A study on bearing characteristic and failure mechanism of thin-walled structure of a prefabricated subway station

In order to study the bearing performance of a new type of prefabricated subway station structure(PSSS),firstly,a three-dimensional finite element model of the PSSS was established to study the nonlinear mechanics and deformation performance.Secondly,the bearing mechanism of a PSSS was investigated in detail.Finally,the development law of damages to a thin-walled prefabricated component and the failure evolution mechanism of a PSSS were discussed.The results showed that this new type of the PSSS had good bearing capacity.The top arch structure was a three-hinged arch bearing system,and the enclosure structure and the substructure were respectively used as the horizontal and vertical support systems of the three-hinged arch structure to ensure the integrity and stability of the overall structure.Moreover,the tongue-and-groove joints could effectively transmit the internal force between the components and keep the components deformed in harmony.The rigidity degradation of the PSSS caused by the accumulation of damages to the spandrel,hance,arch foot,and enclosure structure was the main reason of its loss of bearing capacity.The existing thin-walled components design had significant advantages in weight reduction,concrete temperature control,components hoisting,transportation and assembly construction,which achieved a good balance between safety,usability and economy.

Analytical model of vertical load acting on jacked pipe considering soil arching effect in cohesionless soil

For the project of pipe jacking in cohesionless soil,it is key to determine the vertical load on jacked pipe so as to predict the jacking force accurately.In this paper,a new parabolic soil arching model was proposed to calculate the vertical load on jacked pipe.This proposed analytical model was composed of parabolic soil arching zone,parabola-typed collapse zone and friction arch zone.Combined with existing literature,the key parameters(i.e.,height of parabolic soil arching,horizontal pressure coefficient and width and height of friction arch)were determined.In addition,considering that the trajectory of major stress is parabola,the formula of horizontal pressure coefficient was deduced in the friction arch.The parabolic soil arching zone is assumed as a three-hinged arch with reasonable arch axis,and the formula of load transfer was derived considering the transition effect of parabolic soil arching.The results of experiment,theoretical models and numerical model were adopted to verify the proposed analytical model.Finally,the influence of the key parameters on the vertical load on jacked pipe were also discussed in detail.This work provides a meaningful reference for evaluating the vertical load on jacked pipe for design of pipe jacking.