高温作用后灰岩物理力学性质变化试验研究

Experimental study on change of physical and mechanicalproperties of limestone after high temperature

对于易受高温(如火灾)影响的地下岩体工程,其受过高温以后物理力学性质参数的变化是研究的关键问题。利用微机控制电液伺服岩石三轴试验机(TAW-2000)对不同高温作用后的灰岩试样进行单轴压缩试验,分析了温度对灰岩应力应变曲线、峰值应力、峰值应变、动静弹性模量以及泊松比等物理力学性质的影响。结果表明:500℃是烧失率随温度变化的转折点;高温后灰岩纵波波速随着温度的升高而逐渐降低,350℃~500℃时波速下降速度最快;不同高温作用后所测得的应力应变曲线形状基本一致,呈现出4个不同的变形阶段,符合岩石变形破坏的基本规律;随着加热温度的升高,灰岩的峰值应力逐渐降低,在200℃~500℃之间快速下降;350℃是灰岩峰值应变增长速度发生变化的一个突变点,350℃后灰岩的塑性变形显著加强,开始呈现出一定的蠕变特性;高温后灰岩动弹性模量在一开始就随温度快速下降,其静弹性模量在200℃以后才开始快速下降,两者都在试样加热到500℃后下降速率开始变缓;350℃是灰岩泊松比发生突变的转折点。

For underground rock mass engineering that is susceptible to high temperature(such as fire),the change of physical and mechanical properties after high temperature is a key that we need to study.The uniaxial compression test of different post-high temperature limestone samples was carried out by computer controlled electro-hydraulic servo rock triaxial test machine(TAW-2000).The effects of temperature on the physical and mechanical properties such as stress-strain curve,peak stress,peak strain,dynamic and static elastic modulus and poisson’s ratio of limestone were analyzed.The results show that 500℃is a turning point for relation of loss rate and temperature.After high temperature,the longitudinal wave velocity of limestone gradually decreases with the increase of temperature,and the wave velocity decreases rapidly from 350℃to 500℃.The shapes of the stress-strain curves measured after different high-temperature effects are basically the same,and four different deformation stages are presented,which is consistent with the basic law of rock deformation and failure.With the increase of heating temperature,the peak stress of the limestone gradually decreases,and it rapidly decreases between 200℃and 500℃.350℃is a turning point of the peak strain growth rate of limestone,and the plastic deformation of limestone is significantly strengthened and begins to present creep characteristics above 350℃.After high temperature,the dynamic modulus of limestone rapidly decreases with temperature at the beginning,and its static elastic modulus begins to decrease rapidly above 200℃,which both of them decrease slowly after the sample is heated to 500℃.350℃is a turning point of the change of limestone Poisson’s ratio.