Subway subgrades typically consist of alternating deposits of soil layers with significantly different physical and mechanical properties. However, the overall dynamic characteristics and the evolution of micro-porous structures in stratified soils is often overlooked in current studies. In this study, cyclic triaxial tests were conducted on homogeneous sand, silt and stratified soils with different height ratios, and nuclear magnetic resonance (NMR) was used to investigate the changes in pore structure and moisture content. The dynamic behavior and macroscopic deformation mechanisms were systematically investigated in terms of stress amplitude, confining pressure, and layer height ratio (the ratio of sand to silt height). The results show that as the sand height ratio increases, the axial strain and pore water pressure first increase and then decrease, reaching the maximum when h(Sand): h(Silt) = 2:1. When the confining pressure is 100 kPa, the axial strain of h(Sand): h(Silt) = 2:1 is 181.08 % higher than that of silt. Under the dynamic loading, the stratified soils form a dense skeletal structure near the stratification plane, which hinders the flow and dissipation of pore water, so that the pore water agglomeration phenomenon occurs near the stratification plane, which aggravates the accumulation of residual pore pressure and reduces the deformation resistance. However, when h(Sand): h(Silt) = 4:1, the influence of the stratification planes is significantly reduced, and the deformation characteristics approach homogeneity. This study reveals the dynamic characteristics of stratified soils by comparing and analysing homogeneous samples.

Management of agricultural soils for increased productivity may exert positive or negative effects on soil structure, functions, and organic carbon (SOC) stocks. In this study, a field experiment established in 1993 on a clayey soil in southwest Finland was revisited to investigate the long-term effects of deep ploughing and liming on SOC concentration and stock, particulate (POC) and mineral-associated (MOC) fractions of SOC, pH, electrical conductivity (EC), bulk density (BD), porosity, critical pore size and cereal yield. The experiment comprised whole plots of conventional tillage (CT) to a maximum depth of ca. 20 cm, and plots deep ploughed to ca. 35 cm depth by a commercial (DP1) or by a self-made (DP2) plough. The tillage plots were divided into three split-plots assigned to liming treatments (low, medium and high). Three decades after implementation, the increasing liming rates still induced consistent differences in soil pH, a significant increasing effect on total porosity in the subsoil, and a marginally significant decrease in yield with an increase in soil acidity. The deep ploughing exerted a minor difference in topsoil texture, slightly lowered SOC concentration in the topsoil in DP2 in comparison to CT, and slightly higher subsoil SOC concentration in DP1 in comparison to CT, which indicated transfer of the topsoil SOC to deeper layers and dilution of the SOC in the new topsoil. However, no significant differences between the tillage treatments occurred in SOC stocks. In MOC and POC concentrations, there were no significant differences between the control and tillage treatments. The effects of deep ploughing on soil structural properties on the decadal time scale were minor and scattered. Cereal yield exhibited a slight negative trend for deep ploughing. For EC and BD, no treatment effects were recorded. Overall, the study showed that the legacy of soil management effects on soil properties can be persistent on decadal time scales, but no permanent structural damage due to deep ploughing nor gains in SOC stock accrual could be observed.

Vertical stratification of forest plays important roles in the local material balance and in maintaining forest health by distributing and redistributing precipitation materials through adsorption, fixation, and release. Differences in runoff nutrient concentrations among vertical layers are closely related to vertical stratification (factors such as the trunk, canopy, forest litter, and soil physical and chemical properties). Long-term forest observations revealed significant spatial differences in Pinus massoniana (Pinus massoniana Lamb.) forests in the Three Gorges Reservoir area. Pinus massoniana forests on downslopes were characterized by a dense canopy, green needles, and rich forest vegetation, while those on upslopes were characterized by low vegetation cover, dead trees, and decreases in the tree height, diameter at breast height, and volume per plant with increasing slope. By analyzing the soil at different sites, we found that the pH of the forest land soil differed significantly among different slope positions. Soil on upper slopes was significantly more acidic than soil on lower slopes, indicating that acidic substances were intercepted by filtration through the broad litter layer and the soil surface layer. This filtration process resulted in a normal rhizosphere environment suitable for the absorption of nutrients by vegetation on the lower slopes. In this way, downhill sites provided a good microenvironment for the growth of Pinus massoniana and other vegetation. Our results show that direct contact between needles and acid rain was not the main cause of root death. Instead, the redistribution of rainfall substances by forest spatial stratification caused changes in the soil microenvironment, which inhibited the absorption of nutrients by the roots of Pinus massoniana and the growth of understory plants in Pinus massoniana forests on upper slopes. These findings emphasize that increasing land cover with forests with vertical structural stratification plays an important role in woodland material redistribution and forest conservation.

Tunnelling induces stress change and displacement in the ground. The excavation of a new tunnel in stratified soil can trigger different patterns of stress redistribution, which may adversely influence nearby tunnels. Research on multi-tunnel interaction has mainly been performed on the assumption of a uniform ground. The effects of different soil stratifications on tunnelling interaction remain poorly understood. In this paper, threedimensional numerical parametric studies verified by previous centrifuge tests were carried out to analyse the twin tunnelling effects in two-layered soil. An advanced hypoplastic constitutive model that can capture stress-, path-, and strain-dependency of soil behaviour is adopted. Numerical cases investigated include perpendicular twin tunnelling in two sand layers with different relative densities and the location of the interface between the two sand layers. It is revealed that larger settlements and a wider surface settlement trough occur when tunnelling in two-layered soil strata than in a uniform ground. This is because of the wider and larger soil arch induced in two-layered soil strata. The structural response including tunnel deformation, induced bending moment, and induced hoop stress of the existing tunnel can be greater when tunnelling in layered soil strata than in a uniform ground owing to larger stress relief. Moreover, the combination of bending moment and hoop stress can exceed the M-N failure envelope of the structure in layered soil. A conventional simplified assumption of a uniform ground can underestimate of the influence of new tunnel excavation on existing tunnels, resulting in unsafe designs.