混凝土防渗渠道冬季输水运行中冻胀与抗冻胀力验算

为了明确渠道冬季输水时防渗衬砌层结构的抵抗渠床基土冻胀破坏作用的能力,该文理论分析了大气负温下,介入刚性防渗面层对渠基土冻胀的约束,得到作用于坡板上冻胀力的作用形式为法向冻胀力和指向坡顶的切向冻胀力,对被视为底端简支、板内无接缝、受冻胀作用的构件受力进行理论分析,得到冬季输水渠道边坡板的冻胀问题属于非垂直非全周的冻拔问题的结果,并进一步根据力学基本原理研究了刚性面层(衬砌层)承受荷载力的求解方法。依据桩的抗冻拔验算和拉弯构件的强度验算可实现冬季输水渠道抗冻胀力的计算,建立了适用于防渗渠道刚性衬砌结构设计的方法,为冬季输水梯形混凝土防渗抗冻胀渠道衬砌层厚度的准确确定提供了计算方法。

Frozen heaving and capacity of frozen heaving resistance of trapezoidal concrete lining canal with water in winter

Abstract: The trapezoidal canal with the anti-seepage and anti-scour concrete lining is widely used in water conveyance project. However, the impervious effect of the canal in the seasonally frozen region doesn't work because the frozen heaving of the bed soil causes the concrete lining damage. The forms of frozen heaving force, which were caused by rigid concrete lining's confining the deformation of the canal bed soil, were analyzed for the different coupled field of temperature and water content in the canal bed soil under atmospheric negative temperature, by means of studying the change of the canal slope length with the formation mechanism of tangential frost-heave force. The conclusion was drawn that if the slope was shorter during frozen period than that during unfrozen period, tangential frost-heave force, pointing to the top end of the slope slab, would act on the undersurface of the concrete lining and vice versa. In fact, there are 2 kinds of frozen states of the bed soil in the section of the canal. One is that the bed soil below the whole concrete lining is frozen, which is mainly presented in the canal used for irrigation. The other is that the bed soil under the part of slope concrete lining is frozen in the canal providing water for city or factory. In the former, normal frozen heaving force acts on the bottom slab while tangential frozen heaving force acts on the slope slab pointing to the bottom of the slope. In the latter, there isn't normal frozen heaving force on the bottom slab but there is tangential frozen heaving force, pointing to the top of slab, under the slop slab above the canal water level. Many results were attained on the damage of concrete lining caused by bed soil's frozen heaving of the whole section, while few researches on the frost damage of the slope slab in the canal delivering water were carried out, and related researches were focused on ice situation, including the numerical simulation and control of ice situation and the analysis on ice condition. So the next research was on the capacity of frozen heaving resistance of concrete lining slab on the slope bed soil of the canal delivering water in winter. The problem of frozen heaving resistance of concrete lining was changed into that of bearing capacity of concrete structure under the action of frozen heaving force. Because slope slab was originally lain on the bed soil and the slope slab and the bottom slab were articulated, and the slope slab was jointless, the mechanical model of the slope concrete slab was established under the combination of the normal and the tangential frozen heaving forces, the gravity of the slope concrete slab, the water pressure and the frictional resistance under the slope concrete slab. The frost damage of the slope concrete slab of the canal carrying water in winter belongs to the problem of being pulled by frozen heaving. After the magnitude of normal force and tangential force of frozen heaving was calculated based on the force equilibrium and the formation mechanism of tangential frost-heaving force, the solution to the frost damage of the trapezoidal canal carrying water in winter was found. The capacity of frozen heaving resistance of the trapezoidal canal carrying water in winter could be calculated in the light of pulling resistance of pile as long as the anti-seepage concrete lining of the trapezoidal canal carrying water in winter was regarded as the pile suffered from frozen heaving force, which non-vertically acted on a part of lateral surface of the pile. So the method to design the concrete lining structure of trapezoidal canal carrying water in winter, whose core is checking the calculation of anti-pulling strength of the slope slab, was successfully founded.