Continuous compaction control (CCC) offers a promising alternative to conventional spot tests for earthwork quality assurance. However, establishing reliable correlations between intelligent compaction measurement values (ICMVs) and traditional stiffness metrics, such as the deformation modulus (E_v2) from static plate load tests (PLT), remains a challenge. This study investigated the influence of PLT plate size and vibratory roller type on these correlations through a series of full-scale compaction tests conducted on a granular soil bed. Two plate diameters (300 and 600 mm) and two rollers with different static linear loads (36 and 65 kg/cm) were employed. Sixteen ICMVs spanning acceleration-, mechanics-, and energy-based categories were computed and correlated with E_v2. The results showed that the 600-mm plate, despite producing lower E_v2 values, consistently yielded stronger correlations with the representative ICMVs. The lighter roller produced stronger correlations than the heavier roller, likely due to reduced contact loss and better alignment of measurement depths. Mechanics-based ICMVs performed best, with the vibration modulus (E_vib) during the loading phase showing the strongest correlation (R up to 0.8). These findings confirm that E_vib is a suitable indicator for compaction quality control, suggest that the larger plate is preferable for calibration purposes, and underscore the need for machine-specific calibration.

Jordpackning är en av de mest grundläggande och kritiska jordförstärkningsmetoderna, som utförs i nästan alla typer av byggprojekt, med särskild betydelse inom infrastruktursektorn. En väl utförd packning är avgörande för en konstruktions funktion och livslängd, och med tanke på dess betydande miljöpåverkan är det av yttersta vikt att optimera packningsarbetet. För känsliga konstruktioner som järnvägar, där minimala sättningar är ett krav, är optimal packning av yttersta vikt. Detta gäller i synnerhet vid byggnation av moderna järnvägssystem med ”slab-track”, där undergrundens stabilitet är avgörande för att minimera sättningar. Idag finns ett stort behov av att effektivt kunna verifiera packningsresultat. Nuvarande metoder, såsom plattbelastningsförsök (PLT), är tidsödande och ger endast diskreta mätpunkter, vilket begränsar den yttäckande kontrollen. Därför är det av stor vikt att etablera tillförlitliga korrelationer mellan intelligenta packningsmått (ICMV) – som möjliggör yttäckande packningskontroll (YPK) – och konventionella punktprov.

Denna studie adresserar detta behov genom att presentera fullskaliga, kontrollerade laboratorieförsök. Syftet var att systematiskt utvärdera hur plattstorlek (300 och 600 mm) och vält-typ (Dynapac CA3500D och CA6500D med statiska linjelaster på 36 och 65 kg/cm) påverkar deformationsmoduler från PLT samt 16 olika ICMV, vilka spänner över kinematiska, mekanikbaserade och energibaserade kategorier.

Resultaten visar att 600 mm-plattan, trots något lägre deformationsmodul E_v2, gav konsekvent förbättrade korrelationer med ICMV, sannolikt tack vare dess djupare influensvolym. Den tyngre välten producerade högre E_v2 och lägre variabilitet än den lättare. Analys av ICMV-samband avslöjade stark redundans och tre tydliga kluster (harmonisk-, styvhets- och energibaserade), vilket stöder användningen av en enskild representant från varje kluster vid kalibrering. Vibrationsmodulen E_vib och harmonisk-baserade index presterade bäst i korrelation med PLT, medan energibaserade index var mindre lämpliga.

Sammanfattningsvis förbättrar större PLT-plattor och mekanikbaserade ICMV korrelationen mellan YPK och PLT, men vältspecifik kalibrering är fortsatt nödvändig. Dessa resultat ger praktisk vägledning för mer tillförlitliga YPK-baserade arbetsflöden för kvalitetssäkring.

Soil compaction is one of the most fundamental and critical ground improvement methods, performed in almost all types of construction projects, with particular significance within the infrastructure sector. Well-executed compaction is crucial for the performance and service life of a structure, and given its significant environmental impact, optimizing compaction work is of the utmost importance. For sensitive structures such as railways, where minimal settlement is a requirement, optimal compaction is vital. This applies in particular to the construction of modern railway systems using “slab-track”, where subgrade stability is decisive for minimizing settlement. Today, there is a great need to effectively verify compaction results. Current methods, such as the plate load test (PLT), are time-consuming and provide only discrete measurement points, limiting area-wide control. Therefore, it is highly important to establish reliable correlations between intelligent compaction measurement values (ICMV) – which enable continuous compaction control (CCC) – and conventional spot tests.

This study addresses this need by presenting full-scale, controlled laboratory experiments. The aim was to systematically evaluate how plate size (300 and 600 mm) and roller type (Dynapac CA3500D and CA6500D with static linear loads of 36 and 65 kg/cm) affect deformation moduli from PLT as well as 16 different ICMVs, spanning kinematic, mechanics-based, and energy-based categories.

The results show that the 600 mm plate, despite a slightly lower deformation modulus E_v2, yielded consistently improved correlations with ICMVs, likely due to its deeper influence volume. The heavier roller produced higher E_v2 values and lower variability than the lighter roller. Analysis of relationships among ICMVs revealed strong redundancy and three distinct clusters (harmonic-, stiffness-, and energy-based), supporting the use of a single representative from each cluster during calibration. The vibration modulus E_vib and harmonic-based indices performed best in correlation with PLT, while energy-based indices were less suitable.

In conclusion, larger PLT plates and mechanics-based ICMVs improve the correlation between CCC and PLT, but roller-specific calibration remains necessary. These results provide practical guidance for more reliable CCC-based workflows for quality assurance.

Jordpackning är den absolut vanligaste jordförstärkningsmetoden som används i princip i alla byggprojekt, och där är packningskvaliteten avgörande för hållbar infrastruktur. Traditionella metoder för kvali­tetskontroll, såsom plattbelastningsförsök (PLT), brister dock i effektivitet och täckning. Yttäckande packningskontroll ger en kontinuerlig och yttäckande uppföljning, men dess korrelation med plattbelast­ningsförsök har varit svag. Utvecklingen av yttäckande packnings­kontroll har under lång tid varit begränsad, men med nya tekniska möjligheter har intresse återigen väckts för att utveckla tekniken. Som en fortsättning på en serie tidigare utförd forskning, syftar detta doktorandprojekt till att vidareutveckla yttäckande packningskontroll med användning av moderna mät- och analysverktyg. I ett första steg korreleras PLT mot gamla och nya värden från yttäckande pack­ningskontroll. Det slutgiltiga målet är dock att utveckla den yttäckande packningskontrollen så att behovet av statiska plattbelastningsförsök försvinner.

Modelling railway projects has a main challenge in the discrete element method (DEM). The granular material of the embankment consists of millions of fine angular particles which are difficult to model due to the long computational time. The long computational time also prevents the modeling of the higher number of loading cycles. As a result, researchers prefer to simulate the project in 2D to accelerate the simulation. While 2D simulations present a seemingly simple option for modeling railways, they tend to oversimplify the intricacies of particle interactions and the distribution of stress. Nonetheless, the extent to which these simplifications affect the authenticity of the simulations has remained ambiguous. In this study, the periodic cell replication method is used to build extensive long railway tracks significantly faster than conventional methods. Then, this DEM model is calibrated against the measurement results of a physical full-scale ballasted track. The model is then used to simulate several railway projects with different initial particle arrangements and model dimensions in both 2D and 3D. The results show that the 2D models are more dependant on the initial particle arrangement which shows different behavior for the same model. In addition, 2D simulations are incapable of reproducing the principal stress rotation in granular layers due to the moving load of the train wheel. As a result, 3D DEM simulations using the periodic cell replication method is suggested for studying the railway tracks.

Med påbörjad planering och projektering av nya stambanor för järnväg i Sverige, och med en ännu större utveckling och utbyggnad av ballastfria spår världen över, är det viktigt att undersöka möjliga riskområden som kan komma att påverka exempelvis drift och underhåll. Ett av dessa problemområden är övergången mellan järnvägsbank och järnvägsbro. I ett nyligen publicerat examensarbete, utfört på KTH tillsammans med Sweco, har detta problemområde under­sökts med hjälp av numeriska simuleringar med finita element­metoden.

A common geotechnical site investigation method in Sweden is soil-rock sounding. A steel rod is driven into the ground by a percussion drill and different drilling parameters are recorded. The penetration speed and pushing force are used to determine the soil layer profile, the presence of boulders, and the depth to bedrock. This article describes a novel concept where the ground vibrations generated by the drill bit are measured by a geophone at the ground surface to gain more information about the penetrated material. The results of vibration measurements are analyzed in terms of frequency spectra, spectrograms, and two new parameters called “spectral concentration” and “overtone ratio.” These results show that the method can identify the depth of the groundwater table, distinguish boulders from penetration into bedrock, and possibly identify silt, sand, and gravel layers. More data are needed in different soil types to verify the reliability of the concept.

Despite advancements in computational resources, the discrete element method (DEM) still requires considerable computational time to solve detailed problems, especially when it comes to the large-scale models. In addition to the geometry scale of the problem, the particle shape has a dramatic effect on the computational cost of DEM. Therefore, many studies have been performed with simplified spherical particles or clumps. Particle scaling is an approach to increase the particle size to reduce the number of particles in the DEM. Although several particle scaling methods have been introduced, there are still some disagreements regarding their applicability to certain aspects of problems. In this study, the effect of particle scalping on the shear behavior of granular material is explored. Real granular particles were scanned and imported as polygonal particles in the direct shear test. The effect of particle size distribution, particle angularity, and the amount of scalping were investigated. The results show that particle scalping can simulate the correct shear behavior of the model with significant improvement in computational time. Also, the accuracy of the scalping method depends on the particle angularity and particle size range.

In the repetitive static plate load test, a plate is loaded in two cycles where the second loading cycle provides a modulus denoted Ev2. When calculating the stiffness of a railway embankment, Young’s modulus is often assumed to be equal to Ev2 throughout the embankment. This approach, however, provides inaccurate results, mainly due to soil nonlinearity and the influence of confinement stress. Currently, there exists no method to account for these aspects to derive reliable deformation properties of embankments. Occasionally, correction factors are applied to Ev2, resulting in crude estimations. In this study, plate load tests were simulated in PLAXIS 2D using the Hardening Soil Model and calibrated against four field tests, conducted on crushed rock-fill sub-ballast. The calibrated soil properties were applied in finite element simulations of railway embankments with ballastless slab-track systems. Based on the results of finite element analyses, a semi-empirical approach is proposed, which considers confinement stress through a hyperbolic stress–strain relationship. Soil properties for compacted rock-fill with particle grading 0–150 mm were assumed through the results of the calibrated finite element analyses and the method was verified against 43 plate load tests. This semi-empirical method is more accurate than assuming a constant Young’s modulus, while maintaining simplicity and ease of use.

Statiskt plattbelastningsförsök är en av de mest tillförlitliga metoderna för packningskontroll men styvheten som erhålls – även kallad bärighet – ska ses som en empirisk parameter som inte direkt kan översättas till jordmaterialets egenskaper i driftskedet. Detta eftersom plattbelastning utförs vid en betydligt högre spänningsnivå och med en mindre belastningsyta än för de flesta konstruktioner. Ofta används Ev2-modulen som ett direkt mått på E-modulen i beräkningar utan att ta hänsyn till jordens spännings- och töjningsberoende egenskaper. I denna artikel utforskas vad Ev2-modulen egentligen motsvarar och hur den kan användas till att beräkna deformationer. Med hjälp av mätresultat och FEM-simuleringar har en förenklad semi-empirisk metod utvecklats för att beräkna elastiska deformationer i driftskedet utifrån de resultat som erhålls i ett plattbelastningsförsök

A newly developed intelligent compaction method, automatic frequency control (AFC), has been tested in full-scale field tests. The technique utilizes measurements on the drum to determine the resonant frequency of the dynamic roller-soil system and provides continuous feedback to the roller for automatic adjustment of the frequency. This facilitates compaction at the resonant frequency, even for spatially varying soil properties. Previous tests have been conducted with simplified conditions in indoor full-scale tests and in field tests on low embankments. Those tests showed an increased compaction effect with higher surface stiffness that could likely reduce the number of required passes. This paper describes an additional field test, where a rock-fill embankment has been compacted under realistic conditions. The results confirm that compaction is conducted more efficiently when utilizing AFC, compared to conventional compaction. In addition, AFC increases compaction homogeneity, which provides an embankment less sensitive to rearrangement in the serviceability limit state. Implementing this novel technique can thus reduce costs and environmental impact.