Effectiveness of Anti-Liquefaction Techniques for Buried Pipelines

In this paper, effectiveness of several existing anti-liquefaction methods for preventing large deformations of pipelines for lateral flow of liquefied grounds during earthquakes are investigated and compared, as well as a proposed method which fixes pipelines with expansion joints parallel to auxiliary continuous pipes using iron tie-plates. Stiffness of liquefied soils around pipes is represented as a static coefficient of subgrade reaction, based on the experiments on the interaction between liquefied sand deposits and pipes. Pipeline-spring systems which are characterized by those coefficients are analyzed based on the theory of “a beam on an elastic foundation” and transfer matrix method. Computations are performed with respect to the key parameters of pipes, coefficient of subgrade reaction, and several fixing conditions between pipes and underground structures. The sliding displacements of pipelines, rotational angles of joints, and stresses of pipelines are compared for such anti-liquefaction methods as soil-improving methods (sand-compaction pile or ballast-replaced soil methods) and structural-stiffening methods (parallel pipe or pile-supporting methods).