The influence of intact rock properties on tunnel boring machines (TBM) penetration rate was studied and an empirical equation for estimation of the TBM penetration rate based on the properties of the rock being excavated was introduced in this study. In practice, a database containing measured TBM penetration rates and intact rock properties was established. The data was collected from the 30-kilometre long Karaj-Tehran water conveyance tunnel hard rock TBM project, about 16 kilometers of which was driven to date. Actual penetration rates at different consecutive locations were recorded using the data acquisition system on the TBM. On the other hand, determination of the intact rock properties corresponding to the monitoring locations was performed. In this respect, the main properties of the intact rock effective on the penetration rate were considered as compressive strength, tensile strength and brittleness. The rock tests including uniaxial compressive strength using point load test, tensile strength using Brazilian test and rock brittleness using punch test, were performed at the rock mechanics laboratory, Tarbiat Modares University. Statistical analyses were performed on the data obtained from the field and the laboratory. The results revealed that intact rock properties have strong effect on TBM penetration rate. It was also concluded that TBM penetration rate could be estimate.
Since the first TBM machine was built, the performance analysis of the machines and the development of accurate prediction models have been the ultimate goals of many researchers. Graham in 1976 estimated the penetration rate of TBM by uniaxial compressive strength between 140–200 MPa [1]. Farmer and Glossop in 1980 suggested a relation between Brazilian tensile strength and penetration rate in alluvial rocks [2]. Cassinelli in 1982 determined the penetration rate of TBM by use of RSR [3] and Innaurato et.al In 1991 developed a strong relation between RSR, UCS and penetration rate of TBM [4]. Saffet Yagiz in 2007 earned a relation between rock mass properties and TBM penetration rate [5]. In this study, the effect of intact rock properties on TBM performance is considered.
The karaj-Tehran water conveyance tunnel located between Karaj and Tehran was considered as the case study. This tunnel will transfer water from Amir Kabir dam to Tehran. This area is composed of 15 geological units from U1 to U15. This study focuses on U4 which is composed of shale, siltstone and conglomerate [6]. The location and the orientation of the tunnel are shown in the geological map in Fig.1.
Access to the wall rock and face rock in the tunnel was restricted as double shield TBM was employed. Consequently, sampling was performed by collecting rock from the contents of cars transferring broken material outside.ical map in Fig.1.
