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The China Jinping Underground Laboratory () is a deep underground laboratory in Sichuan, China. The cosmic ray rate in the laboratory is under 0.2 muons/m²/day,〔 placing the lab at a depth of 6720 m.w.e.〔 and making it the best-shielded underground laboratory in the world.〔 The actual depth of the laboratory is , yet there is horizontal access so equipment may be brought in by truck. Although the marble through which the tunnels are dug is considered "hard rock", at the great depth it presents greater geotechnical engineering challenges〔〔〔 than the even harder igneous rocks in which other deep laboratories are constructed. The water pressure in the rock is also inconvenient. But marble has the advantage for radiation shielding of being low in radionuclides,〔〔 such as 40K, 226Ra, 232Th,〔 and 238U. The laboratory is in western China, near Tibet, about southeast of Chengdu.〔 The closest major airport is Xichang Qingshan Airport, away by road.〔 ==History== The Jinping-II Dam hydroelectric power project involved excavating a number of large tunnels under Jinping mountain: four large headrace tunnels carrying water southeast,〔 two vehicular access tunnels,〔 and one water drainage tunnel. Hearing of the excavation in August 2008,〔〔 physicists at Tsinghua University determined that it would be an excellent location for a deep underground laboratory,〔 and negotiated with the hydropower company to excavate laboratory space in the middle of the tunnels. A formal agreement was signed on 8 May 2009,〔 and excavation was promptly started.〔 The first phase CJPL-I, consisting of a main hall,〔 plus of access tunnel (4,000 m³ total excavation)〔 was excavated by May 2010,〔 and construction completed 12 June 2010.〔 A formal laboratory inauguration was held 12 December 2010.〔 The laboratory is to the southwest of the southwesternmost of the seven parallel tunnels, traffic tunnel A. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「China Jinping Underground Laboratory」の詳細全文を読む スポンサード リンク
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