| China Railway High-speed(CRH) is one of the most important infrastructure construction projects in China. According to the latest government development report, in the following decade, China's railway transport lines will be significantly increased, also, both transport speed and loading will improve overall. Thus, high speed and heavy loading have become future development tendency of railway transportation. This tendency of development has brought great convenience to people, on the other hand, higher requirements to the overall performance of subgrade and mechanical properties of subgrade filling has also been put forward. Therefore,more focus should be added on research for effects of high speed and heavy loading on dynamic performance of subgrade filling.Beijing-Shenyang Railway, a high-speed railway line currently in construction, will connect Bohai Sea and northeast of China. This railway line covers Beijing city, Hebei provinces and Liaoning provinces, and is one of the most important railway lines in our country. B-group medium sand is a very typical soil located all over this area. Carefully references review indicate that few researches could be found related to dynamic behaver of B-group medium sand due to dynamic loading. Therefore, study on both physical and mechanical properties of this kind of soil is very necessary.In this paper, typical B-group medium sand was made using the combination of medium sand and silt clay. A multifunctional triaxial testing system, DSC200, was adopted for studying both static and dynamic mechanical properties of B-group medium sand. Effects of high speed and heavy loading on dynamic strain behavior of soil were mainly studied.Effects of confining pressure and fine particle content on stress and strain behavior as well as static strength were studied through a series of conventional triaxial tests. Both law and the reason for influences of fine grain content as well as confining pressure on static strength were analyzed. Therefore, a strain-stress model was established according to Konder's hyperbolic strain-stress model.Dynamic triaxial tests were conducted on B-group medium sand of different fine particle contents for studying dynamic strain-stress behavior. Effect of characteristics such as confining pressure, dynamic stress amplitude, and fine grain content on dynamic strain-stress behavior were studied. Pore pressure development of soil under dynamic loading was described according to Sakai's empirical formula. Development law for elastic modulus as well as influence of fine grain content and vibration frequency on it was also studied.Cumulative plastic deformation prediction model was established based on Monismith simple exponential model and Sakai's empirical formula, respectively. Miura model was used to describe development law of plastic deformation decay curve, and the relevant parameters were obtained. |
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