基于Monte Carlo方法的路堤震害风险概率评价

Risk probability assessment of seismic damage for embankment based on Monte Carlo method

以连云港-霍尔果斯高速公路K1125+470处路堤为研究对象,在路堤震害损伤判别、路堤结构形式和地震动输入确定的基础上,采用增量动力分析和概率性地震需求分析相结合的方法绘制了路堤震害易损性曲线,评价了路堤震害易损性;将路堤震害风险概率定义为场地地震危险性与路堤震害易损性的卷积,并提出相关计算方法;研究了场地地震烈度概率分布模型和地震烈度与地震动峰值加速度转换关系,提出了未来50年内地震动峰值加速度的概率分布函数;基于Monte Carlo方法进行了无挡土墙和有挡土墙路堤的震害风险概率评价,验证了挡土墙对提高路堤抗震性能的积极作用。研究结果表明:当地震动峰值加速度达到0.6g时,无挡土墙路堤超越严重损伤的概率为65.910%,达到0.8g时,超越严重损伤的概率为99.995%,说明无挡土墙路堤的震害易损性较高;未来50年内无挡土墙路堤发生严重损伤和毁坏的风险概率为29.07%,发生基本完好和轻微损伤的风险概率为31.97%;未来50年内有挡土墙路堤超越严重损伤的风险概率比无挡土墙路堤低7.9%,发生基本完好和轻微损伤的风险概率比无挡土墙路堤高12.14%,说明挡土墙可以显著降低路堤震害风险;以路堤未来50年发生毁坏的风险概率40%为风险可接受度对路堤进行抗震设计和加固。

The embankment of Lianyungang-Horgos Expressway at K1125＋470 was taken as research object,the seismic damage,embankment structure form and ground motion input were determined,the seismic vulnerability curves were drawn by combining incremental dynamic analysis and probabilistic seismic demand analysis,and the seismic vulnerability of embankment was evaluated.Embankment＇s seismic risk probability was defined as the convolution of seismic hazard and embankment seismic vulnerability,and its calculation method was put forward.The probability distribution model of seismic intensity and the relationship between seismic intensity and PGA were studied,and the probability distribution function of PGA was propssed in the next50 years.The risk probabilities of embankment seismic were evaluated by using the Monte Carlo method for embankments with and without retaining wall,and the positive effect of retaining wall on improving embankment＇s seismic performance was verified.Analysis result shows that when PGA is 0.6g,the probability exceeding severe damage of embankment without retaining wall is65.910%;When PGA is 0.8g,the probability is 99.995%,so the seismic vulnerability of embankment without retaining wall is high.The risk probability of exceeding severe damage for embankment without retaining wall is 29.07% and the risk probability of main integrity and minor damage is 31.97% in the next 50 years.In the next 50 years,the risk probability exceeding severe damage for embankment with retaining wall is 7.9% lower than the value without retaining wall,and the risk probability of main integrity and minor damage is 12.14%higher than the value without retaining wall,which indicates that retaining wall can significantly reduce the seismic damage risk of embankment.The acceptable risk probability exceeding severe damage in the next 50 years is defined as 40%in order for new embankments＇ aseismic design and existing embankments＇ aseismic reinforcement.