Dewatering characteristics of waste slurry from pipe jacking based on improved vacuum filtration method

[Display omitted] •Vacuum filtration and curing are used in combination to treat waste slurry.•Waste slurry becomes soil material with certain strength while rapidly dewatering.•Pretreatment of solidification-flocculation increases vacuum filtration efficiency.•Solidifying agent added in pretreatment still enhance strength of dewatered soil.•Strength formation mechanism of dewatered soil is proposed. A large amount of waste slurry with high water content generated in the construction of slurry shield and pipe jacking needs to be reduced urgently. Due to high clay content of the waste slurry, existing treatment technologies such as plate and frame pressure filtration and vacuum filtration encounter problems such as low dewatering efficiency and low soil strength. Aiming at these problems, an improved vacuum filtration method was proposed and verified, which can transform waste pipe jacking slurry with high water content into soil material with certain strength while rapidly dewatering. The new method combines traditional vacuum filtration with curing technology. The experiment results show that after using the new method, the slurry with a water content of 400 % can rapidly drop to 62 % within 150 s, and 7-day unconfined compressive strength of the dewatered soil (q7day) can reach 117.33 kPa. The key mechanism of the improved vacuum filtration method was discussed. The pretreatment of solidification-flocculation increases the dewatering efficiency of vacuum filtration. The solidifying agent added in pretreatment still enhance strength of dewatered soil. Meanwhile, the strength formation mechanism of dewatered soil was proposed. The strength is related to water content of the dewatered soil (ωfinal) and the solidifying agent content (COPC).