President & CEO (Hydro),
Tunneling through Himalayan ranges is always a challenging job especially in the weak rock formation with high ingress of water creating flowing ground conditions. Occurrence of extremely poor strata in the form of shear zones or thrust zones or highly jointed rock mass while tunneling in Himalayas makes the job of construction engineers most difficult during execution and has a greater degree of uncertainity both in respect of time and cost. Different methodologies are required to be adopted while excavating very poor rock mass (class V) and exceptionally poor (beyond class V) rock mass. Most of the time proximity of seepage water creates flowing ground. Whenever such difficult situation is encountered, it is managed by many methods ranging from primitive manual methods to modern methods using state of the art technology and latest materials. Most of the hydro projects are encountered with such tunneling problems in a small or big way.
A system was evolved while working in one of the difficult project where large lengths of extra ordinary geological conditions were encountered. The system has been termed as 5P system of tunneling through extremely weak rock formations. The 5P system is a systematic way of dealing with extremely weak rock formation with high amount of seepage water.
This paper discusses 5P System in detail and the methodology to carry out the same for tunneling through extremely weak rock mass with high ingress of water creating flowing ground. The System was successfully used in one of the projects in Himalayan geology.
