Analysis of the impact of pile foundation steel casing construction on longitudinal deformation of adjacent railway frame bridge
The construction of metro pile foundation steel casing in proximity could cause additional stresses and deformations in the frame bridge of existing operating railway.Relying on the Changsha metro line 1 north extension viaduct pile foundation close to the frame bridge of existing railway,the calculation method of longitudinal deformation of the frame bridge caused by the construction of steel casing is established based on the Mindlin stress solution and the Pasternak foundation beam.The accuracy of the method is verified with measured data,and the influence principles of pile diameter,elastic modulus of the ground,relative clear distance and additional force of construction on the longitudinal deformation of the frame bridge are analyzed.The results show that:during the construction of steel casing,the additional forces on the surrounding soil mainly include soil plug pressure,radial pressure on the casing side and friction on the casing side,and the construction disturbance mainly originates from the rotary process of the steel casing;the frame bridge bulges and then gradually settles with the increase of the construction depth of the steel casing;the friction on the casing side is the main factor of the deformation of the frame bridge,and the radial pressure has the least influence on deformation;the longitudinal differential settlement is proportional to the pile diameter,and the elastic modulus and the relative clear distance are proportional to the pile diameter;the relative clear distance is the main control factor for the deformation of the frame bridge,and the deformation gradually tends to zero when it is outside the range of 4 times of the pile diameter.During the construction process,the deformation of the frame bridge can be controlled from the perspective of increasing the modulus of elasticity and relative clear distance,decreasing the soil plug pressure,casing resistance and pile diameter,and the research results could provide a basis for the design and construction of similar projects.
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