Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education

Shanghai, China

Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education

Shanghai, China

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Jiang M.,Tongji University | Jiang M.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | Xiao Y.,Tongji University | Xiao Y.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | And 2 more authors.
Geomechanics and Geotechnics: From Micro to Macro - Proceedings of the International Symposium on Geomechanics and Geotechnics: From Micro to Macro, IS-Shanghai 2010 | Year: 2011

This paper presents an experimental investigation on contact behaviors of idealized granules which are bonded together with cement. First, by using the specimen preparation devices, two aluminum alloy rods with the same size are glued together by cement with the cement water ratio 0.34. Then, by using of auxiliary loading devices, the mechanical behaviors of cementation between the bonded rods are obtained while different forces, such as normal force/shear force/couple force, are applied in different ways. The results show that: (1) The mechanical behaviors for the bonded rods are elasto-brittle in tension tests and stress softening in the compression tests, while the mechanical behaviors of the bonded rods are generally elasto-brittle-plastic in shear tests and elasto-softening-plastic in rotation tests (2) The mechanical behaviors of the bonded rods are in good agreement with the bond contact laws implemented in DEM. © 2011 Taylor & Francis Group.


Jiang M.-J.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | Jiang M.-J.,Tongji University | Li L.-Q.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | Li L.-Q.,Tongji University | And 4 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

Torsion shear tests are conducted by use of a dynamic hollow cylinder apparatus in Tongji University on the TJ-1 lunar soil simulant subjected to stress paths of excavation in order to investigate its deformation behaviors and non-coaxiality during the excavation under the earth environment. The test results indicate that (1) the stress path significantly affects the deformation behaviors of the TJ-1 lunar soil simulant; (2) the soils at the bottom of the pit and outside the diaphragm walls fail due to large deformation; (3) the soils at the bottom exhibit a tendency of contraction; (4) the soils adjacent to the diaphragm walls show remarkable non-coaxiality due to the coupled effects of stress ratio, rotation amplitude and rotation rate of the principal stress; and (5) the non-coaxiality of soils at the bottom of the pit is mainly affected by the rotation amplitude and rotation rate of the principal stress direction, while the non-coaxiality of soils outside the wall is controlled by the stress ratio, rotation amplitude and rotation rate of the principal stress direction.


Gu X.,Tongji University | Gu X.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | Hu J.,Tongji University | Hu J.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | And 2 more authors.
Granular Matter | Year: 2015

The coefficient of earth pressure at rest (Formula presented.) of granular soils is revisited by discrete element method simulation. The effects of confining pressure, soil density and over-consolidation ratio (OCR) on the (Formula presented.) value are investigated. The coefficients of earth pressure at rest defined in the conventional form (Formula presented.) and in the incremental form (Formula presented.) are compared. Most importantly, the microstructure of the soils (i.e. coordination number, anisotropies of contact normal and contact force) is monitored during the tests and it is used to explore the microscopic factors affecting the (Formula presented.) value of soils. The results suggest that (Formula presented.) and (Formula presented.) generally approach a similar constant when the applied vertical stress is 6-10 times and 4 times of the initial isotropic stress, respectively. Meanwhile, the (Formula presented.) value decreases as the void ratio decreases and the vertical stress increases. The OCR has a significant effect on the (Formula presented.) value and for the same OCR the (Formula presented.) value is quite different during unloading and reloading. Better predictions are obtained by Jaky’s equation and Mayne and Kulhway’s equation if peak friction angle is used. The analyses indicate that the (Formula presented.) value depends on the coordination number of the soil, which is consistent with its density-dependent macroscopic behavior. The results also indicate that the (Formula presented.) value is closely related to the anisotropy coefficients of contact normal (Formula presented.), normal contact force (Formula presented.) and tangential contact force (Formula presented.). During the initial (Formula presented.)-loading, (Formula presented.), (Formula presented.) and (Formula presented.) keep nearly constant and the evolution of (Formula presented.) during unloading and reloading is mainly resulted from the evolutions of (Formula presented.) and (Formula presented.). It reveals that the particle rearrangement is negligible and the soil mainly adjusts the particle contact force to resist the external load during the (Formula presented.) loading and unloading. © 2015 Springer-Verlag Berlin Heidelberg


Xiong J.,Tongji University | Xiong J.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | Kou X.,Tongji University | Kou X.,Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education | And 4 more authors.
Advanced Materials Research | Year: 2012

Methane hydrate is ice-like clathrate compound that attracts global attention due to its huge potential as a future energy source. The constitutive law of methane hydrate-bearing sediments remains unknown and becomes a barrier in sustainable exploitation of methane hydrate from marine sediments. The Duncan-Change model is a nonlinear elastic model which was widely accepted by the geotechnical community in approximating the constitutive response of geo-materials. This model and its evolved versions were employed in this study to model the stress-strain response observed in triaxial tests on methane hydrate-bearing sands. Duncan-Chang type models capture well the strain hardening behaviors. However, they fall short of incorporating the dependency of temperature and saturation degree of methane hydrate, which have to be taken into account in future constitutive models of methane hydrate-bearing deposits. © (2012) Trans Tech Publications, Switzerland.

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