【作者】 刘飞；

【导师】 董青红；

【作者基本信息】 中国矿业大学 ， 地质工程， 2015， 硕士

【摘要】 本文通过室内单轴压缩试验和电阻应变监测的方法,以侧向变形作为主要的观测值,探究岩石应变局部化现象的启动、特征与岩石变形破坏特征的关系;运用数值模拟方法,基于应变软化本构关系,考虑岩石峰后强度参数变化、围压和初始缺陷因素,结合岩石破坏特征和剪切带形态,探究岩石全应力应变过程中应变局部化现象,得到如下结论:1)本文试验所得应变局部化启动时的应力σB与峰值应力σd的比值σB/σd分别为0.42、0.44、0.58,试验得出的岩石应变局部化启动大致在岩石裂纹稳定扩展阶段的中后期即开始发生,在裂纹加速扩展阶段已经表现的比较明显;单轴压缩试验得到的三种岩石破坏形态对应特定的应变局部化过程。2)峰后抗剪强度参数的不同变化模式对岩样的应力应变关系有较明显影响,对平均侧向应变特征影响较小。而考虑峰后抗剪强度参数的不同变化模式时,得出的岩样不同位置的侧向应变有明显的差异,岩样最终变形形态各异,应变局部化现象也有不同的表现。当岩样内为“X型”的剪切带和近垂直剪切带时,应变局部化现象相比剪切带集中局部区域表现的不明显,应变局部化现象表现的显著与否和剪切带形态密切相关。3)围压不同时,应变局部化现象差异较大。岩性条件一致时,中低围压下,岩样应变局部化现象比较明显,随着围压的增大,岩样不同位置侧向应变的差异逐渐减小,应变局部化现象逐渐表现的不显著,岩样的变形逐渐趋于各部分整体协同变形。4)岩样存在初始缺陷时,对变形、强度和剪切带形态有比较大的影响。试验的5个缺陷位置得到的剪切带分为单斜剪切面和“V型”楔体剪切带,剪切带均发育于缺陷位置。岩样剪切带倾角和长度最大时,其峰值强度最大,而残余强度则最小,应变会集中于剪切带附近,应变局部化现象比较明显。5)运用FLAC3D软件分别以Mohr-Coulomb模型和考虑峰后强度衰减的应变软化模型为本构模型进行数值模拟分析,使用应变软化模型岩体在峰值后表现出更加明显的变形现象,卸压区范围更大,支承压力区压力减小,覆岩剪应力集中区范围更大,从而使得开挖造成的破坏范围变大,可见忽略岩石峰后强度衰减即应变软化现象而进行的数值分析对工程来说是偏于危险的。更多还原

【Abstract】 In this paper, regarding the lateral deformation as the main observations and using uniaxial compression test and resistance strain monitoring to explore the relationship between starts and features of rock strain localization phenomena and characteristics of rock deformation and failure; Using numerical simulation method,based on strain softening constitutive, considering the changes of the strength parameters of rock after peak value, confining pressure and initial defect factors,combining rock failure characteristics and shear bands form, exploring rock the whole process of stress-strain strain localization, get the following conclusions:1) Experimentally derived the ratio of strain localization startup stress σB and peak stress σd were 0.42,0.44,0.58, test results of strain localization of rock start that began roughly in the middle and late stages of rock stable crack growth, startup of rock strain localization began roughly in the middle and late stages of rock stable crack growth, relatively obvious in stages of crack accelerated expansion; Three rock damage morphology from uniaxial compression test corresponding to specific strain localization process.2) Decay modes of shear strength parameters after the peak have a significant impact on the stress-strain relationship of rock samples and affect the average lateral strain characteristics relatively small. While considering the lateral strain of rock samples in different locations, the results from decay modes of shear strength parameters after the peak is significantly different, the final form of the rock sample is not the same and strain localization phenomena also have different performance.When the "X" type of shear zones and near-vertical shear zone, compared with shear zone concentrated in the local area, strain localization performance is not obvious,Strain localization performance is clearly and closely related to shear zones form.3) Strain localization phenomenon is fairly different when confining pressure is different. When lithologic conditions are consistent, under low and middle confining pressure, the rock sample strain localization phenomenon is quite obvious, with the increase of confining pressure, differences of rock samples lateral strain in different position decreases, strain localization phenomenon is gradually unconspicuous,deformation of various parts of the rock samples tended to the overall cooperative deformation.4) While rock samples exist initial defect, it has a relatively large impact ondeformation, strength and shear zone form. Shear zone form can be divided into single oblique shear plane and "V-type" wedge shear zone, shear zone were developed in the defect location. When the inclination and length of shear zone is maximal, it has the biggest peak strength and smallest residual strength, strain can concentrate near the shear zone, strain localization phenomenon is relatively evident.5) Using FLAC3 D software respectively base on Mohr-Coulomb model and strain softening model that considering strength degradation to analyse, when using the strain-softening model, rock exhibit more pronounced deformation phenomena after the peak, relief area has a wider range, pressure of bearing pressure zone is reduced, shear stress concentration area of overburden rock has a wider range, so that the scope of the destruction of overlying strata produce larger. Thus, it is dangerous for engineering when ignores rock strength decreases after peak to carry on numerical analysis.更多还原