循环冻融石炭系板岩横观各向多源损伤演化机制及抑制

Nolinear damage of rockmass caused by cyclic freezing and thawing is triggered as a geotechnical engineering problem can not be avoided in Xige second railway. After a serious freezings and thawings in every year, tunnel surrounding rock Carboniferous slate has been caused much failure，which damage mechanism and control measure needed to be essentially investigated. The objective of this project is thus to conduct both fundamental and application-oriented research such that freezing transversely isotropic deformation of Carboniferous slate can be disclosed,deformation and failure of the freeze-thaw damage mechanism can be explored, the control measures can be formed.A serious of tests will made,i.e. on the base of the mineral composition analysis and microstructure tests, and Carboniferous slate samples under freezing conditions of Brazil split, no response of mechanical unconfined compression and MTS three axis test, to explore the short-term freeze-thaw,seasonal freeze-thaw and frost heave of the year environment transversely isotropic deformation mechanism will made later. The principle of damage mechanics, the equivalent constitutive and elastic-plastic theory combined with internal will be formed,includes the establishment of deflection and the volume response of two inner time, which can reflect the Carboniferous slate elastic-plastic effect and the temperature field and stress field coupling transversely isotropic mechanical model, calculation methods the development of rock mechanics. After freeze thawing slate deformation mechanism of Carboniferous environment being deeply probed, the mechanism of damage under loading will be revealed, the control principle of the deformation and failure of the freeze-thaw damage will be explored , and the control measures will be proposed . This project will disclose damage mechanism of Carboniferous slate,form the freeze-thaw suppression technique of deformation and provide direct technical support for the construction of rock engineering in cold area.

循环冻融引发岩体非线性损伤是西格二线不可回避的岩土工程问题,特别是隧道中的石炭系板岩地段,每年经历冻融交替达数十次,损伤破坏特别严重,其冻融致损机制和抑制亟待研究。项目以揭示石炭系板岩冻融损伤演化机理和构建抑制措施为目标,开展横观各向同性多源损伤演化和抑制的理论和应用研究。基于石炭系板岩的矿物成份分析和微观结构测试,从石炭系板岩在冻融条件下的巴西劈裂、无侧限压缩及MTS三轴试验的力学响应入手,探索短期冻融、季节性冻融及常年冻胀环境下横观各向同性的变形机制;结合内时损伤力学、等效本构和弹塑性理论,构建包含偏斜和体积响应两个内时时间,且能反映弹塑性效应及温度场和力场耦合横观各向同性力学模型；深入探究冻融环境下石炭系板岩的变形机制，揭示其内时损伤机理，探索控制冻融损伤变形和抑制原理。本研究将揭示石炭系板岩变形及损伤的冻融特征,构建石炭系板岩冻融损伤理论和抑制技术,为寒区岩石工程建设提供技术支持。

循环冻融引发的温度场和力场耦合是高寒区不可回避的岩土工程问题。本课题结合青藏铁路西格二线新关角隧道工程实例，针对冻融横观各向同性岩体强度及破坏准则、冻融横观各向同性岩体中寒区圆形隧道冻胀力、考虑横观各向同性岩体冻融效应的运营隧道稳定性、横观各向同性岩体隧道冻融损伤抑制理论及方法等问题展开深入研究。结果表明：1）随着冻融循环次数增加，岩体单轴、三轴压缩强度均显著降低。当层理倾角0°26.6°时，岩体沿与轴线呈一定角度方向发生剪切破坏；当26.6°83.0°时，岩体沿层理面发生剪切破坏；当83.0°90°时，岩体沿垂直方向发生劈裂破坏。2）随着冻融循环次数增加，岩体拉伸强度显著降低。随着层理倾角增大，岩体拉伸强度将逐渐增大，破坏面倾角呈现先增后减的变化趋势。3）受冻融循环影响，围岩竖向、水平位移及初期支护受力均呈现出显著增长趋势。4）基于多层圆筒壁稳态热传导方程和斯蒂芬近似解析公式，采用等效厚度换算法确定新关角隧道隔热保温层采用夹层铺设时，所需厚度为 3.22 cm；采用表面铺设时，所需厚度为3.01 cm。在此基础上，结合隧道纵向温度分布规律，确定新关角隧道隔热保温层采用夹层铺设时，所需长度为1607.2 m；采用表面铺设时，所需长度为2102.7 m。