交通荷载作用下结构性软土地基长期沉降计算  

Long-term settlement calculation of structured soft clay foundation under traffic loading

作　　者：刘维正[1] 石志国 章定文[2] 瞿帅 Liu Weizheng;Shi Zhiguo;Zhang Dingwen;Qu Shuai(School of Civil Engineering,Central South University,Changsha 410075,China;School of Transportation,Southeast University,Nanjing 210096,China)

机构地区：[1]中南大学土木工程学院,长沙410075 [2]东南大学交通学院,南京210096

出　　处：《东南大学学报（自然科学版）》2018年第4期726-735,共10页Journal of Southeast University：Natural Science Edition

基　　金：国家自然科学基金资助项目(51208517);中国博士后科学基金资助项目(2013M530360)

摘　　要：为了合理预测结构性软土路基长期运营沉降,基于力学-经验法开展了交通移动荷载下软土地基动力附加沉降的计算分析.首先,通过对天然软土循环三轴试验结果的模拟与分析,验证了根据人工结构性土建立的稳定型和破坏型累积应变预测模型的有效性,建立了临界动应力比与应力灵敏度的定量关系,提出了适用于结构性土累积应变的预测模型.然后,采用数值方法确定了考虑荷载速率效应的动应力空间分布,结合累积应变经验模型与分层总和法,提出了交通荷载下结构性软土地基长期沉降的实用计算方法,并通过典型低路堤断面运营沉降的模拟计算,验证了所提方法的合理性与有效性.最后,开展了长期沉降的参数敏感性分析,结果表明:行车速度大于80 km/h和路堤高度小于2 m时,地基动应力显著增大,土结构性易受到损伤破坏;土体灵敏度越低,变形状态越易从稳定型转变为破坏型,地基浅层塑性变形显著增大.To reasonably predict the long-term operation settlement of structured soft soil subgrade,the dynamic additional settlement of soft clay foundation under moving traffic loading is calculated and analyzed based on the mechanical-empirical method.First,through analyzing and simulating the existing repeated load triaxial test results of natural soft clays,the validity of both stable and destructive models for predicting accumulative plastic strain obtained from test results of artificially structured soil is verified,and the quantitative relationship between critical cyclic stress ratio and stress sensitivity is established,and the prediction model of accumulative deformation is extended for structured soft soil under long-term cyclic loading.Then,considering the rate effect of traffic loading,the finite element numerical method was applied to determine the distribution of dynamic stress.Combining the empirical model of accumulative strain and the layer-wise summation method,a practical method is proposed for calculating the long-term settlement of structured soft soil foundation under traffic loading.The rationality and validity of the proposed method were verified through the measured post-construction settlement of a typical low embankment.Finally,parametric studies were conducted to analyze the effects of traffic loading and soil structure on the long-term settlement.The calculated results indicate that the dynamic stress in soft ground increases significantly when the running speed is more than 80 km/h and the embankment height is less than 2.0 m,which leads to vulnerable damage of the soil structure.And with the decrease of soil stress sensitivity,the plastic strain of the shallow-layer soil increases apparently as the accumulative deformation state transforms from stable to destructive type.

关 键 词：交通荷载 土结构性 长期沉降 计算方法 软土路基 

分 类 号：U432[交通运输工程—道路与铁道工程]