Dynamics and strain-based design of the large-diameter pipe under the impact of a falling rock

Abstract

Falling rocks are one of the essential causes to pipeline failures in the most frequently occurring geological disasters and the pipes in a thin-shell structure can hardly resist the huge impact energy. The traditional design are conducted by keeping the maximum stress smaller than the material strength which is too conservative to make a full use of the pipeline. In this work, codes for the explicit dynamics based on the Lagrange algorithm are adopted to numerically simulate the impact of falling spherical stones on the large diameter pipe with the consideration of nonlinearity of big deformation. Dynamic responses of the pipe as well as strains on pipe’s cross section are discussed in detail. Influences on the pipe strains from factors like impact speed, stone size and moving direction are investigated. Results show that, most significant effect is from the diameter-thickness ratio of the pipe and it shows the resistant capability of the pipe drops exponentially with the decreasing of the thickness and the ratio is recommended to be chosen in a range of 40∼60. Eccentricity also effects the strains exponentially and the impact extent is greatly reduced with the eccentricity being smaller than 50%. Safety check is carried out by an ultimate-strain criterion and so, the ultimate size and velocity of the falling stone are got. What is done in this paper is expected to be of referential values for geological disaster resistant design of pipeline.