高速列车振动荷载下水泥改良黄土动力学试验

Dynamic Tests on the Cement-improved Loess under the Vibratory Load

摘要:

结合大同—西安高速铁路建设,选取该线路数个不同地貌单元的典型黄土路段采集试验样品,在GDS高级动态三轴测试系统上进行了水泥改良黄土的动力特性室内试验研究。采用正交试验法以优化试验方案。动荷载按照不同黄土层的埋深深度以火车振动衰减规律求取,土样按照不同水泥掺量经击实获得,经过长时间、多振次的动力学试验后获得水泥改良黄土的动弹模、动阻尼以及振陷量;进而探讨土层埋深、水泥掺和比、压实系数、浸水条件和振动次数对土样动力特性参数影响的主次顺序及显著性程度,找出工程最优化方案。结果表明:影响水泥改良黄土振陷量的各因素的主次顺序为:水泥比>浸水条件>振动次数>深度>压实系数,水泥比和浸水条件影响显著,其它因素无显著影响;动弹性模量影响因素主次顺序：深度〉浸水条件〉水泥比〉振动次数〉压实系数,深度和浸水条件影响高度显著;阻尼比影响因素主次顺序：浸水条件〉水泥比〉振动次数〉压实系数〉深度,水泥比和浸水条件影响高度显著。随着水泥比的增加水泥改良黄土动力特性越好,不存在最优水泥配合比。

Abstract:

In this paper dynamic triaxial tests were performed to explore the order and contribution rate of experiment factors such as depth,cement commingle ratio,compacting factor,water-dipping conditions,and vibration frequency on the dynamic characteristics of cement-improved loess including dynamic deformation,dynamic elastic modulus,and damping ratio.On the basis of the foundation construction of the Datong-Xi＇an high-speed railway,a large number of test samples have been obtained that include typical loess profiles of various geomorphic units.The dynamic parameters of cement-improved loess were tested on the GDS advanced dynamic triaxial test system at the State Key Laboratory of Continental Dynamics.The orthogonal test method was applied to optimize testing.The dynamic load was calculated according to the train vibration attenuation rule of various depths.Loess samples of various cement ratios were created through compaction tests.The dynamic characteristics of cement-improved loess such as dynamic deformation,dynamic elastic modulus,and damping ratio were determined from dynamic tests that included lengthy periods and a large number of cycles.The results showed that within the test factor level range,the primary and secondary order of factors that affected the vibrated subsidence were cement ratio water-dipping conditions vibration frequency depth compacting factor.In addition,cement ratio and water-dipping conditions showed significant influence on dynamic deformation.The primary and secondary order of factors that affected the dynamic elastic modulus were depth water-dipping conditions cement ratio vibration frequency compacting factor.In addition,depth and submerged conditions showed significant influence.The primary and secondary order of factors that affected the damping ratio were submerged condition situation cement ratio vibration frequency compacting factor depth.In addition,cement ratio and submerged conditions showed highly significant influence.Therefore,an increase in cement ratio results in a significant improvement in the dynamic characteristics of cement-improved loess;no optimal ratio of cement was noted.