热-湿-应力耦合作用下框架锚杆支撑的边坡冻融特性分析

为探究季冻区框锚支护边坡的冻融规律，根据传热传质理论，给出了土体在冻融过程中温度场、水分场和应力场的数学模型方程，使用有限差分法对温度场和水分场进行分析，在每个时间步长内使用有限单元法对应力场进行分析。同时，针对土体与结构的协同作用，提出了零宽度四节点单元作为二者的联结单元，来体现二者的联结关系。基于MATLAB软件平台编制了计算程序，并结合室外试验验证了程序的可靠性。结果表明：边坡顶部受温度影响较大，地表温度在冻结和融化时对土体最大影响深度分别是2.0m和1.5m；冻结时的剪应力大约是融化时的2.5倍，在坡面上分布较均匀，边坡处于稳定状态；融化时的剪应力在坡脚处出现应力集中，在融化区和未融化区交界面发生剪应力突变，边坡处于不稳定状态；3种工况下冻结时锚杆轴力最大，大约是初始工况的2.4~2.5倍，融化时锚杆留有残余轴力，大约是初始工况的1.1~1.3倍，表明冻融过程中的冻胀变形对锚杆内力影响较大，一旦超过其抗拉极限，就会发生锚杆被拔出的现象致使防护失效，边坡失稳。因此由冻结引起的变形会对锚杆内力产生不可忽略的影响，此类边坡工程中需要加以重视。

Study on freeze-thaw characteristics of slopes supported by frame anchors under the action of hydrothermal coupling

In order to explore the law of freezing and thawing of frame-anchor-supported slopes in seasonal freezing areas, according to the theory of heat and mass transfer, the mathematical model equations of the temperature field, moisture field and stress field of the soil in the freezing and thawing process are given, and the finite difference method is used. Analyze the temperature field and the moisture field, and use the finite element method to analyze the stress field in each time step.At the same time, in view of the synergy between soil and structure, a zero-width four-node element is proposed as the connection unit of the two to reflect the connection between the two. The calculation program is compiled based on the MATLAB software platform, and the reliability of the program is verified by the outdoor experiment. The results show that the top of the slope is greatly affected by the temperature, and the maximum impact depth of the surface temperature on the soil during freezing and melting is 2.0m and 1.5m respectively; the shear stress during freezing is about 2.5 times that of melting, on the slope surface The distribution is relatively uniform, and the slope is in a stable state; the shear stress during melting appears stress concentration at the toe of the slope, and the shear stress mutation occurs at the interface of the melting zone and the unmelting zone, and the slope is in an unstable state;The axial force of the anchor rod is the largest when freezing under the three working conditions, which is about 2.4~2.5 times that of the initial working condition. The residual stress of the anchor rod remains when it is thawed, which is about 1.1~1.3 times of the initial working condition. Frost heave deformation has a great influence on the internal force of the anchor rod. Once its tensile limit is exceeded, the anchor rod will be pulled out, resulting in failure of protection and instability of the slope. Therefore, the influence of frost heave deformation on the internal force of the anchor rod cannot be ignored, and attention should be paid to slope engineering in areas with similar soil climate.