PhD Student (University of Cambridge), visiting student
Office: 435 Davis Hall
Tsubasa’s research work includes soil liquefaction of the Urayasu City in Japan during the 2011 Tohoku Earthquake. In the undergraduate research at the University of Tokyo, Tsubasa carried out liquefaction tests on Urayasu sand using a hollow cylindrical torsional shear apparatus, in order to investigate the effect of the extremely long duration of earthquake motion on soil liquefaction. This study contributed to a better estimation of the liquefaction resistance of sandy soil during a gigantic earthquake (i.e. moment magnitude greater than 9.0). Tsubasa also worked on a novel soil improvement technique called microbially induced calcite precipitation (MICP) for liquefaction prevention. In his Master’s research, Tsubasa implemented undrained cyclic triaxial shear tests on Urayasu sand treated with MICP to assess MICP’s potential to increase the liquefaction resistance. This work revealed the detrimental effect of fines in the sand on the increase of liquefaction resistance by MICP, and suggested possible mechanisms and countermeasures.
Tsubasa’s current research interest is the wellbore integrity of oil and gas wells in compacting reservoirs and the fiber optic monitoring of wellbore integrity. Managing wellbore integrity in compacting reservoirs is critical to optimize the profit from such reservoirs. Recently, methane hydrate reservoirs have been experimentally developed by countries such as Japan, and methane hydrate reservoirs are often prone to significant compaction. In order to overcome this challenge for sustainable production of methane gas from methane hydrate reservoirs, the prediction and monitoring of wellbore integrity are essential. In this research, finite element analysis is carried out with the Cambridge Methane Hydrate Critical State model, which is best suited to model the mechanical behavior of methane hydrate-bearing soil, so as to predict wellbore integrity during reservoir compaction. In addition, distributed fiber optic monitoring is conducted in laboratory on wellbore specimens to monitor cement failures. The outcome of this research will be utilized in future field tests and will thus contribute to sustainable development of methane hydrate reservoirs.