His approach is presented in this chapter.įigure 4.47. Using Q TBM, Barton (2000a) believed that the performance of TBMs in a particular type of rock mass may be estimated. The TBM should not be used in squeezing ground conditions, rock burst conditions, and flowing grounds, because it is likely to get stuck or damaged.īarton (2000a) incorporated a few parameters in the Q-system that influence the performance of a TBM to obtain Q TBM (i.e., rock mass quality for an open TBM). This can be explained by engineering rock mass classification. The advance rate (AR) of 2.5 m/h has declined to 0.05 m/h in the same project. Earlier in the same project, 270 m of unexpected glacial debris took nearly seven months. Even from a 1967 open TBM, Robbins (1982) reported 7.5 km of advance in shale during four months. There have been continuous efforts to develop a relationship between rock mass characterization and essential machine characteristics such as cutter load and cutter wear, so that surprising rates of advance become the expected rates. Contractors can design TBMs according to the given rock mass conditions, which are nearly homogeneous. Engineers should not use TBMs where engineering geological investigations have not been done in detail and rock masses are very heterogeneous. However, set-up and dismantling time are significant and the range of available tunnel cross-section shapes is limited ( Okubo, Fukui, & Chen, 2003). The basic advantages of TBMs are high safety with low overbreaks, little disturbance to surrounding rock mass, and low manpower. The problem lies in the extremes of rock mass quality, which can be both too bad and too good (no joints), where alternatives to TBM may be faster ( Barton, 1999). When rock conditions are reasonably good, a TBM may be two to four times faster than the drill and blast method. The expectation of fast tunneling places great responsibility on those evaluating geology and hydrogeology along a planned tunnel route. Tunnel boring machines (TBMs) have extreme rates of tunneling of 15 km/year and 15 m/year and sometimes even less. Goel, in Engineering Rock Mass Classification, 2011 Introduction
0 kommentar(er)
