黄土坡滑坡的稳定性对三峡工程的安全运行具有重要影响,一直受到广泛关注,但滑带的空隙及渗透特性对滑坡稳定性的影响机制尚不清楚。从地下水渗流对滑带土作用的角度,利用中国地质大学(武汉)巴东野外综合试验场,结合室内试验的方法开展滑带土空隙结构与渗流特性研究。结果表明:①滑带碎石磨圆度、碎石分布形态、碎石表面擦痕、滑带土层理结构以及基岩面擦痕等特征明显,表明滑坡证据显著;②滑带土致密,层理结构明显,且层理间空隙尚未形成优先导水通道,而滑带土上、下盘接触面均存在贯穿性空隙或裂隙带,说明滑带空隙具有明显的空间分布特征;③滑带土饱和渗透系数低于上覆松散滑坡堆积体地层和强风化基岩地层2~3个数量级,导致降雨在滑带上盘集中排泄,基岩裂隙水在滑带下盘集中渗流,且在基质吸力作用下,上、下盘水分同时缓慢入渗滑带土,说明滑带土对滑坡体降雨入渗以及基岩地下水渗流具有显著的控制作用;④滑带土渗透破坏比降超过16,滑带土在自然水头作用下难以发生渗透破坏,具有很强的抗渗透破坏能力,说明地下水对滑带土影响主要体现在增加滑带土含水量,降低其力学指标,而渗透破坏作用有限。该成果对地下水作用下的滑坡形成机理研究具有重要意义。

The stability of Huangtupo landslide in the Three Gorges Reservoir area has always received attentions from researchers as it exerts significant influence on the safe operation of the Three Gorges Project. Nevertheless, the mechanism of porosity and seepage of slip zone affecting the landslide stability is still unclear. In the present paper, the pore structure and seepage characteristics of the slip zone soil of Huangtupo landslide are investigated in consideration of groundwater seepage via collecting samples from Badong field test site and by using laboratory approaches. Results reveal that 1) the roundness and distribution pattern of gravels, the clear stratigraphic boundary of slip zone as well as the friction marks between gravel and bedrock surface all indicate that the slip zone soil is of evident sliding features. 2) Penetrating cracks at the upper bound (interface between the slip zone soil and landslide accumulation body) of slip zone and the lower bound (interface between slip zone soil and bedrock) are the concentrated seepage channels of groundwater. The slip zone soil is of apparent stratification structure; however, the soil is dense, and groundwater doesn't flow preferentially along the gap between soil layers under the condition of low groundwater head. 3) The saturated permeability coefficient of slip zone soil is lower than those of overlying unconsolidated accumulation body and strongly-weathered bedrock by 2-3 orders of magnitude, which results in the concentrated drainage of rainfall water through the upper bound and fissure water in bedrock through the lower bound. Under the action of matric suction, the groundwater slowly infiltrates into the slip zone soil from both upper and lower bounds, implying that slip zone soil notably controls the groundwater flow. 4) Under natural water head, the slip zone soil is of strong resistance against seepage destruction as the seepage gradient at failure exceeds 16, which suggests that groundwater mainly increases the moisture content and reduces the mechanical properties of slip zone soil rather than destructs it.