ANALYSIS OF NATM TUNNEL RESPONSES IN QUATERNARY UNCONSOLIDATED COHESIVE SOIL

Abstract

  There have been only a limited number of attempts to construct a tunnel by the NATM through unconsolidated cohesive soil of the middle Pleistocene and younger geologic ages because of difficult in ensuring the self-standing ability of the ground. As a result, the responses of this type of ground are not yet well known. Because the NATM allows modification of the support structure in accordance with the observed ground state and selection of construction techniques that suit the ground characteristics, extending the applicability of the NATM to wider ground types is desired. Bearing this in mind, this study summarizes the physical and engineering characteristics of unconsolidated cohesive soil, analyzes ground displacement responses during NATM tunneling, and investigates ground deformation properties that are key to numerical analysis.