The Influence of Geological Features and Geomechanical Properties of Rock Mass on TBM Selection for Sabzkouh Water Conveyance Tunnel

The Sabzkouh water conveyance tunnel، with a length of approximately 11 Km to transferred 90 million cubic meters of water per year from the Sabzkouh area to Choghakhor Dam، about 80 Km south of Shahrekord in Chahar Mahal-e Bakhtiari province is under study. Because of the long length of this tunnel and also low rate excavation by traditional tunneling methods، the Tunnel Boring Machine has been a priority. Due to limitations of TBMs in complex and unfavorable geological conditions، based on the precise study performed، the machine was selected. The geological features and the geomechanical properties of rock masses play an important role to selection of proper TBM. In this paper، by estimation of the most important geomechanical properties and geological conditions of the rock masses، with the interpretations of geotechnical logs and the laboratory test results combined with field observations، the rock mass of the Sabzkouh tunnel، based on the three common engineering systems of RMR، Q and GSI was classified. According to classification systems، the rock masses are divided into three geotechnical zones. Based on the uniaxial strength of intact rock، the properties of discontinuities، fault thickness and shear zones، the underground water level and the squeezing intensity the performance of hard rock TBMs was performed. Finally، double shield TBM for the excavation of Sabzkouh tunnel is proposed