级配碎石基层沥青路面FWD反算模量换算系数

Conversion coefficient for backcalculated modulus of unbound aggregate base asphalt pavement

为了获取真实反映沥青路面结构力学特性和材料性状的结构模量参数，铺筑了4种结构级配碎石基层沥青路面足尺试验路，对其进行加速加载疲劳破坏试验和路面弯沉检测。基于FWD弯沉测试方案，应用分层检测分析方法逐层检测了路面结构层的弯沉，并根据足尺路面加载破坏的损坏程度，进行了路表FWD弯沉测试和弯沉迭代反演，分析了FWD反算模量受荷载水平、位置和路面温度的影响规律，建立了FWD反算模量与实验室动态模量的关系，提出了沥青混凝土、级配碎石和路基土实验室动态模量与FWD反算模量的换算系数K。研究结果表明：沥青混凝土模量受温度和轮载作用的影响最大，路面结构完好的沥青层反算模量换算系数 K＝0．7～1．0；路面出现Top-down开裂后，K＝1．3～1．5；沥青层层底出现疲劳破坏时，K＞1．5；级配碎石层反算模量换算系数为1．32～1．49；土基反算模量换算系数与其所受的应力水平及土质类型相关，随应力水平的降低，土基反算模量换算系数减小。

In order to get pavement structure modulus w hich can real reflect pavement mechanical characteristics and the properties of pavement materials ,four kinds of full-scale unbound aggregate base asphalt pavement test road are constructed ,accelerated pavement testing is conducted and pavement deflection is tested .Based on FWD testing program ,layered measure and analysis method are introduced to measure deflections ,FWD deflection testing is conducted in different stages of pavement damage . T he influence characteristics of loading level ,position and pavement temperature on FWD backcalculated modulus are analyzed ,the relationship between FWD backcalculated modulus and laboratory dynamic modulus is established ,and the conversion coefficients of asphalt concrete ,unbound aggregate and subgrade soil are put forward .The results show that the asphalt concrete modulus is greatly affected by temperature and w heel loads ,asphalt layer backcalculated modulus conversion coefficients is of 0 .5 to 1 .0 if the pavement is in good condition ,and it is of 1 .3 to 1 .5 if pavement top-dow n cracking is occurred .If the pavement is damaged at the bottom of the asphalt layer ,the conversion coeefient is more than 1 .5 .The conversion coefficient of unbound aggregate is of 1 .32 to 1 .49 ;the subgrade soil backcalculated modulus conversion coefficient is related with stress level and soil types ,the conversion coefficient of inverse modulus for soil base decreases with decreasing stress .