Construction and performance evaluation of large stone subbase (LSSB) layers

The most appropriate way to evaluate the engineering properties of large stones is to perform field testing on fullscale pavement systems built with large stone subbase (LSSB) layers because such properties of large stones cannot easily be measured in the laboratory. Although there have been several studies discussing the use of large stones in pavement systems, there is still limited knowledge about appropriate thicknesses, use with geosynthetics and/or with recycled aggregates, and long-term performance of LSSB layers. In this study, several test cells were constructed with LSSB layers with different thicknesses. The cells contained different recycled aggregate base (RAB) layers, and some of the cells contained geosynthetics beneath the LSSB layers. Nuclear density tests and intelligent compaction were performed during construction. A series of falling weight deflectometer (FWD) tests were performed during and after construction. One of the cells contained thermocouples embedded at different depths for soil temperature monitoring. This study showed that the use of geosynthetics was essential for constructing LSSB layers that are not thick enough, and staged construction was not convenient for large stones. In addition, the cells constructed using the thicker LSSB layers provided greater performance. In the short term and the long term, the cells containing the thicker LSSB layers yielded around 2.6 and 1.5 times higher modulus values, respectively.