中文摘要：

南水北调中线工程是长距离串联系统，工程的防洪风险较大，投资规模巨大。如何在结构可靠度与工程造价这对矛盾体中寻求最佳组合，往往是工程规划关注的焦点。以可靠度理论为基础，通过考虑随机因素的随机特征，建立了长距离输水工程交叉建筑物的综合可靠度估算方法，并通过优化算法探讨了南水北调中线工程河北段12座渡槽形成的串联系统的整体可靠度与工程造价的最优分配问题。在保证工程总体可靠度的情况下，给出了各交叉建筑物的最优投资方案和相应的可靠度。

英文摘要：

Crossing Structure Reliability of Water Transfer Project is determined by stochastic characteristics of hydrology, material, geology and structure. All of these aspects impact cost of engineering indirectly or directly. How to resolve the dilemma between cost and reliability is the focus in engineering planning phase. We present integrated flood safety assessment method of launders based on reliability theory and relation between cost and reliability is also set up. The method was applied in Middle Route of South to North Water Transfer Project in Hebei province. Method is a quantitative support for engineering costbenefit evaluation.