Comparison of EPB tunnel boring machine performance in cohesive and frictional soils

Prediction of EPB (Earth Pressure Balance) TBM's performance is a significant issue in tunnel projects in terms of low-cost and target schedule. This study was conducted based on the measurements made in the Sofia Metro Line-3 tunnel in order to determine the effects of the soil type (cohesive and frictional) affecting the EPB TBM excavation performance. The investigated parameters were: cutterhead torque, EPB TBM thrust force, specific energy and instantaneous cutting rate. The studied tunnel section is divided into three zones with respect to geotechnical parameters such as grain size analysis, Atterberg limits and consistency behavior. Data analysis was performed by linking the cutterhead torque, TBM thrust force, instantaneous cutting rate and specific energy with the geotechnical properties of high plasticity clay, low plasticity clay and medium-grained sand. TBM performance analysis reveal the correlation between the operation parameters of the machine and soil type, and thus, main incidents that make an effect on the performance of the machine are determined. Analysis is critical in terms of the information backlog required for such projects that shall be implemented in the future.