Atsushi Iizuka

Coupled chemical-hydraulic-mechanical modelling of long-term alteration of bentonite

Abstract In order to evaluate the long-term behaviour of the engineered barriers in geological disposal sites for transuranic element-bearing (TRU) waste, an evaluation by numerical analysis is required. Although chemical and hydraulic/mechanical analyses have been conducted independently until now, essentially both type of phenomena occur simultaneously and produce synergistic effects. Therefore, we focused attention on the buffer (bentonite) engineered barrier and conducted a study of which involved incorporating hydraulic/mechanical phenomena into the chemical analysis of bentonite alteration. The simulations employed weakly-coupled chemical and hydraulic/mechanical effects to study the behaviour in one dimension. The results showed that the dissolution of the montmorillonite is suppressed in the buffer section nearest the cement material. Moreover, in order to achieve a fully coupled analysis in future, the present study also identifies issues that need to be resolved.

Simulations of Static Compaction with Soil/Water/Air Coupled F.E. Analysis

Most man-made, onshore earth structures are constructed by compaction. Optimum compaction can increase strength and decrease compressibility and permeability. However, the compaction mechanism remains to be defined in soil mechanics and there is no alternative but to apply empirical methods at the geotechnical engineering site. In this study, compaction is assumed as compression of unsaturated soil under water-undrained and air-drained conditions, and the compaction simulation is conducted with soil/water /air coupled finite element analysis. Consequently, the shape of the compaction curve can be drawn on the coordinates of water content and dry density. Moreover, direct shear simulation of the specimen obtained from compaction simulation was also conducted.

Geotechnical Predictions and Practice in Dealing with Geohazards

Prologue - 40 years Contributions to Geotechnical Engineering of Prof Hideki Ohta.- Part 1: Geotechnical Aspects of Some Recent Disasters.- 1. Tsunami induced by 2011 Tohoku-Pacific Ocean earthquake and a possible renewal plan.- 2. Tsunami Damages: what is unexpected? - 3. Past Earthquakes in Indonesia and New Seismic Hazard Maps for Earthquake Design of Buildings and Infrastructures.- 4. Lessons learned from the recent natural disasters in Indonesia.- 5. Behaviour of slope protection and retaining structures during the 2008 Wenchuan Earthquake in China.- Part 2: Geotechnical Predictions.- 6. Consolidation and Creep Settlement of Embankment on Soft Clay: Prediction versus Observation.- 7. Numerical Simulation of Soil Structures Reinforced by Geosynthetics.- 8. Deformation Prediction of a Structure Placed on Soft Clay in Tokyo Bay Affected by Heavy Deep Well Pumping.- 9. Elasto-Plastic FEM Analysis and Safety Evaluation of Large Rockfill Dams during Reservoir Filling.- 10. Three Dimensional Soil/Water Coupled Analysis of Reverse Concreting Excavation Work.- 11. Spatial Discretization of Water Head in Soil-water Coupled Finite Element Analysis using HPM.- 12. Theoretical Analysis for Non-coaxiality of Toyoura Sand.- 13. Threshold of Friction Stabilizes Self-weight Transmission in Gravitating Loose Sand Heaps.- 14. Elasto-Plastic Constitutive Model for Unsaturated Soils with Subloading Surface Concept.- 15. Stress-Strain Relationship for the Singular Point on Yield Surface of Elasto-Plastic Constitutive Model and Quantification of Metastability.- 16. Analysis of the Earth Pressure Problems by Upper and Lower Equilibrium Method.- Part 3: Geotechnical Practices in Dealing with Geo-hazards.- 17. Railway Old Station Building: Enlargement and Underpinning.- 18. Analysis of slope stability and landslide in seismic activity regions.- 19. Recent Developments of PVD Soft Ground Improvement: Laboratory Test Results and Simulations.- 20. Study on Regional Ground Upheaval Phenomenon caused by the Rising of Groundwater Level and its Effect on Underground Infrastructure.- 21. A Robust Control Approach for Decision Making and Reliability Design of Soil Structures.- 22. Development of a Portable Triaxial Testing Apparatus -Smart Triaxial.- 23. Innovation in Disaster Mitigation Technologies.- Index.