英文篇名
The Application of Two-Dimensional Plane Strain Analysis for Deep Excavation - Using PLAXIS Program
作者
徐明志、黃心泉、張登貴、詹絢存、俞清瀚
關鍵字
深開挖、二維平面應變分析、土壤硬化模式、三向度效應
摘要
過去國內深開挖工程大多採用摩爾-庫侖土壤模式(Mohr-Coulomb Model, MC模式)進行總應力分析(φ = 0 ),具有參數選用簡便且求解快速之優點;然而土壤硬化模式(hardening soil model, HS模式)可模擬土壤之非線性行為,同時考量土壤剪切硬化(shear hardening)及壓縮硬化(compression hardening),具雙降伏面,且解壓/再壓與主加壓(primary loading)階段具有不同土壤勁度,並隨土體應力狀態改變,應更適合模擬深開挖問題。因此,本文藉由國內廣泛使用之PLAXIS程式架構,首先介紹排水、不排水配合有效應力與總應力之分析觀念;並於回顧MC模式之特性後,簡要介紹HS模式及討論其分析參數之重點。此外,台灣地區深開挖工程中常使用地中壁及扶壁作為減少擋土連續壁側向變形及周圍土體變位之措施,故本文同時整理二維平面應變分析方法,近似模擬前述措施之三向度行為,以供工程界參考。
英文摘要
Due to its advantages for operation, the MC model with the total stress concept is widely used for numerical analysis of deep excavations in Taiwan. However, the hardening soil model (HS model) is able to simulate the non-linear stress-strain relationships of soils, as well as the shear and cap yield surface (isotropic hardening) and stress-dependent soil stiffness at various conditions. It thus should be more reliable for deep excavation situations. Therefore, the drained and undrained analyses with both total and effective stress concept are evaluated by employing the PLAXIS program. Then characteristics of the MC model are reviewed and a brief introduction of the HS model and the proper parameters are presented. In addition, buttress and cross walls are commonly employed in deep excavation to reduce the lateral displacement of diaphragm walls and adjacent ground settlement. Accordingly, for reference we present the actual behaviors of 3D effects resulting from these measures, which were approximately simulated with the plane-strain methods.