CN216739770U - Combined supporting structure for foundation pits on two sides of existing road - Google Patents

Combined supporting structure for foundation pits on two sides of existing road Download PDF

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CN216739770U
CN216739770U CN202220222897.2U CN202220222897U CN216739770U CN 216739770 U CN216739770 U CN 216739770U CN 202220222897 U CN202220222897 U CN 202220222897U CN 216739770 U CN216739770 U CN 216739770U
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pile
supporting
sides
existing road
anchor rod
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姚汾
叶坤
戴凡
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Wuhan Surveying Geotechnical Research Institute Co Ltd of MCC
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Wuhan Surveying Geotechnical Research Institute Co Ltd of MCC
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Abstract

The utility model provides a combined supporting structure for foundation pits on two sides of an existing road. The supporting structure comprises two rows of supporting piles uniformly arranged along the side lines of the foundation pit on two sides of the existing road and at least two rows of prestressed anchor rods oppositely pulled between the supporting piles on the two sides, each side supporting pile is positioned in the area between the side line of the existing road and the side line of the foundation pit excavation, and the pile spacing of each side supporting pile is not more than twice of the pile diameter; the prestressed anchor rod horizontally penetrates through an existing road, and two ends of the prestressed anchor rod are synchronously tensioned and locked on a waist beam of the support pile. The utility model avoids group anchor effect, effectively limits foundation pit displacement, fully utilizes the tensile property of the anchor rod due to the horizontal arrangement of the anchor rod, solves the condition limitation that the anchor rod needs to penetrate through a soft soil layer to reach a relatively hard soil layer through opposite pulling of the anchor rod, saves the use amount of supporting materials and reduces the construction cost; the condition limitation that the anchor rod needs to be matched with grouting for use is solved through anchor rod counter-pulling, and the pollution of grouting to the environment is reduced.

Description

Combined supporting structure for foundation pits on two sides of existing road
Technical Field
The utility model relates to the technical field of foundation pit supporting engineering, in particular to a combined supporting structure for foundation pits on two sides of an existing road.
Background
In recent years, many large real estate developers have several areas together for comprehensive development of real estate projects, and often two areas are located on both sides of an existing town road. In the field of deep foundation pit supporting, an existing road is a key point of foundation pit engineering attention, and the influence of a supporting scheme on the existing road can be considered in the foundation pit supporting scheme.
In the design of a deep foundation pit supporting scheme, the supporting displacement needs to be strictly controlled on the existing road side, a double-row pile supporting form, a supporting pile + supporting form, a supporting pile + anchor bolt supporting form are generally adopted, and the comprehensive calculation and determination are specifically needed according to the excavation depth of a foundation pit and the soil layer condition. However, the foundation pits on both sides of the existing road are usually supported, constructed and excavated separately according to two foundation pits, two construction disturbances are usually required on both sides of the existing road, and ground cracking and uneven settlement are often caused.
Disclosure of Invention
The utility model aims to provide a combined supporting structure for foundation pits on two sides of an existing road, the supporting structure system provided by the utility model can avoid a group anchor effect and effectively limit the displacement of the foundation pit, the anchor rods are horizontally arranged to fully utilize the tensile property of the anchor rods, the condition limitation that the anchor rods need to penetrate through a soft soil layer to reach a relatively hard soil layer can be solved through anchor rod opposite pulling, the using amount of supporting materials is saved, the condition limitation that the anchor rods need to be matched with grouting for use can be solved through anchor rod opposite pulling, the pollution of grouting to the environment is reduced, and the requirement of safe passing of the existing road during foundation pit excavation is met.
In order to achieve the technical purpose, the utility model provides a combined supporting structure for foundation pits on two sides of an existing road, which comprises two rows of supporting piles uniformly arranged along the side lines of the foundation pits on two sides of the existing road and at least two rows of prestressed anchor rods oppositely pulled between the supporting piles on two sides, wherein each side supporting pile is positioned in the area between the side line of the existing road and the excavation side line of the foundation pit, and the pile spacing of each side supporting pile is not more than twice of the pile diameter; the prestressed anchor rods horizontally penetrate through an existing road, two ends of the prestressed anchor rods are synchronously tensioned and locked on a waist beam of the supporting pile, and the distance between the first row of prestressed anchor rods and the crown beam surface of the supporting pile is 2.5-3.5 m.
The utility model has the following excellent technical scheme: the prestressed anchor rods are provided with two rows, each row of prestressed anchor rods is oppositely pulled through waist beams of supporting piles at two sides, the vertical distance between the two rows of prestressed anchor rods is 3-4 m, the horizontal distance is twice of the pile distance, and the locking value of the prestressed anchor rods is 150-560 kpa.
The utility model has the advantages that: the supporting piles are cast-in-situ bored piles, the pile length of each supporting pile is not less than 1.5 times of the excavation depth of foundation pits on two sides of an existing road, the pile diameter of each supporting pile is 0.8-1.2 m, the pile spacing is 1.1-1.6 m, and the pile diameter is not more than 2 times of the pile diameter; the width of the pile top crown beam is 50-100 mm larger than the diameter of the pile, and the height of the pile top crown beam is 0.6-0.8 m.
The utility model has the following excellent technical scheme: the anchor rod is made of steel bars, and the outside of the anchor rod is separated from concrete of the waist beam by a PVC pipe.
Each row of prestressed anchor rods are horizontally arranged, excavation processes of foundation pits at two sides need to be synchronously carried out or successively carried out, but the anchor rods at two sides need to be ensured to be communicated and then synchronously tensioned and locked, construction of each row of prestressed anchor rods sequentially comprises anchor rod body preparation, drilling and anchor rod body placement, waist beam steel bar binding, formwork support, PVC pipe embedding and concrete pouring are carried out on the inner sides of the foundation pits at two sides to complete waist beam construction, finally, anchor rod tensioning and locking construction is carried out, anchor rods at supporting sections at two sides are simultaneously constructed, and a crown beam and a waist beam are integrally poured; before the waist rail is poured, the tension anchor rods are separated from the waist rail concrete by the PVC pipes, and the PVC pipes penetrate through the cross section of the waist rail and are not damaged locally.
The supporting structure system provided by the utility model not only avoids the group anchor effect and effectively limits the displacement of the foundation pit, but also makes full use of the tensile property of the anchor rod in the horizontal arrangement of the anchor rod to save the using amount of supporting materials, solves the condition limitation that the anchor rod needs to penetrate through a soft soil layer to reach a relatively hard soil layer through the opposite pulling of the anchor rod, and reduces the supporting cost; the condition limitation that the anchor rod needs to be matched with grouting for use is solved through anchor rod counter-pulling, the pollution of grouting to the environment is reduced, and the anchor rod counter-pulling device has popularization and application values.
Drawings
FIG. 1 is a floor plan of the present invention;
FIG. 2 is a cross-sectional view of the present invention;
FIG. 3 is a diagram showing the calculation results of the supporting structures of the foundation pits on both sides of the existing road in the embodiment;
in the figure: 1-side line of excavation of foundation pit, 2-supporting pile, 3-crown beam, 4-prestressed anchor rod, 5-existing road, 6-side line of existing road, and 7-waist beam.
Detailed Description
The utility model is further illustrated by the following figures and examples. Fig. 1 to 3 are drawings of embodiments, which are drawn in a simplified manner and are only used for the purpose of clearly and concisely illustrating the embodiments of the present invention. The following claims presented in the drawings are specific to embodiments of the utility model and are not intended to limit the scope of the claimed invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The combined supporting structure for the foundation pits on two sides of the existing road comprises two rows of supporting piles 2 uniformly arranged along the side lines of the foundation pits on two sides of the existing road 5 and two rows of prestressed anchor rods 4 oppositely pulled between the supporting piles on two sides, wherein each side supporting pile 2 is positioned in the area between the side line 6 of the existing road and the side line 1 of the foundation pit excavation, the supporting piles 2 are all cast-in-place piles, the pile length of each supporting pile 2 is not less than 1.5 times of the excavation depth of the foundation pits on two sides of the existing road 5, the pile diameter is 0.8-1.2 m, the pile spacing is 1.1-1.6 m, and the pile diameter is not more than 2 times of the pile diameter; the width of the pile top crown beam is 50-100 mm larger than the diameter of the pile, and the height of the pile top crown beam is 0.6-0.8 m. The level of 4 prestressed anchorage poles passes existing road 5, and the synchronous stretch-draw locking in both ends is on the waist rail 7 of a fender pile 2, carries out the counter-pull through the waist rail 7 of both sides a fender pile 2, stock 4 adopts the reinforcing bar preparation, and stock 4 adopts the PVC pipe outward to separate with the concrete of waist rail 7. The distance between the first row of prestressed anchor rods 4 and the top beam 3 of the support pile 2 is 2.5-3.5 m, the vertical distance between the second row of prestressed anchor rods 4 and the first row of prestressed anchor rods 4 is 3-4 m, the horizontal distance between each row of prestressed anchor rods 4 is twice of the pile distance, and the locking value of the prestressed anchor rods is 150-560 kpa.
When the pile body is constructed, the reduction coefficient of the active soil pressure of the limited soil body acting on the supporting structure is calculated by adopting the calculation method of the limited soil body close to the foundation pit of the existing building and the calculation of the soil pressure of the limited width soil body based on the upper limit analysis method, the active soil pressure is reduced, the construction parameters of the single-row pile are calculated by combining with the same-initiative star foundation pit design software according to the technical regulations on the foundation pit supporting of the building, and the construction parameters of the two rows of prestressed anchor rods are determined. The calculation formula of the active soil pressure reduction coefficient of the soil body with the limited width is as follows:
Figure BDA0003491187890000041
Figure BDA0003491187890000042
Figure BDA0003491187890000043
Figure BDA0003491187890000044
Figure BDA0003491187890000045
Figure BDA0003491187890000046
in the formula:
b, calculating the width (m) of the limited soil body, and taking a half of the vertical distance of the connecting line of the supporting piles at the two sides of the road;
h- -foundation pit supporting depth (m);
Pa-a rankine active earth pressure calculation;
Figure BDA0003491187890000047
-an active earth pressure upper limit (kPa) for a finite width earth mass;
εa-finite soil pressure reduction factor;
z0-a rear active earth pressure zero depth (m) of the earth-retaining member;
Ka-a rankine active earth pressure calculation factor;
Kp-rankine passive earth pressure calculation coefficients;
c- -cohesive force (kPa) of soil outside the soil retaining structure;
Figure BDA0003491187890000051
-internal friction angle (°) of the soil outside the earth retaining member;
the utility model is further illustrated by the following specific examples: a certain residential block in the Wuhan entrance area is composed of two blocks, a two-layer basement is arranged, and the excavation depth of a foundation pit is 8.04-10.8 m. Due to the influence of development rhythm, two plots are excavated simultaneously but are divided by a built municipal road, the width of the road is 15m, and the excavation depth of foundation pits at two sides of the road is 9.47 m. According to the geological survey report, the detailed geological condition information of two sides of the road in the table 1 can be obtained:
TABLE 1 detailed geological conditions of the construction area
Figure BDA0003491187890000052
In the embodiment, the existing municipal road is positioned in the range of one time of excavation depth of the foundation pit, and the safety grade of the foundation pit is one grade. Aiming at the foundation pit support, the project responsible person provides three support design schemes: (1) the single row of cast-in-situ bored piles and the two rows of prestressed anchor rods are pulled oppositely (namely the supporting structure in the utility model); (2) single row of cast-in-situ bored piles and internal supports (the construction period requires that the supports can not cover a building, soil is reserved at the bottom of the pit when the supports can not reach the position, and the supports are replaced by floor slabs after a main building is built up); (3) single row of cast-in-situ bored piles and inner supports (construction period requires, the supports can not cover a building, the positions where the supports can not reach are supported by double rows of piles, the rear row of piles of the double rows of piles form a red line, and the piles are pulled out in the later period by a construction method).
Through research and analysis, the second scheme has the following problems: the later unearthing of the pit bottom soil is difficult; when the main building is made along the storeroom at the pit edge, the floor slab needs to be replaced and supported, so that the construction period is delayed for a long time; the third scheme has the following problems: double row pile cost is higher, and the existing town road is closed to back row worker method stake, involves during the pile driving and during the later stage is pulled out and occupies the road the construction, and the time limit for a project is slow, with high costs and there is the shaped steel risk of can not necessarily pulling out. Therefore, the construction is carried out by adopting the first design scheme of the utility model.
The method adopts a scheme I that the excavation depth of the foundation pit is 9.47m, the width B of the limited soil body is 8.5m, the soil bodies except the soil retaining structure are considered according to the worst condition, the miscellaneous filling soil is taken as a calculation object, and the gravity gamma is 17kN/m3The cohesive force c is 8kPa, and the internal friction angle is
Figure BDA0003491187890000061
The method comprises the following steps of calculating a reduction coefficient of active soil pressure of a limited soil body acting on a supporting structure according to an active soil pressure calculation method of a limited soil body close to a foundation pit of an existing building and a limited width soil body soil pressure calculation method based on an upper limit analysis method, wherein the reduction coefficient of the active soil pressure of the limited width soil body is calculated as follows:
rankine active earth pressure calculation coefficient:
Figure BDA0003491187890000062
rankine passive earth pressure calculation coefficient:
Figure BDA0003491187890000063
zero depth of active soil pressure behind the soil retaining member:
Figure BDA0003491187890000064
rankine active earth pressure calculation:
Figure BDA0003491187890000065
the upper limit value of the active soil pressure of the limited soil body is as follows:
Figure BDA0003491187890000066
the soil pressure reduction coefficient of the limited soil body is as follows:
Figure BDA0003491187890000067
according to the reduction coefficient of the limited soil mass and the technical regulation of supporting foundation pit of buildings, the calculation is carried out by combining with the design software of the foundation pit of the Michelson of the same economy, and the pile diameter of the single row of piles and the anchor rod counter-pulling structure, the pile length of the pile is 18.00m, and the reinforcing bars are arranged
Figure BDA0003491187890000071
The construction parameters such as the pile spacing 1300mm, the anchor rod spacing 2600 and the like can simultaneously determine the elevation (respectively 2.5m and 5.5m away from the pile top) and the anchor rod (the first row)
Figure BDA0003491187890000072
Reinforcing steel bar, second row
Figure BDA0003491187890000073
Rebar), locked value (490 kpa, 370kpa, respectively).
After each construction parameter is determined, starting to construct a supporting structure:
(1) firstly, constructing supporting piles on the protecting surfaces of two sides of a road, excavating a top crown beam of the earthwork construction pile after the supporting piles reach the maintenance age, requiring to be excavated to the lower elevation of a bottom cushion layer of the crown beam, and integrally pouring the crown beam on each side.
(2) After the maintenance period of the crown beam is reached, earthwork is excavated in layers, a first row of anchor rods and a waist beam are constructed at the position which is excavated to be 3.0m below the surface of the crown beam, each row of prestressed anchor rods are horizontally arranged, and excavation processes of foundation pits at two sides need to be synchronously carried out or sequentially carried out, but synchronous tensioning and locking are carried out after the anchor rods at two sides are ensured to be communicated;
(3) after the first anchor rod is tensioned and locked, continuing to excavate earthwork in a layered and segmented mode, constructing a second row of anchor rods and a waist beam at a position 3m away from the first anchor rod, wherein each row of prestressed anchor rods are horizontally arranged, and foundation pit excavation processes on two sides need to be synchronously carried out or successively carried out, but the synchronous tensioning and locking after the anchor rods on two sides are communicated needs to be ensured;
(4) and (5) completing the prestress tensioning and locking of the second row of anchor rods, and excavating the earthwork to the bottom elevation of the foundation pit.
In the supporting structure, supporting piles on two sides of a road are symmetrically arranged, and the central connecting line of the supporting piles on the two sides of the road needs to be perpendicular to the axis of the road so as to ensure that anchor rods between the piles are oppositely pulled to be perpendicular to the road. Every row of prestressed anchor rods are horizontally arranged, and the excavation processes of foundation pits at two sides need to be synchronously carried out or carried out successively, but the synchronous tensioning and locking after the anchor rods at two sides are communicated are guaranteed. The horizontal distance between the anchor rods is 2 times of the distance between the piles, the distance between the first row of anchor rods and the crown beam surface is 2.5-3.5 m, and the distance between the second row of anchor rods and the first row of anchor rods is 3-4 m; the locking value of the prestressed anchor rod is 150-560 kpa. Every row of prestressed anchor rods are horizontally arranged, and the excavation processes of foundation pits at two sides need to be synchronously carried out or carried out successively, but the synchronous tensioning and locking after the anchor rods at two sides are communicated are guaranteed. The construction of each row of prestressed anchor rods sequentially comprises anchor rod body preparation, drilling and anchor rod body placement, waist beam reinforcement binding, formwork support, pre-buried PVC pipes and concrete pouring are carried out on the inner sides of foundation pits on two sides to finish waist beam construction, anchor rod tensioning locking construction is finally carried out, anchor rods of supporting sections on two sides are simultaneously constructed, and a crown beam and a waist beam are integrally poured.
Under the working condition that the foundation pit is excavated to the depth of 9.47m, the calculation results of the resistance, the displacement, the bending moment and the shearing force of the pile anchor structure are listed in the figure 3. By adopting the supporting scheme provided by the utility model, the supporting structure can meet the requirement of the safety of the foundation pit and better control the displacement of the foundation pit.
In this example, compared with the patent scheme: in the second scheme, a single row of cast-in-situ bored piles and inner supports are adopted (construction period is required, supports cannot cover a building, soil reserved at the bottom of a pit is adopted at positions where the supports cannot reach, and a floor is adopted for support replacement after a main building is built up), the support range of the second scheme is enlarged, the cost is increased by about 35 ten thousand, the support and cover of the main building at least delays construction period by about 4 months, construction period reduced construction cost is 6% of total construction cost of a project, the cost is increased by about 240 thousand, and the cost is increased by about 275 thousand in total; in the third scheme, a single row of cast-in-situ bored piles and an inner support are adopted (construction period requires, the support cannot cover a building, a double row pile support is adopted at a position where the support cannot reach, a red line appears on a row of piles behind the double row pile, and pile pulling-out in the later period of the construction method is adopted). Therefore, the scheme of the utility model has obvious economical efficiency.
The above description is only one embodiment of the present invention, and the description is specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims (4)

1. The utility model provides an existing road both sides foundation ditch combined support structure which characterized in that: the side-supporting anchor pile structure comprises two rows of supporting piles (2) which are uniformly distributed along the side line of a foundation pit on two sides of an existing road (5) and at least two rows of prestressed anchor rods (4) which are oppositely pulled between the supporting piles on the two sides, wherein each side-supporting pile (2) is positioned in the area between the side line (6) of the existing road and the side line (1) of the foundation pit excavation, and the pile spacing of each side-supporting pile (2) is not more than twice of the pile diameter; the prestressed anchor rods (4) horizontally penetrate through the existing road (5), two ends of the prestressed anchor rods are synchronously tensioned and locked on the waist beam (7) of the supporting pile (2), and the distance between the prestressed anchor rods (4) in the first row and the crown beam (3) of the supporting pile is 2.5-3.5 m.
2. The combined supporting structure for foundation pits on two sides of an existing road according to claim 1, wherein: prestressed anchorage pole (4) are equipped with two rows, and waist rail (7) through both sides fender pile (2) are drawn to every row of prestressed anchorage pole (4), and the vertical interval between two rows of prestressed anchorage poles (4) is 3 ~ 4m, and the horizontal interval is the twice of stake interval, and the locking value of prestressed anchorage pole is 150 ~ 560 kpa.
3. The combined supporting structure for foundation pits on two sides of an existing road according to claim 1, wherein: the supporting piles (2) are all cast-in-place bored piles, the pile length of the supporting piles (2) is not less than 1.5 times of the excavation depth of foundation pits on two sides of an existing road (5), the pile diameter is 0.8-1.2 m, the pile spacing is 1.1-1.6 m, and the pile diameter is not more than 2 times of the pile diameter; the width of the pile top crown beam is 50-100 mm larger than the diameter of the pile, and the height of the pile top crown beam is 0.6-0.8 m.
4. The combined supporting structure for foundation pits on two sides of an existing road according to claim 1, wherein: the anchor rod (4) is made of steel bars, and the outside of the anchor rod (4) is separated from concrete of the waist beam (7) by a PVC pipe.
CN202220222897.2U 2022-01-27 2022-01-27 Combined supporting structure for foundation pits on two sides of existing road Active CN216739770U (en)

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