Understanding the geochemical characteristics of various soils is significant for revealing the mechanisms occurring under natural conditions, assessing the environmental risks and managing the land use. However these various soils have complex forming mechanisms. This study examined geochemical characteristics of surface soils using statistical analysis. Principal component analysis (PCA), a very commonly used multivariate technique that can extract hidden structures and patterns from high-dimensional data, was applied to 633 classified soil samples. Soil samples collected in the Miyagi and Ibaraki prefectures were analyzed for major elements (Si, Ti, Al, Fe, Mg, Mn, Ca, Na and K) and heavy metals (Cr, Cu, Zn, As and Pb). Major elements showed most distinctive relationships with an inverse correlation between Si and Ti, Fe and Al. Heavy metals did not exhibit clear correlations with each other. However, background concentrations could be estimated using the frequency distribution and log-normal distribution curves. The background concentration of Cr, Cu, Zn, As and Pb were 50 ～150 mg/kg, 75 ～150 mg/kg, 200 ～300 mg/kg, 25 ～50 mg/kg and 30 ～60 mg/kg, respectively. Results of PCA clarified four common factors controlling major elements and heavy metals in the soil samples. They are ‘Physicochemical formation', ‘Soil components',‘ Vegetation effect' and ‘Adsorption and desorption'. Soils are formed by leaching reactions from rain and groundwater and mixed organic matter from different vegetation types. Therefore, major elements and heavy metals in soil are affected by these processes, which are common to most soil types.
Because blasting is a quite efficient and economical excavation method, it has been widely applied to tunnel excavation especially in hard rock. However, this method is rarely used to the tunnel site close to residential houses due to its environmental impact such as vibration and noise. Nowadays, the advanced electronic detonator, which was widely used in overseas mine site, was introduced to the tunnel site in Japan. This electronic detonator with accurate delay time (=ignition time difference between consecutive holes) has a potential to mitigate blasting vibration. In the past, many studies to lower the blasting vibration had been conducted and in some of them, several ways of simulation were implemented and the relations between vibration mitigation and arrangement of delay time were proposed. In this study, based on the past achievement and blasting test the authors had carried out, the appropriate method to determine the optimum delay time was proposed. In the case of electronic detonator in which each hole has different ignition time, the methods using autocorrelation and frequency analysis were found to be good expectation of delay time to lower the vibration. Also, in the case of conventional electric detonator in which ignition time has dispersion, the relation between vibration and ignition time dispersion was calculated, and the proper way to lower the vibration was proposed. This study gives practical method to set appropriate ignition time to lower blasting vibration.
One of the authors has developed a numerical simulator of airlift pump to solve governing equations represented by the drift flux model. The solver is based on the finite volume method which is known as SIMPLER algorithm for numerical scheme. The calculated results using the simulator were comparatively in good agreement with experimental ones by Weber et al. and Saito et al., despite lack of appropriate correlations used in the constitutive equations. In this study, the simulator is improved by a recent study (Ishii and Hibiki, 2011) on the constitutive equations of the drift flux model in the gas-liquid two-phase flow. The effect of newly incorporated correlations versus original ones in the constitutive equations is studied on the lifting characteristics such as relation between inputting air and lifted water. Also, flow characteristics along axial direction of pipes are examined to compare numerical results with experimental ones over wide range of pipe diameter and pipe length. Furthermore, pressure losses are grasped from the standpoint of the pump head, the relation between various pressure losses and lifting characteristics is discussed.