HIMALAYAL - SHANGHAI - CHINA
A new round of annual inspection of eye-catching Qinghai-Tibet network project - Chaila DC have started since 6th May 2016 after five years of stable and safe operation. It was recently reported that tower foundations in Chaila DC line permafrost have gone through five complete freeze-thaw cycles, and frozen-soil foundations were in stable condition without foundation deformation exceeding a limit.
The part of Qinghai-Tibet network project - Chaila DC passing through the permafrost reaches 550 kilometers. There are 1207 tower foundations, which accounts for 51% of the sum. To reduce the disturbance to frozen soil as much as possible and protect vulnerable ecological environment of the plateau, all participants fully implement relevant standards and regulations about construction quality control, and take measures such as foundation treatment as well as hot sticks to minimize the impact of frost heave and thaw subsidence on the foundation stability.
From April 2012 to April 2015, researchers from Qinghai Electric Power Research Institute and Chinese Academy of Sciences have been monitoring the stability of Chaila DC power transmission line tower foundation. Three aspects were focused on, including the monitoring of No.131 tower foundation stability, No.20 tower soil freezing process and No.10 tower frozen foundation temperature. Plenty of materials about DC line tower foundation stability are accumulated.
The Qinghai Electric Maintenance Company measures foundation settlement and tower inclination three times in permafrost area from March to April, July to August and November to December each year. Combined with line inspection and annual maintenance condition, measurement data are compared with original data, which will provide important support for safe and long-term operation of Qinghai-Tibet DC.
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