Use the drilling machine to drill the whole section of the wellbore once, or drill the wellbore into several holes. The main process is drilling of the wellbore, mud washing wall, sinking prefabricated well wall and wall grouting cementing.
First, the drilling of the wellbore
Drilling in the wellbore is a key process, and the drilling method is mostly done by splitting and reaming.
In order to ensure the verticality of the wellbore, decompression drilling is generally used. That is, the drill itself is pressed against the working surface by 30%-60% of the weight in the mud, so that the cutter can break the rock when the drill bit rotates.
Second, the mud washing well retaining wall
Another important role of mud is to protect the wall. On the one hand, the pressure is balanced by the liquid column pressure of the mud; on the other hand, the mud is formed on the well to block the crack and prevent the sheet. It is required that the mud has good stability and is not easy to precipitate; the water loss is relatively small, and it can form a thin and tough mud; the viscosity of the mud should have better fluidity and easy purification under the condition of meeting the slagging requirements.
The slurry flows from top to bottom along the wellbore and rises to the ground along the drill pipe after washing the well. This well washing method is called reverse circulation washing.
3. Sinking and backfilling
The wellbore constructed by the drilling method uses a tubular prefabricated reinforced concrete shaft wall for the well wall. The prefabricated well wall with the bottom is suspended in the mud in the well by a large hook, and the weight of the water in the well wall is slowly sinked by its own weight and injected into the well wall, and the measurement should be taken when connecting the long well wall to ensure the verticality of the wellbore. While the prefabricated well wall sinks, the mud should be removed in time to avoid mud spillage and sedimentation. In order to prevent the chip, the mud surface should not be lower than 1.0m below the lock.
When the well wall sinks to a depth of 1-2m from the design depth, it should stop sinking. Measure the verticality of the shaft wall and adjust it, then sink it to the bottom and fill the wall in time. Finally, the water in the well wall is drained, and the wall grouting is carried out through the pre-buried grouting pipe to improve the quality of the backfilling of the wall and prevent the occurrence of water and sand accidents when the bottom is broken.
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