A highly efficient, self-stabilizing foundation pit support structure and construction method thereof

Abstract

The present invention discloses an efficient, self-stabilizing foundation pit support structure and a construction method thereof. The support structure includes a foundation pit continuous wall and a support wall, wherein the foundation pit continuous wall is arranged around the foundation pit, and the foundation pit continuous wall is set as a polygonal structure according to the shape of the foundation pit, and a plurality of support walls are arranged around the outer periphery of the polygonal foundation pit continuous wall. The support frame in the support wall is connected to the steel cage in the foundation pit continuous wall. After the foundation pit continuous wall is poured with concrete, the support wall and the foundation pit continuous wall at the location are formed into an integrated structure, and the thickness of the support wall is the same as that of the foundation pit continuous wall. Beneficial effect: The back pressure effect of the deadweight of the soil above the inclined support wall on the support wall surface is utilized to limit the lifting of the inclined support wall and the deflection and deformation of the foundation pit continuous wall into the foundation pit, that is, the self-stabilizing effect. The conventional in-pit support system can be eliminated, and the efficiency of earth excavation in the foundation pit is greatly improved and the construction period can be significantly saved.

Description

Technical Field

[0001] The invention relates to a supporting structure and a construction method thereof, and in particular to a highly efficient, self-stabilizing foundation pit supporting structure and a construction method thereof. Background Art

[0002] In recent years, with the continuous acceleration of urbanization, underground infrastructure construction has entered a new climax. Foundation pit support plays an irreplaceable role as an important structural system to ensure the safety of underground construction. However, the current foundation pit support system usually adopts the form of vertical support structure plus horizontal internal support. The dense horizontal supports in the pit make the working surface of earth excavation very limited, which greatly affects the work efficiency of earth excavation, thereby extending the construction period. More importantly, the swinging operation of the excavator is easy to knock down the internal support rods, which may cause injuries to construction personnel and even cause accidents such as partial collapse of the foundation pit. Therefore, it is necessary to develop a new foundation pit support structure and construction method that can improve the efficiency of foundation pit excavation and ensure the overall stability and safety of the foundation pit. The present invention is committed to providing such a solution, that is, an efficient and self-stabilizing foundation pit support structure and construction method. Summary of the invention

[0003] The purpose of the present invention is to provide an efficient, self-stabilizing foundation pit support structure without support in the pit and a construction method thereof, so as to solve the problem that the dense supports in the pit restrict the excavation working surface of the excavator and prolong the construction period in most foundation pit construction processes.

[0004] The efficient and self-stabilizing foundation pit support structure provided by the present invention comprises a foundation pit continuous wall and a supporting wall, wherein the foundation pit continuous wall is arranged around the periphery of the foundation pit, the foundation pit continuous wall is arranged as a polygonal structure according to the shape of the foundation pit, and several supporting walls are arranged around the outer periphery of the polygonal foundation pit continuous wall.

[0005] The supporting frame in the supporting wall is connected to the steel cage in the foundation pit continuous wall. After the foundation pit continuous wall is poured with concrete, the supporting wall and the foundation pit continuous wall at its location form an integrated structure, and the thickness of the supporting wall is the same as that of the foundation pit continuous wall.

[0006] The supporting wall is an inclined wall, and the inclination angle θ of the supporting wall is not greater than 30°, θ is the angle between the supporting wall and the plumb plane, the supporting walls are symmetrically arranged on either side of the foundation pit, the axis of symmetry is the central axis of that side of the foundation pit, and the supporting walls on one side of the central axis of the continuous wall of the foundation pit are parallel to each other, the distance between the top of the supporting wall adjacent to the corner of the foundation pit and the corner of the foundation pit is not greater than 0.5B, the distance between the top of the supporting wall adjacent to the axis of symmetry and the axis of symmetry is not less than 4B, B is the overhang length of the supporting wall, B is not less than 1.5m.

[0007] The adjacent supporting walls on one side of the central axis of the foundation pit continuous wall are arranged in an equal spacing or gradually increased density close to the symmetry axis. When the foundation pit is a first-level foundation pit, 20m≤S≤30m; when the foundation pit is a second-level foundation pit, 30m<S≤40m; when the foundation pit is a third-level foundation pit, 40m<S≤60m, and S is the supporting wall spacing.

[0008] The supporting frame in the supporting wall includes a guide frame, transverse steel and vertical steel, wherein the length and slope of the guide frame correspond to the length and slope of the supporting wall, the guide frame is composed of two corresponding steel plates, the top ends of the two corresponding steel plates are penetrated with tie rods for connection, the transverse steel is inserted in the gap between the two corresponding steel plates, the transverse steel is assembled in several layers according to the set spacing, the front ends of the transverse steel are connected to the steel cage in the continuous wall of the foundation pit at the location, the vertical steel is composed of several steel sections welded end to end to form a complete long strip of steel that runs through the depth range of the supporting wall, the vertical steel is inserted into the supporting wall at the rear end of the transverse steel, close to the transverse steel and the guide frame, the vertical steel is parallel to the guide frame, after the continuous wall of the foundation pit is poured with concrete, the supporting wall and the continuous wall of the foundation pit at the location form an integrated structure.

[0009] The invention provides a construction method for a highly efficient, self-stabilizing foundation pit support structure, which comprises the following steps:

[0010] Step 1: At the designed location of the foundation pit continuous wall, a trenching machine is used to perform trenching construction of the foundation pit continuous wall trench section;

[0011] Step 2: sink the special steel cage into the continuous wall groove section of the foundation pit. The steel cage is pre-welded with an inclined track to facilitate the subsequent support wall construction. The inclined track is composed of two parallel thick steel bars with a diameter of 35 mm. The inclination angle of the inclined track is the same as the inclination angle of the support wall. At the same time, the MJS method is used to construct the support wall at the designated position on the outside of the continuous wall of the foundation pit in the groove section; the overhang length B of the support wall is not less than 1.5m; the thickness of the support wall is the same as the thickness of the continuous wall of the foundation pit, the top of the support wall is flush with the top of the continuous wall of the foundation pit, and the bottom of the support wall reaches at least the excavation depth D of the foundation pit. If the deformation control level of the foundation pit is high, the bottom of the support wall should be further extended downward by 0.33D, and the inclination angle θ of the support wall is not greater than 30°, θ is the angle between the support wall and the plumb plane;

[0012] Step 3, embed the front end of the transverse steel as the support wall skeleton into the inclined track on the steel cage, and use the brake push rod to push the transverse steel into the wall of the support wall in a set equal spacing. The buried depth of the last sunken transverse steel shall not exceed 0.5 times the spacing between adjacent transverse steels. The first transverse steel lowered is a special steel, and its front end is connected to the steel cage of the foundation pit continuous wall at the location. The rear end of the transverse steel is welded to the two steel plates that form the guide frame. Half of the two steel plates are mounted on the transverse steel, and the other half is suspended as a track for the subsequent vertical steel lowering. The guide frame overlaps the vertical steel to form a whole. The two steel plates of the guide frame are 0.5m above the ground. The upper ends of the two steel plates are perforated. Steel bars with a length exceeding the thickness of the supporting wall are passed through the circular holes on the upper ends of the two steel plates to prevent the two steel plates from sinking into the cement slurry of the supporting wall.

[0013] Step 4: lower the vertical steel section into the wall of the supporting wall where the transverse steel section is far away from the end of the steel cage of the foundation pit continuous wall. When the first vertical steel section is not fully inserted into the wall of the supporting wall, connect the next vertical steel section to it end to end by welding. Repeat this operation. After several vertical steel sections are welded, a complete "longitudinal steel section" that runs through the depth range of the supporting wall is formed. While lowering the vertical steel section, pour concrete into the groove excavated in step 1 to complete the construction of the foundation pit continuous wall groove section at this position. At this point, a section of foundation pit continuous wall + supporting wall combination construction is completed.

[0014] Step 5, then proceed with the construction of the foundation pit continuous wall of other trench sections, and repeat the above steps 1 to 4 in the next trench section with the supporting wall, so as to perform the combined construction of the foundation pit continuous wall and the supporting wall again;

[0015] Step 6: After completing the construction of all foundation pit continuous walls and supporting walls, the foundation pit dewatering excavation construction can be carried out.

[0016] The MJS method in step 2 is also known as the all-round high-pressure jetting method. It is a construction method that can perform 360° all-round foundation drilling and spraying. It can form an underground continuous wall with any inclination angle and has minimal disturbance to the surrounding environment and foundation.

[0017] Beneficial effects of the present invention:

[0018] The efficient, self-stabilizing foundation pit support structure and its construction method provided by the present invention form an integrated structure with the foundation pit continuous wall and the inclined support wall by arranging a series of inclined support walls on the outside of the foundation pit, and utilizing the counter-pressure effect of the deadweight of the soil above the inclined support wall on the supporting wall surface, thereby limiting the lifting of the inclined support wall and the deflection and deformation of the foundation pit continuous wall into the foundation pit, that is, the self-stabilizing effect. The present invention utilizes the self-stabilizing effect of the integrated structure of the inclined support wall + the foundation pit continuous wall to eliminate the conventional in-pit support system, thereby greatly improving the efficiency of earth excavation in the foundation pit and significantly saving the construction period. In addition, a triangular structure is formed between the combined walls of the present invention, so that the overall force of the foundation pit is more uniform and more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the supporting structure described in the present invention.

[0020] Figure 2 The figure is a top view of the supporting structure described in the present invention.

[0021] Figure 3 It is a side schematic diagram of the supporting structure described in the present invention.

[0022] Figure 4 It is a schematic diagram of the positions of the foundation pit continuous wall reinforcement cage and the inclined track described in the present invention.

[0023] Figure 5 It is a front view of the foundation pit continuous wall reinforcement cage and the inclined track described in the present invention.

[0024] Figure 6 It is a side view of the foundation pit continuous wall reinforcement cage and the inclined track described in the present invention.

[0025] Figure 7 This is a schematic diagram of the first specially made transverse steel section and the guide frame in the supporting wall described in the present invention.

[0026] Figure 8 This is a schematic diagram of the installation of the transverse steel sections in the supporting wall of the present invention.

[0027] Fig. 9 It is an overall schematic diagram of the foundation pit continuous wall reinforcement cage and the supporting frame inside the supporting wall described in the present invention.

[0028] Fig.10 This is a force diagram of the supporting wall described in the present invention.

[0029] Fig.11 The present invention is a schematic diagram of the construction method of the support structure.

[0030] The annotations in the image above are as follows:

[0031] 1. Foundation pit continuous wall 2. Support wall 3. Steel cage 4. Guide frame 5. Horizontal steel

[0032] 6. Vertical steel 7. Tie rod 8. Inclined track. DETAILED DESCRIPTION

[0033] See also Figures 1 to 11 As shown:

[0034] The efficient and self-stabilizing foundation pit support structure provided by the present invention includes a foundation pit continuous wall 1 and a supporting wall 2, wherein the foundation pit continuous wall 1 is arranged around the periphery of the foundation pit, and the foundation pit continuous wall 1 is set as a polygonal structure according to the shape of the foundation pit, and several supporting walls 2 are arranged around the outer circle of the polygonal foundation pit continuous wall 1.

[0035] The supporting frame in the supporting wall 2 is connected to the steel cage 3 in the foundation pit continuous wall 1. After the foundation pit continuous wall 1 is poured with concrete, the supporting wall 2 and the foundation pit continuous wall 1 at the location form an integrated structure, and the thickness of the supporting wall 2 is the same as that of the foundation pit continuous wall 1.

[0036] The supporting wall 2 is an inclined wall, and the inclination angle θ of the supporting wall 2 is not greater than 30°, θ is the angle between the supporting wall 2 and the plumb plane, the supporting walls 2 are symmetrically arranged on either side of the foundation pit, the axis of symmetry is the central axis of that side of the foundation pit, and the supporting walls 2 on one side of the central axis of the foundation pit continuous wall 1 are parallel to each other, the distance between the top of the supporting wall 2 adjacent to the corner of the foundation pit and the corner of the foundation pit is not greater than 0.5B, the distance between the top of the supporting wall 2 adjacent to the axis of symmetry and the axis of symmetry is not less than 4B, B is the overhang length of the supporting wall 2, B is not less than 1.5m.

[0037] The adjacent supporting walls 2 on one side of the central axis of the foundation pit continuous wall 1 are arranged in an equal spacing or gradually denser manner close to the symmetry axis. When the foundation pit is a first-level foundation pit, 20m≤S≤30m; when the foundation pit is a second-level foundation pit, 30m<S≤40m; when the foundation pit is a third-level foundation pit, 40m<S≤60m, and S is the spacing between the supporting walls 2.

[0038] The supporting skeleton in the supporting wall 2 includes a guide frame 4, a transverse steel section 5 and a vertical steel section 6, wherein the length and inclination of the guide frame 4 correspond to the length and inclination of the supporting wall 2, the guide frame 4 is composed of two corresponding steel plates, and the top ends of the two corresponding steel plates are penetrated with a tie rod 7 for connection, the transverse steel section 5 is inserted in the gap between the two corresponding steel plates, and the transverse steel section 5 is assembled with several layers according to the set spacing, and the front ends of the transverse steel sections 5 are connected to the steel cage 3 in the foundation pit continuous wall 1 at the location, and the vertical steel section 6 is a complete long strip of steel section composed of several steel sections welded end to end, which runs through the depth range of the supporting wall, and the vertical steel section 6 is inserted into the supporting wall 2 at the rear end of the transverse steel section 5, close to the transverse steel section 5 and the guide frame 4, and the vertical steel section 6 is parallel to the guide frame 4. After the foundation pit continuous wall 1 is poured with concrete, the supporting wall 2 and the foundation pit continuous wall 1 at the location form an integrated structure.

[0039] The working principle of the efficient and self-stabilizing foundation pit support structure provided by the present invention (see Fig.10 ):

[0040] During the excavation process in the foundation pit, as the soil on the inner side of the foundation pit used to support the foundation pit continuous wall 1 continues to decrease, the foundation pit continuous wall 1 will deflect around its bottom into the foundation pit. Since the supporting wall 2 and the foundation pit continuous wall 1 are a whole in the present invention, when the foundation pit continuous wall 1 deflects into the foundation pit, it will drive the supporting wall 2 to rotate together, and the deadweight of the soil above the supporting wall 2 will exert a counter-pressure on the wall surface of the supporting wall 2. Under the action of the soil pressure F1, the supporting wall 2 has the effect of driving the foundation pit continuous wall 1 to deflect in the opposite direction toward the outside of the foundation pit, which has a self-stabilizing effect on the foundation pit support structure; on the other hand, the friction resistance F2 of the soil on both sides of the supporting wall 2 to its wall surface can also limit the overall structure of the supporting wall 2 and the foundation pit continuous wall 1 from deflecting into the foundation pit; furthermore, the overall structure composed of the supporting wall 2 and the foundation pit continuous wall 1 has a larger cross-sectional inertia moment and has a stronger anti-deflection and anti-bending ability. Due to the self-stabilizing effect of the integrated structure of the inclined support wall 2 + the foundation pit continuous wall 1 of the present invention, the conventional in-pit support system can be eliminated during the foundation pit construction, thereby greatly improving the efficiency of earth excavation in the foundation pit and significantly saving the construction period.

[0041] The invention provides a construction method for a highly efficient, self-stabilizing foundation pit support structure, which comprises the following steps:

[0042] Step 1: At the designed location of the foundation pit continuous wall 1, a trenching machine is used to perform trenching construction of the trench section of the foundation pit continuous wall 1;

[0043] Step 2, sink the special steel cage 3 into the groove section of the foundation pit continuous wall 1, and the steel cage 3 is pre-welded with an inclined track 8 to facilitate the subsequent construction of the supporting wall 2. The inclined track 8 is composed of two parallel thick steel bars with a diameter of 35 mm. The inclination angle of the inclined track 8 is the same as the inclination angle of the supporting wall 2. At the same time, the MJS method is used to construct the wall of the supporting wall 2 at the designated position on the outside of the foundation pit continuous wall 1 in the groove section; wherein the overhang length B of the supporting wall 2 is not less than 1.5m; the thickness of the supporting wall 2 is the same as the thickness of the foundation pit continuous wall 1, the top of the supporting wall 2 is flush with the top of the foundation pit continuous wall 1, and the bottom of the supporting wall 2 reaches at least the foundation pit excavation depth D. If the foundation pit deformation control level is high, the bottom of the supporting wall 2 should be further extended downward by 0.33D, and the inclination angle θ of the supporting wall 2 is not greater than 30°, θ is the angle between the supporting wall 2 and the plumb plane;

[0044] Step 3, embed the front end of the transverse steel 5 serving as the skeleton of the supporting wall 2 into the inclined track 8 on the steel cage 3, and use the brake push rod to push the transverse steel 5 into the wall of the supporting wall 2 in a set equal spacing manner. The buried depth of the transverse steel 5 finally sunk shall not exceed 0.5 times the spacing between adjacent transverse steels 5. The first transverse steel 5 lowered is a special steel, and its front end is connected to the steel cage 3 of the continuous wall 1 of the foundation pit at the location. The rear end of the transverse steel 5 is welded to the two steel plates that constitute the guide frame 4. Half of the two steel plates are mounted on the transverse steel 5, and the other half is suspended as a track for the subsequent lowering of the vertical steel 6. The guide frame 4 is overlapped with the vertical steel 6 to form a whole. The two steel plates of the guide frame 4 are 0.5m above the ground. The upper ends of the two steel plates are perforated. Rebars with a length exceeding the thickness of the supporting wall 2 are passed through the circular holes on the upper ends of the two steel plates to prevent the two steel plates from sinking into the cement slurry of the supporting wall 2.

[0045] Step 4, lower the vertical steel 6 into the wall of the supporting wall 2 where the transverse steel 5 is far away from the end of the steel cage 3 of the foundation pit continuous wall 1. When the first vertical steel 6 is not completely inserted into the wall of the supporting wall 2, connect the next vertical steel 6 to it end to end by welding, and repeat this operation. After several vertical steels 6 are welded, a complete "longitudinal steel" that runs through the depth range of the supporting wall 2 is formed; while lowering the vertical steel 6, pour concrete into the groove excavated in step 1 to complete the construction of the groove section of the foundation pit continuous wall 1 at this position; thus, a section of the foundation pit continuous wall 1 + supporting wall 2 combined construction is completed;

[0046] Step 5, then proceed with the construction of the foundation pit continuous wall 1 of other trench sections, and repeat the above steps 1 to 4 in the next trench section with the supporting wall 2, so as to perform the combined construction of the foundation pit continuous wall 1 and the supporting wall 2 again;

[0047] Step 6: After completing the construction of all foundation pit continuous walls 1 and supporting walls 2, the foundation pit dewatering excavation construction can be carried out.

[0048] The MJS method in step 2 is also known as the all-round high-pressure jetting method. It is a construction method that can perform 360° all-round foundation drilling and spraying. It can form an underground continuous wall with any inclination angle and has minimal disturbance to the surrounding environment and foundation.

Claims

1. An efficient and self-stabilizing foundation pit support structure, comprising a foundation pit continuous wall and a supporting wall, wherein the foundation pit continuous wall is arranged around the foundation pit, and the foundation pit continuous wall is set as a polygonal structure according to the shape of the foundation pit, and a plurality of supporting walls are arranged around the outer periphery of the polygonal foundation pit continuous wall; the supporting skeleton in the supporting wall is connected to the steel cage in the foundation pit continuous wall, and after the foundation pit continuous wall is poured with concrete, the supporting wall and the foundation pit continuous wall at the location are formed into an integrated structure, and the thickness of the supporting wall is the same as the thickness of the foundation pit continuous wall; the supporting wall is an inclined wall, and the inclination angle θ of the supporting wall is not greater than 30°, θ is the angle between the supporting wall and the plumb plane, the supporting walls are symmetrically arranged on either side of the foundation pit, the axis of symmetry is the central axis of the side of the foundation pit, and the supporting walls on one side of the central axis of the foundation pit continuous wall are parallel to each other, the distance between the top of the supporting wall adjacent to the corner of the foundation pit and the corner of the foundation pit is not greater than 0.5B, and the distance between the top of the supporting wall adjacent to the axis of symmetry and the axis of symmetry is not less than 4B, B is the overhang length of the supporting wall, and B is not less than 1.5m, characterized in that: The supporting frame in the supporting wall includes a guide frame, transverse steel and vertical steel, wherein the length and slope of the guide frame correspond to the length and slope of the supporting wall, the guide frame is composed of two corresponding steel plates, and the tops of the two corresponding steel plates are penetrated with tie rods for connection, the transverse steel is inserted in the gap between the two corresponding steel plates, and the transverse steel is assembled in several layers according to the set spacing, and the front ends of the transverse steel are connected to the steel cage in the continuous wall of the foundation pit at the location, the vertical steel is composed of several steel sections welded end to end to form a complete long strip of steel that runs through the depth range of the supporting wall, the vertical steel is inserted into the supporting wall at the rear end of the transverse steel, close to the transverse steel and the guide frame, and the vertical steel is parallel to the guide frame. After the continuous wall of the foundation pit is poured with concrete, the supporting wall and the continuous wall of the foundation pit at the location form an integrated structure.

2. A construction method of an efficient, self-stabilizing foundation pit support structure, characterized in that: The method comprises the following steps: Step 1: At the designed location of the foundation pit continuous wall, a trenching machine is used to perform trenching construction of the foundation pit continuous wall trench section; Step 2: sink the special steel cage into the continuous wall groove section of the foundation pit. The steel cage is pre-welded with an inclined track to facilitate the subsequent support wall construction. The inclined track is composed of two parallel thick steel bars with a diameter of 35 mm. The inclination angle of the inclined track is the same as the inclination angle of the support wall. At the same time, the MJS method is used to construct the support wall at the designated position on the outside of the continuous wall of the foundation pit in the groove section; the overhang length B of the support wall is not less than 1.5m; the thickness of the support wall is the same as the thickness of the continuous wall of the foundation pit, the top of the support wall is flush with the top of the continuous wall of the foundation pit, and the bottom of the support wall reaches at least the excavation depth D of the foundation pit. If the deformation control level of the foundation pit is high, the bottom of the support wall should be further extended downward by 0.33D, and the inclination angle θ of the support wall is not greater than 30°, θ is the angle between the support wall and the plumb plane; Step 3, embed the front end of the transverse steel as the support wall skeleton into the inclined track on the steel cage, and use the brake push rod to push the transverse steel into the wall of the support wall in a set equal spacing. The buried depth of the last sunken transverse steel shall not exceed 0.5 times the spacing between adjacent transverse steels. The first transverse steel lowered is a special steel, and its front end is connected to the steel cage of the foundation pit continuous wall at the location. The rear end of the transverse steel is welded to the two steel plates that form the guide frame. Half of the two steel plates are mounted on the transverse steel, and the other half is suspended as a track for the subsequent vertical steel lowering. The guide frame overlaps the vertical steel to form a whole. The two steel plates of the guide frame are 0.5m above the ground. The upper ends of the two steel plates are perforated. Steel bars with a length exceeding the thickness of the supporting wall are passed through the circular holes on the upper ends of the two steel plates to prevent the two steel plates from sinking into the cement slurry of the supporting wall. Step 4: lower the vertical steel section into the wall of the supporting wall where the transverse steel section is far away from the end of the steel cage of the foundation pit continuous wall. When the first vertical steel section is not fully inserted into the wall of the supporting wall, connect the next vertical steel section to it end to end by welding. Repeat this operation. After several vertical steel sections are welded, a complete "longitudinal steel section" that runs through the depth range of the supporting wall is formed. While lowering the vertical steel section, pour concrete into the groove excavated in step 1 to complete the construction of the foundation pit continuous wall groove section at this position. At this point, a section of foundation pit continuous wall + supporting wall combination construction is completed. Step 5, then proceed with the construction of the foundation pit continuous wall of other trench sections, and repeat the above steps 1 to 4 in the next trench section with the supporting wall, so as to perform the combined construction of the foundation pit continuous wall and the supporting wall again; Step 6: After completing the construction of all foundation pit continuous walls and supporting walls, the foundation pit dewatering excavation construction can be carried out.

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