大地材料受剪時之音波與振波特性; The properties of sound waves and vibration waves in geotechnical material during shear deformation

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题名:	大地材料受剪時之音波與振波特性;The properties of sound waves and vibration waves in geotechnical material during shear deformation
作者:	呂盈慧;Ying-hui Lu
贡献者:	土木工程研究所
关键词:	加速度;音波;摩擦試驗;剪力試驗;顯著頻率;sound wave;shear test;friction test;apparent frequency;acceleration
日期:	2011-08-08
上传时间:	2012-01-05 11:10:10 (UTC+8)
摘要:	台灣地處板塊交界處，地勢陡峭、降雨集中，以及人為過度開發山坡地，因此坡地安全監測是大地工程重要項目之一。本研究以直接剪力試驗模擬不同材料地層間之相對剪動，同時利用微音器及加速度計量測其破壞或滑動時產生之音波與振波，並藉由波傳系統的感測器具之高靈敏性，進行防災之基礎研究，以提供未來建立災害預警機制時之參考。本研究主要係利用西螺砂、七厘石與人工岩體等三種材料，進行土體之剪力強度試驗及界面摩擦試驗。結果顯示，大地材料受剪或摩擦滑動之訊號之音波顯著頻率分佈範圍具有確定性，其中砂土音波顯著頻率在30 Hz以下。七厘石為粒徑較小之礫石，其音波顯著頻率偏高，約分佈於500?840 Hz。本研究可利用上述之頻率特性，判斷原本為一複雜之音波訊號，得知其所包含的資訊。此外，振波加速度於剪應力與摩擦應力施加初期開始產生明顯訊號，當接近降伏時開始產生連續振波至破壞前開始劇增。由於振波加速度之振幅在降伏前幾乎相似，無法確定是否降伏，且容易造成誤判，但如果在邊坡持續量測到一連續生成之振波，即可列入警戒進行密集觀察。再配合音波訊號之監測，當測得之音波包含上述之頻率範圍，必須將此邊坡列入警戒區密集觀察，當測得音壓強度大於一般平均值或巨幅音壓時，則應立即發佈警報，以預防或降低災害發生。 The purpose of this study is to do a basic research of sound waves and vibration waves for warning signals of slope failure. Three kinds of material such as Silou sand, gravel and artificial rock were used to perform a series of shear tests and friction tests by using direct shear apparatus under stress control condition. In this study, to avoid the disturbances of vibration and noise during the shearing process, an air cylinder was used to apply the shearing or frictional forces in several steps until the failure of specimens occur. The sound and vibration signals were both analyzed by using the Fast Fourier Transform through the FAMOS software to represent the signals in frequency domain. The experimental data of shear and friction tests showed that the apparent frequency of sand is lower than 30 Hz and the apparent frequency of gravel is located between 500~840 Hz. According to the experimental results, the shearing information of the material could be distinguished by using the apparent frequency mentioned previously. In addition, the sound signals kept some constant and small values continuously and then some burst signals occurred at the moment of failure. However, the values of acceleration increased gradually before yielding and then some apparent signals occurred. Therefore, an early warning system of monitoring the slope failure can be established by using the combination of the information mentioned before to decrease the damage of disaster.
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