This technology standard is applicable to the immersed cast-in-place pile engineering in industrial and civil buildings.

2 Construction preparation

2. 1 raw material requirements

2. 1. 1 cement: No.32.5 ordinary portland cement or slag portland cement is used.

2. 1.2 sand: medium sand or coarse sand, with silt content not more than 5%.

2. 1.3 pebble: the pebble size is not more than 50mm；; Gravel particle size is not more than 40mm；; The particle size of reinforced piles should not be greater than 30mm, and should not be greater than 1/3 of the minimum clear distance of reinforcement.

2. 1.4 water: tap water or clean water without harmful substances.

2. 1.5 steel bars: varieties and specifications shall be adopted according to the design requirements, with factory certificate and re-inspection report.

2.2 Main machine tools

2.2. 1 Hammer piling equipment is a common hammer piling machine, such as drop hammer, diesel hammer and steam hammer. It consists of pile frame, pile hammer, pile pipe, etc. , 270-370mm in diameter and 8-15m in length; Vibrating pile sinking equipment includes DZ60 or DZ90 vibrating hammer, ZJB25 walking pile frame, winch, pressurizing device, pile pipe, pile tip or precast reinforced concrete, etc. The diameter of the pile tube is 220-370mm, and the length is 10-28m.

2.2.2 supporting machines and equipment: hopper, 1t electric dump truck, forced concrete mixer, steel bar processing machinery, AC welding machine, oxygen cutting device, type 50 loader, etc.

2.3 Operating conditions

2.3. 1 According to the site geological data and design and construction drawings, prepare the feasible construction organization design.

2.3.2 Ground and underground obstacles within the scope of the construction site have been removed or treated. The site has completed the work of three links and one leveling, and the weak site that affects the operation of construction machinery has been properly handled (such as slag laying), and drainage measures have been taken.

2.3.3 Construction water, electricity, roads and temporary facilities are ready.

2.3.4 The survey datum line and leveling datum point have been set up at the site and protected. Before construction, the axis and anchor points have been set out according to the construction drawings, and the pile position has been rechecked.

2.3.5 During the construction of complex soil layer, pore-forming tests should be conducted in advance, and the number is generally not less than 2.

2.3.6 Conduct safety training and technical disclosure for construction personnel before construction.

2.4 Operators

2.4. 1 main operators: rig operators, steel bar workers, concrete workers, welders, surveyors, technicians and electricians.

2.4.2 Rig operators and electricians shall hold relevant certificates, and other types of work shall receive safety technical training and carry out construction technical disclosure.

3 construction technology

3. 1 process

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3.2 Operation process

3.2. 1 When the pile driver is in place, the pile hammer (vibration box) at the pile driving (pile sinking) position should be upright and stable. At the same time, mark the control depth on the pile frame or casing, so as to observe the casing depth during construction.

3.2.2 When using the flap pile tip, the flap at the pile tip should be tied tightly with hemp rope or iron wire, and the gap between the flaps should be tight. When the pile tip is aligned with the center of the pile foundation and the verticality of the high-speed casing is checked, the pile tip is pressed into the pile by hammering and casing weight.

3.2.3 When using precast concrete pile tip, the pile tip should be buried in the center of pile foundation first, and cushion material should be placed at the contact point between the lower end of casing and the pile tip. After the pile driver is in place, lift the casing and aim at the pile tip, so that the casing, the pile tip and the pile hammer are in a vertical line, and press the pile tip into the soil by using the weight of the hammer and the self-weight of the casing.

3.2.4 The pile-forming construction sequence generally starts from the middle and goes to both sides or around. When the center distance between pile groups or piles is less than or equal to 3.5d(d is the pile diameter), the piles should be driven at intervals. Piling can be started only after the concrete of adjacent piles reaches 50% of the design strength.

3.2.5 At the beginning of pipe sinking, tap slowly. When the hammer sinks the pipe, the speed of sinking the pipe can be improved by tightening the wire rope to pressurize or increasing the counterweight. When water or mud may enter the pile pipe, the back cover concrete of about 1.5m should be poured into the pipe in advance.

3.2.6 The final penetration of immersed tube shall be strictly controlled according to the design requirements and pile test. Hammer sinking pipe should measure the penetration of the last two rows of ten blows; Vibrating immersed tube shall measure the last two 2-minute penetrations.

3.2.7 In the process of pipe sinking, if the casing sinks too fast or fails to sink, the reasons shall be analyzed in time and handled. If the pile tip penetrates through the hard soil layer and enters the soft soil layer, the pipe sinking operation should be continued. If the pipe sinking is caused by the pile tip hanging on the boulder or encountering the hard soil layer, the pipe sinking speed should be slowed down (light hammer, low impact or slow vibration), and then the pipe sinking should be normal after crossing the obstacle. If it still can't sink or the immersed pipe is too deep, and the final penetration can't meet the design requirements, check the geological data and study and deal with it together with the construction unit.

3.2.8 For hoisting the reinforcing cage, the long reinforcing cage should be buried after the completion of hole formation, and the short reinforcing cage can be buried when the concrete is poured to the design elevation, and the reinforcing cage should be aligned with the pipe hole. Slowly descend vertically. When the concrete pile top adopts structural connection steel dowel, it must be inserted symmetrically, evenly and vertically along the periphery.

3.2.9 Every time concrete is poured into the casing, if short-hole piles are formed by long casing, it will be filled at one time. If long-hole piles are formed, fill them as much as possible at the first time. The slump of concrete should be 6-8cm, and that of reinforced concrete should be 8- 10cm.

3.2. When 1 0 is poured, the filling coefficient (the ratio between actual poured concrete and theoretical calculation) shall not be less than1. The general soil quality is1.1; The soft soil is 1.2- 1.3. In construction, according to the filling coefficient of different soils, the demand of single pile concrete can be calculated, and the actual pouring quantity of concrete can be checked by the number of times it is folded and poured into the hopper. When the filling coefficient is less than 1, the whole pile should be driven again; For the broken pile and necking pile, it can be driven partially, that is, the super-broken pile or necking pile can be driven more than1m.

3.2. 165438+ When specified in the design, the construction shall be carried out according to the design requirements.

3.2. 12 The height of each extubation shall be limited to accommodate the concrete poured in a bucket at one time, and the concrete shall be poured while being drawn. In any case, the concrete with a height of not less than 2m shall be left in the casing, and different methods of pipe drawing shall be adopted according to different pipe sinking methods. In the process of pipe drawing, there should be a special person to check the concrete falling in the pipe with a hammer or buoy, and it should not be pulled too high at a time.

3.2. The method of13 hammer sinking for pipe drawing is as follows: after concrete is poured into the casing, the pipe drawing speed is uniform, and the general soil layer should not be greater than1m/min; The boundary between soft soil layer and soft soil layer should not be greater than 0.8m/min. The number of blows of single-acting steam hammer for inverted extubation shall not be less than 70 times/minute; Free drop hammer percussion (small drop hammer) shall not be less than 50 times /min. Before the pipe bottom is pulled to the design elevation of the pile top, piling or knocking shall not be interrupted.

3.2. 14 vibration immersed tube drawing method According to the specific conditions of foundation soil, single stroke method or reverse insertion method can be used. Single stroke: suitable for soil layer with small water content. After the concrete is poured into the casing, it is vibrated and pulled out again, and so on until the casing is completely pulled out. In general soil layer, the pulling speed should be 1.2- 1.5m/min, and it should not be greater than 0.8- 1.0m/min in soft soil layer. Inverse interpolation method: suitable for saturated soil layer. After concrete is poured into casing, it should be vibrated before extubation. The height of tube drawing is 0.5- 1, and the depth of reverse insertion is 0.3-0.5m, which should not be more than 2/3 of the length of petal pile tip. Concrete should be added in stages during tube drawing, and the concrete surface in the tube should never be lower than the ground or higher than the groundwater level1-1.5m. The tube drawing speed should be controlled within 0.5m/min. When the pile tip is close to the bearing stratum about 1.5m, it is advisable to insert it backwards several times to enlarge the bottom area of the pile. When crossing the silt interlayer, slow down the speed of pipe drawing properly to reduce the depth of pipe drawing and reverse insertion. Reverse insertion method is easy to mix mud into piles, resulting in mud piles, so it should be used carefully in construction.

3.2. 15 During the construction of bored pile, observe whether there is horizontal displacement and uplift on the pile top and ground at any time, and take measures to deal with it when necessary.

3.2. 16 If it is necessary to pile again after concrete pouring, the pile tip must be reinstalled at the original pile position before the initial setting of the original pile concrete, and the pipe shall be immersed for the second time. After sinking the pipe, concrete should be poured on the natural ground every time, and small irrigation is not allowed. In the process of pipe drawing, the silt on the outer wall and ground of pile pipe should be removed in time. The axes of two immersed tubes must coincide.

4 quality standards

4. 1 Allowable deviation of plane position and verticality of cast-in-place pile

The pile position deviation of bored pile must comply with the provisions in the table below, the elevation of pile top should be at least 0.5m higher than the design elevation, and the quality of hole cleaning at the bottom of pile has different requirements according to different pile forming technologies, which should be implemented according to the requirements in this chapter. There must be 1 test piece for every 50m3 of pouring, and 1 test piece for every pile less than 50m3.

Allowable deviation of plane position and verticality of cast-in-place pile

Serial number hole-forming method allowable deviation of pile diameter (mm) allowable deviation of verticality (%) allowable deviation of pile position (mm)

1-3 pile, single-row pile foundation perpendicular to the centerline direction, strip pile foundation of pile group foundation along the centerline direction and middle pile of pile group foundation.

1 bored pile with mud wall protection D ≤ 1000mm 50 < 1d/6, and not more than 100d/4 and not more than 150.

d > 500mm 50 100+0.0 1H 150+0.0 1H

2. Casing bored pile D ≤1000 mm-20 <170150

d > 500mm 100 150

3 dry bored pile -20 < 1 70 150

4. Artificial excavation concrete retaining wall +50 < 0.5 50 150

Steel casing wall protection +50 < 1 100 200

Remarks: 1, negative allowable deviation of pile diameter refers to individual sections.

2. For piles constructed by hammering method and reverse insertion method, the allowable deviation of pile diameter is not limited by the above table.

3.h is the distance between the ground elevation of the construction site and the design elevation of the pile top, and D is the design pile diameter.

4.2 Quality inspection standard for reinforcing cage of cast-in-place pile (mm)

4.2. 1 Before construction, raw materials such as cement, sand, stone (such as on-site mixing) and steel shall be inspected, and the construction sequence and monitoring means (including instruments and methods) formulated in the construction organization design shall be inspected.

4.2.2 During the construction process, the whole process of hole formation, slag removal, reinforcement cage placement and concrete pouring shall be inspected, and the bearing layer (rock) at the bottom of the hole shall be reinspected for manual digging piles. Rock-socketed piles must have a lithology report of the bearing stratum.

4.2.3 After the construction, the strength of concrete should be checked, and the quality and bearing capacity of piles should be tested.

4.2.4 The quality inspection standard of concrete cast-in-place piles shall meet the requirements in the following table.

Quality inspection standard for reinforcing cage of cast-in-place pile (mm)

Inspection method of allowable deviation or allowable value of project sequence inspection

Master control project 1 main reinforcement spacing 10 steel straightedge quantity

2 steel rule with length 100.

General project 1 sampling inspection is required for steel plate quality inspection design.

2 stirrup spacing plus or minus 20 steel rule.

3 steel straightedge for diameter 10

4.3 Quality inspection standard of concrete cast-in-place pile

Quality inspection standard of concrete cast-in-place pile

Check the allowable deviation or allowable value of the items in the order of the items.

owner

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Item 4. 1No. of pile location: measure the pile casing before foundation pit excavation, and measure the pile center after excavation.

2. Hole depth (mm)+300 holes are not shallow. Measure with a heavy hammer, or measure the length of drill pipe and casing. Rock-socketed piles shall ensure that they enter the rock-socketed depth required by the design.

3. The design requirements of pile quality inspection shall comply with the provisions of Technical Specification for Foundation Pile Inspection.

4 Concrete strength design requires specimen report or core sample sampling for inspection.

5 The bearing capacity design requirements shall conform to the technical specifications for foundation pile detection.

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1 verticality Article 4. 1 Measure casing or drill pipe, or use ultrasonic detection, and hang the ball during dry construction.

2. Pile diameter 4. 1 caliper or ultrasonic detection, steel ruler should be used for dry construction, and manual digging pile does not include lining thickness.

3. The specific gravity of mud (in clay or sand) is 1. 15 ~ 1.20. After cleaning the hole, sample 50 cm away from the bottom of the hole.

4 Mud surface elevation (higher than groundwater level) (m) 0.5 ~ 1.0 Visual inspection

5 Sediment thickness: end bearing pile (mm)

Friction pile (mm) ≤ 50

≤ 150 is measured with a sedimentation meter or a heavy hammer.

6 concrete slump:

Underwater perfusion (mm)

Dry construction (mm) 160 ~ 220

70 ~ 100 slump meter

7 Installation depth of reinforcing cage (mm) 100 steel ruler

8 concrete filling coefficient > 1 Check the actual grouting quantity of each pile.

9 The elevation of pile top (mm) is+30 and -50, and the laitance layer on pile top and inferior pile body shall be deducted.

Vertical pile foundation centerline 1 ~ 2 pile D ≤ 500mm, 70, D >；; 500mm

, 100 guy and ruler quantity inspection.

Single row pile

Side pile of pile group foundation

150 when the pile d of strip foundation along the center line of pile foundation is less than d≤500mm.

D & gt500mm, 150 guy and ruler inspection.

Note: D is the diameter of the pile and H is the length of the pile.

Intermediate pile of pile group foundation

4.4 Control of key control points in special process

Control of key control points in special process

Control measures of key control points of serial number

1 When drilling, control the specific gravity of mud at any time to ensure that the hole does not collapse.

2. Concrete configuration adopts forced mixer to discharge automatically, and indicators such as slump are detected in time.

3 The distance from the bottom of the concrete pouring conduit to the bottom of the hole is 300~500mm, and the bottom of the conduit should always be buried in the concrete.

The soil is 0.8 ~ 1.3m, and the length of the first bottom pipe of the conduit is ≥4m, and continuous casting is carried out.

4.5 Quality records

4.5. 1 cement factory certificate and re-inspection report

4.5.2 Factory certificate of reinforcement and inspection report of raw materials and weldments.

4.5.3 Inspection report of stone and sand and certificate of weldment.

4.5.4 Test record of pile test pressure

4.5.5 Construction Record of Cast-in-place Pile

4.5.6 Concrete trial mix list and notice of mixture ratio issued by the laboratory.

4.5.7 Test Report on 28d Standard-raised Compressive Strength of Concrete Block

Arrangement of pile position

4.5.9 sampling witness records of each working procedure

5 Quality problems that should be paid attention to

Concrete freezes.

In winter construction, when the temperature is lower than 0℃, thermal insulation measures should be taken for concrete pouring into piles, the mixing water should be heated, and the concrete pouring temperature should not be lower than 50℃. The pile top should be covered and insulated to prevent freezing.

Excessive water content

During construction in rainy season, when the water content of sand and gravel increases, the amount of water added in concrete mixture ratio should be adjusted at any time according to the field measured data. At the same time, we should pay attention to the change of groundwater level and decide whether to carry out back sealing waterproofing. Special attention should be paid to the soft soil layer in contact with the backfill soil layer, which will become soft and plastic under the immersion of surface water. In this section, reverse insertion should be carried out to prevent necking.

5.0.3 The initial setting time of concrete is short.

In summer construction, when the temperature is higher than 30℃, concrete should be mixed with retarder. If the concrete is parked for a long time, it should be put back into the mixer and mixed with a certain amount of ingredients according to the water-cement ratio before it can continue to be used.

constriction

When pouring concrete into piles, if necking occurs, the diffusion pressure is not enough; Or because the slump of concrete is too small and the workability is not good, the concrete cannot spread quickly; Or locally contracted and squeezed by the soil around the pile. The main preventive measures are to strictly control the extubation speed; The soft soil tunnel section adopts reverse insertion; When pulling out the pipe, ensure that the concrete surface in the pipe is always more than 0.2m higher than the natural ground; Concrete should be added during reverse insertion, and the slump of concrete should be strictly controlled at 8- 10cm.

Honeycomb and dog hole

The common quality defects in construction, such as honeycomb, dog eye and loose pile head, are mainly due to the fact that concrete is not measured according to the mixture ratio and mixed evenly, or the stone grading is not good, or the slump is too large, or the operation is not carried out according to the requirements of stopping pulling and vibrating when vibrating the immersed tube.

Suspended pile

The main reason for hanging piles in construction is that groundwater seeps into the pile pipe, resulting in soft layer at the bottom of the pile. The general preventive measures are: try not to use the tipping pile tip when constructing in the stratum with water level; Increase the amount of concrete for pile pipe bottom sealing; Check the pile end for cracks or gaps. If there are cracks or gaps, they must be treated before sinking the pipe.

6 finished product protection

6.0. 1 For pile groups with center-to-center distance less than 3.5 times the pile diameter, interval construction should be adopted when the sinking pipe method is used to form holes, so as not to affect the quality of adjacent piles that have been poured with concrete.

6.0.2 In the process of pile cap construction, when the concrete at the top of the pile deviates from the design elevation, it must be chiseled from top to bottom, and it is not allowed to be chiseled horizontally, so as to prevent the pile from being damaged by the impact of horizontal force.

6.0.3 After foundation excavation is completed, reasonable excavation scheme and technical measures shall be formulated to prevent the displacement and inclination of piles.

6.0.4 All tendons left outside the pile head shall be properly protected and shall not be bent or broken at will.

6.0.5 In winter construction, before the concrete at the top of the pile fails to meet the design strength, it should be covered with heat preservation to prevent freezing.

7 Safety, Health and Environmental Management:

7. 1 Hazard sources and control measures in the construction process

Harm and control measures in construction process

No. of hazard source control measures in operation activities

1 Injury site management personnel are strictly prohibited from entering the site, and the sinking casing should be commanded by special personnel.

2 damage to the operating machinery of the pile driver The operator of the pile driver should know the performance and structure of the pile driver before operation and be familiar with the operation and maintenance methods.

3 Installation and disassembly of falling pile frame During aerial work, when installing and disassembling maintenance parts on pile frame, you must fasten your seat belt.

4 When the pile driver gets an electric shock when walking, the obstacles on the ground and cable should be removed first, and insulating gloves should be worn when moving the cable to prevent cable friction and leakage.

5. Concrete mixing and reinforcing cage production. Concrete mixing and reinforcing cage producers should do a comprehensive safety protection.

6 When vibrating immersed tube is extruded, if the tension wire rope is used to pressurize, the clutch should be adjusted at any time according to the sinking degree of the pile tube to prevent the pile frame from being lifted and accidents. It is forbidden to straighten the cushion layer at the pile tip by hand when sinking the pipe with a hammer. Don't lift the hammer or brake prematurely before the pile hammer hits the pipe top.

7 The pile driver should stand firm. When the pile driver topples, in case of strong wind, the pile pipe should be inserted into the ground and embedded to ensure the safety of the pile driver.

8 personnel should wear safety helmets, and all construction personnel should wear safety helmets and carry out safety education.

7.2 Identification and control measures of environmental factors

Environmental factor identification and control measures

Control measures of environmental factors in operation activities

1 The mixing sewage of concrete is discharged from the sedimentation tank, and it is cleaned and diverted.

2 aggregate comes into play, and the garbage is transported out, and the surface of the dusty sandstone is covered.

Construction waste transportation surface covering

Roads should be maintained and watered frequently to prevent dust pollution.

3 Clean up the site construction waste. The construction site should be equipped with qualified sanitation and environmental protection facilities. Construction waste should be classified and piled up in a centralized way. It is strictly forbidden to pile up and throw waste at will.

4 machinery using waste oil when using and maintaining machinery at the construction site, measures should be taken to prevent dripping. It is forbidden to drip oil on the surface, causing land pollution.