Permeability and Stability of Base and Sub-base Materials

Since the advent of the automobile early in the twentieth century and the construction of modern roadways, engineers have recognized that asphalt and concrete roadways need adequate subsurface drainage (Oglesby and Hewes, 1963). Among the reasons cited for pavement failures, the inadequate drainage of pavement structures has been identified as a primary cause of pavement distress. Many of the modern roadway problems are associated with inadequate subsurface drainage. For a pavement, even a jointless asphalt pavement, surface water can penetrate and accumulate in the base and subbase. A high groundwater table and capillary rise of groundwater are other sources of subgrade moisture. The inadequate drainage of the accumulated water under the pavement causes mud pumping, adverse stress redistribution in the subgrade and lowers the shear strength of subgrade soils. Freezing action of a saturated base is also detrimental. This study determined the hydraulic conductivities, effective porosities and resilient moduli of several current and proposed drainable base materials. The materials studied were AASHTO No. 57, AASHTO No. 67, ODOT No. 304, ODOT No. 310, Iowa DOT No. 41-21 ('IA mix') and the 'New Jersey mix' studied by Baumgartner (1992).