Study On Unloading Criterion Of Surface-layer Improvement Technique Of Slurry Stratum

At present, in order to shorten the time of construction of the land reclamation project,generally using vacuum preloading to reinforce the surface-layer of slurry stratum. Due to the purpose of surface-layer improvement technique is bearing ability, the ground settlement is not strictly controlled, existing unloading criterion can not be totally applied to surface-layer improvement technique treated by vacuum preloading.This paper aims to study the relationship of sedimentation rate and foundation bearing capacity, establish the calculation method of unloading criterion, provide theoretical guidance to determine the time to stop the shallow reinforcement. The main work is as follows:(1) Collect the existing engineering, summarize the engineering mechanics properties of newly hydraulic fill silt. Meanwhile, introduce how the reinforcement technology works.(2) After analyzing the possible failure modes of the shallow foundation during the deep-layer reinforcement, the calculation method of the possible modes are given. Equations of undrained shear strength of shallow improvement of foundation with dredged slurry are derived accounting for bearing capacity failure and punching failure during improvement of deep soft strata.(3) According to the relationship between the undrained shear strength of the soft clay and the effective consolidation stress, and the relationship between residual settlement and settlement rates considering the the shear strength of soft clay affected by the vacuum unloading, deduce the formula of unloading criterion based on the reinforced shallow sedimentation rate. And analyze the influencing factors.(4) In this paper, apply the unloading criterion to a practical engineering, and analyze the reinforcement effect. Also verify that the unloading criterion derived in the paper through existing projects.