INDUCED-TRENCH METHOD OF CULVERT INSTALLATION

The induced-trench (imperfect-trench) method of culvert installation is used to reduce the loads on a culvert under a high fill. Although the method has been used successfully with concrete pipe under some unusually high fills, the magnitude of the reduction in load achieved by the induced trench has not been clearly established. This research project was initiated to evaluate the settlement ratio and to compare the measured loads acting on the culvert with theoretical values. The results of this research indicate that the range of empirical values that have been recommended for the settlement ratio for the induced trench is reasonable for a 48-in. reinforced concrete-pipe culvert under 30 ft of fill. A comparison of the measured loads acting on the culvert with theoretical loads indicates that the load theory is somewhat conservative.