Construction preparation
Materials and machinery
Cement: It is advisable to use ordinary Portland cement or slag Portland cement with a strength grade of not less than 32.5.
Sand: Use medium sand with a mud content of no more than 3%.
Gravel: Gravel or pebbles with a particle size of 5~40mm and no greater than 1/3 of the clear distance between the main steel bars, and a mud content of no more than 1%.
Water: Drinking water or clean water without harmful substances should be used.
Admixtures and admixtures: determined through tests according to climatic conditions, construction period and design requirements.
Reinforcement bars: The grade and diameter of steel bars should meet the design requirements.
Piling materials:
(1) Welded pile connection: low carbon steel should be used for the steel plate and E43 series for the welding rod;
(2) Flange Piles: Steel plates and bolts should be made of low carbon steel;
(3) Sulfur cement anchor piles: The mix ratio of sulfur cement should be determined through testing.
Machines:
(1) Piling machines: steel bar straightening machine, bending machine, cutting machine, butt welding machine, spot welding machine, electric welding machine, concrete mixer, dump truck Or trolley, plug-in high-frequency vibrator, etc.
(2) Transport equipment: large trailers, truck cranes or crawler cranes, skids, etc.
(3) Piling machinery: diesel pile driver or vibration pile driver, drilling pile driver, press-in pile driver, etc.
(4) Piling equipment: electric welding machine, special tools for sulfur clay boiling and pouring.
(5) Others: shovels, iron plates, scales, rubber tubes, iron trowels, levels, theodolite, steel tape measures, level rods, etc.
Operating conditions
Pile making
(1) Various raw materials have been tested, and the concrete mix ratio has been proposed after trial mixing.
(2) The prefabricated site meets the requirements.
(3) Complete machinery and equipment
(4) Conduct a joint review of the provided pile foundation layout drawings and pile foundation construction drawings, and conduct technical explanations.
Transportation and stacking
(1) The strength of the prefabricated piles meets the requirements for lifting and transportation.
(2) The stacking location meets the requirements.
(3) Lifting and transportation equipment are complete and meet the required capabilities.
Pile driving
(1) Provide an engineering geological survey report of the construction site, and if necessary, supplement in-situ test data such as static cone sounding or standard penetration test.
(2) Clear above-ground and underground obstacles. The piling site should be flat, and the ground bearing capacity should be able to adapt to the normal operation of the pile driver; the construction site should keep drainage ditches clear, and pay attention to earthquake prevention issues 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 construction organization design or construction plan, and make detailed technical explanation.
(5) The inspection data of precast piles are complete.
(6) All pile-driving machines have entered the site and are in normal trial operation.
(7) The line setting and positioning has been completed.
Operation process
Process flow
Pile making
Production procedure: On-site layout → Leveling and compaction → Making fetal membrane → Binding Reinforcement formwork → install lifting rings → pour concrete → curing to 30% strength, remove the formwork and then support the upper formwork → apply isolation agent → stacking → curing to 70% strength and lifting → 100% strength transportation and stacking.
The connection between the main bars of the steel frame should be flash butt welding or arc welding. The number of main reinforcement joints configured in the same section should meet the design requirements. If there are no design requirements, the following regulations should also be met:
(1) The number of main reinforcement joints in the same section shall not exceed 50%;< /p>
(2) The distance between the joint sections of two adjacent main bars should be greater than 35 times the diameter of the main bars and not less than 500mm.
The longitudinal steel bars of prefabricated piles should be tensile-strengthed in a single pile, and stress control is appropriate, and the tensile stress of each pile should be controlled consistently. After the longitudinal steel bars are stretched, they are tied together with the transverse steel bars.
Wooden templates or steel molds can be used to make templates. They should be smooth and firm, accurate in size, and painted with isolation agent.
The concrete for making piles should be poured continuously from the top of the pile to the tip of the pile, and interruption is strictly prohibited. During vibrating, it should be leveled while vibrating and smoothing to achieve a solid interior and a smooth exterior.
After the prefabricated piles are made, they should be covered with water and maintained for no less than 7 days. When steam curing is used, the number of natural curing days should be appropriately increased after steam curing.
When making prefabricated piles by the overlapping method, the following regulations should be met:
(1) The contact surfaces between piles, adjacent piles and bottom molds must not be adhered.
(2) The pouring of the upper piles or adjacent piles should be carried out after the concrete of the lower piles or adjacent piles reaches 30% of the design strength.
(3) The number of overlapping layers of piles should generally not exceed four.
(4) The lifting ring of the pile should be vibrated and compacted.
Transportation and Stacking
When transporting prefabricated piles, wooden pads should be used to support them stably and in accurate positions. The number of stacked layers should not exceed three. It is strictly prohibited to directly drag the piles on the site for transportation. When transporting long piles, movable supports should be placed under the skids.
When stacking prefabricated piles, they should be stacked in layers on a flat, solid ground according to specifications and pile numbers; the pads and lifting points should be kept on the same longitudinal section, and each layer of pads should be aligned up and down. , the number of stacking layers should not exceed four. The bottom layer of pads should be appropriately widened and thickened, or sleepers with good texture should be used to prevent the bottom layer from breaking due to water logging in the site and sinking of the pads, which may be caused by bending.
Pile Testing
During the pile testing process, if it is found that the actual geological conditions are inconsistent with the design data, it should be investigated and handled with the relevant units. For piles of different cross-sections and lengths, the number of hammer blows per meter, final penetration, total number of hammer blows, pile top elevation, time taken to connect the pile in place, pile sinking time, etc. should be recorded in detail and kept on file.
Pile sinking
Pile sinking procedure: pile position line → lay pile points → pile driver in place → pile in place → correct verticality → pile driving → measure pile top elevation → move Drilling machine, repeat the above process.
The axis of the positioning pile foundation should start from the baseline given by the construction unit and be connected to the baseline network that controls the plane position. Leveling points should be set up near the piling area, the number should not be less than 2, and their locations should not be affected by piling.
The actual position of the single pile should be driven vertically 400~500mm into the ground with a steel drill. After the steel drill is pulled out, white ash is poured in and compacted. After the pile position is laid out, it will be reviewed by the technical person in charge of the supervision unit and the construction unit. If there is no error, the handover procedures will be carried out.
Before piling, the center line and the elevation line per meter should be popped up on the adjacent sides of the pile. At the same time, a fixed ruler should be set on the pile frame, and the elevation of every 100mm should be drawn on the pile feeding pipe or the top of the pile. Wire.
To lift and position the piles, the lifting hooks attached to the pile frame are generally used to lift the piles, or a crane is equipped to send the piles into place. Use the guide plate clamp or pile hoop of the pile frame to embed the pile in the two columns of the pile frame, align it vertically with the center of the pile position, and correct the verticality, that is, the pile hammer, pile cap or pile feeder coincides with the center line of the pile body.
The following should be checked before piling:
(1) The gap between the pile cap or pile feeder and the surrounding pile should be 5~10mm.
(2) There should be suitable elastic pads, such as hardwood, rubber pads, etc., between the hammer and the pile cap, and between the pile cap and the pile.
(3) The vertical deviation when the pile is inserted shall not exceed 0.5%.
The pile driving sequence should be carried out according to the following regulations:
(1) The dense pile group should be driven symmetrically from the middle to two directions or all around, or from one side to a single direction. ; When one side is adjacent to a building, the blow can be applied from the adjacent building to the other direction.
(2) According to the design elevation of the foundation, it should be deeper first and then shallower; according to the specifications of the piles, it should be larger first and then smaller.
When using the pile driving method to sink piles, the following regulations should be met:
(1) If the cap is buried shallowly, the piles should be driven first and then the soil is excavated; The cap platform is buried deep, so it is advisable to excavate the foundation pit first and then drive piles.
(2) When the top of the pile sinks to 400~600mm above the ground, a pile feeder should be added to feed the pile. The longitudinal axis of the pile and the pile feeder should be on the same axis.
When using the internal (outer) water injection method to drive piles, the following regulations should be met:
(1) The water injection method is suitable for sandy soil and gravel soil.
(2) When the water reaches the last 1~2m, the water injection should be stopped and hammered to the specified elevation.
When static pressure piles are used, the following regulations should be met:
(1) Static pressure piles are suitable for soft soil layers and are not suitable for medium-density or above sand with a thickness greater than 2m. Sandwich
(2) The pile driver should be equipped with a sufficient rated weight according to the soil conditions.
(3) The center lines of the pile cap, pile feeder and pile body coincide.
(4) The pause time should be shortened when pressing the same pile (section).
When the piles have been driven close to the design elevation, the following should be checked:
(1) Whether the pile caps and elastic cushions are normal.
(2) Whether the hammer is eccentric.
(3) Whether the top of the pile is damaged.
The control of penetration should be determined through test piles or pile driving tests.
(1) When the pile end (referring to the full cross-section of the pile) is located in the general soil layer (friction-based pile), the design elevation of the pile end is mainly controlled, and the penetration degree can be used as a reference.
(2) When the end of the end-bearing pile encounters hard (plastic) clay soil, medium-density or above silt soil, sandy soil, gravel soil, and weathered rock, penetration control is used Mainly, the pile end elevation can be used as a reference.
(3) The controlled penetration depth of friction piles and friction end-bearing piles should be based on the elevation, and the penetration degree can be used as a reference.
(4) When the penetration has been reached but the pile top elevation has not been reached, hammering should be continued for three arrays, and it should be confirmed that the penetration of 10 blows in each array is not greater than the value specified in the design. If necessary The construction control penetration should be determined in consultation with the relevant units.
When connecting piles, the upper and lower node lines must be ensured. The node processing of piles should comply with the following regulations:
(1) Welding piles: The surface of embedded iron parts should be kept clean ; The gap between the upper and lower piles should be filled with pad iron and welded firmly; symmetrical welding should be used during welding to ensure that the weld is high and continuous and full.
(2) Flange pile connection: It is advisable to use asbestos or felt lining between the upper and lower piles, tighten the nuts, hammer them several times before tightening again, and weld the nuts.
(3) Sulfur cement anchoring piles: The anchor bars should be cleaned and straightened in advance; there should be no accumulated water, debris and oil in the anchor hole; when connecting the piles, the node plane and the anchor hole should be Fill with sulfur cement; the pouring time of sulfur cement shall not exceed 2 minutes; the rest time after pouring shall comply with the following table; one set of test pieces shall be made for every 100 kg of sulfur cement semi-finished products.
Protection of finished products
Concrete precast piles can only be lifted when they reach 70% of the design strength. Transportation and piling can only be carried out when it reaches 100%. For long piles over 30m or piles with more than 500 hammer blows, the maintenance period should reach 28 days, and the design strength must reach 100% before they can be lifted and transported.
When lifting and transporting piles, they should be stable and not damaged. The lifting points should comply with the design requirements, and pads should be added between the wire ropes and the piles.
The concrete pile stacking site should be flat and solid, and the pads should be stable and correctly positioned. During rainy season construction, ground drainage should also be done well.
Pay attention to the repair and maintenance of transportation roads to ensure smooth driving of transportation vehicles. It is not suitable to transport piles when the roads are slippery in rain or snow.
The entire process from the horizontal position of the pile to being erected on the pile frame should be carried out smoothly to prevent collisions, twists, quick starts, and emergency stops.
For foundation pit excavation after pile driving, reasonable technical measures should be formulated to prevent pile displacement and tilt.
Notes
Quality issues that should be paid attention to
Before the pile leaves the factory, the cross-sectional size and length of the pile should be marked on the pile with a color that is not easy to wear off. , number, production date; if there is no lifting ring, the location of the lifting point should be marked.
When pile driving encounters the following situations, pile driving should be suspended and timely discussion and handling should be conducted with relevant units:
(1) Drastic changes in penetration.
(2) The pile body suddenly tilts, shifts or has severe rebound.
(3) The pile body is seriously cracked or broken.
When static pressure piles encounter the following situations, pile pressing should be suspended and timely discussion and handling should be carried out with relevant units:
(1) During the initial pressure, the pile body moves to a large extent Position, tilt.
(2) During the pressing process, the pile body suddenly sinks or tilts.
(3) The concrete on the top of the pile is damaged or the pile pressure resistance changes drastically.
Safety issues that should be paid attention to
When there are existing buildings or structures nearby, isolation trenches, isolation sheet piles and sand well drainage should be taken before piling. Measures should be taken, and pre-drilling soil should be used for piling.
When piling on soft soil foundation or near existing buildings, corresponding technical safety measures should be taken to ensure safe production and building safety.
When piling under the pit, a dedicated person should be assigned to check the stability of the slope, and calculate the stability of the pile driver based on the condition of the piling equipment to ensure safe production.
Check whether the pile hammer is hung correctly and securely at any time.
When the pile driver is moved, the frame is inspected midway, or piling operations are suspended for other reasons, the pile hammer should be lowered or temporarily fixed. Elevated workbenches, escalators, etc. should have protective railings.
When transporting and storing the raw materials and finished products of sulfur cement, attention should be paid to fire prevention, and care should be taken to avoid burns when cooking. If there is windy weather when connecting piles, wind protection measures should be taken.
Onsite personnel must wear safety helmets, and mechanical and electrical operators must wear insulating shoes and insulating gloves.
Construction is generally not suitable at night, and construction is not allowed in strong winds above level 6.
Quality records
Measurement and setting records.
Certificates of raw materials such as sand, stone, cement, steel, and welding rods, factory inspection reports, and on-site re-inspection reports.
Test report on mechanical properties of steel joints.
Quality acceptance record of steel bar processing inspection batch.
Inspection and acceptance records of concealed steel works.
Quality acceptance record of the inspection batch of concrete precast piles (reinforced skeleton) projects.
Concrete mix proportion notice.
Quality acceptance records of concrete raw materials and mix design inspection batches.
Concrete construction inspection batch quality acceptance record.
Concrete specimen strength test report.
Concrete precast pile inspection batch quality acceptance record.
Test pile records.
Piling records.
Complete plan of pile location.
6.0.15 Quality acceptance record of static pile pressing project inspection batch.
6.0.16 Foundation bearing capacity test report.
6.0.17 Quality acceptance record of reinforced concrete precast pile sub-projects.
6.0.18 Other technical documents.
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