Long-term Settlement Control Of Operating Expressway Treated By Lateral Radiation Grouting Technique And Reinforcing Mechanism

Long-term settlement of operating expressway is a key problem to be solved in geotechnical engineering.Besides of a long process of consolidation,significant cumulative settlement of soft soil is also due to cycles of traffic loads.Settlement of operating expressway of soft soil areas has become a concerned problem as increasing traffic,while in previous research,operating conditions of expressway are often neglected.For operating expressways,traffic would be limited or closed due to ground improvement with ordinary methods.The whole operating process is also seldom considered in previous settlement analysis.So it is essential to analyze long-term settlement tendency before and after construction with a reasonable ground improvement method.In the background of field test of settlement treating program of inshore expressway of soft soil area in Jiangsu Province,this research work analyzed the ground heave of expressway caused by lateral radiation grouting technique;A serial of 3D stress-pore pressure coupled FE analysis was calculated to analyze compensation and mechanical modification effect due to lateral radiation grouting;Cumulative plastic strain model was adopted to calculate the expressway settlements trend before and after grouting which were induced by traffic load.The specific works in this research were presented as follows:(1)Spherical cavity expansion of half-infinite medium with undrained condition was adopted to analyze the ground heave induced by cavity surface displacement,and then established a displacement-superposing model for multi spherical cavity expansions to calculate ground heave induced by lateral radiation grouting.Limit grouting pressure was analyzed by using finite boundary spherical cavity expansion with the assumption that grouting bubble expanded as spherical cavity.A method to calculate expressway ground heave due to lateral radiation grouting was proposed,in order to take the relationship of grouting volume,pressure and ground heave into consideration.(2)Based on the field test results and monitoring data,a serial of FE models was established which consider the traffic load as static load.The influences of grouting amount,mechanical modifications and compensation effect was analyzed,and the settlement trends were then calculated.The conclusion that controlled settlement ratio was increasing with advancement of treating time was drawn by the parameters analysis of grouting amount,treating time and soil physical parameters.(3)Cumulative plastic strain method was adopted to calculate the traffic-induced long-term settlement trend of the expressway.The parameters variation before and after grouting was confirmed by analyzing the physical meaning of each parameters and the lab test results of field samples.The reduction of traffic-induced stress deviators after lateral radiation grouting was analyzed,and equivalent traffic load cycles was proposed and then used to calculate the variations of traffic-induced settlement after grouting.The conclusion that stress was spread from grouting area to lower soil layers after grouting and traffic-induced settlement was transfer to deeper soil layers was found by calculating the settlement distribution along the ground depth.Traffic-induced settlements of different treating times were calculated,and the controlled settlement ratio reached 40~80% after grouting.