Study On FWD Standard Testing Protocal And Temperature Correction For Deflection Of Asphalt Pavement

Nondestructive deflection testing using falling weight deflectometer has developed since late seventies of the twentieth century ,which has features of fast testing speed ,high precision and easy operation . The complete deflection basins testing by FWD provide the basis of analyzing pavement layer material properties. Currently there are more than 130 FWDS using by China's road departments,however ,due to lack of appropriate standards and uniform testing methods ,the objectivity,representativeand accuracy have not an effective guarantee which affect use and promotion of FWDs.This paper,supported by the item of"Study on the Indicators and Parameters-Structural performance evaluation of Asphalt Pavement",Which sponsored by Western Communications Construction Scientific and Technological Project.By comparing and analyzing FWD testing methods at home and abroad ,plus with the experience of actual FWD detection and visiting the FWD using units ,the FWD standard testing protocol for China is formulated.By using the data of full-scale test section,the variation trend of temperature field and temperature gradient in different weather condition(sunny,overcast,cloudy) is obtained. Through comparison of exsiting asphalt pavement temperature predicting methods at home and abroad, Bells3 model can be used in China's asphalt pavement temperature prediction.By analyzing the temperature data using statistical method in different weather condition(sunny,overcast,cloudy),the simple temperature prediction model is established.Temperature has significant influece for the asphalt pavement.At high temperature,the asphalt concrete softening phenomenon occurs ,resulting in larger overal deflection and smaller modulus.At low temperature,the asphalt concrete hardening phenomenon occurs,resulting in smaller overal deflection and larger modulus.Thus,FWD testing defelction data should be corrected to the standard data at standard temperature or other representative temperature. The asphalt pavement can be devided into several subgroups based on subgrade modulus,base modulus,base thickness and surface layer thickness.The asphalt pavement deflection correction method containing table method and formula method are obtained by using BISAR3 to analyzing various asphalt pavement deflection pavement correction factor.At last,classify the deflection basin indicators,and then do correlation index analysis of each indicators,the conclusion of DRi is more suitable to correct the FWD other point deflection is gained.Meanwhile,the FWD other point deflection correction methods is established.