人工岩體受剪變形之音波特性; The properties of sound wave during shear deformation of artificial rock

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题名:	人工岩體受剪變形之音波特性;The properties of sound wave during shear deformation of artificial rock
作者:	薛景壕;Ching-hao Hsueh
贡献者:	土木工程研究所
关键词:	人工岩體;岩石摩擦;岩石破裂;音波;加速度;sound pressure;acceleration;crack of rock;friction of rock;artificial rock
日期:	2010-07-29
上传时间:	2010-12-08 13:35:29 (UTC+8)
出版者:	國立中央大學
摘要:	本研究以氣動式直剪試驗儀進行人工岩體之摩擦試驗與剪力強度試驗，以模擬岩石層面摩擦與破裂之行為，接著利用電容式微音器及加速度計量測試驗過程中產生之波傳訊號，探討音波、振波與位移間之相互關係。試驗方法以應力控制方式分階施加水平應力，進行一系列固定正向應力之摩擦與剪力強度試驗。本研究之波傳訊號以最大音壓及最大加速度描述某時間區段內訊號強弱，由摩擦試驗結果顯示於人工岩體發生破壞前，若可測得較背景音波訊號為大之音壓，則表示層面間之應力已達到降伏摩擦應力，若摩擦應力持續增加則會發生瞬間滑動破壞，並產生大幅音壓。剪力強度試驗結果顯示於人工岩體發生破壞前，可測得裂隙產生時所發出之音壓，然於試驗中未觀察到顯著之降伏應力及音壓，當人工岩體受剪破壞時才產生巨幅音壓。岩石層面通常存在許多已開裂層面和局部開裂岩體，當局部開裂岩體受剪破裂時，可能尚不致產生大量位移；然已開裂層面受剪時所承受之剪力為層面間之摩擦阻抗，破壞時將產生瞬間之顯著滑動。因此本研究提出一岩層破壞預警模式，當測得巨幅音壓時，即表示此岩層層面之部分岩體開始因受剪而產生破裂，須將該區域視為警戒範圍，應密集觀測滑動破壞所產生之音波訊號，一旦發現音壓有小幅驟升現象發生，即代表獲知岩層或邊坡即將發生滑動破壞之訊息，此時立刻對此岩層或邊坡發出警訊，將可以降低或預防災害的產生。 This research used artificial rock specimens to perform a series of friction tests and shear tests by stress controlled direct shear apparatus, to simulate friction and crack behaviors of rocks. In the testing processes, the data of sound waves and vibration waves was measured, and the relationships among sound waves, vibration waves and shear displacement were discussed. To avoid the disturbances of vibration and noise of the shearing machine, an air cylinder was used to apply the shearing or frictional forces in several small steps until the failure of specimens occur. The signals of wave propagation in a time period were expressed as maximum sound pressure and maximum acceleration. According to the results of the friction tests, some apparent signals of sound pressure and acceleration would be measured before the frictional failure. This means that the frictional stress between these two artificial rocks has reached the yielding value. If the frictional stress increases continuously, the sliding failure may occur and cause some large sound pressure and acceleration simultaneously. On the other hand, although some apparent signals of sound pressure and acceleration can be detected from the shearing tests, but the yielding stress still can not be found and the failure occurred instantly during the shear stress reached the peak value. Therefore, in the application of early warning of rock slope, it is understood that there may exist some apparent cracks or faults in rock ground, and both of the partial cracking or sliding rock may cause some apparent signals of sound and vibration. The combination of these information obtained from this research may support an early warning system of rock slope to decrease the damage of disaster.
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