01025017

Component

The depth of ground water table (GWT) has a profound effect on the performance of pavements. A rise in GWT depth influences the moisture content of the unbound materials and subgrade soils, thereby reducing their strength. The reduced stiffness in unbound materials and subgrade layers contributes to various pavement distresses. GWT depth is a key input parameter in both the 2002 design guide and EICM software. A sensitivity analysis was conducted to study the effects of water table depth on pavement performance, as predicted by the new NCHRP 1-37 software. This paper evaluates the influence of water table depth on performance parameters for six different types of soils. The performance parameters considered in this analysis are top-down cracking, bottom-up cracking and rutting. In this study, two typical pavement structures were analyzed using the NCHRP 1-37 software for a 20 year design period. The results show that the GWT depth parameter affects the pavement performance predictions. As water table increases, predicted top-down cracking at the surface decreases, whereas the fatigue cracking at the bottom of the asphalt concrete layer increases. The level of water table has no significant effect on the rutting accumulated on the asphalt concrete layer. The subgrade rutting is greatly influenced by the depth of ground water table and the predicted rutting exhibits different trends for silty and clayey soils. The predictions of subgrade rutting were compared with the Ayres model for permanent deformation of unbound materials. The analysis indicates that the proposed 2002 design guide software under predicts the subgrade rutting for silty soils when the ground water table is less than 10 feet. These results also highlight the importance of appropriately characterizing the GWT parameter for highway agencies planning to use the 1-37 software.

01020180

06-2162

English

12p

2006

Transportation Research Board 85th Annual Meeting

CD-ROM

Figures (5) ; References (6) ; Tables (11)

Groundwater; Pavement cracking; Pavement design; Pavement performance; Rutting; Software; Subgrade (Pavements); Water table

Design; Highways; Hydraulics and Hydrology; Pavements; I22: Design of Pavements, Railways and Guideways

Transportation Research Board Annual Meeting 2006 Paper #06-2162

BTRIS, TRIS, TRB

Mar 3 2006 10:54AM