Soil Water Characteristic Curve of the Weathered Granite Soil through Simulated Rainfall System and SWCC Cell Test

A simulated rainfall system was built, and the unsaturated characteristics were examined by execution of simulated rainfall system test and soil water characteristic curve cell test(SWCC Cell Test) under the various rainfall and slope conditions. With the results, the applicability of infiltration behavior under rainfall and soil water characteristic curve models to the unsaturated weathered granite soil was examined. At the results of comparison the volumetric water content and matric suction measured in the wetting process(under rainfall) with those in the drying process(leaving as it was) of the simulated rainfall system, the volumetric water content showed a difference of $2{\sim}5%$ and matric suction of about $3{\sim}10\;kPa$, indicating the occurrence of hysteresis. In addition, the difference was relatively larger in matric suction than in the volumetric water content, and this tells that the hysteresis behavior is larger in matric suction. When the soil water characteristic curve derived from measurements in simulated rainfall system test were compared with those from the soil water characteristic curve cell test, both methods produced soil water characteristic curves close each other in the wetting process and the drying process, but in both, there was a difference between results obtained from in the wetting process and those from in the drying process. Thus, when soil water characteristic curves are rationally applied to the design and stability analysis considering of the properties of unsaturated soil, it is considered desirable to apply the soil water characteristic curve of the wetting process to the wetting process, and that of the drying process to the drying process.

강우재현 모형실험과 SWCC Cell 실험에 의한 화강암질 풍화토의 함수특성곡선

강우재현장치를 제작하고, 강우 및 사면조건에 따라 강우재현 모형실험과 함수특성곡선실험(SWCC Cell Test)을 실시하여 불포화 특성에 관해 연구하였다. 그 결과를 이용하여 강우에 따른 침투거동 특성과 함수특성곡선 모델들의 불포화된 화강암질 풍화토에 대한 적용을 검토하였다. 강우재현 모형실험의 습윤과정(강우재현)과 건조과정(방치)에서 계측된 체적함수비와 모관흡인력을 비교한 결과 체적함수비는 $2{\sim}5%$, 모관흡인력은 $3{\sim}10\;kPa$ 정도 값의 차이를 보여 이력현상을 확인 할 수 있었다. 또한, 모관흡인력의 값이 체적함수비의 값에 비해 상대적으로 큰 차이를 보여 모관흡인력에 이력거동이 더 큼을 확인할 수 있었다. 강우재현 모형실험과 함수특성곡선실험에서 얻은 결과로부터 구한 함수특성곡선을 비교하면, 습윤과정과 건조과정에서 두 방법 모두 근접한 함수특성곡선을 얻을 수 있었으나, 두 방법 모두 습윤과정과 건조과정에서의 결과는 차이가 있었다. 이로써 불포화토의 특성을 고려한 보다 합리적인 설계나 안정검토에 함수특성곡선을 적용시킬 때에는 습윤과정에서는 습윤과정 함수특성곡선을 건조과정에서는 건조과정 함수특성곡선을 적용하는 것이 합당할 것으로 여겨진다.