旋挖钻机在深厚卵砾石层超深大直径桩的应用

在桥梁超深大直径钻孔灌注桩施工中，国内通常采用大扭矩全液压回转钻机配备滚刀钻头钻进成孔，气举反循环排渣清孔。但对于深厚卵石地层，回转钻机钻进时需要破碎卵石，存在着钻进效率低、施工成本高、钻杆易堵塞、卵石层漏浆易坍塌等不足。本文针对深厚卵石层回转钻机施工中存在的不足，选用旋挖钻机钻孔，利用膨润土泥浆护壁，针对卵石层漏浆采取了可靠堵漏措施，通过气举反循环两次清孔，确保了孔底沉渣厚度，施工效率大幅提高，施工工期大为缩短，节约了施工成本，确保了桩基质量。

Application of rotary drilling rig in super deep and large diameter pile drilling in deep bouldery formation

In the construction of super deep and large diameter bored piles for bridges, the high torque full-hydraulic circulating drilling rigs are usually used with roller bits to drill holes and air lifting reverse circulation to clean the holes. However, for deep and thick bouldery strata, it needs to break the cobbles when drilling, and there are some disadvantages such as low drilling efficiency, high construction cost, drill pipe blockage, slurry leaking, borehole collapse. In view of the above-mentioned shortcomings, the rotary drilling rig was chosen to drill holes with the wall protected by bentonite mud. Reliable plugging measures were taken for the leakage of the bouldery layer and the hole was cleared twice by air lifting reverse circulation to ensure the thickness of the sediment at the bottom of the hole. The construction efficiency has been greatly improved; and the construction period has been greatly shortened which saved construction costs, and ensured the quality of the pile foundation.