Rotary drilling hole forming method by using multi-stage alloy pilot roller bit in complex stratum cast-in-place pile construction

Abstract

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.

Description

technical field [0001] The invention relates to the technical field of geotechnical engineering construction, in particular to a hole-forming method using multi-stage alloy advanced cone bit rotary drilling for the construction of cast-in-place piles in complex strata. Background technique [0002] In the construction method of cast-in-situ piles in complex strata, different hole-forming techniques have different applicable conditions, and there are also great differences in project investment, project quality, and project progress. The manual digging method has high requirements on the pile diameter, groundwater and formation characteristics, and has high safety risks; when the percussion drilled hole has large fluctuations in the bedrock surface, steep rock formations, and large inclination angles, the pile hole is very easy. Deviation and difficult to correct deviation, often repeated deviation; rotary drilling hole using conventional alloy bit or roller cone bit to drill...

AI Technical Summary

Problems solved by technology

These measures not only delay the construction period, but also have adverse effects on contract performance and project cost control.

Especially in karst-developed areas, due to the different karst states, the position, depth, shape and size of caves, karst trenches, and troughs are erratic, which brings more and greater difficulties to the construction, especially in the case of "gourd string". "-shaped karst caves and fissures, the above conventional methods are basically unable to ensure that the rock-socketed meets the design requirements, resulting in many quality problems

Images