填石层超深预应力管桩综合施工技术

Comprehensive Construction Technology of Ultra-deep PHC Pile in the Stone Filled Layer

在超过10m以上的深厚填石层施工大直径超深预应力管桩,通常先采用冲击钻进引孔,穿越填石层后回填砂土再施工管桩,存在填石层冲击引孔时间长、易垮孔、护壁泥浆量大、综合费用高等弊端。在上部填石层采用大直径潜孔锤引孔以穿越填石层,使用筒型钢桩尖以提高桩管的穿透力和垂直度,设置专门的双向泄水孔以克服地下水浮力,达到了引孔速度快、锤击穿透效果佳、施工费用低的效果。

PHC pile construction with 800ram diameter and over 50 meters depth in more than 10 meters deep stone filled layer, it＇ s usually using traditional construction technology of impact holing. Impact holing method is adopted to pass through the stone fill layer, then backfill sand and construct PHC pile. There are several disadvantages in the previously mentioned method such as spending much time in impact holing, easily causing hole collapse, a great quantity of mud for hole protecting and high cost. In this paper, the authors suggest a new construction technology that using the large diameter DTH hammer to pass through the stone fill layer, and then use long cone steel pile tip to pipe the PHC pile for its high penetration and the perpendicularity of PHC pile can be guaranteed. Besides, there is especially designed two-way drainage hole on the pile to overcome the buoyancy of groundwater. This comprehensive construction technology has the advantages of drilling hole faster, being good at penetrating the stone fill layer and lower cost.