Deep foundation pit system with cofferdam serving as supporting structure
By combining the cofferdam with the foundation pit support structure in the deep foundation pit construction on the river beach, the cofferdam fill and water pressure provide support reaction force, the problems of construction stability and environmental impact of deep foundation pit under important roads on the river embankment are solved, and the foundation pit structure stability and river environmental protection are achieved.
Patent Information
- Application Number
- CN202420248123.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-01
- Publication Date
- 2025-03-04
- Estimated Expiration
- 2034-02-01
AI Technical Summary
In the case where important roads or other sensitive structures exist at the top of the river bank embankment, the construction of deep foundation pits on the side of the river bank is difficult to meet its own stability and surrounding environmental deformation requirements, and the cofferdam occupies a large range of the river channel, affecting the waterway and ecological environment.
A deep foundation pit system with a cofferdam as a support structure is adopted. By combining the cofferdam with the foundation pit support structure, the cofferdam fill pressure and river water pressure provide support reaction force for the enclosure structure, ensuring the stability of the foundation pit structure and reducing the settlement deformation of the river embankment.
It effectively controls the settlement deformation of the embankment road, ensures construction safety, reduces the cofferdam occupies the river range, saves cofferdam project investment, and protects the river ecological environment.
Smart Images
Figure CN222557661U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of deep foundation pits, in particular to a deep foundation pit structure on a riverbank side where an important road or other sensitive structures exist on a riverbank top. Background Art
[0002] There are many riverside buildings in water conservancy projects, such as water intake gates, tide gates, flood control gates, water intakes, and drainage outlets, which involve cofferdams and foundation pit projects during construction. When there are sensitive structures such as important roads and railways on the top of the river embankment, the foundation pit does not have the conditions for excavation and slope reduction, and only vertical support structures can be considered. However, for the foundation pit of the riverside building, since the riverbed is inclined and the terrain height difference on both sides of the vertical water flow direction is large, there is an imbalance in the soil pressure outside the foundation pit; and the vehicle load on the road on the top of the river embankment is large and the deformation control requirements are high, which makes the implementation of the foundation pit difficult. When the foundation pit is shallow, cantilever structures or diagonal bracing supports can be used; but when the foundation pit is deep, cantilever structures and diagonal bracing structures are difficult to meet their own stability and deformation requirements of the surrounding environment, and other technical solutions need to be adopted. Utility Model Content
[0003] In order to solve the problems existing in the existing deep foundation pit technology, the utility model provides a deep foundation pit system with a cofferdam serving as a supporting structure. By combining the cofferdam with the foundation pit supporting structure, the cofferdam filling pressure and the river water pressure are used to provide a supporting reaction force for the retaining structure, thereby ensuring the stability of the foundation pit structure itself, reducing the settlement deformation of the river embankment top, and controlling the deformation of the protected structure within the allowable range. At the same time, it can reduce the scope of the river occupied by the earth-rock cofferdam, which is more advantageous in saving the investment in the cofferdam project, avoiding the waterway and protecting the river ecological environment.
[0004] The technical solution adopted by the utility model is:
[0005] The deep foundation pit system with the cofferdam also serving as the supporting structure includes an earth-rock cofferdam body, a vertical anti-seepage body, a retaining structure, and an internal supporting structure; the earth-rock cofferdam body is set on the river side and serves as the backfill area of the supporting structure to provide a supporting reaction force; the vertical anti-seepage body is set in the soil around the foundation pit to form a closed circle; the retaining structure serves as the vertical supporting structure of the deep foundation pit; the internal supporting structure is a horizontal supporting structure in the foundation pit, and its two ends are connected to the retaining structure. The remaining foundation pit structures such as precipitation wells and drainage ditches are the same as conventional building foundation pits and are set according to actual needs.
[0006] Furthermore, the earth-rock cofferdam body is mainly composed of riprap dikes, earth-rock backfill areas, steel mesh slope protection, anti-scouring riprap areas, and clay backfill areas. The riprap dikes are built above the normal water level and serve as the foundation of the cofferdam. The clay backfill area is located in the center of the earth-rock cofferdam body, the earth-rock backfill areas are located on both sides of the clay backfill area, the anti-scouring riprap area is located outside the earth-rock backfill area, and the steel mesh slope protection is located on the outermost water-facing side of the earth-rock cofferdam body.
[0007] Furthermore, the vertical anti-seepage body is in the form of a concrete anti-seepage wall, a cement mixing pile anti-seepage wall, a high-pressure rotary jet pile anti-seepage wall or a combination thereof to prevent or reduce the infiltration of river water and groundwater and provide a dry construction environment for the foundation pit.
[0008] Furthermore, the enclosure structure adopts concrete cast-in-place piles, or steel pipe piles, or concrete underground continuous walls. When closely spaced concrete cast-in-place piles or steel pipe piles are used, high-pressure jet grouting piles are used to caulk the gaps between the piles.
[0009] Furthermore, the inner support structure adopts concrete support, steel support or a combination of the two. If the plane size of the foundation pit is large, column piles and steel lattice columns are set in the foundation pit, and one or more layers of plane support are adopted according to the depth of the foundation pit.
[0010] The utility model adopts a vertical support form of a retaining structure combined with an internal supporting structure. An earth-rock cofferdam is set on the river side to allow water to enter and block water. At the same time, water and soil pressure is provided for the foundation pit support structure, forming a foundation pit support structure closed on all sides. A circle of vertical anti-seepage bodies is set around the foundation pit to increase the seepage path.
[0011] The construction process of the deep foundation pit system of the utility model with cofferdam serving as supporting structure is as follows:
[0012] S1. Fill the earth-rock cofferdam to the top elevation of the vertical anti-seepage body, construct the vertical anti-seepage body of the foundation pit, form an anti-seepage closed circle outside the foundation pit, and continue to fill the cofferdam to the designed top elevation;
[0013] S2. Construction of foundation pit retaining structure;
[0014] S3. Before excavating the foundation pit, drain and dewater the pit first, then carry out the construction of the internal support structure and the foundation pit excavation: first excavate to the bottom surface of the first support, construct the first support, and after the concrete support strength reaches 80% of the design strength, or after the steel support is prestressed, carry out subsequent excavation; continue to excavate to the bottom surface of the next support, repeat the above steps until the excavation reaches the bottom of the pit, and pour the bottom concrete cushion in time;
[0015] S4. Complete the construction of permanent buildings in the foundation pit;
[0016] S5. After the strength of the permanent buildings in the foundation pit reaches the design requirements, the redundant parts of the supporting structure and the surrounding structure in the foundation pit shall be removed;
[0017] S6. Dismantle the earth-rock cofferdam.
[0018] Furthermore, in step S2, if a dewatering well is provided, the dewatering well is constructed in the pit at the same time.
[0019] The beneficial effects of the utility model are:
[0020] 1. The utility model combines the cofferdam project with the foundation pit support structure, and uses the backfill soil pressure of the cofferdam and the water pressure of the river channel to provide support reaction force, which can effectively control the settlement and deformation of the embankment top road, ensure that the embankment top road construction period is not interrupted, and protect the safety of the embankment top road construction period;
[0021] 2. The foundation pit of the utility model adopts a vertical support method. By combining the cofferdam with the foundation pit, the slope length of the cofferdam close to the foundation pit is greatly shortened, which can effectively reduce the scope of the river occupied by the cofferdam. It is more advantageous when the river is a waterway or has ecological protection requirements;
[0022] 3. Since the river bank terrain is higher than the riverbed, after the cofferdam is offset to the road side of the top of the embankment, not only the axis of the cofferdam is reduced, but also the height is greatly reduced, which effectively saves the investment in the cofferdam project. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 It is a plan layout diagram of an embodiment of the utility model system;
[0024] Figure 2 yes Figure 1 I-I sectional view;
[0025] Figure 3 It is a construction flow chart of the utility model.
[0026] In the figure: 1a-Riprap dike; 1b-Reinforced mesh slope protection; 1c-Riprap area; 1d-Soil and stone backfill area; 1e-Clay backfill area; 2a-Cofferdam anti-seepage wall; 2b-High-pressure rotary grouting anti-seepage wall of foundation pit; 3-Reinforced concrete close-packed support cast-in-place piles; 4-High-pressure rotary grouting caulking piles; 5a-First reinforced concrete inner support; 5b-Second steel support; 5c-Third reinforced concrete inner support; 5d-Fourth steel support; 6a-Concrete cushion; 6b-High-pressure rotary grouting pile reinforcement area; 7a-Reinforced concrete column piles; 7b-Steel lattice column; 8-Drainage ditch; 9-Precipitation well. DETAILED DESCRIPTION
[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.
[0028] like Figure 1-2 As shown, the utility model has a deep foundation pit system in which the cofferdam also serves as a supporting structure, including an earth-rock cofferdam body, a vertical anti-seepage body, a retaining structure, and an internal supporting structure. The earth-rock cofferdam body is arranged on the river side, including a riprap embankment 1a, a steel mesh slope protection 1b, an anti-impact riprap area 1c, an earth-rock backfill area 1d, and a clay backfill area 1e. It also serves as the backfill area on the river side of the foundation pit support to provide a supporting reaction force for the foundation pit support structure; the vertical anti-seepage body is arranged in the soil around the foundation pit to form a closed circle. In this example, the cofferdam anti-seepage wall 2a and the foundation pit high-pressure rotary spraying anti-seepage wall 2b are connected as a whole to form an anti-seepage wall on the outside of the foundation pit; the retaining structure adopts a vertical support form. In this example, reinforced concrete closely packed support cast-in-place piles 3 and high-pressure rotary spraying caulking piles 4 are used. ; The internal support structure is a horizontal support structure for the foundation pit, and its two ends are connected to the surrounding structure. This example consists of horizontal supports and columns. There are four horizontal supports in total vertically, namely, the first reinforced concrete internal support 5a, the second steel support 5b, the third reinforced concrete internal support 5c, and the fourth steel support 5d. A concrete cushion layer 6a and a high-pressure rotary jet pile reinforcement area 6b are set at the bottom of the pit. The column piles are composed of a lower reinforced concrete column pile 7a and an upper steel lattice column 7b. In addition, drainage ditches 8 and precipitation wells 9 can be set according to actual needs to intercept rainwater outside the pit and drain groundwater in the pit.
[0029] like Figure 1 to Figure 3 As shown in the figure, the construction process of the deep foundation pit system of the utility model in which the cofferdam also serves as the supporting structure is as follows:
[0030] S1. Fill the earth-rock cofferdam, which mainly includes riprap embankment 1a, steel mesh slope protection 1b, anti-scouring riprap area 1c, earth and rock backfill area 1d, and clay backfill area 1e. Figure 2 The partitions shown are filled to the top elevation of the cofferdam anti-seepage wall 2a; the cofferdam anti-seepage wall 2a and the foundation pit high-pressure rotary grouting anti-seepage wall 2b are constructed to form an anti-seepage closure on the outside of the foundation pit; the high-pressure rotary grouting pile reinforcement area 6b at the bottom of the foundation pit is constructed; the cofferdam body is continued to be filled to the designed weir top elevation;
[0031] S2, construction enclosure structure, in this example mainly includes reinforced concrete dense support cast-in-place piles 3, high-pressure rotary grouting caulking piles 4, reinforced concrete column piles 7a and steel lattice columns 7b in the foundation pit; in addition, in this example, the lower part of the foundation pit is mainly a gravel and pebble layer with strong water permeability, and a dewatering well is required, so a dewatering well 9 in the pit is constructed at the same time;
[0032] S3. Construct the internal support structure. Before excavating the foundation pit, drain the pit and dewater it. Then excavate to the bottom of the first support and construct the first reinforced concrete internal support 5a. After the concrete support strength reaches 80% of the design strength, proceed with subsequent excavation. Excavate the foundation pit to 0.4m below the design center of the second steel support 5b, construct the second steel support 5b, and apply prestress. When excavating the soil layer below the steel support, prestress the steel support. Excavate the foundation pit to 0.5m below the design center of the third support, construct the third reinforced concrete internal support 5c. After the support strength reaches 80% of the design strength, proceed with subsequent excavation. Excavate the foundation pit to 0.4m below the design center of the fourth support, construct the fourth steel support 5d, and apply prestress. When excavating the soil layer below the steel support, prestress the steel support. After excavating to the bottom of the pit, pour the bottom concrete cushion layer 6a in time.
[0033] S4. This example involves pipe jacking construction. After the pipe jacking construction is completed, the permanent buildings in the foundation pit are constructed;
[0034] S5, after the strength of the permanent buildings in the foundation pit reaches the design requirements, the first reinforced concrete inner support 5a, the second steel support 5b, the third reinforced concrete inner support 5c, the fourth steel support 5d, and the steel lattice column 7b in the foundation pit are removed, and the redundant parts of the surrounding structure are chiseled out, that is, the reinforced concrete dense support cast-in-place piles 3 and the high-pressure rotary grouting caulking piles 4 in this example;
[0035] S6. Finally, dismantle the earth-rock cofferdam.
[0036] The above embodiments describe the present invention in conjunction with the accompanying drawings, but this should not be understood as limiting the scope of protection of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, technical solutions obtained by equivalent replacement or equivalent transformation methods all belong to the scope of protection of the present invention.
Claims
1. The deep foundation pit system with cofferdam serving as supporting structure is characterized by: It includes an earth-rock cofferdam body, a vertical anti-seepage body, a retaining structure, and an internal support structure; the earth-rock cofferdam body is arranged on the river side and serves as the backfill area of the support structure to provide support reaction force; the vertical anti-seepage body is arranged in the soil around the foundation pit to form a closed circle; the retaining structure serves as the vertical support structure of the deep foundation pit; the internal support structure is a horizontal support structure in the foundation pit, and its two ends are connected to the retaining structure.
2. The deep foundation pit system with cofferdam serving as supporting structure according to claim 1 is characterized in that: The earth-rock cofferdam body is mainly composed of riprap dikes, earth-rock backfill areas, steel mesh slope protection, anti-scouring riprap areas, and clay backfill areas. The riprap dikes are filled above the normal water level and serve as the foundation of the cofferdam. The clay backfill area is located in the center of the earth-rock cofferdam body, the earth-rock backfill areas are located on both sides of the clay backfill area, the anti-scouring riprap area is located outside the earth-rock backfill area, and the steel mesh slope protection is located on the outermost water-facing side of the earth-rock cofferdam body.
3. The deep foundation pit system with cofferdam serving as supporting structure according to claim 1 is characterized in that: The vertical anti-seepage body is a concrete anti-seepage wall.
4. The deep foundation pit system with cofferdam serving as supporting structure according to claim 1 is characterized in that: The enclosure structure adopts concrete cast-in-place piles or concrete underground continuous walls. When close-packed concrete cast-in-place piles are adopted, high-pressure rotary jet piles are used to caulk the gaps between the piles.
5. The deep foundation pit system with cofferdam serving as supporting structure according to claim 1 is characterized in that: The inner support structure adopts concrete support, steel support or a combination of the two. If the plane size of the foundation pit is large, column piles and steel lattice columns are set in the foundation pit, and one or more layers of plane support are used according to the depth of the foundation pit.