Pit excavation could inevitably introduce ground movement and threaten the safety of nearby existing high buildings, metro tunnels, or roads. To reduce ground movement and protect those existing structures against large deformation, isolation pile is widely used in engineering practices. A series of physical model tests was carried out to investigate the effects of isolation piles on the ground deformation induced by excavating a pit. Digital image correlation (DIC) analysis was employed to study the ground deformation and slip surface under different pile lengths and locations relative to the retaining wall. The results indicate that the ground deformation and the shear band in the ground are less affected by the existence of a pile if the isolation pile’s end is above or slightly extends beyond the slip surface. In contrast, if the isolation pile extends beyond the slip surface sufficiently, even though the ground movement behind the pile is reduced, the settlement of the soil between the pile and retaining wall would be enlarged. Meanwhile, the horizontal deformation shows an arching shape along the depths and has a noticeable value in the middle section of subsoil. The ground deformation behind the isolation pile shows dependence on the pile’s horizontal displacement, regardless of the pile’s length and location. An empirical model is proposed to evaluate the efficiency of isolation piles on settlement protection. The comparison of the prediction and the results from tests and FEA shows a reasonable agreement.

In offshore engineering, the sand beneath an embankment may be subjected to traffic loads, resulting in a series of engineering issues. The behaviour of the sand beneath the embankment may change under a long-term traffic load. A series of drained cyclic and post-cyclic monotonic triaxial tests were performed on Fujian sand with different relative densities. The drained strength and stress–dilatancy behaviours were studied. The results indicated that the normalised peak strength ratio after cyclic loading was greater than that without cyclic loading, depending on the cyclic stress amplitude, while the critical state strength seemed to be only slightly affected by the cyclic loading history. The dilative response of sand could also be influenced by cyclic loading-induced fabric. Under constant relative density conditions, the higher the cyclic stress amplitude applied to the sand sample, the larger the volume strain produced in the critical state. Furthermore, cyclic-induced fabric could be destroyed after 6% axial strain.

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Grid direction selection and grid size design are two important elements that need to be considered in the grid direction design in reservoir numerical simulation. Reservoir engineers normally utilize geological data (such as the distribution of fractures, low permeability zones, faults and major stress) and simulation experiences to design the grid direction of simulation model qualitatively. The research of the paper indicates that the key to determine the grid direction is to determine the principal permeability direction. Under the circumstances of few static materials, a new grid direction determination method has been developed by using field data (well location map and inter-well permeability) on the bases of Darcy's law and tensor analysis theory. The grid direction of WZ11-7 Oilfield simulation model has been determined using four production wells and two production zones (L 1 and L 3) in WZ11-7-2 well group, the results are in conformity with the geological studied major stress. Therefore, this method can give insights into the numerical simulation study.

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