Zhongda Consulting small editor through the combing of the relevant content, collation of the pile foundation process flow of the relevant provisions of the content, the main content is as follows:
Pile foundation process flow:
Construction process flow: clean up the site, put the pile position, the supply of materials, the production of steel cages, the cylinder Burial, hole making, hole clearing, installation of steel cage, installation of conduit, second clearing, measurement of mud specific gravity, measurement of the thickness of sub-ballast, meet the design requirements and then pouring concrete, external drainage of slurry, clean up the slurry pool, concrete production, move the machine to make a hole.
Construction enterprise specific operation process content is as follows:
① Laying out the pile position and elevation
On the basis of the site three passes and one leveling, according to the information of the building measurement control network and the foundation layout plan, determine the pile axis grid control network and elevation datum point. Determine the center of the pile position, take the center as the circle center, and draw the circumference of the upper part (i.e. the first section) with the radius of the pile body plus the thickness of the retaining wall as the radius. Lime-scattering line is used as the pile hole excavation dimension line. And along the pile center position to the pile hole outside the four piles in the axis control points, with solid wooden stakes to mark. After the pile line is set, it must be reviewed by the relevant departments, do a good pre-check procedures after excavation.
② Excavation of the first section of the pile hole earth
Manual excavation of the pile hole should be carried out layer by layer from top to bottom, first digging the middle part of the earth, and then expand the periphery, effective control of the excavation of the pile hole cross-section size. The height of each section should be determined according to the soil conditions and construction program, generally 0.9m~1.2m is appropriate. Carry out a comprehensive measurement and calibration work after the completion of excavation, and carry out the support after the hole diameter and pile center are detected without error. After each section is dug, it must be straightened and trimmed according to the axis on the pile hole mouth, so that the arc of the hole wall is kept straight up and down.
③ Placement of additional reinforcement, support wall template
After the completion of the hole should be set up well circle, it is appropriate to prioritize the use of cast-in-place reinforced concrete well circle wall protection. When the pile diameter is not large, small depth, good soil quality, low water table can also be used in the case of plain concrete retaining wall. The thickness of the retaining wall should be based on the well ring material, performance, stiffness, stability, easy operation, simple construction and other requirements, and according to the stress conditions, as well as the soil side pressure and groundwater side pressure, through the calculation to determine.
Small diameter pile retaining wall of good soil quality may not put steel, but when the design requirements for placing steel or excavation meets the weak soil layer need to add steel, pile hole excavation is completed and acceptance of qualified, placing steel, and then installing the retaining wall template. The horizontal ring in the retaining wall should not be too much steel, vertical steel end should be bent into a U-shaped hook and driven into the soil surface below 100mm ~ 200mm, in order to connect with the next section of the retaining wall in the steel.
Sheathing wall template with thin steel plate, round steel, angle steel assembled and welded into a curved tool-type internal steel mold each section is divided into 4 pieces, large diameter piles can also be divided into 5 ~ 8 pieces, or with a combination of steel template prefabricated assembled. Adopt the way of dismantling the upper section and supporting the lower section to repeat the turnover use. Between the template with clamps, fasteners connected to fixed, but also in each section of the upper and lower ends of each set a channel steel or angle steel made of arc-shaped inner steel circle as the inner support, to prevent deformation of the inner mold. In order to facilitate the operation of the horizontal support is not set.
The first section of the retaining wall is 150mm~200mm above the ground level, and the thickness of the retaining wall is determined according to the design calculation, and is generally taken as 100mm~150mm. the first section of the retaining wall should be thicker than the following retaining wall by 50mm~100mm, and is generally taken as 150mm~250mm. the center of the retaining wall should be overlapped with the center of the pile, with a deviation of not more than 20mm, and the diameter of orthogonal to the center of the pile is not more than 50mm, with a deviation of not more than 50mm. The deviation is not more than 50mm, and the verticality of pile hole is not more than 0.5%. The verticality of the pile hole is not more than 0.5%. After meeting the requirements, the template can be stabilized with wooden wedges.
④ Pouring the first section of retaining wall concrete
The retaining wall concrete should be poured immediately after each section is dug, manually poured, manually pounded, and should not be used with vibrating rod. Concrete strength is generally C20, slump control at 70mm~100mm, to ensure the stability of the hole wall.
Sheathing wall concrete should be according to climatic conditions, the pouring shall be completed after 24h before demolding, generally in the next section of the pile hole earth excavation is completed. After dismantling, if there is honeycomb and water leakage in the retaining wall, it should be plugged or channelized.
After the pouring of the first section of retaining wall is completed, the axial control point in the pile hole will be led back to the retaining wall, and after further checking, it will be used as the datum for determining the center of the retaining wall in the next section, and at the same time, the relative elevation will be fixed in the retaining wall of the first section of the borehole with the level meter.
⑤ Check the pile (center) axis and elevation
After each section of the retaining wall is done, the pile cross axis and elevation must be measured at the upper mouth of the retaining wall, and then centered with the cross line, hanging line pendant to the bottom of the well casting, to check the vertical smoothness of the borehole wall with the radius of a ruler rod, and then trimmed. The depth of the well must be based on the datum point, and the pilot test is carried out root by root to ensure that the pile hole axis position, elevation, section size meets the design requirements.
6 Set up vertical transportation frame
After the first section of pile hole is made into a hole, it is started to set up vertical transportation bracket on the hole, the bracket has three wooden hitch, steel pipe hanger or wooden hanger, I-beam rail bracket, and it is required to set up a stable and firm.
⑦ Installation of electric hoist or winch
Installation of pulleys in the vertical transportation frame to give and electric hoist or winch wire rope, choose the appropriate location to install the winch.
Shallow piles and small pile holes can also use wooden hanger, wooden windlass or manual directly with the help of hemp rope as lifting tools. Ground soil transportation with dump trucks, wheelbarrows.
⑧ Installation of buckets, lighting, movable safety cover, pumps, ventilators
Installation of pulley block and buckets and pile hole center position coincides with the digging intuitively control the center of the pile and retaining wall support mold centerline.
Lighting at the bottom of the well must use low-voltage power supply (36V, 100W), waterproof with cover safety lamps. Wellhead on the fence. Cable segments are fixed with the guard wall, the length is moderate, to prevent collision with the bucket.
When the depth of the well is greater than 5m, there should be underground ventilation, strengthen the air convection in the well, send oxygen if necessary, and keep a close watch to prevent the harm of toxic gases. Operation of the upper and lower personnel to rotate operations, echo each other, the well personnel at any time to observe the situation of underground personnel, and effectively prevent personal safety accidents.
When the underground seepage is not large, the mud and water will be transported out with buckets as you dig, or dig a water collection pit at the bottom of the well, pump the water with a submersible pump, and strengthen the support. When the groundwater level is high, the drainage ditch is difficult to solve, you can set up a precipitation well precipitation.
Well installation of horizontal nudging activity safety cover: when someone operating in the well, cover the safety cover to prevent debris from falling into the well, unrelated personnel shall not be close to the mouth of the well, lifting the soil, and then open the safety cover, to ensure the safety of personnel in the well construction.
9 Excavation and transportation of the second section of the pile hole earth (edge repair)
From the second section, the use of lifting equipment to transport soil, downhole personnel should wear a good helmet, the well personnel chained to a good safety belt, the well mouth erected guardrail, the bucket away from the mouth of the well 1m to promote the cover plate, cover the mouth of the well, to prevent unloading of dirt, stones and other debris falling into the well injury. Bucket in the trolley after unloading soil (also can use I-beam rail will bucket out to dump truck unloading soil) and then open the well cover, down into the bucket loaded.
The pile hole is dug to the specified depth, the diameter of the pile hole and the arc of the wall is checked with a ruler, the top and bottom should be vertical and smooth, and the hole wall is repaired.
⑩ second section of the retaining wall support template
Place additional reinforcement, and connect with the vertical reinforcement reserved in the previous section, dismantle the first section of the retaining wall template, support the second section. The retaining wall template is used to dismantle the upper section and support the lower section in turnover. Make the upper section of the lower part of the retaining wall embedded in the lower section of the retaining wall of the upper part of the concrete, the upper and lower lap 50mm ~ 75mm. pile hole testing and checking after pouring the retaining wall concrete.
11 Pouring the second section of retaining wall concrete
Concrete delivered by bucket, artificial pouring, artificial vibration compact, concrete mixed with early strength agent determined by the test.
12 Check the axis and elevation of the pile (center)
Based on the locating line at the top entrance of the well, cast and trim section by section.
13 Cycle the work layer by layer
Dig the pile hole to the design depth, remove the virtual soil, check the soil quality, and the pile bottom should enter the depth of the holding layer specified in the design.
14 Excavation bottom part
The bottom of pile can be divided into two kinds: expanded bottom and non-expanded bottom. Excavation of expanded bottom pile should be first expanded bottom part of the pile body of the cylinder dug. And then in accordance with the size and shape of the bottom part of the expansion, from top to bottom cut soil expansion into the shape of the expanded bottom. Expanded bottom size should be in accordance with the design requirements, after completion of the removal of wall sludge, bottom of the hole residue, floating soil, debris, water, etc..
15 Check and acceptance
After the hole is completed, the pile diameter, expanding head size, bottom elevation, pile center, verticality of the wall, the thickness of the virtual soil, the bottom of the hole rock (soil) nature of the comprehensive comprehensive determination one by one. Make a good record of acceptance of the construction of the hole, and go through the hidden acceptance procedures. After passing the inspection, quickly seal the bottom, place the reinforcing cage, and pour the pile concrete.
16 Lifting and placing reinforcement cage
According to the design requirements for the acceptance of reinforcement cage, check the type of reinforcement, spacing, welding quality, diameter and length of the cage and the placement of protection block (card), fill in the acceptance record.
The reinforcement cage is lifted by crane and sunk into the pile hole. Hook a reinforcing hoop at the top of the cage with a hook, use channel steel as a cross-bar, hang the cage at the upper mouth of the shaft wall, keep the skeleton vertical by its own weight, control the elevation of the cage and the thickness of the protective layer. Prevent the cage from deformation when lifting, and pay attention not to collide with the hole wall.
If the cage is too long, it can be lifted in sections and welded vertically at the mouth of the hole.
17 Pouring pile concrete
Pile concrete should use ready-mixed concrete of the strength grade required by the design, and its slump should be tested before pouring, and at least one set of test blocks should be kept for each pile according to the regulations. Use the chute plus string bucket to pour into the well, the drop of concrete is not more than 2m, such as pumping concrete, you can directly move the discharge port of the concrete pump into the hole to cast the material. Pile hole depth of more than 12m is recommended to use concrete conduit continuous layered pouring, vibration and compacting. Generally pouring to the top surface of the bottom of the expansion, vibration, continue to pour the above part.
The diameter of the project pile are less than 1.20m, so in the construction process, the depth of 6m below the part of the concrete can be used to drop the concrete weight of the impulse, and then appropriate auxiliary artificial insertion of pounding to make it dense. The remaining 6m above the part of the layered pouring irrigation vibration compact.
When the hole seepage is large (can be more than 15mm/min rise rate of water in the hole as a reference), should be taken in advance to lower the water, water measures or the use of conduit method of filling underwater concrete. Underwater filling when the first casting amount must be enough to bury the bottom end of the conduit into the underwater concrete for more than 800mm.
18 seasonal construction
The construction of this project is in the hot summer, so in the construction process when the temperature is higher than 30 ℃, according to the specific conditions in the concrete mixed with retarder.
It is not suitable to carry out the construction of hand-dug pile holes in rainy days. If the construction is necessary, the site must be well drained to prevent the ground rainwater from flowing into the pile holes, and there should be water-blocking measures around the holes to prevent the rainwater from flowing into the holes.
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