中文摘要：

以青藏铁路现场实体工程为背景，选用块石路堤、块石护坡和通风管路堤主动冷却措施进行现场实体工群试验，通过对路基内温度场的监测，研究这些措施对保护冻土的作用及效果。分析结果表明，2个冻融周期后，块石护坡路基、通风管路基和块石路基均具有一定的调节降温作用，有利于下覆多年冻土的保护。但是冻土上限的抬升需要消耗下部土体的冷能来实现，说明冻上路基温度场还处于不稳定阶段。

英文摘要：

Qinghai--Tibet railway crosses 550 km continuous permafrost regions and 82 km discontinuous permafrost regions, where high temperature regions（annual average ground temperature is above -1.0 °C） occupy 275 km, ice-rich regions cover 221 km, overlapped sections of high temperature and ice-rich occupy about 134 km. As a result of the influences of both global climate warming and railway engineering on the permafrost degradation, design and construction of roadbed in permafrost regions are faced with quite great difficulties. As the natural thermal state and underground ice are the important factors influencing the roadbed stability, the choice of roadbed structure to protect permafrost is the leading principle of engineering design. Therefore, many measures are put forward and adopted including crushed rock slope protection, crushed rock embankment, embankmentof heat pipe, embankment of awning, thermal-insulation treatment embankment, widened and heightened embankment and duct-ventilated embankment, etc. The crushed rock slope protection, crushed rock embankment, embankment of heat pipe, embankment of awning, and duct-ventilated embankment are all actively protective technologies. The embankment of crushed rock slope protection, crushed rock embankment and duct-ventilated embankment are chosen to study the protective effects of the three kinds of embankments on the permafrost based on the in-situ monitoring results of the roadbeds in Qinghai--Tibet railway. The basic data of actively adjusting and cooling roadbed measures in permafrost regions have been obtained and analyzed. Results show that all of thethree measures have certain effects on adjusting and cooling roadbed, and are advantageous to protect permafrost under the roadbed. However, the rising of artificial permafrost table needs to consume the cold energy of soil below ground, which indicates that the temperature fields of permafrost foundation are in instable phase.