高温下石灰岩膨胀特性和力学特性的试验研究

利用自行研制的岩石高温装置和RMT-150C岩石力学试验机,对石灰岩试件在200~700°C高温双向约束条件下的膨胀特性和力学特性进行了试验研究。结果表明:升温过程中,随着温度的升高,石灰岩试件两个约束方向的膨胀应力在600°C前逐渐增加,600°C或650°C以后出现减小现象;石灰岩垂直层理方向的热膨胀应力大于平行层理方向的热膨胀应力。恒温过程中,600°C以前的试件两方向膨胀应力曲线都随时间延长呈平稳上升,但曲线斜率远远小于升温过程;恒温一定时间后,膨胀应力趋于该温度的一个稳定值。700°C恒温结束后,石灰岩两方向的膨胀应力小于恒温前的值,说明到一定温度后石灰岩已膨胀到极限。在试验温度范围内,石灰岩峰值应力随温度升高而降低,700°C时,峰值强度值比常温下降低了58.92%,说明高温对岩石的强度会产生明显的弱化作用。石灰岩峰值应变随温度升高先增加后减少,500°C前峰值应变增加,之后逐渐减小。由于受约束条件限制,在过高温度后,石灰岩内部裂隙部分闭合,空隙数量减少,致使一定温度后其热膨胀应力和峰值应变可能减小,但具体原因有待进一步研究。

Experimental Research on Swelling Properties of Limestone and Sandstone under High Temperature

The swelling properties and mechanical properties of limestone was investigated under high tamperature from 200℃ to 700℃ and bidirectional restraint with the device used to heating rock designed by ourseIves and servo-control testing machine RMT-150C.The experimental results show that the two directions'swelling stress of limestone increased with temperature rising before 600℃,and decreased after 600℃ or 650℃.The swelling stress perpendicular to bedding plane was bigger than that parallel to bedding plane.The curves of swelling stress and temperature ascended smoothly with time under constant temperature before 600℃,but the slopes were much less than those during temperature rising.The swelling stress tended to be a steady value at last under constant temperature.When constant temperature ended,the swelling stress was smaller than those before constant temperature at 700℃.It showed that the limestone had swelled to the limit value after a certain temperature.The peak-stress of liraestone decreased gradually with temperature increasing and the peak-stress at 700℃ decreased 58.92%comparing to room temperature.It showed high temperature can weaken the strength of limestone evidently.The peak-strain increased before 500℃ firstly,and then reduced after 500℃.The swelling stress and peakstrain may reduce after a certain temperature because the rock sample was restricted and some fissures closed and the number of cracks reduced under over-high temperature,but the detailed reason needs more researches to testify.