Empirical modeling for predicting excavation performance of EPB TBM based on soil properties

Abstract

This study was conducted in order to determine the effects of soil properties on the excavation performance of an earth pressure balance tunnel boring machine (EPB TBM) used in the Istanbul Ayvali Waste Water Tunnel Project in the development of empirical performance prediction models. The tunnel alignment was divided into three general sections in terms of geological and geotechnical conditions. Soil samples were collected from 14 different locations along these sections of approximately 60 segment rings, and subjected to laboratory tests in order to determine the particle size distribution, natural water content, consistency limits (liquid limit, plastic limit, plasticity index, and consistency index), vane shear strength, fall cone penetration depth, unified soil classification, and clogging potential. The field performance data were obtained from the EPB TBM data logger, which operated in open mode without any face pressure being applied. Data analysis was carried out by statistically linking the net cutterhead torque, TBM thrust force, instantaneous cutting rate, and field-specific energy with the geotechnical properties of the excavated clayey soil by using single and linear multi-variable regression methods. The results indicate that, while the performance parameters are similar for the silty sand and lean (low plasticity) clay, the cutterhead torque and field-specific energy are higher, and the thrust and instantaneous cutting rate are lower, for high plasticity clays. The vane shear strength and consistency index may be used for predicting the cutterhead torque, fall cone penetration depth for the thrust force, plastic limit for the instantaneous cutting rate, and plastic limit and plasticity index, as well as the consistency index, for field-specific energy predictions. Additional studies are required to provide more reliable and generalized prediction models, by increasing the number of laboratory and field tests for different soil types and performance data for different EPB TBMs.