| With the continuous increase of road mileage in our country,how to evaluate the pavement structure performance reasonably has a huge market demand.As an important component of the road surface non-destructive testing equipment,FWD has been widely used.However,the accuracy of the inversion of the pavement structure layer modulus using FWD detection data is affected to a certain extent by the buried depth of the shallow rock layer.Although the rock depth can be obtained by drilling and coring(DCP),these operations require a lot of time and resources,which obviously cannot meet actual needs.In this paper,first,by simulating the mechanical response of different pavement structures under the action of half-sine load,the time history curve of road surface deflection at each rock layer depth is obtained.By comparing and analyzing the sensitivity between each structural layer parameter and the deflection curve parameter,the curve parameters closely related to the soil foundation modulus and rock layer depth are screened out,and the calculation method of the soil foundation modulus using curve parameters is improved.Secondly,the study of the error law caused by the buried depth of the rock layer during the modulus inversion process shows that the existence of the rock layer will cause the FWD inversion to seriously overestimate the modulus of the soil foundation,leading to hidden engineering hazards.The inversion efficiency and accuracy can be effectively improved by bringing in the calculated rock depth.However,it is the simplest and most accurate method to predict the depth of the rock layer directly from the road surface deflection time history curve.Finally,by judging the influence boundary of the rock layer depth,combining the data group processing method(GMDH)and the principle of stress wave propagation,a rock layer depth calculation model is established.According to the different sections of the calculation results,the pavement structure layer thickness correction,stress wave propagation period correction and compression wave speed correction were carried out respectively,and finally a simple and reliable rock depth calculation model was obtained.Using the FWD and DCP detection data provided by LTPP,combined with the existing problems in the project,further adjust the rock depth method... |
