ELASTIC MODULUS'S EVOLUTION LAW OF PLAGIOGRANITE UNDER CYCLIC LOADING

This paper presents the increasing-amplitude cycle loading experiment of plagiogranite through the MTS815 rock mechanics testing machine. It examines the effects of number of cycle, confining pressure and moisture content on elastic modulus, and analyzes the variation of work stress,elastic strain energy and dissipated energy with increasing number of cycle. The process of rock compression deformation and failure is divided into four stages according to the energy change law. It researches the relationship between tangent modulus and dissipated energy. The experimental results show that:(1) The tangent modulus at the same stress level is increased and then decreased at the cycle times increases. Its decreasing amplitude increases as cycles and stress level increase. (2) The weakened amplitude of tangent modulus decreases with increase of confining pressure. (3) The weakened amplitude of tangent modulus of saturated samples is bigger than that of natural samples, which shows that water is aggravated damage on saturated samples. (4) The increase of dissipated energy is the cause of the tangent modulus weakening. The change rules of dissipated energy and tangent modulus are correlative.