A series of loading tests on buried flexible pipes has been carried out to validate a new design method. This method provides a unified basis for assessing the interaction between deflections, buckling and yield of the pipe wall, so that charts of direct application to design can be produced. A series of both metal and plastics pipes was buried in either sand or sandy clay and the pipe responses to applied surface loading monitored. The stresses induced by the applied loading were investigated using control tests with no pipe present, and the effect of the TRRL test pit dimensions was assessed using finite element modelling. The results of the pipe loading tests showed that failure could occur either by excessive deflection or by buckling. Comparisons with design chart predictions showed that the test results generally conformed to the model of soil/pipe behaviour which has been adopted. The implication of the results upon the recommended design procedure is discussed and the importance of using back-calculated values of soil modulus demonstrated. The recent development of a simplified deflection-buckling chart embracing a range of loading situations is described. (A)

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