A support structure without support for deep foundation pit in soft soil area

Abstract

The utility model discloses a kind of no-support type supporting structure for soft soil area deep foundation pit, including front row pile, rear row pile, upper tie beam, lower tie beam and composite inclined pile, front row pile, rear row pile are connected with upper tie beam and lower tie beam by reinforcing connecting component, composite inclined pile is connected with upper tie beam or lower tie beam by energy-absorbing component.The utility model adopts double-row pile, double-layer tie beam and composite inclined pile combination, forms a kind of no-support type supporting structure for soft soil area deep foundation pit, can replace internal support in certain foundation pit depth range, reduce foundation pit deformation, improve structural stability, solve the problem of construction inconvenience brought by existing internal support support;Rear row pile and composite inclined pile are fixedly connected, rear row pile top is subjected to the pull together effect of composite inclined pile, can replace the constraint effect of internal support to pile top displacement, simultaneously, the bulk layer in composite inclined pile can diffuse randomly to reach the effect of reinforcing soft soil, greatly improve the lateral support rigidity of overall structure.

Description

Technical Field

[0001] This utility model pertains to support structures, specifically a supportless support structure for deep foundation pits in soft soil areas. Background Technology

[0002] With the accelerating development and utilization of underground space, the number of foundation pit projects is increasing rapidly. Limited by factors such as large-area deep foundation pit excavation and complex surrounding environmental conditions, foundation pit support technology faces increasingly severe challenges. The requirement prohibiting anchor cables (anchor rods) from exceeding the land use boundary line has significantly restricted the application of traditional support methods such as anchor piles and anchor retaining walls. Traditional support systems are gradually revealing limitations in terms of energy conservation, environmental protection, site adaptability, and engineering applicability, necessitating the development of greener, more efficient, and intelligent new support technologies to meet the development needs of modern urban underground engineering.

[0003] Soft soil is loose and has low strength and stiffness. In areas with unique geological conditions, construction quality issues during excavation can lead to significant pit displacement, causing instability in the support and reinforcement system, resulting in quality problems or even major quality and safety accidents. Excavations in soft soil areas typically require a retaining structure with one or more horizontal internal braces or anchor bolts to limit pit deformation and ensure stability. While the internal bracing technology commonly used in soft soil areas provides stable support stiffness, its placement within the excavation space introduces numerous inconveniences to soil excavation and underground structure construction. The high difficulty, long construction period, and high cost of internal bracing limit its application. Utility Model Content

[0004] Purpose of the utility model: In order to overcome the shortcomings of the existing technology, the purpose of this utility model is to provide a simple and effective unsupported support structure for deep foundation pits in soft soil areas that ensures high support rigidity.

[0005] Technical solution: The present invention provides a support structure for deep foundation pits in soft soil areas without bracing, comprising a front row of piles, a rear row of piles, an upper connecting beam, a lower connecting beam, and composite inclined piles. The front row of piles and the rear row of piles are connected to the upper and lower connecting beams through reinforcing connecting components, and the composite inclined piles are connected to the upper or lower connecting beams through energy-absorbing components.

[0006] Furthermore, the composite inclined pile includes a precast pile and a granular layer, with the granular layer placed on the surface of the precast pile.

[0007] Furthermore, the inclination angle of the composite inclined pile is 10°~30°.

[0008] Furthermore, the center-to-center distance between the rear row of piles and the composite inclined piles connected to the lower connecting beam is 1.2~1.5m. The composite inclined piles and the rear row of piles form a triangular stable structure through the lower connecting beam. During excavation, the inclined piles provide upward resistance, while the upper or lower connecting beam provides horizontal resistance, working together to resist deformation. The composite inclined piles and the rear row of piles are fixedly connected.

[0009] Furthermore, the diameter of the front row of piles is greater than or equal to the diameter of the rear row of piles, and the spacing between the front row of piles is 1 to 2 times the diameter of the rear row of piles.

[0010] Furthermore, the reinforcing connecting component is a clamp, which connects the front row of piles to the upper and lower connecting beams to form a pile support structure.

[0011] Furthermore, a rubber friction-reducing layer is provided on the inner side of the clamp.

[0012] Furthermore, the energy-absorbing component is an aluminum honeycomb core with negative Poisson's ratio. Under external loads, the energy-absorbing component dissipates energy through lateral contraction, effectively alleviating stress concentration in the rear piles and composite inclined piles, and improving the overall seismic performance of the structure. Because the rear piles of the energy-absorbing component are movable, while the overall structure is rigid, slight deformation occurs. The composite inclined piles and the rear piles combine to form a straight-inclined composite pile, increasing pull-out resistance, thereby improving structural stability and reducing overall deformation of the foundation pit.

[0013] Furthermore, one end of the energy-absorbing component is welded to the end of the composite inclined pile, and the other end is hinged to the upper or lower connecting beam via a pin, enabling axial displacement within a range of ±5 mm.

[0014] Furthermore, the wall thickness of the energy-absorbing component is 20~25 mm.

[0015] Working Principle: The inclined piles and the rear row of piles form a triangular stable structure through the lower connecting beam. During excavation, the inclined piles provide upward resistance, while the upper or lower connecting beam provides horizontal resistance, working together to resist deformation. The composite inclined piles and the rear row of piles are fixedly connected, with clamps installed at the top of the piles. These clamps connect the front row of piles to the upper and lower connecting beams, forming a pile support structure. Under external loads, the energy-absorbing components dissipate energy through lateral contraction, effectively alleviating stress concentration in the rear row of piles and the composite inclined piles, thus improving the overall seismic performance of the structure. The rear row of piles can move due to the energy-absorbing components, while the overall structure remains rigid, resulting in slight deformation. The combination of inclined piles and the rear row of piles creates a straight-inclined composite pile structure, increasing pull-out resistance and thereby improving structural stability and reducing overall deformation of the foundation pit.

[0016] Construction method:

[0017] Step 1: Level the site and mark the axial positions of the front row of piles, the rear row of piles, the composite inclined piles, and the upper and lower connecting beams.

[0018] Step 2, Construction of composite inclined piles: After drilling and jet grouting, precast piles are inserted to allow cement mortar to spread outwards, reinforcing the surrounding soft soil and forming a loose layer;

[0019] Step 3: After the composite inclined piles are formed, construct the front row of piles and the rear row of piles. Before the concrete has initially set, construct the upper connecting beam located on the top of the piles. At the same time, use an energy-absorbing structure to fix the rear row of piles, the upper connecting beam and the composite inclined piles.

[0020] Step 4: Excavate the soil in the pit, and at the same time excavate the soil between the front row of piles and the rear row of piles, and above the lower connecting beam, and then construct the lower connecting beam.

[0021] Step 5: Continue excavating to the bottom of the pit.

[0022] Beneficial effects: Compared with the prior art, this utility model has the following significant features:

[0023] 1. By adopting a combination of double-row piles, double-layer connecting beams and composite inclined piles, a support structure without bracing is formed that can be used for deep foundation pits in soft soil areas. The foundation pit depth is generally ≤6~8m. Under good geological conditions, it can replace internal bracing, reduce foundation pit deformation, improve structural stability, and solve the problem of construction inconvenience caused by existing internal bracing.

[0024] 2. The rear row of piles is fixedly connected to the composite inclined piles. The top of the rear row of piles is tied by the composite inclined piles, which can replace the constraint of the internal support on the displacement of the pile top. At the same time, the loose layer in the composite inclined piles can randomly spread to achieve the effect of reinforcing soft soil, which greatly improves the lateral support stiffness of the overall structure.

[0025] 3. The rear piles and the front piles are allowed to have relative displacement. When the water and soil pressure outside the pit acts on the support structure and causes it to deform, the energy-absorbing components that connect the rear piles and the composite inclined piles can make the rear piles deform relative to the front piles to achieve the energy absorption effect, thereby reducing the amount of deformation of the front piles and ensuring the safety of the foundation pit construction. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of this utility model;

[0027] Figure 2 This is a schematic diagram showing the connection between the rear row of piles 2 and the composite inclined piles 5 of this utility model;

[0028] Figure 3 This is a connection diagram of the practical reinforcing connection component 6;

[0029] Figure 4 This is a connection diagram of the energy-absorbing component 7 of this utility model;

[0030] Figure 5 This is a top view of the composite inclined pile 5 of this utility model. Detailed Implementation

[0031] like Figure 1 In the unsupported retaining structure for deep foundation pits in soft soil areas, the upper connecting beam 3 is located at the top of the front row of piles 3 and the rear row of piles 4, and the lower connecting beam 4 is located below the upper connecting beam. The composite inclined piles 5 are fixedly connected to the rear row of piles 2 through the reinforcing connecting member 6. The energy-absorbing member 7 is located between the upper connecting beam 3, the lower connecting beam 4, and the rear row of piles 2. The front row of piles 1 and the rear row of piles 2 are preferably bored cast-in-place piles. The pile diameter and pile spacing of the front row of piles 1 should not be less than those of the rear row of piles 2. The pile spacing of the front row of piles 1 and the rear row of piles 2 should be determined according to the excavation depth of the foundation pit, and should not be greater than twice the pile diameter of the rear row of piles 2. The upper connecting beam 3 and the lower connecting beam 4 are fixedly connected to the front row of piles 1. The reinforcing connecting member 6 is a clamp, which is used to press and fix the rear row of piles 2 and the composite inclined piles 5 to the upper connecting beam 3 and the lower connecting beam 4 through two bolts. The clamp is lined with a 3mm rubber friction-reducing layer. The composite inclined pile 5 consists of a precast pile 51 and a granular layer 52 with an inclination angle of 10°~30°. The granular layer 52 is made of cement mortar spreading outward. The center distance between the composite inclined pile 5, which is connected to the lower connecting beam 4, and the rear pile 2 is 1.2~1.5m.

[0032] like Figures 2-3 The composite inclined piles 5 and the rear row of piles 2 form a triangular stable structure through the upper connecting beam 3 and the lower connecting beam 4. During excavation, the two parallel composite inclined piles 5 provide upward resistance, while the composite inclined piles 5 and the rear row of piles 2 (straight piles) provide horizontal resistance, working together to limit the deformation of the foundation pit. Simultaneously, the loose layer 52 in the composite inclined piles 5 can randomly diffuse to reinforce soft soil, greatly improving the lateral support stiffness of the overall structure. The composite inclined piles 5 and the rear row of piles 2 are fixedly connected using reinforcing connecting components 6. Similarly, clamps are installed at the top of the piles, connecting the rear row of piles 2 to the upper connecting beam 3 and the lower connecting beam 4 to form a pile support structure. Each clamp has four bolts, and the front row of piles 1, the rear row of piles 2, the upper connecting beam 3, and the lower connecting beam 4 are connected and fixed by tightening the clamps with bolts.

[0033] like Figure 4 The energy-absorbing component 7 is made of a negative Poisson's ratio alloy material (such as aluminum honeycomb core) with a wall thickness of 20-25 mm. One end of this component is welded to the end of the composite inclined pile 5, and the other end is hinged to the upper connecting beam 3 or the lower connecting beam 4 via a pin, enabling axial displacement within a range of ±5 mm. Under external loads, it dissipates energy through lateral contraction, alleviating stress concentration and improving seismic performance. The rear pile 2 and the front pile 1 are allowed to have relative displacement. When the water and soil pressure outside the pit acts on the support structure and causes it to deform, the component connecting the rear pile 2 and the composite inclined pile 5 allows the rear pile 2 to deform relative to the front pile, achieving an energy-absorbing effect. This, in turn, reduces the deformation of the front pile 1, ensuring the safety of the foundation pit construction.

[0034] like Figure 5The precast piles 51 provide high compressive, flexural, and shear strength, bearing the main loads. The granular layer 52 can randomly diffuse to reinforce soft soil. By solidifying the surrounding soft soil, it increases the effective diameter of the piles, improves side friction and end bearing capacity, and greatly enhances the lateral support stiffness of the overall structure. This combination significantly improves the overall bearing capacity of the piles and is suitable for high-load requirements in soft soil areas.

[0035] The construction method of the unsupported retaining structure for deep foundation pits in soft soil areas in this embodiment includes the following steps:

[0036] Step 1: Level the site and mark the axial positions of the front row of piles 1, the rear row of piles 2, the two composite inclined piles 5, the upper connecting beam 3, and the lower connecting beam 4.

[0037] Step 2: Construct composite inclined pile 5, drill and jet grout, insert precast pile 51, so that cement mortar spreads outward, reinforces the surrounding soft soil, and forms a loose layer 52.

[0038] Step 3: After the composite inclined pile 5 is formed, construct the front row of piles 1 and the rear row of piles 2. Before the concrete initially sets, construct the upper connecting beam 3 located at the top of the piles. At the same time, use the energy-absorbing component 7 with a negative Poisson's ratio structure to fix the rear row of piles 2, the upper connecting beam 3, the lower connecting beam 4 and the composite inclined pile 5.

[0039] Step 4: Excavate the soil in the pit, and at the same time excavate the soil between the front row of piles 1 and the rear row of piles 2, above the lower connecting beam 4, and then construct the lower connecting beam 4.

[0040] Step 5: Continue excavating to the bottom of the pit.

Claims

1. A support structure without bracing for deep foundation pits in soft soil areas, characterized in that: It includes a front row of piles (1), a rear row of piles (2), an upper connecting beam (3), a lower connecting beam (4), and a composite inclined pile (5). The front row of piles (1) and the rear row of piles (2) are connected to the upper connecting beam (3) and the lower connecting beam (4) through a reinforcing connecting member (6). The composite inclined pile (5) is connected to the upper connecting beam (3) or the lower connecting beam (4) through an energy-absorbing member (7).

2. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: The composite inclined pile (5) includes a precast pile (51) and a granular layer (52), wherein the granular layer (52) is disposed on the surface of the precast pile (51).

3. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: The inclination angle of the composite inclined pile (5) is 10°~30°.

4. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: The center distance between the rear piles (2) and the composite inclined piles (5) connected to the lower connecting beam (4) is 1.2~1.5m.

5. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: The diameter of the front row of piles (1) is greater than or equal to the diameter of the rear row of piles (2), and the spacing between the front row of piles (1) is 1 to 2 times the diameter of the rear row of piles (2).

6. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: The reinforcing connection component (6) is a clamp.

7. The unsupported support structure for deep foundation pits in soft soil areas according to claim 6, characterized in that: A rubber friction-reducing layer is provided on the inner side of the clamp.

8. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: The energy-absorbing component (7) is an aluminum honeycomb core with negative Poisson bit properties.

9. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: One end of the energy-absorbing component (7) is welded to the end of the composite inclined pile (5), and the other end is hinged to the upper connecting beam (3) or the lower connecting beam (4) through a pin.

10. The unsupported support structure for deep foundation pits in soft soil areas according to claim 1, characterized in that: The wall thickness of the energy-absorbing component (7) is 20~25 mm.

Images