CN114232607A - Frozen soil section drilled pile construction process - Google Patents
Frozen soil section drilled pile construction process Download PDFInfo
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- CN114232607A CN114232607A CN202111426839.8A CN202111426839A CN114232607A CN 114232607 A CN114232607 A CN 114232607A CN 202111426839 A CN202111426839 A CN 202111426839A CN 114232607 A CN114232607 A CN 114232607A
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- 230000002787 reinforcement Effects 0.000 claims abstract description 27
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- 229910001294 Reinforcing steel Inorganic materials 0.000 claims description 9
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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
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
- E02D15/04—Placing concrete in mould-pipes, pile tubes, bore-holes or narrow shafts
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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
- E02D5/66—Mould-pipes or other moulds
- E02D5/68—Mould-pipes or other moulds for making bulkheads or elements thereof
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
- G01K1/14—Supports; Fastening devices; Arrangements for mounting thermometers in particular locations
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Abstract
A frozen soil section bored pile construction process relates to the technical field of building construction. The method comprises the following steps: preparing a protective barrel clamp; secondly, exploration is carried out on the construction geology before drilling construction, and the depth position of the frozen soil layer is determined; drilling and double-layer casing construction; during the construction of the double-layer pile casing, the outer pile casing adopts a follow-up construction method, firstly, a rotary drilling rig adopts a drill bit with the same diameter as the outer pile casing to drill to the lower limit of the frozen soil layer, the outer pile casing is lowered to the lower limit of the frozen soil layer in sections, and the lower edge of the outer pile casing is lowered to the lower limit of the frozen soil layer; fourthly, installing a fixture and pouring medium coarse sand; and (V) mounting a temperature sensor on the reinforcement cage, wherein the temperature sensor is positioned on the reinforcement cage at the frozen soil layer. The problems that a frozen soil layer is easy to collapse and a pile foundation is damaged due to temperature change in the conventional construction of the frozen soil section drilling pile are solved; and the pile casing of the prior patent is too heavy, so that the pile casing is not convenient to be fixed in a pile hole in construction, and the quality of a drilled pile cannot meet the designed strength requirement.
Description
Technical Field
The invention relates to the technical field of building construction, in particular to a frozen soil pile construction technology.
Background
According to geological survey reports, the permafrost is rich frozen soil, multi-frozen soil, full frozen soil and an ice layer containing soil. The iced rich soil is gray brown, mainly comprising fine round gravels, coarse round gravels and granites, the ice film can be seen by naked eyes, the round gravels mainly comprise tuff, granites and the like, are in a round shape, have a general particle size of 2-50mm, and are filled with 30% of medium coarse sand. The frozen soil is gray brown, hard, mainly comprising sticky particles and particles, has uneven soil texture and contains 5-10% of impurity sand, the ice can be seen by naked eyes, the ice film is seen around the soil particles in the rock core, but the thickness of the ice layer is less than 2.5cm, and the ice content in the volume accounts for about 10% -15%. The layer is distributed on the lower edge of the bearing platform with slightly higher topography, is partially exposed and is 1.3 to 3.5m thick. The saturated frozen soil is gray brown, hard, mainly sticky and powdery, has uneven soil texture and contains 5-10% of impurity sand, the segregated ice can be seen by naked eyes, layered or obviously oriented ice strips can be seen in the core, but the thickness of the ice layer is less than 2.5cm, and the ice content in the volume accounts for about 35% -45%. Partially exposed, the thickness of the layer is 1.2 to 4.5 m. The soil-containing ice layer is gray brown, hard, mainly sticky and powdery, uneven in soil quality, and contains 5-10% of impurity sand, the segregated ice can be seen by naked eyes, the ice thickness is greater than 2.5cm, and the ice content in volume is about 70-80%. Partially revealed, revealing a layer thickness of 2.0 m.
The frozen soil has rheological property, the long-term strength of the frozen soil is far lower than the instantaneous strength, and two dangers are required to be faced when building engineering structures in a frozen soil area: frost heaving and thaw sinking. Therefore, the existing pile foundation construction schemes for structures such as railways, roads and the like in high-latitude and high-cold areas are few, and the problems that the frozen soil layer is easy to collapse and the pile foundation is damaged due to temperature change cannot be well solved; and no efficient irrigation bored pile construction method is available for pile foundation construction in severe cold mountain areas with complicated geological stratification.
In the building construction, the problem of the pore-forming of the bridge bored pile in the permafrost region always puzzles the majority of technical personnel, under the geology of the permafrost layer, if a single pile casing is adopted for conventional construction, when a drilling machine drills into the permafrost layer, the impact force of a drill bit of the drilling machine generates thermal disturbance in the hole, so that the permafrost layer nearby the hole is melted to cause the hole collapse phenomenon, and the pore-forming rate of the bored pile is difficult to ensure. Therefore, the construction efficiency is low, the construction period is prolonged, the cost is high, and the construction quality is difficult to ensure.
Chinese patent document CN102071687B discloses a method for manufacturing a bored pile casing, which is suitable for a novel bored pile casing for permafrost geology and a manufacturing method thereof. The technical scheme is as follows: a group of large outer-layer protection cylinders are concentrically arranged on the outer sides of the small inner-layer protection cylinders, fixing slurry is filled between the small inner-layer protection cylinders and the large outer-layer protection cylinders, and the small inner-layer protection cylinders and the large outer-layer protection cylinders are bonded and fixed, so that formed holes are not deformed, and collapse or expansion caused by orifice collapse and frost soil in the holes are prevented from melting. The method is used for pore forming in permafrost areas in bridge engineering construction.
The existing construction of the frozen soil section drilling pile has the problems that a frozen soil layer is easy to collapse and a pile foundation is damaged due to temperature change. During specific construction, if the temperature of a frozen soil layer is too low, the strength of a poured concrete pile is low, and the method for manufacturing the pile casing of the drilled pile disclosed by the Chinese patent is characterized in that the small casing on the inner layer and the large casing on the outer layer are bonded and fixed by filled fixing slurry, so that the pile casing is too heavy, the pile casing is not convenient to fix in a pile hole during construction, the pile casing cannot be taken out for reuse, and the quality of the drilled pile cannot meet the designed strength requirement.
Disclosure of Invention
The invention provides a frozen soil section drilled pile construction process, which solves the problems that a frozen soil layer is easy to collapse and a pile foundation is damaged due to temperature change in the conventional frozen soil section drilled pile construction; and the pile casing of the prior patent is too heavy, so that the pile casing is not convenient to be fixed in a pile hole in construction, and the quality of a drilled pile cannot meet the designed strength requirement.
In order to solve the problems, the invention adopts the following technical scheme: the frozen soil section bored pile construction process comprises the following steps:
preparing a protective barrel clamp which consists of an inner protective barrel, an outer protective barrel and a clamp;
secondly, exploration is carried out on the construction geology before drilling construction, and the depth position of the frozen soil layer is determined;
drilling and double-layer pile casing construction, wherein when the frozen soil section is positioned at the bottom of the bearing platform and below the bearing platform, the double-layer pile casing construction is adopted; during the construction of the double-layer pile casing, the outer pile casing adopts a follow-up construction method, firstly, a rotary drilling rig adopts a drill bit with the same diameter as the outer pile casing to drill to the lower limit of the frozen soil layer, the outer pile casing is lowered to the lower limit of the frozen soil layer in sections, and the lower edge of the outer pile casing is lowered to the lower limit of the frozen soil layer;
replacing a drill bit which is the same as the inner side casing, continuously drilling to 0.5m below the lower limit of the frozen soil layer, and then lowering the inner side casing;
fourthly, mounting and pouring medium coarse sand by using a fixture, fixing the inner and outer side protective cylinders by using the fixture after the inner and outer side protective cylinders are lowered, uniformly arranging three or four fixtures at the upper ends of the inner and outer side protective cylinders along the circumference, and clamping two jaws at the lower ends of the fixtures, wherein the two jaws are clamped at the outer sides of the inner side protective cylinder and the outer side protective cylinder respectively; the gap between the double-layer protecting cylinders is backfilled by medium coarse sand;
after the protective cylinder is installed, the drill bit is replaced to normally drill;
manufacturing and installing a reinforcement cage, wherein a temperature sensor is installed on the reinforcement cage, the reinforcement cage is installed in a pile hole, and the temperature sensor is located on the reinforcement cage at the position of the frozen soil layer;
and (VI) pouring concrete into the pile hole by adopting an underwater guide pipe method.
Further, the frozen soil section bored pile construction process provided by the invention has the following characteristics: in the drilling construction, taking slag samples and bagging every 0.5 m; according to the upper limit position and the lower limit position of the frozen soil layer displayed by the construction drawing survey report, taking slag samples every 0.3m at geological change positions and bagging, according to on-site actual sampling, judging that the geological conditions are consistent with the design of the drawing by design unit personnel, and determining the upper limit elevation and the lower limit elevation of the on-site actual frozen soil layer.
Further, the frozen soil section bored pile construction process provided by the invention has the following characteristics: and (4) brushing 1cm of asphalt residual oil on the outer side of the inner side casing before the inner side casing follows.
Further, the frozen soil section bored pile construction process provided by the invention has the following characteristics: four limiting reinforcing steel bars are added on each layer of the outer wall of the inner side protective cylinder, the limiting reinforcing steel bars are radially arranged and welded with the inner side protective cylinder, and a gap of 1cm is reserved between the limiting reinforcing steel bars and the inner wall of the outer side protective cylinder.
Further, the frozen soil section bored pile construction process provided by the invention has the following characteristics: the upper ends of the inner and outer protective cylinders are 0.5m higher than the ground.
Further, the frozen soil section bored pile construction process provided by the invention has the following characteristics: removing the fixture after concrete pouring, pulling out the outer side pile casing, and cutting off the pile casing above the pile top after the foundation pit is excavated; the inner side protection sleeve is not pulled out.
Further, the frozen soil section bored pile construction process provided by the invention has the following characteristics: monitoring the temperature of the frozen soil section, wherein the conditions of ice-rich frozen soil, multi-frozen soil, full frozen soil and an ice layer containing soil are determined according to the ice-containing condition of the frozen soil section; in the early construction period, two drilled piles are selected from each soil layer to be provided with temperature sensors, and frozen rich soil, frozen full soil and soil-containing ice layer are respectively selected for construction; the temperature sensors are placed on the pile foundation reinforcement cage, are arranged at the upper limit, the middle limit, the lower limit and 1m below the lower limit of the frozen soil layer according to the position of the frozen soil layer, and are installed on the reinforcement cage; and measuring the temperature every 6 hours after the bored pile is poured, and making a temperature recording table for providing reference for subsequent construction.
The invention has the technical effects that:
1. adopt the double-deck section of thick bamboo construction of protecting, the inside and outside protects a section of thick bamboo and passes through fixture fixed to the coarse sand in pouring, protect a section of thick bamboo and fix firmly in the stake hole, and then effectual frozen soil layer of avoiding leads to collapsing hole and pile foundation to be damaged because of temperature variation easily.
2. The inner and outer side pile casings are constructed respectively, the pile casing is light in weight and convenient to construct.
3. And after the concrete pouring is finished, the fixture is dismantled, the outer side protective barrel is pulled out, and the pulled out protective barrel can be utilized, so that the material is saved.
4. And monitoring the temperature of the frozen soil section by utilizing a temperature sensor pre-embedded in the frozen soil layer concrete. In the early construction period, two drilled piles are selected from each soil layer and are installed with temperature sensors according to the temperature change after pile forming, if the temperature is too low, the subsequent drilled pile construction can be carried out after the temperature rises, so that the strength of all the piles in the engineering can meet the requirement, and the quality of the drilled piles can meet the designed strength requirement.
Drawings
Process flow chart of percussion drilling construction of drilled pile
FIG. 1 is a flow chart of the bored pile construction process of the present invention;
FIG. 2 is an elevation view of a section of frozen earth of a bored pile of the present invention;
FIG. 3 is a cross-sectional view of the inner and outer shrouds;
FIG. 4 is a cross-sectional view A-A of FIG. 3;
FIG. 5 is a schematic view of the inner and outer casing and the frozen soil pile in the construction of the present invention.
Description of the symbols of the drawings: the device comprises a drilling pile 1, a drill bit 2, an inner side protective barrel 3, an outer side protective barrel 4, a clamp 5, medium coarse sand 6, a permafrost lower limit 7, a permafrost upper limit 8 and limiting reinforcing steel bars 9.
Detailed Description
The present invention will be described in detail with reference to the following preferred embodiments.
As shown in fig. 1-5, the frozen soil section bored pile construction process comprises the following construction steps:
the first step is as follows: preparation for construction
And (3) leveling the field, before construction, lofting by a measurer, leveling and compacting the area required by the construction of the drilled pile, placing the base of the drilling machine on a solid soil layer, and detecting the bearing capacity after the construction of the construction platform is finished to confirm whether the safe operation requirement of the drilling machine can be met. The construction site reaches the condition of tee joint and level, so that the construction road is ensured to be smooth, the construction materials are convenient to put in place, the construction site cannot be influenced by accumulated water, and the sewage generated in the construction process is precipitated and clarified to be reused.
The second step is as follows: pile position lofting
Pile position measurement, measurement data, re-checking by hand exchange, and finally submitting to the audit of a technical responsible person for supervision engineer for approval. The site measurement base line and the level point need to be used after repeated measurement. The survey crew uses the RTK lofting pile position and drives in an obvious mark, and pile position lofting should ensure accuracy. And after the lofting is finished, the drill can be started after the supervision and rechecking. And cross-shaped pile protectors are manufactured at the pile foundation point positions, so that the piles cannot be damaged, and construction and checking are facilitated.
The third step: drill in place
The pile foundation adopts a rotary drilling rig, the drilling rig is stably placed, the bottom frame is horizontal, the site is leveled and compacted before the drilling rig is in place, and meanwhile, the foundation bearing capacity detection meets the construction requirements of the drilling rig. After the drilling machine is in place, pile position centering is carried out, and the center of the drill bit, the intersection point of the pile protection cross line and the center of the pile position are located on the same vertical line.
On-site retesting of deviation of drill bit and hole site
The fourth step: clamp for preparing protective cylinder
The cylinder protecting clamp consists of an inner cylinder 3, an outer cylinder 4 and a clamp 5, and the inner cylinder 3 and the outer cylinder 4 are coated with asphalt residual oil.
The fifth step: drilling in
Drilling to the lower limit of the frozen soil layer, enabling the outer side protection cylinder to follow to the lower limit of the frozen soil layer, and enabling the lower edge of the outer side protection cylinder to reach to the lower limit of the frozen soil layer. The construction geology is explored before construction, and the depth position of the frozen soil layer is determined. During drilling, the drilling speed is adjusted according to the actual soil layer situation on site, the drilling is performed at a low speed at the beginning, and then the drilling is gradually shifted to normal so as to avoid inclined holes, bent holes and hole expansion.
During drilling, a drilling original record table and a temperature measurement record table are timely, faithfully and accurately filled, and slag sampling and bagging are carried out every 0.5m in the drilling process; according to the upper limit position and the lower limit position of the frozen soil layer displayed by the construction drawing survey report, taking slag samples every 0.3m at geological change positions and bagging, according to on-site actual sampling, judging that the geological conditions are consistent with the design of the drawing by design unit personnel, and determining the upper limit elevation and the lower limit elevation of the on-site actual frozen soil layer. And a temperature sensor is arranged on the steel reinforcement cage, and the temperature sensor is arranged in the frozen soil layer when the steel reinforcement cage is arranged in the pile hole.
A sixth step: construction of double-layer pile casing
The procedure is divided into the following two cases:
1. placing the protecting cylinders on the bearing platform and above the frozen soil section to a position 0.5m below the lower limit of the frozen soil layer, placing a section of steel protecting cylinder when drilling for 3m, normally drilling by using a rotary drilling rig when the protecting cylinders reach 0.5m below the lower limit of the frozen soil, and removing the protecting cylinders after concrete pouring is finished;
2. when the frozen soil section is positioned at the bottom of the bearing platform and below the bearing platform, a double-layer long pile casing is adopted for construction. During the construction of the double-layer protective cylinder, the outer protective cylinder adopts a follow-up construction method, firstly, a rotary drilling drill adopts a drill bit with the same diameter as the outer protective cylinder to drill, steel protective cylinders are put down in sections, and the length of each section of steel protective cylinder is 3 m; and when the outer side protective cylinder reaches the lower limit position of the frozen soil, the drill bit which is the same as the inner side protective cylinder is replaced, the drilling is continued for 0.5m, and then the inner side steel protective cylinder is lowered.
A seventh step of: coarse sand in fixture installation and pouring
After the inner and outer side protection cylinders are lowered, the inner and outer side protection cylinders are fixed by using clamps, three or four clamps are uniformly arranged at the upper ends of the inner and outer side protection cylinders along the circumference, two clamping jaws are arranged at the lower ends of the clamps, and the two clamping jaws are respectively clamped at the outer sides of the inner side protection cylinder and the outer side protection cylinder and are welded and fixed; and a gap between the double-layer protection cylinders is backfilled by medium coarse sand, and the drill bit is replaced to normally drill after the protection cylinders are installed.
The diameter of the outer side pile casing is 40cm larger than that of the inner side pile casing, the wall thickness is 10mm, and the pile casing penetrates into the lower limit position of the frozen soil layer; the diameter of the inner side pile casing is 20mm larger than that of the drilled pile, the wall thickness is 10mm, the pile casing penetrates into the lower limit of the frozen soil layer by 0.5m, and the pile casing is not pulled out after concrete pouring is finished; before the inner pile casing is followed, 1cm of asphalt residual oil is coated on the outer side of the inner pile casing, so that the uplifting force of frozen soil on a pile foundation is reduced; meanwhile, four limiting reinforcing steel bars are added on each layer of the outer wall of the inner side protective cylinder, the distance between each layer is 2m, the central offset of the protective cylinder is prevented from exceeding the limit, a gap of 1cm is reserved between the limiting reinforcing steel bars of the inner side protective cylinder and the inner wall of the outer side protective cylinder, and the inner side protective cylinder is not pulled out. And (4) removing the clamp to pull out the outer side pile casing after concrete pouring is finished, and cutting off the pile casing above the pile top after the foundation pit is excavated.
And (5) preparing a slurry retaining wall, detecting the formed hole and cleaning the pile hole.
An eighth step: manufacturing and mounting of reinforcement cage
The steel reinforcement cage is processed in the reinforcing bar processing place is concentrated, confirms the kind, the model, the owner muscle radical etc. of reinforcing bar through quality inspector and supervision engineer according to the requirement of design drawing, goes out the scene after the acceptance check is qualified, and the steel reinforcement cage should adopt the plastic cloth to cover on the steel reinforcement cage top on the good channel steel frame of processing is deposited in the transport scene after. The reinforcing cage sets up 4 protective layer cushion blocks per 2.0m, and the cushion block adopts the circular concrete cushion block that is higher grade intensity than design pile body concrete, and cushion diameter 15cm passes from the cushion center with phi 10mm round steel, welds on reinforcing cage owner muscle, guarantees that the reinforcing cage protective layer thickness is 70 mm.
The hanging ribs are steel bar cage elevation positioning ribs and are made of phi 16mm steel bars, the upper portions of the hanging ribs are made into rings with the diameter of 10cm, 2 hanging ribs are arranged on the top of each steel bar cage, steel pipes penetrate through the hanging rib rings to cross the tops of the pile casings and the sleepers, the diameter of each steel pipe is 70mm, and the wall thickness is 5 mm. The sleeper is placed close to the protection cylinder, and the top surface of the sleeper is 5cm higher than that of the protection cylinder.
And a temperature sensor is arranged on the reinforcement cage, the reinforcement cage is arranged in the pile hole, the temperature sensor is positioned at the position of the frozen soil layer, and the temperature sensor is arranged on the reinforcement cage.
A ninth step: conduit installation
The guide pipe is integrally assembled and cannot be hoisted into the hole at one time, and the guide pipe is hoisted into the hole in a segmented mode, so that the hoisting time is shortened, the guide pipe is assembled in advance in a segmented mode, and connecting joints in the hoisting process are reduced. Before construction, the constructed guide pipes are subjected to a watertight test, and the sealing condition of the joints of the guide pipes without holes is checked. If the water leakage phenomenon is caused, the water-saving water dispenser can not be used, and needs to be removed and replaced in time. The water pressure of the conduit in the watertight test is not less than 1.5 times of the pressure of the clean water at the bottom of the hole.
After the reinforcing cage is installed, a pipe chuck is placed, a pipe is installed on the chuck to the bottom of a hole, the section of the bottom of the pipe is 4m, the section of the standard pipe is 3m, the sections of the adjusting section are 2m, 1.5m, 1.0m and 0.5m, the inner diameter is 260mm, and the pipe is assembled and recorded according to the height 400mm higher than the bottom of the hole.
A tenth step: slurry preparation
A group of mud pit and a sedimentation tank are arranged between bearing platforms, and after the excavation of a foundation pit of the mud pit is finished, a double-layer thickened plastic cloth bedding bottom is used for preventing mud from seeping outwards. And the periphery of the mud pit is protected by adopting a standard guardrail enclosure.
The mud has the functions of protecting the hole wall and discharging slag, the method for preparing the mud is different according to different geological conditions, and the bentonite is adopted for making the mud according to field conditions. And in the construction process, adjusting the slurry index according to the geological condition. The mud liquid level in the hole is kept to be higher than the ground water level by more than 1 m. The mud pit and store up the thick liquid pond and set up the guardrail all around and enclose the fender, and the guardrail adopts assembled guardrail, and pole setting interval 2m is highly 1.2 m. Warning signs are hung on four sides of the guardrail, and warning lamps are hung at night. Carrying out dry-shifting on the fresh slurry percussion drill according to the specific gravity of 1.1-1.3g/cm, carrying out rotary drilling according to the specific gravity of 1.05-1.15g/cm high-speed flowering, carrying out viscosity of 16-22s, wherein the sand content is less than or equal to 4%, the colloidal content is not less than 95%, and the pH value is greater than 6.5.
The slurry circulating system is reasonably arranged according to a construction site, excavated dregs and waste slurry are timely cleaned and discharged in construction, and the dregs and the waste slurry are timely transported out of the site.
An eleventh step: cleaning hole and pouring concrete
The performance index of the slurry of the cast-in-situ bored pile after hole cleaning meets the following requirements: the mud discharged or drawn out from the hole has no particles with the diameter of 2mm to 3mm when being touched by a hand; carrying out heavy planting on the slurry with the specific gravity not greater than 1.10 g/cm; the sand content is not more than 2%; the viscosity is 17s to 20 s. And (4) checking the pore-forming quality and the sediment thickness at the bottom of the hole, and timely carrying out the next procedure after the pore-forming inspection is qualified, wherein the intermittent time is not too long.
The concrete used for designing the bored pile is C30/C45 underwater concrete, and the bored pile is poured by adopting an underwater guide pipe method. The underwater concrete has better workability, and the slump is controlled within 200 +/-20 mm. The pile casing is pulled out after the concrete is poured, when the pile casing is deeply embedded, the pile casing is pulled out, and the important attention is paid to preventing hole collapse and protecting the quality of the pile head of the pile.
A twelfth step: frozen soil section temperature monitoring arrangement
According to the ice-containing condition of frozen soil in the frozen soil section, the conditions of ice-rich frozen soil, multi-frozen soil, full frozen soil and an ice layer containing soil, two drilled piles are selected from each soil layer to be provided with temperature sensors, and the ice-rich frozen soil, the multi-frozen soil, the full frozen soil and the ice layer containing soil are respectively selected and constructed; the temperature sensor is placed on a pile foundation reinforcement cage to avoid contact with main ribs, is arranged at the upper limit, the middle limit, the lower limit and 1m below the lower limit of the frozen soil layer according to the position of the frozen soil layer, measures the temperature every 6 hours after pouring is finished, and prepares a temperature recording table to provide reference for subsequent construction.
The construction attention items of the bored pile in the frozen soil section are as follows:
(1) checking the upper limit and the lower limit of the frozen soil layer in the drilling process of the rotary drilling rig, immediately contacting an engineering technical department after the position of the frozen soil layer deviates, and confirming whether to adjust the implementation scheme on site by the technical department together with supervision and design.
(2) When the pile casings are buried, the double-layer pile casings are all 0.5m higher than the ground, the outer pile casings penetrate into the lower limit position of the frozen soil, the inner pile casings penetrate into the lower limit position of the frozen soil by 0.5m, the position of the frozen soil layer is confirmed by technicians according to slag samples when the pile casings follow, and the length of the pile casings is confirmed according to the upper limit and the lower limit of the frozen soil layer.
(3) The construction procedures of the cast-in-situ bored pile are tightly connected, the construction time is shortened as much as possible, and the times of measuring the sediment at the bottom of the hole are increased until the concrete begins to be poured.
(4) The temperature sensor on the installation steel reinforcement cage avoids contacting with the main muscle, welds the fixed temperature sensor of reinforcing bar at steel reinforcement cage stirrup position, transfers the steel reinforcement cage and pours the concrete in-process and make safeguard measure to temperature sensor, avoids destroying, influences follow-up construction.
(5) Before concrete pouring, temperature sensors are embedded, the sensors are embedded at the upper limit of frozen soil, the middle of a frozen soil layer and the lower limit of the frozen soil layer, two sensors are arranged on each layer, one sensor is protected by a thin-wall steel pipe of 1cm, and the time for frost return of a pile foundation is not less than 1 month generally.
(6) The double-layer pile casing is isolated by medium-coarse sand, the top surface of the pile casing is fixed by a double-layer pile casing clamp, and the clamp is dismantled to pull out the outer pile casing after concrete pouring is finished.
A thirteenth step of: frozen soil section bored pile construction quality assurance measure
1. The quality target is as follows: the construction process of the bored pile at the frozen soil section meets the requirements of the construction scheme, the quality of each subsection project reaches the quality standard, and the qualification rate reaches 100 percent.
2. Measurement and inspection quality assurance measures: (1) the engineering is controlled and measured by a total station, the measurement lofting must be rechecked by hand changing, and the field measurement must be retested and checked to ensure that the precision meets the requirement of the technical specification; (2) the measurement is intensified, the measurement is strictly closed, all adopted measurement equipment is calibrated regularly according to the regulation, and the measurement equipment can be put into use after being qualified; (3) a sound internal self-checking system is established, and strict three-checking is carried out on the procedures: a self-checking, mutual-checking and special-checking working system; (4) establishing a strict hidden engineering inspection and certification system, wherein a construction team and a command department of a hidden engineering project carry out self-inspection step by step, and the hidden engineering project and the supervision engineer carry out recheck after the hidden engineering project is qualified, and the inspection result is filled into the hidden engineering inspection and certification and signed by the two parties; (5) building a site laboratory and declaring qualification and measurement approval. And all the test equipment can be used after being qualified by a measurement supervision department. And (4) detecting various incoming raw materials, wherein the incoming raw materials are qualified when not detected and cannot be put into use. The quality of the concrete is strictly controlled in the construction process, and the strength, the slump, the workability, the concrete mixing time and the like of the concrete are ensured. Test pieces were produced as specified. (6) Instruments such as measuring instruments, test equipment and various instruments are regularly or irregularly verified according to the stipulations of the national metrology of people's republic of China.
3. Seasonal technical organization measures of construction: various preparation works before construction are fully made, and the progress and the mechanical labor configuration of each process are timely adjusted according to the site construction condition, so that the process greatly influenced by rainy seasons and cold seasons can be avoided from bad weather as much as possible. Reasonable construction arrangement and feasible guarantee measures are made. The enthusiasm of technical personnel is fully mobilized, the construction progress is accelerated by adopting a new technology, a new process, new equipment and a new material, the influence of adverse environment is overcome, and the engineering quality is ensured.
Claims (7)
1. Frozen soil section bored pile construction technology which is characterized in that: the method comprises the following steps:
preparing a protective barrel clamp which consists of an inner protective barrel, an outer protective barrel and a clamp;
secondly, exploration is carried out on the construction geology before drilling construction, and the depth position of the frozen soil layer is determined;
drilling and double-layer pile casing construction, wherein when the frozen soil section is positioned at the bottom of the bearing platform and below the bearing platform, the double-layer pile casing construction is adopted; during the construction of the double-layer pile casing, the outer pile casing adopts a follow-up construction method, firstly, a rotary drilling rig adopts a drill bit with the same diameter as the outer pile casing to drill to the lower limit of the frozen soil layer, the outer pile casing is lowered to the lower limit of the frozen soil layer in sections, and the lower edge of the outer pile casing is lowered to the lower limit of the frozen soil layer;
replacing a drill bit which is the same as the inner side casing, continuously drilling to 0.5m below the lower limit of the frozen soil layer, and then lowering the inner side casing;
fourthly, mounting and pouring medium coarse sand by using a fixture, fixing the inner and outer side protective cylinders by using the fixture after the inner and outer side protective cylinders are lowered, uniformly arranging three or four fixtures at the upper ends of the inner and outer side protective cylinders along the circumference, and clamping two jaws at the lower ends of the fixtures, wherein the two jaws are clamped at the outer sides of the inner side protective cylinder and the outer side protective cylinder respectively; the gap between the double-layer protecting cylinders is backfilled by medium coarse sand;
after the protective cylinder is installed, the drill bit is replaced to normally drill;
manufacturing and installing a reinforcement cage, wherein a temperature sensor is installed on the reinforcement cage, the reinforcement cage is installed in a pile hole, and the temperature sensor is located on the reinforcement cage at the position of the frozen soil layer;
and (VI) pouring concrete into the pile hole by adopting an underwater guide pipe method.
2. The frozen soil section bored pile construction process according to claim 1, characterized in that: in the drilling construction, taking slag samples and bagging every 0.5 m; according to the upper limit position and the lower limit position of the frozen soil layer displayed by the construction drawing survey report, taking slag samples every 0.3m at geological change positions and bagging, according to on-site actual sampling, judging that the geological conditions are consistent with the design of the drawing by design unit personnel, and determining the upper limit elevation and the lower limit elevation of the on-site actual frozen soil layer.
3. The frozen soil section bored pile construction process according to claim 1, characterized in that: and (4) brushing 1cm of asphalt residual oil on the outer side of the inner side casing before the inner side casing follows.
4. The frozen soil section bored pile construction process according to claim 3, characterized in that: four limiting reinforcing steel bars are added on each layer of the outer wall of the inner side protective cylinder, the limiting reinforcing steel bars are radially arranged and welded with the inner side protective cylinder, and a gap of 1cm is reserved between the limiting reinforcing steel bars and the inner wall of the outer side protective cylinder.
5. The frozen soil section bored pile construction process according to claim 1 or 3, characterized in that: the upper ends of the inner and outer protective cylinders are 0.5m higher than the ground.
6. The frozen soil section bored pile construction process according to claim 5, characterized in that: removing the fixture after concrete pouring, pulling out the outer side pile casing, and cutting off the pile casing above the pile top after the foundation pit is excavated; the inner side protection sleeve is not pulled out.
7. The frozen soil section bored pile construction process according to claim 1, characterized in that: monitoring the temperature of the frozen soil section, wherein the conditions of ice-rich frozen soil, multi-frozen soil, full frozen soil and an ice layer containing soil are determined according to the ice-containing condition of the frozen soil section; in the early construction period, two drilled piles are selected from each soil layer to be provided with temperature sensors, and frozen rich soil, frozen full soil and soil-containing ice layer are respectively selected for construction; the temperature sensors are placed on the pile foundation reinforcement cage, are arranged at the upper limit, the middle limit, the lower limit and 1m below the lower limit of the frozen soil layer according to the position of the frozen soil layer, and are installed on the reinforcement cage; and measuring the temperature every 6 hours after the bored pile is poured, and making a temperature recording table for providing reference for subsequent construction.
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