Views: 0 Author: WU Publish Time: 2024-11-18 Origin: Site
The long spiral concrete press-filled pile is a new type of pile foundation construction technology that utilizes the long spiral drilling rig to drill holes to the design depth without lifting the drill, connects the hose at the top of the drilling rod with the outlet of the concrete pump, and then pumps the concrete into the drilling rod through the concrete pump through the hose to press-fill the pile from the bottom of the pile upward, and puts in the reinforcement cage after the completion of the pumping.
The long spiral pressure-irrigation piles have the characteristics of no mud wall protection, no slag at the bottom of the pile, and less pile breakage, etc. Therefore, the results of the long spiral drilling and pressure-irrigation piles' field load test are of representative significance for the understanding of the characteristics of the pile load bearing capacity and the law of the pile side resistance of the pile foundation.
Quality Advantages
(1) Long spiral drilling and pressing pile adopts long spiral drilling rig to drill holes to the designed depth, slowly lifting the drilling and filling concrete at the same time, and after reaching the ground elevation, it will be immediately vibrated into a pile under the reinforcing cage, so that both the hole and the pile can be completed by one machine at one time, with a short construction time and fast efficacy.
(2) Strong adaptability: The pile type is suitable for various soil qualities such as sludge soil (commonly known as peat soil), clay soil, powder soil, fill soil, etc. It can be used to form piles under complicated geological conditions such as soft soil with shrinkage, quicksand layer, sand and pebble layer, and abundant groundwater.
(3) Good quality of pile body: unlike other common construction process of grouted piles, as the concrete is pressed into the hole from the center of the drill pipe of long auger drilling rig, the concrete has the characteristics of dense, no pile breakage, no necking, etc., and it has the effect of infiltration and squeezing on the soil around the pile hole.
(4) High bearing capacity of single pile: Because it is continuously pressed and filled with super-fluid concrete to form the wall of the hole, it has the effect of infiltration, crowding and consolidation on the soil around the pile hole, and improves the lateral friction resistance of the soil around the pile, so that the pile foundation has strong bearing capacity, pull-out resistance, horizontal force resistance, small deformation, and good stability.
(5) Less mechanical input: the reinforcement cage can be lifted directly by the drilling rig and vibrated and pressed into the pile, which saves crane shifts and reduces the input of large-scale machinery.
Quality defects and control
(1) Conduit clogging: due to the concrete proportion or the degree of collapse does not meet the requirements, the conduit is too bent or the front and back of the platform is not close enough.
Control measures
(1) Ensure that the particle size of coarse aggregate, concrete ratio and caving degree meet the requirements.
② Filling pipe to avoid too large a change in diameter and bending, every time you dismantle the conduit must be cleaned.
③ Strengthen the construction management to ensure that the front and backstage work closely together to find and solve problems in time.
(2) Offset piles: generally there are two kinds of pile translation deviation and verticality exceeding deviation. Mostly due to the site reasons, the pile machine is not carefully aligned, and the stratum reasons make the drilling hole to the drilling rod deviation and other reasons.
Control measures:
① remove underground obstacles before construction, leveling and compaction of the site in order to prevent the drilling rig deflection;
②Lay out the pile position carefully and strictly control the error.
③ The level and verticality of the pile rig should be checked and double-checked before drilling and during the drilling process.
(3) Broken piles, interlayer: due to the drilling too fast pumping concrete can not keep up with the drilling speed or neighboring piles are too close to the string hole caused.
①Keep the continuity of concrete filling, you can take measures such as increasing the volume of concrete pump and equipping the storage tank.
② Strictly control the speed of lifting to ensure that there is more than 0.1m3 concrete in the center drilling rod. If the filling stagnation time is greater than the initial setting time of concrete due to accidental reasons during the filling process, the pile should be re-formed and filled.
(4) Insufficient strength of pile concrete: Pressure filling pile is subject to the technical requirements of pumped concrete and post insertion of reinforcing bars, and the degree of collapse is generally not less than 18~22cm, so it is required to have good compatibility. Generally, fly ash is added in the proportion, so that the strength of concrete is low in the early stage, coupled with the small particle size of coarse aggregate, if no attention is paid to the control of water consumption, it is still easy to cause low strength of concrete.
① Optimize the coarse aggregate grading. Large caving degree concrete is generally used 0.5 ~ 1.5cm crushed stone, according to the pile diameter and length of reinforcement and groundwater can be added to part of the 2 ~ 4cm crushed stone, and try not to increase the sand rate!
② Reasonable choice of admixtures. Try to use early-strength water reducing agent instead of ordinary pumping agent.
③ The selection of fly ash should go through the proportioning test to determine the admixture, and the fly ash should be selected at least class II ash.
(5) Pile concrete shrinkage: pile shrinkage is a common phenomenon, generally solved by additives and overfilling, construction to ensure that the filling factor > 1.0.
① The top of the pile is overfilled by at least 1.0m, and to prevent the mud from mixing in the hole, it should be equipped with personnel to clean up in time. ② Select water reducing agent with good water reducing effect.
(6) Pile head quality problems: mostly mud entrapment, air bubbles, insufficient concrete, too thick floating slurry, etc., generally due to improper operation control.
①Remove or transport the soil out of the pile mouth in time to prevent it from being mixed into the concrete when going down the cage, this measure is especially important.
②Keep the air valve at the top of the drill pipe open freely to prevent air accumulation in the concrete, resulting in air bubbles in the concrete at the top of the pile.
③ Floating slurry on the top of the pile is mostly caused by water in the hole or segregation of concrete, and the final hole can be formed only after overfilling and removing the floating slurry.
④ Vibrate according to the specified requirements and ensure the quality of vibration.
(7) Sinking of reinforcing cage: Generally, it occurs with the contraction of concrete, and sometimes it is caused by improper fixing measures of reinforcing cage at the top of pile.
① Avoid concrete contraction thus preventing cage sinking.
②The top of cage must be fixed with wire plus bracket, and can be removed only after 12 hours.
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