3.
The inner diameter of the pile casing should be 20-40mm larger than the pile diameter.
The reinforcement cage is formed by spot welding in the prefabrication formwork to ensure that the main reinforcement is straight, the error is small, the stirrup is round and the visual effect is good.
Lifting the drill pipe up and down during hole cleaning is conducive to smashing the larger mud blocks, so that the smaller mud blocks will flood out from the orifice with the mud.
(1) The pile casing is made of rolled steel plate.
In order to ensure the elevation of the reinforcement cage, the surveyor shall measure the plane elevation of the drilling rig, and the constructor shall measure the length of the welded hanging reinforcement..
Hole forming construction – drilling control parameters hole forming construction – hole forming mud control parameters hole forming construction – hole forming quality standard 4 The key requirements of this process are as follows: the key of hole cleaning is one-step cleaning.
If all indexes of the mud in the hole do not meet the design and specification requirements, the hole shall be cleaned again until it is qualified.
The drilling rig body must be firm to ensure no displacement and inclination during construction.
The center of the pile casing coincides with the center of the pile position.
The function of pile casing embedding is to protect the orifice and isolate the loose materials in the upper part.
If the error is greater than the specification requirements, it shall be buried again.
The reinforcement cage without acceptance shall not be lowered.
Press the slurry through the concrete conduit for the second hole cleaning, in order to remove the sediment generated during the placement of reinforcement cage and concrete conduit.
When drilling, it is necessary to drill at low pressure and low speed to ensure the verticality of the hole.
(4) Mud density control in drilling: generally, in loose and collapsible strata (such as silt and silt soil layer), the mud density is controlled at about 1.30, and in cohesive soil layer (such as silty clay), the mud density is controlled at about 1.25.
Therefore, the pile casing must be buried before the construction of each pile.
Reinforcement cage placement the key points of this process are: the reinforcement cage shall not be forcibly removed from the cage.
The key points of this process are: the reinforcement with quality assurance certificate and passing the sampling re inspection shall be selected.
III Key points of process control 1 Measurement and positioning (1) according to the measurement datum point and baseline provided by the owner, it can be used as the measurement base point after rechecking and confirming with relevant units, and it shall be rechecked frequently.
When removing the cage, it shall be rotated and lowered slowly.
Before placement, it shall be accepted together with the supervisor, and the acceptance certificate of concealed works shall be carried out on the spot.
After the drilling rig is in place, the level of the base shall be adjusted in time.
The pile casing should be buried vertically and backfilled with clay around.
(5) During the hole forming process, the circulating ditch of the mud pit shall be dredged frequently, and the mud pit shall be cleaned regularly, and the waste slurry shall be transported out in time.
One-step cleaning should be carried out when drilling to 1 ~ 2 meters from the bottom of the pile foundation design.
Pay close attention to the stability of the pile frame during drilling.
The reinforcement cage is made in several sections, which must be self inspected by the reinforcement team leader.
The key points of this process are: this process is the most critical process in the whole construction of bored cast-in-place pile.
2.
(3) Before embedding the pile casing, carefully probe whether there are obstacles (old house foundation, etc.) underground to avoid affecting the normal construction due to underground obstacles during formal drilling construction.
The reinforcement cage shall be made by full-time reinforcement worker and certified electric welder, and the overlapping welding quality of reinforcement shall be sampled and submitted for inspection.
Therefore, the successful completion of one-step cleaning can better ensure that the sedimentation at the bottom meets the design requirements.
The sampling quantity is one group of tests for every 300 welded joints.
(3) The drilling is fast or slow in drilling, and the performance and index of wall protection mud shall change according to the soil condition of the actual stratum.
(2) After the pile casing is buried, the pile position shall be rechecked in time.
In order to ensure that the main reinforcement of the reinforcement cage does not appear, the project adopts 4 Φ one hundred × 50 concrete blocks are set on the reinforcement cage, one group every 3 meters, symmetrically.
For general soil layer (mainly clay layer), grade II (70 RPM) shall be used to appropriately reduce the WOB and speed up the drilling speed; Under special circumstances (mainly referring to sand layer soil), gear I (40 RPM) shall be used to appropriately increase the WOB and slow down the drilling speed.
Taking a bearing platform as an example, if only one drilling rig is set for each bearing platform, the sequence of pile drilling is: ① → ⑤ → ③ → ⑦ → ② → ⑥ → ④ → ⑧.
Pay attention to the vertical and central lowering to avoid colliding with the soil wall; The hanging reinforcement shall be firm to prevent the reinforcement cage from falling; The length of hanging reinforcement shall be calculated according to the measured elevation to ensure that the elevation of cage top is correct.
(1) First hole cleaning: immediately after the completion of hole forming, use the drill pipe for the first hole cleaning, in order to remove the sediment generated during hole forming.
(1) Confirm the drill bit diameter according to the test pile conditions and design requirements.
Full load operation must be carried out before spud in.
The pulley on the upper part of the frame, the center of the rotary table and the pile position shall be in the same straight line.
The key requirements of this process are: the buried depth of the pile casing is determined according to the soil quality; Backfilling must be carried out symmetrically to avoid displacement of pile casing; Ensure that the pile position is free of underground obstacles.
It is not only a necessary measure to prevent the collapse of the orifice, but also a reference point for controlling positioning and elevation control.
Spare various mud testing tools.
(2) Second hole cleaning: after the first hole cleaning, raise the drill pipe, measure the hole depth, and place the reinforcement cage and concrete conduit as soon as possible.
6.
(4) After the secondary hole cleaning, a specially assigned person shall measure the hole depth and sediment at the bottom of the hole.
(2) According to different geological characteristics, reasonably control the drilling parameters (ROP, WOB and drilling speed requirements).
I Construction process and control points i Construction process II Construction sequence engineering pile drilling sequence drilling sequence must adopt skip drilling mode to avoid the impact of hole string and drilling vibration on the newly poured pile concrete.
5.
(3) After hole cleaning, the mud density in the hole is 1.10 ~ 1.15, the viscosity is 20 ~ 26S, the sand content is ≤ 3%, and the sediment at the bottom of the hole is ≤ 100mm.
(2) The pile position shall be corrected and rechecked for three times, that is, the center of the pile position shall be set out for the first time, and the excavation position of the pile casing pit shall be determined by the cross method; Measure and correct the position of the pile casing for the second time, drive in the positioning reinforcement and submit it for review; During the third drilling positioning, the plumb is used to correct so that the center of the rotary table coincides with the center of the pile position.
