青藏铁路冻土路基路堤、路堑过渡带试验研究

Experimental Study on Transitional Zone between Embankment and Cut over Permafrost along Qinghai—Tibet Railway

根据青藏铁路北麓河试验段路堤、路堑过渡带近5年来的地温和变形监测资料,分析挖方段、零填段及填方段的冻土上限变化和路基变形特性。研究结果表明:挖方段,2002和2004年的多年冻土人为上限均为1.6 m,相对原天然上限下降量为0.5 m,但在2005年冻土上限有所回升,其变形主要表现为路基换填土层的固结变形;零填段,冻土上限上升量较大,2005年上升量达2.5 m,其变形主要来自活动层的压密变形;填方段,冻土上限有所上升,2005年上升量为0.7 m,其变形主要为天然上限以下冻土层的压缩及蠕变变形;到2005年12月,此过渡带路基均没有发生融沉变形,路基热稳定性好;从总沉降变形量来看,路堤断面变形量最大,零填断面变形量次之,路堑断面变形量最小,2004年11月后,总变形已基本趋于稳定。路基纵向变形比率最大为1.3∶1 000,小于线路设计坡度的3∶1 000,路基纵向沉降变形比较均匀,路面平顺性较好,能满足列车安全行驶的要求。

Based on the field observational data of ground temperature and subgrade deformation in the transitional zone between embankment and cut at Beiluhe test section along the Qinghai--Tibet railway, this paper discusses the features of artificial permafrost table and subgrade deformation during the first five years of the construction. Analyses of the monitoring results show that in the cut section, the artificial permafrost table was 1.6m Compared with the natural permafrost table, it descended 0. 5 m in 2002 and 2004, while it rose in 2005. The deformation was mainly caused by the consolidation of the soil-replacing layer. In the cut-to-fill location, the artificial permafrost table rose greatly because of the insulation and high-embankment, it increased 2.5 m in 2005. Most of the deformation was from the consolidation of the original active layer. In the fill section, the artificial permafrost table rose slightly, and the value was 0.7 m until 2005. The deformation was mostly resulted from the compression and the creep of ice-rich frozen soils under the original permafrost layer. Up to December 2005, there was no thawing deformation, and the thermal stabilization of subgrade was fine. In terms of the general settlement and deformation, the deformation in the fill section is the greatest, cut-to-fill section takes the second place, and cut section is the smallest. The total settlement of subgrade tended to stabilize after November 2004. The greatest longitudinal deformation ratio was 1.3： 1 000, which was smaller than the design standard of 3 ： 1 000. The longitudinal settlement of the road surface was uniform, and it was satisfactory to the railway line.