梯形渠道Kerr冻土地基梁模型及断裂力学分析

KERR FROZEN SOIL FOUNDATION BEAM MODEL FOR TRAPEZOIDAL CANALS AND ITS FRACTURE MECHANICS ANALYSIS​

  • 摘要: 现有寒区衬砌渠道冻胀断裂力学分析方法未考虑基土冻胀变形与衬砌体的相互作用及衬砌板冷缩引起的温度应力的影响,需要进一步完善。基于此,采用三参数Kerr地基模型描述冻土与衬砌间的相互作用,导出控制微分方程并结合待定指数函数法和卡丹公式获得衬砌板冻胀变形解析解。通过静力平衡条件导出温差作用下的切向位移控制方程,通过求解该方程进一步得到温度应力解析表达式。假设初始裂纹随机分布,基于线弹性断裂力学理论提出综合考虑衬砌冻胀弯曲变形和负温效应的寒区梯形渠道冻胀断裂力学分析方法,并给出了确定危险截面位置的方法及抗裂验算准则。以塔里木灌区某梯形渠道为例,应用该文方法、Winkler模型及有限差分法计算衬砌冻胀变形,并与观测值对比,验证Kerr模型的合理性。参数分析结果表明:随天然冻胀量、温差绝对值、初始裂纹长度的增大,各截面应力强度因子均不同程度地增大;如果忽略负温效应将低估危险截面应力强度因子,使计算结果偏不安全;位于渠坡衬砌板中下部的初始裂纹更加容易失稳扩展并导致结构断裂,与灌区现场调查结果基本相符。该研究可为寒区梯形渠道衬砌结构的抗裂验算提供参考。

     

    Abstract: The current fracture mechanics analysis approach for assessing frost-heaving damage in lined canals located in cold regions lacks the consideration of both the interaction between frozen soil and the lining structure and the influence of temperature-induced stress caused by thermal contraction of the lining. In light of this, the three-parameter Kerr model is utilized to elucidate the interaction between frozen soil and lining. The governing differential equations are systematically derived, and an analytical solution for the frost heave deformation of the lining plate was obtained by combining the undetermined exponential function method with the Cardano formula. The governing equation for tangential displacement induced by temperature variations is derived under the conditions of static equilibrium. This equation is subsequently solved to yield an analytical expression for thermal stress. A comprehensive fracture mechanics analysis method for trapezoidal canal linings is proposed, which accounts for both the bending deformation caused by soil frost heave and the effects of subzero temperatures in accordance with the principles of linear elastic fracture mechanics theory. Guidelines for identifying the most vulnerable sections and establishing frost-heaving fracture criteria for concrete lining are provided. Using a trapezoidal canal in the Tarim Irrigation District as an example, the article employs the traditional Winkler model, the finite difference method, and the presented approach to calculate the frost-heaving deformation of lining plates. The obtained results are then compared with observed values to validate the rationality and applicability of the model proposed. The parametric analysis indicates that the stress intensity factors of each lining section exhibit varying degrees of augmentation in response to the increase in natural frost heave amount, of the absolute temperature difference, and of the initial crack length. Neglecting the subzero temperature effects will lead to an underestimation of the stress intensity factor in the most vulnerable sections, thereby introducing a bias toward unsafe conditions in the calculation results. Cracks situated in the lower middle section of the lining plate are more prone to unstable propagation, which can ultimately result in structural failure. This finding is consistent with the results obtained from the on-site investigations conducted within the irrigation area. These study results will serve as a valuable reference for anti-crack calculations related to concrete lining structures in canals in cold regions.

     

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