New methodology for testing very coarse soils by “liquid plate loading”

Introduction. At present, the plate load testing is considered to be the most effective method for determining the deformation parameters of very coarse soils. However, the major challenge associated with such tests is the low accuracy of the results due to the inability to properly clean the borehole bottom.Aim. To develop a new methodology for plate load testing using an intermediate layer of a liquid, quick-setting material to ensure uniform load transfer to the very coarse soil.Materials and methods. The author conducted a number of laboratory and site investigations in order to select contact layer material, which meets requirements for plasticity, temperature, strengthening and setting time. Following that, the author recommended a liquid quick-setting composite material MasterFlow 928 for application. The study involved development of a technology for the material delivery to the borehole bottom and gathering data on the minimum required thickness of a contact layer depending on particle size of the tested soils. The methodology of using quick-setting composite materials was tested at three sites in different soil conditions and at two experimental plots where a set of parallel tests was made using 600 cm2 plate with and without quick-setting composite materials. The maximum discrepancy between the values of the deformation modulus obtained for the plates with application of quick-setting composite materials and the “reference” ones (screw and flat plate of 5000 cm2 ) did not exceed 14 %.Results. On the basis of the experimental investigations, the author developed a methodology and “Recommendations for plate loading tests to carry out using quick-setting materials at the plate-soil contact”.Conclusion. The suggested methodology for plate load testing tackles the issue of determining the deformation modulus for very coarse soils by using an intermediate layer of quick-setting liquid material that improves the contact between the plate and the soil for uniform load transfer, thus greatly increasing the accuracy of deformation parameters.