高水压对红砂岩动态强度和变形特性影响的试验研究

Experimental investigation of the influence of high water pressure on dynamic strength and deformation characteristics of red sandstone

深部岩体工程处于高水压和高地应力地质环境中,其动态力学特性深受赋存环境的影响。为研究高水压和高地应力对岩石(体)动态力学特性的影响,基于自主研发的高水压高地应力岩石动力学试验装置,对红砂岩进行不同水压力和轴向静应力的冲击试验,分析岩石动态峰值应力、极限应变、平均应变率及动态变形模量随水压力的变化规律,探索动态峰值应力、极限应变与平均应变率的关系,构建峰值应力、极限应变、平均应变率与水压力及极限应变与平均应变率的关系经验模型。基于滑移断裂模型,分析水压力作用下岩石微观结构的强度与变形特性,探索水压力对岩石动态力学特性的影响机制。研究结果表明,相同轴向静应力作用下,红砂岩的动态峰值应力随水压力的增大逐渐增大,峰值应力与水压力呈良好的对数函数分布;红砂岩的平均应变率和极限应变随水压力的增加而减小,二者都与水压力呈指数函数关系。外界水压力及红砂岩裂隙面中水的Meniscus效应、Stefan效应及牛顿内摩擦效应抑制裂隙的萌生扩展,进而提高红砂岩的抗压强度及抵抗变形能力。研究结果有助于完善深部岩石动力学理论,对具有深部高水压环境下岩体工程爆破开挖安全高效设计和施工提供理论基础。

The deep rock mass is in a high water pressure and high geo-stress occurrence environment,the dynamic mechanical properties of rocks are deeply affected by the occurrence environment.In order to investigate the effects of the high water pressure and the high geo-stress on the dynamic mechanical properties of rock mass,based on a self-developed high water pressures and high geo-stress rock dynamic test device,impact tests are carried out on red sandstone samples under different water pressures and axial static stresss.The variation rules of the dynamic peak stress,the ultimate strain,the average strain rate and the dynamic deformation modulus of red sandstones under different water pressures are analyzed respectively.The relationship among the average strain rate,the dynamic peak stress and the ultimate strain are explored.Empirical models for the relationship between the water pressure and the peak stress,the ultimate strain,the average strain rate,and for the relationship between the ultimate strain and the average strain rate are constructed.The strength and deformation characteristics of the microstructure of rocks under the water pressure are analyzed based on sliding crack model and the influence mechanisms of the water pressure on the dynamic mechanical properties of rocks are explored.The results show that,under the same axial static stress,the peak stress of rock samples increases gradually with the increase of the water pressure,and the peak stress shows a good logarithmic function distribution with the water pressure.Besides,the average strain rate and the ultimate strain of rock samples both decrease exponentially with the increase in the water pressure.The Meniscus effect,the Stefan effect and the Newtonian internal friction effect of the water in the fractured surface of red sandstone and the external water pressure inhibit the initiation and expansion of the fissures,and thus improve the compressive strength and deformation resistance of red sandstone at dynamic loading level.The research results are beneficial to the perfection of deep rock dynamic theory and provide a theoretical basis for the safe and efficient design and construction of blasting excavation in rock mass engineering with deep high water pressure environment.