高裂度地震区铁路液化地基处理措施的试验研究

摘要

Research purposes: The Yuxi -Mengzi railway is through the tonghai lacustrine deposites basin. The main geological features are silty sand and silty clay. It is a typical seismic liquefaction foundation. Therefore, gravel-pile consolidation measures are applicated to reinforce the foundation. To demonstrate the feasibility of the compaction and drainage reinforcement, the dynamic tri-axial experimental study of liquefaction strength based on different sand density and drainage condition was performed. The pore water pressure of liquefaction foundation is effected by seismic intensity, which is simulated by shaking-terrace test. The liquefaction resistance of foundation was estimated by the change of pore pressure ratio.rnResearch conclusions: ( 1 ) By dynamic Tri-axial test and shaking-terrace test, the gravel-pile consolidation measures are effective reinforcement for the liquefaction foundation of tonghai basins. (2) The liquefaction resistance of silty sand and silty clay foundation has a significantly increase by the compaction and drainage effection of gravel-pile. (3) Under the seismic loading condition, the main liquefaction foundation area is out of embankment slope. The foundation of embankment has not liquefied, pore pressure ratio of which is much less than 0. 8. (4) For the foundation rnout of embankment slope, pore pressure ratio has increased rapidly when the liquefaction occurred. ( 5 ) For the liquefaction foundation, the reinforcement area is still need to be studied. (6 ) The liquefaction resistance of other reinforcement measures (Such as; cement-soil mixing piles, CFG piles, etc. ) are needed to be further studied. (7) Shaking-isolated measures at toe of slope are recommended, and should be conducted a thorough study.%研究目的:玉蒙铁路通过通海湖相沉积盆地,以粉细砂和粉质黏土为主,属典型的地震液化地基.针对设计采用的碎石桩加固处理措施,通过动三轴试验研究粉细砂两种密实度和排水条件的液化强度,验证采用挤密排水法处理加固的可行性；采用振动台试验模拟地基液化的孔隙水压力随地震裂度的变化情况,从孔压比的变化验证地基抗液化能力.研究结论:(1)通过动三轴试验和振动台试验,验证了碎石桩复合地基对通海盆地的粉细砂液化地基加固的可行性；(2)碎石桩的挤密和排水作用对提高粉细砂液化地基抗液化强度效果明显；(3)地震荷载作用时,通海盆地粉细砂液化地基的液化范围主要是路堤坡脚以外的范围,而路堤内的地基的孔压比则远远低于0.8(通常认为液化的孔压比),没有液化；(4)通海盆地粉细砂液化地基发生液化时,坡脚外地基的孔压比随加载时间迅速增加；(5)对于液化地基上的路堤,复合地基的加固范围仍是一个需要研究的课题；(6)液化地基其它加固措施(如:水泥土搅拌桩、CFG桩等)的抗液化效果尚待进一步研究；(7)建议在坡脚外采用隔震措施,再进行深入研究.