堆积阶地古老滑坡识别方法及其在线状工程地质勘察中的应用

Identification of Ancient and Old Landslides in Terraces and Its Application in Linear Engineering Investigation

阶地型古老滑坡体形成后,长期受各种营力影响,导致古老滑坡地貌形态破坏严重甚至消失。目前遥感技术和普通工程地质调绘很难发现这些滑坡的存在,给工程建设和后期运营造成较大安全隐患。为准确识别形态特征不明显的古老滑坡体,从阶地物质结构特征演变入手,找到阶地受剪切破坏产生的典型物质结构特征,将地层结构错断、卵砾石异常定向排列、摩擦镜面和泥包粒的眼球构造等作为滑坡准确识别依据。首先采用沿沟谷进行工程地质测绘的纵横交错追踪法确定滑坡体纵向范围和滑面形状,再结合地貌特征推测各级、块滑坡平面范围和分布,最后用点状勘探工程验证和校正推测结论。可将其总结为由"地貌异常、沿沟追踪、面上推断、点状校验"组成的阶地型滑坡识别方法,即物质结构异常推断法。结合线状工程勘察设计各阶段工作特点,提出线状工程前期工作中阶地型滑坡识别步骤,并在临渭高速公路工程建设项目中取得成功应用。

The ancient and old landslides of terrace type are often greatly influenced by external geological processes and human activities, and the morphological characteristics of landslides are seriously damaged or even disappeared;Therefore,it is difficult to determine their existence by remote sensing technology and general engineering geological mapping;However,they are potential hazards in constructions and operations. In order to identify the ancient and old landslides with unclear shape, the typical material structure caused by the shear failure of the terrace can be traced back from the evolution of the terrace material structure. For example, the broken stratigraphic structure, abnormal directional gravel alignment, augen structure of friction mirror and mud coated particles can be used as the basis to precisely identify the landslides. The criss-crossing tracking method of an engineering geological mapping along gully is used to determine the longitudinal range and sliding surface shape of landslide body, and then the plane range and distribution of landslides at each level and block are deduced according to the geomorphological features. Finally, the conclusion is verified and corrected by point exploration engineering. This terrace landslide identification procedure can be summarized as "recognizing geomorphological anomaly, tracking along the gully, surface inference,and point verification". Combined with the characteristics of each stage of the linear engineering investigation and design, the identification steps of terrace landslide during the preliminary work of linear engineering were put forward and applied successfully in the construction project of Lin-Wei expressway.