Experimental Study and Variability Analysis of Strength Parameters in Passive Zone Reinforcement of Soft Foundation Pit

Passive zone reinforcement is an effective deformation control method, which has been widely used in soft soil deep foundation pit engineering, but there are few reports about the measured strength parameters and its variability analysis of the passive zone reinforcement. Based on a soft clay deep foundation pit in Wuhan area, in-situ cone penetration tests, dynamic penetration tests, and laboratory unconfined compressive strength tests were carried out, and its correlation between the laboratory unconfined compressive strength parameters and in-situ test indexes was established for the passive zone reinforcement. Through the established empirical formula, the continuous in-situ test data were converted into unconfined compressive strength values, and the variability and distribution of strength parameters of the passive zone reinforcement were discussed by statistical analysis. The results showed that there were significant differences between the strength of the passive zone reinforcement and the undisturbed clay, compared with the empty pile with 10% cement content above the bottom of the pit, the strength of the solid pile with 20% cement content below the bottom of the pit was not significantly increased. The strength of the passive zone reinforcement has strong nonuniformity in both empty and solid piles, and the variation coefficient of the empty pile was larger than that of the solid pile. The distribution of cement-soil strength for the empty pile with low cement content was fitted by an exponential distribution, while that of cement-soil strength for the solid pile with high cement content was approximately lognormal.