Impact Analysis About Surface Subsidence Of Gob Area On Overlying Oil And Gas Pipeline Deformation

With the rapid growth of China’s economy and the vigorous development of the petroleum industry, oil and gas pipeline transport has become the fifth largest transportation after the highway, railway, water transport and shipping.In recent years, oil and gas pipeline engineering was developed rapidly as an important national infrastructural engineering. Inevitably, pipeline engineering often takes place in the widely distributed coal gob area due to its special distribution characteristics.In this article, researches on the deformation of gob area were studied and mathematical modeling was used to analyze the impact of the deformation of gob area on overlying oil and gas pipeline. It is expected to provide some references for the oil and gas pipeline engineering crossing gob area in the future.This article mainly analyzed the impact of the gob area deformation on overlying oil and gas pipeline on the following aspects:1. According to the mechanism of the ground surface being impacted by the deformation of gob area, the impacting trends of horizontal god stratum on stress and displacement of overlying soil and gas pipeline in different depths was analyzed.2. The impacting trends of gob stratum in different inclinations on stress and displacement of overlying soil and gas pipeline in a certain depth.3. The impacting trends of gob stratum in a certain inclination on stress and displacement of overlying soil and gas pipeline in different depths.The finite element analyzing software ANSYS was mainly used during the process of analysis and calculation. After the analysis of the surface deformation and overlying oil and gas pipeline’s displacement and stress change, it was concluded that:1. With the increasing of the placing depth in horizontal gob stratum, the impact of deformation of gob area on the overlying oil and gas pipeline’s vertical displacement decreases gradually; the deformation of the horizontal gob stratum has small effect on the overlying oil and gas pipeline’s horizontal displacement; and the stress distribution caused by the deformation of horizontal stratum gob area is symmetrical distribution basically.2. In the stratum with the same inclination, as the increase of the placing depth of gob area, the oil and gas pipeline’s vertical displacement decreases gradually, but the impacting range increases obviously, and the displacement curve become gentle; In the stratum with the same inclination, the smaller is the placing depth, the larger is the oil and gas pipeline’s horizontal displacement, and the horizontal displacement points to the gob area’s inclination direction. As the location of gob area becomes deeper, the horizontal displacement becomes smaller, and the horizontal displacement curve becomes gentle relatively, the scope of influenced oil and gas pipeline increases; In the stratum with the same inclination, due to the deformation of the gob area, the stress distribution are similar, with the increase of placing depth, stress value increases gradually, and the maximum stress appears in the upper and lower edge of gob area, and in the downside direction, stress concentration is more apparent.3. In the same depth, with the increase of the inclination, the overlying oil and gas pipeline’s vertical displacement decreases gradually, but the variation trends are small relatively. In the same depth, with the increase of the inclination, the horizontal displacement of overlying oil and gas pipeline increases. However, when the inclination angle is relatively gentle (<30°), the increase of inclination angle make small influence on oil and gas pipeline’s horizontal displacement. But when the inclination angle further increases, the oil and gas pipeline’s horizontal displacement increases obviously. In the same depth, due to the deformation of gob area, the stress distribution change obviously. When the inclination angle increases, the maximum stress area move to the downside direction of gob area, and when the inclination angle becomes larger, the maximum stress area only appears in the bottom of the gob area.