A method for layered and segmented excavation of ultra-large foundation pits

Abstract

This invention discloses a method for excavating a super-large foundation pit in layers and sections, comprising the following steps: Step 1: Before excavation, construct the first layer of supporting and diagonal bracing, excavate the soil in the central and peripheral areas of the first layer of the foundation pit, and build several excavation ramps at the edge of the foundation pit; Step 2: After the first layer of foundation pit is excavated, construct the second layer of supporting, then construct the diagonal bracing on both sides and excavate the peripheral area of ​​the second layer, followed by excavating the soil in the central area of ​​the second layer; Step 3: After the excavation of the previous layer of foundation pit is completed, repeat Step 2 to excavate the next layer of foundation pit until the penultimate layer of foundation pit is completed; Step 4: After the penultimate layer of foundation pit is completed, construct the last layer of supporting, excavate the soil in the central area of ​​the last layer, then construct the diagonal bracing on both sides and excavate the soil in the peripheral area. This invention features a smooth and orderly construction process, saves construction costs, has reasonable and orderly construction steps, prevents the foundation pit from deforming during excavation, ensures high stability, improves construction safety, and eliminates the risk of collapse.

Description

Technical Field

[0001] This invention belongs to the field of building construction technology, and in particular to a method for layered and segmented earthwork excavation of ultra-large foundation pits. Background Technology

[0002] With the increasing urbanization and rising environmental demands of residents in my country, fully underground sewage treatment plants, characterized by their ability to harmonize with the surrounding environment, strong enclosure, and lack of secondary pollution, are becoming a development trend and direction for urban sewage treatment projects. These plants, by placing the sewage treatment structures underground and effectively integrating with the surrounding landscape, offer governments and residents a new alternative to traditional water treatment plants. The construction of fully underground sewage treatment plants involves the excavation of ultra-large foundation pits. A foundation pit is an earthen pit excavated according to the foundation design location, based on the base elevation and foundation plane dimensions. Ultra-large foundation pits are characterized by their large area, large volume of earthwork excavation, and deep excavation depth. Current technologies for constructing ultra-large foundation pits typically employ a basin-type excavation method, first excavating the central area of ​​the pit, reserving a counterweight slope around the perimeter, and then excavating the surrounding earthwork after the central area is completed.

[0003] The above construction method has the following technical problems: 1. During the excavation of the foundation pit, since the central area is completely excavated before the remaining areas are excavated, the load on the supporting structure at the edge increases with the excavation depth. If the construction of the supporting structure is not timely, it is easy to cause the foundation pit to deform. There is a great risk of collapse in the process of excavating super-large foundation pits; 2. In the traditional excavation method, the construction process of the support structure is cumbersome and complicated. The steps of earthwork excavation and support structure construction are relatively chaotic, resulting in slow construction progress, low efficiency, high time cost, and difficulty in meeting the construction period requirements. Summary of the Invention

[0004] This invention provides a method for layered and segmented excavation of ultra-large foundation pits to solve the above-mentioned problems existing in the prior art.

[0005] This invention provides a method for layered and segmented excavation of ultra-large foundation pits, comprising the following steps:

[0006] Step 1: Excavate the first layer of foundation pit

[0007] Before excavation, construct the first layer of bracing and diagonal bracing, excavate the soil in the central and surrounding areas of the first layer of the foundation pit, and build several excavation ramps at the edge of the foundation pit.

[0008] Step 2: Excavate the second layer of foundation pit

[0009] After the first layer of foundation pit is excavated, the second layer of bracing is constructed. The diagonal bracing on both sides is constructed in sequence, and the perimeter area of ​​the second layer is excavated. Then the soil in the central area of ​​the second layer is excavated, and the excavated soil is transported out through the excavation ramp.

[0010] Step 3: Excavate the remaining foundation pits

[0011] After the excavation of the previous layer of foundation pit is completed, repeat step two to excavate the next layer of foundation pit until the second to last layer of foundation pit is completed.

[0012] Step 4: Excavate the final layer of the foundation pit

[0013] After the penultimate layer of foundation pit construction is completed, the final layer of bracing is constructed, and the soil in the central area of ​​the final layer is excavated. Subsequently, the diagonal bracing on both sides is constructed in sequence, and the soil in the surrounding area is excavated. The final layer of foundation pit excavation is completed, and the construction is finished.

[0014] Furthermore, in step two, after the second layer of bracing is completed, the left-side exit ramp is removed, the left-side second-layer diagonal bracing is constructed, and the soil around the left-side second-layer area is excavated. The excavated soil is transported out through the right-side exit ramp. After the excavation is completed, the left-side exit ramp is rebuilt. Subsequently, the right-side exit ramp is removed, the right-side second-layer diagonal bracing is constructed, and the soil around the right-side second-layer area is excavated. The excavated soil is transported out through the left-side exit ramp. After the excavation is completed, the right-side exit ramp is rebuilt.

[0015] Furthermore, in step four, after the excavation of the last layer of central area is completed, the left-side exit ramp is removed, the left-side last layer of inclined supports is constructed, and the soil in the left-side last layer of surrounding area is excavated. The excavated soil is transported out from the right-side exit ramp. After the excavation of the left-side surrounding area is completed, the right-side exit ramp is removed, the right-side last layer of inclined supports is constructed, and the soil in the right-side last layer of surrounding area is excavated. The excavated soil is directly hoisted out of the foundation pit.

[0016] Furthermore, in step one, the site surface is cleaned before excavating the foundation pit, the elevation of the first layer of diagonal bracing and counter-bracing is determined, and the capping beam is constructed.

[0017] Furthermore, the excavation ramp is reinforced with shotcrete.

[0018] Furthermore, the bracing is constructed using the slotting method.

[0019] Furthermore, in step four, after the earthwork in the central area and the surrounding area is excavated to the foundation elevation, a cushion layer is constructed on the foundation, and the foundation pit bottom slab is constructed on the cushion layer.

[0020] Furthermore, in step four, when dismantling the right-side excavation ramp, a grab bucket and an excavator are used for excavation.

[0021] Furthermore, during the excavation process, the excavated soil is transported out of the foundation pit via transport vehicles along the excavation ramp.

[0022] Furthermore, the two sides of the excavation ramp are reinforced with reinforced concrete slab supports and truss support beams.

[0023] The advantages and positive effects of this invention are:

[0024] 1. This method of excavating super-large foundation pits in layers and sections, with the excavation of the perimeter area and the central area carried out alternately, and the support structure at the corresponding position constructed layer by layer, can well adapt to the excavation of super-large foundation pits under soft geological conditions, ensuring that the foundation pit is firmly supported at all times during the excavation process, preventing the foundation pit from deforming, and eliminating the safety hazard of foundation pit collapse.

[0025] 2. This method of layered and segmented earthwork excavation for the super-large foundation pit allows for rapid and orderly excavation of the surrounding and central areas in a clear and straightforward manner. This effectively shortens the earthwork excavation period, optimizes the construction method, and significantly improves construction efficiency and economic benefits.

[0026] 3. In this method of excavating earthwork in layers and sections for ultra-large foundation pits, the soil removal ramp is set up to facilitate soil removal, reduce soil transportation costs, and achieve rapid soil removal from ultra-large foundation pits, which further improves construction efficiency. The soil removal ramp is reinforced with reinforced concrete slab supports and trusses on both sides to improve the load-bearing capacity of the soil removal ramp, prevent the soil removal ramp from collapsing, and eliminate safety hazards.

[0027] 4. The construction process of this invention is smooth and orderly, with a short excavation period, saving construction costs. The excavation of the foundation pit is carried out in sections and layers, and the construction of the supporting structure is carried out alternately. The construction steps are reasonable and orderly. The foundation pit is not easily deformed during the excavation process, has high stability, improves construction safety, and eliminates the risk of collapse. Attached Figure Description

[0028] Figure 1 This is a top view of the foundation pit support structure of the present invention;

[0029] Figure 2 This is a front view of the foundation pit support structure of the present invention;

[0030] Figure 3 This is a schematic diagram of the excavation steps of the present invention;

[0031] Figure 4 This is a flowchart of the method steps of the present invention.

[0032] In the diagram, 1 is the diagonal brace, 2 is the peripheral area, 3 is the counter brace, 4 is the central area, 5 is the connecting beam, and 6 is the excavation ramp. Detailed Implementation

[0033] The invention will now be described in further detail with reference to the accompanying drawings.

[0034] This invention provides a method for layered and segmented excavation of ultra-large foundation pits, taking the construction of a foundation pit with a three-layer support structure as an example, including the following steps:

[0035] Step 1: Construct the first layer of bracing 3 and diagonal bracing 1.

[0036] After the diaphragm wall construction is completed and the wall strength meets the design requirements, the entire foundation pit surface is cleaned, the elevation of the first layer of diagonal bracing 1 and anti-bracing 3 is determined, and the capping beam is constructed; the first layer of anti-bracing 3 is constructed in the middle of the foundation pit, and the first layer of diagonal bracing 1 is constructed at the edge of the foundation pit; the anti-bracing 3 is constructed using the slotting method; the anti-bracing 3 of the same layer is connected into a whole by the connecting beam 5 set horizontally in the middle.

[0037] Step 2: Excavate the first layer, including the peripheral area 2 and the central area 4.

[0038] After the first layer of bracing 3 and diagonal bracing 1 is constructed, the foundation pit is divided into a central area 4 and a peripheral area 2. The central area 4 is where the bracing 3 is installed in the middle of the foundation pit, and the peripheral areas 2 are on both sides of the central area 4. The soil in the first layer of peripheral areas 2 and central area 4 is excavated, with the soil being excavated from the perimeter of the foundation pit towards the center. Several excavation ramps 6 are built at the edge of the foundation pit. The excavation ramps 6 are distributed in the middle of the foundation pit and on the left and right sides. The excavation ramps 6 are reinforced with shotcrete. The thickness of the concrete slope protection is 5cm. The slope of the excavation ramps 6 is 1:7. The two sides of the excavation ramps 6 are reinforced with reinforced concrete slab bracing and truss support beams to improve the stability of the excavation ramps 6, prevent the excavation ramps 6 from collapsing, and eliminate safety hazards. During the excavation, the soil is transported out of the foundation pit along the excavation ramps 6 by transport vehicles. The soil in the first layer of central area 4 is excavated to 30cm above the elevation of the second layer of bracing 3.

[0039] Step 3: Construct the second layer of bracing 3

[0040] After the earthwork excavation of the first layer peripheral area 2 and central area 4 is completed, the second layer of support 3 is constructed below the first layer support 3 using the trenching method;

[0041] Step 4: Construction of the Second Layer of Diagonal Bracing 1. Excavation of the Peripheral Area of ​​the Second Layer 2

[0042] After the second layer of bracing 3 is completed, the left-side excavation ramp 6 is removed, the left-side second layer of diagonal bracing 1 is constructed, the soil around the left-side second layer 2 is excavated, and the excavated soil is transported out from the right-side excavation ramp 6. After the excavation is completed, the left-side excavation ramp 6 is rebuilt, and then the right-side excavation ramp 6 is removed. The right-side second layer of diagonal bracing 1 is constructed, the right-side second layer of diagonal bracing 1 is excavated, and the soil around the right-side second layer 2 is excavated. The excavated soil is transported out from the left-side excavation ramp 6. After the excavation is completed, the right-side excavation ramp 6 is rebuilt.

[0043] Step 5: Excavate the second layer central area 4

[0044] After the second layer of diagonal bracing 1 is completed, the soil in the central area 4 of the second layer is excavated. The excavated soil is transported from the middle of the foundation pit to the left and right sides of the excavation ramp 6. The soil in the central area 4 is excavated to 30cm above the elevation of the third layer of bracing 3.

[0045] Step Six: Construct the third layer of bracing 3

[0046] After the earthwork in the central area of ​​the second layer 4 was excavated, the third layer of bracing 3 was constructed using the trenching method;

[0047] Step 7: Excavate the central area of ​​the third layer 4

[0048] After the third layer of bracing 3 is completed, the soil in the central area 4 of the third layer is excavated; after excavation to the base elevation, a cushion layer is constructed on the base of the central area 4, and the foundation pit bottom slab is constructed on the cushion layer.

[0049] Step 8: Construction of the third layer of diagonal bracing 1. Excavation of the perimeter area of ​​the third layer 2.

[0050] After the excavation of the central area 4 of the third layer is completed, the left-side excavation ramp 6 is removed, and the left-side third-layer inclined support 1 is constructed. After the left-side inclined support 1 is constructed, the soil of the left-side third-layer peripheral area 2 is excavated. Then, the right-side excavation ramp 6 is removed, and the right-side third-layer inclined support 1 is constructed. After the right-side inclined support 1 is constructed, the soil of the right-side third-layer peripheral area 2 is excavated. The excavated soil is directly hoisted out of the foundation pit. After the excavation of the right-side third-layer peripheral area 2 is completed, a cushion layer is constructed on the base of the peripheral area 2, and the foundation pit bottom slab is constructed on the cushion layer. When removing the right-side ramp, a grab bucket is used in conjunction with an excavator for excavation.

[0051] The present invention provides a method for excavating earthwork in layers and sections for ultra-large foundation pits, which can be applied to the construction of foundation pits with multi-layered support structures. During construction, the construction steps of the second layer foundation pit can be repeated to complete the construction of the second to penultimate layer foundation pits.

[0052] The construction process of this invention is smooth and orderly, with a short excavation period, saving construction costs. The excavation of the foundation pit is carried out in sections and layers, and the construction of the supporting structure is carried out alternately. The construction steps are reasonable and orderly. The foundation pit is not easily deformed during the excavation process, has high stability, improves construction safety, and eliminates the risk of collapse.

[0053] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for layered and segmented excavation of ultra-large foundation pits, characterized in that, Includes the following steps: Step 1: Excavate the first layer of foundation pit Before excavation, construct the first layer of bracing (3) and diagonal bracing (1), excavate the soil in the central area (4) and surrounding area (2) of the first layer of the foundation pit, and build several excavation ramps (6) at the edge of the foundation pit; Step 2: Excavate the second layer of foundation pit After the first layer of foundation pit is excavated, the second layer of support (3) is constructed, the diagonal supports (1) on both sides are constructed in sequence, and the perimeter area (2) of the second layer is excavated. Then the soil in the central area (4) of the second layer is excavated, and the excavated soil is transported out from the excavation ramp (6). After the second layer of bracing (3) is completed, the left-side excavation ramp (6) is removed, the left-side second layer of diagonal bracing (1) is constructed, and the soil in the left-side second layer surrounding area (2) is excavated. The excavated soil is transported out from the right-side excavation ramp (6). After the excavation is completed, the left-side excavation ramp (6) is rebuilt. Then the right-side excavation ramp (6) is removed, the right-side second layer of diagonal bracing (1) is constructed, and the soil in the right-side second layer surrounding area (2) is excavated. The excavated soil is transported out from the left-side excavation ramp (6). After the excavation is completed, the right-side excavation ramp (6) is rebuilt. Step 3: Excavate the remaining foundation pits After the excavation of the previous layer of foundation pit is completed, repeat step two to excavate the next layer of foundation pit until the second to last layer of foundation pit is completed. Step 4: Excavate the final layer of the foundation pit After the penultimate layer of foundation pit construction is completed, the last layer of support (3) is constructed, the soil in the central area (4) of the last layer is excavated, and then the diagonal supports (1) on both sides are constructed in sequence and the soil in the surrounding area (2) is excavated. The excavation of the last layer of foundation pit is completed and the construction is finished.

2. The method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, In step four, after the excavation of the last layer of the central area (4) is completed, the left-side excavation ramp (6) is removed, the left-side last layer of inclined support (1) is constructed, and the excavation of the left-side last layer of the peripheral area (2) is carried out. The excavated soil is transported out from the right-side excavation ramp (6). After the excavation of the left-side peripheral area (2) is completed, the right-side excavation ramp (6) is removed, the right-side last layer of inclined support (1) is constructed, and the excavation of the right-side last layer of the peripheral area (2) is carried out. The excavated soil is directly hoisted out of the foundation pit.

3. The method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, In step one, the site surface is cleaned before excavating the foundation pit, the elevation of the first layer of diagonal bracing (1) and counter bracing (3) is determined, and the capping beam is constructed.

4. The method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, The excavation ramp (6) is reinforced with shotcrete.

5. The method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, The bracing (3) is constructed using the slotting method.

6. The method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, In step four, after the earthwork in the central area (4) and the surrounding area (2) is excavated to the base elevation, a cushion layer is constructed on the base, and the foundation pit bottom slab is constructed on the cushion layer.

7. The method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, In step four, when dismantling the right-side excavation ramp (6), a grab bucket and an excavator are used for excavation.

8. The method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, During the excavation process, the excavated soil was transported out of the foundation pit by transport vehicles along the excavation ramp (6).

9. A method for layered and segmented excavation of an ultra-large foundation pit according to claim 1, characterized in that, The two sides of the excavation ramp (6) are reinforced with reinforced concrete slab supports and truss support beams.

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