**5. Conclusions**

(1) A method for the rapid reduction and reuse of waste slurry from pipe jacking projects has been studied and proposed. Through the combined treatment of flocculation– sedimentation and solidification, the water content of the waste slurry can be reduced to about 159% in a very short time (10 min), and it can be quickly transformed into a soil material with a strength greater than 30 kPa.

(2) The properties of waste slurry from pipe jacking change with the change of excavated stratum, which affects the results of flocculation and sedimentation. The zeta potential of waste slurry containing bentonite is high, which leads to the poor result of flocculation. Through the compound pretreatment of FeCl3·6H2O and APAM, the zeta potential of slurry can be reduced, and better dewatering results can be obtained.

(3) The conditioners and solidification agents suitable for the treatment of waste pipe jacking slurry were proposed. It was found that the optimal flocculation effect was achieved when APAM 7126 (0.06–0.10%) was added. If the waste slurry contains bentonite, 3% FeCl3·6H2O can be added in advance. For sediment after flocculation and sedimentation, adding 20–30% SAC can greatly improve the strength of solidified sediment in a short period of time, which is convenient for subsequent treatment and utilization.

**Author Contributions:** Conceptualization, L.J. and L.Z.; methodology, J.W. and X.H.; software, J.W.; validation, L.J., L.Z. and T.Z.; formal analysis, T.Z. and X.H.; investigation, T.Z.; resources, T.Z.; data curation, L.J.; writing—original draft preparation, L.J.; writing—review and editing, L.J.; visualization, L.J.; supervision, L.Z.; project administration, L.Z.; funding acquisition, J.W. and X.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Shanghai Rising-Star Program(No. 19QB1401800) and supported by China Scholarship Council.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to data which also forms part of an ongoing study.

**Conflicts of Interest:** The authors declare no conflict of interest.
