微觀參數對礫石層強度影響探討

Abstract

本研究旨在探討卵礫石層在不同微觀特性參數下的剪切力學行為，並使用Particle Flow Code（PFC）軟體進行現地直接剪力試驗的數值模擬。卵礫石層因其獨特的非均勻性和異向性，對土木工程設計和基礎建設是一大難題。研究以台灣桃園更新世礫石地層為例，參考現地直剪試驗數據，建立數值模型，並採用部分因子實驗設計法來探討微觀參數對礫石層的土壤強度參數的影響。 在模擬過程中，根據輸入的微觀特性參數，記錄了4種不同正向應力狀態下模型的剪應變及剪應力。再根據莫爾-庫倫破壞包絡線(Mohr-Coulomb failure envelope)計算試體的強度參數凝聚力(c)和內摩擦角(ϕ)。微觀破壞的數值模擬結果顯示，凝聚力的範圍在在0.25 MPa至11.76 MPa，平均值為2.47MPa，內摩擦角範圍在1.84°至31.83°，平均值為13.63°。 此外，通過ANOVA分析，確定了對強度參數影響顯著的微觀參數。研究結果顯示，鍵結勁度比(k ̅_n⁄k ̅_s )對凝聚力影響顯著，而鍵結楊氏模數(E ̅_c)、鍵結勁度比(k ̅_n⁄k ̅_s ))、團塊替換比例(Gratio)和團塊旋轉角度(α)對內摩擦角影響顯著。這些發現有助於更好地理解卵礫石層的力學行為，並為工程設計提供參考依據。 最後，本研究通過數值模擬和現地試驗數據的對比，驗證了PFC軟體在模擬現地直接剪力試驗中的有效性，並提出了針對卵礫石層強度參數的工程設計建議，以期提高工程設計的準確性和穩定性。

This study aims to investigate the shear mechanical behavior of gravel layers under different microscopic parameters using the Particle Flow Code (PFC) software for in situ direct shear test simulation. Due to their unique heterogeneity and anisotropy, gravel layers pose significant challenges for civil engineering design and construction. Using the Pleistocene gravel strata of Taoyuan, Taiwan as a case study, this research establishes a numerical model based on field direct shear test data and employs a fractional factorial experimental design to explore the effects of microscopic parameters on the soil strength parameters of gravel layers. During the simulation process, we recorded the model's shear strain and shear stress under four different normal stress states based on the input microscopic parameters. Using the Mohr-Coulomb failure envelope, the strength parameters cohesion (c) and internal friction angle (ϕ) were calculated. The numerical simulation results of microscale damage show that the cohesion ranges from 0.25 MPa to 11.76 MPa, with an average of 2.47 MPa, while the internal friction angle ranges from 1.84° to 31.83°, with an average of 13.63°. Additionally, ANOVA analysis identified significant microscopic parameters affecting the strength parameters. The results indicate that the bond stiffness ratio (k ̅_n⁄k ̅_s ) significantly affects cohesion, while the bond Young's modulus (E ̅_c), bond stiffness ratio (k ̅_n⁄k ̅_s ), clump replacement ratio (Gratio), and clump rotation angle (α) significantly affect the internal friction angle. These findings help better understand the mechanical behavior of gravel layers and provide reference for engineering design. Finally, this study validates the effectiveness of the PFC software in simulating in situ direct shear tests through numerical simulations and field test data comparison. It offers engineering design recommendations for the strength parameters of gravel layers, aiming to improve the accuracy and stability of engineering designs.