Study On Construction Risk Assessment And Control Measures Of Large Diameter Bored Pile In Deep Water

With the construction of large bridges extending to the ocean and deep-water areas,the deep-water pile foundation is also developing towards large diameter.However,the harsh deepwater environment,complex geological conditions,special equipment and special technology bring great challenges to the construction of deep-water large diameter pile foundation.Due to the frequent occurrence of construction risk accidents of large diameter bored piles in deep water and the serious consequences,it is imperative to establish the construction risk assessment and control system of large diameter bored piles in deep water from both theoretical and technical aspects through systematic research.Based on the pile foundation construction project of Xihoumen Road-Railway Bridge in Ningbo-Zhoushan Railway,the maximum construction water depth is 60 meters,and the design diameter of pile foundation is 6.3 meters,which are the highest in China.By means of investigation and analysis,numerical simulation,statistical inference and other research methods,this paper systematically studies the risk assessment and control of deep-water large-diameter bored pile construction.The main research contents and conclusions are as follows:(1)To carry out risk identification for construction of deep-water large-diameter bored piles.Through the investigation and analysis of the accident cases occurred in the relevant actual projects,the risk identification is carried out in combination with the actual characteristics of the relying projects,and the list of construction risk accidents of deep-water large-diameter bored piles is formed.By using the risk matrix method,not only the risk-bearing body and risk-bearing environment are clearly defined,but also the risk-causing source is more clearly distinguished.(2)To carry out construction risk analysis of large diameter bored piles in deep water.The construction risk accidents of large-diameter steel casing deformation and large-diameter underwater concrete pouring quality defects contain complex,hidden and difficult to quantify risk factors.Through the simulation analysis of construction penetration and pouring flow pattern,the quantitative impact of various risk factors on the accident is obtained,and the development law of the accident is more clearly understood.(3)To carry out construction risk estimation of large diameter bored piles in deep water.According to the results of construction risk accident identification,the risk evaluation index system of deep-water large-diameter bored pile construction is constructed,the reasonable evaluation expert group is set up and the applicable evaluation criteria are established.By using the scientific and quantitative combination weighting method of game theory and twodimensional cloud risk evaluation model,the comprehensive risk level of 6.3m large-diameter bored pile construction in the project is II.Major risk accidents and key risk factors after screening,and have a comprehensive grasp of the probability and severity of possible construction risk events.(4)To carry out construction risk control of deep-water large-diameter bored piles.According to the results of risk assessment and risk acceptance criteria,the risk control measures with technical pertinence are proposed for the major risk accidents and general risk accidents of deep-water large-diameter bored piles in the stages of steel casing construction,hole forming and pile forming,respectively,to reduce the possibility of risk accidents and the consequences of losses,which provides a reference and guidance for the construction of related projects in the future.