自然冷却和遇水冷却后高温花岗岩力-声特性试验研究

Experimental Study on Mechanical and Acoustic Characteristics of High-temperature Granite after Natural Cooling and Water Cooling

以松辽盆地露天花岗岩为研究对象,对自然冷却和遇水冷却后高温花岗岩进行单轴压、拉和声波测定试验.研究不同方式冷却后花岗岩温度(100℃、200℃、300℃、400℃、500℃、600℃、700℃、800℃,以下简称100℃-800℃)与表观形态、纵、横波波速、弹性模量、泊松比、抗压强度、抗拉强度间关系,并将纵、横波波速与抗压强度、弹性模量建立联系.同时考虑遇水冷却后静置过程对花岗岩力-声性质影响.研究表明:(1)静置0 h-2 h是质量损失、纵波波速下降主要时段,静置6 h后变化率可以忽略;自由水损失量与力-声特性损失量存在一定线性关系;(2)温度升高,自然冷却后花岗岩纵、横波波速、弹性模量、抗压强度、抗拉强度呈线型下降,遇水冷却后呈凹线型下降;高于300℃,自然冷却后花岗岩力-声参数均大于遇水冷却,泊松比变化率与其相反,600℃时冷却方式不同对花岗岩纵、横波波速、弹性模量、抗压强度影响达到最大,遇水冷却比自然冷却分别低33.33%、31.88%、53.33%、31.74%,700℃-800℃时冷却方式对花岗岩力声特性影响减小;(3)温度变化,花岗岩纵、横波波速与抗压强度、弹性模量呈良好相关性.所得结论可以提高花岗岩力-声特性测量准确性,为力学特性预测提供一个可行方法,并为岩体工程安全稳定性评估提供依据.

Taking the open-pit granite mine in Songliao Basin as a study object,uniaxial compression,tensile and acoustic tests were carried out on the high-temperature granite after natural cooling and water cooling.The relationships between the heated temperature(100℃,200℃,300℃,400℃,500℃,600℃,700℃,and 800℃,hereinafter referred to as 100℃-800℃)and the superficial morphology,longitudinal and transverse wave velocities,elastic modulus,Poisson’s ratio,compressive strength and tensile strength of granite after cooling in different ways were studied.Moreover,the relationships between longitudinal and transverse wave velocities and compressive strength and elastic modulus were established.After cooled down to 20℃,the water-cooling granite samples were pulled out of water and placed in a thermotank of 20℃.The influence of thermostatic processing time on the mechanical-acoustic properties of granite was considered.It was found that the mass and longitudinal wave velocity of granite decreased mostly within the first two hours of thermostatic processing,and exhibited negligible changes after six hours of thermostatic processing.There existed a linear relationship between the free water loss and the decreases in mechanical-acoustic properties.With the increase of temperature to which the granite samples were heated,the longitudinal and transverse wave velocities,elastic modulus,compressive strength and tensile strength of granite decreased almost linearly after natural cooling,but concavely after water cooling.When the heated temperature was higher than 300℃,the mechanical-acoustic parameters of granite after natural cooling were all greater than those after water cooling,except for the Poisson’s ratio.When the heated temperature was 600℃,the influence of cooling method on the properties of granite reached the maximum:the longitudinal and transverse wave velocities,elastic modulus and compressive strength of granite after water cooling were,respectively,33.33%,31.88%,53.33%and 31.74%lower than those after natural cooling.When the heated temperature was 700℃-800℃,the influence of cooling method on the mechanical and acoustic characteristics of granite decreased.The relationships among longitudinal and transverse wave velocities,compressive strength and elastic modulus of granite demonstrated good correlations.The conclusions of this study can be used to improve the accuracy of measuring the mechanicalacoustic characteristics of granite,which provide a feasible way for predicting mechanical properties and a basis for evaluating safety and stability of geotechnical structures.