Shanghai Construction Design and Research Institute Co.

Shanghai, China

Shanghai Construction Design and Research Institute Co.

Shanghai, China
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Chen B.,Tongji University | Guo J.,Tongji University | Zhang H.,Shanghai Construction Design and Research Institute Co.
Clay Minerals | Year: 2016

Concepts for geological disposal of high-level radioactive waste usually include bentonite buffer materials. Numerous studies have been performed with most using Wyoming bentonite. Gaomiaozi (GMZ) bentonite has been selected as a potential buffer/backfill material for the deep geological repository of high-level radioactive waste in China. In this context, the highly alkaline environment induced by cementitious materials in the repository is likely to alter montmorillonite, the main clay mineral in GMZ bentonite. This alteration may result in deterioration of the physical and/or chemical properties of the buffer material. To acquire quantitative data which would allow us to assess the dissolution of montmorillonite and changes in the diffusivity of hydroxide ions as well as their effects on the swelling pressure and permeability of the compacted GMZ bentonite, an experimental study was conducted under highly alkaline (NaOH solutions with various pH values were used), simulated groundwater conditions. The GMZ bentonite also contains cristobalite which may also have been dissolved. The microstructure of the compacted bentonite samples after the experiments was determined by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDX) was carried out to identify mineralogical changes. At pH >13, the permeability of specimens increased significantly; the swelling potential decreased with increasing pH. Furthermore, the pore volume and pore size of GMZ bentonite changed when exposed to alkaline solution, resulting in an increase in porosity and permeability. The main alteration mechanisms of compacted GMZ bentonite undergoing infiltration by highly alkaline solution are likely to be dissolution and modifications in terms of the microstructure and mineralogy. © 2016 Mineralogical Society 2016.


Yang J.,Shanghai Construction Design and Research Institute Co. | Chen J.,Shanghai Construction Design and Research Institute Co. | Xie Z.,Shanghai Construction Design and Research Institute Co. | Gu Y.,Shanghai Construction Design and Research Institute Co. | Zhang H.,Shanghai Construction Design and Research Institute Co.
Geotechnical Special Publication | Year: 2014

With the development of urban construction, the excavation area of a foundation pit becomes larger, the depth becomes deeper, and the surrounding environment becomes more complex, which requires higher environment risk control. As a new construction method,the pit-divided method becomes more and more prevalent in the foundation pit. The designed new site of Shanghai International Dance Center is located at the center of Hongqiao historical protection area. With the large excavation area, irregular shape, complex surroundings, the Yan'an viaduct on the southern side, the metro line 10 on the northern side, and the six historical conservation buildings around, there is great difficulty for design and construction. By numerical simulation, this paper draws a conclusion that the pit-divided method has obvious effect on control of the surrounding environment around the pit, which provides scientific guidance for design and construction of the pit. © 2014 American Society of Civil Engineers.

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