Experimental and laboratory assessment of clogging potential based on adhesion

Abstract

Mechanized tunneling through clayey formations is threatened by encountering the clogging problem. Adhesion stress, as the tendency between clay and a metal surface, leads to clogging between TBM and excavated materials. Some empirical clogging classification charts were prepared based on the experienced clogging problems. Moreover, experimental attempts have been made to evaluate clogging potential. The relation between available empirical charts with laboratory measurements has not been fully defined. This research was conducted to clarify the relationship between measured adhesion values and to propose empirical charts to support a laboratory assessment method. In this regard, 35 clayey soil samples (assumed to have different levels of clogging potential) were selected using the main existing empirical evaluation charts. The clayey soil samples were tested at two different consistency indexes using the piston pullout test, as a highly qualified adhesion assessment tool. The performance of available classifications was examined by laboratory test results. For this purpose, distribution of the measured adhesion values and levels of clogging potential with classification charts were compared. Among the examined classification charts, one of them showed a high match with adhesion values. Using the resulting relationship, a new experimental method was proposed to evaluate clogging potential using laboratory data.