# Investigation of Earthquake-Induced Pipe Damage in Liquefiable Soils
## 4 Evaluation of Pipeline Damage Caused by Earthquake in the Iskenderun Region
### Discussion of Results with Numerical Analysis with 3116 Station Data for Study Area 1  
In Study Area 1, the seismic performance of the \(\O\) 1500 mm pipeline between the treatment plant and Isdemir steel plant was evaluated, taking into account the repair works carried out as described in the DSI (State Hydraulic Works) assessment report [59]. After the earthquake, HATSU (Hatay Water Authority) recommissioned the treatment plant, declaring that the existing pipes did not sustain any damage [57]. Study Area 1 is located near the Sarseki neighborhood (Figure 2), and based on results of the microzonation study, the seismic shear wave velocity Vs30 is higher in that area (Figure 13c), suggesting that the bedrock is closer to the surface. Therefore, the seismic record of station 3116 was used. The coordinates of station 3116 are (36.61618 and 36.20661), and its elevation is 33 m. The epicentral distance is calculated as 105.38 km. Analyses were repeated using the record from station 3116 in the soil profile of Study Area 1. In the record from station 3116, PGA is 160.8 cm/s\({}^{2}\), and the shear wave velocity is Vs30 = 870 m/s. Therefore, a 1 m thick bedrock layer was defined at the base instead of residual soil. Material parameters (linear elastic, \(\gamma_{\text{unsat}}\) = 24 kN/m\({}^{3}\), E = 250 \(\times\) 10\({}^{-3}\) kN/m\({}^{2}\), \(\gamma\) = 0.25) for the rock layer used in the numerical analysis for Study Area 1 were utilized. The input data were applied from rock layers located at 40 m at the base of the analysis model, and analyses were conducted employing a model width of 50 m (Figure 15). In the finite element mesh of the 50 m long model, 6236 triangular elements with 15 nodes each were used. The average element size in the model was 0.858 m, and seismic data were applied in the analysis at equal intervals of 0.01 s up to 95.7 s. Since there was rock at the model's base, the boundary conditions were selected as a compliant base, and free-field boundaries were used at the lateral boundaries. Since the input seismic data were applied from rock, the 'Compliant base' option was selected, and a prescribed displacement of 0.5 m magnitude was applied along the \(x\)-direction across the base of the model in the numerical analysis. The \(y\)-component of the strong ground motion was selected as fixed (Figure 15). Figure 18: Excess pore pressure ratio (Ru) of soil layers at the end of the earthquake with DN \(\O\) 2000 mm pipe, 120 m width model. Considering that the seismic acceleration is exerted from rock, the peak ground acceleration (PGA) is 160.8 cm/s\({}^{2}\), and settlements are small (0), the model width was selected as 50 m, assuming that the pipe was not significantly affected by the boundary conditions. Expanding the model boundaries extends the duration of the analysis. Using a seismic record obtained from bedrock at station 3116, the behavior of a \(\OO\) 1500 mm diameter pipe was analyzed at different burial depths (H/D = 1, H/D = 1.2, H/D = 1.5). According to the analysis results, the uplift of the \(\OO\) 1500 mm pipe decreases as the burial ratio (H/D), i.e., burial depth, increases. For the burial ratio of H = 1D, the calculated uplift is 0.075 m, while for the H = 1.5D scenario, the uplift is calculated as 0.035 m (Figures 19c and 20). The variation in vertical displacements is shown in Figure 20. The analysis results (Figure 19b) indicate liquefaction in the soil due to the increase in excess pore water pressure ratio, \(\text{Ru}=1\). However, the excess pore water pressures resulting from the proximity of the bedrock to the surface and the thickness of the liquefiable soil layer have been insufficient for the pipe to undergo displacements significant enough to cause rupture. In the Azyganhk region, the shear wave velocity Vs30 values are higher and they fall within the green zone in Figure 13c, representing a range of values between 400 m/s and 550 m/s.