分離元素法於岩石貫切破壞試驗之模擬分析

Distinct Element Approach on Rock Indentation test

林郁修(Yu-Hsiao Lin)

指導教授 ： 陳立憲

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2007年)

https://doi.org/10.6841/NTUT.2007.00318

摘要

晚近台灣多遭遇於岩覆較深、長大之隧道工程，故多採用全斷面機械式鑽掘工法，是故對於隧道施工鑽掘之安全性與效率備受重視。本研究以分離元素法（Distinct Element Method）之三維數值軟體PFC3D進行模擬單一楔形刃口正向貫入岩材，並比對貫切破壞之理論模式與試驗結果進行相關研析。
經校驗微觀輸入參數與尺度敏感分析，本研究採用花崗岩及大理岩等中至高強度岩類進行數值模擬貫切破壞之行為特徵，藉由改變：（1）楔形刃口角度模擬隧道鑽掘機具刀角幾何因素；（2）水平側向圍壓以模擬側向大地應力之影響；及（3）楔形刃口貫切位置模擬接近岩材開口弱面而進行系列分析。由傳統巨觀性實驗結果得知，當楔形刃口角度漸增與水平側向圍壓越大時，受測岩材產生延性或脆性破壞所需之貫切力亦隨之增大；而臨界貫入深度分別因此遞增與遞減。與實驗比較本數值模擬結果顯示可得之定性趨勢。另再分析粒間微裂位置對應於貫切加載歷程之關係，發現隨楔形刃口角度之漸增（即由尖變鈍），其無因次化之塑性區半徑則明顯減小。於初裂後，塑性區外之粒間張力微裂累積，則隨巨觀張力裂縫長度之增長而成線性增加。再者由粒間微裂空間分佈之演化表可知，隨側向圍壓之增加，塑性區尺寸亦因此增加。此外，因楔形刀角接近開口弱面距離之減少，其最大貫切力與臨界貫入深度皆隨之降低之趨勢；亦經模擬得到頗為相符之成果。
最後將數值所求得之無因次化臨界塑性區半徑，與理論解進行比對，本研究之數值結果得到良好之對應，可驗證模擬方法之適確性。

關鍵字

貫切破壞 ； 分離元素法 ； 楔形刃口角度 ； 側向圍壓 ； 粒間微裂

並列摘要

Recently, for a tunnel can be safe and efficiency, fully cross-area and mechanical boring method for deeper and longer tunnel, such as Tunnel Boring Method(TBM), should be important in Taiwan. This study presents a numerical simulation of the normal wedge indentation of rock by using Particle Flow Code in three dimensions(PFC3D)which bases on the principle of the distinct element method(DEM) and compares numerical results with indentation test theory model and laboratory test results.
In this investigation, according to analysis of sensitivity parametric, by changing : (1) the wedge angle for modeling the cutting tools geometry, (2)the lateral confinement and (3) indentation positions by using granite and marble. In the view point of the macro-scope, the results show that the maximum indentation force increases with the increase in wedge angle and lateral confinement; and the indentation depth respectively increase and decrease. Moreover, in accordance with the micro-fracture compare with the indentation loading curve, dimensionless critical radius decrease in evidence with the wedge angle increase. After initial crack, the normal cracks accumulate numbers outside the plastic zone and the tensile cracks become the linear relation. In other hand, by the evolution of the micro-crack, when the lateral confinement increase, raise the shape of plastic zone. Furthermore, with the indentation position approach the free boundary, the indentation force and the indentation depth decrease.
At last, the numerical dimensionless critical radius is estimated and compares with the experimental results as well as the analytical solutions. Good agreement found between the simulation and previous literature in dimensionless critical radius. Therefore, this study proves that the suitability of the numerical solutions for indentation fracture.

並列關鍵字

Indentation fracture test, Distinct element method ； Wedge angle ； Lateral confinement ； Micro-crack

參考文獻

【4】 張家詮，「分離元素法於擬脆性岩材微觀破裂機制之初探」，碩士論文，國立台北科技大學土木工程系，台北，2007。

【10】 Alehossein, H., Detournay, E. and Huang, H., “Analytical model for the indentation of rocks by blunt tools,” Rock Mechanics and Rock Engineering, vol. 33, no. 4, pp. 267-284, 2000.

【16】 Cundall P., Strack O., “A discrete numerical model for granular assemblies,” Geotechnique, vol. 29, pp. 47-65, 1979

【19】 Drescheret, A. and Kang Y., “Kinematic approach to limit load for steady penetration in rigid-plastic soils,” Geotechnique, vol. 37, no. 3, pp. 233-246, 1987.

【21】 Griffith, A. A., “The phenomena of rupture and flow in solids,” Phil. Trans. Ray. Soc. London A221, pp. 163-197, 1921.