A unified compaction curve for raw earth material based on both static and dynamic compaction tests

Abstract

This paper investigates the compaction characteristics of raw earth via a double-faced static compaction and the traditional Proctor test (dynamic process). The corresponding compaction energies are estimated for each individual sample, while the matric suctions are measured by a simple method using filter papers. The obtained results allow to draw the following observations and conclusions. Firstly, similar to classic Proctor tests, a family of iso-energy curves (i.e. tests with identical compaction energy) are identified for the set of static compaction tests. With increasing compaction energy, the iso-energy curve shifts leftwards and upwards, leading to a reduction of optimum moisture content and an increase of maximum dry density. Secondly, a new term called the optimum saturation degree (Sr)opt is introduced, defined as the degree of saturation Sr where (ρd)max is obtained for a given value of compaction energy and for a particular compaction method. For a specific earth type, and a given compaction energy, our experimental results indicate this (Sr)opt value is constant and that, a unique compression curve linking the degree of compaction Dc = ρd/(ρd)max to Sr−(Sr)opt exists regardless of the compaction method (static compaction, dynamic Proctor etc.) and compaction energy. Thirdly, the matric suction of specimen subject to static compaction tests is slightly higher than that in dynamic Proctor tests at the same moisture content, whereas the dry density has hardly any correlation with the variation of matric suction. Finally, a new method of earth compaction control is proposed here. This new protocol is organized to compact the earth to a target dry density ρd, by taking advantage of practically achievable compaction energies and meeting the design requirement, while keeping the Sr = (Sr)opt condition.