# Investigation of Earthquake-Induced Pipe Damage in Liquefiable Soils  
Munire Dulger  
Department of Civil Engineering, Yilduz Technical University, Istanbul 34220, Turkiye; [EMAIL_ADDRESS]  
has been fluidized whose unit weight is equivalent to its saturated unit weight [6; 7]. It should be noted that the buoyancy force is also estimated in terms of the excess pore water pressure [8]. The safety factor against flotation proposed by [PERSON] [9] has been developed and verified through centrifuge tests for both pipes [10] and manholes [11]. The specified safety factor procedures only indicate the uplift triggering condition and do not accurately predict the final uplift displacements of underground structures [11]. Numerical analyses have been carried out to investigate the dynamic responses of soil and pipes up to the liquefaction stage [12]. In the past fifteen years, the behavior of underground structures (tunnels and pipes) under dynamic conditions has been investigated through numerical analyses [2; 13; 14; 15; 16; 17; 18; 19; 20] and physical model experiments [3; 4; 21; 22]. [PERSON] and [PERSON] [13] have conducted a numerical study using 2D finite difference software FLAC (2008) to investigate the effects of tunnel uplift due to soil liquefaction, evaluating pore pressure variations during earthquakes, considering tunnel diameters, burial depths, and soil stiffness and strength parameters. Based on a series of model experiments, [PERSON] [9] has identified three main reasons for the uplift of underground structures exposed to liquefaction: lateral deformation of the soil beneath the structure, followed by the movement of pore water towards the base of the structure, and finally the reconsolidation of the liquefied soil. Numerical and experimental studies have been conducted to understand better the uplift response of underground structures with circular cross-sections buried in homogeneous liquefiable soil [22]. In these analyses, the deformation patterns occurring in the ground surrounding the structure are similar to those observed by [PERSON] [9]. [PERSON] [22] found in numerical analyses concerning the performance of underground sewer pipes near Tokyo in Urayasu City following the 2011 Great East Japan Earthquake that significant pipe uplift displacements occurred in liquefiable soil, which was consistent with observed pipe damage in the field. [PERSON] [23] have conducted numerical analyses to investigate the uplift of an underground pipe structure due to liquefaction. The liquefiable soil has been modeled using the elastic, perfectly plastic Mohr-Coulomb model, incorporating [PERSON]'s pore water pressure formula. In the study by [PERSON] [24], the uplift of shallow buried pipelines subjected to seismic vibrations in liquefied areas has been investigated using dynamic centrifuge tests. [PERSON] et al. [25] used the Finn Model with the FLAC2D software to study the uplift behavior for Nevada sand parameters at different relative densities, various diameters, and burial depths. It was shown for the various depths that the amount of uplift increases as the diameter ratio increases, and decreases as the relative density and burial depth increase. Damage occurring on critical pipelines during an earthquake can potentially lead to delays in critical services, infrastructure disruptions, explosions, structural collapses, environmental pollution, and economic losses. The safe operation of natural gas pipelines is of great importance in meeting the energy demands of modern societies, but geological hazards pose significant challenges to their integrity  
Most seismic disaster studies have shown that the likelihood of damage to buried pipes in liquefied soil is higher than in non-liquefied soil [26; 27]. In liquefied sands, shallowly buried pipes may exhibit bending deformation, creating an upward buoyancy behavior, which increases the degree of damage. During the 1964 Niigata earthquake, 68% of a 470 km-long pipeline was destroyed. Most of the deformations observed were due to pipe uplifting behavior.