Deformation Of The Embankment With Riprap Slope Protection At Qinghai-Tibet Railway

The deformation of subgrade is composed of consolidation and creep. The differences on strength and deformation feature between frozen soil and common soil is that frozen soil has obvious irreversible reconstruction under loading. Stress relaxation and creep can develop under very low loads. The strength and deformation of the frozen soil change with time. Along with the variation of seasons, the soil of subgrade changes from unfrozen to frozen and repeats the process again and again.The paper is based on the study of the mutual action mechanism between Qinghai-Tibet railway air-cooled embankment with riprap slope protection at different frozen soil regions. We developed thermal-physical models of frozen soil under different engineering measures. Numerical simulation and analysis of temperature fields, stress fields and displacement fields were done. Finally, we compaired the results of the numerical simulation with the test results at a tested section of air-cooled embankment with riprap slope protection, which is a newly designed structure of the Qinghai-Tibet railway. An experimental project on air-cooled embankment with riprap slope protection and common embankment were conducted at Qingshuihe, a field test section of high-temperature fine grain frozen soil region along Qinghai-Tibet railway. Based on monitoring data of ground temperature and settlement at three sections after two freezing-thawing cycle, the ground temperature, accumulated temperature, maximum thawing depth variation and deformation feature of these two kinds of embankment were analyzed comparatively. It was shown that the air-cooled embankment with riprap slope protection showed better effect on decreasing ground temperature, lowing minor accumulated temperature, elevating the maximum thawing depth evidently and reducing settlement than that of common embankment. Therefore, the air-cooled embankment with riprap slope protection, as a kind of convenient and widely used construction measure, was a positive frozen soil protection measure for its effectively decreasing ground temperature and protecting permafrost.