Back Analysis Of Construction Monitoring In JinPing Ⅰ Hydropower Station Underground Workshop Caverns

Lagrangian analysis has been used widely in geotechnical engineering in recent years. However, back analysis, especially back analysis system associated with the famous software FLAC3D has rarely been reported. In the present dissertation, a back analysis system has been set up adopting FLAC3D as its nonlinear analysis module, and Artificial Neural Network as its back analysis tool. The stability of the surrounding rock mass of the underground power plant of JinPing I project has been analyzed using this system. Meanwhile, a new criterion to evaluate the stability of the surrounding rock mass is suggested, based on the current criterions of evaluating the stability of the surrounding rock mass and the results of numerical simulation. The criterion is validated from the numerical examples of the transects in the erection bay. The major contributions of this dissertation are as follows:1. Solve the problem of data exchange between exterior control program and FLAC3D software by adjusting the structure of the data file of FLAC3D software, defining correlative variables, preparing FISH files, accessorial applied files and batch program files. A software system of the construction monitoring back analysis for underground caverns is therefore set up. The optimization of the parameters can be automatically performed by this system.2. Suggest a new criterion to evaluate the stability of the surrounding rock mass, based on the uniformity of the displacement of the cavern. The criterion is validated from the numerical examples of the transect in the erection bay. This criterion is valuable to evaluate the stability of the surrounding rock mass.3. Regress the initial field stress at the construction site of the underground power plant of JinPing I project by Lagrangian analysis. Three load parameters for 2D analysis, including horizontal initial velocity and vertical initial velocity at upstream and downstream border of the model are obtained. The subsequent back analysis is performed based on those load parameters.4. Optimize the three initial velocities which reflect the initial field stress, as well as the elastic modulus of the rock mass according to the in situ measurement deformation. That makes the subsequent analysis result more credible. Then the evaluation and forecasting of the stability of the surrounding rock mass of the underground power plant of JinPing I project were made by the adjusted parameters, so as to provide reasonable suggestions for the safety of the caverns in the following excavation.Research on back analysis system associated with FLAC3D provides an effective approach to perform real-time back analysis during the construction of the underground powerhouses.