Studies On The Variational Problem And Endochronic Theory Of Unloading Fractured Rock Mass And Their Application

Fractured rock mass is one of the most common rocks engineering construction objects. Due to the disturbance of the construction, the original rock mass balance is broken, which causes redistribution of stress in the rock mass, procures the continuous accumulation and development of the inherent cracks (fissures) in the rock mass, produces macro-aging fracture, and leads to instability of rock mass destruction. In the actual project, most consideration is given to rock-loading theory in slope stability calculation and deformation, and often, the rock-unloading is an important factor affecting the stability of rock slope.The various stages mechanical mechanism of fractured rock mass constitutive relation under unloading condition is first revealed in this dissertation. The variational principle of unloading rock mass with σij、uij or σij、εij as second type variables in the initial value problems of both small deformation and large deformation is established through the usage of semi-inverse method. The corresponding energy functional is derived.On the basis of establishing the variation principle, the variational constraint conditions are added to the energy functional through the method of introducing the Lagrange multiplier, which further derives the generalized variation principle. Therefore, the generalized variation principle energy functional of unloading fractured rock mass with Cy σij、uij or σij、εij as second type variables in small deformation and large deformation were established.According to the endochronic constitutive basic theory by Vananis which depends on the material properties and deformation history and is used to describe the history dependence mechanical response of the entire deformation and temperature history function. Fractured rock mass is non-linear material; Building up endochronic constitutive relation of the unloading fractured rock mass in the primary stage and making comparison between the theoretical and experimental values verify the correctness of the application of endochronic theory in the primary stage of the the fractured rock mass. Take Jinggangshan project for example, the ground fissures appeared in the excavation process and cracks of rock mass in the Engineering were surveyed to explore the cracks features. According to the high-density electrical method principle, extending scope and development depth of the ground fissures, tilt direction of crack surface and other factors have been investigated and reasons for its formation were analyzed. Some relevant recommendations and measures had been proposed for the practical engineering.By using the analysis software ABAQUS, on the one hand, different conditions (natural state, after the rainfall, after the earthquake, after the completion of the new buildings) are taken into account to establish computational model for the lower part of the slope after excavation in the Jinggangshan project. On the other hand, ground material parameters were input to calculate and analyze the Slope stability. Stability factor was calculated under different conditions and the stability of the site was evaluated.In Combination with the unloading theory, considering that the upper slope excavation influences the lower part during the unloading process in the Jinggangshan Engineering, choosing the poor slope with factors containing cracks stability as the computational model in the excavation process.building the corresponding ABAQUS calculation model, Simulating excavation unloading process, analyzing the variation of the stress-strain during excavation cracks and making comparison between the calculated data and the theoretical value of endochronic constitutive theory provide a theoretical basis for practical engineering and make a further expansion for the application of the endochronic theory.