Mechanical Analysis of Leaned-Back Retaining Wall with High Fill

台灣山區道路，因受地形及上邊坡岩壁之影響，須於下邊坡擋土牆背填土開挖寬度受限情況下施工，且大都採用倚臂式擋土牆，但倚背式擋土牆相關之分析、研究並不多見。故本論文針對倚臂式擋土牆在不同高度及背填土開挖寬度受限情況下進行相關力學行為之研究，期能提供相關工程單位參考使用。 本研究以倚背式擋土牆為範例，利用工程計算方法與 PLAXIS 電腦程式進行穩定性分析並探討相關力學行為，由研究結果得知：（1）倚背式擋土牆與一般擋土牆受地震作用下，抗傾倒與抗滑安全係數均有相同減少趨勢；（2）倚背式擋土牆受地震時牆底土壓力最大值較常時低，應是牆身幾何重心在後，而發生地震時作用力往前傾，因此減少牆踵承載力；（3）就整體變形而言，背填土頂部加載荷重之情況下，不論牆高或牆背開挖寬度，在牆背回填土接近頂部有較大位移，且底版牆踵附近土 壤垂直應力有最大值；（4）倚背式擋土牆回填土較高者，背填土頂部加載荷重之情況下，牆身上部有往外移情形，而下半段牆身則有往內移，基礎底版變形隨著幾何形狀發展。Due to the constraint of topography and upslope rock cliff in the mountainous road of Taiwan, the retaining wall is required to build up in the limited excavation of back soil and leaned-back retaining walls are usually adopted. However, the analysis and research about this type of retaining wall are scarce. This thesis will study the relevant mechanical behavior of leaned-back retaining walls with different height and limited width of excavation in order to provide the reference and application for related engineering institutes. This study aims at the example of leaned-back retaining walls to perform the stability analysis and relevant mechanical behavior through the engineering computation and Plaxis computer program. From the analyzed results, it indicates that (1).The resistant safety factors of leaned-back retaining walls in sliding and overturning are decreased as the commonly used retaining walls subjected to earthquake action. (2).The maximum soil pressure at the bottom of slab for leaned-back retaining walls is decreased during earthquake. This is due to the acting force moving forward while the gravity of wall is backward inclined. In this way, the soil pressure in the heel of slab will be reduced. (3).The settlements of back soil near the top of leaned-back retaining walls are all greater when subjected to the surcharge load for different height and limited excavation of back soil. The maximum soil pressure is found near the heel of slab. (4).The displacement at the top of higher leaned-back retaining walls moves in the outer direction, while moving inwards at the bottom, and the slab deforms along its geometric shape.致謝………………………………………………………………………I 中文摘要………………………………………………………………II 英文摘要………………………………………………………………III 目次……………………………………………………………………IV 表目錄…………………………………………………………………VII 圖目錄…………………………………………………………………VIII 1.1前言 .......................................................................................... 1 1.2研究動機 ................................................................................... 1 1.3研究方法 ................................................................................... 2 1.4研究內容 ................................................................................... 3 2.1土壤之極限平衡狀態理論 ....................................................... 4 2.2土壓力理論 ............................................................................... 4 2.2.1靜止土壓力 ........................................................................... 4 2.2.2 Rankine 土壓力理論 ............................................................. 5 2.2.3 Coulomb 土壓力理論 ........................................................... 7 2.2.4 Mononobe-Okabe 動態土壓力.............................................. 8 2.2.5莫耳-庫倫破壞準則（Mohr-Coulomb failure criteria）...... 11 2.3擋土牆牆體穩定性 ................................................................. 12 2.4土壤彈塑性模式 ..................................................................... 15 第３章 分析方法 .................................................................................... 23 3.1分析方法 ................................................................................. 23 3.2PLAXIS 2D 數值分析程式 ........................................................ 23 3.2.1Input (輸入) 單元 ................................................................ 24 3.2.2Calculation (計算) 單元....................................................... 25 3.2.3Output (輸出) 單元 ............................................................. 25 3.2.4莫爾庫倫（Mohr-Coulomb）模式 ...................................... 26 3.2.5莫爾庫倫模式之基本參數 .................................................. 27 第４章 研究範例之工程設計分析......................................................... 29 4.1研究範例 ................................................................................. 29 4.2設計參數 ................................................................................. 32 4.3擋土牆重心及重量分析 ......................................................... 33 4.4土壓力分析 ............................................................................. 34 4.5擋土牆穩定檢核 ..................................................................... 46 4.6不同牆高研究案例常時與地震分析結果比較 ...................... 54 第５章 研究範例之 PLAXIS 2D 程式數值分析 ..................................... 56 5.1研究範例 ................................................................................. 56 5.2研究範例分析結果與討論 ..................................................... 58 5.2.1研究範例一 ......................................................................... 58 5.2.2研究範例二 ......................................................................... 65 第６章 結論與建議 ................................................................................ 69 6.1結論 ........................................................................................ 69 6.2建議 ........................................................................................ 70 參考文獻 ................................................................................................. 7