Experimental Research On High-speed Railway Subgrade Frost-depth In Cold Areas

As a nation abundant in permafrost, China has a total area of permafrost over0.5m in frost-depth that accounts for68.6%of the total territory of the nation,46%of which belongs to seasonal frozen soil. With the vicissitudes of seasons, frost heaving and thawing in subgrade of seasonal permafrost can occur repeatedly and as a consequence lead to uneven frost, posing great threats to railway traffic.With the rapid development of passenger lines and the large-scale construction of high speed railway, ballastless track ratio is greatly improved, which requires stricter control of railway subgrade deformation. Located in the seasonal frozen soil regions in Northeast China, Harbin-Dalian High speed Railway adopts ballastless track structure and as a result faces the challenge in controlling the deformation caused by subgrade frost heaving within reasonable scopes.Based on the subgrade of Harbin-Dalian High speed Railway, this thesis studied the rules in the development of the frost heaving issues in question by examining and analying the temperature fields of42typical sites of2012-2013and of2013-2014acquired by an established automatic frost-depth monitoring system; it conducted a statistical analysis of the characteristics of the freeze index, the maximum frost-depth of the soil, the maximum measured frost-depth and the maximum heave, and a comparative analysis of the relations between frost-depth and freeze index, and of the relations between frost-depth and frost heave; focusing on the typical subgrade lots in Shenyang-Dalian and Shenyang-Harbin High speed Railway, it also conducted a systematic analysis of the rules of frost heave variation on the sites in question and the factors that cause that variation.This paper attempts to reveal the development of the subgrade frost-depth in Harbin-Dalian High speed Railway and its rules, in the hope of providing an important reference for the structural design of anti-frost high-speed railway subgrade in cold areas; it provides a theoretical guidance to the construction of high-speed railway in the seasonal frozen soil area in the future as well as applications in maintenance and renovation.