| With the need of urban construction,the development and utilization of underground space is becoming more and more important.Under this background,the intersection of different municipal pipelines,subway and underground works will inevitably shuttle up and down.Heating pipe network has the characteristics of high temperature,high pressure and high thrust.Underpass the existing heating tunnel,the engineering situation is special.If underpass affects the heating equipment and pipelines,it will not only affect the normal work and life of the heating users in the surrounding areas,but also endanger the safety of the construction personnel.Especially in the heating tunnel with fixing supports,the internal heating equipments are very sensitive to the deformation of the structure.The consequences are quite serious.Based on laboratory tests and numerical simulation analysis,this paper makes a thorough study on pipe jacking through existing heating pipelines in the heating grid-connected project of Yalinxi residential area in Beijing.(1)According to the characteristics of the heating pipe network,the influence of structural deformation on the heating pipe network is analyzed.In theoretical analysis,the stress field and deformation law of tunnel excavation are studied,and combined with Peck formula,the influence of different factors on the settlement of existing tunnels is analyzed,including the influence of intersection angle between new tunnels and existing tunnels,the influence of buried depth between new tunnels and existing tunnels,and the influence of structural stiffness of existing tunnels.(2)The deformation failure of the compensator caused by the new construction project crossing the heating pipe network is simulated through laboratory tests.The deformation failure law and the maximum deformation that the bellows heating compensator may bear are studied.From the research conclusion,with the increase of the eccentricity between the straight pipe and the compensator,the pressure bearing capacity of the compensator decreases gradually,and the maximum offset is achieved under the smaller load.That is to say,under the condition of eccentric operation,the compensator actually shows geometric nonlinearity under the condition of small load,and this nonlinearity shows an aggravating trend with the increase of eccentricity and load.(3)The deformation of the existing heating tunnel underneath is studied in combination with the grid-connected heating project in Yalinxi residential area.ABAQUS finite element software is used to simulate and analyze the actual underpass projects,including the deformation of existing tunnels under surge pressure,ideal balance and under-pressure.From the point of view of the simulated structure,whether the earth silo pressure and the earth pressure can be balanced plays an important role in controlling the deformation of the existing tunnel structure and the surrounding soil.(4)According to the requirements of test and heat engine technology,the deformation control requirements are put forward,including control index,early warning value,alarm value,monitoring range and content.According to the monitoring results,these measures canwell control the displacement and settlement of existing thermal tunnels.All monitoring data in the tunnels meet the requirements of settlement control standards.There are no cracks and other obvious deformation in the structure of the tunnels. |
