Research on Key Construction Technology of Rotary Excavation Pile in Deep Sand Layer in Shanghai
The geological conditions of Shanghai East Railway Station of Eastern Hub located are special.The deep sand layer is below 30m on the surface.The 7th and 9th layers are connected.When the conventional rotary excavation construction technology is adopted,the rotary excavation pile construction is prone to shrink and collapse,and the thickness of the sediment at the bottom of the hole is as deep as several meters,hence,the construction quality is difficult to guarantee.The construction parameters are determined by a field test.The research was carried out on the aspects of wall mud mix ratio,hole-forming stability of deep sand layers,construction technology and equipment transformation.The main problems of rotary drilling piles in deep sand layers,which are surface orifice collapse,suction negative pressure effect,and deep sand soil shrinkage,were analyzed.The targeted optimization measures of casing length optimization,drilling bit form transformation and mud parameter control can ensure the hole-forming quality of rotary drilling piles in deep sand layers.The key technology of rotary drilling pile construction under special geological conditions of deep sand layers in soft soil is further summarized and formed.
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