The invention discloses a strong
karst area cast-in-place
pile construction method based on a rotary drilling hole forming manner. The cast-in-place
pile construction method is characterized by comprising the steps of: (1) drilling into the surfaces of a
karst layer and a gravel soil layer by adopting a conventional bit; (2) in combination with the basic theory of rock-
soil mechanics, finding out a mathematic relation between an optimized value of inclination of a multi-stage
alloy pilot roller bit and a coefficient of sliding friction between a rock-
soil material and the interface of the bit; (3) after adopting the conventional bit to dill into the surfaces of the
karst layer and the gravel soil layer, changing the conventional bit into the multi-stage
alloy pilot roller bit, firstly drilling at
high pressure and
low speed, and then, after the bit is dilled into the rock for more than 50 cm, drilling at low pressure and high speed until the drilling depth or hole depth satisfies design requirements; (4) optimizing the design of mud
specific weight in stages for preventing
pile holes from collapsing and improving the
bearing capacity of pile foundations; and (5) handling sudden accidents, such as fracture of drilling rods, bit falling, bit burying, fracture of cone palms in holes, accidental falling of cone palms and other small operation tools and the like, in the drilling process by adopting a
drill tool overshot and a falling object salvage skip.