Early earthquakes often trigger landfill slope failures and damage to cover and liner systems, resulting in gas leakage, environmental contamination, and significant risks to landfill safety. Accurately assessing the static and dynamic characteristics of mechanically biologically treated (MBT) waste is crucial. Centrifuge shaking table tests offer a robust method to address the limitations of conventional shaking table tests by effectively simulating the static and dynamic stress-strain fields of prototype soils, fulfilling the requirements for comprehensive static and dynamic analysis. Accordingly, this study conducted experimental research on MBT waste using a centrifuge shaking table. Key findings are as follows: (1) The Poisson's ratio of MBT waste is 0.483, and its small-strain shear modulus increases with depth, with a derived equation representing the relationship between small- strain shear modulus and depth. (2) MBT waste demonstrated a significant dynamic amplification effect, with an amplification factor ranging from 1.122 to 1.332. (3) The equivalent shear modulus of MBT waste decreases with increasing strain but increases with depth, with a surface equation established between the equivalent shear modulus, strain, and depth. (4) The equivalent damping ratio of MBT waste varies with strain and depth, and a surface equation was established to capture this relationship. (5) A comparison of the normalized equivalent shear modulus and equivalent damping ratio between MBT waste and municipal solid waste (MSW) shows that both parameters are higher in MBT waste than in MSW. These findings provide valuable insights for seismic stability analysis of MBT landfills.

Small strain properties of subgrade fill material are essentially required for the accurate estimation of deformation behavior of railway subgrade. Many attentions have received on small strain properties of soils under the isotropic stress state or low shear stress level. The high level of shear stress and stress ratio induce reduction in small strain stiffness and thus present the potential challenge to the deformation stability of the subgrade. However, there is not much attempt to investigate the small strain properties under high stress ratio. This paper explores the effects of stress path and stress state on small strain stiffness Gmax and Poisson's ratio v of heavily compacted fully weathered red mudstone (FWRM) under a broad range of stress ratio, via a series of stress-controlled triaxial and bender element tests. Three stress paths, named as constant stress ratio (SSP), constant confined pressure (VSP), constant axial stress (HSP) with stress ratio up to 33.0 were considered. Low level of shear stress slightly promotes Gmax, while a significant reduction of Gmax is triggered as the stress ratio exceeds a critical value. A unified correlation between the critical stress ratio and confined pressure is developed. The evolution of Poisson's ratio is also described by a unified three-dimensional feature surface, which influence of stress path is identified by the location and shape of the surface.

The shallow seismic methods, including seismic refraction and 1D MASW, were used to investigate the shallow soil in the vicinity of five damaged building blocks in the village of El-Kalaheen. These building blocks exhibited structural problems including cracks, fissures and displacements between neighboring buildings. The results of both methods show that the shallow subsurface consists of two layers: a surface layer of loose sands, gravels, silts and clays and a compacted sandy clay layer that forms the bedrock in the area. The resulting seismic velocities were used to calculate the geotechnical parameters of the two layers, including Poisson's ratio, shear modulus, Young's modulus, material index and N-value. In addition, the shear wave velocities resulting from the 1D MASW method were used to calculate the average Vs30 in the site. The calculated values of the geotechnical parameters show a gradual increase in the competence of the upper layer from fairly competent and loose in the south of the area to competent and denser in the north. The geotechnical parameters of the bedrock also show an increase from moderately competent in the south to denser and more competent in the north. Possible zones of weakness are also observed in the southern part of the site. The calculated Vs30 indicates a site with stiff soil classification.