含水率和围压对安家岭泥岩峰后力学特性影响的试验研究

Experimental Investigation on the Effects of Confining Pressure and Moisture Content on Post-Peak Mechanical Behavior of Anjialing Mudstone

为分析含水率和围压对泥岩峰后力学特性的影响,从山西安家岭矿取泥岩,制成不同含水率的5组试样,在YAW2000电液伺服试验机上开展了三轴试验,获得了不同含水率泥岩试样三轴全程应力应变曲线,使用激光共聚焦显微镜观测了泥岩增水过程中微观结构变化。利用试验结果,分析了围压和含水率对泥岩峰值强度、残余强度、弹性模量、破坏应变和脆性模量的影响规律和泥岩增水过程中微观结构的变化规律。引入脆性模量系数和强度退化指数来描述围压对泥岩峰后强度退化过程和残余强度的影响,与FLAC中的SS模型结合,建立了考虑围压影响的泥岩应变软化力学模型,模拟了围压对泥岩应变软化行为的影响。研究结果表明:(1)随着围压增加,泥岩的峰值强度、偏应力峰值、破坏应变和残余强度都增长,峰后强度降低速率趋缓,强度退化指数和脆性模量系数可以较好地描述围压对泥岩残余强度和峰后强度退化过程的影响。(2)泥岩增水过程中,岩样内微裂隙及尺寸增长,泥岩的力学性质劣化。随着含水率增加,泥岩的弹性模量、峰值强度和残余强度降低,破坏应变增长。含水率与泥岩的弹性模量、峰值强度和破坏应变之间近似服从线性关系。(3)本文基于脆性模量系数的岩石应变软化模型能较好地描述三轴压缩泥岩的全程变形行为。

In order to investigate the effects of confining pressure and moisture content on mudstone post-peak mechanical behavior,mudstone samples collected from Anjialing mine Shanxi province were divided into five groups with different moisture contents.Tri-axial compression test was conducted by using YAW2000electro-hydraulic servo testing machine,and full stress-strain curves of mudstone samples with different moisture contents were obtained.Besides,mudstone micro-structure change during the moisture content increasing process was observed by laser confocal microscope.Based on experimental results,the effects of confining pressure and moisture content on the peak strength,residual strength,elastic modulus,failure strain and brittle modulus of mudstone were analyzed;mudstone micro-structure change during moisture content increasing process was also studied.Brittle modulus coefficient and strength degradation index were introduced to describe the effects of confining pressure on the post-peak strength degradation process and residual strength.Combining with SS model in FLAC,mudstone strain softening model was established by taking into account the effects of confining pressure,to simulate the effects of confining pressure on mudstone strain softening.Results show that（1）with the increase of confining pressure,the peak strength,deviatoric stress peak value,failure strain and residual strength all increase,the post-peak strength decrease rate becomes slow.The brittle modulus coefficient and strength degradation index can better describe the effects of confining pressure on the post-peak strength degradation process and residual strength.（2）during mudstone moisture content increasing process,the microfracture and size in mudstone sample increase,its mechanical properties degrade,the elastic modulus,peak strength and residual strength decrease,and the failure strain increases.There are approximately linear relations between mudstone elastic modulus,peak strength and failure strain with the moisture content.（3）strain softening model based on brittle modulus coefficient and presented in this paper can better describe full deformation behavior of mudstone subjected to tri-axial compression.