Genki Kinugawa

Numerical simulation of consolidation characteristics of soft ground causing long-term land subsidence and residual subsidence of embankment

Ohtsuka Satoru

The Tohoku Expressway along the Sea of ??Japan is a highway with a total length of about 340 (km) from Niigata City to Aomori City. In Niigata prefecture, since the embankment was constructed on the soft ground without any countermeasures, the traffic was hindered by the influence of long-term subsidence after the service, and continuous maintenance and repair was unavoidable. However, the progress of subsidence has not stopped and is still continuing. Therefore, in this study, we will clarify the mechanism of long-term subsidence of the embankment in the study section (between Seiro-Shibata IC and Nakajo IC on the Japan Sea coast Tohoku Expressway) by numerical analysis (elasto-plastic consolidation deformation analysis). The purpose of this study is to clarify the consolidation characteristics of the local ground by loading repeated loads by a constant strain rate consolidation test.
First, in order to confirm how overlays and construction methods affect long-term embankment subsidence, a simulation of embankment subsidence was carried out using the elasto-plastic constitutive SYS cam clay model. The measured subsidence of the target embankment from the time of service to the present was 3.91 (m), and the subsidence by analysis was 3.92 (m), and the same results as the measured values ??were obtained. In addition, when the amount of embankment subsidence about 30 years from now was predicted by analysis, it was 4.02 (m), but the amount of embankment subsidence was not proportional to the logarithm of time and showed a behavior of converging to 4.02 (m). One of the reasons for this is that the SYS cam clay model does not consider secondary consolidation. Therefore, there is a possibility that subsidence will be larger than the amount of embankment subsidence obtained by analysis.
In recent years, long-term subsidence of soft ground due to groundwater level fluctuations has been confirmed. In the Hokuriku region, there are circumstances peculiar to snowy countries where groundwater is pumped up and used for snow removal, and groundwater level fluctuations are extremely large and cause continuous land subsidence. In order to understand the consolidation characteristics, a repeated consolidation test was conducted using a constant strain rate consolidation tester.