Determining the subgrade reaction modulus. Mathematical approach on case study

Abstract

Subgrade reaction modulus (k) is the reaction pressure sustained by the soil sample under a rigid plate of standard diameter per unit settlement measured at a specified pressure or settlement. For the design of industrial slabs, the geotechnical engineer should provide two values for the subgrade modulus: the first value will be used for short-term loadings such as lift-truck wheel loads, and the second value will be used for long-term loadings such as uniform storage loads or wide area rack. Unfortunately, there are no direct laboratory procedure in order to determine the value of the subgrade reaction modulus, the only way to determine the value is by field tests or by correlation with other tests. The most common used field test is the plate bearing test. The paper is based on a case study, conducted on a site located in Romania, Maramures county. In order to verify the slab base and to determine the value of k, plate tests according to German norm DIN 18134 were performed on the site of a large logistics center in Baia Mare. Two methods were used for the interpretation of the data from the tests performed on the site. The first method is based on a program designed in Excel, and the second method is based on a program written in Qt Creator, using C++ programming language. At the end a comparison was made between the results obtained with the two use methods. The interpretation procedure presents a series of difficulties based on the form of the resulting function. These issues were addressed in the present study.