Review: Calibration of the discrete element method

Energy demand in China has risen rapidly and reached an unprecedented level due to the high-speed economic growth and modern development. As a result, the Chinese government faces a growing pressure to address the energy shortage and environmental deterioration, mainly resulting from an over-dependence on fossil energy. China has become both the largest energy consumer and CO 2 emitting country in the world in 2015. Utilization of potential for renewable energy is necessary for changing inappropriate energy consumption structure, protecting environment and achieving sustainable economic and social development. In view of such mentioned situation, this paper firstly introduces the energy structure as well as the development status of renewable energy in China, which includes hydropower, wind power, solar power, biomass power and other renewable energy. Besides, based on the current situation in China, the paper makes a preliminary prediction of the development of renewable energy in the country for the future decades, and proposes targeted countermeasures and suggestions.

Present situation and future prospect of renewable energy in China

China's water policies in the past decades have relied heavily on the construction of massive water conservancy projects in the form of dams and reservoirs, water transfer projects, and irrigation infrastructure. These facilities have brought tremendous economic and social benefits but also posed many adverse impacts on the eco-environment and society. With the intensification of water scarcity, China's future water conservancy development is facing tremendous challenge of supporting the continuous economic development while protecting the water resources and the dependent ecosystems. This paper provides an overview of China's water conservancy development, and illustrates the socioeconomic, environmental and ecological impacts. A narrative of attitude changes of the central government towards water conservancy, as well as key measures since the 1950s is presented. The strategic water resources management plan set by the central government in its Document No. 1 of 2011 is elaborated with focus on the three stringent controlling “redlines” concerning national water use, water use efficiency and water pollution and the huge investments poised to finance their implementation. We emphasize that realizing the goals set in the strategic plan requires paradigm shifts of the water conservancy development towards maximizing economic and natural capitals, prioritizing investment to preserve intact ecosystems and to restore degraded ecosystems, adapting climate change, balancing construction of new water projects and rejuvenation of existing projects, and managing both “blue” (surface/groundwater) and “green” water (soil water).

Water conservancy projects in China: Achievements, challenges and way forward

Soils that exhibit nonassociated flow may, according to stability postulates by Drucker and by Hill, become unstable when exposed to certain stress paths inside the failure surface. Series of conventional triaxial tests on fully saturated and on partly saturated specimens were performed under drained and undrained conditions to study the regions of stable and unstable behavior. For specimens that compress and have degrees of saturation higher than critical, undrained conditions lead to effective stress paths directed within the region of potential instability, and instability was observed provided the yield surface opens up in the outward direction of the hydrostatic axis. Thus, instability occurs inside the failure surface. Instability is not synonymous with failure, although both may lead to catastrophic events. The location of the instability line is discussed. Examples of a shallow submarine slope and a nearly fully saturated steeper slope representing a tailings dam, which both should remain stable a...

Closure of "Static Instability and Liquefaction of Loose Fine Sandy Slopes"

3D computer simulations and experiments are employed to study random packings of compressible spherical grains under external confining stress. In the rigid ball limit, we find a continuous transition in which the stress vanishes as (straight phi-straight phi(c))(beta), where straight phi is the (solid phase) volume density. The value of straight phi(c) depends on whether the grains interact via only normal forces (giving rise to random close packings) or by a combination of normal and friction generated transverse forces (producing random loose packings). In both cases, near the transition, the system's response is controlled by localized force chains.

Packings of Compressible Granular Materials

Hydropower in China at present and its further development

Settlement analysis of the Shuibuya concrete-face rockfill dam

Modeling the fragmentation of rock grains using computed tomography and combined FDEM

Modeling the particle breakage of rockfill materials with the cohesive crack model

This paper presents simulations of true triaxial tests on crushable granular materials. Considering both the shear and tensile fracture modes of the particle, the Mohr–Coulomb model with tension cut-off is employed as the fracture criterion of single particle. When the particle stresses satisfy the fracture criterion, three new balls are generated to replace the broken particle. The new balls overlap enough within the bounding parent sphere to obey the mass conservation law. A polydisperse assembly consisting of 7935 spheres was isotropically compressed until the desired confining pressure was reached. Then the sample with no bias in initial fabric was subjected to axial compression at a constant minor principal stress under different intermediate principal stress ratios, b. The simulated stress–strain–dilation responses were in agreement with the experimental observations. The macro–micro responses including stress–strain characteristics, fabric tensors, anisotropies, the orientation tensor and force chain characteristics were discussed in details. It is shown that volumetric responses is affected by b. The anisotropies vary with b, but a unique macro–micro linkage exists between the anisotropies and stress ratio, q / p, irrespective of the value of b. A linear relationship is found between the obliquity of $${\sigma _{1} }/{\sigma _{3} }$$
 and the strength indicator (
 $$\beta =\ln ({\tau _{1} }/{\tau _{3} }))$$
 using the orientation tensor method.

Xiaolin Chang

Papers

Hydropower in China at present and its further development

Settlement analysis of the Shuibuya concrete-face rockfill dam

Modeling the fragmentation of rock grains using computed tomography and combined FDEM

Modeling the particle breakage of rockfill materials with the cohesive crack model

Macro–micro responses of crushable granular materials in simulated true triaxial tests