ABSTRACT
Adequate parameters of the support medium in earth pressure balance (EPB) tunnelling are important for the effectiveness of face support pressure, and therefore for safety and tunnelling performance. Moreover, the aspect of the re-usability of excavated material is becoming increasingly important in the context of the resource-efficient circular economy, which becomes more effective with fewer soil conditioning agents used. Such additives are dosed manually, estimated on the basis of subsoil-specific machine parameters as well as on the visual impression of the excavated material in terms of homogeneity and workability on the conveyor belt. In order to provide automated and economically optimised dosage of the conditioning agent, an integrated control circuit is required.
A corresponding measuring system that can effectively conclude geotechnical (index) properties of mixed-grained soils in real time was developed and tested for the first time on an earth pressure balance tunnel boring machine (EPB-TBM). This involves on the one hand a thread pendulum with a steel ball, that moves over the surface of the excavated material on the conveyor belt. On the other hand, a plough is used, which dips into the mass flow of excavated material on the conveyor belt. Depending on soil’s consistency/workability, grain and chip size and other aspects the steel ball and plough measuring devices receive impacts and deflections, which are registered by force sensors. Utilising artificial intelligence methods, it is possible to find correlations between the measured values and key geotechnical (index-) parameters such as slump value and shear strength.
