place pile groups 2 are perpendicular to the sides of the transverse cast-in-place pile group 1; the length of the longitudinal cast-in-place pile groups 2 is less than half the length of the transverse cast-in-place pile group 1; both the transverse cast-in-place pile group 1 and the longitudinal cast-in-place pile group 2 are composed of several vertical cast-in-place piles 101 arranged at equal heights and intervals; the tops of the transverse cast-in-place pile group 1 and the two longitudinal cast-in-place pile groups 2 are connected. The crown beams 3 are interconnected. The two short sides of the crown beams 3, away from the long side, are provided with a brace 5. Angle braces 4 are provided between the two short sides and the long side of the crown beams 3. One end of the angle brace 4 is connected to the middle of the short side of the crown beam 3, and the other end is connected to the long side of the crown beam 3. The angle between the angle brace 4 and the short side of the crown beam 3 is 45°. The end faces of the two short sides of the crown beam 3 are connected to one end of the end support 6 through the end plate 9. The other end of the end support 6 is engaged with the support seat 7 set in the slope. The end support 6 has a set inclination angle.

[0037] In the figure, the transverse cast-in-place pile group 1 is located at the high point of the slope 10, the support base 7 is located at the low point of the slope, the foundation pit outline 8 is located inside the area surrounded by the capping beam 3, and the specific construction depth of the cast-in-place pile 101 and the specific dimensions of the transverse cast-in-place pile group 1 and the longitudinal cast-in-place pile group 2 are determined by the construction personnel based on the dimensions of the foundation pit, geological conditions, and the surrounding buildings.

[0038] like Figure 2 As shown, the angle between the end support 6 and the horizontal plane is 30°-60°. The specific end support angle is determined based on the actual slope angle, the size of the foundation pit, geological conditions, and the surrounding buildings.

[0039] like Figure 3-4 As shown, the cast-in-place pile 101 further includes: a cylindrical concrete 102, inside which are arranged a plurality of reinforcing cage main bars 103, the plurality of reinforcing cage main bars 103 being distributed in a circle coaxial with the cylindrical concrete 102, the inner circle of the plurality of reinforcing cage main bars 103 being provided with spirally distributed dense hoops 104, the dense hoops 104 extending from the upper end to the lower end of the plurality of reinforcing cage main bars 103, the outer circle of the plurality of reinforcing cage main bars 103 being provided with a plurality of horizontally spaced reinforcing hoops 105, the top of the cast-in-place pile 101 extending into the capping beam 3, the top of the cast-in-place pile 101 being provided with a plurality of radially arranged connecting bars 106, the connecting bars 106 also being located inside the capping beam 3.

[0040] like Figure 5-6 As shown, both the transverse cast-in-place pile group 1 and the longitudinal cast-in-place pile group 2 are provided with protective plate groups 107 on the side near the foundation pit, and the protective plate groups 107 are located at the lower part of the cap beam 3.

[0041] like Figure 5-7 As shown, the protective plate assembly 107 further includes: a slab-shaped concrete 108, wherein a plurality of horizontally spaced protective horizontal steel bars 109 are provided inside the slab-shaped concrete 108, and the protective horizontal steel bars 109 are connected to the main steel bars 103 of the adjacent steel cage in the cast-in-place piles 101 that form the transverse cast-in-place pile assembly 1 or the longitudinal cast-in-place pile assembly 2; a plurality of vertically spaced protective vertical steel bars 110 are provided inside the slab-shaped concrete 108 and on the side of the protective horizontal steel bars 109 away from the foundation pit; and a plurality of horizontally spaced protective channel steels 111 are provided on the side wall of the slab-shaped concrete 108 near the foundation pit.

[0042] like Figure 8-9 As shown, the support base 7 further includes: a support base plate 701, and a support block 702 is provided on the upper part of the support base plate 701. The support block 702 has a receiving cavity 705 for accommodating the end support 6. The receiving cavity 705 is set according to the specific construction angle of the end support 6, so that it fully fits the lower end of the end support 6, ensuring that the support base 7 can provide effective support for the end support 6.

[0043] like Figure 8-9 As shown, the support block 702 is provided with a plurality of parallel horizontal support bars 703 inside, and a plurality of parallel vertical support bars 704 are provided below the horizontal support bars 703. The horizontal support bars 703 and the vertical support bars 704 are perpendicular to each other, and both the horizontal support bars 703 and the vertical support bars 704 are located below the receiving cavity 705.

[0044] A construction method for a deep foundation pit support structure on a slope includes the following steps:

[0045] Step 1: First, construct the support base 7 at the toe of the slope;

[0046] Step 2: After the support base 7 is constructed, the transverse cast-in-place pile group 1 and the longitudinal cast-in-place pile group 2 will be constructed.

[0047] Step 3: After the construction of the transverse cast-in-place pile group 1 and the longitudinal cast-in-place pile group 2 is completed, the cap beam 3 is poured. The cap beam 3 connects all the cast-in-place piles 101 in the transverse cast-in-place pile group 1 and the longitudinal cast-in-place pile group 2 to form a whole pile row.

[0048] During the construction of the crown beam 3, the corner bracing 4, the counter bracing 5, and the end support 6 are constructed.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A deep foundation pit support structure on a slope, characterized in that, include: A vertically arranged transverse cast-in-place pile group (1) is provided. At both ends of the transverse cast-in-place pile group (1) near the bottom of the slope, longitudinal cast-in-place pile groups (2) are provided. The two longitudinal cast-in-place pile groups (2) are perpendicular to the sides of the transverse cast-in-place pile group (1). The length of the longitudinal cast-in-place pile group (2) is less than half that of the transverse cast-in-place pile group (1). Both the transverse cast-in-place pile group (1) and the longitudinal cast-in-place pile group (2) consist of several vertical cast-in-place piles (101) arranged at equal heights and intervals. The tops of the transverse cast-in-place pile group (1) and the two longitudinal cast-in-place pile groups (2) are connected to each other by a capping beam (3). A brace (5) is provided on the two short sides of the beam (3) and at the end away from the long side. An angle brace (4) is provided between the two short sides and the long side of the crown beam (3). One end of the angle brace (4) is connected to the middle of the short side of the crown beam (3), and the other end is connected to the long side of the crown beam (3). The angle between the angle brace (4) and the short side of the crown beam (3) is 45°. The end faces of the two short sides of the crown beam (3) are connected to one end of the end support (6) through the end plate (9). The other end of the end support (6) is engaged with the support seat (7) set in the slope. The end support (6) has a set inclination angle.

2. The deep foundation pit support structure on a slope according to claim 1, characterized in that, The angle between the end support (6) and the horizontal plane is 30°-60°.

3. The deep foundation pit support structure on a slope according to claim 2, characterized in that, The cast-in-place pile (101) further includes: a cylindrical concrete (102), the cylindrical concrete (102) having a plurality of main reinforcing bars (103) inside, the plurality of main reinforcing bars (103) being distributed in a circular pattern coaxial with the cylindrical concrete (102), the inner circle of the plurality of main reinforcing bars (103) being provided with spirally distributed reinforced hoops (104), the reinforced hoops (104) extending from the upper end to the lower end of the plurality of main reinforcing bars (103), the outer circle of the plurality of main reinforcing bars (103) being provided with a plurality of horizontally spaced reinforcing hoops (105), the top of the cast-in-place pile (101) extending into the capping beam (3), the top of the cast-in-place pile (101) being provided with a plurality of radially arranged connecting reinforcing bars (106), the connecting reinforcing bars (106) also being located inside the capping beam (3).

4. The deep foundation pit support structure on a slope according to claim 3, characterized in that, Both the transverse cast-in-place pile group (1) and the longitudinal cast-in-place pile group (2) are equipped with protective plate groups (107) on the side near the foundation pit, and the protective plate groups (107) are located at the lower part of the cap beam (3).

5. A deep foundation pit support structure on a slope according to claim 4, characterized in that, The protective plate assembly (107) further includes: a slab-shaped concrete (108), wherein a plurality of horizontally equally spaced protective horizontal steel bars (109) are provided inside the slab-shaped concrete (108), the protective horizontal steel bars (109) are connected to the main reinforcing bars (103) of the adjacent steel cage in the cast-in-place piles (101) that form the transverse cast-in-place pile assembly (1) or the longitudinal cast-in-place pile assembly (2), wherein a plurality of vertically equally spaced protective vertical steel bars (110) are provided inside the slab-shaped concrete (108) and on the side of the protective horizontal steel bars (109) away from the foundation pit, and a plurality of horizontally equally spaced protective channel steels (111) are provided on the side wall of the slab-shaped concrete (108) near the foundation pit.

6. A deep foundation pit support structure on a slope according to claim 5, characterized in that, The support base (7) further includes: a support base plate (701), a support block (702) is provided on the upper part of the support base plate (701), and a receiving cavity (705) for accommodating the end support (6) is provided on the support block (702).

7. A deep foundation pit support structure on a slope according to claim 6, characterized in that, The support block (702) is provided with a number of parallel horizontal support bars (703) inside. The lower part of the horizontal support bars (703) is provided with a number of parallel vertical support bars (704). The horizontal support bars (703) and the vertical support bars (704) are perpendicular to each other. Both the horizontal support bars (703) and the vertical support bars (704) are located below the receiving cavity (705).

8. A construction method for a deep foundation pit support structure on a slope as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: First, construct the support base (7) at the toe of the slope; Step 2: After the support base (7) is completed, the transverse cast-in-place pile group (1) and the longitudinal cast-in-place pile group (2) are constructed. Step 3: After the construction of the transverse cast-in-place pile group (1) and the longitudinal cast-in-place pile group (2) is completed, the cap beam (3) is poured. The cap beam (3) connects all the cast-in-place piles (101) in the transverse cast-in-place pile group (1) and the longitudinal cast-in-place pile group (2) to form a whole pile row. During the construction of the crown beam (3), corner bracing (4), counter bracing (5) and end support (6) are carried out.

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