Construction Analysis And Process Monitoring Of Double Wall Steel Cofferdam For Deep Water Foundation

Double wall steel cofferdam is a temporary water retaining member commonly used in the construction of pier deep water foundation.In the past bridge construction,the construction of steel cofferdam is often neglected.The design of large steel cofferdam is complicated and the risk of construction is high.An example of damage to steel cofferdam due to improper construction control has occurred.Therefore,the implementation of stress monitoring is the key to ensure the smooth construction of steel cofferdam.In the past cofferdam monitoring,no perfect stress monitoring system has been formed.Based on the double wall steel cofferdam of the Third Yangtze River Bridge in Wanzhou,this paper analyzes the construction process of the steel cofferdam installed at the high water level.The finite element software is used to calculate the mechanical response of the steel cofferdam under the most unfavorable conditions,and the stress monitoring of the key construction stage is analyzed.In order to grasp the stress state in the construction stage of cofferdam in time,based on the measured stress,the monitoring and early warning system of the construction process is established,and the safety state of the cofferdam is evaluated.The main contents of this paper are as follows:(1)The general construction method of double wall steel cofferdam is introduced,the control method of the key construction stage of the steel cofferdam is analyzed,the water level control in the installation process of the double wall steel cofferdam under high water level is described,and the speed control and the attitude control of the cofferdam sinking process are also elaborated in detail;(2)Simplified model derivation of empirical formulas for ring coamings,vertical ribs,and flat braces of steel cofferdams,studies structural calculation theories of double-wall steel cofferdams,and provides basis for quickly judging the stress state of steel cofferdams;Methods The strength and rigidity of the double-wall steel cofferdams were analyzed and the basis for the arrangement of the stress monitoring points and the stress calculation were provided;(3)The stability of members of angle steel and steel tube braces under compression is analyzed,and the stability carrying capacity of the cofferdams under compression is calculated.;(4)The stress monitoring scheme based on the cofferdam of the engineering steel is formulated,and the monitoring and early warning system is established.The stress monitoring is carried out synchronously with the construction process.The stress monitoring of two key stages of cofferdam sinking and weir pumping is analyzed.The stress and theoretical results are analyzed and compared,and the stress state of cofferdam is analyzed in the light of the water level change under the current working condition.