Investigation on the correlation between the time factor in the hydrological behavior of residual soil slopes and the rainfall characteristics

• Main Authors: Hsu-wei Chang, 張旭葳
• Other Authors: Chia-cheng Fan(范嘉程)
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/34240665771205702353

碩士 === 國立高雄第一科技大學 === 營建工程研究所 === 102 === This study examined the moisture contained in the unsaturated weathered shale residual soil slopes with emphasis on the distribution of soil moisture content in different time and in different locations in order to identify the correlation between time factors and hydrological behaviors during the rainfall period. A natural slope covered with miscellaneous woods located in Jiasian District, Kaohsiung City, was selected as the experiment site, automatic surveillance method was adopted, soil moisture sensors were buried in various spots with different altitudes and different depths to measure soil moisture content over a long period of time, rainfall data was measured in situ, and nine rainfalls were chosen for quantitative analysis. After the correlation between the time factors and rainfall characteristics was analyzed, the research results indicated that, as far as the typical weathered soil slopes with different rainfall types and different altitudes are concerned, rainfall types influenced the average rainfall intensity as well as the corresponding accumulated rainfall. When the rainfall has a low degree of intensity, the arrival time of water front in all depths (Ts) and the arrival time of unsaturated soil’s shearing force at least value (Te) slow down. After various altitudes were analyzed, the research results indicated that the soil moisture content in shallow layer (1 meter or less below the ground) varies more than the soil moisture content in all other layers. In this connection, the distribution of soil particles influences the soil moisture content the most, particularly the coarse-grained soil. Secondly, the moisture content increase rate (Rm) of antecedent soil moisture content changes in accordance with the distribution of rainfall intensity; the distribution of rainfall types and rainfall intensity substantially influence the time of destruction to the slopes. Therefore, the accumulated rainfall alone is not sufficient for issuing alert. Thirdly, after typical slopes were compared with trench slopes regarding their distributions of moisture content increase rates, the research results indicated that the typical slopes did not reveal any significant difference associated with the altitudes; trench slopes collect rainwater and underground water, and thus develop differently in different latitudes. Based on the results acquired through in situ observations and the comprehensive terrains and environment of the experimental slopes, this study presents practical recommendations for the early warning required by the potentially dangerous slopes.