Full‐scale shaking table tests on soil liquefaction‐induced uplift of buried pipelines for buildings

Abstract

The uplift effect induced by soil liquefaction on buried pipelines that are critical to the serviceability of buildings, including potable water, natural gas, and sewage pipelines, was experimentally investigated. A full‐scale physical model of pipelines buried in liquefiable ground comprising distribution mains and service lines that connect distribution mains and buildings was built. Shaking table tests were conducted on this model with actual earthquake records utilized as the input motions. The performance of gravel as pipe ditch backfill for mitigating the liquefaction‐induced uplift was also evaluated. During the tests, accelerometers and piezometers were installed in free‐field (FF) soil and around the pipelines to reveal the pipeline–soil interaction and the soil liquefaction development. Wire potentiometers were also utilized to monitor any uplift or subsidence of the pipelines. Results indicate that the distribution mains for natural gas and sewage experienced an uplift during liquefaction of ground specimen. The excess porewater pressure buildup level around the uplifted pipelines was generally lower than that in FF soil and was even lower on top of the pipeline circumference, which may be attributed to the pipeline–soil interaction. Furthermore, the practicability of an existing simplified model for anti‐uplift stability assessment and its corresponding uplift force estimation were examined based on aforementioned observations. The findings indicate that the uplift effect for large‐diameter pipelines may be underestimated by simply using this simplified model. This research can be used as a reference for the seismic design of buried pipelines, which is beneficial for disaster prevention and mitigation.

An experimental study of the impact of liquefaction‐induced displacement on buried pipelines for buildings

“…The flexural strains on the top and bottom of the pipe due to settlement and at the side due to lateral spreading along the transverse direction were observed; however, no yielding of the pipe occurred. Besides, both centrifuge and full‐scale shaking table tests were used for the investigation of pipeline uplift, such as Chian et al 8 . and Ko et al 21 .…”

“…This type of forced displacement test is the follow‐up study of the full‐scale shaking table tests on soil liquefaction‐induced uplift of pipelines buried in sandy ground 8 . The setup of these shaking table tests is shown in Figure 1.…”

“…The purpose was to further examine the performance of CSSP by comparing the mechanical behavior of both pipelines. A screw jack was used to impose the free‐end deflection caused by the uplift effect during the shaking table tests, 8 as shown in Figure 3. The jack was hinge‐connected to the free ends of the pipelines with a universal joint to prevent bending and torsion restraints (as shown in the photo in Figure 3).…”

“…For the free end of the cantilevered potable water service lines, the target displacement was 5.1 cm (upward). These values were based on the maximum accumulated subsidence/uplift of the corresponding pipelines during the shaking table tests 8 . All these forced displacement tests were conducted without soil surrounding the pipelines.…”

“…One simulated the subsidence or uplift of distribution mains during liquefaction due to EPWP buildup or soil degradation. The displacement of distribution mains was based on observations from previous full‐scale shaking tests 8 . Complete liquefaction of the soil surrounding the pipeline was considered because this is how pipeline uplift usually occurs.…”