Attenuation characteristics of anelasticity and cumulative effect of damage

With the rapid development of infrastructure such as subway and high-speed railway, people should pay attention to long-term elastic fatigue load, especially dynamic load and highfrequency effect. In this paper, the relaxation attenuation peaks of temperature and frequency anelastic behavior of saturated sandstone and marble under forced resonance anduniaxial cyclic loading in the elastic range are studied at frequencies ranging from 0. 01 to 1000 Hz and temperatures ranging from 50 to 200 C. The results show that the elastic modulus and wave velocity decrease with the increase of temperature, and the decreasing gradient is steeper than that of general rock mechanics experiments. With the increase of frequency, the elastic modulus and wave velocity increase significantly, and the dispersion effect will strengthen. The results reflect the micro process of movement and interaction between micro damage such as micro defects in rock induced by stress, which will lead to the change of microstructure, and then cause micro displacement and micro damage. Micro damage may cause fatigue damage and fracture after a period or a long time of accumulation. The non-uniformity of microstructure in rock and filling or inclusion defects in rock is the weakest part form in rock, which will make a new microcrack system again under the action of cyclic stress, so as to accelerate the accumulation of damage and cause fracture. In addition, the residual stress of various channels in rock will lead to fatigue damage. The increase of vibration frequency will also accelerate the damage of rock. Combined with the comprehensive effect of temperature rise, it will cause the growth of microcracks in rock, lead to the change or damage of rock microstructure, degrade the quality of rock and rock mass media, and then lead to the damage of rock foundation. Although the anelastic damages are caused below the yield point, they will eventually degrade the quality of the rock.