Dynamic Characteristics And The Influencing Factors Of Liquid-filled Pipe Embedded In Saturated Soil Due To Seismic Waves

The damage of underground liquid-filled pipe under the action of earthquake greatly influenced city people’s normal life and enterprise production even may produce some secondary disasters. The seismic problem of the underground pipelines has become the focus of the engineering circle’s attention. Mitigation of earthquake disasters is a difficult problem faced by the public and experts. To carry out the research on the response characteristics of liquid-filled pipeline in saturated soil under seismic action has the certain practical significance in views of reducing the earthquake action on the pipeline engineering damage, ensuring the safety of lifeline engineering and avoiding the coinsurance of secondary disasters.Based on the research of seismic response of liquid-filled pipeline in saturated soil under seismic action, analytic method, numerical simulation and experimental research and reached the following conclusions:(1)The dynamic stress concentration problem of liquid-pipeline in saturated soil under seismic wave action was established by using the Biot theory of saturated soil and elastic medium wave theory. Through specific examples the convergence of the analytical solution were analyzed. By the means of comparing the calculation results with the related literature solution degradation method, the correctness of the solution method were verified.(2)By using the analytic method, the influence of engineering parameters such as pipeline thickness, pipe elastic modulus, and the depth of pipeline buried on the dynamic characteristics of pipeline under earthquake wave were analyzed. Research shows that shear modulus, pipeline thickness and buried depth of pipe have obvious influence on the dynamic characteristics. Along with the pipeline shear modulus decreases, the pipe thickness and the depth increase, the dynamic stress concentration coefficient will decrease. Along with the soil pores increase, the dynamic stress concentration coefficient will increase. The angle and frequency of incident wave and properties of the fluid in the pipeline will influence on the dynamic characteristics of pipeline. With the increasing of incident angle, the distribution also occurs at certain angle deflection. When the incident wave is perpendicular to the pipe, the peak value of pipe dynamic stress concentration coefficient around the periphery of the pipe is relatively large. And the Poisson’s ratio of pipeline has little effect on the dynamic stress distribution.(3)Seismic response of the liquid-filled pipeline in saturated soil was numerically simulated by using the computational software FLAC3D. The seismic response characteristics of flexible pipeline and rigid pipeline were comparatively analyzed. The vertical acceleration peak value, tangential stress peak value and pore water pressure peak value of rigid pipeline are greater than the flexible pipeline. The dynamic stress concentration factor distribution rules are as follows: the bottom is the maximum, the top is the minimum and both sides are secondary. The distribution trend is coinciding with the analytical method result.(4)The liquid-filled pipeline dynamic stress time history data under seismic conditions were tested by using experimental research. The dynamic stress distribution of fluid filled pipe and air pipe, flexible pipeline and rigid pipeline were comparatively analyzed. The test results show that the pipeline’s dynamic stress distribution rules are the bottom is the maximum, the top is the minimum and both sides is are secondary. The distribution difference is more obvious. The maximum and minimum ratio reached1.37-2.36. There is a great difference between the liquid filled pipe and empty pipeline’s dynamic stress distribution. Liquid filled with pipe’s dynamic stress is greater than the empty pipeline’s. Through the test, the dynamic stress of pipeline with different materials makes the elastic modulus parameter of the pipeline have sensitive affect to the dynamic stress values. PP-R building drainage flexible pipe’s dynamic strain is more than PVC-U drainage rigid pipe strain’s dynamic strain. While PP-R building drainage flexible pipe’s dynamic stress is less than PVC-U drainage rigid pipe strain’s dynamic stress. So in project, using the flexible pipe can reduce dynamic stress to some extent in the earthquake generated.