EFFECT OF SHEAR COUPLING ON THE AXISYMMETRIC WAVE MOTION FOR BURIED FLUID-FILLED PIPES

摘要

This paper is concerned with the effects of shear coupling at the pipe/soil interface on the axisymmetric wave motions for buried fluid-filled pipes. Two extreme cases are of particular interest: the "slip" condition representing lubricated contact; and the "no slip" condition representing compact contact. Dispersion relations for the n=0 axisymmetric waves are given by accounting for the fully three-dimensional effects of the surrounding soil, from which low-frequency analytical solutions to the fluid-borne s=1 wavenumber can be determined. Theoretical predictions are presented for a test MDPE water pipe buried in sandy soil for the s=1 wavenumber measurements. It is shown that the predominant effect of shear coupling at the pipe/soil interface is to add stiffness in contrast with mass loading when the shear coupling is neglected, and damping due to radiation. Comparing the two coupling cases, it is found that the real part of the wavenumber for compact contact is slightly lower than that for lubricated contact, as expected, due to the additional lateral constraint on the pipe wall. Nevertheless, the stiffness effect on the wavespeed is relatively small for both coupling cases compared with the compliance effect of the shell wall. For this particular type of soil, the attenuation for the compact coupling case is greater than for the lubricated contact case. Experimental measurements show good agreement with the predictions, and indicate that: as anticipated, for the measurement pipe, the coupling between the pipe and the soil falls between the two extremes considered.