Optimization of thixotropic mud ratio and friction reduction performance for pipe jacking in offshore water-rich soft strata

Abstract

Thixotropic mud plays a vital role in pipe jacking construction, where its excellent thixotropic properties not only provide stratum support but also offer lubrication and friction reduction during pipe advancement. The physical properties and friction reduction performance of the mud are directly related to the efficiency and safety of the construction process. Considering the specific requirements of water-rich soft strata, a new thixotropic mud formulation was proposed using bentonite, soda ash, carboxymethyl cellulose(CMC), and a water-reducing agent. Physical property tests were conducted under different mud ratios to analyze the effects of the water-reducing agent and other components on the mud's viscosity, water loss, and water separation rate. A scaled model test was further conducted to investigate the friction reduction performance of the new thixotropic mud, and parameter normalization analysis was carried out based on stratum characteristics to identify the optimal mud formulation. The result show that the water-reducing agent can adjust the water-cement ratio and promote gel structure formation, thereby increasing viscosity, reducing water loss, and effectively inhibiting water separation. Compared with un-grouted pipe jacking, the new thixotropic mud reduced the friction coefficient by up to 77.1%, and by 38.5% compared to traditional mud without the water-reducing agent, demonstrating significant friction reduction. Pipe jacking in water-rich soft strata requires thixotropic mud with good permeability control and long-term stability. Therefore, the optimal formulation of 10% bentonite, 0.1% CMC, 0.2% soda ash, and 0.5% water-reducing agent was selected. The findings provide effective technical support for addressing poor grouting performance in pipe jacking construction in water-rich soft strata and offer significant application value.

Keywords

water-rich soft strata / pipe jacking construction / thixotropic mud / physical properties / friction reduction performance / mud mix optimization