Estimation of Degree of Soil Reformation at Hillside Work Areas by Principal Component Analysis

Abstract

For estimating the effects of hillside works on soil reformation, undisturbed and disturbed soil samples were collected from a hillside works and their circumferences in granite region. Soil properties such as soil pH, total carbon content, total nitrogen content, solid ratio, specific gravity, volume of non-capillary pore (<pF1.8), volume of coarse capillary pore (pFl.8-2.7), volume of fine capillary pore (pF2.7 <), sand particle content (0.074-2 mm in diameter) and fine fraction content (0.074 mm> in diameter) were measured. Comparing the individual soil property of both areas in relation to the lapsed years after hillside works, it was judged that the soils on the hillside work areas would gradually approach those on their circumferences (KUM-LUNG, and TAKEDA, 1991). In this paper, to estimate the soil reformation synthetically, the soil properties are subjected to principal component analysis. Results showed that principal component analysis was a useful method to estimate the degree of soil reformation at the hillside work area. Besides, it was confirmed that solid ratio and total carbon content were closely related to the degree of soil reformation at the hillside work areas. Kumlung et al.: Estimation of Degree of Soil Reformation at Hillside Work Areas by Principal Component Analysis lapsed years after hillside works (NAKASHIMA et al., 1969, and TSUTSUMI, 1963). KUMLUNG, and TAKEDA (1991) reported that each chemical and physical soilproperty on hillside work-sites would gradually approached those on their circumferences with the lapsed years after hillside works. Beside this, KUM-LUNG et al. (1991) also reported that the changes in soil properties on hillside work-sites were influenced by topographic factors such as bearings and altitudes. Generally, the interpretation of soil reformation requires simultaneous consideration of a number of soil properties. KOSAKI, and JUO (1988) stated that principal component analysis is a mathematical technique used to summarize data and investigate the relationships among variables. In this study, the principal component analysis (KENDALL, 1980) was employed to summarize the data in order to estimate the degree of soil reformation at hillside work areas.