Induced Trench Installation (ITI) is a viable option to reduce the load on rigid culverts buried under high embankments. However, reliable design methods are limited, which restricts further applications of this technology. Based on Marston's formula, a modified analytical solution is proposed, in which the vertical stress across the width of the soil column immediately above the compressible layer is assumed to be distributed in a parabolic shape, and the effects of the geometry and stiffness of the soft layer on load reduction are considered explicitly. Comprehensive comparisons are made between field monitored results and the calculations from different design methods. Parametric studies are subsequently conducted to investigate the influence of different distribution patterns of vertical stress and the properties of the soft layer. It is found that compared to Marston's theory, the proposed method yields a closer estimation to the field measured data. Finally, a simplified design chart is introduced, which can facilitate use of the proposed method.

The response of unsaturated soil slopes subjected to raised groundwater levels is generally governed by undrained shear strength. A series of unconsolidated undrained triaxial tests was conducted on reconstructed specimens of Xiashu loess with different water content. This can avoid the complexity involved with the measurement of matric suction. The Duncan-Chang hyperbolic model was modified to approximate the measured stress-strain responses. A correlation between water content and shear-strength parameters was established. The proposed model was then implemented in a finite-difference analysis program, against which two conventional calculations using the standard Mohr-Coulomb model with constant and varying soil properties with depth were compared. The analyses of an unsaturated soil slope subjected to raised groundwater levels demonstrate that soil properties should vary with water content; otherwise, an unsafe evaluation of slope stability will be obtained because the displacements of the slope may be underestimated if the dependency of water content is neglected.

The performance of a 56 m deep circular excavation supported by a double-wall system, consisting of an inner circular diaphragm wall and an outer rectangular cut-off wall, in Shanghai soft ground is studied in this paper. The surveyed data (e.g., lateral wall deflections ( δ _h), horizontal displacement of soil ( δ _s), ground surface settlement ( δ _v), soil rebound ( δ _v+), earth pressure ( P), pore water pressure ( P_w), and soil stress path) are systematically investigated. The results show that the maximum lateral wall deflections are 0.002% ∼ 0.03% of the excavation depth ( H _e). The maximum ground surface settlement ( δ _{v m}) is generally larger than δ _{h m}, which is located at 0.4 ∼ 0.6 H _e. Moreover, an innovative formula is proposed to estimate the ground settlement. It is able to distinguish various characteristics of surface settlement in different zones of the settlement profile. The ground surface settlements are mainly induced by surcharge loading and continuous excavation, and they are related to the change in confined water level. The lateral earth and pore water pressures in the active zone are relatively insensitive to the excavation, while the correlation becomes obvious in the passive zone. The findings from this study can be helpful to the design of other similar deep excavations in soft clay.