Karaj-Tehran water conveyance system is under construction with length of 30km. In order to excavate this tunnel, its length is divide to two parts. The first part with length of 15981 meters is being constructed with a double shield TBM. The whole length of the tunnel is running through Karaj formation which its lithology consists of pyroclastic rocks, tuffs, clays and sandstones. Unusual wear of disk cutters causes several difficulties in the project schedule and has increased the costs. On the other hand, high disk cutters wear rate causes an increase in specific energy for rock excavating. Therefore, the machine will be in adverse situation and will break down frequently. There are several reasons for disk cutter wear such as geological conditions and machine parameters which are interrelated to each other. In this paper asymmetric disk cutters wear are discussed. We have shown that if normal and rolling forces are not exerted sufficiently, the wear of cutters will increase significantly. In such situation, temperatures are arisen and affect disk cutter components in favor of cutter wear.
Nowadays, several tunnel construction projects with different purposes are under progress in Iran. Mechanized tunneling using tunnel boring machine (TBM) is increasing incredibly in Iran. Karaj-Tehran water conveyance tunnel is one of them. This tunnel has a length of about 30km with a circular cross section shape. It is one part of a water conveyance system that will transmit drinking water from Amirkabir dam to west of Tehran. Some of tunnel specifications are given in table
A double shield TBM is being used to construct the tunnel which its TBM specifications are mentioned in table
The whole length of tunnel is running through Karaj formation which its lithology consists of pyroclastic rocks, tuffs, clays and sandstones.
There are several parameters that affect TBM performance such as disk cutters wear rate, intact rock properties, discontinuities properties [1, 2] and operator skills. The main rock mass factors which are used to evaluate TBM performance prediction are compressive strength and tensile strength of rock material, frequency and orientation of rock joints. Effective machine parameters are TBM diameter, cutter line spacing, cutter diameter and tip width, total thrust and torque. All of these parameters are interrelated to each other [3]. In order to increase TBM performance, there are some special methods that reducing disk cutter wear rate and increasing their life are one of the most important of these methods. Disk cutter wear is a common problem taking place during hard rock tunneling projects. With increasing wear rate, the cost and time of project will increase and these are not desirable. For a cutter with defined metallurgical properties, wear rate is usually controlled by intact rock and rock mass properties and machines parameters. Many researchers have studied the wear mechanisms of disk cutters with different approaches. The influences of cutting geometry on rock chip formation in linear cutting tests are 1372 identified by Rostami and Ozdemir [4].
