Tolerable Movement Criteria of Shallow Bridge Foundations in Cohesionless Soils

摘要

Settlement of structures built on soils is a subject of considerable interest to practicing engineers since excessive settlement is one of the most important problems in soil mechanics and can lead to serviceability problems or even failure states in the structure's foundations. Even though immediate settlement calculation is an important step in evaluating the usage of shallow foundations in cohesionless soils for bridge foundations, differential settlement, and angular distortion are the most effective parameters for the evaluation of bridge foundations. In this paper, the performance of six settlement prediction methods for spread footing foundations is verified by using compiled field data from research projects. Vertical settlements were measured on 20 footings (yielding 10 measurements of differential settlement) from seven bridges in the Northeast U.S. and one bridge in Ohio. The settlement prediction methods selected for settlement calculations for the spread footings on cohesionless soils for each footing site are compared with measured settlement values. The standard penetration test (SPT) is considered in this study for the selected settlement prediction methods. Statistical parameters corresponding to each of the six settlement prediction methods for both differential settlement and angular distortion are evaluated and summarized. The study shows considerable differences in accuracies for the six selected prediction methods. It can be concluded that two prediction methods showed better results than the others. In addition, the distributions of differential settlement for the two selected prediction methods for shallow bridge foundations are examined.