The ground movement caused by the consolidation of soil or surface loading changes the state of stress in the ground adjacent conduits. Under these circumstances the conduits may be subjected to very high ground forces which can lead to conduit failure.
The purpose of this paper is to present a method of estimating the ultimate earth pressure on the conduits, which is based on the limit analysis and equilibrium equations. The analysis presented is similar in principle to that employed by Matsuo (1964), but it is also extended to conduit groups which are placed in parallel. The failure model of soil mass used in the present analysis is produced by analysing photographs to show movements of sand particles around the conduits during model tests. Furthermore, on the assumption that the Mohr-Coulomb's failure criterion is valid on shear sliding line, the failure model is shaped by a logarithmic spiral.
In this paper, comparisons are also made between observations on the ultimate earth pressure acting on the model conduits set in the dry sand and a mass of aluminum rods and those predicted by the proposed theory, and it is found that the proposed theory can predict the test results fairly well.