基于周向冻缩变形协调的衬砌渠道防冻胀纵缝计算方法

CALCULATION METHOD OF ANTI-FROST HEAVE LONGITUDINAL JOINTS FOR LINING CANAL UPON THE COORDINATION OF CIRCUMFERENTIAL FREEZE-SHRINKAGE DEFORMATION

寒区渠道基土法向冻胀引起渠周收缩与刚性衬砌变形不协调,造成衬砌冻胀破坏。设置纵缝是规范中防止冻胀破坏的主要措施,但纵缝位置及宽度尚无法确定。该文在充分考虑开放与半开放环境下冻胀特点下,根据变形协调条件建立了多种典型断面渠周冻缩量计算的数学模型,进一步通过理论推导给出了渠周收缩计算公式及分布规律,经渠道冻胀水热力耦合模型验证其正确性;给出了渠周冻缩量的计算方法及渠周冻缩率的分布规律,分析了断面冻缩敏感性;从变形协调角度给出了纵缝布置及最小缝宽的确定方法。结果表明:断面形状的冻缩敏感性为:梯形>抛物线形>弧底梯形/弧脚梯形/U形;半开放系统α<55°、开放系统α<70°时,抛物线形渠道冻缩量大于其他形式;断面曲率是否连续决定了冻缩率的变化幅度;宽浅式渠道渠周冻缩率小于窄深式,宽浅式弧脚梯形或弧底梯形渠道冻缩分布最均匀,抗冻胀性能最优越;抛物线形仅适于窄深式断面。为了消除变形不协调导致的冻胀破坏,可以在渠周冻缩率突增处设缝,即梯形渠道坡脚处,抛物线形渠道在渠底中心,弧脚梯形/弧底梯形/U形渠道在直线与曲线交界处。研究可为寒区渠道防冻胀工程建设及设计规范修订提供理论参考。

The uncoordinated deformation between the contraction around a canal and the rigid lining caused by the normal frost heaving of the canal foundation soil is the main cause of the frost damage to the lining.Setting longitudinal joints is the main measure to prevent frost damage in the specification,but their positions and widths cannot be determined.In this paper,the frost heaving characteristics of the open and semi-open environments were considered,and a mathematical model for calculating the frost shrinkage around canals of various typical sections was established according to the deformation coordination conditions.Subsequently,the calculation formulas of the shrinkage around canals were derived and then verified by the canal frost heaving model with moisture-heat-mechanical coupling.Finally,the distribution and sensitivity of the freezing shrinkage around the canal and the method were developed to determine the layout and minimum width of the longitudinal joint.The results show that:the freezing shrinkage sensitivity of section shape is trapezoid,parabola,trapezoid with arc bottom/trapezoid with arc toe/U-shape from high to low.Whenαis less than 55°under a semi-open system orαis less than 70°under an open system,the freezing shrinkage of a parabolic canal is larger than other forms.Whether the curvature of the section is continuous determines the variation range of the freeze-shrinkage rate.The freezing shrinkage rate of a wide-shallow canal is less than that of a narrow-deep type one,and a wide-shallow trapezoidal section with arc toe or arc-bottom has the most uniform freezing shrinkage distribution and the best frost heaving resistance.The parabolic shape is only suitable for narrow-deep sections.To reduce the frost damage caused by uncoordinated deformation,the joint should be set at the section with a sudden increase of freezing shrinkage rate,and the joint positions of canals with different section shapes are as follows:slope toe for the trapezoidal canal,bottom center for the parabolic canal,and junction of the straight and curve lines for the trapezoidal canal with arc-bottom or with arc toe or U-shape canal.The research results can provide a theoretical reference for the anti-frost heave design of canals in cold regions.