The state of practice of in situ tests for design, quality control and quality assurance of ground improvement works

In the state-of-the-art report that was published on ground improvement processes at the 17th ISSMGE conference, ground improvement was defined in five categories. This paper has focused on the ground improvement techniques that either mechanically stabilize the soil or incorporate admixtures or inclusions and the most common in situ geotechnical tests that are used during the geotechnical investigation, quality control and quality assurance phases of these techniques. In addition to the suitability and feasibility of the technique itself, the level of success of any ground improvement program is also related to the applicability and suitability of the criteria that is to be satisfied and the testing campaign that is to be undertaken to verify the works. Experience of the authors indicates that the optimal approach is when acceptance is based on the project's actual geotechnical requirements rather than on minimum test results. At the same time, ground improvement design parameters can only be properly determined when the ground conditions are correctly comprehended, which is possible through meaningful geotechnical investigation. Similarly, applied treatment can only be confidently verified when testing is able to well relate to acceptance criteria. Hence, tests that are able to predict the acceptance criteria without reliance on experimental correlations and published work from other sites will result in the best engineering practice and confidence in results.