卵礫石層潛盾切刃磨損影響因素數值模擬

Numerical Simulation Study on Factors Influencing Cutting Tools Wear in Gravelly Soils for Shield Tunnel

陳羿帆(Yi-Fan Chen)

指導教授 ： 鄭富書 ； 王泰典

國立臺灣大學/工學院/土木工程學系/碩士(2023年)

https://doi.org/10.6342/NTU202303104

摘要

過去幾十年來，隨著都市化的發展對基礎設施需求提升，往往應用潛盾工法進行地下空間開發，以土壓平衡式潛盾機應用最為廣泛。潛盾面盤由推進旋轉的方式與地層岩土材料接觸，複雜的開挖過程經常使潛盾機前端切刃面盤產生嚴重磨損，尤其在卵礫石層更是嚴重。將大幅地增加施工成本與工期，由此可知切刃磨損議題之重要性。然而近年來有諸多預測切刃磨損的模型，這些預測模型多半用於特定條件或經驗公式，並且也鮮少投入刀具與卵礫石切削關係的研究，評估礫石層潛盾隧道磨損率的方法還有待發展。
本研究旨在建立一套方法以探討影響卵礫石層切刃磨損的因素，並評估隧道開挖切刃磨損率。以離散元素法進行數值分析為基礎，利用PFC3D建構卵礫石地層潛盾開挖刀刃磨損數值模型，力求更符合實際考量礫石不規則形狀與粒徑分布，抑低可能造成結果不確定的因素。並採前人實驗結果作為數值模擬中微觀參數的驗證對象，過程中進行複迴歸分析與變異數分析，釐清礫石微觀組構對磨損率的影響。最終，探配置不同開口率、切刃型式與切刃高度的面盤對隧道開挖的影響，以及切刃破碎礫石土壤的機制。
研究結果顯示，砂礫石微觀參數中，顆粒摩擦係數、鍵結抗拉強度、鍵結楊氏模數與礫石含量四項因子與磨損指標具高度相關，交互項則以摩擦係數與鍵結拉力強度項對磨損最具影響力。峰前刀具磨損主因和顆粒鍵結有關，峰後則與摩擦係數有關。最後，基於切刃齒配置的分析結果，齒式切刃採剝落切削的方式破壞，輪式切刃則採切割破碎的方式，而同時配置兩種切刃於切刃面盤上能更有效的進行隧道開挖。故本文發展的卵礫石對切刃齒磨損模擬方法，可以提供礫石層潛盾刀盤分析設計的參考。

關鍵字

潛盾工法 ； 切刃磨損 ； 卵礫石層 ； 離散元素法 ； 隧道開挖

並列摘要

In recent decades, the development of urbanization has led to a rapid demand for infrastructure. The shield tunneling method has been widely used to underground space development, with the earth pressure balance shield machine being the most commonly used approach. The tunnel boring machine (TBM) cuts through the geological strata via rotational and advancing motion during excavation. The complex excavation process often leads to severe wear of the TBM’s cutting tools, especially in gravelly soils. It always end up with a significant increase in construction cost and construction period, thus highlighting the importance of cutting tools wear issues. In recent years some studies have been developed to predict wear prediction model for disc cutters, mostly based on specific conditions or empirical formulas. However, there is limited research regarding the relationship between the tools and soils. The methods on assessing the wear of TBM in gravelly soils are still under development.

This study aims to establish a methodology to investigate the factors affecting cutter wear in sandy cobble strata and evaluate the wear rate during tunnel excavation. A numerical analysis approach based on discrete element method, PFC3D is conducted to construct a wear model for gravelly soils. It can better capture the irregular shape and particle size distribution of gravel, reducing potential uncertainties. Previous experimental results are used to validate the microscopic parameters in the numerical simulations. Multiple regression analysis and analysis of variance are performed to clarify the influence of gravel microstructure on the wear rate. Finally, the impact of cutters allocation with different opening ratios, cutter types, and cutter heights on tunnel excavation is investigated, along with the mechanism of cutter-induced gravelly soils fragmentation.
The preliminary results from this research indicated that main factors for cutter are friction coefficient, bonding tensile strength and bond Young's modulus between particles plus gravel content are highly correlated with the wear index. The interaction term between the friction coefficient and bond tensile strength have the most significant influence on wear. The primary cause of wear before the peak is related to particles bonding, while after the peak, it is associated with the friction coefficient. Based on the analysis of cutters allocation, cutter bits exhibit peeling cutting, while disc cutters adopt cutting and fragmentation. Simultaneously employing both types of cutting tools on the cutterhead can enhance tunnel excavation efficiency. The developed simulation method for cutter wear on gravels in this study can provide a reference for the analysis and design of shield cutterheads in gravel layers.

並列關鍵字

Shield tunneling method ； Tool wear ； Gravelly soils ； Discrete element method ； Tunnel excavation

參考文獻

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