红黏土临界动应力与高铁无碴轨道路堑基床换填厚度

Critical dynamic stress of red clay and replacement thickness of ballastless track cutting bed of high-speed railways

针对武广高速铁路无碴轨道红黏土路堑基床长期动力稳定与换填厚度问题,利用改造后的应力控制式动三轴仪,研究了循环荷载作用下原状结构红黏土动应变随振次的变化规律,获得了11种试验条下原状结构红黏土临界动应力。按曲线走势特征,红黏土εd?lg N曲线可分为衰减型、临界型、破坏型3类,具有与其它黏性土相同的曲线型式。基于室内动力试验及现场动响应测试成果,采用临界动应力法初步评价了武广高速铁路无碴轨道红黏土路堑基床的长期动力稳定性,给出了相应的基床换填厚度最小值。探讨了含水比、围压、固结比对红黏土临界动应力及路堑基床换填厚度的影响,通过多元线性回归得到了两个简单实用的经验估算公式。红黏土临界动应力随含水比的增大线性减小,随围压、固结比的增大线性增大。基床换填厚度随含水比的增大线性增大,随围压的增大线性减小,固结比对基床换填厚度的影响就本次试验成果而言还不明显。研究成果为我国高速铁路无碴轨道路堑基床长期动力稳定性评价及换填厚度的确定提出了新的思路和方法,也为红黏土动力特性的深入研究积累了宝贵的第一手资料。

In view of the long-term dynamic stability and replacement thickness of red clay cutting bed under ballastless track of Wuhan-Guangzhou high-speed railway,the variation rules of dynamic strain of red clay in original structure under cyclic loading with vibration times are studied by means of the modified stress-controlled dynamic triaxial test instrument,and values of the critical dynamic stress of red clay in original structure are obtained under 11 kinds of test conditions.According to the trend features of curves,the curves can be divided into three types： attenuated,critical and destructive ones,and they are the same as those of other cohesive soils.Based on the results of laboratory and field tests,the long-term dynamic stability of red clay cutting bed under ballastless track of Wuhan-Guangzhou high-speed railway is preliminarily evaluated by use of the critical dynamic stress method,and the corresponding minimum replacement thickness is given.Influences of water content ratio,confining pressure and consolidation ratio on the critical dynamic stress of red clay and the replacement thickness of cutting bed are discussed.Two practical empirical formulas are obtained by means of multiple linear regressions.The critical dynamic stress decreases linearly with the increase of water content ratio,and increases linearly with the increase of confining pressure and consolidation ratio.The replacement thickness increases linearly with the increase of water content ratio and decreases linearly with the increase of confining pressure,and the influences of consolidation ratio are not obvious on it.A new idea is put forward for the long-term dynamic stability evaluation and the determination of cutting bed replacement thickness under ballastless track of high-speed railways,and the first-hand valuable data are accumulated for further studies on dynamic characteristics of red clay.