大光包滑坡滑带岩体碎裂特征及其形成机制研究  

Cataclastic characteristics and formation mechanism of rock mass in sliding zone of Daguangbao landslide

作　　者：黄润秋[1] 裴向军[1] 崔圣华 

机构地区：[1]成都理工大学地质灾害防治与地质环境保护国家重点实验室,四川成都610059

出　　处：《岩石力学与工程学报》2016年第1期1-15,共15页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(40972195);国家科技支撑计划(2011BAK12B03);四川省科技创新团队项目(2011JTD012)~~

摘　　要：大光包滑坡是"5·12"汶川地震触发的最大规模滑坡,滑坡南侧暴露长约1.8 km顺层滑带,其岩体高度碎裂,引起广泛关注,6 a来对此开展了持续研究。在前期工作基础上(工程地质测绘、坑槽探及浅孔钻探(钻孔声波)等),对滑带岩体的碎裂特征进行了充分的揭露和系统的描述,结果表明,滑带发育的地质基础是滑前坡体内部发育的层间剪切错动带。强震过程中,由于靠近发震断层的强烈垂向地震动,从而导致坡体沿相对软弱的层间错动带分离,并产生垂向振冲或夯击效应,导致层间错动带的进一步碎裂化。对滑带的细观分析表明,这种强震滑带碎裂化现象不仅存在,而且还表现出伴随碎裂过程的扩容效应。采用物理模拟和PFC数值模拟,进一步验证了强震过程中滑带的碎裂和扩容过程,揭示其产生的内在机制。研究表明,滑带岩体碎裂化及扩容现象具有特殊的工程地质和岩体力学意义:一方面滑带岩体的进一步碎裂、细粒化从物理上降低了滑带的摩阻力;另一方面,也是更为重要的是,由于滑带的夯击扩容,地下水将强力挤入扩容空间,从而可能激发水击作用机制,导致孔隙水压力激增,滑带抗剪能力急剧降低,从而促使滑坡骤然启动,产生高速滑动。Daguangbao landslide is the largest landslide triggered by ＂5·12＂ Wenchuan earthquake. The exposed sliding zone with a length of 1.8 km and highly ruptured rock mass occurred on the south side of the landslide,which attracted great attention across the world and was a focus in the past 6 years. The engineering geological mapping and exploration in the past made the cataclastic characteristics of rock mass in sliding zone to be well revealed. The sliding zone was found to be bedding on a fault zone of the slope. Because of the strong vertical ground motion near the seismogenic fault,the slope was separated along the bedding fault zone which was the relatively weaker interlayer. Vertical impacting or tamping within the weaker layer occurred leading to the further fragmentation. Mesoscopic analysis of sliding zone confirmed the existence of the earthquake induced fragmentation in sliding zone and revealed the dilation effect in the process of fracture,which was further verified with the physical simulation and PFC numerical simulation. The rock mass fragmentation and dilation of sliding zone were thus concluded to be very significant. Firstly,the further fragmentation and fine grains of the rock mass reduces the friction of sliding zone. Secondly,what is more important,because of the tamping and synchronous dilation within the sliding zone,groundwater will be strongly squeezed into the dilated space,which may stimulate the water hammer with the rapid increase of pore water pressure and the sharp reduction of shear resistance and as a result,causes initiation of the landslide suddenly with high traveling speed.

关 键 词：边坡工程 大光包滑坡 滑带 滑带碎裂 振冲扩容 水击机制 

分 类 号：P642[天文地球—工程地质学]