Modeling the effect of water, excavation sequence and reinforcement on the response of blocky rock masses.

摘要

A powerful numerical method that can be used for modeling of fractured rock masses is the Discontinuous Deformation Analysis (DDA) method developed by Shi in 1988. This thesis presents three new extensions to the DDA method. The extensions consist of hydro-mechanical coupling between rock blocks and water flow in fractures, sequential loading or unloading, and rock reinforcement by rockbolts, shotcrete or concrete lining.; Simulations of the underground excavation of the “Unju Tunnel” which is part of the “High Speed Railway Project” in Korea were carried out to evaluate the influence of water flow through joints, excavation sequence and reinforcement by rockbolts and shotcrete, on the tunnel stability. The results of the present study indicate that joint water flow and improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is shown that the phases of construction (excavation, reinforcement) can now be simulated using this new program.; In this thesis, the DDA method with the hydro-mechanical algorithm is used to study the effect of rock discontinuities on uplift and seepage in concrete gravity dam foundations. This thesis presents an alternative method of predicting uplift and seepage at the base of concrete gravity dams. The study shows that joint water flow and adverse geological conditions could result in unusual uplift at the base of concrete gravity dams, well in excess of what is predicted with the classical linear or bi-linear pressure assumption. Drains can be very effective in reducing that uplift if their location, diameter, length, and orientation are chosen properly. It is shown that, in general, the DDA program with the hydro-mechanical algorithm can be used as a practical tool in the design of gravity dams built on fractured rock masses.; An alternative method for determining the value of the discontinuity orientation adjustment coefficient R6 in the RMR system of Bieniawski (1989) was presented for a rock mass intersected by two orthogonal joint sets. In the analysis, the joints were assumed to be either vertical or horizontal or dipping at 45°. The proposed method showed that the value of R6 in the RMR system depends on the joint dip angle and that its value can be determined by using the DDA method. (Abstract shortened by UMI.)