Rotary Drilling Rig Hole Construction Technology Points

Technical points of rotary drilling rig hole formation construction:

      Adopting sand-fishing bottom-sealing drilling bucket: When using rotary drilling rigs to drill in the sand layer, the phenomenon of “running out of air” is easy to occur if ordinary drilling buckets are used, so the engineers and technicians actively carry out technological and technical reforms, and finally decide to adopt the sand-fishing bottom-sealing drilling bucket which has a simple operation process and relatively low technological requirements, and set ventilation holes on the drill bit to ensure the flow of mud above and below the drill bit during the lifting process to prevent the vacuum phenomenon during the lifting process. At the same time, ventilation holes were set on the drill head to ensure the flow of mud above and below the drill head during the lifting process and to prevent the vacuum phenomenon during the lifting process. After starting the rotary drilling rig, firstly adopt low speed drilling, and make sure that the wire rope of the main winch bears more than 20% of the sum of the weight of the drilling bucket and the drilling pipe, and make sure to check whether there is any deviation of the hole position in the drilling process.

Strictly control the specific gravity of mud: in the process of rotary drilling, strictly control the specific gravity of clay and mud between 1.4-1.6. After the strict construction quality inspection of the final hole, the first hole clearing operation should be carried out in time. In the process of hole cleaning, the relevant technology and technical indexes of the mud must be strictly controlled, and the phenomenon of hole collapse should be prevented. Therefore, the specific gravity of mud should be strictly controlled between 1.20-1.30 during the first hole cleaning operation. For some of the mud with low PH value, an appropriate amount of soda ash can be added, and the conventional amount of bentonite can be 0.3%-0.5%, which can raise the PH value to 8-10, in order to accelerate the hydration effect of the sand layer, and further improve the stability and colloid rate of the mud.

Timely organize the second clearing of the hole or remake the mud, so as to achieve the effect of strengthening the stability of the retaining wall: after completing the installation of the reinforcing cage, the technical department should use professional instruments to measure the depth of the hole and the mud performance. Through the experience summarized in this sand layer bored pile construction, the following feasible technical measures are summarized: ① Before concrete filling, the specific gravity of mud in the hole is controlled between 1.15-1.25 which is most reasonable;

② The sand content of the mud should be controlled at ≤10%;

③ The mixing time of the slurry should be ≥10min;

④ The newly mixed slurry should be hydrated and decomposed in the slurry pool for more than 24h before use;

⑤ During the process of concrete filling, the change of water level in the sheath must be strictly observed and recorded, and any accidents need to be dealt with in time.

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