Traditional slurry circulation systems exhibit several shortcomings, including inaccurate predictions of critical flow velocity, high risk of water hammer impact, and low efficiency in pipeline extension. To overcome these challenges, the slurry circulation system is enhanced and an innovative solution is proposed based on a case study of the Chongtai Yangtze River Tunnel of the Shanghai-Chongqing-Chengdu High-speed Railway. Based on the theory of multiphase flow dynamics, a modified Durand model is developed to improve the prediction accuracy of critical flow velocity under ultra-long distance and high water pressure conditions, where the traditional Durand model has proved insufficient. With the incorporation of a dynamic friction coefficient and concentration gradient compensation mechanism, the model’s core parameters are optimized to improve the accuracy and applicability of critical flow velocity prediction. The risk of water hammer impact damage during the operation of the slurry circulation system is addressed by developing a multistage water hammer protection system that integrates safety valve pressure relief, intelligent visual monitoring, and electric gate valve linkage. A model for water pressure transmission and valve action sequence is constructed to enable real-time monitoring, rapid response, and effective pressure relief from water hammer impacts. Additionally, to tackle the problems of low pipeline extension efficiency and frequent construction interruptions in ultra-long distance projects, an innovative modular pump station integration technology is proposed. This involves a reserved interface design for three-way pipes to realize uninterrupted pipeline extension, along with a low-headroom retractable pipe replacement device that adapts to the spatial constraints of tunnel construction. Engineering practice has demonstrated that an optimized slurry circulation system effectively resolves the limitations of traditional technologies, such as muck retention and discharge blockage, water hammer impact, and interference during pump station installation, achieving a record of zero muck retention and discharge issues while reducing the occurrence of water hammer accidents to acceptable levels. The newly designed low-headroom retractable pipe replacement device successfully enhances operational space for simultaneous lining construction, thereby improving construction efficiency. Practical verification shows that the optimized system exhibits excellent structural stability and adaptability to varying working conditions.