Energy Evolution and Mechanical Features of Granite Subjected to Triaxial Loading‐Unloading Cycles

Abstract

Energy evolution varies during the whole process of rock deformation, and mechanical parameters are markedly altered under cyclic loading and unloading. In order to investigate the effects of confining pressure on energy evolution and mechanical parameters, cyclic loading and unloading experiments were performed for granite under six different confining pressures. The experiment revealed the confining pressure effect on variation and allocation pattern of energy and mechanical characteristics. Four characteristic energy parameters, namely, storage energy rock, storage energy limit, energy storage ratio, and energy dissipation ratio, were proposed to describe energy storage and dissipation properties of rock. Elastic modulus and dissipation ratio presented a downward “U” and “U”-shaped trends, respectively, with loading and unloading cycles, while Poisson’s ratio increased linearly at the same time. Elastic energy was accumulated mainly before peak stress, while the energy dissipation and release were dominant after the peak strength. As the confining pressure increased, efficiency of energy accumulation and storage limit improved. An exponential function was proposed to express the relationship between the energy storage limit and confining pressure. Dissipation energy increased nonlinearly with the strain, and the volume dilatancy point defined the turning point from a relatively slow growth to an accelerated growth of dissipation energy. The dilatancy point can be used as an important indication for the rapid development of dissipation energy.

Mechanical Properties and Energy Evolution of Fractured Sandstone under Cyclic Loading

“…They concluded that rock’s internal structure and axial loading stress were the main factors affecting energy storage. Based on the principle of energy evolution and the hysteresis effect of concrete, Pei et al [ 31 ] conducted triaxial cyclic loading and unloading tests to study the influence of confining pressure on the energy storage limit, energy storage ratio, and energy consumption ratio. Through analysis of the energy evolution characteristics of the hysteresis loop of the stress-strain curve.…”

Shear Slip Instability Behavior of Rock Fractures under Prepeak Tiered Cyclic Shear Loading

“…Many engineering projects have shown that rock is not in a stable stress environment but is subjected to a cyclic loading-unloading stress environment [9][10][11]. Tiered cyclic loading is a common form acting on rock mass, such as periodical change of the reservoir level and reciprocating motion of the train [12][13][14][15]. e rough fluctuation of rock fractures is suffered from periodic wear and passivation, leading to the deterioration of its shear strength under cyclic shear loading.…”

“…e essence of deformation and failure of rock mass is the instability driven by energy [15,23,24]. e energy evolution process involves energy absorption, agglomeration, dissipation, release, transformation and transmission [1].…”

Experimental Study on Mechanical Properties and Acoustic Emission Characteristics of Water Bearing Sandstone under Stable Cyclic Loading and Unloading

“…ey analyzed and summarized the evolution law of cyclic acoustic emission of stress-strain changes of different rocks in loading and unloading stages. Pei and Yang et al [22,23] carried out triaxial cyclic loading and unloading tests of granite and deep-buried marble specimens under different confining pressures, respectively. e results show that the modulus of elasticity decreases with the loading and unloading cycles, while Poisson's ratio increases linearly.…”