A Mesocosm-Based Approach for Assessing in-situ Performance of Stabilized Geomaterials

Abstract Several common ground improvement methods, including deep mixing and stabilization and solidification, utilize cement or other pozzolanic additives to enhance the strength and workability of initially unsuitable geomaterials. Ground improvement methods are often determined using a laboratory treatability study with laboratory cured samples. However, samples created in the laboratory often differ from material in the field due to differences in placement, curing, and testing conditions. This paper presents the implementation of a mesocosm-based approach which aims to better mimic field conditions for design and QA/QC of stabilized geomaterials. The mesocosm method was evaluated using a dredged fine-grained sediment stabilized with 4% Type 1L Portland cement by wet mass. Shelby tube samples were extracted from the constructed mesocosms after different curing durations, and their performance was assessed using unconfined compressive strength (UCS) tests. The mesocosm samples were compared with samples that were created following typical treatability study approaches and cured under the same ambient conditions as the mesocosms. Results after the first four weeks of curing showed that the mesocosm samples had a lower UCS compared with samples created following the traditional approaches. Additionally, differences in the ambient temperature during curing corresponded with differences in the achieved performance between mesocosms. Finally, dynamic cone penetrometer tests were used to evaluate the performance in-situ and were able to capture the increase in strength over time as well as the variability between the different mesocosm replicates. The practical impacts and future research needs are discussed.