Unloading Mechanical Character Of The Surrounding Rock Of The Jinping Hydraulic Power Plant And Its Application

In rock engineering ,rock and tunnel excavation is under unloading condition, this is absolutely contrary to the rock mechanics analysis ,which always use loading condition parameters and according calculation methods. Even considering linear unloading during the excavation simulation ,it is also conducted by normal method and its constitutive equation and parameters calculation software is in fact considered as loading condition. In fact, excavation is a process of unloading, not only the load is unloading, but also stress condition parameters and constitutive relation are also under unloading condition.Currently, the excavation analysis results do not fit to in-situ measure .sometimes the difference is ten times ,this is mainly because the analysis parameters and model do not fit to the actual loading condition, this thesis mainly discuss marble surrounding rock of the Jinping hydraulic power plant , and some conclusions are summarized as the following:(1) Aim at the great difference between the in-situ measure and normal loading analysis result, indoor unloading experiment are carried out using marble surrounding rock of the Jinping hydraulic power plant, and the mechanical characters during unloading are analyzed.Microstructure method are used to analyze the marble surrounding rock of the Jinping hydraulic power plant. Under the condition of principle stress kept unchanged, the failure section of specimens are scanned by SEM,stat the microstructure using computer, the changing laws under unloading are discussed.(2) By assuming the damage of rock infinitesimal is fit to statistical law, a damage variable is defined, and a constitutive equation considering the influence of unloding is deduced. By data fitting, the parameters under different unloading failure are obtained, and it has been verified that the model curve can fit to the experimental curve well.(3) A FEM equation is deduce from the statistical damage constitutive model, a calculation is conducted to the Jinping water guiding tunnel excavation using the the program according to the constitutive model, and FEM result which do not considering unloading is compared to the above result.