Application of rock mass classification systems for tunnel temporary support : a case study

Abstract

Rock mass classification systems have gained wide application and are frequently adopted in rock engineering feasibility and design. However, as all of these systems were developed based on empirical approach, they may have limitations. It is important that such rock mass classification be applied appropriately and with care. This study based on the application of rock mass classification systems and design of rock tunnel temporary support with reference to a case study in Hong Kong. In design stage, the tunnel temporary support was estimated based on an empirical method. However, as the ground conditions encountered during tunnel excavation deviates from the original design, the design of temporary support had to be revised to cater for the unforeseen ground condition. The purpose of this study is to assess the application of rock mass classification for planning purposes and for prescription of rock support during construction. Data has been obtained from empirical design, tunnel excavation mapping, and numerical analysis.