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標題: 石門集水區優勢植物根系形態調查及其拉拔抗力與抗剪強度之力學轉換模式建置
Investigations of Root Morphology of Predominant Plants in Shi-Men Watershed and Their Mechanical Transform Model from Pull-Out Resistance to Shear Strength Increment
作者: 林德貴
關鍵字: 土木水利工程類, 水土資源保育;應用研究;Root morphology;根系形態;極限拉拔抗力;三維數值模型;抗剪強度增量;力學轉換模式;Ultimate pull-out resistance;Three dimensional numericalmodel;Shear strength increment;Mechanical transform model
本研究將針對石門水庫集水區崩塌地之優勢鄉土植物,包含山芙蓉、九芎、構樹、山鹽菁、山黃麻等5 種植物進行現地根系形態(morphology)之調查、室內根系強度試驗及現地根系拉拔抗力試驗。根系形態之主要項目包括:主根長Lr-tap(length of tap root)、分枝角度(branching angle)、側根數目nr-lat(number of lateral root )。根據根系形態現地調查成果,可建立各種根系之三維數值模型。植物根系數值模型的排列與配置型式,將決定植物抗拔的能力。利用含根土之三維數值模型,並參照現地拉拔試驗之加載方式(採用拉拔力加載控制方式),可進行根系現地拉拔抗力試驗之數值模擬。根據模擬結果,分析其拉拔歷程並比對拉拔抗力-拉拔量關係曲線之量測值與模擬值之吻合度,即可確定數值模擬程序之有效性。本研究期望採用簡單的根系幾何形狀及多樣的數值模擬技巧,來檢核根系形態對其錨碇力的影響。隨之,再採用與根系拉拔抗力試驗數值模擬相同之三維數值模型,進行含根土之直接剪力試驗數值模擬,並推估含根土根系抗剪強度增量值ΔSr。最後,即可建置上述5種植物之根系形態、極限拉拔抗力Pu 與土~根系統抗剪強度增量ΔSr 之力學關係式,即ΔSr=f(Pu, Lr-tap, , nr-lat)關係函數。最後,再將此根系力學轉換模式結果,運用於植生邊坡三維穩定性分析中,並評估不同植物根系對邊坡土層之加勁效果。

In this study, a systematic field survey are performed to investigate the root morphologyof five predominant plants, namely: (1) Hibiscus taiwanensis S. Y. Hu, (Taiwan hibiscus), (2)Lagerstroemia subcostata Koehne (Subcostate crape myrtle), (3) Broussonetia papyrifera(Paper mulberry), (4) Rhus javanica L. var. Roxburghiana (Roxburgh sumac) and (5) Tremaorientalis L. (Blume, Indiacharcial trema) at the local landslide area of Shi-Men watershed.The root morphology can be expressed in terms of length of tap root (Lr-tap), branching angleof lateral root () and the number of lateral root (nr-lat). In addition, the tensile strength ofvarious root materials from laboratory test and their pull-out resistance from field test are alsocarried out in the associated testing program.Based on the field investigations of root morphology, one can establish a threedimensional (3-D) numerical model of soil~root system to simulate the pull-out test of plantroot in soil~root system. The arrangement and layout of the plant root in soil~root systemdetermines the capability of pull-out resistance of the plant root. Using the 3-D numericalmodel of soil~root system, the numerical modeling of pull-out test of the plant root can beperformed according to the manner of pull-out force applied in the field site (or pull-out forceloading control). Through the comparison of simulated pull-out mechanical behaviors withthose from measurements, the effectiveness of the proposed 3-D numerical procedures can beverified. Further, the influence of root morphology on the pull-out or anchorage resistance ofthe plant root is also examined through a simple pattern of root system and versatilenumerical modeling techniques in this study.Subsequently, a 3-D numerical model of soil~root system identical with the pull-out testis repeatedly used for the simulation of direct shear test to estimate the shear strengthincrement, ΔSr, contributed by the plant root in soil~root system. For the aforementioned fivepredominant plants in Shi-Men watershed, based on the numerical results a general equationof mechanical transform model, ΔSr=f (Pu, Lr-tap, , nr-lat), can be formulated and used totransform the ultimate pull-out resistance Pu into the shear strength increment ΔSr of soil~rootsystem. Eventually, this model is applied to 3-D slope stability analysis to evaluate the effectof reinforcement of various plant roots in the slope of watershed.
其他識別: NSC98-2221-E005-088
Appears in Collections:水土保持學系

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