Abstract: Water pressure of groundwater can be separated into hydrostatic pressure and hydrodynamic pressure in evaluation model of slope stability and the mechanical analytic model of slope stability is developed by using residual thrust method when considering water pressure of groundwater. Formulas are also induced to calculate the thickness of aquifer and water head in any point between the two points in which groundwater table is given. Taking groundwater table and shear strength index as stochastic variables and the distribution features of these two variables can be obtained basd on the monitored and tested data, the analytical method of slope reliability based on Monte-Carlo method and residual thrust method has been put forward to analyze the slope reliability of a highway slope. Analytical results show that there is a positive correlation between the change of groundwater table and the change of failure probability of slope. Failure probability of slope is approximately 60% when taking groundwater table as stochastic variable, but is 10%-30% when taking groundwater table as determinable variable during the periods of July, August and September when groundwater table changes dramatically.In other months, groundwater table varies slightly and failure probability of slope also varies slightly, but the failure probability of slope when taking groundwater table as stochastic variable is always higher than that when taking groundwater table as determined variable.

Key words: reliability of slope, randomness, groundwater table, residual thrust method, safety factor, groundwater