Mass stabilization is not a common soil improvement method in Sweden, and even less so in sulfide soils. Previous research indicates that a linear elastic material model is suitable for settlements in stabilized sulfide soil. A construction project in the northern part of Sweden applied mass stabilization in sulfide soil. This was an opportunity to study the mass stabilized sulfide soil in the field. This master thesis was executed in parallel to that construction project.  Ground preparations in the project meant that 5-8 m fill would be placed on fine-grained sulfide soil. Soil improvement and specific foundation designs were determined to be required.  Mass stabilization of the sulfide soil was one of the soil improvement methods used. The binder recipe for the mass stabilization was determined to be 60 kg cement/m3. Which also was the binder recipe analyzed in this thesis. The goal of the thesis was to investigate if settlements in stabilized sulfide soil could be predicted with a linear elastic model. This was done by using soil parameters derived from: o   Back calculations of measured settlements caused by a test embankment. o   UCS tests. o   Oedometer tests. Deriving soil parameters by back calculation from the test embankment was done by: Assuming Terzaghi’s one dimensional consolidation theory. Defining the settlement curve by Casagrande’s logarithm of time fitting method. And then iterating the elastic modulus so that calculated settlements would match the defined settlements. The same method used for back calculations of the test embankment was performed in micro-scale on the Oedometer tests. Deriving soil parameters from the UCS tests was done according to previous recommended methods presented by (Al-Jabban, 2019) and (Åhnberg, 2006). The derived soil parameters were then used in a numerical model in Plaxis 2D to calculate settlements. The material model Mohr-Coulomb was used in Plaxis 2D. Three different settlement calculations were performed, one for each source of soil parameters. The calculated settlement results were compared to measured settlements caused by the test embankment. The calculated settlements gave good predictions of measured settlements in stabilized sulfide soil during immediate- and primary consolidation. However, depending on the binder recipe, secondary consolidation might occur in stabilized sulfide soil.  Some binder recipes underneath the test embankment seemed show no secondary consolidation. But the analyzed binder recipe, 60 kg cement/m3 experienced secondary consolidation. Secondary consolidation cannot be calculated with the linear elastic material model used in Plaxis 2D. Nor can it be evaluated from the UCS test. However, if secondary consolidation occurs, it can be added with hand calculations by parameters derived from “Casagrande logarithm of time fitting method.” The calculated settlements from back calculation of the test embankment and from the oedometer tests gave good predictions of the settlements during secondary consolidation. But this should be confirmed by measuring settlements over a longer period of time.  One advantage with soil parameters derived from laboratory investigations is that it is a faster method than soil parameters derived from back calculations of a full-scale field test.

Although it has been established that in-situ soil mixing has improved the bearing capacity of soils, additional research is needed to better understand the effect of soil mixing on lateral resistance of pile caps. To do this, in-situ soil mixing was used to strengthen weak clay adjacent to a pile cap of a driven pile foundation. The mass stabilization method or mass mixing was used to treat an 11 ft wide, 4 ft thick, and 10 ft deep zone consisting of an average 475 psf clay that was adjacent to a 9-pile group in 3x3 pile configuration capped with a 9 ft x 9 ft x 2.5 ft, 5000 psi concrete cap. The mass mixing involved 220 cubic ft of in-situ soil and was mixed with an additional 220 cubic ft of jet grout spoils producing a mixing ratio of 1 to 1. All of the mass mixing took place after construction of the pile caps. Laboratory testing of the mass mix slurry showed an unconfined compressive strength of 20,160 psf or 140 psi. Lateral load testing of the pile foundation was then undertaken. The results of this testing were compared with similar testing performed on the same foundation with native soil conditions. The lateral resistance of the native soil was 282 kips at a pile cap displacement of 1.5 inches, and the total lateral resistance of the pile foundation treated with mass mixing was increased by 62% or 170 kips. Of the 170 kips, 90% to 100% can be attributed to the increased passive force on the face of the mass mixed zone and shear on the sides and bottom denoting that the mass mixed zone behaved as a rigid block.

Vid utvidgning av befintliga hamnar kan den relativt nya metoden stabiliserade/solidifierade (S/S) förorenade muddermassor användas i anslutning till spont. S/S metoden används för att binda föroreningarna fysikaliskt eller stänga in dem samt för att förbättra massornas hållfasthets- och deformationsegenskaper. Istället för att deponera dessa, ofta förorenade, muddermassor till ett högt pris kan det återanvändas i hamnkonstruktionen som ett byggmaterial. Det finns få rapporter som behandlar stabiliserade massor i anslutning till spont och hur de samverkar, vilket gör att det inte finns tydliga riktlinjer för hur metoden ska användas. Dessutom finns det stora osäkerheter kring hur utvecklingen av den odränerade skjuvhållfastheten ökar över tid och hur den kan tas hänsyn till vid projekteringen och därför kan metoden inte utnyttjas på ett effektivt sätt. Den odränerade skjuvhållfastheten utvärderas som halva tryckhållfastheten. Syftet med studien är att kunna prognostisera hur jordtrycket mot en spont beror på de S/S -behandlade muddermassornas egenskaper. Vidare har en projekteringsmetodik till S/S massor i anslutning till spont föreslagits. För att svara på detta har en litteraturstudie gjorts för att samla bakgrundsinformation och skapa en djupare förståelse för ämnet. Därefter gjordes en parameterstudie i FEM-programmet PLAXIS. Resultatet från parameterstudien kunde sedan jämföras med tidigare fält- och laboratorieförsök där egenskapernas förändringar över tid har studerats. Med detta som bakgrund kunde en projekteringsmetodik föreslås. Muddermassorna kan initialt liknas vid en vätska som orsakar ett hydrostatiskt tryck mot sponten. Med tiden kommer massorna härda och därigenom ökar hållfastheten, detta gör så att det horisontella jordtrycket minskar samtidigt som en vertikal pålastning sker vilket ökar det horisontella jordtrycket. Från litteraturstudien kunde det även ses att muddermassornas slutgiltiga hållfasthet och tillväxt beror på bindemedelsmängd och kombination som i sin tur måste anpassas efter muddermassornas vattenkvot och organisk halt. Från parameterstudien kan slutsatsen dras att en av faktorerna som har en större påverkan är hur hög skjuvhållfastheten är efter första härdningen när alla muddermassor har pumpats på plats samt förhållandet mellan skjuvhållfastheten och elasticitetsmodulen och hur de utvecklas. I den föreslagna projekteringsmetoden rekommenderas att dräneringstyp odränerad A och materialmodell Mohr-Coulomb ska användas vid simuleringar. Då det finns så stora osäkerheter kring S/S muddermassor anses materialmodell Mohr-Coulomb vara fullt tillräcklig jämfört med andra mer avancerade modeller då det finns stora osäkerheter kring indatan. Dräneringstyp odränerad A är den mer avancerade dräneringstypen av de tre och tar hänsyn till fler parametrar. Eftersom det kommer ske en utveckling av friktionsvinkel kommer modellen ge en bättre representation. / When expanding existing ports, the relatively new method ofvstabilized/solidified (S/S) contaminated dredged material can be used in connection with a sheet pile wall. The S/S method is used to physically bind the contaminants or trap them and to improve the strength and deformation properties of the masses. Instead of depositing these, often polluted, dredged materials at a high price, it can be reused in the port construction as a buildingmaterial. There are few reports that deal with stabilized masses in connection with a sheet pile wall and how they interact, which means that there are no clear guidelines for how the method should be used. In addition, there are great uncertainties about how the development of the undrained shear strength increases over time and how it can be taken into account in the design and therefore the method cannot be used in an efficient manner. The undrained shear strength is evaluated as half of the compressive strength. The purpose of the study is to be able to forecast how the earth pressure against a sheet pile wall depends on the properties of the S/S-treated dredged material. Furthermore, a design methodology for S/S material in connection with sheet pile wall has been proposed. To answer this, a literature study has been done to gather background information and create a deeper understanding of the subject. A parameter study was also done in the FEM-program PLAXIS. The results from the parameter study could then be compared with previous field and laboratory experiments where the changes in properties over time have been studied. With this as a background, a design methodology could be proposed. The dredged masses can initially be likened to a liquid which causes a hydrostatic pressure against the sheet pile wall. Over time, the masses will harden and thereby increase the shear strength, this means that the horizontal earth pressure decreases at the same time as a vertical loading takes place, which increases the horizontal earth pressure. From the literature study, it could also be seen that the final shear strength and growth of the dredged material depends on the amount of binder and combination, which in turn must be adapted to the water content and the organic content. From the parameter study, it can be concluded that one of the factors that has a greater impact is how high the shear strength is after the first hardening when all dredged materials have been pumped in place and the relationship between the shear strength and modulus of elasticity and the development. In the proposed design method, it is recommended that drainage type undrained A and material model Mohr-Coulomb should be used in simulations. As there are such large uncertainties regarding S/S dredged materials, the Mohr-Coulomb material model is considered to be fully sufficient compared with other more advanced models as there are large uncertainties regarding the input data. Drainage type undrained A is the more advanced drainage type of the three tested and takes the materials friction angle into account. Which will give a better representation.