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  • 學位論文

以FLAC程式探討剛性擋土牆於不同位移型式之側向土壓力分佈

Study on the Lateral Soil Pressure Distribution Behind a Rigid Retaining Wall subjected to Different Displacement modes Using FLAC

指導教授 : 馮道偉 葛德治
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摘要


擋土牆為土木工程中常見之擋土結構系統,應用於穩定及擋護由挖掘或填築而成之永久性岩面,而為了能設計安全又符合經濟效益之擋土牆,必須要能先預測有多少側向土壓力作用於擋土牆上,以及擋土牆後側向土壓力分佈情形。側向土壓力對於擋土牆型式及結構設計上為一重要之輸入值,側向土壓力之設計值現今普遍使用Rankine & Coulomb於剛性擋土牆之理論解。而影響側向土壓力分佈之因子有擋土牆、背填土材料特性、擋土牆與背填土間之界面特性、背填坡角傾角、額外動靜力加載、及地下水位等;而傳統理論解只考慮簡單及理想情況,並未考慮到這些複雜情況。 因此本文擬採用FLAC程式,其能精確考量背填土之變形行為及在複雜狀態下來探討擋土牆後土壤之互制行為。本論文首先考慮背填坡傾角α= 0°時,分別探討兩種背填土壤於三種不同擋土牆位移型式下之主動/被動側向土壓分佈及滑動破壞面情形。三種不同擋土牆位移型式有:1) 對牆底旋轉 (RB移動型式):即擋土牆之側向位移以線性漸增;2) 牆平移 (T移動型式):即擋土牆之側向位移等距增加;3) 對牆頂旋轉 (RT移動型式):擋土牆之側向位移呈線性漸減等三種類型。並考慮背填坡傾角α≠ 0時之情況,探討α=5°、α=10°及α=15°時之情況,以FLAC程式計算擋土牆後之側向土壓力分佈及滑動破壞面情形。並探討背填坡傾角α≠ 0時之極限破壞背填坡傾角之情形。並和方永壽與Ishibashi於主動狀態下之模型實驗解比較。 結果顯示FLAC數值解之側向土壓力在RB移動型式下非常接近Rankine & Coulomb之理論解,T移動型式次之,RT移動型式差異最大;破壞滑動面在RB移動型式及T移動型式為直線,在RT移動型式較接近螺線;而擋土牆後側向土壓力之合力作用中心,RB與T移動型式較接近Rankine理論解,RT移動型式則差異較大。與方永壽之模型實驗比較,當接近極限狀態時兩者較為接近。

並列摘要


A retaining wall is the common structure system in civil engineering. It is applied in fixing and protecting excavated or filled rocks. In order to design safety and economical retaining wall, we need to predict how much lateral soil pressure and its distribution will act behind a retaining wall. The lateral soil pressure is an important input parameter for choosing the type and performing the design of a retaining wall. The value of lateral soil pressure always used Rankine's & Coulomb's theoretical solution. And the influences of lateral soil pressure are retaining wall, the property of back filled soil, the interface between retaining wall and back filled soil, the slop angle of back filled slop, extra dynamic or static loading, and groundwater table…etc. But the theoretical solution only considered about simple and perfect condition, not involved these complex situations. This paper is using the FLAC. It can consider the deformation behavior of back filled soil and the interaction analysis of retaining wall and back filled soil in complex situations accurately. First, this paper considers that when back filled angleαis equal to 0°. During simulating the active and passive states of lateral soil pressure and critical slip, consider two kinds of back filled soils in three displacement modes of the retaining wall. The three displacement modes of the retaining wall are:1) rotation about base (RB mode):linearly increasing, constant. 2) translation (T mode):constant. 3) rotation about top (RT mode):linearly decreasing, constant. Considered the lateral soil pressure and break slip when back filled angleαis not equal to 0°,αis equal to 5°, 10°, 15° using FLAC. Considered the critical break slip when back filled angleαis not equal to 0°.And compared with Fang and Ishibashi's experiment solution in simulating the active states. The conclusion shows that using FLAC the lateral soil pressure in RB mode is much closer to the Rankine's & Coulomb's theoretical solution, the next is T mode, and much difference is the RT mode. The break slip is straight in RB mode, and spiral line in RT mode. The total pressure center is much closer to the Rankine's theoretical solution in the RB and T mode, and much difference in the RT mode. Compared with Fang and Ishibashi's experiment solution when it is closer to the critical condition, they are closer.

參考文獻


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