陳榮河2006-07-252018-07-092006-07-252018-07-092002http://ntur.lib.ntu.edu.tw//handle/246246/2796土石流之發生機制與土石材料之力學 性質有十分密切的關係，本研究係針對台 北縣金山鄉重和地區三和溪之土石堆積區 進行現地採樣與粒徑分析，並進行多項室 內試驗以了解土石材料之特性；研究方法 採用等重量替代法模擬現地土壤之級配曲 線，並對模擬之土樣進行三軸透水試驗、 土壤水分特性曲線試驗、飽和均向壓密不 排水三軸試驗，以及土樣於不飽和狀態下 之壓密排水三軸試驗，期望藉由不同試驗 結果，能對土石材料之基本力學性質、透 水性質以及保水特性更進一步的瞭解；此 外，由試驗結果與現地相關資料，對災害 發生之原因進行探討。 粒徑分析結果顯示三和溪土樣之礫石 含量佔77.1%，200 號篩以下含量為5%； 依統一土壤分類法屬於GP，為以礫石為主 體之土壤。土石材料之透水係數皆約10-3 cm/sec。由於礫石土壤之細料含量少，因此 土壤水份特性曲線試驗結果顯示，其保持 水分能力不佳。而飽和均向壓密不排水三 軸試驗結果顯示，三和溪土樣之內摩擦角 隨最大粒徑之增大而降低，而土樣因相對 密度較高有受剪膨脹之行為；土樣於不同 級配條件及相對密度下之c’、ψ’分別為 4kPa、0.4kPa 以及36.9°、38.7°。此外，土 樣於不飽和狀態下之壓密排水三軸試驗結 果顯示，土樣之剪力強度隨著基質吸力增 加而上升，當基質吸力增加至75kPa 時， 強度上升幅度則會趨於平緩；由試驗結果 發現，基質吸力與土壤總凝聚力間之關係 為非線性。 由試驗結果與現地之相關資料得知， 現地之土石材料在降雨強度高之情況下， 表層之飽和度會因雨水的累積而快速上 升，使得剪力強度快速下降，造成土體之 穩定性降低，進而發生破壞。The initiation of debris flows is very much affected by soil properties. The study site is at the upstream of Shanher Creek, located at Chinshan in Taipei County. Samples were taken from the site and their grain size distributions were determined. However, due to limitation of specimen size in the laboratory, simulating the field grain size distribution by the “weight replace method” was adopted. Tests were carried out on the simulated samples to obtain the mechanical properties of the soil as well as hydraulic properties. The tests performed include isotropically consolidated undrained triaxial (CIU) test, triaxial permeability test, soil-water characteristic curve, and consolidated drained triaxial (CD) test on unsaturated soil sample. According to the grain size distribution of the soil, it contains 77.1% gravels and only 5% fines. It is composed mainly of coarse materials with non-plastic fines and is 2 classified as GP by the Unified Soil Classification System. Because of coarse particles, the soil has low water retention ability as determined by the soil-water characteristic curve test. The permeability test shows that the permeability of the soil decreases with increasing confining pressure, but the difference is not significant. The CIU test shows higher friction angles for the soils with smaller maximum particle size. The CD test on unsaturated samples shows that shear strength increases with matric suction, but levers off when the matric suction being over 75 kPa. The relationship between the shear strength and the matric suction is nonlinear, thus fb is not a constant. Finally, based on the above soil properties, heavy rainfall was very likely to saturate quickly the surface zone of the slope on site and caused the slope unstable or even failed.application/pdf139392 bytesapplication/pdfzh-TW國立臺灣大學土木工程學系暨研究所邊坡破壞不飽和土壤土壤水分特性曲線剪力強度slope failureunsaturated soilsoil-water characteristic curveshear strengthreporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/2796/1/902625Z002023.pdf