1 construction technology of bored pile, measuring the position of pay-off pile
2, liners buried, pile position measurement.
3. Displacement of drilling rig
4, drilling rig spudding
5, drilling
6, the final hole, the final hole detection hole depth
7, hole cleaning, reinforcing cage
8, secondary hole cleaning, detection of mud specific gravity, viscosity, sand content, indicators qualified after ready to pour concrete.
9, pile head excavation, chisel pile head
10, pile foundation detection, detection methods include low strain, high strain, ultrasonic detection, drilling and coring, etc. According to the design requirements.
Construction technology of impact bored pile The construction technology of impact bored pile is as follows:
1. Before spudding, pour mud into the hole, and the relative density of mud depends on the soil layer. If there is water in the hole, clay can be directly put in and the mud can be repeatedly impacted with a small stroke of an impact cone. Generally, the fine-grained soil layer can be compacted repeatedly with thick mud, short stroke and high frequency, so that the hole wall is solid and does not collapse or leak. Normal impact can only be carried out after the drilling depth exceeds the full height and full stroke of the drill bit. In the drilling stage of 4 ~ 5m, in order to make the drilling slag squeeze into the hole wall and reduce the number of slag cleaning, the slag should be cleaned in time after normal drilling to ensure the effective impact on the hole bottom.
2, in the process of drilling, should pay attention to the formation changes, according to different soil layers, using different drilling speed.
3. Stroke should be specified according to soil conditions: generally, large stroke is adopted in hard and dense pebble layer or bedrock boulder layer; When passing through loose sandy soil, gravel soil or pebbles sandwiched in soil layer, the medium stroke is adopted, which is too large, causing great vibration to the bottom of the hole and easily causing hole collapse; When passing through high liquid limit clay and sand-bearing low liquid limit clay, medium stroke is adopted; Use small strokes in places prone to collapse or quicksand to increase the viscosity and relative density of mud.
4. When passing through boulders or rock strata, if the surface is uneven, clay, pebbles and pebbles should be put in first to make the surface smooth, and then impact drilling with a drill bit to prevent accidents of inclined holes and hole collapse; If the strength of rock stratum is uneven and it is easy to cause hole deviation, the above method can also be used to backfill and re-drill; If necessary, inject cement into the retaining wall or extend the buried depth of the liner.
5. When drilling loose layers such as sand and pebble soil, clay and small stones (particle size is not more than 375px) can be put in the proportion of 1: 1, and the impact cone is used to repeatedly impact with a small stroke, so that the mud paste and small stones can be squeezed into the hole wall. When necessary, backfill and impact repeatedly for 2 ~ 3 times. In case of quicksand, clay should be increased, and the flaky proportion should be reduced, and the hole wall should be solid.
6. When passing through the viscous soil layer such as sandy clay with low liquid limit, the consistency of the input mud should be reduced because the soil layer itself can make slurry, and a short stroke of 0.5m should be adopted to prevent the drill from sticking and burying.
7, pay attention to the length of the wire rope should be uniform. Generally, the rope can be loosened 125px ~ 200px in soft soil layer and 3 ~ 125px in dense hard soil layer. Attention should be paid to prevent too few loose ropes from forming a "hollow hammer", resulting in excessive accidental load and damage to drilling rig, derrick and wire rope. If the rope is loosened too much, the stroke will be reduced, the drilling speed will be reduced, and the wire rope will be wound in serious cases.
What is the construction technology of bored pile? Drilling rig structure
(1) Burying and slurry making:
This project adopts steel liners matching the diameter of pile foundation; The gasket shall be buried within 4m. The center line of the buried pile casing must coincide with the center line of the pile, the allowable deviation of the plane is 50mm, and the inclination angle of the vertical line must be less than 65438 0%. The connection with the casing requires no protrusion in the casing, tensile and pressure resistance, and no water leakage.
Drilling mud is made of water and clay, and its relative density is 1.2- 1.4. If the preparation of clay can't meet the required indexes of mud, bentonite or other additives can be used.
(2) Rig in place:
Rig installation must be carried out according to the control points of pile foundation provided by on-site construction technicians. Rig installation must be firm and stable, and the functions of all components should be flexible and reliable (the site within the scope of pile foundation construction is flat and the activity space is barrier-free). Prevent the rig from shifting and sinking during drilling.
(3) pore formation:
The drilling operation will be carried out in shifts for 24 hours, and the machinery will be supervised by professionals. The drilling situation of the drilling rig and the proportion of mud will be supervised by special personnel, and even adjusted. During the drilling process, the drilling construction record will be filled in. During the handover of each shift, the drilling situation and matters needing attention of the next shift should be explained.
Slow down when starting the machine, and speed up drilling only after all guiding parts enter the stratum. During drilling, check the level of drilling rig and the verticality of drill pipe at any time to ensure the verticality of drilling < 1%. Pay attention to geological changes at any time during drilling. If it does not conform to the geological conditions, it should report to the technical supervisor in time and make analysis and comparison. When necessary, exploration departments and designers should be invited to consult and analyze, and put forward conclusions.
In order to ensure the engineering quality and prevent the hole wall from collapsing, firstly, the qualified mud is poured into the casing, and the mud density is measured and controlled at any time during the hole forming process. The mud specific gravity is controlled according to different geological conditions: cohesive soil:1.02 ~1.06; Sandy soil:1.06 ~1.10; Gravel soil:1.10 ~1.15.
During drilling, the drilling speed should be uniform, and sudden acceleration is not allowed. Drilling operation should be completed at one time, and the pause time should not be too long.
(4) Stop drilling:
In the process of drilling, when the designed pile length is reached, the drilling shall be stopped in time with the consent of the quality inspector and the supervision department.
(5) hole cleaning:
After the completion of the final hole, hang a 0.5kg weight iron weight under the measuring rope to measure and check the hole depth, and then clean the hole after verification; Care must be taken to maintain the specific gravity of mud in the hole to prevent collapse, and the method of deepening the depth of the hole bottom should not be used instead of cleaning the hole. After hole cleaning, the sediment at the bottom of the hole shall not be greater than 5cm, the over-diameter coefficient of hole formation shall not be greater than 1. 1 and shall not be less than 1.0, the verticality of the hole shall be less than 1%, and the sediment at the bottom of the hole shall be less than 5 cm.
After lowering the pile foundation reinforcement cage and conduit, measure the thickness of sediment again, and carry out secondary hole cleaning until the sediment is less than 5cm and the mud density is between 1. 1- 1.2, and then stop hole cleaning. Concrete pouring must be carried out within 30 minutes after hole cleaning.
(6) Put down the reinforcing cage
After the first hole cleaning, lower the reinforcing cage. The reinforcing cage will be moved and installed by crane. When hoisting, three-point hoisting will be adopted, and pine rods will be tied inside the cage to prevent deformation, so as to ensure that the cage body is uniformly stressed and not deformed. When installing, slowly put it into the middle hole to prevent it from colliding with the hole wall. It is forbidden to lift it high and slam it.
After the reinforcing cage is in place, check the lower entrance position according to the design requirements. After the design position is determined, the reinforcing cage shall be fixed in time, and the reinforcement shall be fixed in a solid foundation position through intubation to ensure that the reinforcing cage will not shift, float or sink during concrete construction.
(7) Underwater concrete pouring:
All commercial concrete is used in this project, and the concrete for pile foundation is poured directly into the hole by concrete mixer, which solves the problem of large amount of concrete in the first plate of cast-in-place pile. Before pouring, the supplier of commercial concrete must provide the certificate of commercial concrete, the certificate of concrete mixture ratio and the certificate of raw material quality, and assign special personnel to do the tower slump test for each tank of concrete on site to ensure that the slump is qualified at 180-220mm. It is planned to use six commercial concrete transport vehicles to ensure the continuity of pile foundation concrete pouring.
The conduit must be sealed with a sealing ring to ensure its air tightness and water tightness. The bucket for pouring concrete must be large enough to ensure that the initial pouring amount of concrete reaches the buried depth of 1.0m or more.
Lower the bottom of the concrete conduit to a distance of 300-500mm from the bottom of the hole, and lower it slowly to prevent it from colliding with the reinforcing cage and affecting the position of the copper reinforcing cage.
In the process of concrete pouring, the rising height of the concrete surface should be detected in time, and the conduit should be dismantled in time to ensure that the bottom conduit is buried below the concrete surface not less than 2.0m, and it is forbidden to pull the conduit out of the concrete surface. The concrete over-pouring quantity of each pile should be controlled above 0.8m
The concrete pouring of each pile must be completed at one time, and it is not allowed to stop halfway.
Do a good job of retaining test blocks, and leave two groups for each pile, one for standard curing and the other for the same condition curing, so as to test the quality of piles.
(8) Pile quality standard:
The hole-forming depth must meet the design requirements.
Allowable deviation of aperture:-50mm.
Vertical deviation: less than 1% pile length.
Pile position deviation: 50 mm
Six, steel structure
(1) Basic requirements:
All steel bars must be inspected for the effectiveness of raw materials before entering the site, and unqualified products are forbidden to enter the site. Check whether the factory certificate and batch number of steel bars are consistent with the incoming materials, and check whether the types of steel bars meet the requirements. Without the consent of the designer, it is forbidden to substitute reinforcement. Stacked steel bars must be pollution-free, corrosion-free and convenient for construction operation, so as to prevent steel bars from being eroded by rain and other factors.
Steel processing site must be flat and clean to prevent deformation, corrosion and pollution of processed steel bars. (The site is hardened with concrete)
Steel bar construction should be carried out by experienced professional team, in strict accordance with the construction operation procedures, and meet the construction specifications and design requirements. All personnel should hold relevant certificates.
Butt welding of steel bars shall be operated by experienced professionals with relevant certificates. When butt welding, the test pieces must be selected first, and a large number of steel bars can be processed only after the performance indicators are qualified. Sampling inspection should be carried out in the construction process to test the construction quality.
Welding and processing of steel bars must meet the specification requirements and design requirements, and steel bars shall not be damaged during construction, which will affect the mechanical efficiency of steel bars.
(2) Pile foundation reinforcement cage:
Each pile foundation reinforcement cage is bound and formed on the ground at one time. According to the design requirements, the whole length of the main reinforcement of the reinforcing cage is welded by flash butt welding, which meets the design requirements. The spiral stirrups outside the cage are connected with the main reinforcement by spot welding, and the rest are bound; The reinforcing ribs are welded with the main reinforcement to form a closed loop, and the closed loop is lap welded. Weld length 12cm, single-sided welding 24cm. The lap length of the main reinforcement of the pile extension is 80cm, and the double-sided welding is adopted, and the weld length is 60cm, which ensures the overall stiffness requirements of the reinforcing cage.
Steel butt welding sampling must comply with the specifications and design requirements.
The processed reinforcing cage must be laid flat to prevent deformation. Before the construction of cast-in-place pile, the tied reinforcing cage must be inspected and accepted in conjunction with relevant departments such as design and supervision, and the acceptance record must be filled in. Unqualified products are strictly prohibited from being used in engineering.
The allowable deviation and protective layer thickness of pile foundation reinforcement cage construction must meet the design requirements and norms. The reinforcement shall be constructed in accordance with the operation procedures.
Seven, pile foundation construction matters needing attention
(1) For the construction lofting of bored piles, the deviation of the center of single pile shall not be greater than 50mm, the thickness of sediment at the pile tip shall not be greater than 100mm, and the aperture shall not be less than the design diameter.
(2) After drilling to the design depth, check the quality of the hole, including the shape (aperture), depth, verticality and sediment at the bottom of the hole.
(3) If the on-site measured indicators such as detection aperture, verticality, hole wall stability and siltation do not meet the specifications and design requirements, the reasons should be found out and remedial measures should be taken in time to improve the construction technology in the future.
(4) In the process of manufacture, installation and transportation, measures should be taken to prevent irreversible deformation. When hoisting into the hole, it is not allowed to collide with the hole wall, and reliable measures should be taken to fix its vertical position when pouring concrete.
(5) After the pile is completed, the quality of the pile should be checked, and the foundation pile should be nondestructive tested one by one.
Eight, after the pile detection
(1) Check in time after drilling and piling.
(2) When testing pile foundation, it must be operated by professionals, and the data should be sorted out in time.
(3) After obtaining the test data, organize the technical personnel of the project department to analyze the data in time, and formulate corresponding rectification measures for the problematic piles with reasons in time. After rectification, the next step of construction can be carried out.
What is the construction technology of bored pile? Construction method of bored pile
The construction of bored pile is divided into two types: mud wall protection method and full pipe construction method.
Construction method of mud wall protection
The construction method of slurry wall protection can adopt impact drilling, impact drilling and rotary drilling. The process of this construction method is as follows: leveling the site → mud preparation → burying the casing → laying the working platform → installing the positioning drill → drilling → cleaning the hole to check the quality of the hole → lowering the reinforcing cage → pouring underwater concrete → pulling out the casing → checking the quality. construction sequence
(1) construction preparation
Construction preparation includes: selection of drilling rig, drilling tools and site layout.
The main equipment for bored pile construction is drilling rig, which can be selected according to geological conditions and the use conditions of various drilling rigs.
(2) Installation and positioning of drilling rig
If the foundation on which the drilling rig is installed is unstable, adverse effects such as inclination of the drilling rig, inclination of the pile and eccentricity of the pile are likely to occur in the construction, so the installation foundation is required to be stable. For the soft and sloping foundation, bulldozers can be used to level it and steel plates or sleepers can be used to reinforce it.
In order to prevent the pile location from being inaccurate, it is very important to determine the center position and install the drilling rig correctly. For a drilling rig with a derrick, firstly, the drill pipe is roughly positioned by using the power of the drilling rig and the nearby ground cage, and then the frame is jacked up for precise positioning, so that the clamping holes of the lifting pulley, the drill bit or the fixed drill pipe are in a vertical line with the center of the casing to ensure the verticality of the drilling rig. The deviation of drilling rig position shall not exceed 2cm. After aligning the pile position, level the beam of the drilling rig with sleepers, and symmetrically pull the cable wind rope on the axis of the drilling rig at the top of the tower.
(3) Buried liner
The key to successful drilling is to prevent the hole wall from collapsing. When the hole is deep, the soil on the hole wall below the groundwater level will collapse into the hole under the action of hydrostatic pressure, and even sand flow will occur. If we can maintain the high head of the groundwater level in the borehole and increase the hydrostatic pressure in the borehole, we can protect the borehole wall and prevent the borehole from collapsing. In addition to this function, the casing also has the functions of isolating surface water, protecting orifice ground, fixing pile hole position and guiding drill bit.
There are three kinds of materials for lining: wood, steel and reinforced concrete. The liners should be durable and impervious, and the inner diameter should be larger than the borehole diameter (about 20cm for rotary drilling rig, 40cm for down-the-hole drilling rig, impact or grab cone), and the length of each section is about 2 ~ 3 m. Steel liners are generally used.
(4) mud preparation
Drilling mud consists of water, clay (bentonite) and additives. It has the functions of suspending drilling slag, cooling the drill bit and lubricating drilling tools, increasing hydrostatic pressure, forming mud skin on the hole wall, isolating seepage inside and outside the hole and preventing hole collapse. The mud consistency of modulated drilling mud and circulating purification mud should be determined according to drilling methods and formation conditions, and the mud consistency should be flexibly mastered according to formation changes or operation requirements. The mud is too thin, the slag discharge ability is small, and the wall protection effect is poor; Too thick mud will weaken the impact of the drill bit and reduce the drilling speed.
cast-in-situ bored pile
(5) Drilling
Drilling is a key process, and the construction must be carried out in strict accordance with the operating requirements to ensure the quality of drilling. First of all, we should pay attention to the quality of opening, so we must aim at the center line and verticality, and we must press the casing well. Pay attention to the continuous addition of mud and slag discharge (impact use) during construction, and check whether the hole is deviated at any time. When impact or grab drilling rig is used for construction, the nearby soil layer will be affected by vibration, thus affecting the stability of adjacent holes. Therefore, the borehole should be cleaned in time, the reinforcing cage should be lowered, and underwater concrete should be poured. The drilling sequence should also be planned in advance to ensure that the construction of the next pile hole will not affect the last pile hole, and the moving distance of the drilling rig will not be too far to interfere with each other.
(6) hole cleaning
The depth, diameter, position and shape of the borehole are directly related to the quality of the pile and the curvature of the pile body. Therefore, in addition to close observation and supervision when drilling, after drilling reaches the design depth, the hole depth, hole position, hole shape and aperture should also be checked. When the final hole inspection completely meets the design requirements, the bottom of the hole should be cleaned immediately to avoid mud precipitation and hole collapse caused by too long interval. For friction piles, when the hole wall is easy to collapse, it is required that the thickness of sediment is not more than 30cm before pouring underwater concrete. When the hole wall is not easy to collapse, it should not exceed 20cm. For column piles, the thickness of sediment should not exceed 5cm before water injection or air injection. The borehole cleaning method can flexibly use different rigs. Usually, a forward rotary drilling rig, a reverse rotary machine, a vacuum suction machine and a slag extractor can be used for hole cleaning. Among them, mud suction machine is used to clean holes, which requires less equipment and is convenient and thorough to operate, but it should be used with caution in unstable soil layers. Its principle is to blow the high-pressure air generated by the compressor into the pipeline of the sludge suction machine and blow out the sludge.
(7) pouring underwater concrete
After hole cleaning, the prefabricated reinforcing cage can be vertically hoisted into the hole, fixed after positioning, and then poured with a catheter. The concrete shall not be interrupted during pouring, otherwise the pile will be easily broken.
Whole pipeline construction method
Construction sequence of whole pipeline construction method. The general construction process is: leveling the site, laying the working platform, installing the drilling rig, pressing the casing, drilling, placing the reinforcing cage, preventing the pipe, pouring concrete, pulling out the casing and checking the quality of the pile.
The main construction steps of the whole pipeline construction method are similar to those of the mud wall protection method, except that mud and hole cleaning are not needed. The verticality of pressed casing depends on the verticality of 5~6m depth at the beginning of excavation. Therefore, the verticality should be checked with a level and a plumb.
Construction technology of post-grouting cast-in-place pile with spiral drilling
4.2 Technical requirements for post-grouting construction of cast-in-place piles
4.2. 1 control parameters of post-grouting construction
(1) The initial operation time of post-grouting can generally be carried out 2 days after the completion of the foundation pile, and the specific time can be adjusted according to the construction situation of the foundation pile, but generally it should not exceed 30 days after the pile is completed (in case of special circumstances, grouting can be carried out in advance); '
(2) The quality control of post-grouting adopts the double control method of grouting quantity and grouting pressure, with the grouting quantity as the main control and the pumping termination pressure as the auxiliary control;
(3) The cement is P.O 32.5 cement, and the grouting water-cement ratio is 0.60 ~ 0.75;
(4) Cement pressure and pumping termination pressure are as follows:
Pile type, pile diameter/effective pile length, grouting at each pile end and grouting at each pile side.
Cement pumping pressure
Grouting pile1000 mm/36.50 m&; 38.00m1600 ~1800kg ≮ 2.0mpa 600 ~ 800kg ≮1.5mpa.
Specific construction control standards:
A. The cement pressure reaches 70% of the design value in the table, and grouting can be stopped when the pumping pressure exceeds 6.0MPa;
B the cement injection amount reaches 70% of the design value in the table, and the pump pressure is less than 70% of the predetermined pressure in the table.
, should lower the water cement ratio, continue grouting to reach the predetermined pressure;
C. If the cement slurry overflows from the pile side, the water cement ratio should be reduced and the cement pressure should be poured intermittently until the cement pressure meets the requirements in the above table.
4.2.2 Post-grouting pipeline setting
(1) The grouting valve at the pile end and pile side shall be made according to the patented product pattern of Foundation Research Institute of China Academy of Building Research. Two grouting pipes are set at the pile end and one grouting pipe is set at the pile side (see the grouting equipment diagram for details).
(2) The grouting conduit shall be a welded pipe for conveying low-pressure fluid in line with national standards. The nominal diameter of the grouting conduit at the pile tip is φ25( 1'), and the wall thickness is 3.25mm (note: the actual wall thickness of the steel pipe shall not be less than 3.25mm); Guide for grouting on pile side. The nominal diameter of the pipe is φ20(3/4') and the wall thickness is 2.75mm；; The nominal diameter of the welding sleeve of the grouting conduit at the pile end is φ32, and the wall thickness is 3.25mm.
(3) The setting of grouting conduit is shown in the detailed drawing, and the key points are as follows (see attached figure):
A, the upper end of a grouting conduit is provided with a pipe thread, a pipe hoop and a plug; G 1' thread and a pipe hoop for tightening the grouting valve at the pile end are arranged at the lower end of the pile end grouting conduit; The lower end of the pile-side grouting conduit is provided with G3/4' thread and a tee for inserting the pile-side grouting valve.
B. Grouting conduit shall be connected by casing welding, and the welding shall be continuous and airtight, and the weld shall be full and uniform, and there shall be no air holes and sand holes (each solder joint shall be knocked off to check the welding quality, and the next working procedure can be carried out only after it meets the requirements).
C grouting conduit and reinforcing cage are fixed by 12 lead wire cross binding method. Binding should be firm, binding point should be uniform. The grouting conduit at the pile end is bound at the inner side of the stiffening hoop, and the binding fixing point is at each stiffening hoop; The grouting conduit at the pile side is bound on the outer side of the spiral stirrup, and the spacing between binding points is1.5m.
D the upper end of the grouting conduit shall be not less than 200mm under the pile construction floor (it can be slightly adjusted according to the specific situation); The lower end of the pile tip grouting conduit is 400mm away from the longitudinal cage bottom of the reinforcing cage. (Note: The bottom hoop of the reinforcing cage should also be adjusted here; The set elevation of the lower end of the grouting conduit at the pile side is about -34.30m, which is 10m away from the cage bottom. )
E, inserting a grouting valve at the side of the pile in the process of hoisting the reinforcing cage into the hole, and welding the grouting conduit at the empty hole section of the pile before the reinforcing cage is finally positioned;
F the reinforcing cage shall not be twisted and collided downwards repeatedly during hoisting; The reinforcing cage must sink to the bottom, and cannot be suspended!
G. After the pile concrete is poured and the vertical holes are backfilled, obvious signs should be inserted, and vehicles are strictly prohibited from rolling.
4.2.3 Post-grouting mechanism
(1) grouting pump adopts 3SNS high-pressure grouting pump with rated pressure not less than 8MPa, rated flow rate of 76L/min and power 18kW.
(2) grouting pump control monitoring pressure gauge is 2.5 16MPa seismic pressure gauge.
(3) The slurry mixer is YJ-340 slurry mixer matched by grouting pump, with a volume of 0.34m3 and a power of 4kW.
(4) High-pressure fluid pumping hose with rated pressure not less than 8MPa shall be used for the cement slurry conveying pipe.
4.2.4 Post-grouting construction materials
The cement used for grouting is marked as P.O 32.5, and the cement shall meet the requirements of relevant technical specifications.
What's the difference between bored pile, sinking pipe pile, mixing pile and blasting pile? Hello! In the aspect of pile-forming technology, the bored pile is drilled with a drilling machine and then poured with concrete; Immersed cast-in-place pile is to drive the steel pipe into the soil, and then pull out the steel pipe while pouring concrete; Explosive expanded pile is also called rammed expanded pile (explosive expanded in rock). After the pile is driven to the specified depth, it is poured with hard concrete, compacted (or exploded) with a rammer to form an enlarged head, and then the upper concrete is poured. These three kinds of piles are all reinforced concrete piles, but the difference is that bored piles are used to remove the soil inside the piles, while driven piles are used to squeeze the soil around the piles. There are two ways to form the explosive belled pile, but the pile head is enlarged, which improves the bearing capacity of the pile. Mixing piles are generally used to reinforce foundation soil. The cement slurry is pressed into the soil by pressure, and the soil and mud are mixed with special machinery while adding it to form a "cement-soil" pile to improve the bearing capacity of the foundation.