Aging of INSEM and INSEM structures in natural environments

Abstract

In recent years, there has been increased use of INSEM (in-situ stabilized excavated material)-based Sabo structures. Because INSEM is a low-quality material, one concern about structures built using INSEM is whether they will prematurely degrade in natural environments. There have been few investigative case studies, so it is currently impossible to clearly evaluate durability with regards to freeze-thaw cycles and so forth. The aim of this study was to provide information related to INSEM aging, durability, and degradation characteristics, based on the results of an aging study performed from 1999 to 2014 by test pieces and a structure at an altitude of 1300 m. The aging study investigated external appearance, compressive strength, relative dynamic modulus of elasticity, and mass loss rate. The lowest temperature at the site was －12.8℃, the freezing period was 91 days per year, and the observed materials were 8-15 years old, yet barring exceptional circumstances, no remarkable degradation due to freeze-thaw cycles or other meteorological phenomena was seen. The results of this investigation therefore suggest a low risk of degradation of INSEM and INSEM-based structures of this age due to the effects of meteorological phenomena such as freeze-thaw cycles. In other words, we confirmed that INSEM has sufficient durability to resist premature degradation under natural conditions for at least 8-15 years