Welcome

July 2019
Welcome to the website of Geomechanics group at YNU. Geomaterials are a mixture of solid, liquid and gas, which exhibits complex but fascinating behavior. We are tackling challenging topics on such material to overcome the limitations of current geomechanics. In particular, our primary approach is to develop a rational model to predict mechanical and hydraulic behavior of geomaterials with a smaller number of simplified assumptions. We are a group of enthusiastic researchers and students from different regions of the world. I hope that you will enjoy visiting our website and that the visit will inspire you.

Advances of elastoplastic theory to broader phenomena
We are trying to develop a constitutive model that can predict broader, complex behavior of soils with smaller number of simplified assumptions.
Three dimensional state boundary surface : Critical state line that has ordinarily been assumed to be unique in the plane of specific volume and mean effective stress is extended to include the effect of changing grading.
(This work was supported by JSPS Grant-in-Aid for Challenging Exploratory Research, 2012-2014)

Fig. : 3-dimensional critical state surface extended to the direction of grading state index (Soils Found., 2010)

Contribution to Environmental Geotechnics
We developed a pressure-saturation model for immissible multiphase fluids in porous media (Soils Found., 2014; Contaminant Hydrology, 2018) and solved initial/boundary value problems on ground contamination (Envron. Geotech., 2015).
We applied for the patent (application 2014-109802, 2014; publication 2015-225494, 2015) for our simulation method and are working towards its practical use.
(This work is supported by JSPS Grant-in-Aid for Challenging Explaratory Research, H27-28)

Movie : Three-phase seepage simulation on contamination of unsaturated ground by L/DNAPL

Empirical engineering to rational theories
We aim to describe soil behavior that has only been explained empirically or experimentally.
We are trying to simulate the behavior of geostructures such as embankments from costruction process to the deformation and failure due to heavy rain and/or earthquake.
(This work is supported by JSPS Grant-in-Aid for Scientific Researc (B), H24-26, and JSPS Grant-in-Aid for Young Scientists (A), H28-30.

Fig. : Compaction curve obtained by the simulation using elastoplastic model for unsaturated soils (Proc. 14ARC, 2011; Proc. E-UNSAT, 2016)

Application of latest geomechanics towards pathbreaking, exploratory researches
We carried out the field surveys of masonry structures in Angkor Thom, Cambodia, and conducted laboratory tests on soils obtained in situ (Proc. JGS, 2014). We applie a numerical method, elastoplastic NMM-DDA, to clarify the deformation mechanism of masonry structures (Geosys. Engrg., 2013; Japanese geotechnical journal, 2016; Computers Geotech. 2017).
(This work was supported by JSPS Grant-in-Aid for Scientific Research (B), H25-27)

Picture : Survey of soil properties at Bayon temple in Angkor Thom

Development of new technologies
We aim to develop novel methods that can contribute practical geotechnical engineering.
We developed a method for measuring mechanical anisotropy of rock masses by a single triaxial test (Rock Mech. Rock Engrg., 2017; Geotech. Engrg. J., 2015; JGS Best Paper Award, 2016) or a single torsional shear test (JSCE Journal Ser. C, 2015).

Fig. : On-site torsional shear test on rock mass and determination process of anisotropy (Patent application 2013-148114, 2013; publication 2015-21767, 2015)

Interdisciplinary / integrated researches
We are challenging interdisciplinary research issues between geomechanics and geology.
We observed weathering and deformation behavior of weak geomaterials derived from mudstones or shales by a novel experimental technique, and we developed a rational constitutive model incorporating physical / chemical weathering.

Exploring the mechanism of liquefaction of UNSAT
We applied our model for unsaturated soils to simulate liquefaction of unsaturated soils, and investigated the conbined effects of saturation degree and density on the liquefaction potential.

Fig. : 3-dimensional surface of mean effective stress reduction ratio (this value goes to unity in case that liquefaction occurs) ( 3rd E-UNSAT, 2016; Int. J. Numer. Anal. Meth. Geomech., 2017)

Measurring risk against natural hazards
We developed an integrative index for risk against natural hazards and published this as Gross National Safety for natural disasters (GNS2015; GNS2017; GNS2019) with Japanese geotechnical society, Kanto branch.
Article report on the index is HERE. Introduction of this index is HERE. GNS2019 was introduced in Kentsuu News.

Fig. : GNS2015 published with JGS, Kanto branch (left) and multi-scale assessment of risks against natural hazards (right)

Dynamic behavior of soil-rock composite structure
We investigate the mechanisms of geohazards from the viewpoint of geomechanics and seek rational countermeasures.

Survey report on stone walls of Kumamoto castle damaged by 2016 Kumamoto earthquake is HERE.

Picture : Deformation of stone walls of Kumamoto castle detected by 3d laser scanner