通过对亭子口水利枢纽工程坝基下卧的黏土岩、粉砂岩、长石石英砂岩和岩屑砂岩等 4 种主要岩性的岩体变形试验曲线特征进行分析，认为：厚层岩屑砂岩的试验变形量主要来自于岩石晶格错动变形，长石石英砂岩的试验变形量主要为岩石内孔隙和空隙变形以及岩石晶格错动产生的变形，而层理较发育的薄层黏土岩和粉砂岩的试验变形量主要由层间压缩变形、岩石内孔隙和空隙变形以及岩石晶格错动产生的变形共同组成。

Through the analysis of characteristics in curve of deformation tests on the four kinds of rockmasses such as claystone, siltstone, feldspar-quartz sandstone and lithic sandstone underlain the dam foundation of Tingzikou Hydropower Station, it is thought that: the test deformation of thick lithic sandstone is mainly caused by slippage deformation of rock crystal lattice ； the test deformation of feldspar-quartz sandstone is mainly from small crevices in rock, compressive deformation of rock small holes and slippage deformation of rock crystal lattice; and the test deformation of thin layer claystone in which horizontal layer is developed and siltstone is mainly from compression deformation in interlayer, small crevices in rock, compression deformation of rock small holes and slippage deformation of rock crystal lattice.