渗透注浆是修建隧道穿越富水砂层时防渗堵水的重要方法之一。与普通化学浆液不同的是，该渗透型高聚物在浆液扩散过程中具有双组份反应并快速固结的特点，适用于在富水砂层中注浆堵水。然而由于其扩散过程中的快速固结的特点，使得其在富水砂层的扩散规律更为复杂。为了研究该渗透型高聚物在富水砂层中的堵水效果，制作了一套可视化的富水砂层渗透注浆模型试验装置，该装置具备可观察浆液扩散距离、监测注浆前后孔隙水压力变化和测量堵水率等功能。以堵水率、渗透系数作为评价富水砂层渗透注浆堵水防渗效果的性能指标，选取砂层粒径、动水压力、注浆压力和黏性土含量4个因素作为渗透注浆的影响因素，开展了砂层渗透注浆堵水防渗效果的正交试验，获得了影响渗透型高聚物浆液在富水砂层渗透注浆效果的主控因素以及各单因素对注浆效果的影响特征。同时，对模型试验进行了数值模拟，重点分析了注浆过程中的浆-水两相渗流场压力、流速和浆液扩散的变化过程，并与试验实测浆液扩散距离进行了对比验证。研究结果表明：1）富水砂层经渗透型高聚物注浆后，10min内堵水率可达到90%以上，1d渗透系数可达到10-7cm/s数量级，达到了理想的堵水防渗效果；2）在一定注浆压力范围内，注浆压力是控制富水砂层注浆堵水防渗效果的主控因素，随着注浆压力的增大，10min内堵水率逐渐增大且砂层1d渗透系数显著降低；3）浆液反应结束后，浆液能扩散到的砂层位置处，孔隙水压力接近0；4）数值模拟结果表明，浆-水两相渗流压力场从注浆孔向出水边界递减，顺水段渗流速度受水流冲刷明显大于逆水段，浆液存在逆水扩散现象，扩散距离的模拟结果与固结体实测结果误差不大；5）通过多元线性回归分析，得到注浆堵水率、固结体1d的渗透系数与动水压力、注浆压力、砂层粒径、黏性土含量的回归方程。

This article studies the quantitative relationship between the target reliability index and the design service life for concrete main girders of cable-stayed bridges. A resistance degradation model of the concrete components is established by quantifying the effects of concrete carbonation and steel corrosion. It is assumed that the dead load and the live load are time-invariant with the distributions of normal and extreme type I, respectively, while the resistance is considered as time-variant with the distribution of lognormal. The standard values of the most unfavorable moment under dead and live loads are calculated by ANSYS, its mean value and standard deviation are further obtained using the statistical parameters suggested by the Unified Standard for Structural Reliability Design of Highway Engineering. The mean and standard deviation of resistance are obtained using the target reliability index value provided in the code above. The resistance value and reliability index at different times in a certain design service life can be obtained through the resistance degradation model. The result shows the reliability index decreases exponentially during the service life of the structure. For different design service years, different initial resistance values and initial reliability indexes can be deduced. Based on this, the target reliability index values considering the design service life are suggested. In the example analysis, the target reliability index of the concrete main girder of a cable-stayed bridge with a design service life of 100 years is suggested as 6.24. This research provides references for the design of concrete main girders of cable-stayed bridges.