The boundary integral equation method gives the efficiencies associated with the reduction of the dimensionality of a problem. This paper deals with the unsteady behavior of moving free surface and fresh-salt interface on the basis of the boundary integral equation method. The formulation and numerical discretization techniques for solving the dynamics of moving interface are explained, and theoretical results are compared with some experiments to examine the applicability of numerical computation. For the sake of practical use, two problems concerning an artificial land and rock cavern for stock piling are analized in coastal aquifers. As a result of serveral analyses, the applicability of boundary integral equation method for analyzing the moving interface as well as the characteristics of interface are confirmed.
In order to develop water resources in coastal areas, reservoirs have been planed and built on river mouth. Salt water intrusion through an aquifer due to the drawdown of water level in these reservoirs should be taken into consideration when reservoirs are constructed. One of the possible approaches for the prevention of salt water intrusion is to control its movement by artificial groundwater recharge. In the present paper, state equation which describes the movement of the tip of salt water wedge is derived through the boundary element method. And the optimal groundwater recharge rate from a culvert placed within the aquifer is determined by the optimal control theory. Some examples are demonstrated to confirm the availability of the proposed method.
The Kanto Loam is a deposit of the volcanic ash, and is widely distributed in the Kanto district. The purpose of this paper is to clarify the effects of tube-like macropores on hydraulic conductivities and on its anisotropy of the Kanto Loam. The permeability tester developed for this study was used to measure the anisotropy of conductivities. By using this device, it is possible to obtain the conductivities of two directions (vertical and horizontal) in one sample, simultaneously. Undisturbed soil samples for this measurements were taken at the outcrop in Kawasaki city in every 1 meters height. As a result, the following conclusions are obtaind. 1. The hydralic conductivities of the layer with many tube-like macropores is much larger than that of layer with few macropores. The magnitude of the difference is 10 times in horizontal direction and 100 times in vertical. 2. The anisotropy of the hydraulic conductivity is also much influenced by the effects of tube-like macropores. Without tube-like macropores, the ratios of Kv (vertical hydraulic conductivity) to Kh (horizontal one) range from 1.0 to 1.5, while with macropores, the ratios of Kv to Kh range from 3.0 to 20.