Groundwater reservoirs aim at saving grounding water from aquifers by means of interception and adjustment. This study adopts numerical model simulation to evaluate the benefit of developing subsurface reservoirs and provides the case of the groundwater reservoir development at Daping region in Dongju Island. Since 2008, this study has been conducting surface geological surveys, geological drilling, surface infiltration experiments, physical experiments on bore specimens, and continuous observation of groundwater level while simultaneously conducting water pumping and slug tests in the field in order to estimate the hydro geological parameters of the site. The development benefit assessment of the groundwater reservoir will also include catchment area, surface land use, calendar year rainfall records and other information. Meanwhile, the FEMWATER numerical model of groundwater will be used to conduct hydrodynamic simulations of the development area. According to the simulation results of pre and post construction of the cut-off wall of the groundwater reservoir, this study could estimate the stable pre and post water volume and the development benefit of the groundwater reservoir can be assessed. According the 3-year unsteady numerical simulation, the results show that the groundwater reservoir can provide approximately 36 m3/day of stable water supply during dry seasons. If a cut-off wall is implemented and the stable water supply could increase 11% to 40 m3/day and raise the average upstream groundwater level of the cut-off wall by 1m, it clearly displays the benefit of the cut-off wall.

Unsaturated cracked slopes are easily to be affected by rainfall in the soil. Actually, some of the rainfall becomes the surface runoff and the rest permeates the crack under the ground in water cycle system. The infiltration makes the groundwater level rise. It also increases the pore water pressure and slide stress of the soil and decreases the anti-shear strength of soil. That makes the slope fracture or deform. However, most of the slope stability analyses set the physical properties of the soil as constant values but neglect the influence of the crack and infiltration. Those analyses underestimate the influence of the crack and the change of water content to the anti-shear strength of the soil. Therefore, it was unable to predict the possible damage time point by these evaluation results. The knowledge and methodology of the rainfall combine infiltration and slope stability analysis in this research. Simulations of the moisture content of the soil and the groundwater level are performed by FEMWATER numerical model. The simulating conditions are based on the different cracked positions and rainfall durations. The data of moisture content changes of the soil will be transformed into the parameters of safety factors fitted by STEDWIN numerical model. The influence of the slope stability with different cracked positions was gained from the simulations.

The Southern Taiwan Science Park (STSP) is located between Hsinshi Township and Shanhua Township of Tainan County, with the newly-built, high-speed railway running through its eastern side. The low-frequency vibration which was generated by passing high-speed trains causes environmental disturbances to industries within the Park. To address this issue, the implementation of vibration-reduction project with detailed design and construction was provided. The diaphragm wall-type vibration reduction walls will be built along the borderline between Hsinshi Township and Shanhua Township to reduce the impact on industries. The diaphragm wall structure will block groundwater from flowing to affect the underground hydrology. This study was aimed to discuss and assess the best configuration for the vibration reduction effects and environmental impacts. Numerical analysis of the impacts on groundwater hydrology was conducted in two cases. The simulation results indicated that both sides of diaphragm walls developed gaps in groundwater levels. Hence, diaphragm walls effectively reduced adverse impacts on groundwater hydrology with openings at locations where underground pipelines ran. Such variations were within the scope of groundwater level of high water and low water periods. Therefore, surface runoff and land subsidence resulting from the diaphragm wall construction were not severe. As diaphragm walls were made of impermeable materials, pumping water nearby made the groundwater level drawdown effects worse. Groundwater level variations resulting from pumping water were far greater than the regional groundwater level variations after the establishment of diaphragm walls. Special attention must be paid to this situation in follow-up management.

In this study, the slope piping experiment selected 6 different sands in mining engineering of civil construction. In addition to discussing the physical parameters of the graded sands in mining engineering, the piping destruction parameters of different slopes were obtained from the experiment. When piping occurs, we can use numerical model to get the hydraulic gradient value at the failure point. The difference between the theoretical estimation and the numerical model was compared and we found that different particle size distribution caused the main difference. The particle size parameter ratio, D*, is used for correcting the critical hydraulic gradient value in this study. We learned the correction coefficient of D* is between 0.5~0.857 in different tests and its value approximates the reciprocal of the coefficient of uniformity. Therefore, the critical hydraulic gradient estimation formula for the slope piping of the uniform sand can be future corrected, and it can be used for estimating the graded sand in this study. In civil engineering the sand filling project can use the estimation formula of this study to calculate the critical hydraulic gradient as the reference for design and disaster prevention.