Pit precast ring beam step open caisson type supporting structure and method in water-rich sand pit

Abstract

The application discloses a kind of water-rich sand layer pit pit prefabricated ring beam step caisson type supporting structure and method, supporting structure includes: multilayer prefabricated ring beam, interval setting and with the excavation slope of pit pit from base edge to upper edge of edge step type distribution, pre-embedded drainage pipe is embedded in each prefabricated ring beam;Multilayer structure, with the excavation slope of pit pit from base edge to upper edge of edge step type distribution and respectively connected between each adjacent two layers of prefabricated ring beam, multilayer structure and multilayer prefabricated ring beam are connected into step structure supported at pit pit slope, each layer of structure includes filter layer, water-resisting layer, cushion, which are sequentially arranged from bottom to top, and both ends of each pre-embedded drainage pipe are communicated with two filter layers in adjacent two layers of structure, to realize water in water-rich sand layer layer-by-layer flow guide, the application solves the problem that water-rich sand layer local deep pit slope collapses with excavation, realizes supporting with excavation, simultaneously realizes synchronous hidden drainage of groundwater in water-rich sand layer, and has high popularization value.

Description

Technical Field

[0001] This invention relates to the field of foundation pit construction technology, and in particular to a precast ring beam stepped caisson support structure and method for a pit in a water-rich sand layer. Background Technology

[0002] The main characteristics of water-rich sandy soil layers are that they cannot form stable slopes, and they collapse as they are excavated. In addition, the sand layer has high permeability, large groundwater flow, and long drainage cycle. In foundation pit projects with the foundation in water-rich sandy soil layers, pits within pits such as sump pits, elevator pits, and column piers are usually excavated with slopes, which leads to slope collapse and difficulty in dewatering. Traditional slope spraying cannot form a solid slope, resulting in delays in construction progress and safety hazards. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a precast ring beam stepped caisson support structure and method for pit-within-pit in water-rich sand layers. This structure enables simultaneous excavation and support of pit-within-pit in water-rich sand layers, ensuring that local deep pits in saturated sand layers do not collapse during excavation, while also allowing for the underground drainage of groundwater.

[0004] To achieve the above objectives, the present invention provides a precast ring beam stepped caisson support structure for pits in water-rich sand layers, comprising:

[0005] Multi-layer precast ring beams are spaced apart and distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-within-pit. Each layer of the precast ring beams is pre-embedded with a drainage pipe.

[0006] The multi-layered structural section is distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-within-a-pit and is connected between each two adjacent layers of precast ring beams. The multi-layered structural section and the multi-layered precast ring beams are connected together to form a stepped structure supporting the slope of the pit-within-a-pit. Each layer of the structural section includes a filter layer, a water-proof layer and a cushion layer arranged sequentially from bottom to top. The two ends of each pre-embedded drainage pipe are respectively connected to the two filter layers in the two adjacent layers of the structural section to realize the layer-by-layer diversion of water in the water-rich sand layer.

[0007] Preferably, each of the two ends of the pre-buried drainage pipe is provided with a filter screen at the connection point between the pipe and the corresponding filter layer.

[0008] Preferably, each layer of the precast ring beam is provided with a cutting edge at the bottom.

[0009] Preferably, the support structure further includes a foundation plate covering the surface of the stepped structure and forming the pit-in-pit sidewall, and a concrete layer filling the space between the foundation plate and the stepped structure.

[0010] A method for constructing a precast ring beam stepped caisson support structure for a pit in a water-rich sand layer, the method comprising the following construction steps:

[0011] Multi-layer precast ring beams are constructed, with pre-embedded drainage pipes embedded in each layer of the precast ring beams.

[0012] The pit-within-a-pit is excavated in the water-rich sand layer, and the precast ring beams are installed layer by layer at the corresponding positions during the excavation process until the base design elevation of the pit-within-a-pit is reached. The multi-layer precast ring beams are set at intervals and are distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-within-a-pit.

[0013] Multi-layer structural units are constructed between each pair of adjacent precast ring beams, so that the multi-layer structural units are distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-in-pit. The multi-layer structural units and the multi-layer precast ring beams are connected together to form a stepped structure supporting the slope of the pit-in-pit. Each layer of structural unit includes a filter layer, a water-proof layer, and a cushion layer arranged sequentially from bottom to top. Both ends of each pre-embedded drainage pipe are connected to the two filter layers in the two adjacent structural units, so as to realize the layer-by-layer diversion of water in the water-rich sand layer.

[0014] By adopting the above technical solution, the present invention has the following beneficial effects:

[0015] By setting up precast ring beams, the precast ring beams are installed in a stepped manner from the bottom edge to the top edge of the pit, which is consistent with the excavation slope of the pit. This allows for support during excavation and solves the problem of local deep pit slopes collapsing during excavation in water-rich sand layers. By setting up pre-embedded drainage pipes in the precast ring beams, the groundwater in the water-rich sand layers can be discharged synchronously, ensuring the rapid construction of the cushion layer and waterproof layer. The bottom of the precast ring beams is equipped with a cutting edge, which facilitates caisson construction. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a plan view of the precast ring beam stepped caisson support structure in the water-rich sand layer pit in this embodiment of the invention.

[0018] Figure 2 This is a cross-sectional view of the precast ring beam stepped caisson support structure in the water-rich sand layer pit in this embodiment of the invention.

[0019] Figure 3 yes Figure 2 Enlarged view of the structure at point A in the middle.

[0020] Figure 4 This is a schematic cross-sectional view of the prefabricated ring beam in an embodiment of the present invention.

[0021] Figure 5 This is a detailed drawing of the reinforcement of the precast ring beam in an embodiment of the present invention.

[0022] The correspondence between the numbers in the attached diagram is as follows:

[0023] 1- Pit within a pit; 2- Dewatering well; 3- Drainage hose; 4- Precast ring beam; 41- Reinforcing steel; 42- Embedded drainage pipe; 43- Cutting edge; 5- Structural part; 51- Subbase; 52- Waterproof layer; 53- Filter layer; 6- Concrete layer; 7- Filter screen; 8- Water-rich sand layer. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions of embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below...

[0025] Please see Figures 1 to 5As shown, this embodiment of the invention provides a precast ring beam stepped caisson support structure for a pit within a pit in a water-rich sand layer. The pit within a pit 1 is formed within a water-rich sand layer 8. The support structure includes multiple layers of precast ring beams 4 and multiple layers of structural parts 5. The multiple layers of precast ring beams 4 are spaced apart and distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit within a pit 1. Each layer of precast ring beams 4 has a pre-embedded drainage pipe 42. The multiple layers of structural parts are distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit within a pit 1 and are respectively connected between each two adjacent layers of precast ring beams 4. The multiple layers of structural parts 5 and the multiple layers of precast ring beams 4 are connected together to form a stepped structure supporting the slope of the pit within a pit 1. Each layer of structural parts 5 includes a filter layer 53, a water-proof layer 52, and a cushion layer 51 arranged sequentially from bottom to top. The two ends of each pre-embedded drainage pipe 42 are respectively connected to the two filter layers 53 in the two adjacent layers of structural parts 5 to realize the layer-by-layer diversion of water in the water-rich sand layer 8. It should be noted that in this embodiment, the precast ring beam 4 is made of steel bars 41 and precast concrete, with a cross-sectional dimension of 200 mm × 650 mm (width × height). Each layer of precast ring beam 4 has a cutting edge 43 at the bottom, with a bottom opening width of 100 mm and an angle of 63° to facilitate caisson construction. The steel bars 41 are divided into horizontal bars, stirrups and hooks. The horizontal bars are arranged using C14@200, and the stirrups and hooks are arranged using A6@200. Then, C25 concrete is poured to precast the beam. Multiple embedded drainage pipes 42 are evenly arranged inside each layer of precast ring beam 4. The embedded drainage pipes 42 are made of A50 PVC pipes and are Z-shaped. The filter layer 53 is a crushed stone filter layer with a thickness of 100 mm. The waterproof layer 52 is laid with PE film. The cushion layer 51 is 50 mm thick C15 concrete.

[0026] Furthermore, in this embodiment, each pre-buried drainage pipe 42 is provided with a filter screen 7 at the connection between its two ends and the corresponding filter layer 53.

[0027] Furthermore, the support structure also includes a foundation slab that covers the surface of the stepped structure and forms the sidewall of the pit-in-pit 1, and a concrete layer 6 that fills the space between the foundation slab and the stepped structure.

[0028] It should be noted that, in this embodiment, the pit within the pit 1 is a water collection pit formed in the foundation pit of the water-rich sand layer. The water collection pit is equipped with a dewatering well 2, and the dewatering well 2 is equipped with a drainage hose 3 that connects to the upper edge of the water collection pit. The construction of the base of the water collection pit is the same as that of the structural part 5, including a filter layer 53, a water-proof layer 52, and a cushion layer 51 arranged sequentially from bottom to top.

[0029] This invention also provides a method for constructing a precast ring beam stepped caisson support structure for a pit in a water-rich sand layer. The method includes the following construction steps:

[0030] Multi-layer precast ring beams are constructed, with pre-embedded drainage pipes in each layer. When constructing multi-layer precast ring beams, templates are made according to the plan and cross-sectional dimensions of the precast ring beams, reinforcement is arranged according to the design strength requirements and steel bars are tied, and concrete is poured after the pre-embedded drainage pipes are completed.

[0031] The process involves excavating a pit within a pit in a water-rich sandy layer, and installing precast ring beams layer by layer at corresponding locations during excavation until the designed elevation of the pit's base is reached. The precast ring beams are spaced apart and arranged in a stepped pattern from the base edge to the top edge, following the excavation slope of the pit. It should be noted that the top of the pit is measured and marked according to the design drawings. The precast ring beams are then hoisted into place. The excavation is carried out using a combination of manual labor and a small excavator in the water-rich sandy layer. During the excavation, the precast ring beams are installed layer by layer at corresponding locations until the designed elevation of the pit's base is reached. The precast ring beams are spaced apart and arranged in a stepped pattern from the base edge to the top edge, following the excavation slope of the pit. When installing the precast ring beams, excavation is carried out sequentially around the base of the cutting edge to ensure the precast ring beams sink at a uniform speed.

[0032] Multi-layer structural sections are constructed between each pair of adjacent precast ring beams, forming a stepped distribution from the base edge to the top edge of the pit, following the excavation slope of the pit-within-a-pit. These multi-layer structural sections, together with the multi-layer precast ring beams, form a stepped structure supporting the slope of the pit-within-a-pit. Each structural section includes, from bottom to top, a filter layer, a waterproof layer, and a cushion layer. Both ends of each pre-embedded drainage pipe are connected to two filter layers within the adjacent structural sections, enabling the gradual diversion of water from the water-rich sand layer. Before constructing the structural sections, a dewatering well (1.5m deep, using steel well pipes) is excavated in the center of the pit-within-a-pit (in this embodiment, a sump pit) base, and a drainage hose is installed. The dewatering well contains a sewage pump for groundwater extraction. Surrounding groundwater, passing through the filter layer and pre-embedded drainage pipes, gradually collects in the dewatering well and is then pumped away through the sewage pump and drainage hose. During the construction of the cushion layer, the waterproofing layer can be applied, and the dewatering well maintains continuous dewatering throughout this period.

[0033] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A precast ring beam stepped caisson support structure for a pit in a water-rich sand layer, characterized in that, include: Multi-layer precast ring beams are spaced apart and distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-within-pit. Each layer of the precast ring beams is pre-embedded with a drainage pipe. The multi-layered structural section is distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-within-a-pit and is connected between each two adjacent layers of precast ring beams. The multi-layered structural section and the multi-layered precast ring beams are connected together to form a stepped structure supporting the slope of the pit-within-a-pit. Each layer of the structural section includes a filter layer, a water-proof layer and a cushion layer arranged sequentially from bottom to top. The two ends of each pre-embedded drainage pipe are respectively connected to the two filter layers in the two adjacent layers of the structural section to realize the layer-by-layer diversion of water in the water-rich sand layer.

2. The precast ring beam stepped caisson support structure for pits in water-rich sand layers as described in claim 1, characterized in that: Each of the two ends of the pre-buried drainage pipe is provided with a filter screen at the connection point between the pipe and the corresponding filter layer.

3. The precast ring beam stepped caisson support structure for pits in water-rich sand layers as described in claim 1, characterized in that: Each layer of the precast ring beam has a cutting edge at the bottom.

4. The precast ring beam stepped caisson support structure for pits in water-rich sand layers as described in claim 1, characterized in that: The support structure also includes a foundation slab covering the surface of the stepped structure and forming the pit-in-pit sidewall, and a concrete layer filling the space between the foundation slab and the stepped structure.

5. A method for precast ring beam stepped caisson support in a pit within a water-rich sand layer, characterized in that, The method for constructing the precast ring beam stepped caisson support structure for a pit in a water-rich sand layer as described in claim 1 includes the following construction steps: Multi-layer precast ring beams are constructed, with pre-embedded drainage pipes embedded in each layer of the precast ring beams. The pit-within-a-pit is excavated in the water-rich sand layer, and the precast ring beams are installed layer by layer at the corresponding positions during the excavation process until the base design elevation of the pit-within-a-pit is reached. The multi-layer precast ring beams are set at intervals and are distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-within-a-pit. Multi-layer structural units are constructed between each pair of adjacent precast ring beams, so that the multi-layer structural units are distributed in a stepped manner from the base edge to the top edge according to the excavation slope of the pit-in-pit. The multi-layer structural units and the multi-layer precast ring beams are connected together to form a stepped structure supporting the slope of the pit-in-pit. Each layer of structural unit includes a filter layer, a water-proof layer, and a cushion layer arranged sequentially from bottom to top. Both ends of each pre-embedded drainage pipe are connected to the two filter layers in the two adjacent structural units, so as to realize the layer-by-layer diversion of water in the water-rich sand layer.

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