PSI - Issue 30

A.A. Antonov et al. / Procedia Structural Integrity 30 (2020) 11–16 A.A. Antonov et al. / Structural Integrity Procedia 00 (2020) 000–000

13

3

The actual depth of the pipeline axis was measured with a probe at 2-3 arbitrary control points in the inspected area to check the accuracy of the measurements performed by the line locator. Based on the survey results, graphs were constructed according to the Baltic system of heights, where the surface relief of the earth and the main gas pipeline are marked. A section of the line-I of the underwater gas pipeline on Uluu Aryy island from the side of Hatassy village is taken as an example. According to the data obtained, the average depth of the underwater gas pipeline at the site of Uluu Aryy island is 2 m (see Fig. 1), and it is 2.5 m at the Byldjahyktaah island. The smallest depth is 0.9 m from the land surface at a distance of 2489,91 m from the Hatasskaya channel. Moreover, particularly dangerous denuded sections of the underwater gas pipeline were detected at distances of 1592.28 m and 2798.56 m. On the right bank at the intersection of the channel (coordinates 61  51 ′ 39.28 ″ C; 129  47 ′ 51.34 ″ B) the pipelines lie 0.30 m high from the earth surface, which is dangerous in case of bed movement in spring. Owing to the weak water-saturated soils in the section of the underwater gas pipeline, located 1,592.28 m from the Hatasskaya channel, a 2.3-meter-long gas pipeline was denuded. The lower part of the pipe lies at the bottom of the stream, creating an artificial dam. In this case, one side of the pipeline lies on the water level. The other is 15 cm above the water level. In this section, the gas pipeline is bent along the longitudinal axis as a result of sagging and seasonal “loosening” (pipe blowing) of the gas pipeline (see Fig. 2). The length of the scoured section, which is 2,798.56 m far from the Hatasskaya channel, is 10 m. The pipeline sagging is up to 25 cm from the level of the ice surface. Swelling of the longitudinal axis of the pipeline is also observed at this site. The planned-high-altitude position of the gas pipeline in this section is demonstrated on Fig. 3.

Fig. 1. Section of the I-line of the underwater crossing of MGL on Uluu Aryy island, Hatassy village.