饱和岩石滞弹性弛豫机理的实验研究

Experimental Research on Anelastic Mechanism of Saturated Rocks

通过Metravib热机械分析仪,用正弦波加载方式,模拟地震波的传播。实验时固定静载为100N,正弦波动载荷恒为60N,将总载荷控制在屈服点以下。在温度为-50℃~90℃,升温速率保持在1℃/分,频率为5Hz^400Hz的条件下,对饱和泵油彭山砂岩和遂宁砂岩样品进行单轴循环加载实验,获得饱和泵油彭山砂岩和遂宁砂岩的衰减、虚模量、实模量、波速与温度和频率以及动载荷的关系。以此研究了饱和多孔岩石的衰减和虚模量、杨氏模量和弹性波波速随温度和频率的动态响应。取得了随频率增高,饱和多孔岩石的衰减峰和虚模量峰的峰位向高温方向移动的热激活弛豫机制。杨氏模量和弹性波波速随温度升高而下降,随频率增高而增大,具有频散效应;杨氏模量和弹性波波速随动载荷振幅的增大而降低。这些结果与低频共振的驻波实验取得了同样的热激活弛豫规律,说明热激活弛豫规律具有一定的普适性。

Sine wave loading experiments were performed to simulate seismic wave by using Metravib Dynamic Mechanical Analyzer. Fixed 100N static load and 60N sine wave dynamic load were applied. The total loading force was controlled under the yield stress. Temperature was controlled between --50℃ and 90℃; heating speed was maintained onto 1℃ per minute, and the frequency was controlled between 5Hz- 400Hz. Pump-oil saturated Pengshan sandstones and Suining sandstones were tested under uniaxial cyclic loading. The variations of attenuation, imaginary modulus, real modulus and velocity with temperature and frequency were obtained. The attenuation peak and the imaginarY modulus peak shift to higher temperatures when the frequency increases due to the thermal relaxation phenomena. Both Young~ s modulus and wave velocity decrease with the temperature increase but increase with frequency increase and with obvious frequency dispersion. Young＇s modulus and wave velocity decrease when the dynamic load increases. Experimental results are similar to that from low-frequency resonance standing wave experiments, which indicates that thermal relaxation regularities generally exist in saturated porous rocks.