Active failure characteristics and earth pressure distribution around deep buried shield tunnel in dry sand stratum

Abstract

The stability of the tunnel face is a key issue in shield tunnel engineering. In this paper, a series of 1 g model tests were conducted in dry sand for various buried depth ratios H/D = 2, 3, 4, 5, and 6 to study the failure characteristics, earth pressure distribution and the soil arching effect. Each test provided a measurement of the earth pressure with the face withdrawal displacement. And the soil deformation and the failure characteristics were investigated by Particle Image Velocimetry (PIV) system. The development of the failure characteristics was discussed for the buried depth ratios H/D = 3. The relationships between the failure characteristic and buried depth ratios were investigated. The variation of limit support pressure, soil stress distribution at different depths and earth pressure around the tunnel are analyzed. The soil arching effect around the tunnel at deep burial conditions is revealed. With the withdrawal displacement increasing, the tunnel face is in close contact with the support panel at first, and then gradually separated from the support panel. The larger the H/D is, the smaller the increment of horizontal soil stress is. It could be concluded that the increase of tunnel depth directly leads to the soil arching effect.