Compaction- and strength properties of stabilised and unstabilised fine-grained tills

Sammanfattning: Fine-grained soils are often regarded as problematic soils in earthworks because of their water- and frost sensitivity. Only limited amounts of fine-grained tills are used as earthwork material today. The main objective of this thesis is to improve the knowledge of how to use and also treat a fine-grained till, so that a greater amount can be utilised as earthwork material. To achieve an increasing use of fine-grained tills, they must be handled in a certain way or treated/modified to achieve the desired properties. This thesis is focused on the compaction- and strength- properties of tills, both untreated and treated with a stabilising agents. Compaction is essential to achieve a good base for foundations for roads, railways and other constructions. To achieve a good result, the water content of the soil to be compacted must be within a certain range. Densification of fine-grained soils at low water contents is about to overcome the soils' “cohesion”. The soils' apparent cohesion is the sum of cohesion and matrix suction. The density increase during compaction is related to the applied compaction energy and the water content of the soils. The results in this study are based on both laboratory investigations and well as field studies. The laboratory results are based on tests performed on 13 different soils. The main type has been clay till but coarser soils such as clayey sand tills have also been studied. The field tests have been performed at two different sites. To conclude: the thesis work shows that fine-grained tills can be used as qualified fills in earthworks, and that the MCA (Moisture Condition Apparatus) has been proven to be a very efficient and accurate tool to predict the properties of a fine-grained till. The relation between the undrained shear strength, cu and MCV (Moisture Condition Value) is expressed by the following equation; cu = 14.1'e^(0.22'MCV) where cu is the undrained shear strength in kPa. Lime is the main soil-stabilising agent. However, cement may be preferred in cold weather conditions since to the chemical reactions also occur at low temperature. Blended binders have proven to be very efficient and could well compete with single binders and in many cases give a considerably better effect than a single binder. Blended binders have many advantages regarding the binders’ working period. The evaluations of blended binders are preferable performed with response surface methodology (RSM) a statistical evaluation technique that evaluates the interactions between the different agents. Different RSM techniques should be used depending on which type of parameter is to be evaluated.