筑坝堆石料邓肯-张模型参数确定方法的改进

An improved Method to Determine Duncan-Zhang Model Parameters of Rockfill Material

针对目前常用的邓肯-张模型参数整理方法计算的初始模量离散等问题,进行了4组堆石料大型三轴试验研究,建议了一种新的模型参数整理方法。试验结果表明:ε_a/q-ε_a(ε_a为轴向应变,q=σ_1-σ_3为偏应力)的试验点在低应力水平和高应力水平有明显偏离直线关系的趋势,导致目前常用的参数整理方法计算的初始模量离散性较大。考虑到坝体关注的主要应力水平在75%以下以及低应力水平受装样引起的超固结的影响,建议根据应力水平50%和75%两点求取初始模量和破坏比;破坏比R_f并非常数,R_f随围压σ_3的增大逐渐减小,且lg(R_f)与lg(σ_3/pa)呈良好的直线关系。反演结果表明,在邓肯-张模型中考虑围压水平对R_f的影响,能更好的反映较高围压范围条件下堆石料的应力应变特性,建议当进行超高土石坝静力分析时应考虑R_f的围压相关性。

Duncan- Zhang model has been widely used to analyze the static deformation of earth-rock dam.In accordance with the discrete problem of initial modulus,we propose a new method to determine the model parameters by conducting four groups of large-scale triaxial tests on rockfill material.The main conclusions show that the commonly used method of determining model parameters makes the discrete problem of initial modulus on account of the obvious deviation from the trend of linear relationship of some sites of ε_a/q-ε_a at low stress levels and high stress levels.Considering the main stress levels of the dam below 75 percent and the influence of the over-consolidated at low stress levels,we suggest using the sites of 50 percent of stress level and 75 percent of stress level to calculate initial modulus and break ratio.Tests show that break ratio R_fdecreases with increasing confining pressure σ_3,and lg（R_f） and lg（σ_3/pa） can be described with linear.The inversion results indicate that it can better reflect stressstrain characteristics of rockfill material under high confining pressure by considering effect of break ratio,so it is suggested that the effect of confining pressure on break ratio should be considered when the static analysis of super high earth-rock dam is carried out.