Problematic Soils and Rocks: From Micro to Macro
Published:2015-01-02 Hits:1585
Problematic geomaterials (e.g., structural sands, collapsible loess, methane hydrate bearing sands, weathered rocks, lunar regolith) challenge the classic soil mechanics due to their abnormal mechanical behavior arising from peculiar microstructure. It becomes essential to endow the macroscopic constitutive relations of problematic soils and rocks, which are often phenomenological, with the physical origin taking place on the particulate scale, which rules the macroscopic properties of geomaterials. The connection between the two scales is the focus of this research. 
(4)To establish microscopic contact models for problematic geomaterials, including structural sands, loess, methane hydrate bearing sands, lunar regolith, rocks.
(5)To develop rational continuum-based models for problematic geomaterials, which capsulate the mechanisms on the microscopic scale.   
Micro mechanical experiments were performed on idealized bonded particles to feature the mechanical response and strength of bonded particles. The observed contact laws were then implemented into bond contact models with minimum hypotheses to feature the mechanical behavior of soils/rocks on both microscopic and macroscopic scales using the distinct element method (DEM). The macroscopic constitutive models of soils/rocks were enhanced according to DEM results. Meanwhile, basic laboratory tests were conducted to examine the constitutive relations on limited stress paths and validate the numerical simulations. 
Significant Results and Potential Impact: 
This research leads to a series of original contact models, which demonstrate rationality and effectiveness to feature the micro- and macro-properties of methane hydrate bearing sands, lunar regolith, rocks, and structural sands. It also provides an effective approach to disclose the micro-mechanism on the particulate scale of problematic soils/rocks, which is essential in governing their macroscopic properties but is far from being fully understood using conventional testing techniques and numerical simulations. 
Principal Investigator:
Mingjing Jiang, Fang Liu.
      China National Funds for Distinguished Young Scientists: Rock and Soil Mechanics Engineering (51025932)
      National Natural Science Foundation of China (key project): Key Testing Techniques and Engineering Properties of Gas Hydrate Bearing Soils (51239010)
      National Natural Science Foundation of China: Study on the Interaction Mechanism between Lunar Soil and Probe under Complicated Situation (51179128)
      National Natural Science Foundation of China: Microscopic Mechanism of Non-coaxiality of Sand and Its Macro and Micro Numerical Simulation Analysis (10972158)
      Ph.D. Programs Foundation of Ministry of Education of China: Micro-constitutive Theory and DEM Simulation of Methane Hydrate-bearing Sediments in Deep Seabed (20100072110048)
Key Publication: 
      12.Jiang M J, Liu F, Zhou Y P. A bond failure criterion for DEM simulations of cemented geomaterials considering variable bond thickness, International Journal for Numerical and Analytical Methods in Geomechanics, 2014, DOI: 10.1002/nag.2282.
      13.Jiang M J, Zhu F Y, Liu F, Utili S. A bond contact model for methane hydrate bearing sediments with inter-particle cementation, International Journal for Numerical and Analytical Methods in Geomechanics, 2014, DOI: 10.1002/nag.2283.
      14.Jiang M J, Chen H, Tapias M, Arroyo M. Study of mechanical behavior and strain localization of methane hydrate bearing sediments with different saturations by a new DEM model. Computers and Geotechnics, 2014, 57C: 122-138.
      15.Jiang M J, Zhang F G, Sun Y G. An evaluation on the degradation evolutions in three constitutive models for bonded geomaterials by DEM analyses. Computers and Geotechnics, 2014, 57: 1-16.
      16.Jiang M J, Li T, Hu H J, Thornton C. DEM analyses of one-dimensional compression and collapse behaviour of unsaturated structural loess. Computers and Geotechnics, 2014, 60: 47-60.
      17.Jiang M J, Shen Z F, Colin Thornton, Microscopic contact model of lunar regolith for high efficiency discrete element analyses, Computers and Geotechnics, 2013, 54: 104-116.
      18.Jiang M J, Li L Q, Yang Q J. Experimental investigation on deformation behavior of TJ-1 lunar soil simulant subjected to principal stress rotation. Advances in Space Research, 2013, 52(1): 136-146.
      19.Jiang M J, Zhang W C. DEM investigation on mechanical behavior within shear bands in granulates under Earth and Moon conditions. Theoretical and Applied Mechanics Letters, 2013, 3(2): 1-5.
      20.Jiang M J, Li L Q, Sun Y G. Properties of TJ-1 lunar soil simulant. Journal of Aerospace Engineering, 2012, 25(3): 463-469.
      21.Jiang M J, Sun Y G, Yang Q J. A simple distinct element modeling of the mechanical behavior of methane hydrate-bearing sediments in deep seabed. Granular Matter, 2013, 15(2): 209-220.
      22.Jiang M J, Liu J D, Sun Y G, Yin Z Y. Investigation into macroscopic and microscopic behaviors of bonded sands using the discrete element method, Soils and Foundations, 2013, 53(6): 804-819.
      23.Jiang M J, Zhang W C, Sun YG, Utili S. An investigation on loose cemented granular materials via DEM analysis, Granular Matter, 2013, 15(1): 65-84.
      24.Jiang M J, Sun Y G, Li L Q, Zhu H H. Contact behavior of idealized granules bonded in two different interparticle distances: An experimental investigation, Mechanics of Materials, 2012, 55: 1-15.
      25.Jiang M J, Sun Y G, Xiao Y. An experimental investigation on the mechanical behavior between cemented granules, Geotechnical Testing Journal (ASTM), 2012, 35(5):678-690.
      26.Jiang M J, Hu H J, Liu F. Summary of collapsible behaviour of artificially structured loess in oedometer and triaxial wetting tests. Canadian Geotechnical Journal, 2012, 49(10): 1147-1157.
      27.Jiang M J, Hu H J, Peng J B, Leroueil S. Experimental study of two saturated natural soils and their saturated remoulded soils under three consolidated undrained stress paths. Frontiers of Architecture and Civil Engineering in China, 2011, 5(2):225-238.
      28.Jiang M J, Yan H B, Zhu H-H, Utili S. Modeling shear behavior and strain localization in cemented sands by two-dimensional distinct element method analyses. Computers and Geotechnics, 2011,38:14-29.
      29.Jiang M J, Zhu H H, Li X-M, Strain localization analyses of idealized sands in biaxial tests by distinct element method. Frontiers of Architecture and Civil Engineering in China (FAC), 2010, 4(2): 208-222.
      30.Jiang M.J, Leroueil S, Zhu H H, Yu H S, and Konrad J M, Two-Dimensional discrete element theory for rough particles, International Journal of   Geomechanics (ASCE), 2009,9(1): 20-33.
      31.Jiang M J, Peng L C,Zhu H H, Lin Y X, and Huang L J, Macro- and Micro- properties of two natural marine clays in China, China Ocean Engineering, 2009, 2:329-344.
      32.Jiang M J, Zhu H H, Harris D. Classical and non-classical kinematic fields of two-dimensional penetration tests on granular ground by discrete element method analyses. Granular Matter, 2008, 10, 439-455.
      33.Jiang M J, Zhu H H. An interpretation of the internal length in Chang’s couple-stress continuum for bonded granulates. Granular Matter, 2007, 9: 431-437.
      34.Jiang M J, Yu H S, Leroueil S. A simple and efficient approach to capturing bonding effect in naturally microstructured sands by Discrete Element Method. Int. Journal for Numerical Methods in Engineering, 2007, 69: 1158-1193.
      35.Jiang M J, Harris D, Zhu H H. Future continuum models for granular materials in penetration analyses. Granular Matter, 2007, 9: 97-108.
      36.Jiang M J, Yu H S, Harris D. Bond rolling resistance and its effect on yielding of bonded granulates by DEM analyses. International Journal for Numerical and Analytical Methods in Geomechanics, 2006, 30(7): 723-761.
      37.Jiang M J, Yu H S, Harris D. Discrete element modelling of deep penetration in granular soils. International Journal for Numerical and Analytical Methods in Geomechanics, 2006, 30(4):335-361.
      38.Jiang M J, Yu H S, Harris D. Kinematic variables bridging discrete and continuum granular mechanics. Mechanics Research Communication, 2006, 33: 651-666.