Seismic Fragility Analysis Of Buried Water Supply Pipeline Before And After Retrofited By Corrosion Protection Lining

Lifeline engineering system is a basic engineering facility system that maintains the functions of modern city and regional economy.As an important part of lifeline system engineering,buried pipelines are mostly used for the transportation of petroleum,natural gas and water,maintaining the functions of modern and contemporary cities and regional economic development.In actual laying,buried pipelines inevitably pass through sites with different geological conditions,or even seismic active zones.Earthquake damage investigation and research show that buried pipelines are seriously damaged under strong earthquake,and the damage mainly concentrates on the pipeline joints,and the main failure form is tension and compression damage.The total mileage of water supply pipelines in China is increasing year by year,but a large number of existing buried pipelines are lack of necessary seismic design and measures.At the same time,with the increase of service life,corrosion and aging problems become increasingly prominent,which further aggravates the seismic vulnerability of buried pipelines.Therefore,improving the seismic performance of existing buried pipelines is an important link to ensure the safe use of urban lifeline projects.As one of the trenchless repairing methods for buried pipelines,the liner method can effectively improve the overflow,corrosion resistance and leakage resistance of buried pipelines by using high density polyethylene liner and grouting material as a whole.The reinforcement effect of this method for buried pipelines needs to be further studied.In this study,DN200 and DN400 ductile iron water supply pipelines are taken as research objects,and the research is carried out in two directions: mechanical properties of push-on joint of ductile iron water supply pipelines before and after liner reinforced;seismic response analysis and vulnerability evaluation of buried pipelines.The main research contents and result are as follows: 1.Mechanical Properties of Push-on Joint of Ductile Iron Pipe(1)Experiments were carried out on ductile iron with push-on joint water supply pipes before and after reinforced by liner method.The mechanical properties of pipeline joints under the combined action of axial force,bending moment and water pressure are studied.The mechanical properties and failure mechanism are revealed.The failure modes and failure criteria are established.(2)Comparing the mechanical properties of the push-on joints of ductile iron water supply pipelines before and after reinforced by the liner method,observing the situation of the splitting of the liner at the push-on joints of ductile iron water supply pipelines after reinforced by the liner method,and putting suggestions for the improvement of the liner method.2.Numerical Model of Push-on Joint of Ductile Iron Pipe(1)Based on OpenSees finite element platform,mechanical model of push-on joint of ductile iron before and after liner reinforced was developed.Compared with the test results of existing push-on joint of ductile iron,the fitting degree of the model and the stiffness,strength reduction and energy dissipation characteristics of pipe joint during the test process were verified.(2)Based on the developed numerical model of pipeline joint,the corresponding joint element and pipe-soil interaction element are defined,and the ductile iron underground water supply pipeline numerical model is established for seismic response analysis and vulnerability study of buried pipelines under multiple seismic excitations.3.Seismic Response Analysis and Vulnerability Study of Buried Pipelines(1)Aiming at assessing the seismic response of ductile iron underground water supply pipeline before and after liner reinforcement,the numerical simulation of uniform and non-uniform underground water supply pipeline is carried out under the action of multiple groups earthquake,which verifies the difference of the axial displacement of the push-on joint of underground pipeline in different fields.(2)For the numerical model of ductile iron underground water supply pipeline before and after liner reinforced,the incremental dynamic analysis(IDA)was carried out,and the vulnerability curve of underground pipeline interface based on PGA in non-uniform field was obtained,and the vulnerability analysis of buried pipeline was completed.