考虑冻胀效应的寒区隧道围岩变形演化机理研究

Frost injury is an important factor leading to the disaster in cold-regional tunnels. Exploring deformation evolution law of surrounding rocks considering the frost heave effect is one of the priorities to prevent accidents. First of all, the relationship between frost heaven strain and temperature and the viscoelastoplastic constitutive relation of frozen surrounding rocks are obtained by the test study on the characteristics of frost heave and creep. The constitutive model considering the two processes of frost heave and creep is finally modified and the yield criterion which can accurately reflect nonlinear characteristics of creep strength of frozen surrounding rocks is also established. Secondly, according to the deformation characteristics of frost heave, the interaction model of surrounding rocks in cold-region tunnels, unfrozen (unmelted) surrounding rocks-frozen surrounding rocks-lining, is built. The radius in which the frost deformation is zero can be solved using iterative method. Based on the solution for the model, the space-time evolution laws of stress and deformation of surrounding rocks are studied preliminary. Thirdly, according to the newly built constitutive model and the yield criterion, the ADINA software is developed secondly. The program is verified by the test data. The results of the example obtained by the program can verify the laws of stress and deformation obtained by the analytical solution. Based on the systematic analysis of results, the principle of deformation failure is revealed further and the evaluation criterion for the stability of surrounding rocks in cold region tunnels is established. At last, the factor influencing the stability is analyzed and the key factor is found and optimized. The reasonable support measures are put forward to ensure the stability of cold-region tunnels.

冻害是导致寒区隧道灾变发生的重要因素，而探明考虑冻胀效应时围岩的变形演化规律是预防灾变发生首要解决的问题之一。首先，通过室内试验研究围岩的冻胀特性和蠕变特性，获得冻胀量与温度的关系以及冻结围岩的黏弹塑性变形关系，在此基础上修正围岩的本构方程使其能同时考虑冻胀和蠕变过程，并建立描述冻结围岩蠕变强度非线性特征的屈服准则；其次，根据冻胀变形特征建立寒区隧道未冻（融）围岩-冻结围岩-衬砌相互作用力学模型，采用迭代法确定冻胀零位移的位置并求解模型，初步探讨围岩应力与变形的时空演化规律；再次，结合新建本构模型和屈服准则，采用ADINA软件进行二次开发，通过蠕变试验数据验证完善计算程序，利用算例的数值结果验证理论模型获得的应力与变形规律，系统分析计算结果，深入揭示寒区隧道围岩变形破坏的机理，建立稳定性评价准则；最后，分析围岩稳定因素，明确并优化关键因素，提出合理的支护措施来保证寒区隧道工程的稳定。

随着一带一路战略推进以及近年来振兴东北老工业基地和西部大开发战略政策的实施，一些国家级大型基建项目将迎来建设的高峰，而这些地区都属于高纬度或高海拔地区，修建的隧道将面临着冻害的威胁。针对该问题分析寒区隧道温度场和围岩应力与变形规律，可为寒区隧道的安全建设和稳定运营提供了一定的指导。.开展不等压条件下寒区隧道围岩应力与变形研究，采用已建立的冻胀本构模型，并将计算模型分解为开挖模型和冻胀模型，开挖模型采用复变函数法进行求解；通过拟合数值模拟计算结果建立补充方程，在此基础上通过迭代计算方法求解冻胀模型；叠加开挖模型和冻胀模型即可获得总应力和变形。.为了准确预测冻胀对隧道安全的影响，建立考虑非均匀冻胀计算模型。根据支护强度和支护时机的不同，将计算模型细分为三种情况：(1)rp<rL ; (2) rL<rp<rf; (3) rp>rf；根据冻胀线应变的不同取值（0和0.0055），对比应力分布情况和塑性半径的大小显示：冻胀不促进塑性区的发展但是增加衬砌中的应力差，这是导致寒区隧道稳定的一个主要因素。.根据寒区隧道的变形特征，考虑寒区隧道围岩冻胀变形的各向异性，修正冻结围岩的本构方程，结合D-P强度准则建立围岩应力分析模型并获得了围岩应力与变形的弹塑性解。计算结果显示考虑非均匀冻胀下的塑性半径和冻胀力比均匀冻胀结果偏大。.采用自动温度监测仪对该隧道进行现场观测，得到隧道不同径向深度处的温度变化规律；分析现场采用5cm保温层防护时的可靠性，结果表明在衬砌壁后仍存在0.4m的冻结范围；同时分析了冻结锋面的扩展规律，得出拱肩和底板是冻结锋面扩展速度最快、距离最远的部位，视为整个断面的危险位置。.采用Laplace积分变换和有限傅里叶正弦变换的方法求解三维轴对称温度场模型，获得了隧道的温度分布规律；开展冻土不均匀冻胀特性试验，研究不均匀冻胀系数随受力状态的变化规律；进行冻土的力学特性试验，研究强度参数随温度的变化规律。