(1. Department of Earth Science，Sun Yat-sen University，Guangzhou，Guangdong 510275，China；
2. Guangdong Province Key Laboratory of Geological Processes and Mineral Resources，Guangzhou，Guangdong 510275，China)
Abstract：Based on the classical Boussinesq analytical solutions，a set defined by stress and strain state of points，when subjected to concentrated load，with varied spatial location in semi-infinite elastic subgrade and constrained by certain conditions，is employed to characterize the stress and strain state of a fixed point in the subgrade during the loading-unloading process induced by a single vehicle load. Dynamics，consequently，is transformed into quasi-statics，and analysis model，which is supposed to be convenient and practical for verifying subgrade dynamic behaviors，is established. Stress state and effective working radius are approached and determined during a loading—unloading process in subgrade. Results indicate：(1) curves of dynamic normal stress differences( ) and ( ) are pulse shape，while( ) changes in a twin peak manner；(2) the maximum principal stress might whirl abruptly about z axis，and the angle intersected with z axis rotates gradually and continuously by 180°；the orientation of minimum principal stress turns in a relatively smooth pattern and its rotation features are less remarkably；while the intermediate principal stress direction alters elusively；(3) effective working radius，which represents the limit of impacts exerted by a single vehicle loads on subgrade，pavement system，is suggested to a length of 10 m，and the influenced area can be considered as a semi-sphere with a radius of 10 m and whose center sited at the point of load. At last，the validity of effective working radius，which is defined by 10 m under one vehicle loading，is specified by in situ monitoring data.
2011, Vol. 30 
