Performance of sewer pipes with liner during earthquake

Abstract

This report investigates the performance of sewer pipes equipped with AM-liner during earthquakes. The AM-liner’s performance as structural retrofitting measure to earthquakeproof sewer pipes has never been established. The extent of damage imposed on sewer pipes and the AM-liner’s limit of serviceability during earthquakes was studied. This research has been split into three stages. The first stage was to numerically simulate earthquake-related damages imposed on sewer pipes. The second stage was to physically model the pipe’s performance and in Stage 3, Stage 1 and Stage 2 results were synthesised. Between ground oscillation and lateral spreading, the latter mode inflicted the most damage on sewer pipes therefore analysis was conducted on lateral spreading. In Stage 1, lateral displacement was modelled as frame-spring model using SAP2000 Pushover Analysis. Fourpoint bending tests were performed on two specimens of 150mm nominal bore vitrified clay pipe as part of Stage 2. The test was stopped after the displacement being applied by the actuator reached 268mm because the actuator arm could not be extended any further. The AM-liner at this point had partially collapsed but was not torn at any place. Based on this observation, it can be said that during an earthquake, AM-Liner can prevent influx of sand and water through broken pipes and the pipes can remain serviceable. As a result, restoration of damaged pipes can be delayed and attention can be provided to more important services or facilities. In Stage 3, the numerical models from Stage 1 were modified and calibrated using the properties determined during Stage 2. 8m and 16m lengths of 150mm diameter vitrified clay pipes were subjected to different amplitudes of lateral spreading. Segmented pipelines generally had the pipe and AM-liner failure at a lower lateral displacement than continuous pipelines. Continuous pipes on average had 67% more displacement capacity than segmented pipes. Pipelines subjected with constant profiled lateral spreading failed at a lower lateral displacement than pipelines subjected with triangular profiled lateral spreading. When the lengths of pipelines were compared, it was observed that AM-liners in longer pipelines maintain higher serviceability. 16m AM-lined segmented pipeline subjected with triangular profiled lateral spreading had the highest increase in tolerance to lateral displacement. For this scenario, the AM-liner increased the displacement capacity by 905% to 201mm.