The Influences Of In-situ Stress Characteristics And Mountain Inclination Angles On The Stability Of Large-scale Underground Caverns

The 21st century is the century for development and utilization of the underground spaces. With the development of science and technology, the number of underground projects is increasing, the scales are becoming larger and the technical problems are becoming more complicated. All these need higher requirements for studying the stability of the surrounding rock masses. The problems on the stability of the underground projects are widely concentrated in the field of rock and soil engineering.The stability of the surrounding rock is influenced by a number of factors, including the physico-mechanical parameters of the surrounding rock masses, the buried depths of the caverns, the horizontal lateral pressure coefficients of in situ stresses, the height of the main power house, the distance between the main power house and the transformer house, the inclination angle of mountains, and so on.Few researchers all over the world systematically made any research on the stability of the surrounding rock masses. Among them, Zhu et al. put forward a formula to predict the displacement of one key point in the downstream side wall by numerical calculations, considering the physico-mechanical parameters of the surrounding rock masses, the buried depths of the caverns, the horizontal lateral pressure coefficient and the height of the main power house. During studying the formula, the maximum displacement of the upstream side wall usually occurs at the corresponding position of the downstream side wall. And there is a relationship between two displacement values. To study the relationship, a FEM model was built and calculations under different situations were carried out, consequently a formula to predict the displacement of the key point on the upstream side wall was obtained and used in some actual projects.At the same time, as the distance between the main power house and the transformer house is also an important factor influencing the stability of the surrounding rock masses. Based on the original formula, a new formula to predict the displacement of key point on the downstream side wall was obtained by numerical calculations considering the physico-mechanical parameters of the surrounding rock masses, the buried depths of the cavern, the horizontal lateral pressure coefficients, the height of the main power house, the distance between the main power house and the transformer house. The new formula was verified in the actual projects.The stability of surrounding rock masses is also influenced by the inclination angles of mountains. In my thesis, the stability of surrounding rock masses was quantitatively studied by constructing two different kinds of models under the conditions of invariant buried depth, different lateral pressure coefficients and different inclination angles.