Heavy Truck Induced Dynamic Response Of Asphalt Pavement Based On Irregular Stiffness

Heavy truck riding on highway generates severe early damages to theasphalt pavement because overloading which leads to heavier axle loads is verypopular. Irregular stiffness of subgrade will exacerbate heavy truck’s vibrationduring its travelling, which accelerates early damages of asphalt pavement tosome extent. In this dissertation, heavy truck induced dynamic response ofasphalt pavement based on irregular stiffness of subgrade is to be discussed onthe basis of field testing and theoretical analysis. And consequently, the failuremechanism of asphalt pavement based on irregular stiffness of subgrade whichheavy truck is travelling on.The methods of field testing using FWD, elasticity modulus positivecalculation, numerical modeling and parameter analysis are used in thedissertation. Firstly, the problem of composite modulus of subgrade andpavement is studied from a macro level by means of FWD field testing, whichproves that the irregularity of composite modulus of subgrade and pavement doesexist, and it varies in a great range from900MPa to2500MPa. How side slope ofhighway, fill and excavation of subgrade and damage modes of pavementaffecting the composite stiffness is discussed. Secondly, the transformingrelationship of elasticity modulus of subgrade and stiffness of subgrade is builtup. A numerical model of heavy truck, pavement, base and subgrade isestablished, which uses irregular stiffness of subgrade as a stimulant. Then, areasonable mode degree and the availability of the numerical model areconfirmed. Finally, based on the model, various kinds of saltation stiffness ofsubgrade and gradual change stiffness of subgrade are analyzed to discussedwhether and how they will affect the dynamic response of asphalt pavement. Aparticular kind of saltation stiffness of subgrade and a particular kind of cosinecurve stiffness of subgrade are picked up to discuss how they will affect thedynamic response of pavement under he control of different kinds of heavytrucks, different kinds of speed and different kinds of axle loads. When thestiffnenss of subgrade is saltated from different values to0, the dynamicdisplacement of pavement will increase at least3times. When the saltation distance of subgrade stiffness is increased to1time and2times, the dynamicdisplacement of pavement will increase28.0%and57.2%respectively.Compared with40MPa saltated to30MPa, when the subgrade stiffness is saltatedfrom40MPa to20MPa and from40MPa to10MPa, the dynamic displacement ofpavement has increased24%and70%respectively. The increasing tide is gettingfaster. When the minimum stiffness value of cosine curve stiffness of subgrade isdecreased for each10MPa, the maximum dynamic displacement of pavement willamplify1.2times. With the same maximum values and minimun values, whilecosine curves stiffness of subgrade have different periods, the average value ofdynamic displacement of pavement is almost equivalent, but the maximumdynamic displacement for the period of10meters is0.2times larger than that ofthe period of20meters.