成都地区砂卵石围岩宏细观力学特性研究及应用
发布时间：2019-02-28 15:09
【摘要】：随着大量城市隧道的开发利用使得穿越砂卵石地层而造成的安全问题日益引起了人们的注意。砂卵石土是由不同粒径的卵石和砂土构成的松散颗粒堆积体,其颗粒排列复杂且具有明显的离散特征。本文采用颗粒筛分试验、室内大型三轴试验和PFC三轴数值模拟试验相结合的手段,深入研究砂卵石土的力学特征及工程特性,定量地分析了主要细观参数对砂卵石土特性的影响规律,并获得砂卵石土的宏细观力学参数,为研究隧道砂卵石围岩稳定性分析奠定了基础。主要得到了以下成果:(1)对不同含水率、密度和粗粒含量的砂卵石土进行了不排水不固结大型三轴试验研究,分析不同物理状态下的应力-应变关系曲线变化规律和抗剪强度的规律;(2)基于颗粒流点接触连接本构模型(未考虑颗粒破碎),通过PFC内嵌fish语言程序,得到PFC3D数值模拟平台并完成数值模拟三轴试验;数值模拟三轴试验和室内大型三轴试验得到的应力—应变曲线总体上比较吻合,抗剪强度参数与室内试验得到的强度参数相对误差很小,此次数值模拟具有较高的吻合度;(3)从细观角度研究影响砂卵石土变形特性和抗剪强度的相关因素,对颗粒接触模量、摩擦系数和刚度比这三个主要细观参数对砂卵石土宏观力学性质的影响做了详细的分析。分析结果表明:随着颗粒接触模量的增加,砂卵石土的初始变形模量也有增大的趋势,峰值强度也有所越高,破坏时的轴向应变则减小,剪缩变形越来越小,数值模型由剪缩转向剪胀时相应的轴向应变也越小;随着颗粒摩擦系数的增大,砂卵石土的峰值强度也随着增大,峰值强度与摩擦系数大致呈正比例关系,砂卵石土的初始变形模量也随摩擦系数增大有稍微增大的趋势,但颗粒的摩擦系数只对变形的影响不大;颗粒刚度比值越大峰值应力越小,初始模量越小,体积应变减小到最小时应变越小,但是刚度比对砂卵石土的特性影响不明显。这些结论一定程度上定量的揭示了影响砂卵石土工程特性的细观因素。为研究砂卵石土特性提供了一定的参考。(4)砂卵石地层隧道开挖后,掌子面正前方土体最先发生破坏,且距离掌子面越近隧道拱顶的土体变形越大,从而引起地表沉降;应力松弛区域由掌子面正前方逐渐向右上方扩散,最终导致开挖面失稳。
[Abstract]:With the development and utilization of a large number of urban tunnels, people pay more and more attention to the safety problems caused by traversing sand and pebbles. Sand-pebble soil is a loose particle accumulation composed of pebbles and sandy soil with different particle sizes, and its particle arrangement is complex and has obvious discrete characteristics. In this paper, the mechanical and engineering characteristics of sandy pebble soil are studied by means of particle sieving test, large-scale triaxial test in laboratory and PFC triaxial numerical simulation test. The effects of main micro-parameters on the characteristics of sand-pebble soil are quantitatively analyzed, and the macro-and micro-mechanical parameters of sand-gravel soil are obtained, which lays a foundation for studying the stability of surrounding rock of sand-pebble in tunnel. The main results are as follows: (1) the large-scale triaxial test of undrained and unconsolidated sandy pebble soil with different moisture content, density and coarse grain content was carried out. The variation law of stress-strain relation curve and the law of shear strength under different physical conditions are analyzed. (2) based on the constitutive model of particle flow point contact connection (without considering particle breaking), the PFC3D numerical simulation platform is obtained by PFC embedded in fish program, and the numerical simulation triaxial test is completed. The stress-strain curves obtained by numerical simulation triaxial test and indoor large-scale triaxial test are generally in good agreement, and the relative error between shear strength parameters and the strength parameters obtained from indoor tests is very small, so the numerical simulation has a high degree of coincidence. (3) the relative factors affecting the deformation characteristics and shear strength of sand-pebble soil are studied from the view of meso-view, and the contact modulus of particles is also studied. The effects of friction coefficient and stiffness ratio on the macro-mechanical properties of sand-pebble soil are analyzed in detail. The results show that with the increase of particle contact modulus, the initial deformation modulus of sand-pebble soil also increases, the peak strength is also higher, the axial strain decreases and the shear deformation becomes smaller and smaller. The corresponding axial strain is smaller when the numerical model changes from shear to dilatancy. With the increase of particle friction coefficient, the peak strength of sand-pebble soil increases, and the peak strength and friction coefficient show a positive proportional relationship. The initial deformation modulus of sand-gravel soil also increases slightly with the increase of friction coefficient, and the initial deformation modulus of sand-pebble soil increases slightly with the increase of friction coefficient. However, the friction coefficient of the particles has little effect on the deformation. The larger the particle stiffness ratio, the smaller the peak stress, the smaller the initial modulus and the smaller the volume strain is, but the stiffness ratio has no obvious effect on the characteristics of sandy pebble soil. To some extent, these conclusions reveal the micro-factors that affect the engineering characteristics of sand-pebble soil. It provides some reference for studying the characteristics of sand-pebble soil. (4) after the excavation of the sand-gravel stratum tunnel, the soil in front of the palm surface is destroyed first, and the deformation of the soil body closer to the palm surface is greater, which leads to the settlement of the earth surface. The stress relaxation region gradually diffuses from the front of the palm to the upper right, and finally leads to the instability of the excavation surface.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U451.2
[Abstract]:With the development and utilization of a large number of urban tunnels, people pay more and more attention to the safety problems caused by traversing sand and pebbles. Sand-pebble soil is a loose particle accumulation composed of pebbles and sandy soil with different particle sizes, and its particle arrangement is complex and has obvious discrete characteristics. In this paper, the mechanical and engineering characteristics of sandy pebble soil are studied by means of particle sieving test, large-scale triaxial test in laboratory and PFC triaxial numerical simulation test. The effects of main micro-parameters on the characteristics of sand-pebble soil are quantitatively analyzed, and the macro-and micro-mechanical parameters of sand-gravel soil are obtained, which lays a foundation for studying the stability of surrounding rock of sand-pebble in tunnel. The main results are as follows: (1) the large-scale triaxial test of undrained and unconsolidated sandy pebble soil with different moisture content, density and coarse grain content was carried out. The variation law of stress-strain relation curve and the law of shear strength under different physical conditions are analyzed. (2) based on the constitutive model of particle flow point contact connection (without considering particle breaking), the PFC3D numerical simulation platform is obtained by PFC embedded in fish program, and the numerical simulation triaxial test is completed. The stress-strain curves obtained by numerical simulation triaxial test and indoor large-scale triaxial test are generally in good agreement, and the relative error between shear strength parameters and the strength parameters obtained from indoor tests is very small, so the numerical simulation has a high degree of coincidence. (3) the relative factors affecting the deformation characteristics and shear strength of sand-pebble soil are studied from the view of meso-view, and the contact modulus of particles is also studied. The effects of friction coefficient and stiffness ratio on the macro-mechanical properties of sand-pebble soil are analyzed in detail. The results show that with the increase of particle contact modulus, the initial deformation modulus of sand-pebble soil also increases, the peak strength is also higher, the axial strain decreases and the shear deformation becomes smaller and smaller. The corresponding axial strain is smaller when the numerical model changes from shear to dilatancy. With the increase of particle friction coefficient, the peak strength of sand-pebble soil increases, and the peak strength and friction coefficient show a positive proportional relationship. The initial deformation modulus of sand-gravel soil also increases slightly with the increase of friction coefficient, and the initial deformation modulus of sand-pebble soil increases slightly with the increase of friction coefficient. However, the friction coefficient of the particles has little effect on the deformation. The larger the particle stiffness ratio, the smaller the peak stress, the smaller the initial modulus and the smaller the volume strain is, but the stiffness ratio has no obvious effect on the characteristics of sandy pebble soil. To some extent, these conclusions reveal the micro-factors that affect the engineering characteristics of sand-pebble soil. It provides some reference for studying the characteristics of sand-pebble soil. (4) after the excavation of the sand-gravel stratum tunnel, the soil in front of the palm surface is destroyed first, and the deformation of the soil body closer to the palm surface is greater, which leads to the settlement of the earth surface. The stress relaxation region gradually diffuses from the front of the palm to the upper right, and finally leads to the instability of the excavation surface.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U451.2
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