The construction methods of bored piles include rotary drill (positive circulation method, reverse circulation method), percussion drill, punch drill, submersible electric drill, as well as rotary drill, long auger, etc.

   (1) Rotary drill. Use mud to carry broken drill slag. The positive circulation method is that the mud is sprayed from the drill bit into the borehole through the center of the drill pipe, and the mud entrains the drilling slag to rise and discharge into the sedimentation tank; the reverse circulation method is the opposite. Not suitable for pebble layers and hard rock layers.

   (2) Impact drill. Use a hoist to lift the drill bit, impact to form a hole. Use a slag bucket to pick up the drill slag and clear the hole. Simple process. low efficiency. Especially suitable for pebble layers and hard rock layers. Poor hole quality (reaming, drilling rig shift, stuck bit, dropped bit).

   (3) Rotary drilling. New type of pile hole construction method. The principle: use the rotation of the drill pipe and the drill bucket to fill the bucket with soil debris and lift the drill bucket to unearth; through the rotation of the drill bucket, excavation and lifting, soil unloading and mud replacement of the wall. Repeated cycles to form holes. Features: Built-in power, high cost, efficiency can be increased by 20 times, good construction quality, less dust and mud pollution, suitable for various geological conditions, can realize automatic adjustment of mast verticality and measurement of drilling depth.

   (4) Long auger pouring into pile technology underwater. Construction principle: Use a long auger to drill the hole to the design elevation, use a concrete pump to press the concrete out of the bottom of the drill bit, press and pour the concrete while lifting the drill bit until a pile is formed, and then use a special vibration device to insert the steel cage into the pile at one time to form steel Concrete piles. Features: Compared with ordinary underwater bored pile construction technology, long auger is poured underwater into pile construction. Since there is no need for mud wall protection, there is no mud skin, no sediment, no mud pollution, and the construction speed is fast. Low cost. The key points of the process: forming the hole, configuring the concrete, pumping the concrete, and implanting the steel cage.

   (5) Post-grouting technology for cast-in-place piles. Construction principle: in a certain period of time after the cast-in-place pile is formed, the cement slurry is injected into the pile end and pile side through the grouting pipe preset on the steel cage in the pile body and the pile end and pile side grouting valve connected to it. The soil (including sediment and mud) is reinforced, thereby increasing the bearing capacity of the single pile and reducing settlement. The grouting pipe can use the steel pipe pipe tested by ultrasonic. Grouting method: pile bottom grouting, pile side grouting, pile bottom and pile side compound grouting. Process points: grouting pipe production, grouting pipe installation and lowering, grouting test, underwater concrete pouring, water pressure test, grouting construction.