Trench Effects on Blast‐Induced Pipeline Stresses

An experimental program was conducted to obtain data from model tests to evaluate the effects of open trenches on blast‐induced circumferential and longitudinal stresses on an underground pipeline. A model pipe was instrumented with five sets of orthogonal strain gages at two longitudinal locations. Five sets of experiments were performed. The first set of experiments, in which the blast‐induced stresses covered the range of a stress‐predictive equation derived previously, consisted of tests without a trench. Similar blasting tests were then conducted using four different trench geometries. The trenches were all the same width and located the same distance from the model pipe. Two different lengths and depths were used on the four trenches/The measured strains and ground motions from the no‐trench experiments showed that the new data compared very well with values obtained using the predictive equations developed on a previous program. In general, the trenches were more effective in reducing the circumferential pipe stresses than the longitudinal pipe stresses. However, different depths and lengths of the trench affected the pipe stress amplitude variations. The longer and deeper trench was the most effective.