STUDY ON LONG-TERM SUBSIDENCE OF SOFT CLAY DUE TO 2007 NIIGATA PREFECTURE CHUETSU-OKI EARTHQUAKE

Long-term subsidence has been observed in Kashiwazaki City after the 2007 Niigata Prefecture Chuetsu-Oki Earthquake. The present study was conducted to investigate the mechanism of this long-term subsidence through ground investigations in the form of a boring survey and laboratory tests on soil samples. The results showed that the samples were very soft and relatively highly structured. In the study's second part, ground subsidence was simulated via soil-water coupling elasto-plastic FE analysis. In the simulation, the Cyclic Mobility model developed by Zhang et al. (2007), which incorporates the concepts of subloading and superloading used as the constitutive model with parameters determined in line with the laboratory test results. Based on the outcomes of the simulation, the post-quake behavior of soft clay and the related mechanism were elucidated, and the progress of subsidence was predicted.