回转反循环若干特殊施工工艺的工程实践

Engineering Practices of Some Special Operational Technology in Rotary Inverse Circulation Pile Construction

针对在含有大径卵石块的地层、纯砂层,以磨擦桩为主的地层中进行大孔径回转反循环桩施工,提出了三种特殊施工工艺:筐捞法,小径漏石法,二次成孔法。筐捞法是在卵石直径小于孔半径10cm的地层中,利用焊有筐状盛器的钻头,通过钻具的旋转将卵石装入筐内,清除孔外;小径漏石法则是先钻一小孔径钻孔至漏石合适的深度,该深度要保证在大径钻头成孔时,石块或卵石能够落入漏石孔底,使之不影响钻进的连续性;二次成孔法是针对胶结性差、渗透性好的地层的一种施工工艺,其原理是利用密度约为1.15g/cm3冲洗液,在第一次钻孔后的犬牙交错的孔壁上,形成一定厚度的泥浆浸入带,保护二次成孔时孔壁不再产生损伤。

Aimed at large grain size pebble contained,pure sand,mainly friction pile constructing strata carry out large sized rotary inverse circulation pile construction,put forward three special operational technologies: basket dredging,small sized hole enable pebbles fallen into and second time well completion methods.The basket dredging method is used in strata with pebble diameter less than 10cm well radius,using drilling bits welded with basketlike receptacle,through drilling tool's rotary setting in pebbles and finally clear away from well;the small sized hole enable pebble fallen into method is to drill a small sized hole first to the depth enable pebbles fallen into,the depth should ensure when the larger sized bit is used in well completion rocks or pebbles can fall into the bottom of falling hole and not influence on drilling continuity;the second time well completion method is an operational technology used in poor cemented,strong permeable strata,the principle is to use flush fluid with density about 1.15g/cm3 that can form a mud immersed belt with enough thickness on first drilled jigsaw pattern wall to ensure the wall not to be damaged during the second time well completion.