Railroad Ballast Density Measurement
Because existing methods were unsuitable for measuring the in-situ density of railroad ballast, studies were conducted to develop a new technique. A laboratory investigation was made of the various factors affecting the measurement of density in railroad ballast, which typically is composed of open-graded and coarse-grained aggregates. An approach employing water replacement in a lined hole was selected for extensive evaluation. Based on the laboratory results, a new apparatus has been devised and test procedures have been developed which subsequently have been successfully applied in the field at various railroad sites. This paper summarizes the research involved in the development of the density-measurement method. The details of the apparatus and procedures are provided in appendixes to the paper. The field tests confirmed the suitability of the method and provided new information on the physical state of ballast. The proposed new method is not limited to use with ballast but is also applicable to most other soil and aggregate materials.