地铁车站基坑工程工期风险值计算

Calculation of Construction Period Value-at-Risk of Foundation Pit Engineering for Subway Station

基于全概率、蒙特卡洛思想,构建阶段工期变化风险值的计算方法与步骤.从工期未发生异常变化、工期发生异常变化但未采取补救措施,以及工期发生异常变化且采取补救措施3方面进行阶段工期变化风险的概率计算,建立了工期异常时间全概率法的计算公式;运用蒙特卡洛思想,构建了基于Matlab的阶段工期变化风险蒙特卡洛法的计算步骤,并将贝塔分布函数用于描述工期变化.最后以某车站基坑工程为例,计算获得了该基坑开挖与支护工期变化风险值,验证了全概率法和蒙特卡洛法的实用性.

This paper deals with the calculation methods and the corresponding steps of the value-at-risk due to the construction period change,based on the total probability and the Monte Carlo thoughts.In the investigation,first,the risk probability is calculated for the project without anomalous change during the construction,with anomalous change but without remedial measures,and with anomalous change as well as remedial measures.Based on the probability calculation in the three above-mentioned cases,a calculation formula of full-probability method of abnormal project time is established.Then,by using the Monte Carlo thoughts,the Monte Carlo method calculation steps of the value-at-risk are presented based on Matlab,and the construction period change is described with the Beta distribution function.Finally,with an excavation engineering of a subway station as an example,the value-at-risk during the excavation period and the supporting period is calculated.The results indicate that the full-probability method and the Monte Carlo method are both effective.