Research On Treatment Technique Of Joint Section Between New And Old Highways

Now many expressways are confronted with embankment linking and widening, which induce uneven settlement and pavement cracking along the joint between the old and new embankments. On soft ground embankment widening also possibly causes embankement slide. But now the systematic analysis of performance and treatment techniques of the joint section are scarce.A numerical model based on plane strain finite element method (FEM) is used and its theoretical hypotheses are Biot consolidation theory and Duncan-Chang hyperbolic soil model. The influences on embankment and groundwork in the joint owing to widening are analyzed, including uneven settlement, horizontal displacement, stress condition and stability.In order to reduce uneven settlement in the joint, four treatment techniques including embanlment reinforcement, light embankment, cement deep mixing pile and separating wall are compared in mechanism and applicable condition. Their function and parameter sensitivity are also discussed. A suggestion of choosing treatment technique is put forward. Four centrifuge model tests are carried out for different widening projects. The development of settlement, horizontal displacement and pore water pressure in widening are specialized. Comparison is made between test data and calculated results. The tensile strain of reinforcement is measured in the centrifuge model test. Besides, in ultimate conditions the failure mechanism of widening embankment is discussed and analyzed.Finally, the settlement criterion in the joint is analyzed and put forward based on the influence on pavement structure caused by uneven settlement. It is suggested that the permanent deformation of soil should be considered in pavement structure design.