Abstract:Because the blocks in deep rock mass exist in the form of tectonic order,therefore continuous medium mechanics as the analytic foundation of rock mechanics lacks basis. It is very important to explain and testify the experimental phenomena of ultra-low friction,because the influence of ultra-low friction among rock mass is the main reflection of the dynamic characteristics of block rock mass. The law is referred to describing the experimental phenomena of ultra-low friction and organizing the experimental data;then the dynamic model of block rock mass is established;and the theoretical and the numerical values are worked out to testify the correctness of ultra-low friction. By making such effort,the conclusion has been drawn as follows:the redistribution of vertical force and transformation of coefficient of kinetic friction are the fundamental factors of ultra-low friction. Furthermore,the tendency of experimental phenomena is consistent with that of the numerical results. The capability of storage and energy conversion is related with friction coefficient for the deep rock mass with tectonic level. A new branch of rock mechanics,nonlinear deep rock mechanics,is established. According to the static and dynamic characteristic phenomena and the characteristics of deep rock,the tectonic,deformation and failure problems of deep rock such as the block structure feature,the state of high earth stress,the stored energy and the nonlinearity,discontinuity and incompatibility of deformation,are suggested.