梳子壩在土石流作用下之三維數值分析

Three Dimensional Numerical Analyses of Slit Dam Subjected to Debris Flow

10.29417/JCSWC.201003_41(1).0003

林德貴(Der-Guey Lin)；黃伯舜(Bor-Shun Huang)；黃隆明(Long-Ming Huang)

梳子壩 ； 三維有限元素 ； 三維數值模型 ； 撞擊力 ； 壩柱寬度與壩柱開口寬度比 ； slit dam ； 3-D finite element ； 3-D numerical model ； impact force ； ratio of the width of slit column to the open size of slits

中華水土保持學報

41卷1期（2010 / 03 / 01）

49 - 60

簡體中文

This study selects the No. 5 slit dam (gravity dam) situated at the Song-He No. 1 creek, Bo-Ai village, He-Ping, Taichung County as a case history for structural analysis. By maintaining the dam height (or slit column height) unchanged and the configuration meets the design criteria, four sets of fictitious slit dam were analyzed under different column width/open size ratios or (D/L) ratio (D/L=0.667~0.683). Where, D and L represent the width of slit column and the open size of slit respectively. Three dimensional (3-D) static structural analyses were performed on slit dam under various loading conditions, namely Case 1~Case 4, in which, Case 1 (Condition 1: debris accumulates at the upstream of slit dam, and Loading 1: driven force from none to a value induced from the action of debris flow), Case 2 (Condition 2: slit dam is filled up by debris, and Loading 2: the maximum earthquake loading is applied), Case 3 (Condition 3: slit dam is filled up by debris at the upstream, and Loading 3: debris flow overflows) , Case 4 (Condition 4: slit dam is nearly occupied by debris flow at the upstream, and Loading 4: the impact force induced from the large boulder is applied). Meanwhile, through the analyses, the effect of (D/L) ratio, the stress and displacement distribution of dam body are also investigated. The numerical results indicate the ratios of the maximum bending tensile stress +σ(subscript yy), maximum bending compressive stress-σ(subscript yy) and maximum shear stress σ(subscript yz) of slit column to their allowable values of concrete, σ(subscript t), σ(subscript c) andσ(subscript s) are: For (+σ(subscript yy)/σ(subscript t)): Case 1 (17.94%)＞Case 3 (5.78%)＞Case 2 (0.12%). For (σ(subscript yy)/ σ(subscript c)): Case 1(2.86%)＞Case 3 (1.95%)＞Case 2 (1.51%). For (σ(subscript yz)/ σ(subscript s)): Case 1(6.93%)＞Case 3(2.76%)＞Case 2(0.93%). Finally, according to the numerical results, the ratio of the maximum tensile stress to the allowable tensile stress of concrete (σ(subscript yy)/σ(subscript t)) and the ratio of the maximum shear stress to the allowable shear stress of concrete (σ(subscript yz)/σ(subscript s)) in slit column are increased from 0.53 to 0.80 (about 51% increment) and from 0.48 to 0.71 (48% increment) respectively if the impact force is carried by two slit columns instead of three. These imply that the tensile stress and shear stress induced from impact force will be much closer to their allowable values if the force is distributed to two slit column rather than three. As a consequence, to achieve a beneficial and efficient utilization of material strength in stress analyses of slit dam for debris flow impact force, it is suggested to assume that the impact loading is simply taken by two slit columns.

This study selects the No. 5 slit dam (gravity dam) situated at the Song-He No. 1 creek, Bo-Ai village, He-Ping, Taichung County as a case history for structural analysis. By maintaining the dam height (or slit column height) unchanged and the configuration meets the design criteria, four sets of fictitious slit dam were analyzed under different column width/open size ratios or (D/L) ratio (D/L=0.667~0.683). Where, D and L represent the width of slit column and the open size of slit respectively. Three dimensional (3-D) static structural analyses were performed on slit dam under various loading conditions, namely Case 1~Case 4, in which, Case 1 (Condition 1: debris accumulates at the upstream of slit dam, and Loading 1: driven force from none to a value induced from the action of debris flow), Case 2 (Condition 2: slit dam is filled up by debris, and Loading 2: the maximum earthquake loading is applied), Case 3 (Condition 3: slit dam is filled up by debris at the upstream, and Loading 3: debris flow overflows) , Case 4 (Condition 4: slit dam is nearly occupied by debris flow at the upstream, and Loading 4: the impact force induced from the large boulder is applied). Meanwhile, through the analyses, the effect of (D/L) ratio, the stress and displacement distribution of dam body are also investigated. The numerical results indicate the ratios of the maximum bending tensile stress +σ(subscript yy), maximum bending compressive stress-σ(subscript yy) and maximum shear stress σ(subscript yz) of slit column to their allowable values of concrete, σ(subscript t), σ(subscript c) andσ(subscript s) are: For (+σ(subscript yy)/σ(subscript t)): Case 1 (17.94%)＞Case 3 (5.78%)＞Case 2 (0.12%). For (σ(subscript yy)/ σ(subscript c)): Case 1(2.86%)＞Case 3 (1.95%)＞Case 2 (1.51%). For (σ(subscript yz)/ σ(subscript s)): Case 1(6.93%)＞Case 3(2.76%)＞Case 2(0.93%). Finally, according to the numerical results, the ratio of the maximum tensile stress to the allowable tensile stress of concrete (σ(subscript yy)/σ(subscript t)) and the ratio of the maximum shear stress to the allowable shear stress of concrete (σ(subscript yz)/σ(subscript s)) in slit column are increased from 0.53 to 0.80 (about 51% increment) and from 0.48 to 0.71 (48% increment) respectively if the impact force is carried by two slit columns instead of three. These imply that the tensile stress and shear stress induced from impact force will be much closer to their allowable values if the force is distributed to two slit column rather than three. As a consequence, to achieve a beneficial and efficient utilization of material strength in stress analyses of slit dam for debris flow impact force, it is suggested to assume that the impact loading is simply taken by two slit columns.