Tool Wear Estimation in Erath Pressure Balance (EPB) Machine Tunneling

The use of mechanized excavation especially tunnel boring machines (TBMs), has grown more and more in tunnel projects. One of the advantages of TMB compared to conventional method is that these machines can be used in several geological conditions. In the recent years, The Earth Pressure Balance (EPB) shield method was successfully used in urban areas and its application is developed. One of the decisive issues for successful EPB tunneling using conditioning agent is the wear estimation and the assessment of the effects of abrasive ground on the costs and schedule of a project. The estimation of primary wear as well as secondary wear is important for performing a successful project. Among the parameters that can be affected on wear, the soil conditioning is very important. Soil conditioning has been increasingly used to improve the performance of tunnelling process adding foaming agent. It can reduce the wear of machine cutter head face plate and tools, and all wear parts of the muck removal system. In order to assess the impact of the soil conditioning on tool wear, this paper introduces a new test apparatus with new propeller built to measure soil abrasion. Moreover, a specific test procedure has been designed and several sets of tests was conducted in the "Tunnelling and Underground Space Center" of Polytechnic university of Turin, in collaboration with UTT Mapei S.P.A. The primary examination shows that utilizing soil conditioning can reduce the wear of tool. More tests are underway to evaluate the effect of soil conditioning as well as other parameters on wear tool that lead to introduce the model and index for predicting the wear in soft ground tunnelling.