CN116876518A - Construction method suitable for foundation pit supporting of assembled subway entrance and exit in soft soil area - Google Patents
Construction method suitable for foundation pit supporting of assembled subway entrance and exit in soft soil area Download PDFInfo
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- 239000010959 steel Substances 0.000 claims abstract description 77
- 238000009412 basement excavation Methods 0.000 claims abstract description 32
- 238000001556 precipitation Methods 0.000 claims abstract description 24
- 239000010410 layer Substances 0.000 claims abstract description 17
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Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/08—Restraining of underground water by employing open ditches arranged below the level of the water
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/10—Restraining of underground water by lowering level of ground water
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D31/00—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D31/00—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution
- E02D31/02—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution against ground humidity or ground water
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/02—Sheet piles or sheet pile bulkheads
- E02D5/03—Prefabricated parts, e.g. composite sheet piles
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/02—Sheet piles or sheet pile bulkheads
- E02D5/03—Prefabricated parts, e.g. composite sheet piles
- E02D5/04—Prefabricated parts, e.g. composite sheet piles made of steel
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
- E02D5/46—Concrete or concrete-like piles cast in position ; Apparatus for making same making in situ by forcing bonding agents into gravel fillings or the soil
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Structural Engineering (AREA)
- Mining & Mineral Resources (AREA)
- General Engineering & Computer Science (AREA)
- Civil Engineering (AREA)
- Paleontology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Chemical & Material Sciences (AREA)
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Abstract
The construction method for the foundation pit support of the assembled subway entrance and exit suitable for the soft soil area comprises the following construction steps: s1, slope laying excavation is carried out, an enclosure structure adopts SMW construction method piles, and then precipitation in a pit is carried out; s2, excavating soil body to be 0.5m below the first supporting position, and constructing a transverse strut; s3, excavating to the pit bottom, wherein foundation pit excavation is performed in a segmented, zoned and layered mode, and the foundation pit excavation is not performed in an overexcavation mode; s4, sequentially hanging the prefabricated assembled side walls, and splicing and fixedly connecting the prefabricated assembled side walls with the assembled bottom plate and the adjacent assembled side walls; s5, dismantling the first support after the back support is applied; s6, applying a waterproof layer and a protective layer, dismantling the inverted support, recovering the H-shaped steel, plugging the dewatering well and recovering the road surface. The enclosure structure adopts the closely inserted H-shaped steel construction method pile, the first-channel internal support and the inverted support are both steel supports, and the rapid support system is formed by matching with the assembled bottom plate and the side wall structure, so that the internal support is reduced, the support interval is increased, and the construction period is shortened.
Description
Technical Field
The invention relates to the technical field of building construction, in particular to a foundation pit supporting construction method suitable for an assembled subway entrance and exit in a soft soil area.
Background
At present, most provinces and key cities in China are greatly pushed to track traffic construction, so that various problems are brought, and the problems of low construction efficiency, poor operation environment and serious pollution in the subway station construction process are particularly remarkable. In the subway station construction process, the cast-in-situ construction workload of the auxiliary structure is large, the space is narrow during construction operation, the working procedures are many, the construction difficulty is large, the construction period is long, the operation environment is messy, the quality is not good, and the like, which are always common pain points in the industry.
The assembly technology not only reduces the wet workload of a construction site and labor cost, can reduce material waste to a certain extent and reduce construction noise, dust pollution, construction waste and sewage discharge, but also is an important way for effectively reducing carbon discharge in the construction process, and is used for carrying out the integrated research and application of the assembly technology in the field of rail transit, so that the consumption of wood templates, plastering cement mortar, construction water and construction electricity in the construction process of subway stations can be greatly reduced, the discharge of the construction waste is reduced by more than 80%, the carbon discharge and dust and noise pollution brought to the environment are obviously reduced, the improvement of urban environment, the improvement of the comprehensive quality and performance of subway stations and the promotion of ecological civilization construction are facilitated, and the creation of value is finally realized. The research of the subject can effectively expand the application scene of the assembly type technology in the field of rail transit, and solve the problems of high energy consumption and high pollution caused by the traditional construction mode.
The subway station passageway adopts cast-in-situ operation and steel construction more often, has that on-the-spot work load is big, construction progress is slow, degree of standardization is low, later maintenance frequency and expense scheduling problem. However, the subway station access & exit foundation pit supporting structure in the soft soil area is complicated, especially to the deep foundation pit, and the supporting member needs to set up the multichannel support in vertical, and horizontal interval is less, seriously influences subway access & exit assembled component hoist and mount and connection.
Disclosure of Invention
The invention provides a foundation pit supporting construction method suitable for an assembled subway entrance and exit in a soft soil area. The construction method can reduce the number of supports, increase the horizontal spacing of the supports, shorten the construction period, reduce the influence on peripheral economic traffic and resident life, and has the advantages of safety and economic benefit, thereby being applicable to the requirements of the construction of assembled subway entrances and exits in soft soil areas.
The invention adopts the technical scheme that:
the construction method for the foundation pit support of the assembled subway entrance and exit suitable for the soft soil area is characterized by comprising the following construction steps:
s1, constructing a fence, leveling a site, performing traffic fluffing, performing slope discharging excavation according to on-site geological conditions, controlling the slope height within 3m, and determining the slope according to calculation, wherein the slope is not suitable to be larger than 1:2, slope surface, making protection treatment, reserving a water drain hole, arranging a water interception ditch at the slope foot, and making slope body and drainage of the slope surface; the enclosure structure is formed by adopting an SMW construction method pile and a triaxial stirrer, H-shaped steel is densely inserted into the whole section of the stirring pile, and the soil-in ratio of the SMW continuous wall is 1:1, according to calculation, the enclosure structure meets the requirements of strength, overall stability and deformation; after the construction of the SMW construction method pile is finished, carrying out precipitation in the pit;
s2, excavating soil body to be 0.5m below the first supporting position, constructing a transverse brace, enabling the end face of the transverse brace to be perpendicular to the contact face of the waist beam, and performing design checking calculation on the embedded part and the welding structure; the waist beam adopts double-spliced or triple-spliced I-steel plate combined sections, steel supports are timely installed, and prestress is accurately applied; continuing to carry out precipitation in the pit, and keeping the groundwater level 1-2 m below the excavation surface when soil is excavated in layers according to the excavation progress;
s3, excavating to the pit bottom, wherein foundation pit excavation is performed in a segmented, zoned and layered mode, and the foundation pit excavation is not performed in an overexcavation mode; the width of the exposed part of the enclosure structure is controlled to be 3-6 m, the excavation depth of each layer is not more than 2.5m, and the excavation is forbidden to be completed once; applying a cushion layer, and setting paving fine stone concrete with the thickness not smaller than 300 mm; hanging the assembled bottom plates of the subway entrance and the subway entrance, when the entrance and the subway entrance are longer, sequentially putting the assembled bottom plates into sections, and splicing and fixing adjacent assembled bottom plates;
s4, after the bottom plate structure is firmly connected, sequentially hanging the prefabricated assembled side walls, and splicing and fixedly connecting the prefabricated assembled side walls with the assembled bottom plate and the adjacent assembled side walls; the steel plates are pre-embedded in the assembled side wall in advance, after the assembled side wall is spliced and fixed, the back support is timely applied to the side wall structure, and the back support is directly propped against the pre-embedded steel plates of the assembled side wall;
s5, after the back support is applied, the first support is removed, before the back support is removed, the bottom plate structure, the back support, the side wall structure and the enclosure system are inspected, the connection is firm, the force transfer is stable, the steel wedge blocks are unloaded step by step, and the support is removed; sequentially hanging and installing the assembled top plate, and splicing and fixedly connecting the assembled top plate with the assembled side wall and the adjacent assembled top plate;
s6, after the roof structure is firmly connected, a waterproof layer and a protective layer are applied, the inverted support is removed, the H-shaped steel is recovered after backfilling, the dewatering well is plugged, and the pavement is recovered.
In the step S1, when a longitudinal slope is laid and excavated, a water intercepting ditch or a water retaining earth dike is arranged outside the top of the slope, so that surface water is prevented from flushing the slope or draining water outside the foundation pit and reflowing into the pit. When earth is excavated, the waste soil is piled up and should keep away from the foundation pit roof line beyond 20 m. Building materials are piled around the periphery of the foundation pit, or transport tools and other machines are moved along the edge of the foundation pit, and the distance between the building materials and the edge of the upper part of the foundation pit is not less than 2m. The construction error of the cement mixing pile is strictly controlled, and the perpendicularity of the pile body is not more than 1/200.
In the step S2, the steel support is installed within a specified time, and the erection of the steel support must be accurate and in place, and the prestressing force must be applied strictly as required. In addition, in the whole construction process from erection to dismantling of the steel support, the monitoring of the steel support is strictly required, and the stability of the steel support is ensured. A strict monitoring network is established in the influence range of precipitation, the water level and the water pressure inside and outside the pit and the change of the surrounding environment caused by the water pressure are monitored, and the environmental influence caused by the precipitation is subjected to special analysis.
In the step S3, after the foundation pit is excavated, drainage ditches and water collecting wells in the pit are timely arranged to prevent water accumulation at the bottom of the pit, after the foundation pit is excavated to the bottom of the pit in a segmented mode, cushion layer concrete is rapidly poured to control the deformation of the foundation pit, and after the splicing of the lifting assembly type bottom plate is completed, high-strength fast hard fine stone concrete is used for filling gaps between the bottom plate and the enclosure structure.
In the step S4, the prefabricated assembled side wall is connected by reserving a sleeve in the wall through a high-strength bolt, and a connecting gap is filled with an expanding agent; before the reverse support is installed, the horizontal displacement of the SMW construction method pile and the axial force of the support are monitored, detection data are reserved, a steel support is supported by welding steel bar brackets on the embedded plates during the reverse support installation, after the support erection is completed, the close fit condition of the support steel plates and the embedded steel plates is checked, steel wedges are wedged in gaps between the support steel plates and the embedded steel plates, the steel wedges are required to be symmetrically installed, and the steel wedges are plugged by iron plates, so that the integral supporting effect of a supporting system is ensured.
In the step S5, the steel support is suspended and protected by a steel wire rope through a suspension rope, so that the safety of the foundation pit is prevented from being endangered due to falling off, and the steel support is gradually unloaded until the steel wedge is taken out.
The invention has the beneficial effects that: according to the invention, the depth of the foundation pit at the subway entrance and exit is effectively reduced by slope laying, the enclosure structure adopts the dense-insert H-shaped steel construction method pile, the first-pass internal support and the inverted support are both steel supports, and the rapid support system is formed by matching with the assembled bottom plate and the side wall structure, so that the internal support is reduced, the support interval is increased, the construction period is shortened, and the rapid support and rapid disassembly support system is provided for the construction of the foundation pit at the assembled subway entrance and exit.
Drawings
Fig. 1 is a construction schematic diagram of step S1 of the present invention.
Fig. 2 is a construction schematic diagram of step S2 of the present invention.
Fig. 3 is a construction schematic diagram of step S3 of the present invention.
Fig. 4 is a construction schematic diagram of step S4 of the present invention.
Fig. 5 is a construction schematic of step S5 of the present invention.
Fig. 6 is a construction schematic of step S6 of the present invention.
Wherein: 1-a dewatering well; 2-SMW construction method piles; 3-slope releasing; 4-crown beam; 5-cross braces; 6-assembling a bottom plate; 7-assembling type side walls; 8-backing; 9-fabricated top plate.
Detailed Description
The construction method for the foundation pit support of the assembled subway entrance and exit suitable for the soft soil area comprises the following specific steps:
s1, constructing a fence, leveling a site, performing traffic fluffing, performing slope 3 excavation according to on-site geological conditions, controlling the slope height within 3m, and determining the slope according to calculation, wherein the slope is not suitable to be larger than 1:2, slope surface, making protection treatment, reserving a water drain hole, arranging a water interception ditch at the slope foot, and making slope body and drainage of the slope surface; the enclosure structure is formed by adopting an SMW construction method pile 2 and a triaxial mixer, construction errors of the cement-soil mixing pile are strictly controlled, and the perpendicularity of the pile body is not more than 1/200;
according to soil quality and site conditions, construction parameters such as sinking speed, rotating speed, slurry spraying time, slurry spraying flow, lifting speed and the like are determined, after the construction of the stirring pile is finished, the section steel is quickly inserted into the composite soil, the section steel is conveniently pulled out, the surface of the section steel is coated with a friction reducer, and cement injection is adopted to backfill the holes of the section steel pulled out; the mixing pile is closely inserted with H-shaped steel in full section, and the soil-in ratio of the SMW continuous wall is about 1:1, according to calculation, the enclosure structure meets the requirements of strength, overall stability, deformation and the like; the depth of the inserted section steel in the SMW cement mixing pile wall meets the calculation requirements of the foundation pit on anti-uplift and anti-overturning performance, the overall stability, the internal force and deformation of the enclosure wall and the seepage resistance of the foundation pit, and the section steel can be smoothly pulled out after the construction of the underground structure is considered; when the internal force and deformation calculation of the pile wall and the stability analysis of each item of foundation pit sequence are carried out, the depth of the pile wall is based on the bottom end of the inserted section steel, and the action of the cement-soil mixing pile below the end of the section steel is not calculated; the verticality deviation of the stirring pile and the inserted section steel is less than or equal to 1/200, the pile position deviation is less than or equal to 50mm, the pile diameter deviation is less than or equal to +10mm, and the section steel centroid rotation angle deviation is less than or equal to 3 degrees;
the construction of the H-shaped steel SMW construction method pile 2 is completed and is verified to be qualified, the construction of a crown beam 4 is carried out, a foundation pit is excavated to the bottom elevation of the crown beam 4, slurry on the top surface of a guard pile is chiseled, water is used for washing cleanly, then reinforcement binding, template installation and concrete pouring are carried out, the guard structure is connected into a whole, then precipitation in the pit is carried out, the 1-point burying depth of a precipitation well is 4-5 m below the pit, the diving precipitation starts about 20 days before the foundation pit is excavated, the groundwater level is kept 1-2 m below the excavated surface when soil is excavated in layers, the precipitation amount is strictly controlled on the premise of stabilizing the foundation pit and excavating in earthwork, a strict monitoring network is established in the influence range of precipitation, the water level, the water pressure inside and outside the pit and the surrounding environment change caused by precipitation are monitored, and the response of the environmental shadow caused by precipitation is subjected to special analysis;
s2, after the reinforcement of the guard piles and the foundation outside the pit reaches the design strength, pit excavation can be carried out, the pile is drilled and core-removed before excavation, the impervious coefficient of the pile is required to be less than or equal to 1x10 (-7) cm/S, the compressive strength of the pile in 28 days is required to be more than or equal to 1.0MPa, and the pit excavation can be carried out; the foundation pit excavation should be noted that the longitudinal side slope of the foundation pit is stable, the 'space-time effect' effect should be fully utilized during excavation, foundation pit segmentation and layered excavation should be adopted, and during excavation, the waste soil pile should be far away from the top edge of the foundation pit and transported away as soon as possible;
excavating soil body to 0.5m below the first supporting position, constructing a transverse support 5, enabling the end face of the transverse support 5 to be perpendicular to the contact face of the waist beam, and performing design checking calculation on embedded parts and welding structures; the waist beam adopts double-spliced or triple-spliced I-steel plate combined sections, steel supports are timely installed and accurately pre-stressed, the installation period of the steel supports is not more than 8 hours, the steel supports are installed in a specified time, the erection of the steel supports is required to be accurately in place, the pre-stress is strictly applied according to the requirements, and each link of manufacturing, installation and the like is required to be carefully operated; the tolerances of the support mounting should meet the following specifications: the elevation difference of the support center is not more than 30mm, the elevation difference of the two ends of the support is not more than 20mm and the l/600 of the support length, the support deflection is not more than 1/1000 of the support length, the support horizontal axis deviation is not more than 30mm, and the support installation eccentric distance is required to be less than 20mm; in the whole construction process from erection to dismantling of the steel support, the monitoring of the steel support is strictly required, so that the stability of the steel support is ensured;
continuing to carry out precipitation in the pit, and keeping the groundwater level 1-2 m below the excavation surface when soil is excavated in layers according to the excavation progress; after the foundation pit is excavated, a drainage ditch and a water collecting well in the pit are timely arranged to prevent water accumulation at the bottom of the pit; the excavating machinery and the vehicle cannot directly walk on the support, and the excavating machinery is strictly forbidden to collide with the support, the upright post, the well point pipe and the guard pile;
s3, excavating to the pit bottom, wherein foundation pit excavation is performed in a segmented, zoned and layered mode, and the foundation pit excavation is not performed in an overexcavation mode; the width of the exposed part of the enclosure structure is controlled to be 3-6 m, the excavation depth of each layer is not more than 2.5m, the excavation is strictly forbidden to be completed once, the pit bottom is reserved for manually excavating and leveling a soil layer with the thickness of 200-300 mm, and the pit bottom soil disturbance is prevented;
rapidly applying a cushion layer after digging to the pit bottom, and setting a paving fine stone concrete with the thickness of not less than 300mm to control the deformation of the foundation pit; the water outlet and precipitation effect sealing part precipitation well 1 can be combined before the construction of the bottom plate, wherein the water outlet and precipitation effect sealing part precipitation well 1 is formed by hanging out the inlet assembly type bottom plate 6, and when the inlet and outlet are longer, the water outlet and the precipitation effect sealing part are sequentially put in sections;
when the foundation pit is excavated to cause unsteady sand, water burst or pit bottom bulge, or when the deformation of the enclosure structure is overlarge or a precursor of unstability exists, the construction should be stopped immediately, and reliable and effective measures are taken to ensure the safe and smooth construction; during excavation and structural construction of a foundation pit, construction overload around the foundation pit is not more than 20kPa, and construction load on a steel support is not more than 0.5kN/m;
s4, after the bottom plate structure is firmly connected, sequentially hanging the assembled side walls 7, and splicing and fixedly connecting the assembled side walls 7 with the assembled bottom plate 6 and the adjacent assembled side walls 7; the steel plates are pre-buried in the assembled side wall 7 in advance, after the assembled side wall 7 is spliced and fixed, the inverted support 8 is timely applied to the side wall structure, the inverted support 8 is directly propped against the pre-buried steel plates of the assembled side wall 7, and the installation period of the inverted support 8 is not more than 8 hours; reliable supporting and connection are needed for each support, so that support falling caused by deformation of the enclosure structure and construction impact is prevented;
s5, after the back support 8 is applied, the first support is removed, before the back support 8, the bottom plate structure, the back support 8, the side wall structure and the enclosure system are inspected, the connection is firm, the force transfer is stable, the tapping wedge blocks are unloaded step by step, and the support is removed; sequentially hanging and installing the assembled top plate 9, and splicing and fixedly connecting the assembled top plate 9, the assembled side wall 7 and the adjacent assembled top plate 9;
s6, after the roof structure is firmly connected, a waterproof layer and a protective layer are applied, the inverted support 8 is removed, backfilling soil is adopted, the foundation pit backfilling material adopts cohesive soil, accumulated water and sundries in the pit are cleaned up before backfilling, the backfilled virtual soil is compacted, and after the backfilling is inspected to be qualified, the foundation pit backfilling can be backfilled, and layering and horizontal compaction are carried out;
the two sides and the periphery of the underground pipeline within 500mm of the top of the structure are manually tamped by using a small machine tool; the backfill compactness is required to meet the original soil index, and when the field inspection cannot meet the requirement, grouting or other effective measures can be adopted for treatment to meet the requirement;
recovering H-shaped steel after backfilling, and recovering the pavement; after the internal structure is completed and the earth is covered, the well can be completely sealed in the precipitation well 1 side, and after the well point pipe of the precipitation well 1 is pulled out, the well hole is backfilled and sealed in time.
According to the invention, the depth of the foundation pit at the subway entrance and exit is effectively reduced by slope laying, the enclosure structure adopts the dense-insert H-shaped steel construction method pile, the first-pass internal support and the inverted support 8 are both steel supports, and the rapid support system is formed by matching the assembled bottom plate 6 and the assembled side wall 7 structure, so that the internal support is reduced, the support interval is increased, the construction period is shortened, and the rapid support and rapid disassembly support system is provided for the construction of the foundation pit at the subway entrance and exit.
The foregoing describes the embodiments of the present invention in detail, but the description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.
Claims (6)
1. The construction method for the foundation pit support of the assembled subway entrance and exit suitable for the soft soil area is characterized by comprising the following construction steps:
s1, constructing a fence, leveling a site, performing traffic fluffing, performing slope (3) excavation according to on-site geological conditions, controlling the slope height within 3m, determining the slope according to calculation, and ensuring that the slope is not more than 1:2, slope surface, making protection treatment, reserving a water drain hole, arranging a water interception ditch at the slope foot, and making slope body and drainage of the slope surface; the enclosure structure is formed by adopting an SMW construction method pile (2) and a triaxial stirrer, H-shaped steel is densely inserted in the whole section of the stirring pile, and the soil-in ratio of the SMW continuous wall is 1:1, according to calculation, the enclosure structure meets the requirements of strength, overall stability and deformation; after the construction of the H-shaped steel SMW construction method pile (2) is completed, crown beam (4) construction is carried out, all the enclosure structures are connected into a whole, and then precipitation in a pit is carried out;
s2, excavating soil body to be 0.5m below the first supporting position, constructing a transverse brace (5), enabling the end face of the transverse brace (5) to be perpendicular to the contact face of the waist beam, and performing design checking calculation on the embedded part and the welding structure; the waist beam adopts double-spliced or triple-spliced I-steel plate combined sections, steel supports are timely installed, and prestress is accurately applied; continuing to carry out precipitation in the pit, and keeping the groundwater level 1-2 m below the excavation surface when soil is excavated in layers according to the excavation progress;
s3, excavating to the pit bottom, wherein foundation pit excavation is performed in a segmented, zoned and layered mode, and the foundation pit excavation is not performed in an overexcavation mode; the width of the exposed part of the enclosure structure is controlled to be 3-6 m, the excavation depth of each layer is not more than 2.5m, and the excavation is forbidden to be completed once; applying a cushion layer, and setting paving fine stone concrete with the thickness not smaller than 300 mm; the subway entrance and exit assembled bottom plates (6) are hung, when the entrance and exit are long, the subway entrance and exit are sequentially put in sections, and adjacent assembled bottom plates (6) are spliced and fixed;
s4, after the bottom plate structure is firmly connected, sequentially hanging prefabricated assembly type side walls (7), and splicing and fixedly connecting the prefabricated assembly type side walls with the assembly type bottom plate (6) and adjacent assembly type side walls (7); the steel plates are pre-buried in the assembled side wall (7), after the assembled side wall (7) is spliced and fixed, the back support (8) is timely applied to the side wall structure, and the back support (8) is directly propped against the pre-buried steel plates of the assembled side wall (7);
s5, after the inverted support (8) is applied, the first support is removed, before the first support is removed, the bottom plate structure, the inverted support (8), the side wall structure and the enclosure system are inspected, the connection is firm, the force transmission is stable, the tapping wedge blocks are unloaded step by step, and the supports are removed; sequentially hanging and installing the assembled top plate (9), and splicing and fixedly connecting the assembled top plate with the assembled side wall (7) and the adjacent assembled top plate (9);
s6, after the roof structure is firmly connected, a waterproof layer and a protective layer are applied, the inverted support (8) is removed, the H-shaped steel is recovered after backfilling, the dewatering well (1) is plugged, and the pavement is recovered.
2. The construction method for supporting foundation pit of assembled subway entrance and exit in soft soil area according to claim 1, wherein in step S1, when the longitudinal slope (3) is excavated, a water intercepting ditch or a water retaining earth dike is arranged outside the top of the slope to prevent surface water from flushing the slope or the drainage outside the foundation pit from flowing back into the pit.
3. The construction method for foundation pit support of assembled subway entrance and exit in soft soil area according to claim 1, characterized in that in step S2, steel supports are installed in a specified time, the erection of the steel supports must be accurate and in place, and pre-stress is applied strictly according to the requirement, a strict monitoring network is built in the influence range of precipitation, the water level, water pressure and the surrounding environment changes caused inside and outside the pit are monitored, and the environmental influence caused by precipitation is subjected to special analysis.
4. The construction method for supporting foundation pit of assembled subway entrance and exit in soft soil area according to claim 1, characterized in that in step S3, after the foundation pit is excavated, drainage ditch and water collecting well are set in time to prevent water accumulation at the bottom of the pit, when the foundation pit is excavated to the bottom of the pit in sections, cushion layer concrete is poured rapidly to control foundation pit deformation, after the assembled bottom plate (6) is hung, high-strength fast hard fine stone concrete is used to fill the gap between the bottom plate and the enclosure structure.
5. The construction method for foundation pit support of assembled subway entrance and exit in soft soil area according to claim 3, wherein in step S4, prefabricated assembled side walls (7) are connected by high-strength bolts through reserved sleeves in the walls, and the connecting gaps are filled with expanding agent; before installing the back support (8), monitoring horizontal displacement of the SMW construction method pile (2) and axial force of the support, and keeping detection data, welding steel bar brackets on the embedded plates to support the steel support when the back support (8) is installed, checking the close fit condition of the supporting steel plates and the embedded steel plates after the support is erected, wedging steel wedges in gaps of the supporting steel plates and the embedded steel plates, wherein the steel wedges are required to be symmetrically installed, and are plugged by iron plates, so that the integral supporting effect of a supporting system is ensured.
6. The construction method for foundation pit support of assembled subway entrance and exit in soft soil area according to claim 1, wherein in step S5, steel support is suspended and protected by steel wire rope with suspension rope, so as to prevent the safety of foundation pit from being endangered by falling off, and the foundation pit is gradually unloaded to the end of taking out steel wedge.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310732282.3A CN116876518A (en) | 2023-06-20 | 2023-06-20 | Construction method suitable for foundation pit supporting of assembled subway entrance and exit in soft soil area |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310732282.3A CN116876518A (en) | 2023-06-20 | 2023-06-20 | Construction method suitable for foundation pit supporting of assembled subway entrance and exit in soft soil area |
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| Publication Number | Publication Date |
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| CN116876518A true CN116876518A (en) | 2023-10-13 |
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| CN202310732282.3A Pending CN116876518A (en) | 2023-06-20 | 2023-06-20 | Construction method suitable for foundation pit supporting of assembled subway entrance and exit in soft soil area |
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| Country | Link |
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| CN (1) | CN116876518A (en) |
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