Water and Salt Migration with Phase Change in Saline Soil during Freezing and Thawing Processes
Water and salt transfer coupled with phase change may cause serious damage to engineering structures in saline soil regions. In this study, the migration of water and salt in silty clay collected from the Qinghai‐Tibet Plateau is explored experimentally and numerically during freezing and thawing processes. The results revealed that there are significant differences in the variations of liquid water content and solution concentration for different initial salt contents, due to salt crystallization and dissolution. The temperature‐induced water migration is determined by the soil properties, which can be well explained by the thermodynamics of mass transfer. The amount of salt migrated upward during cooling is slightly larger than that transported downward in the warming period, implying that salt may be accumulated in the surface soil after a large number of circulations and finally result in soil salinization.
Experimental study of characteristics of frost and salt heaves of saline highway foundation soils in seasonally frozen regions in Gansu Province
Under the impact of frost heave,thaw settlement and salt heave on the embankment and pavement of the highways in the zones of seasonally frozen ground in Gansu province,Northwestern China,many road damages,which has serious influence on road stability and security,occurred such as pavement cracks and road boiling etc.In this paper,repeated freeze-thaw experiments of saline soils taken from where some damages always occurred in the subgrade and pavement were conducted to investigate the characteristics of frost heave,thaw settlement and salt heave of these saline soils under the periodically fluctuating temperature,and to study the mechanisms of the road damages.The experimental results show that salinity has significant impact on the deformation process;and that the deformation mechanisms are different for the saline soils with different salinity.When salinity is very high,the deformation is mainly caused by salt heave.When salinity is low,the deformation mainly results from frost heave and thaw settlement with possible frost heave.For the non-salt and frost susceptible soil,it is caused by frost heave and thaw settlement.Meanwhile,some suggestions have been proposed to prevent the embankment and pavement of highways from damages and instability in saline soil regions.
Geological, mineralogical and chemical characterization of Devonian kaolinite-bearing sediments for further applications in the ceramic (tiles) industry in La Paz, Bolivia
Clay minerals are widely distributed in Bolivia; among them, illitic clays are most common in the Altiplano where they are mined for use in the ceramic industry that has been growing in the last few years. In addition to illitic sediments, kaolinitic sediments have been recently discovered in sedimentary units in the Bolivian Altiplano. Residual ball clay occurrences in Devonian sedimentary units were studied as part of this work. Geological mapping and geophysical studies (ERT and GPR) were done for better understanding the origin of the deposits and were part of a preliminary study of the mineral potential to define the relationship with the host rock. Chemical and mineralogical techniques such as X-Ray Diffraction, Scanning Electron Microscopy and Inductively Coupled Plasma analyses were performed in samples from the studied area to verify the presence of kaolinite. Atterberg limits and behaviour of the raw material in ceramic specimens supported by chemical analyses show that this material is suitable for manufacturing tile ceramics. This study provides fundamental knowledge for deposit exploitation and future generation of an alternative source of employment for the inhabitants of Micaya.