Influence of water and sand content on adhesion of clayey soils

Abstract

Clogging occurs during mechanical tunneling with a Tunnel Boring Machine (TBM) because of adhesion of clayey soils to the cutter<br />head and conveyor system. The present study examined the effects of water and sand contents on clogging in Montmorillonite clayey<br />soil. Testing was carried out using an adhesion test device on 28 samples with different water and sand contents to determine adhesion<br />stress and degree of clogging. The results indicate that the consistency index (Ic) of the samples decreases as the sand and water<br />content increases. The results for variation of adhesion stress versus water content at different sand contents formed similar bellshaped<br />curves. In all graphs, an increase in sand content decreased adhesion stress. Adhesion stress increased until the water content<br />increased to 138%, at which point it began to decrease. The results show that adhesion of the soil to the surface of the metal piston did<br />not occur in samples having a sand content of >40% and in samples with >133% water content having a sand content of <40%, Ic>0.5<br />adhesion occurred.