ANALYSIS OF PARAMETER SENSITIVITY AND JUDGEMENT OF STABILITY RELIABILITY FOR FALLING UNSTABLE ROCK

In the harder-hit earthquake areas such as Wenchuan, the constancy of unstable rock is considered as a key work of the disaster control because there are many kinds of geologic hazards caused by the earthquake. This paper is based on the reliability theory and uses the limit state characteristics of falling unstable rocks. It establishes the equation of constancy judging probability limit state. It also determines the mean value, variability and distribution shape of the unstable rock angle of rupture, the unstable rock angle of equivalent internal friction, weight per unit length, equivalent cohesion, height and other basic variables in the functions by means of field measurement and probability statistics. Based on these studies, the paper develops the calculation method of falling unstable rock stability reliability index. At the same time, it studies the parameter sensitivity of each basic variable. The result shows that the variables in descending order from high to low sensitivity are the unstable rock angle of rupture, the equivalent cohesion, the height, the weight per unit length and the angle of equivalent internal friction. The result offers a reference in judging the constancy of unstable rock and designing of a regulation scheme.