Project Reports – Geotechnical Lifelines Large-Scale Testing Facility

Project Team
PI: Thomas O’Rourke, Cornell University
Co-PIs: Amjad J. Aref, State University of New York at Buffalo; Andre Filiatrault, State University of New York at Buffalo; Harry Stewart, Cornell University; Sofia Tangalos, State University of New York at Buffalo

Intelligent Liners Ensure Earthquake-Resistant Pipelines

Overview

In the United States, there are more than 2.1 million kilometers of pipelines in water and wastewater systems. Nearly half of those consist of cast-iron pipelines ranging from 50 to 100 years old.

Thanks in good measure to the work of NEES researchers at Cornell, University at Buffalo and California State University at Los Angeles these aging underground lifelines, especially those in areas of high seismic hazard, may be rehabilitated through the installation of fiber reinforced polymer liners.

The earthquake response and rehabilitation of critical lifelines can be enhanced substantially by in situ pipe lining technologies that involve the installation of fiber-reinforced polymer (FRP) linings inside existing, underground pipelines through trenchless construction procedures. In situ linings are not used currently for earthquake protection, and the absence of experimental validation and analytical procedures for evaluating the seismic response of pipelines retrofitted with FRP technology is a serious barrier to the adoption of in situ linings for improved earthquake performance.

Analytical models developed at Cornell and University at Buffalo for seismic wave and permanent ground deformation effects on underground lifelines have been successfully harnessed to full-scale tests with the dual shake table facility at the University at Buffalo (UB) and large-scale lifelines testing facility at Cornell to simulate the earthquake performance of pipelines retrofitted with FRP technology. The results show that the retrofitted pipelines are able to accommodate very high levels of transient ground motion and moderate levels of permanent ground deformation. Thus, the in situ lining technology is able to provide substantial benefits for seismic strengthening in addition to rehabilitation of aging and deteriorated underground infrastructure.

Research methodology

The research has focused on cured-in-place pipelining (CIPP) technology, which involves the insertion of a flexible tubular membrane, which is saturated with a thermosetting resin, into an existing pipeline. The CIPP linings have benefitted from prior research and development, and have been shown to be cost-effective and reliable for rehabilitation under both transient and permanent loading conditions.

Experiments in this collaborative project took place at the Cornell University Large-Scale Lifelines Testing Facility, at the University at Buffalo Dual Shake Table Facility, and at the California State University at Los Angeles (CSULA) Strength of Materials Instructional Laboratory. These laboratories were used for physical modeling in combination with advanced computational simulation to characterize the behavior of underground lined piping systems. The large-scale testing at Cornell was performed with large-stroke actuators linked together. The actuators were mounted on a reaction wall with movable pistons connected to a split test basin, which contained up to 100 tons of soil. These tests were able to simulate accurately soil-pipeline interaction under abrupt ground rupture conditions, and representative of active faulting and the most severe types of ground deformation caused by liquefaction and landslides.

Full-scale dynamic testing of underground lifeline systems was conducted in the Structural Engineering and Earthquake Simulation Laboratory at the University at Buffalo, which hosts two high performance six-degrees-of-freedom shake tables that were positioned along a trench so they were adjacent to one another. Pipeline specimens were anchored to both shake tables to simulate the passage of a seismic wave through two adjacent push-on joints. The test results showed that pipelines reinforced with CIPP linings can accommodate very high intensity ground motions and can provide substantial seismic strengthening in addition to efficient rehabilitation of aging underground infrastructure.

Intelligent linings, or linings that include flexible electronics, are an exciting new development for smart infrastructure technologies. Flexible electronics are devices on thin deformable metal or plastic foils mated to flexible polymeric substrates. In situ linings embedded with such micro sensor systems have the potential to transform local utility systems into real-time condition-monitoring and data-gathering networks.

Strain sensors capable of high strain of at least 60%, were fabricated from mixtures of multiwall carbon nanotubes (MWCNTs) mixed in polydimethylsiloxane (PDMS). The carbon nanotube and polymer mixture was optimized, and flexible gages, suitable for intelligent linings, were fabricated and tested. A 2-4% by weight mixture of MWCNTs was found to produce a mechanically strong and conductive film that could be used as a strain gage.

The team partnered with Insituform Technologies, Inc., Progressive Pipeline Management, the Los Angeles Department of Water and Power (LADWP), and the Center for Advanced Microelectronics Manufacturing at Binghampton University, which a New York State Center of Excellence for advanced research. This partnership allowed for close interaction with industry, and the qualification of seismic capabilities consistent with the actual products and conditions in the field.

Engineering Impact

The Cornell and University at Buffalo team has developed a fundamental understanding – as well as analytical capabilities – for the in situ reinforcement of lifelines. By combining full-scale experimental validation and computational simulation, the researchers are creating design and construction guidelines for such retrofits.

The research has dramatically increased the options for seismic mitigation of underground lifelines: in situ lining technology has been qualified to retrofit existing underground infrastructure, averting the serious traffic and business disruptions and associated costs of excavating and replacing underground infrastructure in urban environments. The research work also has been disseminated to the water-industry through annual short courses and has been a catalyst in the U.S. to use rehabilitated pipes.

The research has explored the use of flexible electronics for combining micro-sensor systems with in situ linings to create intelligent pipelines as a result of in situ rehabilitation.. The results of this work have the potential to transform underground utilities into real-time condition monitoring and data collection networks.

The research has shown that FRP linings installed with trenchless construction methods can improve substantially the seismic response of existing pipelines in addition to enhancing performance and extending life under daily loading conditions. The additional seismic improvements from in situ rehabilitation will provide more retrofit options in the future and open new markets for trenchless construction and in situ rehabilitation companies. The knowledge gained from the comprehensive experimental program provides the basis for future improvements and optimization in the manufacturing and installation of FRP linings. Experiments with multiwall carbon nanotubes and polymer mixtures for flexible strain gages provides the catalyst for further development of flexible electronics suitable for intelligent linings in existing underground infrastructure.

Educational Impact

Education of the work force was pursued in this project by conducting two annual 2-day short courses, entitled “Water Supply Seismic System Performance, Planning, and Asset Management”, at LADWP. The short courses were held at the LADWP conference facility, with participation of scores of LADWP managers and engineers, local consulting engineering companies, and Hispanic students from CSULA. Each short course was video-taped by LADWP and made available to NEEScom. The videoed courses were available at the Cornell and University at Buffalo NEES web sites.

Research findings from this project were integrated into a freshman engineering course at CSULA, in which the students were required to perform a preliminary design of a new water conveyance system and support facilities, including a dam, pump station, and pipeline that supplies water to a local southern California community. This course has been the foundation of a strong civil engineering design program that received two national awards for senior design projects.

Representative Research Publications

Bouziou, D., Wham, B.P., O’Rourke, T.D., Stewart, H.E., Palmer, M.C., Zhong, Z., Filiatrault, A., and Aref, A. (2012) “Earthquake Response and Rehabilitation of Critical Lifelines,” Proceedings, 15th World Conference on Earthquake Engineering, Lisbon, Portugal, 10p.

Farhidzadeh, A., Dehghan-Niri, E., Zhong, Z., Salamone, S., Aref, A. and Filiatrault, A. (2014). “Post-Earthquake Evaluation of Pipelines Rehabilitated with Cured in Place Lining Technology using Acoustic Emission,” Construction and Building Materials 54C, 326-338.

Purasinghe, R., Shamma, J., Lum, H., (2013),” Engaging Students’ Creativity and Interest Early Through a Freshman Civil Engineering Design Course, 5th First Year Engineering Experience (FYEE),” Conference, Pittsburgh, PA, Session F1B.

Wham, B.P., Argrou, C., Bouziou, D., O’Rourke, T.D., Stewart, H.E., and Bond, T.K. (2014), “Jointed Pipeline Response to Earthquake Induced Ground Deformation,” Proceedings, 10th U.S. National Conference on Earthquake Engineering, Anchorage, Alaska, Paper ID:102

Zhong, Z., Bouziou, D., Wham, B.P., Filiatrault, A., Aref, A., O’Rourke, T.D., and Stewart, H.E. (2014). Performance Evaluation of Water Pipelines Retrofitted With Cured In Place Pipe Liner Technology under Transient Earthquake Motions, Proceedings, 10th US National Conference on Earthquake, Anchorage, Alaska, Paper ID: 490.

NEES Summary Report

Evaluation of Ground Rupture Effects on Critical Lifelines

Award #0421142 NEES project #13

Project Team
PI: Thomas O’Rourke, Cornell University
Co-PIs: Harry Stewart, Cornell University; Kathleen Krafft, Sciencenter; Michael O’Rourke, Renssalaer Polytechnic Institute; Michael Symans, Renssalaer Polytechnic Institute

Ductile, Plastic Pipelines Secure Critical Services in Seismic Zones

Overview

In terms of earthquake engineering, a “lifeline” has special meaning. Specifically, lifelines are parts of critical systems that deliver resources and services necessary for the economic well-being and security of our communities. Lifelines provide many essentials, such as: power, fuels, telecommunications, transportation, waste disposal, and water.

NEES researchers, using a unique combination of large-scale soil-structure interaction at Cornell and centrifuge-scale split box testing at Rensselaer Polytechnic Institute (RPI), performed a systematic and comprehensive assessment of ground rupture effects on critical underground lifelines. Deliverables from the project include: 1) quantification of serviceability and ultimate limit states for critical lifelines, 2) improved analytical procedures and guidelines for design, 3) experimental databases for benchmarking future numerical models and guiding the evolution of numerical simulations for soil-structure interaction, and 4) validation and guidance for advanced sensor and robotics deployment in underground conduits.

The large-scale and centrifuge experiments demonstrated superior performance of high density polyethylene (HDPE) pipelines under abrupt ground rupture caused by earthquakes.
Polyethylene pipelines are made by thermo-welding lengths of pipe together to form a continuous pipeline. Conventional, segmental pipelines, by contrast, are not continuous. They have couplings, or joints, which often are not restrained from pullout under tension caused by seismic loading. Segmental pipeline joints are generally weaker in bending and tension than a continuous pipeline of the same material.

Research Methodology

This research on the safety and reliability of critical infrastructure was conducted at two NEES equipment sites: Cornell University and Rensselaer Polytechnic Institute (RPI). The equipment at these sites allows for large-scale soil-structure interaction and centrifuge-scale split box testing.

Cornell has large-displacement servo-hydraulic actuators and ancillary hydraulic systems, soil storage facilities and frame support systems for large-scale lifeline soil-structure interaction, and a variety of instrumentation and data acquisition systems. The facility allowed researchers to concentrate on detailed soil-structure-interaction for accurate representation of both the soil and buried lifelines in the vicinity of ground ruptures, where it is most important to duplicate pipe and soil material behaviors and reactions.

RPI has advanced split-box-centrifuge containers for simulating lifeline systems. These containers were used on the recently upgraded RPI 150 g-ton centrifuge. The research at Cornell involved the largest laboratory tests ever performed on pipeline response to ground rupture. Approximately 100 tons of soil were sheared and ruptured, generating fault displacements of 1.2m (4 ft) at the center of a 400-mm diameter pipeline composed of high density polyethylene. The RPI facility through multi-g scaling, was able to simulate larger prototype dimensions, and faster rates of loading. Both sites use telepresence (teleobservation, teleoperation, and teleparticipation) consistent with NEESgrid specifications.

Large-scale testing at Cornell provided detailed, full-scale experimental data to compare with RPI centrifuge data and advanced numerical modeling of soil-pipeline interaction. While emphasis was given to highly ductile pipeline material, such as HDPE, significant attention was also given to steel pipelines used in numerous critical fuel, water, and electrical power facilities.

The experimental evidence provided by the full-scale tests confirmed the substantial ductility of HDPE pipe and the beneficial effects of its highly ductile performance in accommodating permanent ground deformation. The maximum measured strains for strike-slip displacement were far below strain levels associated with rupture of the pipe wall. The maximum reduction of pipe diameter due to ovaling, however, was greater than expected. The experimental evidence therefore shows that loss of pipe cross-sectional area due to ovaling is likely to be the mode of deformation governing failure of larger HDPE pipes for earthquake-induced ground rupture effects.

Engineering Impact

In Christchurch, NZ, the deployment of HDPE pipelines is being used to improve substantially the performance of water and wastewater systems following the Canterbury Earthquake sequence. In Los Angeles, HDPE pipelines are being used to reduce the seismic risk to the Los Angeles Aqueducts at the location where they cross the San Andreas Fault. In San Francisco, HDPE pipeline designs are being advanced for seismic retrofitting of critical facilities within the Auxiliary Water Supply System.

After the 2010 Darfield earthquake in New Zealand, NEES researchers with other members of a reconnaissance team advised the Christchurch City Council to replace damaged parts of its water distribution network with HDPE pipelines. The results were stunning. Even though two subsequent earthquakes induced soil liquefaction in the area of replacement, involving lateral spreading and settlements as large as 2 m, there was not a single location of repair in the HDPE replacement pipelines.

Building on NEES test results and the favorable Christchurch pipeline performance, LADWP engineers are installing HDPE pipelines in the Elizabeth Tunnel, which carries all Los Angeles Aqueduct water across the San Andreas Fault. The tunnel is about 3 m wide and conveys water by gravity flow. Pipelines of about 900 mm nominal diameter will be installed. The HDPE pipelines will be able accommodate as much as 2.5 m of lateral fault rupture, thereby conveying water even when the tunnel is virtually cut off. This installation is a cost-effective way to reduce the risk of fault rupture from more frequent, lower magnitude earthquakes.

Many water supplies and wastewater systems are beginning to deploy polyethylene piping for enhanced resilience to earthquakes, as well as other natural hazards. The use of highly ductile pipelines is expected to grow substantially in the future. The pipeline industry is now developing segmental pipelines that can accommodate large joint extension, compression, and rotation to accommodate earthquake-induced ground movements. Hence, the next generation hazard-resilient pipelines are being advanced by research and development at various companies, following the lead of NEES research.

Educational Impact

In coordination with Cornell and Rensselaer Polytechnic Institute, the Sciencenter in Ithaca, NY developed an interacive traveling exhibition for science museums called When the Earth Shakes. The 800-ft2 exhibition shows how engineers at NEES sites study earthquake effects with networked experimental facilities. It includes a simple hands-on shaketable for K – 6 children to learn the basics of dynamic response and structural reinforcement and an interactive tsunami tank that allows users to experiment with wave-structure interaction. The exhibition reaches over 100,000 people annually and allows offsite, web-based participation to broaden the range of outreach and demonstrate the capabilities of a collaboratory approach.

As part of the larger exhibition, five 90-sec. videos have been produced that feature earthquake footage, real engineers and experiments, and describe how their work is making our built world safer through research. The videos won several awards, including 1) Silver Davey Award, 2) Certificate of Merit from the Chicago Film Festival’s INTERCOM video competition, 3) Bronze Telly Award, 4) Bronze Award at the Millenium Awards, Award of Excellence at the 15th Communicator Awards, and 5) Silver Award at the Horizon Interactive Awards. Cornell, RPI, and the Sciencenter won the Most Effective Education, Outreach, and Training Activity of the Year recognition from NEESinc in 2009 on behalf of the NSF-sponsored Network for Earthquake Engineering Simulation.

Representative Research Publications

Abdoun, T. H., Ha, D., O’Rourke, M. J., Symans, M. D., O’Rourke, T. D., Palmer, M. C., & Stewart, H. E. (2009). Factors influencing the behavior of buried pipelines subjected to earthquake faulting. Soil Dynamics and Earthquake Engineering, 29(3), 415-427.

Ha, D., Abdoun, T. H., O’Rourke, M. J., Symans, M. D., O’Rourke, T. D., Palmer, M. C., & Stewart, H. E. (2010). Earthquake Faulting Effects on Buried Pipelines–Case History and Centrifuge Study. Journal of earthquake engineering, 14(5), 646-669.

O’Rourke, T.D. (2010) “Geohazards and Large Geographically Distributed Systems”, 2009 Rankine Lecture, Geotechnique, Vol. LX, No. 7, July, 2010, pp. 503-543.

Palmer M.C., T. D. O’Rourke, N. A. Olson, T. Abdoun, D. Ha, and M. J. O’Rourke (2009) “Tactile Pressure Sensors for Soil-Structure Interaction Assessment”, J. Geotechnical and Geoenvironmental Engr., ASCE, Vol. 135 (11), 1638-1645.

Xie, X., Symans, M. D., O’Rourke, M. J., Abdoun, T. H., O’Rourke, T. D., Palmer, M. C., & Stewart, H. E. (2013). Numerical modeling of buried HDPE pipelines subjected to normal faulting: A case study. Earthquake Spectra,29(2), 609-632.

2009 NEES Final Report