Classification of Frost Damage Grades in Tunnel

In order to supply basic principles for preventing frost damage in tunnels,through analyzing the conditions of frost damage occurred in tunnels,climate and groundwater were chosen as main influencing factors to grading.On the basis of partition for climate cold level and groundwater harm degree,the classification of frost damage in tunnels is partitioned with a comprehensive evaluation method.The results show that the climate and groundwater are main influencing factors of frost damage;The cold level is partitioned into five grades by the control indicators of climate including the average temperature of the coldest month and the freezing depth;The harm degree of groundwater is partitioned into five grades by the control indicators of groundwater including the form of groundwater occurrence,supplying and the situation of groundwater spreading into tunnel.The classiffication of frost damage in tunnels is divided into five grades according to the influencing factors of climate and groundwater for frost damage levele;In permafrost,although the climate is cold in extreme,frost damage happens less seriously in the tunnels where surrounding rocks are freezing all the year round.The frost damage of permafrost tunnels is classified as grade Ⅱ while the ice on the surrounding rocks melts by the impacting of human activities in excavation or warming.