Model Experimental Study On The Residual Stress Of Ultra-soft Ground Static-Dynamic Drainage Consolidation Treatment

Static-Dynamic Drainage Consolidation Method is a kind of soft soil foundation reinforcement technology developed in recent years,especially for the treatment of soil silt, silt soft soil foundation,The basic idea of the method is by setting artificial drainage system,under the effect of the amount of static coating and dynamic load and the sustained residual stress,pore water will continuously discharge rapidly,and then the purpose of soft foundation reinforcement has been reached,However, after impacting the residual stress of reinforcement that kept by static covering is usually not be taken seriously,from the point of static dynamic drainage consolidation method of soft soil engineering treatment and indoor model test,under certain conditions there is residual stress in soil,and it has engineering effect,in order to find out the residual stress mechanism in static dynamic drainage consolidation method in ultra soil ground treatment,the indoor model test of high impacting load was carried out and the residual stress related problems were studied.In this paper, at first a variety of consolidation theory of ultra-soft soil and the research status of metal residual stress and Static-Dynamic Drainage Consolidation Method research status at home and abroad are reviewed, and then the concept of residual stress of metal is introduced into soft soil,ZW-HEIA has being utilized to do the indoor model test of soft clay under static and dynamic loads,on the basic of experimental data of the model test,the magnitude of the residual stresses is calculated,residual stress time dependent curve were drawn,the existence of residual stress is verified and the law of change is explored.The relationship between residual stress and effect of drainage system,total stress.pore pressure,settlement were analyzed and discussion.At the same time,model test results and field actual engineering data are comparative analyzed.tne actual engineering residual stress has been validated and the reliability of the model test results is demonstrated.the residual stress calculation formula is deduced,and the calculated values were compared with the model test values.The main research results in this paper are as follows:(1) The residual stress is structure force which is the additional load caused by the combined effect of force and restraint.the available residual stress formula of soil is verified again. There is no obvious residual stress under the action of static mechanism,it can be neglected;stress increases with the increase of the tamping number of times; with the increase of tamping number the residual stress effect transferring from shallow to deep.(2) The setting of drainage plate has important influence on the maintenance and accumulation of the residual stress;the better effect of the drainage system is,the greater the residual stress is.When the pore pressure is reduced, the residual stress increase;when the pore pressure is kept constant, the residual stress is also in steady state;and when the pore pressure increases, the residual stress decreases,this rule is more and more obvious with the increase of the dept.The change trend of the residual stress and total stress are basically the same.Field test data show that:the depth of residual stress effect increase with the crease of the load of static coat,under the circumstance that the energy of tamping kept the same,the residual stress decreases with the increase of depth,the residual stress increase with tamping energy increases at the same depth.(3) On the basis that additional stress’energy which generated by static load and dynamic load and constraints,the formula of residual stress is deduced.This paper explores and validates residual stress mechanism in foundation reinforcement of the ultra-soft soil (mainly silt and silty soil) under the joint action of cover layer, impact load and drainage system. Theory of Static-Dynamic Drainage Consolidation Method is easy to understood, reference are provided for both design and construction when Static-Dynamic Drainage Consolidation Method is utilized in ultra-soft soil foundation treatment.