Research on Effect Factors of Mechanical Response of Cross-Fault Buried Gas Pipeline Based on Fluid-Structure Interaction

Long-distance buried pipelines inescapably go through seismic fracture zones which makes the buried pipelines be easily influenced by the diastrophism. Most of the existing studies only focus on the two-phase contact between pipeline and soil, and the mechanical behavior of the cross-fault pipeline under transportation condition has not been studied. In this paper, ADINA finite element software was used to establish a pipe-soil-fluid three-phase coupling model based on fluid-structure interaction (FSI), and the effect factors of mechanical response of cross-fault buried gas pipeline were studied. Results indicate the following conclusions: (1) The model considering the effect of fluid-structure interaction can effectively simulate the mechanical response of pipelines in the actual working condition. (2) It is safer for the pipeline to pass through the strike-slip fault, and the most dangerous to pass through the reversed fault. (3) When the fault displacement is less than 1.3m, the optimal angle range to pass through the strike-slip fault is 30° to 60°, otherwise the optimal angle range is 30° to 45°; the optimal angle range to pass through the normal fault is 30° to 60°; the optimal angle to pass through the reversed fault is 90°. (4) When passing through the reversed fault, the optimal buried depth of pipeline is 1m-1.5m. (5) When the fault displacement is less than 1.3m, a certain delivery pressure (8MPa) can enhance the ability of pipeline to resist the strike-slip fault dislocation.

IV.—The Circular form of Mountain Chains

I am a stranger in the field of speculation, and am quite unacquainted with the intricacies of its authorized boundaries. It is therefore with some hesitation, lest I should tread upon forbidden ground, that I venture to offer a suggestion on one point in Professor Sollas's paper on “The Figure of the Earth.”It has long been observed that mountain ranges and chains of islands (which, indeed, are only mountain ranges partially submerged) are generally curvilinear in form, but Professor Sollas is, I believe, the first to show clearly that the curve often coincides almost exactly with an arc of a circle. Such a mountain chain is frequently defined along its convex margin by a great reversed fault over which the mountain mass has slid forward; and in these cases, at least, we may safely adopt Suess's conception, and look upon the chain as the crumpled edge of a ‘scale’ of the earth's crust which has been pushed forward over the part in front of it. The surface along which the movement has taken place is called a thrustplane. If this surface really is a plane, then the edge of the ‘scale’, that is the mountain chain itself, must necessarily be circular in form; for if any plane cuts a sphere, in any position whatever, the outcrop of the plane on the surface of the sphere will always be a circle. There can be no deviation from the circular form unless the ‘sphere’ is not truly spherical, or the ‘thrust-plane’ is not a true plane.