CCS水电站600 m深竖井反井钻机施工塌孔分析

Analysis and Treatment of Hole-Collapse Accident in the Construction of a 600 m Shaft Constructed by Raise Boring Machine in CCS Hydropower Station

竖井作为地下建筑物,地质条件复杂多变,对反井钻机施工影响较大。CCS水电站布置两条600 m级超深竖井,其中2#竖井在反井钻机施工过程中出现塌孔事故,进而大量涌水并导致设备损坏。结合塌孔特征和附近已开挖建筑物工程地质条件对塌孔原因进行分析,初步推测应是下平段揭露的f46、f47断层与R3流纹岩脉相交部位围岩稳定性差,造成塌方,在高水头作用下,陡倾岩体破碎带形成了地下水径流通道。针对塌腔发育情况和周边工程地质条件利用钻探、物探、激光扫描、地下水示踪等手段开展补充勘测,从而进一步查明竖井区工程地质条件,证实塌孔原因,确定塌腔发育部位、规模和性状等,据此确定新竖井孔位。在新孔位导孔施工过程中,根据钻进参数、渣料、返水等情况对工程岩体条件进行分析判断,及时对不良地质段进行灌浆加固,在导孔施工完成后采用全孔纯压式灌浆。在新竖井人工扩挖时,通过M9支洞对塌腔进行密实回填,顶部回填困难区域采用模袋混凝土填充,以减少塌腔对竖井运行安全造成的影响。

Geological conditions of the shaft as an underground building are complex and changeable,and have great influence to the con-struction of the raise boring machine.There are two 600 m super-deep shafts at CCS Hydropower Station.The shaft No.2 collapsed in the con-struction,which resulted in a large amount of water inrush and damage to the equipment.Combined with the characteristics of collapse hole and the engineering geological conditions of nearby excavated buildings,it was preliminarily speculated that the surrounding rock stability at the intersection of f46,f47 and R3 rhyolite veins should be poor.Furthermore,the broken zone of steep rock mass formed groundwater runoff channel under the high water press.We carried out supplementary survey using drilling,geophysical exploration,laser scanning,groundwater tracer and other means,so as to further find out the engineering geological conditions in shaft area furtherly,confirm the causes of collapse hole,and determine the development location,scale and characteristics of the collapse cavity.According to this,we chose the new hole posi-tion downstream of of the previous shaft about 50 m,and analyzed the rock mass conditions of new position according to the drilling parame-ters,slag material,return water and so on.The bad geological section was strengthened by grouting in time and the full hole was grouted completed after the completion of the guide hole.The collapse cavity was backfilled through M9 branch tunnel,and the difficult area at the top of the collapse cavity was filled with membrane bag concrete,in order to reduce the influence of collapse cavity to the safety of shaft operation.