青藏铁路沿线的地裂缝及工程影响

通过大比例尺野外地质调查和跨季节对比观测, 发现青藏铁路沿线发育地震破裂、断层裂缝、冻土裂缝与冰裂缝4种不同类型的地裂缝。典型地震破裂包括西大滩古地震破裂、昆仑山南缘地震破裂、可可西里古地震破裂、崩错地震破裂、谷露盆西地震破裂、羊八井—当雄盆西地震破裂; 地震破裂规模大, 产状稳定, 与地震鼓包、地震陡坎、地震凹陷有序组合, 是地表构造变形的重要形式, 属内动力成因地裂缝。断层裂缝沿断层破碎带定向分布, 产状稳定,成群产出, 与断层活动、地下水运移、不均匀冻胀存在密切的关系, 是构造变形与融冻变形联合、内外动力耦合产生的复合成因地裂缝。冻土裂缝和冰裂缝属外营力成因地裂缝, 是冻土与冰层不均匀融冻变形的重要表现形式。地震破裂、断层裂缝和冻土裂缝对青藏公路、青藏铁路及沿线工程安全具有不良影响, 这些地裂缝切割错断路基, 形成路面破裂和路基滑塌, 产生显著的灾害效应。

Surface Fractures and Their Hazard Effects on Engineering Construction along the Golmud- Lhasa Railway across the Tibetan Plateau

After field geological survey on the scale of 1∶2,000 and comparative measurement in different seasons, four types of surface fractures, seismic fractures, fault fracturs, permafrost fractures and ice fractures, were discovered along the Golmud Lhasa railway across the Tibetan Plateau after engineering geological mapping on the scale of 1∶2,000 Seismic fracture zones are consisted of and accompanied by seismic fractures, seismic scarps, pressure ridges, sag ponds and pull apart basins Typical examples include the Xidatan palaeo seismic fracture zone, seismic fracture zone of the Kunlun Ms 8 1 earthquake occurred in November 14,2001, the south Hohxil palaeo seismic fracture zone, seismic fracture zone of the Bengcuo Ms 8 0 earthquake occurred in 1951 and seismic fracture zones along normal fault in east of the Nyainqentanglha Mts caused by Jiuzila Ms 7 5 earthquake occurred in 1952 and Yangbajain Ms 8 0 earthquake occurred in 1411 Fault fracture zones often form in active fault zones and appear as long extension with stable trending, they are jointly controlled by active faulting, underground water concentration and freezing expansion Permafrost fracture and ice fracture are both the result of freezing expansion without evident relation to tectonic deformation and regional structures Seismic fracture, fault fracture and permafrost fracture all gave negative effects on engineering construction and formed geological hazards at many localities along the Golmud Lhasa highway and railway Ice fractures formed in freezing rivers and lakes and on the top of pingos have not shown any hazard effect on engineering constructions up to the present