軟弱岩石之漸進屈伏模式及其應用

Abstract

極軟弱岩石可算是一種邊際性大地材料，其力學行為深受應力路徑與應力歷史影響，在承受相當荷載之後常會呈現明顯的非線性變形性與殘餘應變。本研究首先整理交通大學近年於軟岩中完成大量的各類試驗工作成果，建立了一套實用的使用者介面與資料庫系統，以期便於透過此資料庫來查詢及瞭解實驗相關位置、地質狀況、物性、與力學性質。地質材料之力學行為極為複雜，往往並非簡單的力學模式所能輕易模擬。本模式運用複屈伏面觀念，提出一套三面模式，可以合理考慮軟岩之真實力學行為，如：非線性、受應力歷史影響、異向性等。對於材料參數之標定，本文採最佳化方法，將標定材料參數視為一個逆問題，引用基因演算來處理求解。本文所提出之三面模式若配合離散力學分析方法（如有限元素法），即可以模擬分析一般之地工邊界值問題。本文中將三面模式分別融入非線性與彈塑性有限元素分析方法，用以模擬現地傍壓儀以及實驗室三軸實驗，由數值模擬結果與試驗結果之比較驗證此模式之合理性與正確性。若將此一非線性或彈塑性有限元素分析方法用於實際大地工程問題中，可進一步分析在軟岩中的邊坡穩定、淺基礎、深基礎等大地工程問題。

The mechanical behavior of soft rock, a typical marginal geomaterial, is highly dependent on its stress-path and stress-history. Nonlinear stress-strain relation and permanent deformation are notable features of the mechanical behavior of soft rock. This study began with the establishment of a data base of the results of all soft-rock experiments carried out by the geotechnical group of National Chiao-Tung University; the data base contains information including location, geology profile, and experimental results (physical properties and mechanical properties). Various multi-surface models have demonstrated their effectiveness and capability in modeling the inelastic behavior of a geomaterial. A 3-surface model, a special version of the generalized transitional yielding approach, is adopted for modeling the mechanical behavior of soft rock in the presented work. The proposed model is capable of modeling major features of mechanical behavior of soft rock. Optimized calibration by a genetic algorithm is proposed for determining model parameters. Numerical simulation incorporating the presented model was carried out to simulate in-situ pressuremeter and laboratory triaxial tests in soft sandstone. The numerical simulation successfully captures the trend of experimental results. The presented approach has a good potential in analyzing relevant geotechnical problems in soft rock.