Abstract
Large caisson constructed in the soft soil layer is prone to rapid sinking during the sinking process. Rapid sinking is often accompanied by partial sinking, which affects construction safety and subsequent construction. There is no relevant early warning mechanism for early warning of rapid sinking. This paper takes the sinking construction of a large land caisson in a deep silt layer as an example, analysis the rapid sinking mechanism through the earth pressure and settlement rate of the sinking process, and proposes a rapid sinking early warning mechanism. Before the rapid sinking, the soil at the edge of the blade feet is partially plastic damaged, and the earth pressure decreases continuously after reaching its limit value; The strain softening of the overlying soft soil layer, the rapid reduction of side friction and the instability of open caisson caused by soil gushing after the plastic zone connecting are the important reasons for the rapid sinking. The rapid sinking process is divided into “sagging section, starting section, instability section and stable section”. The earth pressure early warning mechanism is the continuous decrease of the earth pressure at the blade feet. When the sinking rate exceeds the threshold value for two hours, it is regarded as the early warning mechanism of sinking rate. Using this dual control mechanism of end earth pressure and sinking rate can effectively warn the rapid sinking of the caisson.
Highlights
With the development of long-span bridges, the caisson, as the foundation, is developing in the direction of large size, multi compartment and more complicated geology
Large caisson constructed in the soft soil layer is prone to rapid sinking during the sinking process
Rapid sinking is often accompanied by partial sinking, which affects construction safety and subsequent construction
Summary
With the development of long-span bridges, the caisson, as the foundation, is developing in the direction of large size, multi compartment and more complicated geology. Chang Dabao [2] studied the difficulties encountered in the construction of several large caissons and their solutions; pointed out that the weight ratio of open caisson should be increased properly in the design of open caisson, and the reasonable setting of sinking aid measures are the key to make it smooth sinking. He Qiaoling et al [3] based on the monitoring data of the earth pressure on the side wall of the South Anchorage caisson of Taizhou Yangtze River Bridge, analysed the variation law of the earth pressure on the side wall of the caisson. Based on the sinking construction of an anchor caisson foundation of a suspension bridge, this paper studies the rapid settlement early warning analysis based on monitoring data, discusses the rapid sinking mechanism, and provides a reference for similar projects
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