| The change of moisture and temperature is one of the important factors that cause subgradelongitudinal cracks. Qinghai-Tibet highway was constructed to change the balance ofmoisture and heat original system, which caused seriously longitudinal cracks and seriouslyaffected the safety and comfort of vehicle operation. This paper analyzed the influencingfactors and formation mechanism of longitudinal cracks based on road conditions survey, atypical cross-section measure and statistical analysis. The main results are as follows:1）Combining with the natural conditions, the condition of permafrost stability andengineering conditions, the influence factors and distribution features of subgrade longitudinalcracks were analyzed base on field survey, typical cross-section analysis and data statistics.the result showed that longitudinal crack formation is closely relate with height of subgrade,slope direction, frozen soil types, roadside water.2）The change of moisture and temperature were monitored in subgrade at a typicalcross-section(K3020+200). Temperature in subgrade changes lagged behind the subgradesurface’. The subgrade temperature gradient decreased with depth increasing. Affected bytemperature and rainfall time, water content decreased with subgrade depth increasing inMay, but which was opposite in September, and water content in road shoulder is larger thanat the middle of subgrade’ within3m depth. Moisture migrated from high water potential tolow water potential in subgrade, moisture migrated from high temperature to low temperature,which make the moisture migrated to0℃line gathered near the permafrost.3）Numerical model of permafrost subgrade longitudinal cracks was builded base on thephase transition temperature field control equation, moisture migration control equation ofconsidering temperature gradient and the phase transition influence, stress and deformationcontrol equation. This paper analyzed the effect of roadside water, the height of subgrade,permafrost, slope direction and time of roadside water on permafrost subgrade longitudinalcracks with finite difference method.4）Longitudinal cracks were classified and graded by distribution characteristics offormation, deformation characteristics and developmental severity. This paper put forward thetreatment technology, which are longitudinal cracks from a mechanical point of view, flexiblebeam technology, tenon geomembrane bag technology, the tenon geomembrane bag andflexible beam comprehensive technology. Preventive measures of Qinghai-Tibet highway subgrade longitudinal cracks and general design method of drainage facilities were putforward from preventing water and reducing heat enter the subgrade. |
PDF Full Text Request