切缝法测定水泥混凝土路面残余应力数值模拟分析

Numerical analysis of notch-cutting method for determining the residual stress in PCC Slab

残余应力和固化翘曲的存在使得水泥混凝土路面(机场道面)的开裂模式向多样化发展,对路面长期服役行为产生深远影响。利用切缝过程中板表面应变释放历史确定板内初始应力和残余应力的方法尚处于初步阶段。通过建立三维有限元模型,对切缝过程中板的响应进行数值模拟,系统分析不同测点位置、边界约束方式、地基刚度、板厚、切缝间距、切缝深度、温度场构成方式等工况组合下的混凝土板上表面的应力、应变释放规律。在此基础上提出基于干切缝法的水泥混凝土板全深度绝对应力和残余应力分布预估方法,以深距比综合考虑切缝间距、切缝深度对应力、应变释放规律的影响,以应变释放极限值考虑板的大小、厚度、温度场构成方式、下卧层刚度等因素对应变释放过程的影响,给出表征混凝土板表面应变释放规律的基函数及其参数取值。最后,通过足尺大板数值算例验证该方法的可靠性,建议试验过程中将切缝深距比终值定在1.0~1.5范围内,同时尽量不要选择切缝厚距比小于1.25的切缝方案。

The existence of residual stress and built-in curling will result in the multi-cracking modes in portland cement concrete( PCC) slab and produce profound influences on the long term service behavior of JPCP. It is still in the preliminary step to determine the initial stress and residual stress inside the slab by measuring the surface strain release history during cutting notch. Three dimensional finite element models were established to simulate the slab's responses to notch cutting under different conditions such as measurement position,boundary constraint modes,foundation stiffness,slab thickness,notch space,notch depth and temperature field components,etc. On the basis of these data,a full depth absolute stress and residual stress profile prediction procedure using dry notch cutting method is presented.Notch depth-space ratio is taken to consider the overall effects of notch space and notch depth on stress and strain relaxation curve. Ultimate relieved strain is introduced to characterize the influences of slab size,thickness,temperature field components and the underlying stratum. The basis functions and corresponding parameter values that represent the slab surface strain relief features are listed. The reliability of this procedure is verified by a numerical example of a full scale slab. The eventual notch depth-space ratio is recommended to be in between 1. 0 and 1. 5 and slab thickness-notch space ratio is advised to be larger than 1. 25 in experiments.