振幅影响隧道混凝土累积损伤特征的试验研究

Experimental study on dynamic amplitudes for cumulate damage characteristics of tunnel invert concrete

重载列车轴重的增加导致振动幅值的提高,进而引起隧底结构损伤破坏的发生。针对仰拱混凝土累积损伤方面研究的不足且未引入隧道设计规范中,基于Helmholtz自由能理论体系,开展用于描述循环荷载引起仰拱混凝土累积损伤特征计算模型的研究。为了验证累积损伤模型并获取满足隧底力学环境的混凝土损伤计算方法,进行静载与循环荷载耦合环境中不同振动幅值作用下仰拱混凝土的试验研究。实验数据及数值计算结果表明:混凝土损伤演化曲线可以分为3个阶段:初期增长阶段、稳定增长阶段和快速发展阶段。通过对不同阶段混凝土损伤演化趋势的非线性拟合分析,给出能够引发混凝土损伤破坏的静载水平和不同阶段损伤演化趋势的定量表达式。通过数值计算与试验结果对比分析,得到混凝土试件损伤主要分布在中间受拉区域,底部损伤值相对较大并最终发生破坏。初始阶段损伤首先发生在混凝土试块中底部,混凝土损伤由试件下部逐渐向上逐渐发展。

The growth of train axle load has led to an increase in dynamic loading enhancing their cumulate damage impact in the base structure of tunnel.However,the relevant theories research on dynamic performance and accumulate damage behavior are still limited and not included in current design codes.Based on the framework of Helmholtz free energy theory,this work presents a accumulate damage mode for describing the damage behavior of invert concrete due to cyclic load in tunnel environments.In order to verify the damage model and get the damage calculating method,a number of invert concrete tests under different vibration amplitudes combined were presented.The test data and numerical computing results show that the damage process is divided into three stages,initial growth stage I,slow growth stage II,and rapid growth stage III.This thesis analyzed the different stages in the damage process by fitting the nonlinear damage equation.Moreover,the critical static load level causing the failure of the specimen and the quantitative expression of the damage process is obtained.Through comparisons of the calculation results and the test results,damage are mainly distributed in the middle area,and the major maxes of damage appears around the bottom of specimen,eventually leading to destroy concrete.The evolution of initial damages appeared first at the bottom centre of specimen and new damages is forming upward progressively.