Formulation optimization and performance analysis of the thixotropic slurry for large-section rectangular pipe jacking in anhydrous sand

Abstract

When large-section rectangular pipe jacking is performed in anhydrous sand strata, due to the special geological condition and construction specification, there are specific requirements for the performance of thixotropic slurry. In this study, an optimized traditional slurry formula and a nano-modified slurry formula (with 2% nano-SiO2 added) suitable for large-section rectangular pipe jacking in anhydrous sand formations were proposed by conducting an L25 (35) orthogonal test and a two-factor test, respectively. Five indicators were used to select the optimal slurry component proportion and nano-additive and additive concentration, including plastic viscosity (PV), filter loss (FL), water dissociation ratio (WDR), thixotropic value (TV) and yield point (YP). The influence of the component content on the slurry properties was analysed. To preliminarily verify the drag-reducing effect of the slurries prepared according to the formulas, an interface friction test was designed. The interface friction test results show that the optimized traditional slurry can reduce the pipe-soil friction coefficient to 64.7%, whereas the nano-modified slurry is 54.9%. Through scanning electron microscopy (SEM) observations, the micro mechanisms of the slurries were investigated. Furthermore, the formulas were applied in a practical pipe jacking project, and the jacking load and soil settlement were well controlled throughout the application period.