[BUCH][B] Roadway Performance in an Expansive Clay

RF Reed - 1987 - trid.trb.org
RF Reed
1987trid.trb.org
The performance of three pavement designs with expansive clay subgrade is presented.
The pavements have been subjected to extensive warping attributed to differential swelling
of the underlying soil. The purpose of this paper is to evaluate the effectiveness of the three
designs in reducing warping, and to provide suggested alternative designs. The study
focuses on pavements west of Dallas, Texas, situated over weathered shale of the Eagle
Ford geologic formation. The weathered shale is highly expansive with heaving in excess of …
The performance of three pavement designs with expansive clay subgrade is presented. The pavements have been subjected to extensive warping attributed to differential swelling of the underlying soil. The purpose of this paper is to evaluate the effectiveness of the three designs in reducing warping, and to provide suggested alternative designs. The study focuses on pavements west of Dallas, Texas, situated over weathered shale of the Eagle Ford geologic formation. The weathered shale is highly expansive with heaving in excess of 12 in. being recorded. Postconstruction heave is attributed to increase in the soil moisture regime over time. Pavement warp occurs primarily in deep cut areas where the finished grade lies near or below the original zone at which soil moisture was stable and was not influenced by seasonal fluctuations. Data indicate that the overall movement of the pavements studied was upward. Differential vertical movements caused warping. The differential movement is attributed to the influence of:(a) underground utilities;(b) micro and macro soil structure features;(c) drainage;(d) patterns of water migration; and (e) stress release. The study evaluates the performance of three specific pavements. Subgrade treatments used to minimize potential movements included removal and replacement with lime stabilized soils and inert fills, and maintaining positive drainage. Alternative subgrade treatment by preswelling is discussed. Modification of pavement shoulders and base to account for shrinkage and loss of bearing support is a necessary component of preswelling design. Preswelling and suggested base and shoulder modifications are compared to current design techniques used in the area on an economical basis.
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