Study On The PCCP Crack Form Under The Impact Of Interal Pressure

Due to its advantages of good combination of performance,prestressed concrete cylinder pipe(PCCP)become the preferred material for large diameter and long distance water conveyance.It is widely used in multiple fields such as water conservancy,electric power,and municipal,therefore,it is practically important to study the failure mechanism of PCCP.This thesis imployes the software of ADINA to establish the three-dimensional finite element model of PCCP.By simulating a series of process such as PCCP prestressed clamp,backfill soil backfilling in the process of construction,the internal pressure,this thesis analyzes the impact of each load step of PCCP concrete circular stress.With the increase of the internal water pressure,this thesis also analyzes concrete stress,strain and fracture distribution,under various operating conditions,determines the crack form of each characteristical parts,and elaborates the reason of different crack forms combining the conditions of the tube deformation,,and then analyzes the effect of broken wires of PCCP concrete cracks and draw the following conclusions:1.Regarding the tube body stress changes: with the increase of the internal pressure,the stress variation between the PCCP materials has obvious difference,and the crack development of different layers of material and the crack form is different,mainly with tension as a whole.2.Regarding the tube deformation situation: after construction,backfilling,the tube body is elliptical deformed;with the increase of the internal pressure,,the pipe body overall expands outward,the deformation degree of each part is different,the top expands obviously,causing a biggest deformation on both sides of the pipe roof..3.Regarding the development of the pipe body crack: the crack development order of outer tube core feature area : The outer edge of the waist cracks → The inside of the pipe bottom cracks→The inside of the pipe roof cracks→Through crack in the waist→Through Crack on the top of the tube → Through crack in the pipe bottom.The crack development order of inner tube core area: The outer edge of the waist cracks →The inside of the pipe bottom cracks→Through Crack on the top of the tube→Through crack in the pipe bottom→ The outer edge of the waist cracks.4.Regarding the cracks form of the characteristical parts: The bottom and outside of the waist of the outer tube core are closed crack;The bottom of inner tube core are crushed crack,the outer are closed crack,other parts are all open crack.Tube core as a whole is mainly with open crack,and is partly damaged with compression damage.5.Regarding the reasons of different forms of cracks: with the internal pressure increases step by step,the tube body cracks,causing redistribution of the pipe body,internal water pressure further increases,leading to more cracks,tensile capacity loss,ongoing stress redistribution,with the change of the external load and boundary conditions to make the tube body deformation,stress redistribution of the pipe body and pipe body deformation stress change,leading to different crack forms.6.Regarding the impact of broken wires on the mechanical behavior of PCCP : the appearance of the broken wire tube causes the decrease of the internal pressure on the first crack,the development of the crack condition changes,and the corresponding crack principal stress direction changed from simple toroidal to Stacking direction.