1. Pile position stakeout

After the site leveling, organize qualified measurement stakeout personnel, release all pile positions, nail the cross protection piles, make a measurement review, and record the stakeout data for record.

2, buried casing

Use the wire drawing method to check the pile position deviation, and the pile position deviation should meet the requirements of the specification.

3, into the hole

The hole is formed by positive circulation rotary drilling technology, drilled with a drill bit, and according to different levels of soil structure, different turntable speed and footage are selected for control. After drilling in the sand layer and entering the layer of strong weathered granite, the soil layer is too hard, which will cause the tapping of the drill cone and the deflection of the drill cone, and increase the swing of the drill pipe. Therefore, the low-speed slow speed and high-quality mud pumping method are selected. The rotational speed parameter of the turntable takes 13~40v/min, and the hole depth is controlled according to the design requirements. The design requirement is that the pile hole enters the strong weathered granite layer by 5m.

4, mud wall

During the drilling process, according to different conditions of the stratum, maintain a certain hydrostatic head pressure, guide the mud management work according to the principle of balanced drilling, and use the formation clay to make natural pulp as much as possible. When the consistency of the mud cannot meet the requirements, the clay with strong pulping ability and high viscosity should be selected for pulping to increase the consistency of the mud and ensure that the drilling process does not collapse or shrink. The pile hole construction adopts one-time comprehensive uninterrupted operation. During the construction, the soil layer structure is judged according to the slag discharge condition, and the mud performance index is adjusted in a timely and reasonable manner. When the loose formation is encountered, the relative density and viscosity of the mud are appropriately increased, the height of the water head in the hole is maintained, and the height is minimized. The effect of the flushing on the hole wall, while reducing the speed and the drilling pressure to meet the construction quality control requirements.

5, accident prevention measures in the hole

1 Select a construction team with experience and strong sense of responsibility to ensure the quality of the operators;

2 Strengthen the inspection of drilling tools, and strictly prohibit the use of drills with poor processing;

3 The height of the head in the hole, the relative density and viscosity of the mud are often observed and detected, and the problem is solved in time, especially when drilling the slag, lifting the cone to remove the soil or stopping the drill for the reason, the hole should have the specified water level and requirements. Mud performance indicators to prevent boring;

4 Drilling operations should be carried out in batches, paying attention to changes in soil layers, taking slag samples at soil layer changes, identifying soil layers, and then checking with geological sections, and taking corresponding measures according to soil conditions to ensure construction quality;

5 The lifting taper should be stable. The drill cone should prevent the collision of the wellhead from colliding with the casing and the hole wall, and prevent the bottom of the casing from being hooked.

Clear hole

Clearing the hole is an important part of the construction of the hole pile and ensuring the quality of the pile. The quality index of the pile hole, the thickness of the sediment at the bottom of the hole, the amount of drilling slag contained in the circulating liquid and the mud wall of the hole wall are ensured by the clear hole to meet the quality requirements of the pile hole. This time, the positive circulation rotary drilling technology is adopted. The method of clearing the hole is to increase the drilling tool by 20~50cm after the final hole of the pile hole, and use the large pump to pump the new mud whose performance index meets the requirements and maintain the positive cycle for more than 30min until it is removed. The bottom of the hole is sedimented and the mud wall of the hole wall and the mud content of the mud are less than 4%. Because of the thick loose and easy soil layer, the pile hole of the project can not immediately terminate the hole after clearing the hole, but the steel cage is placed in the hole, and the second hole cleaning operation is performed after the grouting pipe is installed, so that the bottom of the hole before the infusion The thickness of the sediment meets the requirements to ensure the quality of the column.

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