Development of a three-dimensional staged volume loss tunnelling method in the centrifuge

Abstract

Conventional assessment of tunnelling-induced settlement focuses primarily on transverse profiles given the transitional nature of the longitudinal settlement profile. This approach thus relies on the commonly made assumption that the trough width parameter is constant for both directions (longitudinally and transversely). The commonly used single-stage fluid extraction method of volume loss modelling in the centrifuge, restricts the tunnelling behaviour to a plane strain problem, prohibiting any investigation into the longitudinal settlement profile. A staged volume loss tunnelling method along with a new centrifuge package was designed and built to simulate the three-dimensional construction of a model tunnel, equivalent to 6·2 m dia. tunnel in prototype, across five advancements in Speswhite kaolin clay. Using the geotechnical centrifuge at Cambridge University, this model enabled multiple runs of tunnelling construction to be simulated within one flight at different volume losses, operating at 100g. This new innovative tunnelling method in the centrifuge has allowed a distinct difference between the trough longitudinal and transverse width parameters to be observed and studied at various volume loss values.