Geotechnical approaches for preservation of openly exhibited Geo-relics damaged by rainfall infiltration

Abstract

Excavated geo-relics are vulnerable to damage by natural processes. The aim of this study is to contribute to the establishment of a technical framework for the preservation of openly exhibited geo-relics. This study also examines the preservation of an openly exhibited geo-relic in Japan, which has experienced surface deformation in the soft soil layer due to water infiltration. The surface deformation is numerically investigated by performing seepage-deformation analyses based on unsaturated soil mechanics in order to understand its mechanism and to obtain effective countermeasures. The results show that deformation develops in the surface layer of the slope as the bonding between soil particles, represented by skeleton stress, and decreases when water infiltrates the slope. Although the calculation considers the influence of groundwater, as well as precipitation, the results show that the deformation of the slope is primarily controlled by precipitation, not by groundwater. Furthermore, the elevation of the groundwater does not contribute to the development of surface deformation. Based on the mechanism of the surface deformation, replacing the surface layer with a well-compacted, highly permeable soil is proposed to improve slope stability. It is predicted that this proposed method will be effective because the replaced zone retains sufficient strength and stiffness when it is wet, despite a decrease in the skeleton stress due to rainfall infiltration. This countermeasure has been adopted for the actual restoration of a damaged slope.