Field tests and researches on secondary stresses of advanced tunnel segments during parallel shield tunnels driving in close proximity

The change rules of the secondary stresses of advanced tunnel segment induced by parallel shield tunnels dirving in close proximity are studied by field tests. The layout of the measured points and the field test methods are introduced, and the change rules of the secondary stresses are analyzed. Furthermore, the relationship between the secondary stresses and the distance of the shield driving face to the measured section are studied. Statistical analyses of the maximum and the stabilized magnitudes of the secondary stresses are carried out. The results of the field tests show that there will be sharp change of the secondary stresses when the hind shield is driven to the measured section, the circumferential secondary stresses in the intersection of horizontal diameter with circumference of the tunnel will be laid, and the magnitudes of the circumferential secondary stresses will be greater than those of the longitudinal secondary stresses. The results may be applied to the quantitative assessment of the construction interaction of shield tunnels in close proximity and is regarded as references to the design and construction of this kind of shield tunnels.