Mitigation of liquefaction-induced pipeline uplift using passive stabilization

Existing lifelines in seismic regions often suffer from liquefaction-induced uplift, which may cause intolerable straining to the buried pipes thus threatening their integrity. Backfill excavation and refilling with proper aggregate is the most common yet costly liquefaction mitigation technique. A novel mitigation technique, that avoids excavations, is the low-pressure injection of a colloidal silica stabilizer in the vicinity of the pipe. This paper performs a numerical investigation of the effectiveness of this technique for the case of a buried steel pipe. The investigation is performed with FLAC and initiates by model verification against a dynamic centrifuge experiment where the pipe uplifts due to liquefaction of the surrounding sand. The paper explores different stabilization geometries with respect to the pipe (over it, under it, at its sides, etc.) thus establishing the most efficient stabilization scheme that reduces the uplift displacement at the minimum cost, for different pipe diameters and embedment depths.