Deep soil mixing – Finnish guideline for stabilisation tests

There has not been a uniform national guideline on laboratory methods for deep soil stabilisation tests currently in Finland. That is why there has been a need to prepare a guideline for both mass and column stabilisation pretesting in laboratory. Based on this new guideline, stabilisation test results in different laboratories should be more comparable. This paper describes the reasons for the differences in deep soil stabilisation test results based on the different practices used in the laboratories. It also reviews and organizes the source
material to identify the crucial factors that have an effect for susceptibility of the stabilisation test results. In the preliminary survey, Finnish laboratories were interviewed about their stabilisation test practices and clear differences in procedures were found. These were particularly the homogenisation of aggregate, the method of compaction, and the storage of samples. The differences were also observed in the reference tests conducted in the laboratories using identical test material. The Finnish Transport Agency’s guideline for the design of deep stabilisation (11/2010) was updated during 2017 – 2018 and published in 8/2018. The update was supplemented by a fully new guideline on the laboratory methods for deep stabilisation tests. This paper presents aspects and procedures that were included in the laboratory guideline. The laboratory guideline was completed and based on the preliminary survey. The content of the laboratory guideline has been agreed by the deep soil stabilisation workgroup.