Evaluation of causes of excessive settlements of pavements behind bridge abutments and their remedies Phase II (FHWA-OK-89-06) 2148

To evaluate the causes of bridge approach settlement a survey of 758 bridge approaches in seventy-seven counties of Oklahoma was conducted. In this survey, data related to the following items were collected: ( i) bridge, abutment, approach, and slope protection structure, (ii) embankment material. Information related to the construction and maintenance for these approaches was collected by interviewing ODOT personnel and searching records maintained at ODOT. The analyses of data show that the settlement problem is extensive in Oklahoma, namely, 83% of the approaches surveyed experienced settlement. It was observed that on the basis of long term performance rigid and flexible approaches are similar, but on a short term basis, rigid approaches experience lower differential settlement. Pile supported abutments as compared to stub type and high embankments with no drainage for the fills appear to be conducive to larger settlements. In general, skewed appreaches have a higher settlement than nonskewed approaches. Regression techniques were used to develop an empirical relationship between the approach settlement and the causative parameters such as age of the approach, embankment height, traffic volume, and skewness of the approach. As a preliminary work for the next phase of the study, soil samples were collected from two sites. Comprehensive laboratory testing was conducted with the purpose of determining their site-specific embankment and foundation soil characteristics which may be used in a settlement prediction model.N