弧底梯形渠道砼衬砌冻胀破坏的力学模型研究

弧底梯形渠道以其抗冻胀性能及水力特性良好,在北方寒旱地区得到广泛应用,但该种形式衬砌的结构计算仍无力学模型,该衬砌体的设计只能凭经验选取,而无法量化.该文通过对弧底梯形渠道砼衬砌冻胀破坏机理及破坏特征的分析,指出了弧底梯形渠道砼衬砌整体结构的计算简图是在法向冻胀力及切向冻结力和重力共同作用下的薄壳拱形结构,就局部受力来看属压弯组合变形问题.通过恰当假设及简化,提出了该砼衬砌整体结构冻胀破坏的力学模型,求出了其冻胀控制内力及最大拉应力的计算公式,并结合砼板抗裂条件,给出了胀裂部位、衬砌板厚及抗冻胀破坏验算的一系列计算方法.理论分析阐明了弧底梯形砼衬砌结构因法向冻胀力数值小、分布均、恢复力大,因此,整体适应变形及抗冻胀能力强,从而更优于梯形断面.实例计算表明该模型安全合理、简单实用.

Mechanics models of frost-heaving damage of concrete lining trapezoidal canal with arc-bottom

Trapezoid canal with arc-bottom is widely used in cold and aridity areas in northem China because of its better capacity of resisting frost-heaving damage and hydraulic characteristic. However, there have not been any accurate mechanics calculation model about this kind of lining structure, the design of this lining structure depends only on the experience, and it can not make quantitative design and calculation. Through the. analysis on the damage mechanism and damage characteristic of the frost-heaving of the concrete lining of trapezoidal canal with arc-bottom, the entire structure can be regard as thin-shell arc structure under the loads of normal frost-heaving force, tangential freezing force and gravity, and this belongs to the problem with both bending and compressing deformation. Using rational hypothesis and simplification, a mechanics models was proposed to analyze the frost-heaving damage of the entire structure with concrete lining, the formula was acquired to calculate the internal forces controlling frost-heaving and the maximal tensile stresses. By considering the conditions of resisting the crack of concrete plates, the calculation methods for analyzing the position of expansion cracks, the proper depth of the lining plates preventing the occurrence of frost-heaving and cracks , and the checking calculation on resisting frost-heaving were proposed. The theory analysis indicate that the concrete lining structure of trapezoid canal with arc-bottom, the normal frost-heaving force is small and uniform, the resilience is large, so it has stronger capability of adapting entire deformation and resisting frost-heaving, and it is better than trapezoid canal. The results of examples show that the mechanics model is safety, rationality, briefness and practicability.