冻融和循环载荷作用下对饱和砂岩损伤机理的研究

Research on Damage Mechanism of Saturated Sandstone Subjected to Freeze-Thaw and Cyclic Loading

为研究寒冷地区饱和砂岩的冻融损伤机理,采用DMA450伺服压机,在静载100N、动载80N、波动频率5~200Hz、温度-40~40℃的条件下,进行了饱和砂岩在不同频率正弦波单轴载荷作用下杨氏模量随温度变化的实验研究,获得滞（粘）弹性的弛豫衰减,以及有衰减引起的砂岩样品微结构变化情况。结果表明：饱和砂岩的杨氏模量和弹性波速度随温度升高而降低,随频率提高而增大;-40~20℃温度范围是冻融损伤最严重的区域。同时,在三种低频条件下（1.6Hz、2.8Hz和5.0Hz）用共振法在0℃获得相变衰减峰,反映了饱和砂岩的冻胀融缩效应,其产生的应力导致了饱和砂岩的损伤。从机理来看,前者是微观缺陷的演变,长期积累会导致破坏;后者是一种物理风化作用造成的宏观损伤。本文结果可为研究寒冷地区饱和岩石冻融损伤的机理及规律提供一定的参考。

In order to research into the freeze-thaw damage mechanism of saturated sandstone in cold regions,experimental study of its Young’s modulus variation with temperature under the condition of uniaxial loading of sine wave at different frequencies was carried out by using DMA450 servo press,and static loading 100 N,dynamic loading 80 N,wave frequency 5 ~ 200 Hz,temperature-40 ~ 40℃.The microstructure change of sandstone samples due to lag（sticky） elastic relaxation attenuation was understood.Results show that both Young’s modulus and elastic wave velocity decrease with temperature increase,but increase with frequency increase;temperature range from-40℃ to 20℃ is the most serious range of freeze-thaw damage.At the same time,the phase-change attenuation peak at 0℃ was obtained under condition of three low frequency（1.6Hz,2.8Hz,5.0Hz）,respectively,based on resonance method,which causes the frost heaving and thaw contraction of saturated sandstone and produces stress resulting in saturated sandstone damage.From the mechanism point of view,the former is the evolution of micro defects,long-term accumulation will lead to failure;the latter is the macroscopic damage caused by a physical weathering.Above results may provide a reference for investigation on damage mechanism and regular pattern of saturated rock in cold regions due to freeze-thaw action.