Cement mixing techniques are widely used to improve the mechanical properties of weak soils in geotechnical engineering. However, due to the influence of various factors such as material properties, mixing conditions, and curing conditions, cement-mixed soil exhibits pronounced spatial variability which is greater than that of natural soil deposits, introducing additional uncertainty into the measurement and evaluation of its unconfined compressive strength. The purpose of this study is to propose a novel framework that integrates image analysis with Bayesian approach to evaluate the unconfined compressive strength of cement-mixed soil. A portable scanner is used to capture high-quality digital images of cement-mixed soil specimens. Mixing Index (MI) is defined to effectively evaluate mixing quality of specimens. An equation describing the relationship between water cement ratio (W/C) and unconfined compressive strength (qu) is introduced to estimate the strength of uniform specimens. To estimate the strength of non-uniform specimens, the equation is developed by integrating MI with the strength of uniform specimens. The coefficients of equations are obtained using Bayesian approach and Markov Chain Monte Carlo (MCMC) method, which effectively estimating the strength of both uniform and non-uniform specimens, with coefficients of determination (R2) of 0.9858 and 0.8745, respectively. For each specimen, a distribution of estimated strength can be obtained rather than a single fixed estimate, providing a more comprehensive understanding of the variability in strength. Bayesian approach robustly quantifies uncertainties, while image analysis serves as a convenient and non-destructive method for strength evaluation, providing accurate method for optimizing the mechanical properties of cement-mixed soil.

In order to investigate the impact of plant root systems on the stability of loess shallow slope, this study conducted plant morphology investigations and direct soil shear tests to analyse the morphological characteristics of alfalfa and the shear characteristics of alfalfa root-loess composites under different soil bulk densities and soil moisture saturation levels. Additionally, the reinforcing effect of the alfalfa root system on the reliability of loess slopes was assessed using the Monte Carlo method. Slope reliability analysis refers to the estimation of the probability of slope failure under specific conditions. The results showed that plant weight and root weight both decreased following an exponential function with increasing soil bulk density. Root weight had a positively linear correlation with plant weight. The cohesion and internal friction angle of both loess samples without roots and with roots increased with increasing soil bulk density. The cohesion and internal friction angle of the two kinds of samples could decreased at less and more than 30% soil moisture saturation. The cohesion and internal friction angle of the root-soil composites were significantly higher than those of the rootless soil. The decrease of soil bulk density and the increase of soil moisture could increase the difference of the two mechanical parameters between the two kinds of samples. Assuming the thickness of the landslide body was 0.3 m, the failure probability of loess slopes covered with alfalfa significantly decreased from 34.97 to 14.51% compared to slopes without vegetation cover. Alfalfa roots significantly increased the reliability of the loess slopes in stability.

On 18 December 2023, a Ms 6.2 earthquake struck the Jishishan area in Northwest China, located at the border of the Qinghai-Tibet and Loess Plateau. The earthquake triggered shallow loess landslides, small rock failures, and soil cracks, mainly along hilly gullies and cut slopes at the edges of terraced fields. A rare large-scale flowslide also occurred in irrigated farmland. These seismic landslides and collapses blocked roads, buried farmland, damaged houses, and resulted in many casualties. Field investigations revealed that these geological hazards were concentrated around cultivated land. Consequently, cultivated land was introduced as an engineering geological zoning factor into the seismic geological hazard risk assessment for Jishishan area. The Newmark cumulative displacement model was refined by incorporating lithological uncertainties via the Monte Carlo method. Comparative analysis of coseismic geohazards with and without considering cultivated land suggests that, in loess-covered areas with cultivation activities, the consideration of the disturbed characteristics of soils provides a more accurate probabilistic risk assessment of seismic geohazards. Human cultivation and irrigation activities affect the physical properties of surface soil, the terraced fields around earthquake prone areas have a risk of earthquake-induced geological hazards. This study may offer valuable insights for hazard prevention and mitigation in high fortification intensity loess covered areas.

Pitting corrosion is normally distributed randomly along the pipeline, which is the source of the uncertainty affecting the ultimate bearing capacity of the submarine pipelines. So the Monte Carlo method is employed to study the effect of pitting corrosion on the upheaval buckling behavior of the pipeline. A corroded pipeline model with randomly distributed pitting corrosion is utilized to captures the intricate realities of corrosion scenarios. Multiple corrosion models with distinct artificial patterns have been meticulously crafted. Additionally, a new pipeline element based on Euler-Bernoulli beam theory is extended considering corroded sections, pipe -soil interactions, axial load, initial imperfections, and other major factors. Moreover, the bearing capacity, vertical deformation and stress of the pipeline under corrosion is discussed thoroughly, wherein a Newton- Raphson typed numerical analysis procedure is utilized for nonlinear analysis of the upheaval buckling of pipelines. The influence of corrosion parameters such as the corrosion depth, corrosion ratio and area loss ratio on mechanical properties of the submarine pipelines is further analyzed in detail. It's indicated that varying patterns of corrosion distribution, despite exhibiting identical corrosion parameters, can result in distinct reduction factors and vertical buckling displacements. Copyright (c) 2024 by The Hong Kong Institute of Steel Construction. All rights reserved.