Assessment of Double Shield TBM performance by using downtime index (DTI)

In mechanized tunneling, TBM performance prediction is vital to estimate the time and cost of the project.Therefore, calculating the performance parameters is so important. The utilization coefficient depends onmanagement parameters, personal ability, logistic utility and equipment, tunnel characteristics, objectivesand geological conditions. Although in each of the main models same as CSM, NTNU and QTBM, thespecific parameters used to estimate the utilization coefficient, the effect of management factor andinteractions and overlapping factors not considered. On the other hand, many parameters have a severedependence on each other and may simultaneously affect the performance of the TBM. Therefore, theinteraction matrix can be used to evaluate the interaction of parameters on each other and on TBMperformance. The effect of 18 parameters on the utilization coefficient was evaluated by the matrix methodin Karaj water conveyance tunnel. The interactions of these parameters show that the lack of utility servicesand shift change have the most significant impact on TBM performance. By recording the actual delays ineach parts of tunnel, the downtime index (DTI) is obtained; this index has a direct relationship with tunnelboring time and is inversely related to TBM performance.