硬脆性流纹岩变形分析的综合刚度法

COMPREHENSIVE STIFFNESS TECHNIQUE USED IN DEFORMATION ANALYSIS OF HARD AND BRITTLE RHYOLITE WITH FISSURES

天然岩石在压缩荷载作用下内部裂隙的闭合、张开、扩展过程直接影响岩石的力学性能。在经典移动点回归法的基础上,引入泊松比进行修正提出了一种6阶段变形划分方法——综合刚度法。不同加载路径下流纹岩的单轴压缩试验结果分析表明:(1)采用综合刚度法可以准确获得硬脆性岩石试样接触应变ε_0、裂隙闭合应变ε_c、弹性应变ε_e、裂隙稳定扩展应变ε_i、裂隙不稳定扩展应变ε_d和峰后应变值ε_f;(2)单轴压缩下流纹岩试样裂隙闭合应变达到峰前总应变的44.2%,峰前裂隙扩展应变和峰后应变均较小,脆性特征明显;(3)单轴压缩弹性阶段加卸载试验表明,采用综合刚度法能更准确剔除试样接触应变,获得裂隙闭合应变。综合刚度法更加适用于硬脆性岩石的变形分析,可以准确剔除试样接触应变并获得更准确的各阶段应变,特别是裂隙闭合应变,可以作为评价岩石内裂隙密度的定量参数。

The closure, opening and propagation of internal fissures of natural rock under compressive load can affect the mechanical properties of rock directly. Based on the classical moving point regression technique, Poisson＇s ratio is introduced to propose the six stage division method which is called comprehensive stiffness technique（ CST）. The results of uniaxial compression test under different loading paths show the following. （ 1 ） Contact strain ε 0, closure strain of cracks εc, elastic strain ε e, stable crack propagation , unstable crack propagation εd and post-peak strain εi of hard and brittle rock can be achieved by the CST. （2） Under uniaxial compression test, the closure strain of cracks at 44. 2% of pre-peak strain is larger than the elastic strain of rhyolite. The pre-peak crack propagation strain and post-peak strain are all small. Actually the rhyolite is significantly brittle. （ 3 ） Loading and unloading test in elastic stage shows that the contact strain can be removed by comprehensive stiffness technique and the closure strain of cracks. The comprehensive stiffness technique is more suitable to the deformation analysis of hard and brittle rock, since it can remove the contact strain and achieve more accurate strain of different stages, especially the closure strain of cracks. These strains can be the quantitative parameters of the evaluation of crack density in rock.