The Effect of Geotechnical Properties of Rock Formation on the Productivity of Tunnel Boring Machines

Abstract

In 1964, a Komatsu-Robbins Tunnel Boring Machine (TBM) was used to drive a pressure tunnel of water power plant for the first time in Japan. Since this first experience for TBM up to 1979, tunnels driven with TBM amount to 34 tunnels and 28 km in their total length.The experiences on based the driving of TBM have indicated that the performance of TBM is obviously dependent on the geotechnical properties of rock formation, because they can find many case histories in which many troubles were caused by difficulties of rock formation.In this report, the authors discuss on the possibility of application of TBM for various rock formations and the effect of geotechnical properties on the performance of TBM, based on the experiences of operation of TBM in Japan.The geotechnical factors affecting the performance of TBM would be as follows;1) rock stresses around the tunnel, 2) discontinuities in rock formation, 3) strength and hardness of intact rock, 4) in situ strength of rock formation, and5) rate of inflow of ground water.Most of rock formations where tunnels had been driven with TBM are included in the areas (I) in Fig.3. In Fig.3, the abscissa in logarithm of the square of the index of discontinuty k2, and the ordinate is logarithm of the estimated in situ rock strength k2 ·σ.