Research On Crack Resistance Of Prefabricated Underground Comprehensive Pipe Corridor Under Construction Conditions

The underground comprehensive pipeline corridor is the "economic artery" of urban operation,which centralizes all kinds of pipelines needed by urban operation into one for management.In recent years,the state has intensively issued relevant policy documents and standards,actively promoted the construction of comprehensive pipe corridor,rationally utilized the limited and precious resources of underground space,and improved the comprehensive bearing capacity of the city.Cracking is a common quality problem in underground concrete structures.There are many factors affecting the formation of cracks and the mechanism of cracking is complicated.With the pressing needs of the comprehensive utility tunnel construction,the pipe gallery crack resistance is an urgent need to solve problems,to practical engineering optimization design in the pipe gallery section stiffness,foundation reinforcement treatment,utility tunnel construction technology,etc,to provide theoretical support and technical support,construction and better prevent safety accidents and economic losses caused by cracks.In view of this,this article uses the field solid test,finite element numerical simulation,static analysis to study the anti-cracking performance of the prefabricated underground comprehensive pipe corridor by factors such as the load,temperature,shrinkage and creep of the concrete pipe corridor and construction.With a view to providing reference value for the design and construction of the comprehensive pipe corridor in the future.Mainly completed the research work in the following aspects:(1)The main research contents and achievements of prefabricated underground comprehensive pipe gallery cracks at home and abroad are summarized,and the existing problems are analyzed.The research content and route of integrated pipe gallery solid engineering test are put forward.According to the requirement of economy,feasibility and effectiveness of field test,the characteristics of different instruments are analyzed.According to the test purpose and requirement,the monitoring parameter instrument and data acquisition instrument are determined.(2)Based on the integrated pipe gallery solid project,the test method and test sequence are determined.Abundant experimental data are obtained to provide data analysis support for the genesis of fractures.(3)The law of stress change and the cause of crack of precast underground pipe gallery under different conditions are analyzed.(4)The comprehensive stress condition of prefabricated underground pipe gallery was obtained through numerical analysis,and the stress amplitude variation rule under different conditions was analyzed.(5)According to the stress amplitudes under different conditions,the variation law of the stress peak amplitude and the genesis of fractures is obtained.It can provide an effective reference for the future research on the genesis and mechanism of cracks in prefabricated underground pipe corridors.The main conclusions are as follows:(1)Monotonous concentrated static load indicates that there is obvious force deformation at the mid-span of the roof,and the deformation of the side plate is relatively small.It fully shows that the mechanical performance of the vertical prefabricated pipe corridor structure meets the regulations.(2)Analysis of the monitoring results of stress and strain in the soil around the pipe corridor during the construction backfill stage shows that:As the depth of the overlying soil increases,the horizontal and vertical mechanical deformation of the pipe corridor structure shows a linear growth trend.From the overall point of view,the longitudinal deformation is more obvious,however,the horizontal deformation of the roof of the pipe corridor mainly occurs laterally.The yield failure of the prefabricated pipe corridor roof is mainly divided into four stages.The first crack appears in the first stage,the second stage cross-medial and lateral compression yield failure,the third stage tensile cracking at the axillary angle,and the fourth stage steel bar tensile Yield to destruction.(3)Comparative research under different tonnage roller combination working conditions shows that under the conditions of temperature,bulldozing height and other factors,as the load of the roller increases,it has a certain effect on the crack resistance of the tube corridor.With the increase of the tonnage of the roller,it accounts for a large part of the load.After the cracks appear,it is difficult to recover elastically and will exist permanently.It is manifested as load cracks in the middle of the pipe gallery roof and floor caused by the load.Provide a reference for the research on how to increase the crack resistance of the pipe corridor during the construction process.