求翻译：青藏铁路建设改变以往一直沿用的消极被动保护冻土的措施，变“被动保温”为“主动降温”，采用积极主动的保护冻土措施，研究开发新的地温调控原理和技术，提出能冷却地基的新的路基结构形式和设计参数，以确保工程稳定是什么意思？

The change has been in use in the past passive measures to protect the permafrost of Qinghai-Tibet Railway construction, change the "passive holding" as "active cooling", the use of active measures to protect the permafrost, research and development of new geothermal regulatory principles and techni

Construction of the Qinghai-Tibet Railway has been changed from the previous practice of passive protection measures, and the permafrost soil is "passive" to "keep cool" initiative, a positive and proactive measures to protect permafrost research and development of the new geothermal heating theory

The Qinghai and Xizang railroad construction change formerly continuously continued to use the negative passive protection frozen earth measure, changed “the passive heat preservation” was “the initiative temperature decrease”, used the positive initiative protection frozen earth measure, the resear

Changed the construction of Qinghai-Tibet Railway has been used in the past for passive measures protecting frozen soil, change "passive insulation" as "active cooling" adopt positive measures of protection in permafrost regions, research and development of new principles and technology of temperatu

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