Emulation Analysis On Asphalt Pavement Structure Stress And Jointing Of Widened Subgrade

With the rapid growth of traffic volume, a great part of the existing freeway can’tmeet the growing traffic demand, thus widening of freeway in our country has become ahot topic in highway construction. The design for freeway widening is different from thenew project that some key technical problems need further study. Most of the currentresearch is mainly on the prediction and control of uneven settlement on the new and oldsubgrade, while under uneven settlement stress analysis and jointing between the new andold pavement is rarely investigated of which no overall applicable theory has beenachieved.This paper used finite element simulation on Beijing-Hongkong-Macao freeway（Beijing-Shijiazhuang project）. Firstly, the settlement patterns of Embankments withdifferent heights (the depth of fill is1.6m and5.0m separately) was analyzed, secondly,the stress analysis on asphalt pavement structures based on the actual subgrade unevensettlement pattern was made, comparing with that of commonly simplified settlementpattern. Through the orthogonal test analysis, the influence of overlap thickness, modulus,Poisson’s ratio, the new surface layer modulus, base modulus and sub-base modulus on thenew and old pavement structure was analyzed and the optimal parameter values weregiven. Finally, the new and old pavement overlap dimensions and lapped joint locationwere analyzed.The results show that: a) Low embankment shows "~" type uneven settlement underactual settlement pattern, its pavement structure bear the additional tensile stress on lappedjoint ("~" curve convex) and large reverse bending tensile stress occurred on base(sub-base)("~" curve concave)of the newly built pavement, moreover base(sub-base)may cracked earlier than pavement;b) The high embankment is mainly affected by tensilestress from top of the lapped joint whereas the reverse bending tensile stress is not obvious.Simplified settlement pattern cannot accurately reflect the pavement structure damaginglayer and the failure point. c)30cm overlap step should be reserved between the new and old base and sub-base. The relative disadvantageous load range was analyzed and the jointlocations were determined separately when there were one step and two steps at surfacelayer.