3:50 PM - 4:05 PM
[SEM15-02] Investigation of the condition of embankments buried in peaty ground using geophysical exploration and geophysical logging, and a study of the electrical properties of peat
Keywords:electrical prospecting, electromagnetic sounding, electrical logging, peat
1. Introduction
In Hokkaido, peaty ground is widely distributed, and embankments are constructed and used on such ground. When materials such as sandy soil are used for the embankment, the groundwater level is high due to compaction, which leads to liquefaction and large embankment failures during earthquakes. Therefore, it is important to know the distribution and thickness of saturated embankment areas, which may be weak points of embankments, qualitatively, in a wide and continuous manner.
In this report, a simple method to determine the saturated area of embankments in peaty ground is discussed, in which geophysical exploration is added to conventional ground investigation methods and the results are compared.
2. Research field
Two embankments for snow protection forested, one with coarse-grained embankment (hereinafter referred to as “coarse-grained embankment”) and the other with fine-grained embankment (hereinafter referred to as “fine-grained embankment”), were investigated on peaty ground in Hokkaido, Japan.
3. Research methodology
In this study, geophysical exploration was conducted to compare and evaluate the right information on embankment and peat obtained by conventional geotechnical investigation methods. Conventional geotechnical investigation methods include borings, standard penetration tests, and electrical logging. The geophysical exploration was conducted by electrical Resistivity Tomography and Electromagnetic method. Geophysical explorations were conducted in the longitudinal direction for both coarse-grained and fine-grained embankments at the center of the embankment crown and at three measuring lines (30 m/line) on the left and right sides. The line at the center of the embankment is referred to as line C, and the lines on the left and right are referred to as lines L and R, respectively.
In Hokkaido, peaty ground is widely distributed, and embankments are constructed and used on such ground. When materials such as sandy soil are used for the embankment, the groundwater level is high due to compaction, which leads to liquefaction and large embankment failures during earthquakes. Therefore, it is important to know the distribution and thickness of saturated embankment areas, which may be weak points of embankments, qualitatively, in a wide and continuous manner.
In this report, a simple method to determine the saturated area of embankments in peaty ground is discussed, in which geophysical exploration is added to conventional ground investigation methods and the results are compared.
2. Research field
Two embankments for snow protection forested, one with coarse-grained embankment (hereinafter referred to as “coarse-grained embankment”) and the other with fine-grained embankment (hereinafter referred to as “fine-grained embankment”), were investigated on peaty ground in Hokkaido, Japan.
3. Research methodology
In this study, geophysical exploration was conducted to compare and evaluate the right information on embankment and peat obtained by conventional geotechnical investigation methods. Conventional geotechnical investigation methods include borings, standard penetration tests, and electrical logging. The geophysical exploration was conducted by electrical Resistivity Tomography and Electromagnetic method. Geophysical explorations were conducted in the longitudinal direction for both coarse-grained and fine-grained embankments at the center of the embankment crown and at three measuring lines (30 m/line) on the left and right sides. The line at the center of the embankment is referred to as line C, and the lines on the left and right are referred to as lines L and R, respectively.