CN113186942A - Pipe jacking well enclosure structure and excavation construction method - Google Patents
Pipe jacking well enclosure structure and excavation construction method Download PDFInfo
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- CN113186942A CN113186942A CN202110512564.3A CN202110512564A CN113186942A CN 113186942 A CN113186942 A CN 113186942A CN 202110512564 A CN202110512564 A CN 202110512564A CN 113186942 A CN113186942 A CN 113186942A
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- 238000010276 construction Methods 0.000 title claims abstract description 75
- 238000009412 basement excavation Methods 0.000 title claims abstract description 39
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 110
- 239000010959 steel Substances 0.000 claims abstract description 110
- 239000004567 concrete Substances 0.000 claims abstract description 60
- 238000000034 method Methods 0.000 claims abstract description 43
- 230000008093 supporting effect Effects 0.000 claims abstract description 18
- 238000007789 sealing Methods 0.000 claims abstract description 15
- 239000002689 soil Substances 0.000 claims description 32
- 239000000463 material Substances 0.000 claims description 18
- 238000013461 design Methods 0.000 claims description 17
- 239000004033 plastic Substances 0.000 claims description 14
- 238000003466 welding Methods 0.000 claims description 10
- 238000005086 pumping Methods 0.000 claims description 9
- 230000004888 barrier function Effects 0.000 claims description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 5
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- 239000004575 stone Substances 0.000 description 6
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 5
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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
- E02D17/06—Foundation trenches ditches or narrow shafts
- E02D17/08—Bordering or stiffening the sides of ditches trenches or narrow shafts for foundations
-
- 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
-
- 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
-
- 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
- E02D17/06—Foundation trenches ditches or narrow shafts
- E02D17/08—Bordering or stiffening the sides of ditches trenches or narrow shafts for foundations
- E02D17/083—Shoring struts
-
- 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
- E02D17/18—Making embankments, e.g. dikes, dams
-
- 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
- E02D19/02—Restraining of open water
- E02D19/04—Restraining of open water by coffer-dams, e.g. made of sheet piles
-
- 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
Abstract
The invention provides a pipe jacking well enclosure structure and an excavation supporting method thereof, and belongs to the field of pipe jacking construction. The technical scheme is as follows: the method for excavating and supporting the pipe jacking well enclosure structure comprises the following steps: leveling a field, constructing a dewatering well, constructing a steel sheet pile, excavating a first layer of earthwork, constructing a concrete ring beam, constructing subsequent segments and sealing a bottom. The invention has the beneficial effects that: the construction method has the advantages of short construction period, turnover use, low cost, higher support strength, sufficient underground space and high safety, improves the construction safety and the construction efficiency, and is beneficial to environmental protection.
Description
Technical Field
The invention relates to the field of pipe jacking construction, in particular to a pipe jacking well enclosure structure and an excavation construction method.
Background
Along with urban development, urban construction space gradually extends to the underground from the ground, expands to deep underground passage structure by expressway overhead, such as tunnel, piping lane, pipeline etc. urban space utilization reaches the maximize, is novel modernized city development trend, simultaneously, we also face the challenge to underground engineering construction.
In the underground engineering construction process, open excavation, underground excavation and other forms are usually adopted, and the underground excavation comprises a mine method, a pipe jacking method, a shield method and the like. In a complex urban environment, for urban pipe network construction, in order to not influence ground houses and other engineering facilities, a pipe jacking method is usually adopted for construction, an initial well needs to be arranged, the supporting form of the initial well is generally prefabricated on the ground in a concrete underground continuous wall form in advance, then soil is excavated in the well, the circumference synchronously sinks, and finally the designed foundation pit bottom elevation is achieved.
Disclosure of Invention
The invention aims to provide a pipe jacking well enclosure structure and an excavation construction method which have the advantages of short construction period, turnover use, low manufacturing cost, higher support strength, sufficient underground space and high safety, improve the construction safety and the construction efficiency and are beneficial to protecting the environment.
The invention is realized by the following measures:
a pipe jacking well enclosure excavation supporting method is characterized by comprising the following steps:
(1) leveling the field: leveling a pre-constructed field, removing foreign matters on the ground, erecting a surrounding barrier of the construction field according to the requirement of green construction, closing in time, and determining the ground position of an excavated pipe jacking well according to the design requirement;
(2) and (3) dewatering well construction: arranging a plurality of precipitation wells on the ground at the periphery of a starting well to be excavated (the number of the precipitation wells can be properly increased according to the underground water level condition and the excavation depth condition so as to achieve the precipitation effect), arranging 1 precipitation well in the starting well, and performing pumping operation 1 week ahead;
(3) constructing a steel sheet pile: according to the design of a starting well, setting out a line in a construction area, and inserting and driving a single row of annular closed steel sheet piles;
(4) excavating the earth on the first layer: carrying out earthwork excavation in a construction range, synchronously carrying out inner side dewatering sand-free pipe dismantling, and carrying out concrete ring beam construction after the earthwork excavation reaches the bottom elevation of the first layer of concrete ring beam;
(5) and (3) concrete ring beam construction: welding steel sheet pile ear plates, laying concrete ring beam bottoms and side templates, binding main steel bars on an enclosure, welding anti-falling steel bars, finally, erecting a concrete template support, pouring concrete of the concrete ring beam, and removing the template after the strength reaches 75% of the design requirement to form the concrete ring beam support;
(6) subsequent segment construction and bottom sealing: and (5) repeating the step (4) and the step (5), and after excavating to the designed bottom elevation of the foundation pit, performing bottom sealing concrete pouring.
The invention has the following specific characteristics:
the steel sheet pile adopts a fixed modulus Larsen IV type steel sheet pile, the joint of the steel sheet pile is fastened, and the inclination of each steel sheet pile is not more than 2%.
The first layer of earthwork excavation is earth surface soil excavation performed after the construction of the steel sheet pile is finished, the excavation depth of the first layer of earthwork excavation meets the depth of the first layer of concrete ring beam structure, and the supporting effect of the fender pile on the soil body meets the soil body stability requirement.
In the steel sheet pile construction step, 10-20 steel sheet piles are inserted into the guide frame in rows to be driven in a screen shape, firstly, a group of steel sheet piles at two ends of the screen wall are driven to a designed elevation or a certain depth, the verticality is strictly controlled, and then the steel sheet piles are driven in the middle according to the height of 1/3 or 1/2 steel sheet piles in sequence.
The bottom die and the side die of the concrete ring beam are made of plastic materials.
A pipe jacking well enclosure structure is characterized by comprising a plurality of steel sheet piles and concrete ring beams arranged on the inner sides of the steel sheet piles, wherein the steel sheet piles form an annular cofferdam.
The steel sheet pile adopts a fixed modulus Larsen IV type steel sheet pile, and the inclination of each steel sheet pile is not more than 2%.
And the bottom die and the side die of the concrete ring beam are both made of plastic materials.
The pipe jacking well enclosure is realized according to the excavation supporting method of the pipe jacking well enclosure of the claims 1-5.
The dewatering well construction method specifically comprises the following steps:
measuring well position
According to the measurement control point that design unit provided, measure the unwrapping wire and confirm the well point position, excavate the well point, precipitation well spacing slot upper shed line 1m arranges, excavates a little pit, and is about 500mm deep to catchment when trompil, and be connected little pit and sump pit with the ditch, so that excrete unnecessary water.
Drilling machine in position
And a hole is formed by adopting a reverse circulation drilling machine, and a vehicle-mounted reverse circulation power head drilling machine is selected as the reverse circulation drilling machine. The hoisting equipment is operated by a hoisting personnel with a professional license, and a specially-assigned person commands the hoisting equipment. When the pile driver is installed, three points are arranged in a line, namely the center of a drill rod, the center of a rotary table and the center of a pile hole are on the same plumb line, so that the verticality of a drilled hole is guaranteed, and the deviation between the center of the rotary table and the center of the pile hole is less than or equal to 10 mm. The installation of the drilling machine must be stable and firm, displacement cannot occur during drilling, the base is cushioned, and the drilling machine is frequently checked during drilling. After the equipment is installed in place, the equipment is carefully leveled and firmly installed, and the equipment is firstly tried before operation so as to prevent mechanical failure during hole forming. All electromechanical equipment needs safe and reliable wiring, and a cable buried pipeline on a transportation road is protected. The installation, use, removal, disassembly and maintenance of each piece of equipment are operated and used according to the operating instruction.
Preparation of slurry
High-plasticity bentonite is selected for preparing the slurry.
Fourthly, drilling
A. And the circulating system is arranged, namely the circulating system is reasonably arranged according to the actual situation of the field, and the flushing liquid is required to circulate smoothly, so that the drilling slag is easy to remove. The capacity of the mud pool is not less than 5m3To ensure normal circulation of the rinse solution. When drilling a hole, firstly lightly pressing and slowly drilling, controlling the pump amount, and gradually increasing the rotating speed and the drilling pressure after entering a normal working state. Before formal construction, trial hole forming is carried out;
B. the drilling operation needs to be continuously carried out, and when the drilling is stopped due to the reason, the drill bit needs to be lifted away from the bottom of the hole by more than 5m so as to prevent the collapse hole from burying the drill;
C. during the drilling process, the stratum change is noticed, and different drilling methods are adopted for different soil layers. When drilling in hard clay, loosening the hoisting steel wire rope by using a first gear of rotating speed, and freely advancing; when drilling in common clay and sand clay, the drilling tool can freely advance with second gear and third gear rotating speed; when the silt soil is rich in underground water and easy to collapse, low-grade slow drilling is adopted, the stirring of the silt soil by a drill bit is reduced, and the specific gravity of slurry is increased and the water head is increased to strengthen the wall protection and prevent the collapse of the hole;
D. when drilling, decompression drilling is needed, even if the bit pressure born by the bottom of the hole does not exceed 80% of the sum of the gravity of the drill bit and the gravity of the weight minus the buoyancy, the drill rod can be kept in a vertical state, the drill bit can rotate vertically and stably, and the phenomena of inclined holes, bent holes and hole expansion are avoided or reduced.
Fifthly, cleaning holes
And (3) timely cleaning and lifting the hole after the designed hole depth is reached, lifting the drill bit away from the hole by 15-20 cm when the hole is cleaned, inputting slurry for circular hole cleaning, and controlling the specific gravity of the slurry and adjusting the performance of the slurry. The sand content of the fresh slurry in the hole is gradually reduced to a stable and non-settling degree.
Hanging non-sand concrete pipe
The down pipe adopts a suspended tray down pipe method, and the pipe barrel must be tightly packaged by a gauze in a silt layer section to prevent sand gushing. The sand cushion layer is firstly backfilled before the water filter pipe is arranged, then the settling pipe (concrete solid wall pipe) is arranged, then the concrete water filter pipe is arranged, and the upper pipe and the lower pipe are bound and connected by bamboo skin (thin bamboo) iron wires. When the pipe is to be lowered, the center of the pipe must be aligned with the center of the drilled hole. The lower pump is preferably suspended in the well by a hemp (or palm) rope, lowered to a designed depth and firmly tied at the well mouth.
Seventh, fill the filtering material
The filter material is medium coarse sand or fine stone, the thickness of the filter material is not less than 100mm, and the lower part of the filter material is 2m lower than the filter tube;
and after the pipe is lowered, immediately filling filter materials between the pipe wall and the hole wall, and slowly filling the filter materials from the periphery by using an iron mill during enclosing and tamping by using reinforcing steel bars to prevent the middle from being hollow. When filling, the filter material should be filled uniformly and continuously along the circumference of the well pipe and measured as filling. When the filling quantity, depth and calculation have larger accesses, the reason should be found and eliminated in time.
Eight well-flushing slurry discharging
The well is washed by a sewage pump or a submersible pump, the standard of well washing is based on that water pumped out from the well is clear, and the well washing time is required to be not less than 4 hours.
Ninthly drainage
The pumping equipment adopts a sewage pump or a submersible pump, a valve is installed in each well to adjust the flow, the valve is fixed by a clamp plate, the ground main pipe adopts a DE400 PE pipe, the passway pipe adopts a DE300 steel pipe, the wall thickness is 5mm, the steel pipe is sealed by concrete, a water collecting sedimentation tank is arranged according to the actual situation of pumping water of the foundation pit, and finally, the water collecting sedimentation tank is arranged to a nearby drainage pipe network along the main pipe.
Monitoring and maintenance of the r
And (4) observing the underground water level by using a precipitation well, wherein the underground water level is observed for 1-2 times every day at the early stage of precipitation. The dewatering well is required to be ensured to be intact during dewatering, regular inspection and maintenance are carried out on the dewatering well, problems are found and timely treated, and the safety of foundation pit construction is ensured. During precipitation, the foreign matters are forbidden to be put into the pipe well, the effect of pumping water is avoided being influenced, and the pipe well mouth is bound and sealed, so that the safety of ground personnel is guaranteed.
Backfilling after the water dropping of the pipe well is finished, and filling clay to seal the well when the pipe well is suggested to be positioned on a green belt or a sidewalk according to the determination of field technological tests; when the pipe well is positioned on the roadway, sealing the well by adopting a sand filling method, filling the well with sand, and then filling water into the sand in the well until the sand is filled; shortly after the well is full, the sand will settle in the well, and then the sand is again filled, water is poured, until the fill level is reached.
During the construction of the steel sheet pile, before piling, the steel sheet pile is inspected one by one, common sheet piles with rusty connecting locking openings and serious deformation are removed, grease is coated in the locking openings of the steel sheet pile to facilitate driving and pulling out, the inclination of each pile is monitored at any time in the inserting and driving process is not more than 2%, when the inclination is too large and cannot be adjusted by a drawing and aligning method, the steel sheet pile is pulled and driven, the construction combining a one by one driving method and a screen type driving method can be considered in the driving of the steel sheet pile, a screen type driving method is suggested to be used in areas with dense sandy soil and high-viscosity soil, and the construction sequence of the screen type driving method comprises a forward sequence, a reverse sequence, a reciprocating sequence, a middle dividing sequence, a neutralizing sequence and a composite sequence. The construction sequence has direct influence on the verticality, displacement, expansion in the axis direction, the concave-convex of the steel sheet pile wall and the piling efficiency. Therefore, the construction sequence is one of the keys of the steel sheet pile construction process, and the selection principle is as follows: when the steel sheet piles which are arranged at the two ends of the screen wall are inclined reversely, the steel sheet piles are driven in a forward sequence; otherwise, beating in reverse sequence; when the steel sheet piles at the two ends of the screen wall are kept vertical, the steel sheet piles can be driven in a reciprocating sequence; when the length of the steel sheet pile wall is long, the steel sheet pile wall can be driven in a composite sequence, and the steel sheet pile wall is tightly buckled to ensure that the steel sheet pile wall is smoothly folded.
When the concrete ring beam is constructed, the steel sheet pile ear plates are cut and prefabricated in a processing plant in advance according to design requirements, the steel sheet pile ear plates are transported to a construction site after the quality meets the requirements, and field measurement personnel mark the welding position in advance by using markers such as chalk and the like, so that the welding and point finding of workers are facilitated;
after the soil surface below the ring beam is leveled, a white plastic cloth bottom film and a side mold are circularly paved, the shape of the plastic cloth on the inner side of the groove of the steel sheet pile is trimmed in advance, and the plastic cloth can be directly placed into the groove when the plastic cloth is used;
the main reinforcements of the ring beam, the types, the intervals and the quantity of the stirrups are calculated according to the design, the anti-falling reinforcements are welded after the main reinforcements are bound, the anti-falling reinforcements are required to be arranged below the main reinforcements of the top layer, the side formwork is connected through binding wires and is formed by customizing and combining a bamboo rubber plate and a square timber, on-site assembling personnel refine units according to the size of a circular section and then perform assembling operation, the joint of each side formwork unit is sealed, and the leakage is prevented when concrete is poured;
the ring beam concrete needs to be maintained to 75% in strength and then is demoulded; and meanwhile, the displacement monitoring points are arranged, and the arrangement requirement meets the relevant standard requirement.
During subsequent segment construction and bottom sealing, the foundation pit is lowered to 1m below the designed foundation pit according to the requirement of precipitation in the pit, earthwork is excavated layer by layer to 20-30 cm before the designed elevation, the earthwork is continuously excavated downwards by adopting a manual excavation method, a certain designed thickness is overexcavated, the soil surface is leveled, pit bottom reinforcing steel bars are bound, and concrete is poured to achieve the purposes of hardening and bottom sealing, when the foundation pit is excavated, if the soil with lower bearing capacity such as organic soil, miscellaneous filling soil, ploughing filling soil and the like is encountered, a flaky stone (or pachyrhizus stone) extrusion and silt replacement method can be adopted, the thickness of the cast and filled flaky stone (or pachyrhizus stone) is not less than 0.5m, and the bearing capacity of the foundation is not less than 120KPa (after depth correction is carried out) (filling according to the design drawing requirement).
The invention has the beneficial effects that: the construction method has the advantages of short construction period, turnover use, low cost, higher support strength, sufficient underground space and high safety, improves the construction safety and the construction efficiency, and is beneficial to protecting the environment;
the steel sheet pile and the reinforced concrete ring beam are connected together and mutually occluded to form an integral stable structure system by utilizing the steel sheet pile and the reinforced concrete ring beam inner support as a supporting structure, and the integral stable structure system is reasonable in stress, high in supporting strength and free of stress concentration. The mechanical properties of the reinforced concrete ring beam, such as high compression resistance, high torsion resistance and high bending resistance, are greatly exerted.
The clearance of the underground working surface is sufficient, only the annular reinforced concrete support exists in the foundation pit support, the support is not arranged in the rest space, the pipe section and the box culvert section can be conveniently hoisted into the well, the clearance of the working surface is sufficient, and no collision can occur; meanwhile, other conveying pipelines (a mud conveying pipe, a mud discharging pipe, a power transmission line and the like) can be conveniently arranged on the ladder for people to get on or off. The turnover rate is high, and the construction cost is low;
after the engineering construction in the pit is finished, backfill is carried out according to design requirements in a layered mode, at the moment, corresponding concrete ring beams (serving as backfill and improving the bearing capacity of the foundation) need to be broken, reinforcing steel bars are recycled, steel sheet piles are pulled out after the concrete ring beams are backfilled to the ground layer by layer, the steel sheet piles are recycled and used by the next working well, compared with a concrete continuous wall, the reinforced concrete structure is replaced by the steel sheet piles at the same space position, and cost is greatly reduced.
Detailed Description
In order to clearly illustrate the technical features of the present solution, the present solution is explained below by way of specific embodiments.
A pipe jacking well enclosure excavation supporting method comprises the following steps:
(1) leveling the field: leveling a pre-constructed field, removing foreign matters on the ground, erecting a surrounding barrier of the construction field according to the requirement of green construction, closing in time, and determining the ground position of an excavated pipe jacking well according to the design requirement;
(2) and (3) dewatering well construction: arranging 4 dewatering wells on the ground at the periphery of a starting well to be excavated (the number of the dewatering wells can be properly increased according to the underground water level condition and the excavation depth condition so as to achieve a dewatering effect), arranging 1 dewatering well in the starting well, and performing pumping operation 1 week ahead;
(3) constructing a steel sheet pile: according to the design of a starting well, setting out a line in a construction area, and inserting and driving a single row of annular closed steel sheet piles;
(4) excavating the earth on the first layer: carrying out earthwork excavation in a construction range, synchronously carrying out sand-free pipe removal of an inner dewatering well, and carrying out concrete ring beam construction after the earthwork excavation reaches the bottom elevation of the first layer of concrete ring beam;
(5) and (3) concrete ring beam construction: welding steel sheet pile ear plates, laying concrete ring beam bottoms and side templates, binding main steel bars on an enclosure, welding anti-falling steel bars, finally, erecting a concrete template support, pouring concrete of the concrete ring beam, and removing the template after the strength reaches 75% of the design requirement to form the concrete ring beam support;
(6) subsequent segment construction and bottom sealing: and (5) repeating the step (4) and the step (5), and after excavating to the designed bottom elevation of the foundation pit, performing bottom sealing concrete pouring.
The steel sheet pile adopts a fixed modulus Larsen IV type steel sheet pile, the joint of the steel sheet pile is fastened, and the inclination of each steel sheet pile is not more than 2%.
The first layer of earthwork excavation is earth surface soil excavation performed after the construction of the steel sheet pile is finished, the excavation depth of the first layer of earthwork excavation meets the height of the first layer of concrete ring beam structure, and the supporting effect of the fender pile on the soil body meets the soil body stability requirement.
In the steel sheet pile construction step, 10-20 steel sheet piles are inserted into the guide frame in rows to be driven in a screen shape, firstly, a group of steel sheet piles at two ends of the screen wall are driven to a designed elevation or a certain depth, the verticality is strictly controlled, and then the steel sheet piles are driven in the middle according to the height of 1/3 or 1/2 steel sheet piles in sequence.
The bottom die of the concrete ring beam is made of plastic.
A pipe jacking well enclosure structure comprises a plurality of steel sheet piles and concrete ring beams arranged on the inner sides of the steel sheet piles, wherein the steel sheet piles form an annular cofferdam.
The steel sheet pile adopts a Larsen IV type steel sheet pile with a fixed modulus, and the inclination of each steel sheet pile is not more than 2%.
The bottom die and the side die of the concrete ring beam are made of plastic materials.
The pipe jacking well enclosure structure is realized according to a pipe jacking well enclosure structure excavation supporting method.
The dewatering well construction method specifically comprises the following steps:
measuring well position
According to the measurement control point that design unit provided, measure the unwrapping wire and confirm the well point position, excavate the well point, precipitation well spacing slot upper shed line 1m arranges, excavates a little pit, and is about 500mm deep to catchment when trompil, and be connected little pit and sump pit with the ditch, so that excrete unnecessary water.
Drilling machine in position
And a hole is formed by adopting a reverse circulation drilling machine, and a vehicle-mounted reverse circulation power head drilling machine is selected as the reverse circulation drilling machine. The hoisting equipment is operated by a hoisting personnel with a professional license, and a specially-assigned person commands the hoisting equipment. When the pile driver is installed, three points are arranged in a line, namely the center of a drill rod, the center of a rotary table and the center of a pile hole are on the same plumb line, so that the verticality of a drilled hole is guaranteed, and the deviation between the center of the rotary table and the center of the pile hole is less than or equal to 10 mm. The installation of the drilling machine must be stable and firm, displacement cannot occur during drilling, the base is cushioned, and the drilling machine is frequently checked during drilling. After the equipment is installed in place, the equipment is carefully leveled and firmly installed, and the equipment is firstly tried before operation so as to prevent mechanical failure during hole forming. All electromechanical equipment needs safe and reliable wiring, and a cable buried pipeline on a transportation road is protected. The installation, use, removal, disassembly and maintenance of each piece of equipment are operated and used according to the operating instruction.
Preparation of slurry
High-plasticity bentonite is selected for preparing the slurry.
Fourthly, drilling
A. And the circulating system is arranged, namely the circulating system is reasonably arranged according to the actual situation of the field, and the flushing liquid is required to circulate smoothly, so that the drilling slag is easy to remove. The mud pit capacity is not less than 5m3 to ensure the normal circulation of the flushing liquid. When drilling a hole, firstly lightly pressing and slowly drilling, controlling the pump amount, and gradually increasing the rotating speed and the drilling pressure after entering a normal working state. Before formal construction, trial hole forming is carried out;
B. the drilling operation needs to be continuously carried out, and when the drilling is stopped due to the reason, the drill bit needs to be lifted away from the bottom of the hole by more than 5m so as to prevent the collapse hole from burying the drill;
C. during the drilling process, the stratum change is noticed, and different drilling methods are adopted for different soil layers. When drilling in hard clay, loosening the hoisting steel wire rope by using a first gear of rotating speed, and freely advancing; when drilling in common clay and sand clay, the drilling tool can freely advance with second gear and third gear rotating speed; when the silt soil is rich in underground water and easy to collapse, low-grade slow drilling is adopted, the stirring of the silt soil by a drill bit is reduced, and the specific gravity of slurry is increased and the water head is increased to strengthen the wall protection and prevent the collapse of the hole;
D. when drilling, decompression drilling is needed, even if the bit pressure born by the bottom of the hole does not exceed 80% of the sum of the gravity of the drill bit and the gravity of the weight minus the buoyancy, the drill rod can be kept in a vertical state, the drill bit can rotate vertically and stably, and the phenomena of inclined holes, bent holes and hole expansion are avoided or reduced.
Fifthly, cleaning holes
And (3) timely cleaning and lifting the hole after the designed hole depth is reached, lifting the drill bit away from the hole by 15-20 cm when the hole is cleaned, inputting slurry for circular hole cleaning, and controlling the specific gravity of the slurry and adjusting the performance of the slurry. The sand content of the fresh slurry in the hole is gradually reduced to a stable and non-settling degree.
Hanging non-sand concrete pipe
The down pipe adopts a suspended tray down pipe method, and the pipe barrel must be tightly packaged by a gauze in a silt layer section to prevent sand gushing. The sand cushion layer is firstly backfilled before the water filter pipe is arranged, then the settling pipe (concrete solid wall pipe) is arranged, then the concrete water filter pipe is arranged, and the upper pipe and the lower pipe are bound and connected by bamboo skin (thin bamboo) iron wires. When the pipe is to be lowered, the center of the pipe must be aligned with the center of the drilled hole. The lower pump is preferably suspended in the well by a hemp (or palm) rope, lowered to a designed depth and firmly tied at the well mouth.
Seventh, fill the filtering material
The filter material is medium coarse sand or fine stone, the thickness of the filter material is not less than 100mm, and the lower part of the filter material is 2m lower than the filter tube;
and after the pipe is lowered, immediately filling filter materials between the pipe wall and the hole wall, and slowly filling the filter materials from the periphery by using an iron mill during enclosing and tamping by using reinforcing steel bars to prevent the middle from being hollow. When filling, the filter material should be filled uniformly and continuously along the circumference of the well pipe and measured as filling. When the filling quantity, depth and calculation have larger accesses, the reason should be found and eliminated in time.
Eight well-flushing slurry discharging
The well is washed by a sewage pump or a submersible pump, the standard of well washing is based on that water pumped out from the well is clear, and the well washing time is required to be not less than 4 hours.
Ninthly drainage
The pumping equipment adopts a sewage pump or a submersible pump, a valve is installed in each well to adjust the flow, the valve is fixed by a clamp plate, the ground main pipe adopts a DE400 PE pipe, the passway pipe adopts a DE300 steel pipe, the wall thickness is 5mm, the steel pipe is sealed by concrete, a water collecting sedimentation tank is arranged according to the actual situation of pumping water of the foundation pit, and finally, the water collecting sedimentation tank is arranged to a nearby drainage pipe network along the main pipe.
Monitoring and maintenance of the r
And (4) observing the underground water level by using a precipitation well, wherein the underground water level is observed for 1-2 times every day at the early stage of precipitation. The dewatering well is required to be ensured to be intact during dewatering, regular inspection and maintenance are carried out on the dewatering well, problems are found and timely treated, and the safety of foundation pit construction is ensured. During precipitation, the foreign matters are forbidden to be put into the pipe well, the effect of pumping water is avoided being influenced, and the pipe well mouth is bound and sealed, so that the safety of ground personnel is guaranteed.
Backfilling after the water dropping of the pipe well is finished, and filling clay to seal the well when the pipe well is suggested to be positioned on a green belt or a sidewalk according to the determination of field technological tests; when the pipe well is positioned on the roadway, sealing the well by adopting a sand filling method, filling the well with sand, and then filling water into the sand in the well until the sand is filled; shortly after the well is full, the sand will settle in the well, and then the sand is again filled, water is poured, until the fill level is reached.
When the steel sheet pile is constructed, before piling, the steel sheet pile is checked one by one, common sheet piles with rusty connecting locking openings and serious deformation are removed, grease is coated in the locking openings of the steel sheet piles to facilitate driving and pulling out, the inclination of each pile is monitored at any time in the inserting and driving process is not more than 2%, when the inclination is too large and cannot be adjusted by a drawing-aligning method, the steel sheet piles are pulled and driven, the construction combining a one-by-one driving method and a screen driving method can be considered in the driving of the steel sheet piles, a screen driving method is suggested to be used in areas with dense sandy soil and high-viscosity soil, and the construction sequence of the screen driving method comprises a forward sequence, a reverse sequence, a reciprocating sequence, a middle-dividing sequence, a neutralizing sequence and a composite sequence. The construction sequence has direct influence on the verticality, displacement, expansion in the axis direction, the concave-convex of the steel sheet pile wall and the piling efficiency. Therefore, the construction sequence is one of the keys of the steel sheet pile construction process, and the selection principle is as follows: when the steel sheet piles which are arranged at the two ends of the screen wall are inclined reversely, the steel sheet piles are driven in a forward sequence; otherwise, beating in reverse sequence; when the steel sheet piles at the two ends of the screen wall are kept vertical, the steel sheet piles can be driven in a reciprocating sequence; when the length of the steel sheet pile wall is long, the steel sheet pile wall can be driven in a composite sequence, and the steel sheet pile wall is tightly buckled to ensure that the steel sheet pile wall is smoothly folded.
When the concrete ring beam is constructed, the steel sheet pile ear plates are cut and prefabricated in a processing plant in advance according to design requirements, the steel sheet pile ear plates are transported to a construction site after the quality meets the requirements, and field measurement personnel mark the welding position in advance by using markers such as chalk and the like, so that the welding and point finding of workers are facilitated;
after the soil surface below the ring beam is leveled, a white plastic cloth bottom film and a side mold are circularly paved, the shape of the plastic cloth on the inner side of the groove of the steel sheet pile is trimmed in advance, and the plastic cloth can be directly placed into the groove when the plastic cloth is used;
the main reinforcements of the ring beam, the types, the intervals and the quantity of the stirrups are calculated according to the design, the anti-falling reinforcements are welded after the main reinforcements are bound, the anti-falling reinforcements are required to be arranged below the main reinforcements of the top layer, the side formwork is connected through binding wires and is formed by customizing and combining a bamboo rubber plate and a square timber, on-site assembling personnel refine units according to the size of a circular section and then perform assembling operation, the joint of each side formwork unit is sealed, and the leakage is prevented when concrete is poured;
the ring beam concrete needs to be maintained to 75% in strength and then is demoulded; and meanwhile, the displacement monitoring points are arranged, and the arrangement requirement meets the relevant standard requirement.
During subsequent segment construction and bottom sealing, the foundation pit is lowered to 1m below the designed foundation pit according to the requirement of precipitation in the pit, earthwork is excavated layer by layer to 20-30 cm before the designed elevation, the earthwork is continuously excavated downwards by adopting a manual excavation method, a certain designed thickness is overexcavated, the soil surface is leveled, pit bottom reinforcing steel bars are bound, and concrete is poured, so that the purposes of hardening and bottom sealing are achieved, when the foundation pit is excavated, if the soil with lower bearing capacity such as organic soil, miscellaneous filling soil, plowing and filling soil and the like is encountered, a rubble (or pachyrhizus) extrusion and silt replacement method can be adopted, the thickness of the ripened rubble (or pachyrhizus) is not less than 0.5m, and the bearing capacity of the foundation is not less than 120KPa (after depth correction).
The technical features of the present invention which are not described in the above embodiments may be implemented by or using the prior art, and are not described herein again, of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and variations, modifications, additions or substitutions which may be made by those skilled in the art within the spirit and scope of the present invention should also fall within the protection scope of the present invention.
Claims (9)
1. A pipe jacking well enclosure excavation supporting method is characterized by comprising the following steps:
(1) leveling the field: leveling a pre-constructed field, removing foreign matters on the ground, erecting a surrounding barrier of the construction field according to the requirement of green construction, closing in time, and determining the ground position of an excavated pipe jacking well according to the design requirement;
(2) and (3) dewatering well construction: arranging a plurality of dewatering wells on the ground at the periphery of an initial well to be excavated, arranging 1 dewatering well in the initial well, and performing pumping operation 1 week in advance;
(3) constructing a steel sheet pile: according to the design of a starting well, setting out a line in a construction area, and inserting and driving a single row of annular closed steel sheet piles;
(4) excavating the earth on the first layer: carrying out earthwork excavation in a construction range, synchronously carrying out sand-free pipe removal of an inner dewatering well, and carrying out concrete ring beam construction after the earthwork excavation reaches the elevation of the bottom of the concrete ring beam;
(5) and (3) concrete ring beam construction: welding steel sheet pile ear plates, laying concrete ring beam bottoms and side templates, binding main steel bars on an enclosure, welding anti-falling steel bars, finally, erecting a concrete template support, pouring concrete of the concrete ring beam, and removing the template after the strength reaches 75% of the design requirement to form the concrete ring beam support;
(6) subsequent segment construction and bottom sealing: and (5) repeating the step (4) and the step (5), and after excavating to the designed bottom elevation of the foundation pit, performing bottom sealing concrete pouring.
2. The push bench well enclosure structure and excavation supporting method thereof according to claim 1, wherein the steel sheet pile is a fixed modulus Larsen type IV steel sheet pile, the steel sheet pile joint is fastened, and the inclination of each steel sheet pile is not more than 2%.
3. The push pipe well enclosure structure and the excavation supporting method thereof as claimed in claim 1, wherein the first layer of earthwork excavation is earth surface soil excavation performed after the construction of the steel sheet pile is completed, the excavation depth meets the depth of the first layer of concrete ring beam structure, and the supporting effect of the enclosure pile on the soil body meets the soil body stability requirement.
4. The pipe jacking well enclosure structure and the excavation supporting method thereof according to claim 1, wherein in the steel sheet pile construction step, 10-20 steel sheet piles are inserted into the guide frame in rows to be driven in a screen shape, a group of steel sheet piles at both ends of the screen wall are driven to a designed elevation or a certain depth, the verticality is strictly controlled, and then the steel sheet piles are driven in the middle in 1/3 or 1/2 plate pile heights in sequence.
5. The pipe jacking well enclosure structure and the excavation supporting method thereof according to claim 1, wherein the bottom mold and the side mold of the concrete ring beam are made of plastic materials.
6. A pipe jacking well enclosure structure is characterized by comprising a plurality of steel sheet piles and concrete ring beams arranged on the inner sides of the steel sheet piles, wherein the steel sheet piles form an annular cofferdam.
7. The push pipe well enclosure structure according to claim 6, wherein the steel sheet piles adopt Larsen type IV steel sheet piles with fixed modulus, and the inclination of each steel sheet pile is not more than 2%.
8. A pipe jacking well enclosure structure according to claim 7, wherein the bottom die and the side die of the concrete ring beam are made of plastic.
9. A pipe jacking well enclosure according to any one of claims 6 to 8, wherein the pipe jacking well enclosure is implemented according to the excavation supporting method of the pipe jacking well enclosure of claims 1 to 5.
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Application publication date: 20210730 |