Research On Monitoring Items Selecting For Deep Foundation Pit Construction Of Metro Based On Risk Assessment

In recent years, urban's metro development is in large scare while safety accident rate is on the rise in China during construction stage. Useful information can be provided by monitoring. It is very important to identify risk position accuratly and select monitoring items properly for prevention. However, due to the regulation related to monitoring items selecting lacking of focalization, the actual construction risk is not considered in our country. In order to supplement the lack of specification, making a systematic research on monitoring items selecting based on the risk assessment of the basic engineering information during the deep foundation pit construction phase of metro is needed.First of all, on the detailed analysis of the research of deep foundation pit monitoring, risk assessment and related laws and regulations of metro, it is found that the study on monitoring items selecting is vitally important. Secondly, it puts forward the concept of "revealling the risk contribution rate" for describing the nature of monitoring items innovatively. After three methods( i.e. the investigation of experts investigation, the comparison of monitoring codes and monitoring cases) were applied to calculate quantitatively the priority of monitoring items, the final quantitative value and standard of monitoring items priority is concluded. Meanwhile, based on the quantitative identification of engineering risk characteristic parameters, building the risk rating standard system based on the basic engineering information can achieve to identify the risk level of overall and risk position for deep foundation pit of metro. Again, through the analysis of the monitoring items origin and the outcomes of revealling the risk contribution rate, the priority system between risk position and monitoring items is established. The final monitoring items priority partition adjustmentent were based on the risk level of overall and risk position. Finally, an actual case of a deep foundation pit of metro monitoring is to verify this method for monitoring items selecting by comparing the result from this method, specification and the actual project.The method of monitoring items selecting for deep foundation pit of metro is introduced, which is suitable for the stage of decision-making before excavation. However, taking into account different decision-makers for risk acceptance and on the adjustment for dynamic monitoring should be discussed and evaluated during the whole construction stage for monitoring items selection in the future.