Article
Engineering, Geological
Xiaoli Xie, Bin Ye, Teng Zhao, Xiaoqing Feng, Feng Zhang
Summary: Prior earthquakes have significant impacts on the liquefaction resistance of sandy soils. Non-liquefying loading can either increase or decrease the liquefaction resistance, depending on the cyclic stress ratio and excess pore pressure ratio. Specimens previously loaded under larger cyclic stress ratios exhibited lower liquefaction resistance after reconsolidation, while those reconsolidated from smaller cyclic stress ratios showed higher liquefaction resistance. Sand liquefaction resistance is correlated with initial anisotropic degree and mechanical average coordination number.
SOIL DYNAMICS AND EARTHQUAKE ENGINEERING
(2022)
Article
Engineering, Geological
W. Rong, J. S. McCartney
Summary: This study investigated the volumetric changes of unsaturated sand specimens during undrained cyclic shear tests, revealing a nonlinear relationship between volumetric contraction and degree of saturation. The largest contraction occurred at a saturation degree of 0.4, coinciding with the largest decrease in mean effective stress. The sand specimens followed a wetting-path scanning curve during shearing, with small changes in matric suction.
JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING
(2021)
Article
Engineering, Geological
Kangda Wang, Jian Chu, Shifan Wu, Jia He
Summary: The study demonstrates that microbial desaturation enhances the liquefaction resistance of sand under both monotonic and cyclic loading conditions, with shear strength increasing more than two times when saturation is reduced from 100% to 86.4%. Results also show significant improvement in liquefaction resistance under cyclic loading when samples are slightly desaturated.
Article
Engineering, Marine
Yang Guang-chang, Bai Bing, Liu Yang, Chen Pei-pei
Summary: A thermodynamic constitutive model is developed to describe the undrained shear behavior of gassy sand based on the thermodynamic theory of granular matter and the dilatancy equation. The model considers dissipation at the mesoscopic level and introduces the concept of granular temperature to describe irreversible deformation of gassy sand. The relationship between dissipation mechanism and macroscopic mechanical behavior is established through migration coefficients and energy density functions.
Article
Energy & Fuels
Yanlu Ding, Anna Qian, Hailong Lu
Summary: This study investigates the mechanical properties of hydrate-bearing sediments by considering the morphology and distribution of hydrates. The results show that the morphology of hydrates significantly affects the mechanical behavior of sediments, while the distribution heterogeneity has a smaller influence. Heterogeneous sediments exhibit higher shear strength, and the cementing type of sediments has the highest mid-strain modulus.
GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
(2022)
Article
Engineering, Marine
Tianju Wang, Yanlu Ding, Rui Wang, Anna Qian, Hailong Lu, Boyu Zhou
Summary: A pore-scale method is proposed to model cemented hydrate-bearing sediments (HBSS) using the discrete element method (DEM), capturing the hydrate distribution heterogeneity. The mechanical behavior of heterogeneous HBSS is investigated and it is found that both macroscopic and microscopic hydrate distribution heterogeneity can influence the mechanical properties of HBSS. The findings provide insights into understanding the mechanical behavior of natural HBSS with heterogeneous hydrate distributions.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2023)
Article
Engineering, Geological
Q. X. Wu, Z. X. Yang
Summary: The undrained response of sand under principal stress rotation (PSR) has been studied using the discrete element method, providing insights into the fabric evolution and macroscopic mechanical behavior of granular materials under rotational shear.
JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING
(2022)
Article
Engineering, Geological
Md Mizanur Rahman, Yannis F. Dafalias
Summary: This study discusses the effects of fabric anisotropy and fines content on the mechanical behavior of sands, and develops the Anisotropic Critical State Theory and Equivalent Granular State Theory for clean sands. By combining these two theories, a constitutive model is proposed to simultaneously consider the effects of fabric anisotropy and fines content on the undrained response of sands.
Article
Engineering, Geological
Quoc T. Phan, Ha H. Bui, Giang D. Nguyen, Abdelmalek Bouazza
Summary: This study demonstrates that the rolling resistance of silty sand significantly influences its critical state, peak state, and zero-dilatancy state, and the rolling resistance of fine particles can reduce the liquefaction susceptibility of the sand.
Article
Computer Science, Interdisciplinary Applications
Yanlu Ding, Anna Qian, Hailong Lu, Yuan Li, Yi Zhang
Summary: Understanding the engineering properties of hydrate-bearing sands (HBS) is crucial for assessing the safety of natural gas hydrate exploitation. However, precise testing of HBS specimens with different hydrate morphologies has been difficult due to the challenges in controlling hydrate formation in the laboratory. In this study, the discrete element method (DEM) is employed to create HBS models with various hydrate morphologies, and biaxial compression tests are simulated to evaluate their mechanical properties. The numerical results demonstrate that the shear strength and secant modulus of HBS are affected by hydrate morphology and saturation, and relationships between micro mechanical analyses and macro mechanical properties are established. These findings provide valuable insights into the mechanical responses of HBS with complex hydrate morphologies.
COMPUTERS AND GEOTECHNICS
(2022)
Article
Energy & Fuels
Lei Wang, Shi Shen, Zhaoran Wu, Pengyu Chen, Yanghui Li
Summary: This study focuses on the investigation of undrained mechanical characteristics of hydrate-bearing fine-grained soils in order to achieve safe and efficient hydrate exploitation. The results show that temperature has a significant influence on the failure strength of clayey silts, both with and without hydrates. The presence of hydrates also affects the excess pore pressure response and effective stress paths of clayey silts. These findings contribute to a better understanding of the stability of hydrate reservoirs in the South China Sea under environmental changes and thermal injection for hydrate extraction.
Article
Engineering, Geological
Q. X. Wu, J. J. Zheng, Z. X. Yang
Summary: This study presents a convenient and efficient DEM sample preparation procedure to generate three-dimensional specimens with different intensities of initial fabric anisotropy. The initial fabric can be altered by changing the bedding plane angle α of the soil deposition relative to the horizontal plane. A range of α values was considered, from -90 to 90 degrees. Undrained rotational shear tests were conducted on these initially anisotropic samples using a novel discrete element approach. The simulation results provide new insights into the strain evolution patterns and fabric evolutions of initially anisotropic samples under undrained rotational shear.
Article
Energy & Fuels
Yi Wang, Feng-Qiu Long, Xiao-Sen Li, Ya-Ting Xu, Xuan Kou
Summary: This study aims to identify effective sand control methods for hydrate reservoir development. The experimental results showed that polyurethane foam can effectively prevent sand production in the reservoir.
Article
Engineering, Marine
Yujing Jiang, Meng Li, Hengjie Luan, Yichen Shi, Sunhao Zhang, Peng Yan, Baocheng Li
Summary: This study investigates the effect of dynamic loading on the mechanical properties of gas-hydrate-bearing sediments using numerical tests and particle flow code. The loading frequency has a small effect on the stiffness, but a significant effect on the peak strength. The peak strength increases and then decreases with the increase in loading frequency. Under the same loading frequency, the peak strength increases with the increase in loading amplitude, while the stiffness decreases. The maximum shear expansion of the specimen is influenced by the movement of the phase change point and the rearrangement of particles.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2022)
Article
Engineering, Ocean
Javad Saeidaskari, Mahdi Alibolandi, Alireza Saeedi Azizkandi
Summary: The research investigated the undrained behavior of calcareous sand in Qeshm island, Iran. It found that increasing effective confining pressure led to higher excess pore water pressure under cyclic loading. Higher relative density and over consolidation ratio enhanced shear modulus and reduced liquefaction potential, while particle breakage increased with increasing shear strain and effective confining pressure.
MARINE GEORESOURCES & GEOTECHNOLOGY
(2021)
