A method for constructing underground continuous walls in existing underground structures

Abstract

The present application discloses a method for constructing an underground continuous wall in an existing underground structure, which relates to the field of underground continuous walls and includes the following steps: S1, dewatering operation, lowering the groundwater level around the old underground structure to below the bottom plate; S2, slope reduction operation, removing the top plate of the old underground structure and constructing a ramp from the ground to the bottom plate for mechanical equipment to enter; S3, trenching operation, breaking the local bottom plate and digging a continuous trench according to the designed position of the underground continuous wall; S4, lowering the steel cage, lowering the steel cage into the continuous trench; S5, pouring operation, pouring concrete into the continuous trench, and forming an underground continuous wall after the concrete solidifies. The present application has the effect of reducing the occurrence of soil collapse around the wall into the construction pit and improving the safety of construction operations within the wall.

Description

Technical Field

[0001] The present application relates to the field of underground continuous walls, and in particular to a method for constructing underground continuous walls in an existing underground structure. Background Art

[0002] In recent years, with the continuous development of cities, more and more building functions cannot meet the growing urban needs, and the renovation of old buildings in cities is imperative. Among them, such old buildings often have old underground structures.

[0003] In the related art, an old underground structure includes a wall set underground, a bottom plate is set at the bottom of the wall, a top plate is set at the top of the wall, there is a floor around the top plate, and the bottom plate elevation is 3m lower than the floor elevation. In actual construction, in order to ensure the normal progress of the reconstruction construction, large-scale demolition and obstacle clearance construction are often carried out on the old underground structure. After the old underground structure is completely demolished, a construction pit is formed at the location of the original old underground structure. At this time, if the construction pit needs to construct an underground continuous wall part, a trenching machine can be used to dig a continuous trench in the construction pit, and a steel cage can be placed in the continuous trench and concrete can be poured to form an underground continuous wall.

[0004] Regarding the above-mentioned related technologies, the soil around the old underground structure exerts great pressure on the underground structure. At this time, the soil around the construction pit can easily collapse into the construction pit, posing a major safety hazard to the construction work in the construction pit. There is room for improvement. Summary of the Invention

[0005] In order to improve the related technology that after the old underground structure is completely demolished, the soil around the construction pit is easily collapsed into the construction pit, which poses a great safety hazard to the construction work in the construction pit, the present application provides an underground continuous wall construction method in an existing underground structure.

[0006] This application provides a method for constructing an underground continuous wall in an existing underground structure, which adopts the following technical solution:

[0007] A method for constructing an underground continuous wall in an existing underground structure comprises the following steps:

[0008] S1. Dewatering operation: lowering the groundwater level around the old underground structure to below the floor;

[0009] S2: Slope reduction operation: remove the top plate of the old underground structure and construct a ramp from the ground to the bottom plate for mechanical equipment to enter;

[0010] S3: Trenching operation: according to the designed position of underground continuous wall, remove the local bottom plate and dig the continuous trench;

[0011] S4, lowering the steel cage into the continuous trough;

[0012] S5. Pouring operation: pouring concrete into the continuous trough. After the concrete solidifies, an underground continuous wall is formed.

[0013] By adopting the above technical solution, the groundwater around the old underground structure is lowered, the top plate of the old underground structure is broken, and the mechanical equipment is moved to the bottom plate through a ramp. Then, a continuous trench and an underground continuous wall are constructed on the bottom plate. The surrounding soil is supported by the walls and bottom plate of the old underground structure, which reduces the occurrence of soil around the wall collapsing into the construction pit and improves the safety of construction operations within the wall.

[0014] Preferably, in step S1, a light well point dewatering device is set on one side of the old underground structure, and a water-blocking outer wall is set on the other sides of the old underground structure. The light well point dewatering device includes a well pipe, and the lower end of the well pipe and the lower side of the water-blocking outer wall are both lower than the bottom plate.

[0015] By adopting the above technical solution, the light well point dewatering device continuously pumps out groundwater, reduces the groundwater around the old underground structure, and causes a large amount of groundwater to flow into the inside of the water-blocking outer wall from the outside of the water-blocking outer wall. At the same time, the water-blocking outer wall can play a certain stabilizing role on the soil around the old underground structure, thereby reducing the occurrence of groundwater flowing into the water-blocking outer wall, further reducing the occurrence of soil around the wall collapsing into the construction pit, and improving the safety of construction operations within the wall.

[0016] Preferably, in S2, the upper part of one side of the old underground structure wall is demolished, and an avoidance gap is formed on the wall, and then the soil outside the avoidance gap is unloaded, and the unloaded soil is accumulated under the avoidance gap; then, the soil on both sides of the avoidance gap is sorted and a ramp is formed.

[0017] By adopting the above technical solution, the upper part of one side of the wall is demolished, reducing the damage to the strength of the wall and ensuring normal support for the soil around the wall; at the same time, the soil outside the avoidance gap is unloaded, so that the unloaded soil is accumulated under the avoidance gap, and the soil is taken on site, which facilitates the formation of the ramp and helps to reduce the space occupied by the ramp inside the wall.

[0018] Preferably, the ramp surface is made of concrete.

[0019] By adopting the above technical solution, the ramp is built with concrete, which helps to ensure the bearing capacity of the ramp.

[0020] Preferably, in step S3, while the continuous trench is being dug, mud is cyclically extracted and injected into the dug continuous trench, the specific gravity of the mud circulating in the continuous trench is controlled to be 1.1-1.25 g / cm³, and the viscosity of the circulating mud is controlled to be 25-30 Pa·s.

[0021] By adopting the above technical solution, mud is injected into the continuous tank, and the circulating mud is guaranteed to have a larger specific gravity of soil and a larger viscosity, thereby ensuring that the circulating mud supports the side wall of the continuous tank and helping to reduce the occurrence of groundwater inrush into the wall.

[0022] Preferably, S6, the ground wall is raised by installing a support formwork on the upper side of the formed underground continuous wall, setting a steel cage in the support formwork, and then pouring concrete into the support formwork to raise the underground continuous wall to the ground elevation.

[0023] By adopting the above technical solution, the formed underground continuous wall is raised and extended to the ground level to ensure the construction of the new underground structure.

[0024] Preferably, in step S4, the upper end of the steel cage is a steel bar joint;

[0025] In step S6, the lower side of the steel cage in the support formwork is fixedly connected to the steel bar joint portion.

[0026] The adoption of the above technical solution helps to ensure the stability of the upper connecting part of the underground continuous wall.

[0027] Preferably, in step S4, a protective cover is placed on the steel bar joint.

[0028] By adopting the above technical solution, the protective cover protects the steel bar joints, reducing the occurrence of damage to the steel bar joints.

[0029] Preferably, in step S3, a guide groove is first dug, and guide walls are constructed on both sides of the guide groove in the width direction, and then the guide groove is deepened to form a continuous groove.

[0030] By adopting the above technical solution, the broken part of the bottom plate is protected by the guide wall, which helps to ensure the stability of the bottom plate and facilitates the continuous groove forming operation.

[0031] Preferably, before installing the support formwork, the guide wall and the bottom plate on one side of the formed underground continuous wall are broken, and the upper part of the formed underground continuous wall is chiseled off.

[0032] By adopting the above technical solution, after breaking down the guide wall and bottom plate on one side, the upper part of the formed underground continuous wall can be chiseled off more easily. At the same time, the steel bar joints will be more exposed, and the upper side of the formed underground continuous wall will be rougher, which will help to improve the stability of the upper connecting part of the underground continuous wall.

[0033] In summary, this application includes at least one of the following beneficial technical effects:

[0034] 1. By reducing groundwater levels around the old underground structure and partially demolishing it, mechanical equipment can be moved to the base plate via a ramp. Continuous trenches and underground continuous walls can then be constructed on the base plate. The surrounding soil can be supported by the walls and base plate of the old underground structure, reducing the chance of soil around the walls collapsing into the construction pit and improving the safety of construction operations within the walls.

[0035] 2. By connecting the steel bar joint with the steel cage in the support formwork and chiseling off the upper part of the formed underground continuous wall, the upper part of the formed underground continuous wall is made rougher, which helps to improve the stability of the upper connecting part of the underground continuous wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This application mainly reflects the flow chart of the underground continuous wall construction method in the existing underground structure. DETAILED DESCRIPTION

[0037] The present application is further described in detail below with reference to the accompanying drawings.

[0038] The embodiment of the present application discloses a method for constructing an underground continuous wall in an existing underground structure.

[0039] Example 1:

[0040] Reference Figure 1 The construction method of underground continuous wall in an existing underground structure includes the following steps:

[0041] S1. Precipitation operations.

[0042] S1.1. Establish a water-blocking exterior wall around the old underground structure. The water-blocking exterior wall is arranged around the old underground structure, with a water-blocking gap formed between the ends of the water-blocking exterior wall. The underside of the water-blocking exterior wall is lower than the floor of the old underground structure. In this embodiment, the water-blocking exterior wall can be constructed using the TAD method or by using a trenching machine to dig a continuous trench, lower a steel cage into the trench, and inject concrete to form the trench.

[0043] S1.2. A dewatering well is drilled on the ground on one side of the water-blocking gap in the old underground structure, and a light well-point dewatering device is set on the side of the water-blocking gap. The light well-point dewatering device includes a water collecting pipe, a well pipe and a water pump. The water collecting pipe is located between the water-blocking gaps, and the two ends of the water collecting pipe extend to the two ends of the water-blocking outer wall respectively, and the water collecting pipe is located on the outside of the old underground structure. The well pipe is arranged vertically, the upper end of the well pipe is connected to the water collecting pipe, and the lower side of the well pipe is inserted into the dewatering well. The lower end of the well pipe is lower than the bottom plate of the old underground structure, and there are several dewatering wells arranged along the water collecting pipe, and the well pipes correspond to the dewatering wells one by one. At the same time, the water pump's suction port is connected to the water collecting pipe, and groundwater is extracted through the water collecting pipe and the well pipe and discharged to the outside.

[0044] S2. Slope reduction operation. Remove the roof, beams, columns, and partition wall structures of the old underground structure, and remove the upper part of one side of the old underground structure wall to form an avoidance gap on the wall. The height of the avoidance gap can be one-third to two-thirds of the wall height. Preferably, the height of the avoidance gap is one-half of the wall height. Then, unload the soil outside the avoidance gap and allow the unloaded soil to accumulate below the avoidance gap. Subsequently, the soil on both sides of the avoidance gap is sorted to form a ramp, which gradually descends from the ground side to the bottom plate. Finally, lay steel bars and pour concrete on the slope of the ramp to form a reinforced concrete slope.

[0045] S3. Trenching. Excavators, trenching machines, and other equipment can access the floor slab of the old underground structure via a ramp. Then, based on the designed location of the underground continuous wall, the floor slab is partially broken away. A guide trench is dug with an excavator, and guide walls are constructed on both sides of the trench width. The trenching machine is then used to deepen the trench, forming a continuous trench.

[0046] While the continuous trench is being dug, mud is cyclically pumped out and injected into the dug continuous trench. The specific gravity of the mud circulating in the continuous trench is controlled to be 1.1-1.25 g / cm³, and the viscosity of the circulating mud is controlled to be 25-30 Pa·s. Preferably, the specific gravity of the mud circulating in the continuous trench is controlled to be 1.2 g / cm³, and the viscosity of the circulating mud is controlled to be 28 Pa·s. After the continuous trench is completed, the specific gravity of the mud circulating in the continuous trench is controlled to be 1.1-1.15 g / cm³, and preferably, the specific gravity of the mud circulating in the continuous trench is controlled to be 1.1 g / cm³.

[0047] S4. Lower the rebar cage. Use a crane to lower the rebar cage into the continuous trough. The upper end of the rebar cage is the rebar joint, which is covered with a protective sleeve. The rebar joint is composed of the upper ends of several vertical rebars. In this embodiment, the protective sleeve can be either a plastic sleeve or a rubber sleeve. The protective sleeve is placed on the upper ends of the vertical rebars, and the protective sleeve is placed corresponding to the upper ends of the vertical rebars.

[0048] S5. Pouring operation: Pour concrete into the continuous trough. After the concrete solidifies, an underground continuous wall is formed.

[0049] S6. Connect the ground and wall.

[0050] S6.1. Remove the guide wall and bottom plate on one side of the formed underground continuous wall, and chisel away the upper part of the formed underground continuous wall to expose the steel bar joints; then, remove each protective cover.

[0051] S6.2. Install a support formwork on the upper side of the completed diaphragm wall. Braces can be provided on the guide wall and base plate to support the support formwork. Simultaneously, install a rebar cage within the support formwork, securing the underside of the rebar cage to the rebar joints within the support formwork. In this embodiment, the underside of the rebar cage within the support formwork is welded to the rebar joints. Then, pour concrete into the support formwork, raising the diaphragm wall to the ground level. Construction of the diaphragm wall is complete once the concrete solidifies and stabilizes.

[0052] Example 2:

[0053] Reference Figure 1 The construction method of underground continuous wall in an existing underground structure includes the following steps:

[0054] S1. Precipitation operations.

[0055] S1.1. Set up a water-blocking outer wall around the old underground structure. The water-blocking outer wall is set around the old underground structure, and the lower side of the water-blocking outer wall is lower than the bottom plate of the old underground structure.

[0056] It should be noted that in this embodiment, the renovation area is larger than the old underground structure area, and the old underground structure is located within the renovation area. The water-blocking exterior wall is the exterior wall portion of the underground continuous wall. The water-blocking exterior wall can be completed using the TAD method or by using a trenching machine to dig a continuous trench, lower a steel cage into the trench, and inject concrete to form the trench.

[0057] S1.2. A dewatering well is drilled on the ground on the side where the old underground structure is farther away from the water-blocking outer wall, and a light well-point dewatering device is installed on one side of the dewatering well. The light well-point dewatering device includes a water collecting pipe, a well pipe, and a water pump. The water collecting pipe is set along the side of the old underground structure close to the corresponding water-blocking outer wall. The two ends of the water collecting pipe extend to the water-blocking outer walls on both sides, and the water collecting pipe is located on the outside of the old underground structure. The well pipe is set vertically, the upper end of the well pipe is connected to the water collecting pipe, and the lower side of the well pipe is inserted into the dewatering well. The lower end of the well pipe is lower than the bottom plate of the old underground structure, and several dewatering wells are set along the water collecting pipe, and the well pipes correspond to the dewatering wells one by one. At the same time, the water pump's suction port is connected to the water collecting pipe, and groundwater is extracted through the water collecting pipe and the well pipe and discharged to the outside.

[0058] S2. Slope reduction operation. Remove the roof, beams, columns, and partition wall structures of the old underground structure, and remove the upper part of one side of the old underground structure wall to form an avoidance gap on the wall. The height of the avoidance gap can be one-third to two-thirds of the wall height. Preferably, the height of the avoidance gap is one-half of the wall height. Then, unload the soil outside the avoidance gap and allow the unloaded soil to accumulate below the avoidance gap. Subsequently, the soil on both sides of the avoidance gap is sorted to form a ramp, which gradually descends from the ground side to the bottom plate. Finally, lay steel bars and pour concrete on the slope of the ramp to form a reinforced concrete slope.

[0059] S3. Trenching. Excavators, trenching machines, and other equipment can access the floor slab of the old underground structure via a ramp. Then, based on the designed location of the underground continuous wall, the floor slab is partially broken away. A guide trench is dug with an excavator, and guide walls are constructed on both sides of the trench width. The trenching machine is then used to deepen the trench, forming a continuous trench.

[0060] While the continuous trench is being dug, mud is cyclically pumped out and injected into the dug continuous trench. The specific gravity of the mud circulating in the continuous trench is controlled to be 1.1-1.25 g / cm³, and the viscosity of the circulating mud is controlled to be 25-30 Pa·s. Preferably, the specific gravity of the mud circulating in the continuous trench is controlled to be 1.2 g / cm³, and the viscosity of the circulating mud is controlled to be 28 Pa·s. After the continuous trench is completed, the specific gravity of the mud circulating in the continuous trench is controlled to be 1.1-1.15 g / cm³, and preferably, the specific gravity of the mud circulating in the continuous trench is controlled to be 1.1 g / cm³.

[0061] S4. Lower the rebar cage. Use a crane to lower the rebar cage into the continuous trough. The upper end of the rebar cage is the rebar joint, which is covered with a protective sleeve. The rebar joint is composed of the upper ends of several vertical rebars. In this embodiment, the protective sleeve can be either a plastic sleeve or a rubber sleeve. The protective sleeve is placed on the upper ends of the vertical rebars, and the protective sleeve is placed corresponding to the upper ends of the vertical rebars.

[0062] S5. Concrete pouring. Pour concrete into the continuous trench. Once the concrete solidifies, it forms an underground continuous wall. In this embodiment, the underground continuous wall located within the old underground structure wall is a central partition wall, primarily used to partition and isolate the area within the water-blocking exterior wall.

[0063] S6. Connect the ground and wall.

[0064] S6.1. Remove the guide wall and bottom plate on one side of the formed underground continuous wall, and chisel away the upper part of the formed underground continuous wall to expose the steel bar joints; then, remove each protective cover.

[0065] S6.2. Install a support formwork on the upper side of the completed diaphragm wall. Braces can be provided on the guide wall and base plate to support the support formwork. Simultaneously, install a steel cage within the support formwork, securing the lower side of the steel cage to the steel bar joints within the support formwork. In this embodiment, the lower side of the steel cage within the support formwork is welded to the steel bar joints. Concrete is then poured into the support formwork, raising the diaphragm wall to the ground level. Construction of the diaphragm wall is complete once the concrete solidifies and stabilizes.

[0066] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for constructing an underground continuous wall in an existing underground structure, characterized by: The following steps are included: S1. Dewatering operation: lowering the groundwater level around the old underground structure to below the floor; S2: Slope reduction operation: remove the top plate of the old underground structure and construct a ramp from the ground to the bottom plate for mechanical equipment to enter; S3: Trenching operation: according to the designed position of underground continuous wall, remove the local bottom plate and dig the continuous trench; S4, lowering the steel cage into the continuous trough; S5, pouring operation, pouring concrete into the continuous trough, and forming an underground continuous wall after the concrete solidifies; S6. Raise the ground wall by installing a support formwork on the upper side of the formed underground continuous wall, setting a steel cage inside the support formwork, and then pouring concrete into the support formwork to raise the underground continuous wall to the ground level; In step S1, a light wellpoint dewatering device is installed on one side of the old underground structure, and a water-blocking outer wall is installed on the other sides of the old underground structure. The light wellpoint dewatering device includes a well pipe, and the lower end of the well pipe and the lower side of the water-blocking outer wall are both lower than the bottom plate; In S2, the upper part of one side of the old underground structure wall is demolished, and an avoidance gap is formed on the wall. Then, the soil outside the avoidance gap is unloaded and accumulated under the avoidance gap. Subsequently, the soil on both sides of the avoidance gap is sorted and a ramp is formed.

2. The method for constructing an underground continuous wall in an existing underground structure according to claim 1, characterized in that: The slope surface of the ramp is built with concrete.

3. The method for constructing an underground continuous wall in an existing underground structure according to claim 1, characterized in that: In step S3, while the continuous trench is being dug, mud is cyclically pumped out and injected into the dug continuous trench. The specific gravity of the mud circulating in the continuous trench is controlled to be 1.1-1.25 g / cm³, and the viscosity of the circulating mud is controlled to be 25-30 Pa·s.

4. The method for constructing an underground continuous wall in an existing underground structure according to claim 1, characterized in that: In step S4, the upper end of the steel cage is the steel bar joint; In step S6, the lower side of the steel cage in the support formwork is fixedly connected to the steel bar joint portion.

5. The method for constructing an underground continuous wall in an existing underground structure according to claim 4, characterized in that: In step S4, a protective cover is placed on the joint of the steel bar.

6. The method for constructing an underground continuous wall in an existing underground structure according to claim 1, characterized in that: In step S3, a guide groove is first dug, and guide walls are constructed on both sides of the guide groove in the width direction, and then the guide groove is deepened to form a continuous groove.

7. The method for constructing an underground continuous wall in an existing underground structure according to claim 6, characterized in that: Before installing the support formwork, the guide wall and bottom plate on one side of the formed underground continuous wall are broken down, and the upper part of the formed underground continuous wall is chiseled off.

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