Non-uniform Temperature Effect And Mechanical Behavior Of Foundation Pit Retaining Structure Under Solar Radiation

Due to insufficient understanding of the temperature stress changes of the foundation pit under solar radiation,a lot of pit hazards happened under temperature stress.Practice shows the influence of strong solar radiation on the foundation pit support structure can not be ignored.However,the temperature of the surface of the concrete structure is strongly non-uniform and time-varying due to multi-factor dynamic coupling effects such as short-wave radiation of the sun,long-wave radiation of the sky,and convective heat transfer of the outside air.For deep foundation pits,when the temperature difference in the area where the foundation pit works is large,the horizontal support of the foundation pit produces large temperature stress,and further causes additional displacement and internal force of the enclosure.At present,there are few studies on the non-uniform temperature field of concrete supported by solar radiation,the multi-support non-uniform temperature field under occlusion factors and the influence of temperature changes on the foundation pit retaining system.Therefore,based on the extensive investigation of the influence of a large amount of solar radiation on the non-uniform temperature difference of concrete support and the axial force measurement data of the foundation pit support structure under the influence of large temperature difference,the theoretical analysis,numerical simulation,mathematical statistics and field test are comprehensively applied.to acquire the following main conclusions and results:(1)The temperature field of the concrete supporting structure of the foundation pit under single and multi-supported solar radiation is a non-uniform temperature field law;with the change of the sun position,the temperature field of the concrete support at different moments is different,at the same time.The maximum value of each surface is also different.The multi-support at the same time has different concrete support temperature values in the depth direction due to the occlusion relationship,and the field test of the multi-support temperature field in winter is verified.(2)The influencing factors of the concrete support temperature field were analyzed,and the influence law of each factor was obtained under the action of solar radiation.Influence factors include solar radiation absorption coefficient,ground reflection coefficient,atmospheric cleanliness,spatial position(in the north-south vertical plane,in the east-west vertical plane and in the horizontal plane)and geographical position(3)Four control temperature load calculation models for solar radiation non-uniform temperature field of concrete support section are proposed,namely: east control temperature load model,top surface control load model,west control temperature load model and night cooling load model and give the expression and time of each model.(4)Aiming at the analysis of non-uniform temperature field of multi-support concrete support,the concept of temperature-blocking ratio is proposed,and the zoning model and noon occlusion influence partition model are proposed.The weak occlusion I area,strong occlusion area,and weak occlusion zone II are proposed in the two models respectively.(5)For the influence of change on the foundation pit support structure system,firstly,horizontal displacement from the ground connection wall.Supporting axial force,ground bending moment,earth pressure and surface settlement obtained the law of foundation pit retaining structure without considering temperature change;then studied the influence of large temperature rise and fall on these five aspects,and obtained the temperature The influences of the temperature change on the structure of the foundation pit support systemwere studied,and the field measurement was carried out to verify the correctness of the numerical simulation.