Pre-grouting for Leakage Control and Rock Improvement

In underground construction, ground water inflow and rock mass stability has been a challenging problem. Especially the tunnels constructed below ground water table are often exposed to risk of ground water inflow. Protection of underground structures against water ingress and rock mass failure is of paramount importance during construction as well as operation of the tunnel. Risks associated with these hydrogeological issues often pose challenge to tunneling engineers. Mitigation of these risks by means of pragmatic measures such as pre-grouting can improve the rock mass strength and restrict the water ingress to acceptable levels. The primary purpose of pre-grouting is to improve the rock mass strength and establish an impervious zone around the tunnel periphery, thus leading to reduced support system and permeability of rock mass. The aim of this article is to discuss the concept of pre-grouting as an effective mitigation measure for leakage control and rock mass improvement which is being successfully implemented in many countries.