Performance Analysis of Slurry After Sewage Infiltration in Pipe Jacking Construction of Subway Station Entrances and Exits Project

Objective During pipe jacking construction, aging sewage pipes within the construction area are prone to rupture, leading to sewage infiltration into the thixotropic slurry along the soil body, thus impacting the performance of the thixotropic slurry to some extent. In order to ensure the construction safety, it is necessary to study the change law of performance indicator after sewage infiltration of the thixotropic slurry. Method Using the No. 1 entrance and exit project of Baohua Street Station on Jinan Rail Transit Line 2 as a case study, combined with the construction conditions of the sewage pipe rupture due to the jacking pipe underpass at the entrance and exit of the station, the change law of the thixotropic slurry performance indicators after sewage infiltration is studied, and the sewage infiltration impact on the drag reduction effect of thixotropic slurry is analyzed by drag reduction test. Result & Conclusion After sewage infiltration, the performance of the thixotropic slurry deteriorates, with a reduction in slurry funnel viscosity and a significant increase in water separation rate and water loss. The positive charges of inorganic salts in the sewage and the negative charges of the slurry soil particles attract each other, causing the slurry Zeta potential dropping from a stable 31.0 mV to below 20.0 mV. Sewage infiltration results in a noticeable increase in the mass fraction of large-size soil particles, and aggregation and precipitation of the slurry, this is the reason for the significant increase in slurry water separation rate. Sewage infiltration also leads to the decrease in the slurry drag reduction effect, with an increase in the friction factor and pipe jacking thrust.