单向冻结条件下模拟螺旋桩的冻拔响应（英文）

发布时间：2018-06-15 19:11

  本文选题：道路工程 + 路基　； 参考：《长安大学学报(自然科学版)》2017年04期

【摘要】：季节性冻土区活动层土体在寒季的冻结会引起与冻胀相关的工程病害,如埋设在冻土中的地基会随冻胀的发展发生冻拔等。针对该问题,寒区工程一般选用螺旋桩来减轻影响。采用COMSOL Multiphysics软件建立有限元模型,模拟单向冻结条件下螺旋桩-地基土系统的响应。考虑水分、温度、应力3种物理场的顺序耦合,即自定义水分-温度耦合计算模块,在理查德方程中考虑冰水相变、冰对水分迁移的阻抗作用等,得到某时刻的全局体积含冰量分布,根据半经验模型建立冻胀量与体积含冰量、温度之间的关系,用以计算应力场中冻胀、冻拔变形,得到应力与位移分布,最终实现水分、温度、应力3个物理场的顺序耦合。根据几何对称性,建立二维轴对称计算模型。比选了3类螺旋桩(多叶片螺旋桩、宽叶片双螺旋桩、窄叶片双螺旋桩),并设置1组直线形桩作对照。计算结果表明:边界温度设为-15℃,经过7d冻结,土体冻深超过了桩的埋设深度,3种螺旋桩的冻拔位移小于直线形桩,证明了其减轻冻拔的作用;此时,螺旋桩底层叶片将承担最多的应力,桩身可以传递更多的冷量到下部土层,促使桩周土体冻结;通过对比不同桩形,总结出叶片布设的主要几何参数,即螺距、叶片宽度与数量及顶层叶片位置等对螺旋桩-地基土系统的冻拔响应会产生较大影响,并初步探索了寒区工程中一种基础的抗冻拔措施。
[Abstract]:The freezing of active layer soil in seasonal frozen soil region will cause engineering diseases related to frost heaving, such as the foundation buried in frozen soil will be frozen and pulled out with the development of frost heave. In view of this problem, spiral pile is generally used to alleviate the influence in cold area engineering. A finite element model was established by using COMSOL Multiphysics software to simulate the response of spiral pile-soil system under unidirectional freezing. Considering the sequential coupling of moisture, temperature and stress, namely the self-defined water-temperature coupling calculation module, the ice water phase transition and the impedance of ice to water migration are considered in Richard's equation. The distribution of global volume ice content at a certain time is obtained. The relationship between frost heaving quantity and volume ice content and temperature is established according to the semi-empirical model, which can be used to calculate frost heaving and freezing drawing deformation in stress field, obtain stress and displacement distribution, and finally realize moisture content. The sequential coupling of three physical fields, temperature and stress. According to geometric symmetry, a two-dimensional axisymmetric model is established. Three kinds of spiral piles (multi-blade spiral pile, wide-blade double-helical pile, narrow blade double-helical pile) were compared and a group of linear piles were set as control. The calculation results show that the boundary temperature is -15 鈩，

本文编号：2023229