Taking the Longmenshan complex geological environment as the study background, a geomechanical model with a reverse fault and subjected to horizontal tectonic stress is built and valley incision process is modeled. After excavation, the right slope has the contrary dip to faults but on the left slope the dip is similar to faults. Valley side slope presents tensile stress and the valley floor presents compressive stress. During valley incision the right slope display tensile stress state and its stress distribution show different characteristics of zonation from surface to inside of the slopes. As the valley incision depth increases, the position of tensile stress concentration area in right slope has changed from inside to surface, and lastly to the top of overlying fault. Stress state of left slope is complex and mainly performs tensile stress, but it also shows different characteristics in upper and lower slope.
The crustal stress refers to all stress distributed in the earth, which is a stable field in macroscopic and perform variety at one point with the time changing, namely, it is a function of the time and space (Su et al., 2002). When the concept of crustal stress was defined by A. Heim in 1912, it has become a focus to geologists all over the world and gotten a large number of acheivements (Cai et al., 1995; Lee et al., 1996).
The stress state of a slope adjusts continously with geological environment changing and determines it's deformation and failure mode, therefore, systematically and accurately grasping stress distribution characteristics have a great significance to slope stability evaluation and protection (Tang, 2011).
Valley stress is a special stress field which is influced by regional tectonic stress and formed by stress adjusting in valley floor and valley side slopes along with river incised process (Tian et al., 2002). There are plentiful hydropower resources in China, especially in the alpine valleys of southwest China. Since valley incision has brought a series engineering geological problems, the distribution of valley stress field gets more and more attention in recent years. Zheng Xiaoyan (2012) and TianYuzhong (2002) discussed the characteristic of valley stress by numerical simulation. In recent years, a large number of measured data have been accumulated in water conservancy projects in southwest China (Zheng et al., 2012; Bai et al., 1982; Huang et al., 1996) and provided reference basis for valley stress field study.
Studying valley stress field, especially the stress distribution of valley slope which is influenced by tectonic stress has great significance. Current research techniques are mostly limited to the numerical simulation. Although there are a large number of measured data, its research scope is limited and both of them cannot reflect the real stress state in the slopes. Therefore, the geomechanical simulation experiment of the valley excavation to reseaching the valley stress distribution is necessary.