Stability Analysis Of Deep Soft Soil Excavation Of Cement-soil Reinforcement In Passive Zone

In the soft soil excavation,due to the properties and thick soil layer,soil pressure in the passive zone is not enough,this leads to the restriction from the base to pile becoming weak.In the design of excavation supporting system,the improvement of restriction is achieved by increasing the pile length.But this will result in higher budget and the effect is not very obvious.Reinforcement in passive zone by using cement-soil will generate soil pressure,enhance excavation capacity and provide build-in force for piles.Overall,reinforcement in passive zone is an economical and effective technical method.Due to the time effect on properties of reinforced soil,until now,no theory is raised which considers cement-soil,soft soil and supporting pile at the same time. Based on this topic,this paper focuses on the research of cement-soil reinforcement, time-effects on its strength in Nansha area.And apply experiment result into calculations,which is described as follows.Take a practical project for case study,analyze the micro structure of cement-soil,research on its reinforcement mechanism;in the meanwhile,conduct unconfined strength test respectively under 7d,14d,28d,90d,as per different cement content,water cement ratio,additive.Obtain relevant properties of cement-soil as well as the fact that strength changes in terms of time.Conclusion is derived on the methods for the excavation supporting system in deep soft soil zone.Reinforcement design for passive zone and analysis of excavation stability are presented via specific project case study.The analysis is undertaken in consideration of the fact that the cement-soil strength is changing towards time,this is achieved by adopting different strength factors in passive zone.Numerical modeling and finite element analysis are performed for the reinforced deep soft soil excavation and excavation supporting system in the passive zone. Drucker-Prage material model is adopted for the cement-soil and soft soil in the modeling process;pile and excavation support is modeled as beam element.Result which is derived from experiment is applied,and consider construction time interval, different cement-soil strength regarding to different concrete age are used.The characteristic of excavation deformation and stability is monitored,which is under the consideration of cement-soil,soft soil and supporting element.Moreover,accurate analysis is undertaken,which is on the effects of cement-soil strength change towards excavation stability and deformation in terms of construction steps.Therefore, theoretical basis and practical reference are provided to such medium-small excavation supporting system and construction procedures in deep soft soil.