Analysis For Seismic Isolation Pipelines Across Fault

As one of the most important transport means, especially oil-gas-water pipelines being called lifelines,pipelines are widely used all over the world and their working are important to maintaining common safety and wealth. Though faulting is one main reason of buried pipelines damage, so far no reliable and effective measures are developed for pipelines to cross the fault. In this background, this paper proposes one measure for this purpose. Buried pipeline comes out of the ground near the fault with supports being installed under the pipeline and the blocks at the bottom of the supports can slip on the ground, so seismic isolation pipe segment is formed. This paper mainly involves earthquake response digital simulation and engineering design of seismic isolation pipelines across the fault.In chapter 1, the background and meanings of this thesis are pointed out and the research status and main earthquake resistant measures of buried pipelines across fault are reviewed. The problems to be solved in the future are emphasized here too.In chapter 2, two theoretical methods and two simplified methods are reviewed. Newmark-Hall method is the approximate method to give the minimum tensile strain of the buried pipelines across the fault, while Kennedy method gives the maximum one. Takada's simplified formula calculates the length of the start-bending point to the fault according to Kennedy's method and the soil constraint is not considered in his finite element model. Liu Ai-wen's simplified formula is the normalization result of the digital simulation examples and the model of buried pipe across the fault is established based on his"equivalent spring"method. While reviewing the main earthquake resistant measures'advantages and disadvantages of the pipe across fault, the writer proposes one measure for the same purpose. The rationality of the theory, the feasibility of the technique and the economy, and the reliability of the measure and the digital simulation are discussed.In chapter 3, the physical model of the seismic isolation pipe across the fault is established and the fundamental theories and detailed methods are introduced. They include dealing with the non-linearity,the analysis methods of structural response with multi-inputs,the choosing of the finite element,the type of the fault, the displacement of the fault, the ground motion records near the fault and so on. In chapter 4, the influence of different factors, on the earthquake response and the seismic isolation effect, are discussed with the factors being validated, analyzed and explained. The content includes: (1) the influence of the interaction between the pipe ends and their surrounding soil on the seismic isolation effect of the pipe segment across the fault; (2) the influence of the space between supports on the seismic isolation effect of the pipe across the fault; (3) the influence of the fault displacement on the seismic isolation effect of the pipe across the fault; (4) the earthquake response difference between seismic isolation straight pipe segment and the pipe segment with end elbows; (5) the influence of the friction coefficient between the slip block and the soil surface on the seismic isolation effect of the pipe across the fault; (6) the influence of the seismic isolation pipe segment length and the angel between the pipeline and the fault line on the seismic isolation effect of the pipe across the fault; (7) the difference between the earthquake responses of dynamic analysis and static analysis for the seismic isolation pipe segment; (8) the seismic isolation effect analysis for the pipe segment under strike slip faulting containing normal(reverse) fault component.In chapter 5, the engineering design procedure and demands are proposed for the seismic isolation pipelines across the fault(establishing the model, considering the ground motion input, analysis method and procedure, checking criteria and so on). By the way of FEM, the part maximal tensile strain and maximal compressive strain of 210 meters long pipe segment with three kinds of diameter and three kinds of thickness, under three kinds of ground earthquake motion records. The earthquake resistant ability of seismic isolation pipe segment is evaluated by comparing their maximal strain with corresponding permission strain. In the same time, the strain of seismic isolation pipe segment is compared with the strain of buried pipe across the fault. Finally the engineering design suggestion of three commonly used diameter pipe segments is given through changing their length and the friction coefficient between the slip block and the soil surface.In chapter 6, after summarizing the whole research work, the research work in the future is suggested.