本研究主要係利用微音器及加速度計量得之波傳訊號，對砂土層 中因振動或變位所產生之音波與振波之傳播特性，進行探討與測試。 本研究利用改良式直接剪力試驗儀，以西螺砂作為試驗土樣，在 直剪盒上裝入微音器及加速度計，以應力控制方式施加剪力，進行一 系列的定荷重剪力試驗。本研究探討位移與剪應力、音波及振波之相 關性等，藉以瞭解砂土受剪力時音波及振波訊號發生特性。結果顯示 當剪應力到達試體破壞前剪應力的40%~50%會產生較大的音壓。之 後隨著剪動位移，產生較小的音波及振波。砂土相對密度越高在相同 正向應力下產生的音波及振波越大。在相同的條件下，剪應力增量越 大，產生的音波及振波越大。另外，本研究進行了淺層土層中音波及 振波現地量測試驗。音源的產生是引爆一個埋設深度為80 m 重達七 百五十公斤的乳膠炸藥，至於量測方式係將微音器及加速度計埋置於 距音源水平距離20 m 處，埋置深度為30 cm。結果顯示此次試驗中 之音波係伴隨振波同時出現。說明當土層發生變位或錯動時，只要振 動的量夠大，音波便能藉由振波向外傳遞至較遠處。 This research used wave signals measured from microphones and accelerometers to investigate transmission properties of sound waves and vibration waves generated by shock vibration or shear displacement in sand layer. This research carried out a series of constant loading shear tests by means of a modified direct shear apparatus. Set a microphone and a accelerometer in the direct shear box to measure sound pressure accelerate. Siluo sand was used in the tests and the shear stress was applied with air cylinder. The signals of vibration and sound wave were measured from the direct shear tests. The results showed that when the shear stress has reached 40%~50% of soil strength, the higher sound pressure would appear. Then of values of vibration and sound would become smaller with the increase of shear displacement. For the sand with higher relative density, the vibration and sound wave would be getting higher with the same normal stress. Under the same condition, higher shear stress increment will cause higher vibration and sound wave. In addition, field test was performed in this research. The sound and vibration waves were caused by the explosion of dynamite of 750 kg which was imbedded at depth of 80 m. The microphone and the accelerometer were set apart from the sound source of 20 m, and these sensors were imbedded at depth of 30 cm. From the results of the experiment, the sound and vibration waves were appeared at the same time. If the generated energy of slide or movement of sand is large enough, the sound waves may transmit away with the vibration waves to a farther distance simultaneously.
