The Deformation Analysis of Soil Gabion

土石籠擋土牆之設計法，可採用重力式擋土牆之分析原則來作初步設計，除結構幾何配置須符合現地情況外，亦要滿足各項安全性檢核（如：傾倒、滑動、承載力及整體穩定）。但土石籠擋土牆為柔性結構物，會因地盤條件、土質狀況、地下水位等因素影響，造成牆體變形之情事發生；假如變形量過大，則容易造成土石籠構造物崩塌損壞。 本研究將使用PLAXIS有限元素分析程式，採用15節點三角形元素模擬土石籠回填土及現地土壤，用5節點樑元素模擬箱籠網，分析土石籠在不同配置方式及高度之變形及位移量。 使用PLAXIS有限元素分析程式進行土石籠擋土牆變形及位移量分析結果顯示：不同堆疊型式及高度配置下，對其變形量及位移量有一定影響。水平位移主要產生於牆體坡趾部及腹部，而垂直位移主要來自土石籠擋土牆本身自重壓縮影響，有效高度7.0M時，型式A總位移量為1.440㎝，型式B總位移量1.800㎝，型式C總位移量為2.110㎝，因此基於成本、變形量及總位移量考量，型式A配置方式之土石籠擋土牆為最佳選擇。使用較輕質回填材料及配合不同加勁方式，在有效高度7.0M時，其總位移量為1.250㎝，使用一般現地土壤回填料土石籠總位移量為1.440㎝。因此使用較輕質回填材料及配合不同加勁方式可降低土石籠擋土牆變形量。The preliminary design of soil gabion is often based on the principles of the gravity retaining wall, where the geometric configuration of the structure should not only conform to the soil condition on the site, but also meet the safety inspection for overturning, sliding, bearing capacity and the overall stability, etc. However, soil gabion is a flexible structure, which may be susceptible to deformation by the factors, such as foundation condition, soil types and groundwater level further leading to collapse or damage to the soil gabion structure. This study aims to determine the deformation and displacement of soil gabion under different configurations and heights by means of PLAXIS finite element analysis program, including the 15-node triangular element simulating the soil gabion backfill and the present soil, and also the 5-node beam element simulating the cage network. The results on the above deformation and displacement of soil gabion retaining wall performed by PLAXIS finite element analysis program show that different configurations involving stacking types and heights have significant influence on deformation and displacement, where the horizontal displacement is mainly located at the toe and abdomen of the wall, while the vertical displacement is mainly caused by the compression from the weight of the wall. When the effective height is 7.0 M, the overall displacement for Type A, B and C are 1.440 cm, 1.8 cm and 2.110 cm, respectively. In considering the cost, deformation and overall displacement, the soil gabion retaining wall of Type A is the best choice of all types. On the other hand, under the same height of 7M, when using lightweight backfill coupled with different strengths, the overall displacement is 1.250 cm, which is less than the one using the onsite backfill for soil gabion, 1.40 cm, indicating that the deformation of soil gabion retaining wall can be reduced by using lightweight backfill with different strengths.摘 要 i ABSTRACT ii 目 錄 iii 表目錄 v 圖目錄 vi 第一章 前言 1 1-1 研究背景 1 1-2 研究動機與目的 2 1-3 組織架構 3 第二章 文獻回顧 4 2-1 土石籠之基本原理與特性 4 2-2 箱籠材料與力學特性 5 2-2-1材料 5 2-2-2力學特性 8 2-3 土石籠工法之介紹 10 2-4 土石籠設計原則 14 2-4-1 結構體之尺寸及配置 14 2-4-2 回填施工 14 2-4-3 容許變形 14 2-4-4 排水(級配或地工織物濾層) 15 2-5 傳統力學分析方法 15 2-5-1 滑動穩定檢核（Sliding） 15 2-5-2 傾覆穩定檢核（Overturning） 16 2-5-3 基礎土壤承載力穩定檢核（Bearing Capacity） 17 2-6 數值模擬 19 第三章 程式說明 20 3-1 PLAXIS程式基本操作原則 21 3-2 網格劃分 24 3-3 輸入部分（Input） 25 3-4 計算部分（Calculation） 32 3-5 輸出部分（Output） 33 3-6 莫爾庫倫模型（Mohr-Coulomb Model） 33 3-6-1 莫爾庫倫模型參數之決定原則 34 第四章 程式分析與討論 38 4-1 分析模型建立 42 4-1-1 土層參數設定 44 4-1-2 傳統力學檢核結果 45 4-1-3 箱籠網參數設定 46 4-2 土石籠擋土牆斷面模型 46 4-3 型式A土石籠擋土牆變形量 50 4-4 型式B土石籠擋土牆變形量 58 4-5 型式C土石籠擋土牆變形量 66 4-6 不同回填替代材料與加勁方式探討 74 4-7 不同型式土石籠擋土牆變形及位移量綜合討論 96 4-8 使用輕質回填料與不同加勁方式變形及位移量綜合討論 99 第五章 結論與建議 102 5-1 結論 102 5-2 建議 103 參考文獻 10