Frictional behavior of rock pipe jacking in mixed solutions of varying pH with coexisting debris

Previous studies have indicated that the sudden increase in jacking force and pipe sticking in the Guanjingkou rock pipe jacking project is closely associated with mud cake formation from crushed debris. To address this issue, acidic and alkaline solutions are applied on-site to corrode the mud cake and restore jacking progress. However, during the rainy season, these solutions may be transported backward by rainwater, potentially affecting subsequent pipe sections. To investigate whether the coexistence of karst water and acid and alkaline cleaning solutions influences the frictional characteristics of subsequent pipe sections, this study combines indoor direct shear tests, scanning electron microscopy (SEM), and field monitoring. The frictional characteristics at the pipe-rock interface under different pH conditions and debris mixing scenarios are systematically investigated, and the effects of key factors on the friction coefficient are analyzed. By comparing predictions from the experimental model with field monitoring data, the reliability of the results is verified. The findings provide a theoretical foundation and practical guidance for friction control and pipe sticking mitigation in karst environments.