Time filter

Source Type

Zhou J.,Tongji University | Zhou J.,University of Michigan | Tang Y.,Tongji University | Yang P.,Tongji University | And 4 more authors.
Natural Hazards | Year: 2012

Karst is widely distributed in the southwest of China, especially in Guizhou Province. The phenomenon of desertification in these areas is very serious. And soil erosion is the key link in the process of desertification. Through field monitoring, underground soil leakage is derived to the main mode of soil loss in this area. Shear strength tests and creep experiments were carried out with the aim of analyzing the creep mechanism in underground soil loss. It is shown that the water content can lead to the great influence on the shear strength of the brown clay. This variation has been combined with creep characteristics besides the structural geology, hydrology condition and brown clay distribution circumstance (field observation). A conceptual creep model of the brown clay sliding along the karst conduits has been unveiled to show the detailed inference of the creep mechanism in the underground soil loss: geology and hydrology control the development of the karst conduit system; and penetration of water induces the weakening of the shear strength of the surface soil and accelerates the creeping and sliding of the brown clay along the karst conduit system. This understanding of the creep mechanism has significant implications for the future management of the soil erosion in the karst area. © 2012 Springer Science+Business Media B.V.

Tang Y.,Tongji University | Li J.,Tongji University | Zhang X.,Tongji University | Yang P.,Tongji University | And 3 more authors.
Natural Hazards | Year: 2013

Karst rocky desertification is one of the major ecological and environmental problems that threaten the sustainable development of southwestern China. This study focuses on a case study of the small watershed in Chenqi where karst rocky desertification is particularly severe. This paper considers samples of soils from six different land use patterns in Chenqi village. Various correlations are observed by using fractal theory, including an emerging model for studying soil aggregates. This study demonstrates how the fractal characteristics of soil structure and the stability of soil aggregates are crucial to better understanding karst rocky desertification. The fractal dimension of different land use patterns can be used to indicate the magnitude of soil destruction. Soil fractal dimension can be applied using different methods to characterize the changes in factors influencing the stability of soil structure. The results indicate a significant negative relationship between fractal dimension of soil aggregates and large aggregate content (of diameters 5-10 mm) and a significant positive relationship between fractal dimension and micro-aggregate content (<0. 25 mm). The fractal dimension of soil aggregates is also significantly negatively correlated with both clay content and organic matter content. These results suggest that fractal dimension can be used as a reliable indicator of soil quality and presents advantages compared to using mean weight diameter. © 2012 Springer Science+Business Media B.V.

Ye W.,Tongji University | Ye W.,Beijing Research Institute of Uranium Geology | Zhu J.-Y.,Tongji University | Chen B.,Tongji University | And 2 more authors.
KSCE Journal of Civil Engineering | Year: 2012

During the long-term operation of a conceptual multi-barrier deep geological repository for disposal of high-level nuclear waste, performance of the artificial barrier system (compacted bentonite) with consideration of influences of the surrounding rocks has to be evaluated for tens of thousands of years. Numerical simulation technology could be one of the most effective assessment methods. In order to have confidence in the prediction of the coupled hydraulic and mechanical processes occurring within the engineered clay barrier, a comparison between calculated and observed results is essential for validation and verification. For this purpose, a new Hydro-Mechanical (HM) device was designed in this paper, in which compacted GMZ01 bentonite specimen was embedded into a hollow Beishan granite column, which was tightly fixed by a closure metal framework. Relative humidity and pressure sensors were employed for monitoring behavior of the compacted bentonite during hydration, in order to observe the HM coupling performance of the compacted bentonite with consideration of influences of surrounding rocks at room temperature. The newly-developed test device includes three parts, a bottom plug, a cylindrical metal cell body and a top plug, which were tightly fixed together with four screws to form a confined (constant volume) closure system. Relative humidity and pressure sensors were implemented. Relative humidity sensors were calibrated before installation. With this newly-developed device, the GMZ01 bentonite-Beishan granite specimen was submitted to hydration. Some interesting preliminary results of the HM behavior of the compacted GMZ01 bentonite with consideration of the bentonite/rock interactions were obtained and discussed. © 2012 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.

Loading United Research Center for Urban Environment and Sustainable Development collaborators
Loading United Research Center for Urban Environment and Sustainable Development collaborators