Study On The Determination Method Of Construction Load Based On The Analysis Of Whole Effect Of Shield Tunnel

Shield tunnel is in the construction environment of multi field coupling of seepage field and stress field.The load action mode of the structure is complex,there are many kinds of loads,and the stage action is obvious.All of these make it difficult to design the shield tunnel structure.At present,grouting pressure,Jack thrust and shield tail brush reaction are generally considered for construction load.The construction load is calculated by combining with earth pressure.However,the calculation and action mode of construction load are lack of clear basis.Generally,the construction load is analyzed simply according to the engineering experience.Therefore,the calculation theory and action mechanism of construction load are proved.In this paper,the detailed,clear and systematic method to determine the construction load is of engineering value.This paper mainly studies from the following aspects:(1)Analyze the existing earth pressure calculation theory.According to the geological conditions of soft soil area,the pressure calculation method of layered soil layer is improved.Through the three-dimensional numerical simulation of tunnel excavation,the deep and shallow depth limits of shield tunnel in soft soil area are defined clearly.In this paper,the earth pressure calculated by the model is compared with various theoretical calculation results.Finally,the calculation flow of accurately determining the earth pressure is formed.(2)The paper makes a comparative analysis of the existing grouting pressure diffusion theory.The model of fan-shaped filling diffusion after grouting with time-varying wall is improved.Through the comparison between the theory and the actual monitoring data,this paper proves the rationality of the theoretical derivation.Through the structural calculation of beam spring model,the reasonable arrangement of grouting holes is determined.A set of calculation methods for grouting pressure,distribution and hole location are formed.(3)Through the compression test of the shield tail brush,the paper puts forward the value range and loading mode of the reaction force of the shield tail brush.Based on the coupling of earth pressure,grouting pressure and shield tail brush reaction,the whole refinement model of straight and curved shield tunnel is established.This paper studies the mechanical response of Jack thrust deflection angle to the structure.In this paper,the control threshold of Jack thrust deflection angle is determined,and the existing calculation theory of Jack thrust is improved.(4)According to the plastic damage theory,the combination coefficient and single load influence coefficient of construction load are determined.The method of sub item combination of construction load is put forward.Finally,the load calculation theory of shield tunnel structure design and construction is formed.Through the above research,a set of relatively complete calculation technology of shield tunnel lining structure is formed.Structural calculation technology provides calculation method for shield tunnel design stage.Structural calculation technology provides control parameters for shield tunnel construction stage.It has practical significance of guiding function.