大型沉井下沉过程中结构受力特性试验OA

An essential foundation for assessing the structural safety of the caisson sinking process is the stress condition of the side wall and partition wall.However,the equations for caisson forces in current codes are based on the theory of elasticity for simple members,and most research results are based on small-to medium-sized caissons. The completed construction of a large caisson with coarse grating at a wastewater treatment plant was used as a study object.The stress in the sidewall and partition wall during the caisson sinking process was monitored and combined with numerical simulation,the caisson's structural stress distribution and change rules were analyzed. The findings show that:(1)the side wall and partition wall repeatedly cut into the soil during the caisson sinking process due to the increase and decrease cycle of the structural stress;The short-side partition wall reinforcement stress maximum value during caisson sinking is 31.6 MPa,while the long-side partition wall stress maximum value is only 5.1 MPa;The short-side partition wall reinforcement is necessary in the design.(2)At the start of the caisson sinking,the maximum tensile stress at the bottom of the partition wall is 1.40 MPa,and the maximum compressive stress at the top of the partition wall is 1.28 MPa.When the sinkhole is sunk to a depth of 9 m,the lower and middle portions of the caisson are under compressive stress,with higher compressive stress at the intersection of the side wall and partition wall,with stress extremes of 1.51 MPa.When the caisson is sunk to the design elevation,the maximum compressive stress is 3.51 MPa,and the tensile stress is up to 2.65 MPa. In summary,as the sinking depth increases,the soil constraint can effectively reduce the partition wall and side wall stresses.Reinforcement stress in short-side partition walls is much higher than in long-side walls,so short-side partition walls require reinforcement in the design.The caisson bends downward during the early stages of sinking.When the sinking depth reaches 9 m,the tensile stress at the bottom of the partition wall essentially vanishes,and the caisson's stress state changes from the bending member to the compression member.Once the caisson has sunk in place,the entire caisson behaves in the state of compression,with the maximum tensile stress occurring at the inner surface of the long-side side wall and the maximum compressive stress always occurring at the intersection of the bottom long-side partition wall.The stress trends at different sections of the upper and lower levels of the caisson are opposite.The resulting rules can guide targeted monitoring of structural stresses.The construction of caisson structures can be guided by the distribution and change rule of structural stress during caisson sinking.