Field Evaluation of Trench Backfilling Procedures: Interim Report

This study was originated in 1960 at the request of the Minnesota Local Road Research Board. Its basic objective is to determine a means of backfilling slit-type trenches so that little or no settlement results. In the first four years personnel from the Research Section, Office of Materials, Minnesota Highway Department, collected data by observing trench backfilling during regular construction operations and then measuring the subsequent settlements. In 1964, 1965, and 1966 dummy trenches were excavated and backfilled under more controlled conditions. This work was done by the City of St. Paul and Minnesota Highway Department maintenance forces. All testing was done by Research Section personnel.

In 1963, a progress report titled BACKFILLING TRENCH EXCAVATIONS was published by the Materials and Research Section, Minnesota Department of Highways. Included were general recommendations for street preparation, backfilling, and patching. Also, the effectiveness of various types of compactors was discussed and specific compaction procedures for given soils and traffic conditions were recommended. The results of the controlled backfill studies reported herein have confirmed certain of those recommendations for compaction procedures but have contradicted others. The investigation to date has not satisfied its objective and is being continued.