A reinforcement structure and construction method for reducing bias pressure of deep foundation pit

Abstract

The present invention discloses a reinforcement structure and construction method for reducing bias pressure in a deep foundation pit, comprising isolation piles located between a foundation pit retaining structure of a high-rise building and the deep foundation pit, the isolation piles comprising a connecting beam, a row of inclined piles and a row of vertical piles, the tops of the inclined piles and the tops of the vertical piles being fixedly connected to the connecting beam, the inclined piles and the vertical piles being arranged in a one-to-one correspondence; the inclined piles and the vertical piles each comprising a pile hole, a pile pipe and a first steel cage, the first steel cage being located within the pile pipe, the pile pipe being located within the pile hole, a first filling layer being provided between the pile hole, the pile pipe and the first steel cage, the connecting beam comprising a horizontally arranged groove, a second steel cage being provided within the groove, the tops of the pile pipes of the straight piles and the tops of the pile pipes of the inclined piles both extending into the second steel cage, and a second filling layer being provided between the groove and the second steel cage. The present invention adopts the reinforcement structure and construction method for reducing bias pressure in a deep foundation pit of the above structure, and utilizes the isolation piles to effectively block the adverse effects of bias pressure generated by the high-rise building on the newly built deep foundation pit.

Description

Technical Field

[0001] The present invention relates to the technical field of deep foundation pit reinforcement, and in particular to a reinforcement structure and a construction method for reducing bias pressure of a deep foundation pit. Background Art

[0002] Most urban subway stations are laid along the main roads of the city. In order to reduce the adverse impact of subway construction on the traffic on the main roads, the stations are mostly arranged on both sides of the main roads. In the central area of ​​the city, there are many high-rise buildings, and the distance between the high-rise buildings and the edges of the main roads is relatively small. The foundation pits of subway stations are mostly 20 to 25 meters, and some foundation pits exceed 30 meters. The depth of the foundation pits of high-rise buildings adjacent to the station foundation pits is mostly smaller than that of the station foundation pits. The retaining structures of the foundation pits of high-rise buildings are mostly cast-in-place piles or ground-connected walls. The loads of high-rise buildings are transmitted to the stratum through the retaining structures, which inevitably produces eccentric pressure on the station. The large eccentric pressure will bring safety hazards to the construction of the foundation pits of neighboring stations. In serious cases, the foundation pits of neighboring stations will be deformed, which will have an adverse effect on the formed structure.

[0003] In view of the above background technology, it is necessary to develop a reinforcement structure and construction method for reducing the bias pressure of deep foundation pits such as station foundation pits. Summary of the Invention

[0004] The purpose of the present invention is to provide a reinforcement structure and construction method for reducing the bias pressure of a deep foundation pit, so as to solve the safety problem of a newly built deep foundation pit adjacent to a high-rise building.

[0005] To achieve the above-mentioned object, the present invention provides a reinforcement structure for reducing bias pressure in a deep foundation pit, comprising isolation piles located between a high-rise building foundation pit retaining structure and a deep foundation pit retaining structure, the isolation piles comprising a connecting beam, a row of inclined piles and a row of vertical piles arranged parallel to the length direction of the high-rise building foundation pit retaining structure, the tops of the inclined piles and the tops of the vertical piles being fixedly connected to the connecting beam, the distance between the inclined piles and the high-rise building foundation pit retaining structure being shorter than the distance between the vertical piles and the high-rise building foundation pit retaining structure, and the inclined piles and the vertical piles being arranged in a one-to-one correspondence;

[0006] The inclined pile and the straight pile both include a pile hole, a pile pipe and a first steel cage, the first steel cage is located in the pile pipe, the pile pipe is located in the pile hole, a first filling layer is provided between the pile hole, the pile pipe and the first steel cage, the pile hole of the straight pile is vertically arranged, an angle is provided between the pile hole of the inclined pile and the pile hole of the straight pile, the connecting beam includes a horizontally arranged groove, a second steel cage is provided in the groove, the top of the pile pipe of the straight pile and the top of the pile pipe of the inclined pile both extend into the second steel cage, and a second filling layer is provided between the groove and the second steel cage.

[0007] Preferably, the interval between two adjacent inclined piles and the interval between two adjacent straight piles are 1 meter.

[0008] Preferably, the first filling layer is a cement slurry layer with a water-cement mass ratio of 1:1, and the second filling layer is concrete.

[0009] Preferably, the first reinforcement cage and the second reinforcement cage both include stirrups and main bars connected to each other, and the main bars are evenly distributed along the periphery of the stirrups.

[0010] Preferably, the pile pipe is a steel pipe. When the length of a single steel pipe is insufficient, butt welding is adopted, and a casing with a length of 0.3m is added at the weld, and both ends of the casing are welded to the outer periphery of the steel pipe.

[0011] Preferably, the pile pipe is provided with grouting holes evenly distributed along its length.

[0012] A construction method for a reinforcement structure for reducing bias pressure in a deep foundation pit comprises the following steps:

[0013] Step 1: High-rise building structural survey: Conduct a site survey to verify the actual location of the deep foundation pit to be constructed and the high-rise building; investigate the structural type, enclosure structure, pile foundation structure and construction status of the high-rise building; explore the actual hydrogeological conditions of the high-rise building and the surrounding engineering environment; investigate the quality of the high-rise building, the hydrogeological conditions of the deep foundation pit to be constructed, and the minimum distance between the deep foundation pit and the high-rise building;

[0014] Step 2: Calculate the stress value of the high-rise building on the stratum: Based on the high-rise building survey data in step 1, calculate the quality of the high-rise building and calculate the stress value of the high-rise building on the stratum based on the pile foundation structure;

[0015] Step 3: Confirm and verify the isolation pile design scheme: Determine the impact of the high-rise building on the deep foundation pit to be constructed based on the stress value of the stratum, design the isolation piles, verify the bearing capacity of the isolation piles, and confirm the reliability of the isolation pile design scheme;

[0016] Step 4: Construction of isolation piles: first level the site and make pile pipes, then construct inclined piles, that is, according to the isolation pile design plan in step 3, drill and clean the inclined piles, install the pile pipes and the first steel cage of the inclined piles, check the grouting pipeline, and implement grouting of the inclined piles to complete the construction of the first filling layer of the inclined piles, and then construct vertical piles, that is, according to the isolation pile design plan in step 3, drill and clean the vertical piles, install the pile pipes and the first steel cage of the vertical piles, check the grouting pipeline, and implement grouting of the vertical piles to complete the construction of the first filling layer of the vertical piles, finally, according to the isolation pile design plan in step 3, excavate the trench for the connecting beam, construct the cushion layer, tie the second steel cage, place the top ends of the pile pipes of the inclined piles and the vertical piles in the second steel cage, set up the formwork, and pour concrete to complete the construction of the second filling layer to form a reliable connecting beam.

[0017] Preferably, the interval drilling method is adopted when drilling the inclined piles and the vertical piles, and the drilling interval is 2 to 5 hole positions.

[0018] Preferably, when the isolation piles conflict with the deep foundation pit retaining structure, the isolation piles are constructed first, and when the deep foundation pit retaining structure is excavated, the conflicting parts are cut off after the ring beams are constructed around the outer periphery of the deep foundation pit retaining structure.

[0019] Therefore, the present invention adopts the above-mentioned structure to reduce the bias pressure of deep foundation pits and the construction method, which solves the safety problem of newly built deep foundation pits adjacent to high-rise buildings. The implementation of isolation piles effectively blocks the bias pressure generated by high-rise buildings from causing adverse effects on newly built deep foundation pits. The structure is stable in stress, the construction process is simple, and the cost is low, with good economic, social and environmental benefits.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of an embodiment of a construction method for a reinforcement structure for reducing bias pressure in a deep foundation pit according to the present invention;

[0022] Figure 2 1 is a schematic structural diagram of an embodiment of an isolation pile in a reinforcement structure for reducing bias pressure in a deep foundation pit according to the present invention;

[0023] Figure 3 is a schematic cross-sectional view of an embodiment of a straight pile in a reinforcement structure for reducing bias pressure in a deep foundation pit according to the present invention;

[0024] Figure 4 1 is a schematic structural diagram of an embodiment of a pile pipe in a reinforcement structure for reducing bias pressure in a deep foundation pit according to the present invention;

[0025] Figure 5 This is a construction flow chart of an embodiment of a straight pile or an inclined pile in a construction method of a reinforcement structure for reducing bias pressure in a deep foundation pit according to the present invention;

[0026] Figure 6 It is a schematic diagram of an embodiment of a ring beam structure when an isolation pile conflicts with a deep foundation pit retaining structure in a construction method of a reinforcement structure for reducing bias pressure of a deep foundation pit according to the present invention;

[0027] Figure 7 Schematic diagram of pile-pipe butt welding in the construction method of the reinforcement structure for reducing bias pressure in a deep foundation pit according to the present invention;

[0028] Figure 8 yes Figure 1 Enlarged view of point A in the middle.

[0029] Reference numerals

[0030] 1. Foundation pit retaining structure for high-rise buildings; 2. Foundation pit retaining structure for deep foundation pits; 3. Isolation piles; 31. Connecting beam; 32. Inclined piles; 33. Vertical piles; 4. Pile pipe; 5. First reinforcement cage; 51. Stirrups; 52. Main reinforcement; 6. Casing; 7. Ring beam; 8. Grouting holes. DETAILED DESCRIPTION

[0031] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0032] A reinforcement structure for reducing bias pressure in a deep foundation pit includes isolation piles 3 located between a high-rise building foundation pit retaining structure 1 and a deep foundation pit retaining structure 2. The isolation piles 3 include a coupling beam 31, a row of inclined piles 32 and a row of vertical piles 33 arranged parallel to the length of the high-rise building foundation pit retaining structure 1. The tops of the inclined piles 32 and the tops of the vertical piles 33 are both fixedly connected to the coupling beam 31. The distance between the inclined piles 32 and the high-rise building foundation pit retaining structure 1 is shorter than the distance between the vertical piles 33 and the high-rise building foundation pit retaining structure 1. The inclined piles 32 and the vertical piles 33 are arranged in a one-to-one correspondence, with a spacing of 1 meter between adjacent inclined piles 32 and adjacent vertical piles 33.

[0033] Both the inclined pile 32 and the vertical pile 33 include a pile hole, a pile pipe 4, and a first reinforcing cage 5. The first reinforcing cage 5 is located within the pile pipe 4, which is then located within the pile hole. A first filler layer is provided between the pile hole, the pile pipe 4, and the first reinforcing cage 5. This first filler layer is a cement slurry layer with a water-cement ratio of 1:1. Grouting holes 8 are evenly distributed along the length of the pile pipe 4. These holes facilitate the flow of the first filler layer into the pile hole, thereby securing the pile hole, the pile pipe 4, and the first reinforcing cage 5. The pile pipe 4 is a steel pipe. When a single steel pipe is insufficient in length, butt welding is used. A 0.3m-long sleeve 6 is added at the weld joint, and both ends of the sleeve 6 are securely welded to the outer periphery of the steel pipe. The pile hole of the vertical pile 33 is vertically arranged, with an angle between the pile holes of the inclined pile 32 and the pile holes of the vertical pile 33. The inclined piles 32 and the vertical piles 33 form a nearly triangular structure, effectively preventing the adverse effects of the bias pressure generated by high-rise buildings on the newly constructed deep foundation pit.

[0034] The coupling beam 31 includes a horizontal groove with a second reinforcement cage positioned within it. The tops of the pile tubes 4 of the straight piles 33 and the inclined piles 32 extend into the second reinforcement cage. A second filler layer of concrete, such as C40 concrete, is located between the groove and the second reinforcement cage. Both the first and second reinforcement cages 5 and 5 comprise interconnected stirrups 51 and main bars 52, with the main bars 52 evenly distributed along the perimeter of the stirrups 51.

[0035] This embodiment is to reduce the eccentric pressure of the foundation pit of Duandian Station on Jinan Metro Line 4. Figure 1 As shown, the construction method of the reinforced structure includes the following steps:

[0036] Step 1: Structural survey of high-rise buildings: Survey the construction site, verify the actual location of the deep foundation pit to be built and the high-rise building, investigate the structural type, enclosure structure, pile foundation structure and construction status of the high-rise building, explore the actual hydrogeology of the high-rise building and the surrounding engineering environment, investigate the quality of the high-rise building, the hydrogeology of the deep foundation pit to be built, and the minimum distance between the deep foundation pit and the high-rise building.

[0037] Duandian Station on Jinan Metro Line 4 is located south of Jingshi Road, running east-west. It features a two-story underground island station. To the southwest of the station is a 28-story commercial and residential building under construction, and to the southeast are the Fortune Times Square parking lot and the six-story Shunhe Hotel parking lot. Exit D of the station is approximately 10 meters from the high-rise building's foundation pit. The station's strata, from top to bottom, consist of miscellaneous fill, silty clay, silty clay, fully weathered diorite, and strongly weathered diorite. The station floor is located in the silty clay layer. The site is primarily composed of Quaternary loose pore water, with aquifers consisting primarily of sand, silty clay, gravel, and pebbles. The water table is buried at a depth of 2.2 to 11.9 meters and at an elevation of 24.3 to 42.0 meters.

[0038] Step 2: Calculate the stress value of the high-rise building on the stratum: According to the high-rise building survey data in step 1, calculate the quality of the high-rise building, and calculate the stress value of the high-rise building on the stratum based on the pile foundation structure.

[0039] Step 3: Confirmation and verification of isolation pile design: Based on the stress value of the high-rise building on the stratum, finite element calculation is used to determine the degree of influence on the deep foundation pit to be built, and isolation pile 3 is designed. The structural diagram of isolation pile 3 is as follows: Figure 2 The bearing capacity of the isolation pile 3 was verified using finite element and mechanical calculation formulas to confirm the reliability of the isolation pile 3 design scheme.

[0040] According to the actual hydrogeology and engineering environment of the project, the design scheme of the isolation pile 3 in this project is as follows: the inclination angle of the pile hole of the inclined pile 32 is 15°, the distance between the top center of the straight pile 33 and the inclined pile 32 is 0.3m, and the distance between two adjacent straight piles 33 and two adjacent inclined piles 32 is 1.0m. The pile pipes 4 of the inclined piles 32 and the straight piles 33 are both Φ219×16 steel pipes, and the steel pipes are provided with grouting holes 8 evenly distributed along their length. In this embodiment, the grouting holes 8 are provided with two staggered rows. The main reinforcement 52 of the first steel cage 5 is 4×Φ20 threaded steel bar HRB400, and the stirrups 51 are Φ12 round steel. The main reinforcement 52 of the second steel cage is 4×Φ25 threaded steel bar HRB400, the upper and lower horizontal surfaces are 6 steel bars, and the vertical surface is 4 steel bars. The stirrups 51 are Φ12 threaded steel bar HRB400, and the cross section of the connecting beam 31 is 0.8×0.6m. Figure 7As shown, butt welding is used when the length of a single steel pipe is insufficient. The steel pipe can be extended and then hoisted into the hole according to the on-site construction conditions, or it can be lowered for welding. A 0.3m long Φ245×12 casing 6 is added at the weld. The pile pipe 4 made of Φ219 steel pipe is processed with a welding groove of 8×45° before welding. The butt weld should be smooth to ensure that the Φ245×12 casing 6 can be inserted smoothly and then welded reliably. The weld height is not less than 5mm, and the grouting hole 8 at the steel pipe joint can be adjusted appropriately.

[0041] Step 4: Construction of Isolation Pile 3: First, the site is leveled and the pile pipe 4 is fabricated. Next, the inclined pile 32 is constructed. Specifically, according to the isolation pile design in Step 3, the inclined pile 32 is drilled and cleaned, the pile pipe 4 and first reinforcement cage 5 of the inclined pile 32 are installed, the grouting pipeline is inspected, and grouting is performed on the inclined pile 32 to complete the construction of the first filling layer of the inclined pile 32. Then, the vertical pile 33 is constructed. Specifically, according to the isolation pile 3 design in Step 3, the vertical pile 33 is drilled and cleaned, the pile pipe and first reinforcement cage 5 of the vertical pile 33 are installed, the grouting pipeline is inspected, and grouting is performed on the vertical pile 33 to complete the construction of the first filling layer of the vertical pile 33. Both the inclined pile 32 and the vertical pile 33 are drilled using the interval drilling method, with 2 to 5 holes spaced apart. Finally, according to the design scheme of the isolation pile 3 in step three, the trench for the connecting beam 31 is excavated, the cushion layer is constructed, and the second reinforcement cage is tied. The top ends of the pile pipes 4 of the inclined piles 32 and the vertical piles 33 are placed in the second reinforcement cage, the formwork is set up, and concrete is poured to complete the construction of the second filling layer to form a reliable connecting beam 31.

[0042] During grouting in this embodiment, the water-cement ratio of the cement slurry is 1:1 (mass ratio); the grouting pressure is 0.3 MPa; the slurry diffusion radius is 0.5 m; the grouting standards are: 1) when the grouting pressure reaches more than 80% of the designed grouting volume; 2) when the grouting pressure reaches the final pressure, the grouting volume has reached 1.5 times the designed grouting volume, and there is no leakage, which can save single-hole grouting.

[0043] In this step, when the isolation pile 3 conflicts with the deep foundation pit retaining structure 2, the isolation pile 3 is constructed first. When the deep foundation pit retaining structure 2 is excavated, the conflicting part is cut off after the ring beam 7 is constructed on the outer periphery of the deep foundation pit retaining structure 2. The ring beam 7 can be used as a component of the retaining structure and optimized and adjusted according to the actual construction conditions.

[0044] Therefore, the present invention adopts the above-mentioned structure to reduce the bias pressure of deep foundation pits and the construction method, which solves the safety problem of newly built deep foundation pits adjacent to high-rise buildings. The implementation of isolation piles effectively blocks the bias pressure generated by high-rise buildings from causing adverse effects on newly built deep foundation pits. The structure is stable in stress, the construction process is simple, and the cost is low, with good economic, social and environmental benefits.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A reinforcement structure for reducing bias pressure in a deep foundation pit, characterized by: The isolation piles include isolation piles located between a high-rise building foundation pit retaining structure and a deep foundation pit retaining structure, the isolation piles include a connecting beam, a row of inclined piles and a row of vertical piles arranged parallel to the length direction of the high-rise building foundation pit retaining structure, the tops of the inclined piles and the tops of the vertical piles are both fixedly connected to the connecting beam, the distance between the inclined piles and the high-rise building foundation pit retaining structure is shorter than the distance between the vertical piles and the high-rise building foundation pit retaining structure, and the inclined piles and the vertical piles are arranged in a one-to-one correspondence; The inclined pile and the straight pile each include a pile hole, a pile pipe, and a first steel cage, the first steel cage being located in the pile pipe, the pile pipe being located in the pile hole, a first filling layer being provided between the pile hole, the pile pipe, and the first steel cage, the pile hole of the straight pile being vertically arranged, an angle being provided between the pile hole of the inclined pile and the pile hole of the straight pile, the connecting beam including a horizontally arranged groove, a second steel cage being provided in the groove, the top of the pile pipe of the straight pile and the top of the pile pipe of the inclined pile both extending into the second steel cage, and a second filling layer being provided between the groove and the second steel cage; The first reinforcement cage and the second reinforcement cage each include stirrups and main bars connected to each other, and the main bars are evenly distributed along the periphery of the stirrups; The pile pipe is a steel pipe. When the length of a single steel pipe is insufficient, butt welding is adopted. A casing with a length of 0.3m is added at the weld, and both ends of the casing are welded to the outer periphery of the steel pipe. A construction method for a reinforced structure for reducing bias pressure in a deep foundation pit comprises the following steps: Step 1: High-rise building structural survey: Conduct a site survey to verify the actual location of the deep foundation pit to be constructed and the high-rise building; investigate the structural type, enclosure structure, pile foundation structure and construction status of the high-rise building; explore the actual hydrogeological conditions of the high-rise building and the surrounding engineering environment; investigate the quality of the high-rise building, the hydrogeological conditions of the deep foundation pit to be constructed, and the minimum distance between the deep foundation pit and the high-rise building; Step 2: Calculate the stress value of the high-rise building on the stratum: Based on the high-rise building survey data in step 1, calculate the quality of the high-rise building and calculate the stress value of the high-rise building on the stratum based on the pile foundation structure; Step 3: Confirm and verify the isolation pile design: Based on the stress value of the high-rise building on the stratum, determine the impact of the deep foundation pit to be built, design the isolation piles, verify the bearing capacity of the isolation piles, and confirm the reliability of the isolation pile design plan; Step 4: Construction of isolation piles: first level the site and make pile pipes, then construct inclined piles, that is, according to the isolation pile design plan in step 3, drill and clean the inclined piles, install the pile pipes and the first steel cage of the inclined piles, check the grouting pipeline, and implement grouting of the inclined piles to complete the construction of the first filling layer of the inclined piles, then construct vertical piles, that is, according to the isolation pile design plan in step 3, drill and clean the vertical piles, install the pile pipes and the first steel cage of the vertical piles, check the grouting pipeline, and implement grouting of the vertical piles to complete the construction of the first filling layer of the vertical piles, finally, according to the isolation pile design plan in step 3, excavate the trench for the connecting beam, construct the cushion layer, tie the second steel cage, place the top ends of the pile pipes of the inclined piles and the vertical piles in the second steel cage, set up the formwork, and pour concrete to complete the construction of the second filling layer to form a reliable connecting beam.

2. The reinforcement structure for reducing bias pressure of a deep foundation pit according to claim 1, characterized in that: There is a 1-meter interval between two adjacent inclined piles and between two adjacent vertical piles.

3. The reinforcement structure for reducing bias pressure of a deep foundation pit according to claim 2, characterized in that: The first filling layer is a cement slurry layer with a water-cement mass ratio of 1:1, and the second filling layer is concrete.

4. The reinforcement structure for reducing bias pressure of a deep foundation pit according to claim 3, characterized in that: The pile pipe is provided with grouting holes evenly distributed along the length direction of the pile pipe.

5. The reinforcement structure for reducing bias pressure of a deep foundation pit according to claim 1, characterized in that: The interval drilling method is adopted when drilling inclined piles and vertical piles, with the drilling intervals of 2 to 5 holes.

6. The reinforcement structure for reducing bias pressure of a deep foundation pit according to claim 2, characterized in that: When the isolation piles conflict with the deep foundation pit retaining structure, the isolation piles are constructed first. When the deep foundation pit retaining structure is excavated, the conflicting parts are cut off after the ring beams are constructed around the outer perimeter of the deep foundation pit retaining structure.

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