The use of weathered phyllite waste slags generated from the excavation of cuttings and tunnels as roadbed filler material can effectively address issues related to filler scarcity, environmental protection, and cost. This study focused on weathered phyllite obtained from a highway expansion project in the Longnan Area of Gansu Province, China. Various experiments were conducted in a laboratory setting, including compaction, unconfined compressive strength (UCS), California bearing ratio (CBR), permeability, and disintegration tests, to investigate the response of mixtures with different gravel contents (GCs), ranging between 30 %-70 % by weight of weathered phyllite filler (WPF). The test results indicate the presence of a critical GC threshold. At 55 % GC, the WPF exhibits optimal compaction, the highest UCS and CBR values, and the lowest permeability and disintegration rates. Upon reaching this critical GC threshold, the phyllite gravels contact each other to form a skeletal structure, while fine grains fill the gaps within this structure to create a denser skeleton configuration. Coarse phyllite gravels are more prone to fragmentation into finer grains, which can effectively occupy large, medium, and small voids between particles. Consequently, the WPF exhibits enhanced structural density and improved mechanical and hydraulic properties. These findings provide a theoretical reference for the engineering application of phyllite in mountainous projects.

At least 32 case histories have shown that liquefaction can occur in gravelly soils (both natural deposits and manmade reclamations) during severe earthquakes, causing large ground deformations and severe damage to civil infrastructures. Gravelly soils, however, pose major challenges in geotechnical earthquake engineering in terms of assessing their deformation characteristics and potential for liquefaction. In this study, aimed at providing valuable insights into this important topic, a series of isotropically consolidated undrained cyclic triaxial tests were carried out on selected sand-gravel mixtures (SGMs) with varying degrees of gravel content (Gc) and relative density (Dr). The pore water pressure generation and liquefaction resistance were examined and then further scrutinized using an energy-based method (EBM) for liquefaction assessment. It is shown that the rate of pore water pressure development is influenced by the cyclic resistance ratio (CSR), Gc and Dr of SGMs. However, a unique correlation exists between the pore water pressure ratio and cumulative normalized dissipated energy during liquefaction. Furthermore, the cumulative normalized energy is a promising parameter to describe the cyclic resistance ratio (CRR) of gravelly soils at various post-liquefaction axial strain levels, considering the combined effects of Gc and Dr on the liquefaction resistance.

Due to climate change, human activities and natural disturbances in high-latitude permafrost and seasonally frozen areas are gradually increasing, attracting more attention from scholars. However, research primarily focuses on soil biology and chemistry in these regions, with limited exploration of their mechanical properties, especially compression properties. This study aims to evaluate the effects of gravel content and freeze-thaw (F-T) cycles on the compression properties of coarse-grained layered forest soil from northeast China's seasonally frozen regions, with the goal of predicting the soil's compressive changes under heavy mechanical loads. Specifically, using uniaxial confined compression tests (UCCT) on 252 disturbed soil samples (including two soil layers: AB and Bhs; hs ; six gravel contents; and seven F-T cycles), three characteristic compression coefficients-precompression stress (6pc), compression index (Cc),and swelling index (Cs)-were s )-were measured. Additionally, scanning electron microscopy (SEM) was used to analyze the mesostructure evolution of coarse-grained gravel-bearing soil. Volume changes of samples were measured after 15F-T cycles with varying gravel contents. Results indicate non-linear effects of gravel content and F-T cycles on 6pc. pc . Gravel content below 50% positively influences 6 pc , while content above 50% increases soil pore content, decreasing 6 pc . Cc c and Cs s exhibit an approximately negative correlation with gravel content and initially increase followed by a decrease with more F-T cycles. Moreover, the 6pcand pc and Ccof c of the AB layer are higher than those in the B hs layer, likely due to differences in clay and organic carbon contents. Notably, the observed trends differ from previous studies on other soil types such as farmland and paddy fields. This study fills a gap in understanding the compression characteristics of layered gravel-bearing forest soil in seasonally frozen regions, providing valuable insights for evaluating soil compression in both seasonally frozen and permafrost regions, and understanding mechanical vehicle- soil interactions. It also lays the theoretical groundwork and provides data support for constructing compression models of layered gravel-bearing forest soil.

Case histories from at least 28 earthquakes worldwide have indicated that liquefaction can occur in gravelly soils (both in natural deposits and manmade reclamations), inducing large ground deformation and causing severe damage to civil infrastructures. However, the evaluation of the liquefaction potential and cyclic strain accumulation characteristics of gravelly soils remains a major challenge in geotechnical earthquake engineering. To provide new and useful insights into this crucial topic, stress -controlled undrained cyclic triaxial tests were conducted on sand -gravel mixtures (SGM) having sand -dominated microstructure but different packing states (i.e., soil grain arrangement), which were obtained by varying the gravel content (GC) and relative density (Dr). The experimental results confirmed that both the GC and Dr have marginal (at low GC and Dr) to significant (at high GC and Dr) effects on the cyclic resistance ratio (CRR) of SGM, but highlighted the need to consider GC and Dr effects together. In this regard, the use of state parameters, such as the equivalent void ratio (ef(eq)) and equivalent relative density (Drf(eq)), were found to be suitable approaches to describe the combined effect of GC and Dr on CRR as they provide unique correlations for sand -dominated SGM irrespective of their packing states. (c) 2024 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).