Lateral earth pressure of granular backfills on retaining walls with expanded polystyrene geofoam inclusions under limited surcharge loading

Existing studies have focused on the behavior of the retaining wall equipped with expanded polystyrene(EPS)geofoam inclusions under semi-infinite surcharge loading rather than limited surcharge loading.In this paper,the failure mode and the earth pressure acting on the rigid retaining wall with EPS geofoam inclusions and granular backfills(henceforth referred to as EPS-wall),under limited surcharge loading are investigated through two-and three-dimensional model tests.The testing results show that different from the sliding of almost all the backfill in the EPS-wall under semi-infinite surcharge loading,only an approximately triangular backfill slides in the wall under limited surcharge loading.The distribution of the lateral earth pressure on the EPS-wall under limited surcharge loading is non-linear,and the distribution changes from the increase of the wall depth to the decrease with the increase of the limited surcharge loading.An approach based on the force equilibrium of a differential element is developed to predict the lateral earth pressure behind the EPS-wall subjected to limited surcharge loading,and its performance was fully validated by the three-dimensional model tests.

At-rest lateral earth pressure of compacted expansive soils:Experimental investigations and prediction approach

This paper presents experimental studies on a compacted expansive soil,from Nanyang,China for investigating the at-rest lateral earth pressureσL of expansive soils.The key studies include(i)relationships between theσL and the vertical stressσV during soaking and consolidation,(ii)the influences of initial dry densityρd0 and moisture content w 0 on the vertical and lateral swelling pressures at no swelling strain(i.e.σV0 andσL0),and(iii)evolution of theσL during five long-term wetting-drying cycles.Experimental results demonstrated that the post-soakingσL-σV relationships are piecewise linear and their slopes in the passive state(σL>σV)and active state(σL<σV)are similar to that of the consolidationσL-σV relationships in the normal-and over-consolidated states,respectively.The soakingσL-σV relationships converge to the consolidationσL-σV relationships at a thresholdσV where the interparticle swelling is restrained.TheσL0 andσV0 increase monotonically withρd0;however,they show increasing-then-decreasing trends with the w 0.The extent of compaction-induced swelling anisotropy,which is evaluated byσL0/σV0,reduces with an increase in the compaction energy and molding water content.TheσL reduces over moisture cycles and the stress relaxation in theσL during soaking is observed.An approach was developed to predict the at-rest soakingσL-σV relationships,which requires conventional consolidation and shear strength properties and one measurement of theσL-σV relationships during soaking.The proposed approach was validated using the results of three different expansive soils available in the literature.

Structural,volumetric and water retention behaviors of a compacted clay upon saline intrusion and freeze-thaw cycles

This study investigates the evolution of the structural,volumetric and water retention behaviors of a compacted clay during soaking and desiccation considering the influences of freeze-thaw(FT)cycles and saline intrusion.Compacted specimens were subjected to different FT cycles and then submerged in NaCl solution with different concentrations to facilitate the saline intrusion and measure the swelling behaviors.Shrinkage curve and filter paper tests were thereafter performed to reveal the clay’s volumetric and water-retention characteristics during desiccation.Mercury intrusion porosimetry and field emission scanning electron microscopy tests were conducted to observe the evolution of the clay’s microstructure.Experimental results show that the clay’s micropores decrease and macropores increase after FT cycles,which is associated with the migration of water,growth of ice crystals,and development of FT-induced cracks during FT cycles.Similar observations were obtained from specimens after the saline intrusion,which is attributed to the osmotic and osmotically-induced consolidation.FT-induced cracks significantly reduce the clay’s swelling and shrinkage potentials.FT cycles result in the shrinkage of micropores which leads to a reduction in the water retention capacity in the low suction range(capillary regime).The salinization suppresses the swelling of the clay and prolongs its primary and secondary swelling stages.The shrinkage potential initially increases and then decreases with increasing saline concentration.Salinization has significant influences on the osmotic suction and thus alters the clay’s water-retention curves in terms of total suction.It demonstrates little impact on the clay’s water-retention curves in terms of matric suction.