高地下水位冻土区抛物线形渠道冻胀力学分析

Mechanical analysis of parabolic-shaped canal frost heave in frozen soil regions with high goundwater level

考虑渠道断面各截面地下水位以及局部几何特性逐点不同的特殊性并结合Winkler假设,提出了高地下水位冻土区抛物线形渠道衬砌法向冻胀力与切向冻结力计算方法及截面内力计算公式.考虑曲梁曲率影响提出基于曲梁理论的截面正应力计算方法及抗裂验算公式.以河北某抛物线形渠道为例,分析衬砌截面轴力、弯矩及应力分布规律.结果表明:轴力自渠顶向渠底中部逐渐增大且均为压力;衬砌板主要在负弯矩作用下凸向内侧,仅在临近渠底时由负变正转而凸向外侧;由于存在拱效应,各截面均以压应力为主,仅渠坡中下部内侧及渠底中部附近外侧出现拉应力从而易导致开裂.分别应用直梁理论和曲梁理论计算衬砌板截面应力并进行对比分析.发现渠底中心附近曲率较大处两者相对误差可达11.78%,且直梁理论的计算结果量值偏小、安全性低,应当基于曲梁理论进行应力分析更加合理.

Considering the particularity that the groundwater level and local geometric characteristics of each section of the canal section are different point by point,combined with Winkler assumption,calculation method of normal frost heaving force and trangential freezing force of parabolic channel lining in high groundwater table and the calculation formula of internal force of section were presented.Consi-dering the influence of curvature of curved beam,the calculated method of section internal force and anti crack checking formula based on curved beam theory was proposed.By taking a parabolic-shaped canal in Hebei Province of China as example,distributions of section axial force,bending moment and normal stress distribution of the lining section were calculated.The results show that axial force gra-dually increase to the maximum from top to bottom,and all of them are pressures.The lining plate is mainly convex to the inside under the negative bending moment,and only turns from negative to positive to convex to the outside when it is near the bottom of the canal.Because of arc effect,compressive stress occupies the main part,and tensile stress only arises in both insides of lower middle part of the canal lining and outsides of bottom center.These two parts under tensile stress are most likely to crack.The comparative analysis between straight beam theory and curved beam theory was performed to calculate the section stress of the lining plate and make a comparative analysis.It is found that the relative error between the two is 11.78%near the bottom center,and the calculated value of the straight beam theory is small and unsafe,so it is more reasonable to conduct stress analysis based on the curved beam theory.