Effects of Water Related Factors on Pre-grouting in Hard Rock Tunnelling

Water control is highly concerned for underground facilities, and rock grouting has been used over decades to reduce the water inflow. The performances of grouting are influenced by many factors such as rock type, joint distribution and grouting materials. In this paper, the effects of water related factors are focused, from the engineering perspective. The observed volume of water inflow from the probe drilling hole often serves as the base for judgment of grouting needs. The allowable limit of water inflow varies for underground facilities of different purposes. For similar underground facilities, such limit may also differ substantially in different regions. High pressure of underground water would increase difficulty for grouting. The water appearance may give indication on whether the fillings of joints or the weakness zones have been eroded. In the coastal area, the inflow water can be saline, and this needs to be taken into consideration to eliminate corrosion on electrical installations underground.