Experimental Evaluation of Ductile Iron Pipeline Response to Earthquake-Induced Ground Deformation

Pariya-Ekkasut, Chalermpat

Experimental Evaluation of Ductile Iron Pipeline Response to Earthquake-Induced Ground Deformation

Abstract

This thesis addresses the performance of ductile iron (DI) pipelines with restrained axial slip joints subject to earthquake-induced ground deformation. DI pipelines account for 23% of U.S. water distribution systems (US.EPA, 2013), and have been used extensively for replacing aging cast iron (CI) pipelines. Under earthquake-induced ground deformation a jointed DI pipeline is vulnerable primarily to joint pullout and excessive joint rotation. Improvements in pipeline technology have led to the development of DI pipelines with restrained axial slip joints that move axially and rotate to conform to differential soil movements, but are restrained from pullout without leakage and loss of structural integrity. A series of large-scale experiments was performed on DI pipelines with restrained axial slip joints to characterize tensile strength properties, direct axial compression and tension, moment vs rotation characteristics, soil axial restraint, and performance in response to fault rupture. Large-scale tests were performed primarily on 6-in. (150-mm)-diameter DI pipelines, but also included direct tension and bending tests on 12-in. (300-mm)-diameter DI pipelines. The direct compression tests show either leakage or irrecoverable deformation in the form of large rotation at loads equal to or slightly higher than load consistent with the proportional limit stress of DI pipe. The direct tension tests show that tensile failure of the pipeline depends on the locking mechanism of the joint. Joints that use full circumferential locking rings generate the highest resisting force. Failure and leakage under tension with these features occurred as DI ring shear fracture and bell fracture. In contrast, joints that use locking segments mobilized lower pullout force. Failure and leakage of joints with locking segments occurred as local deformation at the spigot caused by load concentration at the locking segments, allowing the weld bead to slip past the locking segments and cause leakage. Large-scale fault rupture tests provide a comprehensive and detailed understanding of the sequence of joint movements, combined axial pullout and rotation at each joint, and the actual axial forces influenced by longitudinal frictional resistance and axial resistance to movement at the joints. The longitudinal frictional forces are controlled by at-rest (Ko) conditions, which set the initial state of stress along the pipeline near the north and south ends of the split basin, and the conditions of maximum lateral soil reaction during fault rupture, which establish the maximum longitudinal frictional resistance for the pipeline in the vicinity of fault rupture. The joint axial resistance model proposed in this work is obtained from the expression for face resistance of the leading edge of a jacked pipe proposed by Meskele and Stuedlein (2015) from the work of Weber and Hurtz (1981). The model is used to predict the axial resistance from a restrained axial slip joint for DI pipe and the pullout restraints of PVCO and PVC pipelines. The proposed model provides for relatively close prediction under Ko conditions within ±15% of the actual maximum load measured during full scale soil axial resistance tests.

Date Issued

2018-05-30

Keywords

Civil engineering; Ductile iron pipe; Fault rupture; Ground deformation; Jointed pipelines; Large-scale experiments; Water distribution systems

Committee Chair

O'Rourke, Thomas Denis

Committee Member

Stewart, Harry Eaton
Grigoriu, Mircea Dan

Degree Discipline

Civil and Environmental Engineering

Degree Name

Ph. D., Civil and Environmental Engineering

Degree Level

Doctor of Philosophy

Types

dissertation or thesis