Particle flow analysis of fracture characteristics of marble with a single hole
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摘要: 基于室內單軸壓縮試驗結果，利用顆粒流程序PFC2D，模擬含預制孔洞大理巖在單軸和雙軸壓縮條件下的破壞過程，分析預制孔洞形狀、圍壓大小以及巖石非均質性對大理巖力學特性和裂紋擴展的影響.數值結果表明：與完整大理巖試樣相比，含孔洞試樣的峰值強度顯著降低，降低程度與孔洞形狀有關；圍壓對含孔洞大理巖試樣的力學特性和裂紋擴展有顯著影響，含孔洞試樣的峰值強度隨圍壓的增加而增加，但偏應力峰值隨圍壓的增加呈先增大后減小的變化趨勢；試樣的破壞模式與孔洞形狀相關，含圓形孔洞試樣為類X型剪切破壞，含矩形孔洞或馬蹄形孔洞試樣為對角剪切破壞；巖石內部的礦物結核影響了裂紋的擴展路徑，從而改變試樣的宏觀破壞模式.微觀機理分析表明：孔洞周邊裂紋的萌生與擴展過程伴隨著應力集中區的釋放與轉移；含孔洞試樣的宏觀裂紋有3種模式：孔壁剝落、拉伸裂紋和壓剪裂紋.Abstract: Based on uniaxial compression laboratory results, the failure process of marble with a single hole was simulated using the particle flow code PFC2D under uniaxial and biaxial compressions. The influence of the pre-existing hole shape, confining pressure and the rock heterogeneity on the mechanical properties of marble and the coalescence of cracks was analyzed. Numerical results show that compared to an intact marble specimen, the peak strength of a specimen containing a single hole reduces significantly, and the extent of reduction is related to the hole shape. The confining pressure has a significant effect on the mechanical properties of marble and the coalescence of cracks. The peak strength increases with the increase of confining pressure, while the peak deviator stress increases first and then decreases with the confining pressure increasing. Specimens containing circular holes exhibit X-type shear failure, while specimens containing rectangular or U-shaped holes exhibit diagonal shear failure. The mineral nodules in the rock specimen significantly affect the propagation of cracks leading to a change in the failure mode of marble specimen. Analysis results of the microscopic mechanisms show that the initiation and propagation of cracks around the hole is always accompanied by the release and transfer of stress from a concentrated zone. Three types of macroscopic cracks can be classified in specimen containing a single hole as hole surface spalling, tensile crack, and compressive shear crack.
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參考文獻
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