First of all, the rotary drilling rig with a kelly bar should meet the design of pile length and empty drill (ground elevation - pile bottom elevation) depth. Secondly, the main machine's maximum hole forming diameter, torque, main pulling force and other parameters meet the design of pile diameter hole forming requirements. Finally, the rock and soil strength need to be shear broken under pressure. A larger machine mass and a reasonable center of gravity can provide the downforce, as well as the fitting lock rod to ensure the pressure output and meet the efficiency of hole formation and construction.
Rotary Drilling Rig Model selection factors
(1) Pile length: the length and diameter of drill pipe are different for different models, which can meet the construction requirements according to the specifications of drill pipe that can be suspended by the main engine.
(2) Pile diameter: small pile diameter conventional geological construction can choose small models, flexible, fuel economy, can improve earnings.
With the increase of pile diameter, more torque, axial pressure and main roll-up force are required, and the machine will be enlarged accordingly.
(3) Geology: with the increase of rock and soil strength, it is necessary to apply more pressure shear breakage, so in order to meet the demand of pile diameter and pile length, the machine type needs to be further increased. There is a trade-off between rock and soil strength and pile depth, whether to choose a larger model or choose to install friction drill pipe.
(4) Economy: consider assembly and disassembly, transportation transfer, maintenance, flexibility, fuel economy, personnel wages, etc. According to the reasonable matching of geotechnical and engineering parameters, the construction costs of different models are quite different.
(5) Special foundation: for construction of special foundation such as occlusion and inclined pile, use protective cylinder driver to lower the casing, and select models according to the diameter and depth of the casing; If the drum driver cannot meet the casing running requirements, a pipe rolling machine/full rotary rig can be installed, but pay attention to the machine interface, operating radius, lifting height and other factors.