Method for breaking through foundation pit and existing station structure

Abstract

The invention discloses a foundation pit and existing station structure break-through method. In order to solve the problem that normal use of an existing building, especially a surface road, can be influenced when an existing foundation pit and an existing building are communicated by an existing dredging method which generally adopts an open excavation and capping mode, the invention designs a foundation pit and existing station structure dredging method which comprises the following steps: excavating a foundation pit and building a cast-in-place pile; a reserved area needing to be cut and broken through is reserved on the cast-in-place pile face needing to be broken through with the existing station; horizontally cutting the cast-in-place pile and the upper boundary of the existing structure according to the reserved area, and inserting a steel plate for penetration; vertically cutting two side boundaries and inserting the steel plate; the cast-in-place pile in the reserved area is cut and hoisted out; the soil body is excavated to a wall structure of the existing station; breaking a wall structure of the existing station; and a connecting wall, an expansion joint and a waterproof joint are built in the opened channel. When the method is used for underground excavation, the soil layer above the channel does not need to be additionally reinforced any more, the nature of the soil body is protected, and meanwhile the influence of machining on an existing road is reduced.

Description

Technical Field

[0001] The present invention relates to the field of deep foundation pit construction of civil engineering buildings, and in particular to a method for connecting a foundation pit with an existing station structure. Background Art

[0002] The excavation of the foundation pit often leaves a certain distance of soil between the existing station structure, and retains the soil and the surface above the existing station for vehicles and pedestrians to pass. After the excavation of the foundation pit is completed, the foundation pit needs to be connected with the existing station structure to establish a connecting passage to meet the needs of subway transfers. In order to ensure the safety and normal use of surface structures and roads, it is necessary to develop a way to open it up without interfering with the ground. Summary of the invention

[0003] The present invention is aimed at the existing opening method which usually adopts the method of open excavation and covering, which will affect the normal use of the existing buildings, especially the surface roads when connecting the existing foundation pit and the existing buildings. For this reason, the method used in the present invention is designed.

[0004] The present invention provides a method for connecting a foundation pit with an existing station structure, comprising the following steps: Step 1: excavate the foundation pit and build cast-in-place piles, and reserve a reserved area that needs to be cut and opened on the cast-in-place pile surface that needs to be opened with the existing station; Step 2: According to the reserved area, horizontally cut the cast-in-place piles and the upper boundary of the existing structure and insert the steel plate through; Step 3: vertically cut the borders on both sides and insert the steel plates; Step 4: Cut and hoist the cast-in-place piles in the reserved area; Step 5: excavate the soil to the wall structure of the existing station; Step 6: Demolish the existing station wall structure; Step seven, build connecting walls, expansion joints and waterproof joints in the opened passage.

[0005] Preferably, the hole produced by the horizontal cutting in step 2 has a thickness greater than or equal to 20 mm, a width greater than the reserved area and extends to the left and right to exceed the adjacent cast-in-place piles in the reserved area; In step 3, the holes formed by vertical cutting are arranged in the gaps formed between the cast-in-place piles; The steel plates used are usually between 20mm and 35mm thick, and are selected according to the actual depth of the channel. The steel plates are placed on the cast-in-place piles and the walls of the existing station. The vertically cut holes and horizontally cut hole-shaped materials have a T-shaped structure. When the inner soil layer wrapped by the channel is excavated, the vertically set steel plates can prevent the soil layers on both sides from sliding in and can also serve as a supporting structure.

[0006] If necessary, the support of the vertical steel plates can be strengthened by driving in additional vertical steel sections.

[0007] Preferably, the thickness of the horizontal cut hole is between 40 mm and 200 mm, and a hollow steel pipe is implanted from the foundation pit to the existing station on the top of the horizontally implanted steel plate, and the size of the steel pipe is selected according to the size of the horizontal cut hole; At least one working hole is set on the hollow steel pipe at an interval of 150mm, and at least 4 rows of working holes are set along the circumference of the steel pipe; A hollow steel pipe is set at every 300mm horizontal interval; After the hollow steel pipe is inserted into the soil, cement is injected into it through the end, and the cement is sprayed out through the working hole to form a cement nail structure.

[0008] Preferably, the thickness of the hole produced by the horizontal cutting is greater than or equal to 100 mm, and a first steel section is embedded in the hole, and the first steel section wraps the structure punched into the hole; The second steel section is embedded along the longitudinal edge of the steel plate, the second steel section wraps the structure punched into the hole, and the end portion is welded to the first steel section.

[0009] Preferably, the cutting point on the cast-in-place pile in step 4 is a horizontal cutting hole used when the steel plate is driven horizontally; The lower cutting point is greater in vertical height than the lower edge of the steel plate driven vertically, and the spacing is greater than 200mm.

[0010] The substantial effect of the present invention is that when using this method for underground excavation, there is no need to perform additional reinforcement on the soil layer above the passage, which is beneficial to protecting the natural nature of the soil and reducing the impact of processing on existing roads. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The overall flow chart of the present invention; Figure 2 Sectional view between foundation pit and existing station; Figure 3 Cross-section view of cutting a horizontal steel plate and punching a hole; Figure 4 The cross-section between the foundation pit and the existing station after the steel plate is driven in; Figure 5 Front view of the foundation pit side when cutting the horizontal steel plate and punching the hole; Figure 6 Front view of the foundation pit after the horizontal steel plate is driven in; Figure 7 Front view of the foundation pit after the vertical steel plate is driven in; Figure 8 Cut and hoist the bored piles out one by one, and then take a front view of the foundation pit side; Fig. 9 Front view of the foundation pit side when excavating the soil; Fig.10 The front view of the foundation pit side when the existing station structure is exposed; Fig.11 Front view of the foundation pit side when breaking the existing station wall; Fig.12 Front view of the foundation pit side when the passage is established; In the figure: 10, soil, 100, existing station, 201, horizontal support, 202, horizontal cutting hole, 203, steel plate, 204, cast-in-place pile, 205, supporting purlin, 206, suspended cast-in-place pile section, 207, station wall, 208, connecting wall. DETAILED DESCRIPTION

[0012] The technical solution of the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0013] Example 1 The method for connecting the foundation pit with the existing station structure includes the following steps: Step 1: excavate a foundation pit and build cast-in-place piles, and reserve a reserved area that needs to be cut and opened on the cast-in-place pile surface that needs to be opened with the existing station 100.

[0014] like Figure 1 As shown, the foundation pit is built in accordance with the normal way of building the foundation pit retaining wall 200, using a retaining wall formed by bored piles 204 formed from the ground surface, excavating the foundation pit soil and sequentially constructing the supporting purlin 205 and the horizontal support 201. In the figure, the existing soil is marked with a mark 10.

[0015] Step 2, such as Figure 2 , Figure 3 , Figure 5 and Figure 6 As shown, according to the reserved area, the cast-in-place piles and the upper boundary of the existing structure (at Figure 2 and Figure 5 A horizontal hole is cut at the position marked by the dotted line 202, and a horizontal steel plate 203 is inserted through it (estimated thickness 30-50 mm, selected according to actual working conditions).

[0016] Choose whether to include the steel crown beam at the end according to the actual situation. If not, the thickness of the quality control is equal to the thickness of the inserted steel plate. The width is larger than the reserved area and extends to the left and right to exceed the adjacent cast-in-place piles in the reserved area.

[0017] If it is determined that the soil is easily disturbed and needs a certain degree of reinforcement, the horizontal holes can be opened before the steel plates are driven in, and the holes can be expanded upward and downward to facilitate the driving of cement nails for reinforcement. Cement nails are formed by steel pipes. Hollow steel pipes are implanted along the top of the steel plate from the foundation pit to the existing station, and cement is injected into the hollow steel pipes. After solidification, the steel pipes and cement overflowing from the holes will form cement nails to reduce soil sliding.

[0018] At least one working hole is set on the hollow steel pipe at an interval of 150mm, and at least 4 rows of working holes are set along the circumference of the steel pipe; one hollow steel pipe is set at a horizontal interval of every 300mm; After the hollow steel pipe is inserted into the soil, cement is injected into it through the end, and the cement is sprayed out through the working hole to form a cement nail structure.

[0019] The solution of driving hollow steel pipes requires wrapping steel sections or cap beams on the horizontal holes to prevent soil from flowing through the gaps formed by the horizontal holes and the steel plates and steel pipes in the event of water seepage.

[0020] Before driving in the steel section, the depth of the selected steel plate is first reduced by the width of one steel section. When the steel sections are driven in at both ends, the steel plate can be stuck in the structure of the steel section.

[0021] If the depth is not reduced, the steel section needs to be placed on the steel plate and welded. If there is a hollow cemented steel pipe, the end of the steel pipe is wrapped with steel section.

[0022] If necessary, a second steel section can be embedded along the longitudinal edge of the steel plate. The second steel section wraps the structure punched into the hole and the end is welded to the first steel section.

[0023] The first steel section and the second steel section can enhance the bending resistance of the steel plate in the horizontal and longitudinal directions.

[0024] Step three, such as Figure 7 As shown, the two side boundaries are cut vertically and vertical steel plates 203 are inserted; the holes formed by the vertical cutting are set in the gaps formed between the cast-in-place piles. The gaps between the cast-in-place piles may not be large enough to be driven directly, so the vertical cutting holes are expanded at equal intervals on the left and right according to the gap as the mid-vertical line.

[0025] And the steel plate does not need to be driven in strictly according to Figure 7 The lower edge is shown adjacent to the supporting purlin 205 .

[0026] Step 4: Figure 8 The cast-in-place pile is cut as shown (the first cast-in-place pile section cut and lifted out is marked with 206, Fig. 9 In order to completely hoist out the 6 cast-in-place piles in the example, the cutting point below the soil is greater than the lower edge of the vertically driven steel plate in vertical height, and the spacing is greater than or equal to 200mm. In this way, the remaining cast-in-place piles and the existing wall can be effectively used to position the vertical steel plate. Cut and hoist them out in sequence. Step 5: Fig.10 As shown, the soil is excavated to the wall 207 structure of the existing station.

[0027] Step 6: Remove the existing station wall structure to form Fig.11 Channel shown.

[0028] Step 7: Build connecting walls 208, expansion joints, and waterproof joints in the opened passage to form Fig.12 Channel shown.

[0029] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for connecting a foundation pit with an existing station structure, characterized in that: The following steps are involved: Step 1: excavate the foundation pit and build cast-in-place piles, and reserve a reserved area that needs to be cut and opened on the cast-in-place pile surface that needs to be opened with the existing station; Step 2: According to the reserved area, horizontally cut the cast-in-place piles and the upper boundary of the existing structure and insert a steel plate through it (estimated thickness 30-50mm); Step 3, vertically cut the borders on both sides and insert the steel plates; Step 4: Cut and hoist the cast-in-place piles in the reserved area; Step 5: excavate the soil to the wall structure of the existing station; Step 6: Demolish the existing station wall structure; Step seven, build connecting walls, expansion joints and waterproof joints in the opened passage.

2. The method for connecting the foundation pit with the existing station structure according to claim 1 is characterized in that: The hole produced by the horizontal cutting in step 2 has a thickness greater than or equal to 20 mm, a width greater than the reserved area and extends to the left and right to exceed the adjacent cast-in-place piles in the reserved area; In step three, the holes formed by vertical cutting are arranged in the gaps formed between the cast-in-place piles.

3. The method for connecting the foundation pit with the existing station structure according to claim 2 is characterized in that: The thickness of the horizontal cutting hole is between 40mm and 200mm, and a hollow steel pipe is implanted from the foundation pit to the existing station on the top of the horizontally implanted steel plate. The size of the steel pipe is selected according to the size of the horizontal cutting hole; At least one working hole is set on the hollow steel pipe at an interval of 150mm, and at least 4 rows of working holes are set along the circumference of the steel pipe; A hollow steel pipe is set at every 300mm horizontal interval; After the hollow steel pipe is inserted into the soil, cement is injected into it through the end, and the cement is sprayed out through the working hole to form a cement nail structure.

4. The method for connecting a foundation pit with an existing station structure according to claim 1 or 2, characterized in that: The thickness of the hole produced by the horizontal cutting is greater than or equal to 100 mm, and the first steel section is embedded in the hole, and the first steel section wraps the structure punched into the hole; The second steel section is embedded along the longitudinal edge of the steel plate, the second steel section wraps the structure punched into the hole, and the end portion is welded to the first steel section.

5. The method for connecting a foundation pit with an existing station structure according to claim 1, characterized in that: The cutting point on the cast-in-place pile in step 4 is the horizontal cutting hole used when the steel plate is driven horizontally; The lower cutting point is greater in vertical height than the lower edge of the steel plate driven vertically, and the spacing is greater than 200mm.

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