A multiple-graph technique for preliminary assessment of ground conditions for tunneling

A novel multiple-graph technique has been proposed for the preliminary assessment of the ground conditions in the Himalayan region. This technique has been developed based on the sequential estimation of three quantities, viz. rock mass strength, competency factor and the ground condition. Rock mass strength is estimated from rock mass quality (Q). Moreover, two empirical ground classifications have been suggested, based on many case histories, for separately defining ground condition in soft rocks and hard rocks. A graphical work flow chart and practical illustration of this method has been presented using two sets of examples. The proposed technique is an efficient tool for quick estimation of the ground condition in the primary phase of design of tunnels and also during the excavation of tunnels.