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青藏铁路清水河多年冻土试验段,平均海拔4 470 m,冻土年平均地温为-1.40℃～-0.46℃,冻土上限为1.5～3.5 m,2001年9～11月施工。2002年10月前后,路基相继出现多条纵向裂缝。为研究试验段路基裂缝成因及片石路基沉降量较大等问题,2003年5月对DK1026+630和DK1025+583断面进行解剖分析,如实记录开挖路基基本情况,进行现场和室内试验,分析路基沉降和裂缝形成规律,计算路基沉降量。结果表明,路基沉降由在外荷载作用下路基本体的压密沉降和基底以下地层的压密和融化沉降两部分组成,由于两个路基断面填料压实度均匀良好,其沉降量主要来自于地层的压密变形和融沉,路基沉降量的计算值与实测值基本一致。DK1026+630断面裂缝贯穿路基本体,为融沉裂缝,是由于路基阳侧原天然地面下泥灰岩风化物融化压缩引起路基体横向不均匀沉降造成的。由于片石有调解人为上限形态和抑制路基不均匀变形的作用,故片石路基没有产生融沉裂缝,但在竣工初期却表现出较大的沉降量。
Qinghai-Tibet Railway Qingshuihe permafrost experimental section, with an average elevation of 4 470 m, the average annual ground temperature of frozen soil is -1.40 ℃ ~ -0.46 ℃, the upper limit of permafrost is 1.5 ~ 3.5 m, 2001 September to November construction. Around October 2002, a number of longitudinal cracks have appeared in the subgrade. In order to study the causes of subgrade cracks and the large amount of settlement of paving slabs in the pilot section, the sections of DK1026 + 630 and DK1025 + 583 were anatomically analyzed in May 2003, and the basic conditions of subgrade excavation were recorded. Field and laboratory tests were conducted to analyze subgrade Settlement and crack formation rules, calculate the subgrade settlement. The results show that subgrade settlement is composed of compact subgrade settlement under subgrade load and compaction and thaw settlement of sub-basement. Because of the well-compacted compaction of the two embankment sections, the subsidence mainly comes from the formation Compaction deformation and thaw settlement, the calculated value of roadbed settlement is basically consistent with the measured value. The fracture of DK1026 + 630 penetrates through the road base, which is caused by the thawing settlement of the subgrade due to the lateral subsidence of the subgrade caused by the melting and compressing of the marl weathering material under the natural ground of the subgrade. Because of the upper limit shape of the stone tablet and the effect of suppressing the uneven deformation of the roadbed, there is no thawing and thawing cracks in the stone tablet roadbed, but a large amount of settlement is shown at the early stage of completion.