中国西部地区典型岩质滑坡机理研究

本文根据作者在中国西部地区多年的研究工作实践,对几类典型的大型岩质斜坡变形及失稳机理进行了较为深入的分析,重点阐述了这些大型滑坡形成的地质条件、斜坡变形过程及发生机理的"概念模型",其中包括滑移-拉裂-剪断的三段式模式、挡墙溃决模式、"超级强夯"模式等.这些机理及模式的提出,对这一地区的防灾减灾实践具有一定的指导意义.

MECHANISM OF LARGE SCALE LANDSLIDES IN WESTERN CHINA

Lots of evidence show that landslides have increased in China since 1990s,especially some typical hazardous landslides. Even though this kind of increase has been thought to be related to the large scale infrastructures construction, it is a common sense that the fundamental geologic-mechanics model should be involved in the sliding process. Therefore, it is very significant to discuss the mechanism of these landslides and finalite some typical models. The author's work reveals:(1) Creep-tension-shearing fracture model (three segments mechanism): This kind of mechanism occurs in the slope contained nearly horizontal or gently out-inclined soft layers or weak planes. With the unloading process of the slope from river down erosion or slope cutting, the creep deformation occurs along the weak plane and a tension crack will appear at the top of the slope. The continuous creep deformation will promote the gradually deepening of the tension crack and a locked segment will appear at the middle part of the potential slip surface. When the concentrated stress reaches a critical extent, the locked section will be cut through with a sudden brittle shearing failure, and a hazardous landslide occurs.(2) “Retaining wall” collapse model: It generally occurs on the slope with a soft base and a rigid section above it. The later one can be regarded as a “locked section” on the slip surface and it acted as a “retaining wall” because it supports the driving force from the upper slope. Obviously, the stress will be accumulated gradually behind the “retaining wall” with the increasing of the driving force from the upper slope and the continuous squeezing out deformation of its soft base. Finally, the “retaining wall” located at the middle part of the slope will be destroyed due to exceed stress accumulation, and the slip surface will be formed.(3) “Super punching” mechanism model: It describes the process that a unstable block slides down from a sharply steep slope or mountain and it impacts very strongly on a debris at the slope foot, and induces the debris integrating suddenly and flowing a long distance in a moment time. Generally, the unstable block has huge potential energy owing to its high position, and its instability comes very suddenly.