Investigation on the seismic response of geogrid reinforced soil walls backfilled with cement-fiber-treated soil through 1-g shaking table tests

Improving the characteristics of local low-strength soils at the construction site is one of the appropriate approaches to employ the soils as a backfill of geogrid reinforced soil (GRS) walls. In this study, the fiber-cement-treated sand-silt mixture was used as the backfill of walls. The post-earthquake performance of the walls was evaluated by applying the sinusoidal waves on 1-m high reduced-scale physical models and conducting a series of 1-g shaking table tests. A comparison of the wall models constructed with treated and untreated backfill indicated the advantages of geogrid-reinforced fiber-cement-treated soil walls subjected to strong ground motion. The results revealed the better behavior of the wall models backfilled with treated soil mixtures under dynamic loading. Such improved performance was more evident in (1) deformation responses, including the lateral displacement of wall facing, deformation mode, failure surfaces, and settlement of backfill surface and (2) acceleration response in different locations, including facing, reinforced, and retained zone of walls.

Vacuum-induced lateral deformation around a vertical drain in dredged slurry

The horizontal strain in the vacuum preloading/dewatering of dredged slurry is significant to the apparent clogging effect and estimation of surface settlement around a drain; however, it has seldom been investigated in previous studies. In this study, a vacuum consolidation model test assisted with the particle image velocimetry (PIV) technology was conducted. The displacement vector field was obtained through PIV analysis and image processing; it was used to visually observe the deformation features around a drain. Based on the displacement field, the vertical/horizontal strains at varied radial distances were calculated to explain the “soil pile” and apparent clogging effect. From the strain distribution with radial distances, a significant lateral compression zone near the drain and an extension zone at farther areas were confirmed. Furthermore, a simple explicit model was established to evaluate the horizontal strain within a prefabricated vertical drain unit cell considering a horizontal attenuated vacuum and compression/extension zone. Finally, this method was applied to predict the horizontal displacement in the model test. The results showed that the proposed method can estimate the lateral displacement of soft clay slurry fairly well.

Experimental evaluation of salinity geosynthetics capillary barriers

This paper explores the transient upward flow of saline water in one-dimensional soil and soil-geosynthetics columns to evaluate preventive measures to mitigate salinity rise. Unsaturated soil concepts are utilised to elucidate the salinity movement through geotextile and geocomposite drain interfaces. The presence of a geotextile layer slowed down the capillary rise of the saline water. However, it did not prevent the breakthrough of the saline water due to the hydrophilicity of the geotextile and the suction at the geotextile base being close to the geotextile's water entry suction value. In contrast, using a geocomposite drain mitigated the upward saline wetting front. It acted as a salinity capillary barrier due to the initial hydrophobicity of its geotextile component and the air gap present in the geonet core.