填土容重对中低速磁浮基床厚度影响分析

Analysis of the Influence of Filling Bulk Density on the Subgrade Bed Thickness of Medium and Low Speed Maglev

中低速磁浮低置结构路基厚度的确定原则与铁路路基相同,均按列车产生的动应力与路基自重应力之比为0.2的原则确定。由于中低速磁浮列车动荷载较小,填土容重有可能成为确定基床厚度的敏感性指标,规范对不同填料的基床厚度均采用1.8 m设计,其合理性有待商榷。本文对填土容重对路基动荷载深度的影响进行分析,据此对中低速磁浮低置结构路基基床厚度进行设计,提出基床厚度设计公式,并给出了设计案例。研究结论:(1)填土容重对动荷载深度的影响有限,浮动值约为10%,但据此对基床厚度仍有一定的优化空间。(2)根据不同填料压实后的容重经验值计算,基床底层填料采用细粒土时,基床厚度可减至1.7 m;采用粗粒土时,基床厚度可减至1.65 m;采用碎石土时,基床厚度可减至1.6 m。(3)动荷载影响深度与填土容重之间约为线性比例关系,基床厚度可根据公式快速设计,以达到优化基床厚度的目的。

The principle to determine the subgrade thickness of ground structure of medium and low speed maglev is the same as that of railway subgrade.The determination principle is that the ratio of dynamic stress generated by train to self weight stress of subgrade is 0.2.Due to the small dynamic load of medium and low speed maglev train,the bulk density of fill may become a sensitive index to determine the thickness of subgrade bed.In the code,the thickness of subgrade bed with different fillers is designed as 1.8 m,which is not reasonable.Therefore,this paper analyzes the influence of filling bulk density on subgrade dynamic load depth.Based on this,the thickness of subgrade bed with ground structure is designed.The design formula of subgrade bed thickness is put forward and a design case is given.The conclusions of this paper are as follows:firstly,the influence of soil bulk density on dynamic load depth is limited,and the amplitude value is about 10%,but there is still some room for optimization of subgrade bed thickness.Secondly,according to the empirical value of bulk density after compaction of different fillers,the thickness of subgrade bed can be reduced to 1.7 m when the bottom layer of subgrade bed is filled with fine-grained soil,and 1.65 m when coarse-grained soil is used,and 1.6 m when gravel soil is used.Thirdly,the relationship between the depth of dynamic load and the bulk density of fill is approximately linear,and the thickness of subgrade bed can be quickly designed according to the formula.This can achieve the purpose of optimizing the subgrade bed thickness.