Abstract: This paper presents a case history of mitigating the settlement of initial support of tunnel excavations in the saturated completely weathered granite soils and the factors that inducing the settlement are also investigated. The general guidelines for minimizing the settlement in the initial support are also proposed. Settlement mitigation measures, such as, dewatering around the excavated area, grouting from the ground surface and increasing the stiffness of the initial supporting structures and the construction monitoring system were established based on the theoretical analysis. The comprehensive approaches were applied in the construction and resolved the excessive deformation in the initial support of tunnel excavation in saturated completely weathered granite soils.

Key words: saturated, completely weathered granite, settlement of initial support, mitigation method