Evaluation of Groutability in the Pliocene Conglomerate by SPI Method for Sealing (A Case Study)

The Dorud - Khorramabad Railway, with a length of 114 km, is under construction in 5 separate phases. In terms of geology, a large part of the route passes along the High Zagros and the Chaghalvandi Thrust in the form of tunnels and other structures. Phase 5, which is 26 kilometers long, from the 72nd kilometer to the 98th kilometer, between the Biran-Shahr Plain and the Deh-Pir region in North Khorramabad City, has two tunnels with a length of more than 7,500 meters. Given the local climate and the ground water level (average depth of 10 meters) on this route, for the sealing of the tunnels, it is necessary to study the rock mass. For this purpose, it is necessary to understand the characteristics of Pliocene Conglomerate including the mechanical and the physical parameters of the tunnel. The present study tries to determine the permeability by means of the data of water pressure tests. The groutability in this rock unit, in turn, was determined based on the Secondary Permeability Index (SPI). The results show that the behavior of this rock mass is 19% in Class C, 67% in Class B, and 14% in Class A in terms of the SPI, and that 86% of the rock mass needs to improve by means of cement grouting operations. Totally, because of similar geological conditions in the railway route, all of the railway route needs to improve.