ANALYSIS OF SECONDARY TOPPLING MECHANISM OF JOINTED ROCK SLOPE UNDER SOIL PRESSURE

Secondary toppling failure is one of typical instabilities of steep stratified rock slopes. The limit equilibrium analysis method is the main method to analyze the toppling failure of rock slopes. Analysis of secondary toppling failure of counter-tilt jointed rock slopes has an important bearing on engineering practice, especially for mountain area of southwest China where there are many slope engineering. Based on the analysis method of limit equilibrium proposed by Goodman and Bray, a geomechanical model of the secondary toppling of counter-tilt jointed rock slope under the action from rear soil pressure are developed, The related analysis method is proposed. This model takes into account the factors such as groundwater pressure, joint connectivity, and rock cohesion. A formulation is derived for calculating the pushing force of each rock formation. The comprehensive safety coefficient is given. The stability of secondary toppling of counter-tilt jointed rock slope can be easily analyzed using a Matlab program, which provides a theoretical basis for the design and reinforce of this type of slope. An example is introduced. It analyses the influence of groundwater pressure, joint connectivity as well as rock cohesion on the pushing force of each rock formation and comprehensive safety coefficient. Compared with the block toppling failure of rock slopes, for secondary toppling failure of counter-tilt jointed rock slopes, from top to bottom, the rock formation above destruction surface is divided into three parts:the slip zone, the toppling area and the stabilization zone. The groundwater pressure, joint connectivity and the rock cohesion of the underlying fractured rock have obvious influence on the failure form and stability safety coefficient of each rock formation, especially in the lower part of the slope and the foot part of the slope. The minimum stability factor of each rock formation is concentrated in the upper part of the slope.