Research On Fast Detection Of Pavement Bearing Capacity Based On Vibration Frequency

During the long-term use of road pavement,the mechanical properties of the structure will decrease to a certain extent because of the effect of the vehicle load and other factors.The good performance of the road is not only to prolong the life of the road,but also to ensure the safety of the driving.Therefore,more and more attention has been paid to the monitoring and evaluation of road carrying capacity.At present,Benkelman beam and the falling weight deflectometer are widely used to detect pavement bearing capacity at home and abroad.The Benkelman beam is measured by the static deflection of the road,which can not reflect the real working condition of the pavement structure,and the falling weight deflectometer by applying the heavy hammer impact to simulate the driving single wheel load on the pavement,can not represent the real driving load,and it needs to be sampled during the test.This not only brings great economic impact on the busy road traffic,but also causes the certain security risk in the testing process.Therefore,it is a new research direction to monitor and evaluate the bearing capacity of pavement under the condition of continuous intersection.Based on the support of the national Supercomputer Center of Tianjin(NSCC),through the combination of finite element simulation and theoretical analysis,a theoretical and technical approach to evaluate pavement carrying capacity is put forward.The method is simple,quick,low cost,and can be used to evaluate the road surface under the normal running condition of the vehicle.The specific contents are as follows:1.Considering the influence of road roughness level,vehicle speed and vehicle type,a vehicle road coupled dynamic analysis model is established to simulate the dynamic random load on the road surface under normal driving conditions.2.Based on elastic layered theory,a three-dimensional finite element model of road structure is generated by using finite element software.Considering the vibration characteristics of road,dynamic modulus index is established as the evaluation index of pavement bearing capacity.3.Through a large number of finite element simulation calculations,the influence laws of vehicle speed,rear axle load,road roughness and road structural layer parameters on the road base frequency and the influence depth of soil foundation were analyzed.The calculation formulas of the road base frequency,soil depth of influence and their respective main influencing factors are established respectively,and then the equivalent elastic modulus analysis model of the base roof based on the road base frequency is obtained.According to this model,the bearing capacity of the road surface can be detected by combining the grading standards of the bearing capacity of the road surface.4.Considering the inhomogeneity of the soil foundation in the real road structure,a double layer soil foundation model with soft substratum is established in this paper.The influence of the thickness and modulus of the soft substratum on the fundamental frequency of the road and the depth of the soil foundation is analyzed,and the general rule is obtained by the regression analysis.5.A field test of a newly built asphalt concrete pavement in Hebei province has been carried out,and the test data have achieved good results,which verifies the feasibility of this method.