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Loading Rate Effects on Strength and Stiffness of Frozen Sands
이장근,김영석,채덕호,조완제 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.1
The seasonally frozen ground has been focused on as research topics such as the frost heaving under the asphalt road rather than the permafrost ground due to the latitudinal location of Korea. However, the recent construction of the second Korean Antarctic research station, the Jangbogo station and the participation on the development of the natural gas pipeline in Russia arouse the research interests on the behavior of the permafrost ground. At the design process of the geotechnical structures on the permafrost ground, the evaluation of the mechanical characteristics of frozen soil is very important. In the laboratory tests, it is crucial to understand the effects of testing conditions such as loading rate and temperature on the mechanical behavior of frozen soils. Therefore, unconfined compression tests are performed to evaluate the loading rate effects on the mechanical characteristics of frozen granular soils. Based on the experimental results, the loading rate affects both the strength and deformation characteristics of the frozen soils. The ASTM standards on the loading rate of the frozen sands are fast enough for the strength evaluations but not for the stiffness evaluations. Furthermore, the loading rate effects are evaluated on the bearing capacity and deformation of pile installed on the permafrost via numerical analyses with experimental results.
이장근,박재우 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.6
In situ capping is one of the preferable remediation technologies for sediments contaminated by heavy metals because of its relatively modest cost. However, it has been used to isolate heavy metals without having detailed information available regarding the effect of consolidation and the chemical isolation caused by in situ capping. This paper presents a numerical estimation of in situ capping efficiency for mitigating heavy metals in sediments when a groundwater flow condition is included. Numerical simulations were conducted using a computational model (CST2) in which contaminant transport occurs by advection, dispersion, and sorption. The results from numerical simulations indicate that the discharge rate of dissolved heavy metals increases during and for some time after capping installation but decreases because of a significant reduction in advection after 100% consolidation. In addition, tailing effect which is the main reason for the long term release of heavy metals is caused by consolidation. Further simulations shows that a multilayered capping system with a thin reactive layer provides an effective barrier to contaminant transport even though consolidation caused by in situ capping results in the negative effects on mitigating heavy metals.