具空間變異性土體壓縮指數之均質化

Abstract

在現實生活中，土壤因環境影響使其呈現非均質的狀態，土壤性質也有著空間變異性，然而為了方便大地工程的設計及分析，工程師常將土壤視為均質。因此如何選擇具有代表性的材料性質以代表整體土壤便為本研究之課題，本研究將針對土壤之壓縮指數，提出一簡易的均質化模型，透過此模型可以有效地代表土壤受壓後之壓密行為。 本研究將透過穩態隨機場模擬具空間變異性之壓縮指數，並運用MATLAB以及有限元素軟體ABAQUS進行隨機有限元素分析，將分析後之壓密沉陷量與均質模型擬合獲得有效壓縮指數 ，同時利用空間平均模型計算此壓縮指數隨機場下之均質化壓縮指數，並比較有效壓縮指數與均質化壓縮指數之結果。在初步的結果中發現，土壤元素受到壓密行為後各處之權重皆不同，這種非均勻驅動之現象也影響空間平均模型之結果。因此本研究便找出與壓密行為有關之影響因子，提出符合壓密行為之新pseudo incremental energy (PIE) 模型，並配合權重幾何平均計算出均質化壓縮指數。 針對大地工程中常見之壓密案例，以ABAQUS進行不同關聯性長度之分析，並藉由新PIE模型進行後續分析，研究結果表明，在大多數案例中新PIE模型所獲得之均質化壓縮指數與隨機有限元素分析獲得之有效壓縮指數皆具有相當高的關聯性。

Soil is non-homogeneous due to environmental influence, and the soil properties also have spatial variability. However, in order to make geotechnical engineering design and analysis easy, engineers often regard soil as homogeneous. Therefore, how to choose representative soil properties to represent the in-situ soil is the subject of this research. This research focuses on soil compression index and proposes a homogeneous model which can represent the soil consolidation behavior. In this study, we simulate the compression index with spatial variability through the stationary random field and conduct random finite element analysis (RFEA) by ABAQUS software, then fitting the consolidation settlement to obtain the effective compression index . Meanwhile, we compute spatial averages of compression index random field to obtain homogenized compression index and compare to . In the preliminary results, we found that the soil elements are different everywhere after soil consolidation, and non-uniform mobilization of soil also affects the results of spatial average model. Therefore, we figure out the influence factors related to consolidation behavior, and propose a new pseudo incremental energy (PIE) model, and adopt weighting geometric average model to obtain the homogenized compression index. We use ABAQUS to analyze different scale of fluctuations for different cases, and use the new PIE model for subsequent analysis. The research results shows that the homogenized compression index and have a high correlation in most geotechnical cases.