On the Moisture Condition of Highway Subgrade

Abstract

We cannot design a reliable highway pavement without knowledge of the moisture condition of the paved subgrade because the bearing capacity of subgrade changes much with the moisture condition. Generally, although the moisture condition of bare ground changes much following a change of weather, after the groung is paved, it does not change so much, and is in a limited range. To know exactly the moisture condition of the subgrade before and after the subgrade is paved, the author investigated the negative pore water pressure in bare and paved ground, and made clear the features of the moisture condition of a typical subgrade. Then the author proposed a new method estimating for the moisture condition of subgrade and an expedient method for estimating the possible wettest moisture condition. As the values estimated by these methods were nearly equal to the measured values, these methods were considered to be usable for designing highway. Especially, the expedient method seemed to be convenient for designing a reliable highway pavement in a rainy country like Japan.