The Application Of Rotary Drilling And Reamed Pile Construction In Super-thick Sand Layer

Under the geological condition of super-thick sand, it’s possible for the formation of bored grouting pile to occur hole wall collapse and catheter filled with sand and other phenomena. Taking the construction character of drilling pile as a starting point, the paper studied the influent factors on the pile bearing capacity, improved the key construction technology based on the possible project accident caused by the pile drilling in super-thick sand layer, summarized the construction method of rotary drilling and reamed pile in super-thick sand layer, and finally, took the construction of Nan Ning East Station pile project for an example, verified the advantage of the construction method.The construction method mainly aimed at the pile construction under the geological condition of super-thick sand and constructs through the way of rotary drilling and reamed pile. Due to the poor cohesion of sandy soil, the pile need to keep stable by the friction resistance. When the construction condition is below the underground water level, the friction resistance and shear strength between pile and soil are reduced, the sandy soil stress to the hole after drilling pile hole, make the initial pore diameter decreases, and eventually led to the sand layer hole wall collapse. Based on the analysis of the characteristics of the sand layer, the ultra thick sand layer under the geological conditions of the construction of bored piles are the following difficulties: sand setting quickly, prone to drill burying accidents, breast wall mud proportioning is insufficient, can’t maintain the stability of hole wall, reinforcing cage install bridging efficiency low, cause the sludge inside hole long grit too thick. According to the above problem, the paper introduced the construction, the key technology research and improvement, finally forms the construction method applied in rotary drilling and reamed pile in super-thick sand layer.Based on the construction of Nan Ning East Station pile project in super-thick sand layer, through the effect of pile inspecting, the method improves the porosity of pile blast-holes, verify the feasibility of the construction technique and economic benefit, it is obtained that the bearing capacity of the ordinary pile is larger than the bearing capacity of the trial pile by analyzing them, and the cumulative settlement characteristics is small. It shows that the construction method is reliable and feasible.