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By far, the most technologically challenging railway ever built was probably the Qinghai-Tibet Railway, 【小题1】 (complete) in 2006, which connects Xining to Lhasa. The railway was first planned in the 1950s, but the technical difficulties were too much 【小题2】 (overcome). It was not until 1984 【小题3】 the first 814-kilometer section of the railway, from Xining to Golmud, was completed.
The biggest issue was the permafrost(冻结带)-frozen earth. In the summer, usually melting at a fast speed, the top layer of the permafrost turns to mud, 【小题4】 (make) the ground unstable. A 【小题5】 (various) of solutions were used to get around this. In some cases, railway bridges 【小题6】 (build). In other cases, engineers installed pipes under the ground to keep it frozen during the summer. Finally, in some areas it was impossible to build the railway over the permafrost, 【小题7】 engineers tunneled through it.
It is hoped that the experience of building the Qinghai-Tibet Railway can be used in 【小题8】 new project, linking China with Pakistan. This railway 【小题9】 (travel) 1,000 kilometers through the Pamir Mountains, which are nicknamed the Roof of the World. Building such a railway will be 【小题10】 (doubt) a technical challenge. It has not yet been announced when construction on this project will start.