地下水的致灾效应及异常地下水流诱发地质灾害

HAZARDOUS EFFECTS OF UNDERGROUND WATER AND EXTRAORDINARY WATER FLOW-INDUCED GEOHAZARDS

地下水是诱发和触发近地表地质灾害的最主要因素,在地质灾害评价、预测与防治中具有特殊重要的意义。本文对灾害过程中地下水的地质-力学作用一般原理和规律作了较为全面的分析,提出了地质体水敏性和水敏结构的概念,尤其对地下水的化学作用进行了较为深入的分析。结合具体实例,揭示了两类典型的极端情况下地下水触发地质灾害的特殊机理。一类是大型顺层滑坡发生过程中的地下水的“水垫-楔裂”效应;另一类是深埋长隧道中,地下水在高强度水头压力作用下的“劈裂”效应。两类效应在西南地区斜坡地质灾害和深埋长隧道的修建过程中都具有一定的典型意义。

Underground water is one of the most important and active factors inducing geohazards such as landslides and rockfalls. It is of great significance in the evaluation, prediction and control of geohazards. A comprehensive analysis was conducted of geological and mechanical actions of groundwater in slopes. It was pointed out that there were some water-sensitive structures in various slopes, which controlled the slope behaviors during water seepage. From two typical examples, we discovered “ water cushion effect” and “water splitting effect”. The former occurred in the slope failure of consequent slopes in the case of heavy rainstorm. The groundwater was closed in near slip surface and produced an extremely high water pressure, which caused the uplift of the whole slope like a “cushion”. The latter was found in deep-buried tunnels which lay much deep below the groundwater table. The groundwater squeezed out from closed fissures on the tunnel face under the action of high static water pressure and the fissures were widened gradually. Finally, the groundwater would gush out with extraordinarily high pressure （6～10 MPa）. Some basic evaluation principles were suggested for these two groundwater effects and some valuable control measures.