关键词: 地震断层, 埋地管道, 抗震设计

Abstract: This paper reviews the most popular studies since 1975 on the responses of buried pipeline to earthquake faulting. Among the analysis methods based on beam model, Newmark-Hall's model and Kennedy's model are most representative. Newmark-Hall's model is commonly accepted in engineering fields and adopted in China (SYJ8401-91,1991) and USA (Guidelines for Seismic Design of Oil and Gas Pipeline System, 1984) for its simplicity. Kennedy's model is relatively more precise and closer to the reality. As compared to the second model, the first model gains smaller calculating result due to the neglecting of transverse forces of the soil and bending deformation of the pipe. On the other hand, the result of the second model is conservative due to overestimating the elongation of the pipe. Recently, Wang Ruliang et al. proposed two representative numerical methods that were used to compute the deformation and internal forces of the pipes and to gain more realistic results. On the basis of previous work, a new analytical method of buried pipelines based on beam theory is proposed in this paper. The major characteristics of this method are: 1) The deformation model takes the form of elastic base beam in the far end and cantilever beam at the end closer to the fault (e.g. Wang Ru-Liang's method); 2) Ramberg-Osgood stress-strain model, which describes the pipe more realistic than the formerly used stress-strain model, is used and nonlinear feature of the pipe is considered; 3) Simplify the complex steps of determining whether the material yields in Wang Ru-Liang method of 1998 when calculating axial elongation of the pipe;4) The adoption of stress-strain model for large deformation improves the precision in the case of faulting with large deformation; 5) The influences of bending rigidity and extension rigidity are considered simultaneously so that the analytical formula of internal forces and deformation in any sections can be obtained. Some improvements have been made in our model on the basis of the previous work, which makes the result more reasonable, especially for analysis of the internal forces and deformation on the segments of large deformation. This paper also discusses the problem of concern to the researchers and engineers. That is, whether or not a physical parameter can be found to determine the strain of pipeline is mainly axial or bending? This problem is tentatively studied in this paper and a dimensionless physical parameter α is found. If α<1.2, then the strain of pipeline is mainly bending. In this case, however, the results obtained by using Newmark's method as recommended by the regulation are smaller, and will not satisfy the precision. If α>1.2, then the strain of pipeline is mainly axial extension, and the precision of Newmark's method in this case is satisfactory. When the pipe is deformed extensionally by faulting, it is suitable to take β between 50° and 80°. When the pipe is deformed compressionally by faultingt β is better to be close to 90°.

Key words: Strong earthquake faulting, Buried pipeline, Anti-seismic design