Chapter 9 - Changes of Permeability Due to the Excavation of Ship-Locks of the Three Gorges Project, China

Abstract

Permeability is a key parameter that governs the flow of fluid through a fractured rock mass. These models require sufficient data to generate a statistical mean pattern of fractures, which is then analyzed to obtain equivalent continuum permeability properties. The permeability of a fractured rock mass is dependent on the stress state. This chapter applies the permeability concept to an engineering problem involving the excavation of a large rock mass and predicts the associated change in permeability. The study performed in this chapter involves the excavation of a series of ship-locks in the Three Gorges Project in China. Twelve 2D fracture patterns mapped on three orthogonal planes were used to represent the fracture geometry of the rock mass. These 2D permeability tensors were calculated by the superposition of flow rates in two orthogonal directions through the fracture patterns on each plane. An approximate 3D permeability tensor was then estimated using these three 2D permeability tensors. Based on the results, the chapter highlights that the permeability must be expected to increase significantly after excavation.