季节冻土区长期交通荷载下公路路基永久变形特性

摘要

为研究季冻区公路路基在长期交通荷载作用下永久变形的累积规律,首先基于室内试验获取的路基融土永久应变经验公式,提出季节冻土区路基永久变形计算步骤;并通过建立的基层-路基-地基有限元模型,研究汽车轴型、后轴轴重、行车速度和路基融化厚度对正常期和春融期路基应力比和永久变形的影响.计算结果表明:正常期路基的应力比随着埋深的增加逐渐减小,融化路基应力比较正常期大,冻结路基内较正常期小;六轴汽车产生的永久变形大于其他4种轴型汽车;路基内的应力比和永久变形随后轴轴重和路基冻融影响厚度的增加而显著增大;行车速度越低,路基内应力比和永久变形越大.据此提出了季节冻土区长期公路交通荷载作用下路基永久变形预测公式.%To determine permanent deformation and its accumulation characteristics of subgrade induced by longterm traffic loading in seasonally frozen regions,a calculation method is proposed based on the accumulative strain empirical of subgrade soil under cyclic loading.Then,a finite element model of base-subgrade-foundation was built,and the effects of truck type,rear-axial loading,running speed and the depth of subgrade on the stress ratio and permanent deformation in the normal and spring-thawed period are analyzed.The calculated results show that:the stress ratio decreases with the increasing of depth in the normal period,and the stress ratio in thawed soil is greater than frozen soil and normal soil.Six-axis truck could produce more permanent deformation than other four types truck.The stress ratio and permanent deformation increases with the increasing of the rear-axis loading and the thickness affected by freeze-thaw action.Stress ratio and permanent deformation decreases with the increasing of running speed.Furthermore,a prediction formulation of subgrade permanent deformation is proposed based on the above calculation results.