Abstract:Based on the uncertainty risk analysis theory,the depositional environment of the karst dam region is investigated. The method to describe the infiltration characteristics is systematically studied. The variability of permeability and the describing method of the corrosion rock mass are investigated. A new method measuring the variance of permeability is proposed,namely the error spreading function approach based on principle. The extreme values of the statistics parameters such as the width,spacing of the crack,and radius of the karst pipe can be calculated according to principle. And then the variance of permeability is obtained by using the cube law. By discriminating the jointed rock mass and pore karst cave,Kriging¢s random field theory and Vanmarcke¢s relativity theory on the study of geotechnical parameter variance are renewed and improved. Based on the geology statistical data in the field,the variance of permeability of the corroded rock mass in the grouting adit of Qingjiang Shuibuya project in a typical karst region in south China is computed. The proposed method is proved practical and simple. With variance of permeability provided,the random waterpower model can be constituted and then random permeability calculation can also be carried out.