Abstract:

In order to research the evaluation index of differential settlement, the finite element code was used to study the influence of settlement gradient on the additional stress of the base. Then the analytic solution of tensile stress at the bottom of semi-rigid base was obtained basing on the two layer of elastic continuous system, and the maclaurin expansion was adopted to simplify the analytic solution. Results showed that there were great limitations for using the settlement gradient to evaluate the allowable uneven settlement. But the first derivative settlement gradient, which was the ratio of settlement gradient to spread distance, had a well linear correspondence to the tensile stress. Therefore, the first derivative settlement gradient could be used as the key index to assess the allowable subgrade uneven settlement. For the typical semi-rigid base asphalt pavement structure, the allowable first derivative settlement gradient was 0.000161m-1, when the traffic loading was not considered.

Key words: subgrade uneven settlement, evaluation index, settlement gradient, spread distance, first derivative settlement gradient