Seismic safety of high concrete face rockfill dams (CFRD) on thick layered deposit is crucial. This study develops a seismic performance assessment procedure for high CFRD on thick layered deposit considering multiple engineering demand parameters (EDPs), and evaluates the effectiveness of gravel column and berm reinforcement for a typical CFRD. Solid-fluid coupled seismic response analysis of high CFRD on thick layered deposit is conducted using an advanced elasto-plastic constitutive model for soil, revealing the unique seismic response of the system, including the buildup of excess pore pressure within the thick deposit. Based on the high-fidelity simulations, appropriate intensity measure (IM) and EDPs are identified, and corresponding damage states (DS) are determined. Fragility curves are then developed using multiple stripe analysis, so that the probability of damage under different input motion intensities can be quantified for different DS. Using the proposed procedure, the reinforcement effects of berms and gravel columns are evaluated. Results show that berms can contribute significantly to reducing the probability of damage for the system, while the effect of gravel columns is unsatisfactory due to the limited achievable installation depth compared to the thickness of the deposit and low replacement ratio.

This study presents a novel micromorphic continuum model for sand-gravel mixtures with low gravel contents, which explicitly accounts for the influences of the particle size distribution, gravel content, and fabric anisotropy. This model is rigorously formulated based on the principle of macro-microscopic energy conservation and Hamilton's variational principle, incorporating a systematic analysis of the kinematics of coarse and fine particles as well as macro-microscopic deformation differentials. Dispersion equations for plane waves are derived to elucidate wave propagation mechanisms. The results demonstrate that the model effectively captures normal dispersion characteristics and size-dependent effects on wave propagation in these mixtures. In long-wavelength regimes, wave velocities are governed by macroscopic properties, whereas decreasing wavelengths induce interparticle scattering and multiple reflections, attenuating velocities or inhibiting waves, especially when wavelengths approach interparticle spacing. The particle size, porosity, and stiffness ratio primarily influence the macroscopic average stiffness, exhibiting consistent effects on dispersion characteristics across all wavelength domains. In contrast, the particle size ratio and gravel content simultaneously influence both macroscopic mechanical properties and microstructural organization, leading to opposing trends across different wavelength ranges. Model validation against experiments confirms its exceptional predictive ability regarding wave propagation characteristics, including relationships between lowpass threshold frequency, porosity, wave velocity, and coarse particle content. This study provides a theoretical foundation for understanding wave propagation in sand-gravel mixtures and their engineering applications.

The sulphated gravel embankment in seasonal frozen soil regions may experience deformation problems such as salt expansion, frost heave, and settlement under rainfall percolation conditions and changes in environmental temperature, affecting considerably its normal use. In response to these issues, relying on the renovation and expansion project of an international airport in northwest China, this paper used a self-designed temperature control testing device and conducted indoor constant temperature tests and freeze-thaw cycle tests using on-site natural embankment filling, and conducted numerical simulation tests using the COMSOL Multiphysics software programme. This paper investigated the characteristics of temperature variation, moisture, salt migration, and deformation of sulphated gravel in seasonal frozen soil regions under rainfall percolation conditions. The results indicated that under environmental temperature changes in the range of- 10-25 degrees C, the temperature at which sulphated gravel salt expansion and frost heave occur was approximately-8 degrees C, and the deformation sensitive depth range from 0 to 200 mm. The moisture and salt contents of soil samples would experience a sudden increase due to rainfall percolation, with the sudden increase in moisture in the soil sample with a salt content of 0.9 % lagging that of the soil sample with a salt content of 0.5 % by one freeze-thaw cycle. Rainfall percolation significantly enhanced the settlement deformation of sulphated gravel during freeze-thaw cycles. The primary causes of soil deformation include the upward migration of water vapour, the downward percolation of moisture, and rainfall. These factors contribute to the destruction of the soil structure and alter the contact modes between soil particles, resulting in soil loosening and settlement deformation.

Gravel-bearing sandstone reservoirs represent a significant type of reservoir in oil and gas exploration. Due to the difference of the spatial random distribution the content and the shape of the gravel particles, these reservoirs exhibit complex mechanical properties and failure modes. In this study, a numerical model of gravel-bearing sandstone was developed by using the Finite Element Method (FEM) and were verified by the actual indoor experimental data. The effect of the gravel particle sizes, gravel content, and gravel types on the compressive peak strength and microcrack evolution processes are further analyzed. The results reveal that cracks initiate within the sandstone matrix surrounding the gravel and propagate through the gravel with continued loading. The primary factors governing the stability of gravel-bearing sandstone are the gravel radius and content. The variation in gravel penetration rate is synchronized with the changes in peak strength. By embedding gravel particles of different shapes into the model, it is observed that the peak compressive strength of round gravel is comparable to that of elliptical gravel, with both exhibiting higher peak strengths than angular gravel. Regression models demonstrate that the tensile strength difference between the gravel and the sandstone matrix is a critical parameter influencing gravel penetration. Confining pressure has a relatively minor effect on the elastic modulus, while its impact on peak compressive strength is significantly more pronounced.

Cemented sand-gravel (CSG) is an innovative material for dam construction with a wide range of applications. Nevertheless, a comprehensive understanding of the dynamic properties of CSG is lacking. A series of cyclic triaxial dynamic shear tests were carried out on CSG materials to investigate their complex dynamic mechanical properties, leading to the establishment of a dynamic constitutive model considering damage. The findings indicate that both the application of confining pressure and the addition of cementitious material have a noticeable influence on the morphology of the hysteresis curve. Further research scrutiny reveals that augmenting confining pressure and gel content leads to an increase in the dynamic shear modulus and a decrease in damping ratio. Furthermore, a constitutive dynamic damage constitutive model was constructed by linking a damage element to the generalized Kelvin model and defining the damage variable D based on energy interaction principles. The theoretical formulas for dynamic shear modulus and damping ratio were adjusted accordingly. In addition, the stiffness matrix of the dynamic damage constitutive model was derived, which demonstrated its strong fitting effects in dynamic triaxial shear tests on CSG. Finally, the dynamic response and damage distribution in the dam body under dynamic loading were analyzed using a selected CSG dam in China.

The interface between geotextile and geomaterials plays a crucial role in the performance of various geotechnical structures. Soil-geotextile interfaces often suffer reduced performance under environmental stressors such as rainfall and cyclic loading, limiting the reliability of geotechnical structures. This study examines the influence of gravel content (Gc), compaction degree (Cd), and rainfall duration (Rd) on the mobilized shear strength at the silty clay-gravel mixture (SCGM)- geotextile interface through a comprehensive series of direct shear tests under both static and cyclic loadings. A novel approach using Polyurethane Foam Adhesive (PFA) injection is introduced to enhance the interface behavior. The results reveal that increasing Gc from 0 % to 70 % leads to a 35-70 % improvement in mobilized shear strength and friction angle, while cohesion decreases by 15 %-60 %, depending on Cd. A higher Cd further boosts shear strength by 6 %- 70 %, influenced by Gc and normal stress levels. Under cyclic loading, increasing displacement amplitude reduces shear stiffness (K), while having minimal impact on the damping ratio (D); K and D appear unaffected by the number of cycles in non-injected samples. Rainfall reduces mobilized shear strength by 8 %-25 %, depending on the normal stress, with a 47 % drop in friction angle and a 24 % increase in cohesion after 120 minutes of rainfall exposure. In contrast, PFA-injected samples exhibit a marked increase in mobilized shear strength under both dry and wet conditions, primarily attributed to enhanced cohesion. Notably, PFA treatment proves particularly effective in maintaining higher shear strength and stiffness in rainfall-affected interfaces, demonstrating its potential in improving geotextile-soil interaction under challenging environmental conditions.

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.

Gravelly soils, characterized by a distinctive combination of coarse gravel aggregates and fine soil matrix, are widely distributed and play a crucial role in geotechnical engineering. This study investigates the mechanical behavior of gravelly soil subjected to simulated freeze-thaw (F-T) cycles using triaxial compressive strength tests. The long-term deviatoric stress response of specimens with varying gravel content and initial water content was analyzed under three distinct effective confining pressures (100, 200, and 300 kPa) across different F-T cycles. The results indicate that compressive strength is significantly influenced by gravel content, initial water content, and confining pressure. Notably, the rate of increase in deviatoric stress does not exhibit a proportional rise under confining pressures of 200 kPa and 300 kPa after 40 F-T cycles. However, a direct correlation is observed between deviatoric stress and increasing confining pressure (100, 200, and 300 kPa) over 2-, 4-, and 6-day intervals, this effect is more pronounced at higher confining pressures. The deviatoric stress peaks at different strain thresholds depending on the applied confining pressure; furthermore, no evident strain-softening behavior is observed across the tested conditions. These findings suggests that higher confining pressure inhibits particle displacement and interlocking failure, thereby reducing both the void ratio and axial strain within the soil matrix. Overall, these insights enhance our understanding of the complex interactions among gravel content, water content, confining pressure, and freeze-thaw effects, contributing to the understanding of the compressive strength evolution in gravelly soils under cyclic environmental loading.

The shear behavior of gravel-block soil (GBS) is unique and significant for evaluation the failure mechanism of GBS landslide on the Qinghai-Tibet Plateau. This study focuses on interpreting the shear behavior observed in the GBS during large-scale direct shear tests conducted on a landslide in Jiacha County, Tibet, China. The tests considered coarse particle content (CPC), dry density, and moisture conditions. Additionally, a discrete element numerical model, scaled to match the laboratory testing dimensions, was developed to simulate the large-scale direct shear tests on GBS. Results indicated that an increase in CPC improves the strength of the GBS, as it enhances the framework strength through interlocking between gravel blocks and between gravel blocks and the soil mass. The critical CPC for shear failure of the GBS exhibits a decreasing trend as the dry density increases. Furthermore, particle crushing rate (PCR) of the GBS is positively correlated with CPC, vertical pressure, and dry density. The simulation results show good agreement with the test results, providing insights into the damage-shear fracture mechanism of typical GBS under large-scale direct shear tests. The research outcomes provide a theoretical basis for the prevention and control of geological hazards in the Qinghai-Tibet Plateau.

Integral bridges with longer spans experience an increased cyclic interaction with their granular backfills, particularly due to seasonal thermal fluctuations. To accurately model this interaction behaviour under cyclic loading, it is crucial to employ appropriate constitutive models and meticulously calibrate and test them. For this purpose, in this paper two advanced elastoplastic (DeltaSand, Sanisand-MS) and two hypoplastic (Hypo+IGS, Hypo+ISA) constitutive models with focus on small strain and cyclic behaviour are investigated. The soil models are calibrated based on a comprehensive laboratory programme of a representative highly compacted gravel backfill material for bridges. The calibration procedure is shown in detail and the model capabilities and limitations are discussed on the element test level. Additional triaxial tests with repeated un- and reloading reveal significant over- and undershooting effects for the majority of the investigated material models. Finally, cyclic finite element analyses on the soil-structure interaction of an integral bridge are conducted to compare the performance of the soil models. Qualitatively similar cyclic evolution of earth pressures are detected for the soil models at various bridge lengths and test settings. However, a substantially different cyclic settlement behaviour is observed. Additionally, the investigation highlights severe overshooting effects associated with the tested hypoplastic soil models. This phenomenon is studied in detail using a single integration point analysis. Supplementary studies reveal that the foot point deformation of the abutment significantly influences the lateral passive stress mobilisation and the amount of its increase with growing seasonal cycles.