| Summary: | 碩士 === 國立高雄第一科技大學 === 營建工程所 === 96 === During rainfall,the rainfall water infiltrates into the unsaturated soil slope which results in an increase in soil water content,a decrease in soil matric suction and a decrease in shear strength to tigger the slope failures.At present,the research field of the unsaturated soil mechanics focused on application analysis and mechanics experiment,rather than influence from slope topography to the near-ground characteristics.
The matric suctions and volumetric water content of the soil along the depth at the upper and lower part of the slope were measured prior to and after the rainfall event.The matric suctions of the soil at a depth of 1.2m, 1.5m, and 2.7m were measured using jet-filled tensiometers, and those at a depth of 0.15m, 0.6m, and 0.9m were measured using the filter paper method because the matric suctions at the shallow depth were expected to be high and tensiometers are only capable of measuring the matric suction up to 90kPa;the volumetric water content is determined by the soil water monitoring in the backfill slopes of three different terrains(ridgelike slopes,flat slopes,and gullied slopes) and slope positions(up-slope,mid-slope,and toe),to find out the changes on matric suction and volumetric water content.Also it explores the influence of slope topography on the near ground characteristics of unsaturaterd soils subjected to rainfall.
The results show that,the matric suction is reduced with the decline of slope position，show slope the more influence flowed by runoff from top to botton.In addition,make the matric suction is the smallest of the ridgelike slopes and the flat slopes.As regards ridgelike slopes and flat slopes,drop of matric suction of slope position in difference of ridgelike slope is apparently smaller than flat slope，i.t.,ridgelike slope is influenced the more seriously that the flat slope is flowed by runoff from top to bottom.The unsaturated shear strength rise to increase with the matric suction,the stability of the ridgelike slope is that relatively the flat slope is good and the gullied slope is the worst.
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