1. State Key Laboratory of Structural Analysis for Industrial Equipment，Dalian University of Technology，Dalian，Liaoning 116024，China；2. College of Water Conservancy and Civil Engineering，China Agricultural University，Beijing 100083，China
Abstract：The problem of membrane penetration can be studied quantitatively based on digital image measurement system. By non-contact measurement technique of the digital image system，the precise volume changes of specimen and water pipe can be gained. The volume change of water pipe includes the specimen¢s volume change and that caused by membrane penetration. Through the drained-loading tests of some sand materials，using the planar deformation assumption，the membrane penetration is obtained by subtraction the specimen skeleton¢s volume change from the discharge pipe¢s in the process of drained-loading test. Based on the test results，the relation between the membrane penetration and its mainly influential factors，such as s3，d50，are analyzed and the formula of membrane penetration is improved. It is not reasonable for graded sand including high percentage of fine particle using d50 to analyze the membrane penetration. The influence of gradation¢s uneven or other characteristic particle size should be taken into account.
