Materials and machines
Cement: Ordinary portland cement or slag portland cement with a strength grade of not less than 32.5 shall be used.
Sand: medium sand is used, and the silt content is not more than 3%.
Gravel: Gravel or pebble with a particle size of 5~40mm and not more than 65,438+0/3 of the clear distance of main reinforcement, with a silt content of not more than 65,438+0%.
Water: It is advisable to use drinking water or clean water without harmful substances.
Admixtures and admixtures: according to climatic conditions, construction period and design requirements. They were determined by experiments.
Reinforcement: The grade and diameter of reinforcement shall meet the design requirements.
Pile extension material:
(1) welding pile connection: the steel plate is made of low carbon steel, and covered electrode adopts E43 series;
(2) Flange pile connection: steel plates and bolts shall be made of low carbon steel;
(3) Anchor pile connection with sulfur mastic: The mixture ratio of sulfur mastic shall be determined through tests.
Machines and tools:
(1) Pile-making machines and tools: steel bar straightener, bender, cutter, butt welder, spot welder, electric welder, concrete mixer, dump truck or trolley, plug-in high-frequency vibrator, etc.
(2) Transport equipment: large trailer, truck crane or crawler crane, skidding, etc.
(3) Piling machinery: diesel pile driver or vibration pile driver, drilling pile driver, press-in pile driver, etc.
(4) Pile grafting machine: electric welding machine, a special tool for boiling sulfur cement.
(5) Others: shovel, iron plate, platform scale, rubber hose, iron trowel, spirit level, theodolite, steel tape measure, spirit level, etc.
Cao Zuo Jian
making herbs into wool
(1) Various raw materials have been inspected, and the concrete mix ratio is proposed after trial mix.
(2) The prefabricated site meets the requirements.
(3) Complete machines and tools
(4) Joint review of the provided pile foundation layout and pile foundation construction drawing, and technical disclosure.
Transportation and stacking
(1) The strength of precast pile meets the requirements of hoisting and transportation.
(2) The stacking position meets the requirements.
(3) The lifting and transportation equipment is complete and can meet the requirements.
pile sinking
(1) Provide the engineering geological investigation report of the construction site, and supplement the in-situ test data such as static penetration test or standard penetration test when necessary.
(2) Remove ground and underground obstacles. The piling site should be flat and the bearing capacity of the foundation should be able to adapt to the normal operation of the piling machine; The drainage ditch should be kept clear at the construction site, and attention should be paid to earthquake prevention during construction.
(3) Before construction, the number of test piles shall be no less than 2. Determine the penetration and verify whether the piling equipment, construction technology and technical measures are appropriate.
(4) Prepare the construction organization design or construction scheme, and make detailed technical disclosure.
(5) The inspection data of precast piles are complete.
operative technique
process flow
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Production procedure: site layout → leveling and compaction → making fetal membranes → binding steel formwork → installing rings → pouring concrete → curing to 30% strength → supporting the upper formwork after formwork removal → painting isolation agent → stacking → curing to 70% strength → hoisting to 100% strength → transportation and stacking.
Flash butt welding or arc welding should be adopted for the main reinforcement connection of the reinforcement skeleton. The number of main reinforcement joints in the same section should meet the design requirements. If there is no design requirement, the following requirements shall also be met:
(1) The joint of main reinforcement in the same section shall not exceed 50%;
(2) The distance between two adjacent joints of main reinforcement shall be 35 times greater than the diameter of main reinforcement and not less than 500mm.
The longitudinal reinforcement of precast pile should be tensioned individually, and the stress control should be appropriate, and the tensile stress control of each pile should be consistent. After the longitudinal reinforcement is tensioned, it is bound with the transverse reinforcement.
Wooden formwork or steel formwork can be used to make formwork, which should be flat and firm, accurate in size and coated with isolation agent.
Pile-making concrete shall be continuously poured from the top of the pile to the tip of the pile, without interruption. When vibrating, it should be leveled while vibrating, so that it is solid inside and light outside.
After the precast pile is made, it shall be watered and maintained for not less than 7d. When steam curing is adopted, the natural curing days after steam curing should be appropriately increased.
When making precast piles by lap joint method, the following requirements shall be met:
(1) The contact surface between pile and adjacent pile and bottom die shall not be adhered.
(2) The pouring of the upper pile or adjacent pile shall be carried out after the concrete of the lower pile or adjacent pile reaches 30% of the design strength.
(3) Generally, the overlapping layers of piles should not exceed four.
Transport stacking
When transporting precast piles, the application of wood cushion should be stable and accurate, and the stacking number should not exceed three. It is forbidden to drag piles directly for transportation at the site. When transporting long piles, movable supports should be placed under the skids.
Precast piles should be stacked in layers on flat and solid ground according to specifications and pile number; Shoppers and lifting points should be kept on the same longitudinal section, and each layer of skids should be aligned up and down, and the number of piles should not exceed 4. The bottom stow-wood should be widened and thickened appropriately, or sleepers with good texture should be used to avoid the bottom layer from breaking due to the bending caused by the flooded site and the sinking of the stow-wood.
test pile
In the process of pile testing, if it is found that the actual geological conditions are inconsistent with the design data, it should be studied and handled with the relevant units. For piles with different sections and lengths, the number of blows per meter, the final penetration, the total number of blows, the elevation of the pile top, the time taken for pile connection and pile sinking should be recorded in detail and filed.
pile sinking
Pile sinking procedure: setting pile line → arranging pile points → positioning pile machine → positioning pile → correcting verticality → piling → measuring pile top elevation → moving drilling rig, and repeat the above procedures.
The axis positioning of pile foundation should start from the baseline given by the construction unit and be connected with the baseline network that controls the plane position. There should be no less than two leveling points near the piling area, and their positions should not be affected by piling.
The actual position of a single pile is driven vertically into the ground by reinforcing steel bars for 400~500mm, and after the reinforcing steel bars are pulled out, they are filled with lime. After the pile location is set out, the technical director of the supervision unit and the construction unit will review it, and the handover procedures will be handled after it is correct.
Before piling, the center line and elevation line per meter should be popped up on the adjacent sides of the pile, and a fixed scale should be set on the pile frame, and the elevation line per 100mm should be drawn on the pile delivery pipe or pile top.
For the lifting and positioning of piles, the hook attached to the pile frame is usually used to lift the piles, or a crane is equipped to send the piles to the proper position. Use the guide plate clamp or pile hoop of the pile frame to embed the pile into the two columns of the pile frame, vertically align with the center of the pile position, and correct the verticality, that is, the pile hammer, pile cap or pile feeder coincide with the center line of the pile body.
Check the following contents before piling:
(1) The clearance between pile cap or pile driver and pile shall be 5 ~ 10 mm. ..
(2) There should be suitable elastic pads, such as hardwood and rubber pads, between the hammer and the pile cap, and between the pile cap and the pile.
(3) The vertical deviation of pile insertion shall not exceed 0.5%.
The piling sequence shall be as follows:
(1) Dense pile groups should be driven symmetrically from the middle to two directions or around, or from one side to a single direction; When one side is adjacent to a building, it can be hit from the other direction of the adjacent building.
(2) According to the design elevation of foundation, it should be deep first and then shallow; According to the specifications of the pile, it should be large first and then small.
When the pile sinking method is adopted, the following provisions shall be met:
(1) If the buried depth of the pile cap is shallow, pile driving should be done before digging; If the pile cap is deeply buried, it is advisable to excavate the foundation pit before piling.
(2) When the pile top sinks to 400~600mm from the ground, a pile driver should be added to deliver the pile, and the longitudinal axis of the pile and the pile driver should be on the same axis.
When using the internal (external) water jet method for pile sinking, the following provisions shall be met:
(1) Jet piling is suitable for sandy soil and gravel soil.
(2) When the water reaches the last 1~2m, stop water injection and hammer to the specified elevation.
When using static pressure pile, the following requirements shall be met:
(1) Static pressure pile is suitable for soft soil layer, but not for sand interlayer with thickness greater than 2m.
(2) The pile driver should be fully weighted according to the soil conditions.
(3) The center lines of the pile cap, the pile driver and the pile body coincide.
(4) Pressing the same pile (section) should shorten the pause time.
When piling approaches the design elevation, the following contents shall be checked:
(1) Whether the pile cap and elastic cushion are normal.
(2) Whether the hammering is eccentric.
(3) Whether the pile top is damaged.
The above are collected and sorted by Zhong Da Consulting Company.
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