基于应变软化模型的岩石应变局部化数值分析

发布时间：2018-03-25 10:40

本文选题：应变局部化　切入点：侧向变形　出处：《中国矿业大学》2015年硕士论文

【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。
[Abstract]:In this paper, by means of laboratory uniaxial compression test and resistance strain monitoring, lateral deformation is taken as the main observed value to explore the relationship between the start-up of rock strain localization phenomenon and the characteristics of rock deformation and failure, and the numerical simulation method is used. Based on the constitutive relation of strain softening, considering the change of strength parameters, confining pressure and initial defect factors of rock after peak, combined with the characteristics of rock failure and the shape of shear zone, this paper explores the strain localization phenomenon in the process of full stress and strain of rock. The results are as follows: (1) the ratio of stress 蟽 B to peak stress 蟽 d at the start of strain localization in this paper is 0.422 / 0.44 0. 58, respectively. The rock strain localization starts at the middle and late stage of the stable growth stage of rock crack. At the stage of accelerated crack propagation, it is obvious. The three rock failure patterns obtained by uniaxial compression test correspond to the specific strain localization process. 2) different variation models of shear strength parameters after peak have obvious influence on the stress-strain relationship of rock samples. However, considering different variation models of shear strength parameters after peak, the lateral strain of rock samples at different locations is obviously different, and the final deformation of rock samples is different. The phenomenon of strain localization is also different. When the shear zone is "X-type" and near vertical shear zone, the strain localization phenomenon is not obvious compared with the concentrated local area of shear zone. Whether the strain localization is significant or not is closely related to the shear zone shape. 3) the strain localization is different from that of the shear zone. When the lithology condition is the same, the strain localization of rock sample is obvious under the middle and low confining pressure. With the increase of confining pressure, the difference of lateral strain in different position of rock sample decreases gradually, the strain localization phenomenon is not obvious gradually, the deformation of rock sample gradually tends to the total synergistic deformation of each part. 4) when there are initial defects in rock sample, the deformation of rock sample, The shear bands obtained from the five defect locations are divided into monocline shear plane and V-shaped wedge shear zone. The shear bands are all developed in the defect position. When the slope and length of the rock sample shear zone are the largest, The peak strength is the largest, while the residual strength is the smallest, and the strain is concentrated near the shear band. The strain localization phenomenon is obvious. 5) using FLAC3D software, the Mohr-Coulomb model and the strain softening model considering the post-peak strength attenuation are respectively used as the constitutive model to carry out the numerical simulation and analysis. The strain softening model shows a more obvious deformation phenomenon after the peak value. The range of the relief zone is larger, the pressure of the supporting pressure area is reduced, and the range of the shear stress concentration zone of the overburden rock is larger, which makes the damage range of the excavation become larger. It can be seen that the numerical analysis is dangerous to engineering by neglecting the strength attenuation of rock after peak, that is, strain softening.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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