The Way Of Installation And Stress Distribution Of The Heating Pipe In The Utility Tunnel

With the acceleration of urbanization process in China,now the kinds of underground municipal pipeline of city is more,the scale is bigger,the shape is more complex,and the problem is also increasingly prominent.With the increasing kinds,bigger scale and more complex structure of pipeline in the city due to the acceleration of urbanization process,the situation of pipeline management underground becomes more servere.Therefore,in order to utilize urban underground space rationally,the urban underground utility tunnel is proposed.In the northern city,heating pipe is a kind of important municipal pipeline which is bringing many economic and social benefits in the utility tunnel system.However,in the technology standards which has been implemented on urban heating pipe,there is no content about laying method of heating pipe in it.In January 2016,the Ministry of Housing and Urban-Rural Development compiled the national architecture standard design system for urban utility tunnel.In this standard design system,the utility tunnel heating piping laying and installation is still in the planning process.Therefore,the way of installation and stress distribution of the heating pipe in the utility tunnel is worth being discussed,and the internal medium of the heating pipe we discussed is hot water.Firstly,this paper made a brief introduction to the related contents of the utility tunnel,and then introduced the existing urban outdoor heating pipe laying mode and its advantages and disadvantages,according to the characteristics of the utility tunnel,the laying mode of heating pipe in the utility tunnel was put forward.Secondly,heating pipe which diameter is DN800 with 96m-length,local applied force test at aerial state,preliminarily verified the feasibility that reduce the pipeline axial thermal elongation by applying force in some local location preliminarily.Finally on the basis of test results,the heating pipe model in utility tunnel is established by using the finite element analysis software ABAQUS,and the pipe diameter for the DN600,DN800 and DN1000 overhead heating pipes in different pressure(1.0MPa,1.6MPa and 2.5MPa)under applying the simulation for different size after partial external forces.Following conclusions will be revealed in this paper:(1)When the overhead heating pipe in the absence of locally applied force,the test axial thermal elongation is less than the theory axial thermal elongation,but both have the same change trend.(2)When the aerial heating pipe in the local applied force,the unit temperature of axial thermal elongation is less than the unit temperature of axial thermal elongation in the absence of any compelling force.(3)Under the same temperature difference and the same pipe diameter of the heating pipe,the more pressure,the smaller the axial thermal elongation.(4)The axial force and axial thermal elongation must be applied in the heating pipeline had a linear relationship.The slope of the linear relationship is only related to the diameter of the heating pipe,not the temperature and stress,intercept is the axial thermal elongation of heating pipe in overhead at absence of compelling force state.(5)The axial thermal elongation of the heating pipe is only related to the total external force exerted on the pipe,which is independent with the number of positions that can be applied to the pipe.