| 1. |
- Ahmad, Alireza, et al.
(author)
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Impact of particle arrangement and model dimensions on DEM modeling of high-speed railway ballasted tracks in 2D and 3D
- 2024
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In: Transportation Geotechnics. - : Elsevier BV. - 2214-3912. ; 47
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Journal article (peer-reviewed)abstract
- 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.
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| 2. |
- Ahmad, Alireza, et al.
(author)
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Scaling granular material with polygonal particles in discrete element modeling
- 2023
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In: Particuology. - : Elsevier BV. - 1674-2001 .- 2210-4291. ; 75, s. 151-164
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Ahmad, Alireza, et al.
(author)
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The influence of the rail beam on the settlement ofhigh-speed railway tracks : A discrete element study
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Other publication (other academic/artistic)abstract
- Modelling railway embankments have two main challenges in the discrete ele-ment method (DEM). First, the granular material of the embankment consistof millions of fine angular particles which are difficult to model due to thelong computational time. As a result, researchers prefer to use spherical orscale-up particles as granular material. Also, it prevents the modeling of thehigher number of loading cycles. Second, the DEM is incapable of includingcontinuous rail beams due to its discrete nature. Therefore, most of the re-search is limited to ignoring the rail beam and other structural elements ofthe track. In this study, a DEM model is calibrated against the measure-ment results of a physical full-scale ballasted track. The model is then used toinvestigate the effect of including the rail beam for high-speed railways sub-jected to 2000 axle passages. The results show that although ignoring therail beam does not substantially affect the results for initial loading cycles,its influence is significant after a couple of hundred axle passages. The modelwithout a rail beam shows more principal stress rotation, more settlement,non-realistic vertical displacement of the sleepers, more particle rearrange-ment and more sleepers’ vibration. Therefore, it is necessary to include therail beam in the long-term analysis of the track to conclude realistic results.
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| 4. |
- Ahmadi, Alireza
(author)
-
Discrete element technique for modeling high-speed railway tracks
- 2023
-
Licentiate thesis (other academic/artistic)abstract
- The Discrete element method (DEM) is a methodology to investigatethe interactions among granular materials. It analyzes the behavior of par-ticulate environments by solving force-displacement equations that adhereto Newton’s second law of motion. Despite its usefulness, the DEM is notwithout limitations, and researchers are still facing certain challenges thatrestrict them from performing detailed analyses of granular materials. Thisstudy addresses two issues in DEM modeling of granular materials in rail-way embankments. Firstly, the long computational time required by theDEM for modeling fine angular particles in granular materials is addressedby exploring the effects of particle scaling on the shear behavior of granularmaterial. This study investigates the impact of particle size distribution,particle angularity, and the amount of scaling on the accuracy and compu-tational efficiency of DEM. Secondly, the limitations of DEM in includingthe continuous rail beam structure in the track are addressed by verifyinga DEM model against physical measurements of a full-scale ballasted trackand investigating the influence of including the rail beam structure on high-speed railway ballasted tracks. The results show that the use of particlescaling in the first study significantly improves the computational efficiencyof the DEM while maintaining accuracy, and this method is used in thesecond study to investigate the influence of the rail beam structure on thebehavior of railway tracks.
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| 5. |
- Bodare, Anders, et al.
(author)
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Planning and Execution of Rock Blasting in Urban Areas
- 2009
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In: Environmental Vibrations. - 9787030257659 ; , s. 784-789
-
Conference paper (peer-reviewed)abstract
- Proper management of technical risks during blasting facilitates efficient project management and helps keeping costs and safety at an acceptable level. it is of crucial importance to incorporate the process of risk management in the design and execution of the project. Risk analyses of the environmental effect of blast-induced vibrations are, in many cases, based on crude concepts which do not take into consideration the fundamental nature of vibratory motion. Realistic modeling of wave propagation in soil and rock requires that correct dynamic parameters are considered and appropriate attenuation models are applied. It is possible to apply relatively simple vibration attenuation concepts for prediction of vibrations in soil and rock and their interaction with structures on or below the ground surface.
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| 6. |
- Ehrmanntraut, Editha, et al.
(author)
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Identification of Soil Layers and Properties by Vibration Measurements during Dynamic Penetration Testing
- 2023
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In: ASTM geotechnical testing journal. - : ASTM International. - 0149-6115 .- 1945-7545. ; 46:2
-
Journal article (peer-reviewed)abstract
- 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.
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| 7. |
- Ehrmanntraut, Editha, et al.
(author)
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Identification of soil layers and properties by vibrationmeasurements during dynamic penetration testing
-
Other publication (pop. science, debate, etc.)abstract
- A common geotechnical site investigation method in Sweden is soil-rock sounding. A steelrod is driven into the ground by a percussion drill and different drilling parameters arerecorded. The penetration speed and pushing force are used to determine the soil layer profile,the presence of boulders, and the depth to bedrock. This paper describes a novel conceptwhere the ground vibrations generated by the drill bit are measured by a geophone at theground surface to gain more information about the penetrated material. The results ofvibration measurements are analyzed in terms of frequency spectra, spectrograms, and twonew parameters called “spectral concentration” and “overtone ratio”. These results show thatthe method can identify the depth of the groundwater table, distinguish boulders frompenetration into bedrock, and possibly identify silt, sand and gravel layers. More data areneeded in different soil types to verify the reliability of the concept.
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| 8. |
- Ehrmanntraut, Editha, et al.
(author)
-
Soil identification by vibration measurements during dynamic penetration testing : a field study
- 2021
-
Conference paper (peer-reviewed)abstract
- The identification of soil and rock in connection with dynamic penetration tests of hard soils, boulders and rock often requires the retrieval of samples. The process is, however, time-consuming and expensive. A more efficient and cheaper dynamic penetration test for the investigation of dense and hard soils or rock is soil-rock sounding. Only limited information of the soil and its properties is retrieved by this method. For soil-rock sounding a percussion drill is operated in a frequency range between 15 and 30 Hz. During penetration, the impacting drill generates continuous vibra-tions, which propagate as waves to the ground surface.This paper describes a new concept, called Jb-Vib, where the vibrations generated by this impacting drill are measured at the ground surface. The objective is to evaluate whether additional quantitative information can be gained which de-scribes the properties of the penetrated material. The vertical and horizontal components of the vibration velocity are recorded with vibration sensors from which the variation of vibration amplitude and the frequency content with depth can be determined. The RMS-value of the vibration velocity and the frequency spectrum can be derived as a function of depth. Furthermore the effect of geometric damping - the decrease of vibration amplitude with distance – can be accounted for. Prior studies suggest that an important parameter, which can help to identify the type of penetrated material, is the fre-quency content of the signal. Spectrograms can be used to present the variation of frequency and signal intensity as a function of depth. It is shown that the frequency content reflects the material which is penetrated by the impacting drill.
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| 9. |
- Ehrmanntraut, Editha, et al.
(author)
-
Vibration measurements during soil-rock sounding : a comparison between accelerometers and geophones
- 2020
-
Conference paper (other academic/artistic)abstract
- There are many different methods to retrieve information about ground properties prior to building and infrastructure projects. In Sweden the most common method is soil-rock sounding (Jb-sounding) which was developed in Norway in the 1990s. Soil-rock sounding is used for identifying the stratification of soil and the depth to bedrock and can be applied in different classes with different accuracy. It is an effective method with low costs but gives restricted information about the penetrated soft soil strata sequences and its properties. Improved knowledge about the presence of different soil and rock layers is necessary for a cost-effective design particularly of deep foundations.The purpose of this research project is to perform vibration measurements on the ground during soil-rock sounding to gain more knowledge about the penetrated ground. The measurements can be executed without influencing or affecting the sounding measurements and show that the frequency content of the signal is reflecting the properties of the penetrated soil layers. As an important step for developing the new measurement method vibration measurements with an accelerometer are compared to simultaneous measurements with a geophone in order to evaluate which sensor is most suitable for retrieving soil information. The results and recommendations of this analysis are presented in this paper.
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| 10. |
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| 11. |
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| 12. |
- Larsson, Stefan, et al.
(author)
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Geotekniker och bergmekaniker ska lära för livet : men hur ska det gå till?
- 2014
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In: Bygg och Teknik. - Stockholm : Förlags AB Bygg & teknik. - 0281-658X .- 2002-8350. ; :1, s. 70-72
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Journal article (pop. science, debate, etc.)abstract
- Geoteknikeroch bergmekaniker ska ha förmågan att projektera, bygga och underhålla geokonstruktionerför det moderna samhället. Konstruktionerna måste vara både ekonomiska, säkra,estetiska och miljövänliga. Ingenjören får sin kompetens genom utbildning,träning och erfarenheter från skolan, annan fortbildning och arbete iprojekten. Kraven på en bred kunskapsbas ökar alltmer, samtidigt som det krävsen betydande fördjupning inom det specifika ämnesområdet. Både högskolorna ochnäringslivet genomgår nu ett påtagligt generationsskifte och det är därförlämpligt att inom de närmaste åren utföra en omfattande didaktisk analysavseende: Vad ska läras ut? Varför ska det läras ut? Hur ska det läras ut? Förvem ska det läras ut? Vi anser att geoteknik och bergmekanikundervisningen börinriktas på att ge ingenjören förmågor som ska utgöra en bas för ett livslångtlärande.
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| 13. |
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| 14. |
- Massarsch, K. Rainer, et al.
(author)
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Cumulative lateral soil displacement due to pile driving in soft clay
- 2013
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In: SOUND GEOTECHNICAL RESEARCH TO PRACTICE. - Reston, VA : American Society of Civil Engineers. - 9780784412770 ; , s. 463-480
-
Conference paper (peer-reviewed)abstract
- Installation of preformed piles in clay causes lateral displacements of soil and of foundations of nearby structures embedded in the ground. The problem has been assessed by first analyzing the displacement effects of a single pile based on model tests and numerical analyses. Lateral soil displacement can be predicted using cavity expansion theory. Model tests were performed to study lateral displacements of soil due to installation of a group of piles. The results of theoretical analyses and model tests were compared with field measurements. A method is proposed to estimate cumulative lateral soil displacements caused by the installation of a pile group. The effect of sloping ground on lateral soil movements is addressed. Prediction of lateral soil displacement due to installation of several rows of piles in clay is illustrated by a practical example.
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| 15. |
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| 16. |
- Massarsch, K. Rainer, et al.
(author)
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Horizontal stress increase induced by deep vibratory compaction
- 2020
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In: Proceedings of the Institution of Civil Engeneers. - : Thomas Telford Ltd.. - 1353-2618 .- 1751-8563. ; 173:3, s. 228-253
-
Journal article (peer-reviewed)abstract
- Compaction by vertically or horizontal oscillating probes increases not only the soil stiffness but also the horizontal effective stress. An important, but often neglected, consequence is that compaction also causes preloading of the soil. The change in horizontal stress following vibratory compaction can be measured independently by two in situ methods - a cone penetration test (CPT) and a flat dilatometer test (DMT). Values of sleeve resistance (CPT) and horizontal stress index (DMT) can be determined prior and after compaction. In this work, five case histories reported in the literature where different vibratory compaction methods were used (dynamic compaction, vibroflotation, VibroWing, TriStar and resonance compaction) were re-analysed. For each test site, the change in CPT cone resistance and sleeve resistance was determined and compared with the increase in horizontal stress index from DMTs. The preloading effect due to vibratory compaction was estimated using empirical correlations.
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| 17. |
- Massarsch, K. Rainer, et al.
(author)
-
Liquefaction induced by deep vertical vibratory compaction
- 2021
-
In: PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-GROUND IMPROVEMENT. - : ICE Publishing. - 1755-0750 .- 1755-0769. ; 174:3, s. 194-205
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Journal article (peer-reviewed)abstract
- Three case histories were analysed where three different methods of deep vertical vibratory compaction were used to treat loose, water-saturated sand. Vertically oscillating probes not only generate cylindrical waves with strong ground vibrations that cause compaction of the soil but may also result in liquefaction. Cone penetration tests (CPTs) were performed before and after treatment to evaluate the compaction effect. Soil liquefaction could be observed on all sites during the start of deep vibratory compaction. On two sites, the onset of liquefaction could be documented by vibration measurements. A conventional CPT-based liquefaction analysis was performed, which suggested that liquefaction could be expected at all sites. The case histories analysed in this study suggest that vertically oscillating probes have the potential of being used as full-scale liquefaction testing machines. A new concept is outlined that could be used to establish the liquefaction hazard at a particular site.
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| 18. |
- Massarsch, K. R., et al.
(author)
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Monitoring and Process Control of Vibratory Driving
- 2019
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In: Geotechnical Engineering. - : SOUTHEAST ASIAN GEOTECHNICAL SOC. - 0046-5828. ; 50:3, s. 1-10
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Journal article (peer-reviewed)abstract
- Vibrators are used increasingly in the foundation industry, primarily for installation of piles and sheet piles, but also for deep vibratory compaction. Fundamentals of vibratory driving are described that make it possible to choose vibrator performance parameters based on field monitoring and performance control. Variable frequency and amplitude vibrators have become available that make it possible to adapt the driving process to project-specific requirements. The components of modern electronic measuring systems are detailed that can be used to monitor, control, and document different aspects of vibratory driving. Two examples are presented-vibratory driving of sheet piles and resonance compaction-which show how the performance of vibrators and sheet piles can be analysed and adapted to meet specific requirements. By using the advanced monitoring and process control systems, the efficiency of vibratory driving is enhanced. From the retrieved parameters, a better understanding of the vibratory driving process is gained, which can be used to develop a valuable database.
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| 19. |
- Massarsch, Karl Rainer, et al.
(author)
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Significance of frequency for vibratory sheet pile driving (Bedeutung der Frequenz für das Vibrationsrammen von Spundbohlen)
- 2021
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In: Bautechnik. - : Wiley. - 0932-8351 .- 1437-0999. ; 98:6, s. 410-422
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Journal article (peer-reviewed)abstract
- Bei modernen Vibratoren können die Vibrationsfrequenz und das exzentrische Moment während des Rammens verändert werden. Das dynamische Zusammenwirken der schwingenden Bohle mit dem umgebenden Boden kann durch Feldmessungen untersucht werden. Bisher wurde der Einfluss der Vibrationsfrequenz auf den Eindringvorgang und die Ausstrahlung von Vibrationen in die Umgebung nicht ausreichend beachtet, obwohl die Frequenz für die Rammbarkeit und die Erschütterungsausbreitung von Bedeutung sind. In vorliegendem Beitrag werden die Ergebnisse von drei Proberammungen beschrieben, bei denen Doppelbohlen in einen mitteldichten kiesigen Sandboden einvibriert wurden. Messungen wurden am Vibrator, an der Spundbohle und im Boden durchgeführt, womit u. a. die Frequenz, die Schwingungsamplitude, die Eindringgeschwindigkeit der Bohle und die Bodenerschütterungen registriert wurden. Eine Analyse der Messwerte zeigt, dass die Schwingungsfrequenz ein wichtiger Parameter ist. Wenn die Bohle nahe der Resonanzfrequenz des Vibrator-Bohle-Bodensystems erregt wird, schwingt die Bohle in Phase mit dem umgebenden Boden. In diesem Zustand sinkt die Eindringgeschwindigkeit ab, während die Vibrationsausstrahlung in den Boden ansteigt. Die Resonanzfrequenz kann einfach durch Messung der Bodenschwingungen bestimmt werden. Effektives Vibrationsrammen wird erreicht, wenn die Vibrationsfrequenz deutlich höher als die Resonanzfrequenz ist. Vibrationsmessungen zeigen, dass durch das Absenken des exzentrischen Moments stärkere Bodenerschütterungen verursacht werden können.
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| 20. |
- Massarsch, K. Rainer, et al.
(author)
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Vibratory driving of piles and sheet piles-state of practice
- 2022
-
In: Proceedings of the Institution of Civil Engeneers. - : Thomas Telford Ltd.. - 1353-2618 .- 1751-8563. ; 175:1, s. 31-48
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Journal article (peer-reviewed)abstract
- The installation of piles by vibratory methods is discussed and illustrated by case histories. The influence of vibration frequency - which can be controlled during vibratory driving but not during impact driving - on pile penetration, bearing capacity and emission of vibration is examined. The driving process affects the performance of vibratory-driven piles more strongly than impact-driven piles. Concepts are presented for assessing driveability. The importance of resonance of the vibrator-pile-soil system (system resonance) for driveability and pile bearing capacity is explained. Ground vibrations measured on and below the ground surface show that strong oscillating horizontal stresses are generated. These stresses can temporarily reduce the shaft resistance during driving, which can explain why vibratory driving is effective even in dense granular soils. Model tests show that, in granular soils, the bearing capacity of piles vibrated after driving at system resonance is significantly higher than that of piles installed only at high frequency. A concept is described suggesting that, during vibratory driving at high frequency, a zone is created adjacent to the pile shaft where the normal effective stress acting against the pile shaft is reduced due to arching. This arching effect can explain the reduced shaft resistance of piles installed at high frequency.
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| 21. |
- Massarsch, K. Rainer, et al.
(author)
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Vibratory plate resonance compaction
- 2020
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In: Proceedings of the Institution of Civil Engeneers. - : Thomas Telford Ltd.. - 1353-2618 .- 1751-8563. ; 173:4, s. 359-369
-
Journal article (peer-reviewed)abstract
- The development of vibratory plate compaction in North America, Japan and Europe is described. In Japan, the vibrator is attached to a massive plate and used as a bouncing tamper, operating at a low frequency. In Europe, the vibrator/plate system operates at a higher frequency and may be dynamically tuned by attaching a heavy mass, supported by elastomeric springs. Three case histories are presented where the compaction effect was carefully monitored by site investigations prior to and after treatment. These show that the depth of influence is directly related to the size of the plate. Finally, a recently developed application of the resonance compaction concept is described and illustrated by a case history.
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| 22. |
- Massarsch, Rainer, et al.
(author)
-
Dynamic Ground Response during Vibratory Sheet Pile Driving
- 2021
-
In: Journal of Geotechnical and Geoenvironmental Engineering. - : American Society of Civil Engineers (ASCE). - 1090-0241 .- 1943-5606. ; 147:7
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Journal article (peer-reviewed)abstract
- Vibratory sheet pile driving is a widely used foundation method. In order to investigate the effect of different operational parameters, such as vibration frequency and eccentric moment on sheet pile to ground interaction, carefully monitored and documented field tests were performed. A single sheet pile was vibrated into a sandy soil deposit (esker) and different operational parameters were varied. The interaction between the vertically oscillating sheet pile and the surrounding ground was studied, using sensors on the vibrator and on the ground in the vicinity of the sheet pile. The effect of vibration frequency and eccentric moment on sheet pile penetration speed and emitted ground vibrations is presented. When the sheet pile is vibrated at the resonance frequency of the vibrator-sheet pile-soil system (system resonance), ground vibrations increase significantly and sheet pile penetration speed decreases. It is concluded that the vibration frequency is an important parameter for the efficient and environmentally safe installation of sheet piles. These tests provide insight into the interaction of a vibrated sheet pile and the surrounding ground. Based on these results, guidelines for the efficient and environmentally friendly installation of piles and sheet piles are proposed.
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| 23. |
- Massarsch, Rainer, et al.
(author)
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Horisontell jordundanträngning vid pålslagning i lera
- 2014
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In: Bygg och Teknik. - Stockholm : Förlags AB Bygg & teknik. - 0281-658X .- 2002-8350. ; :1, s. 46-51
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Journal article (pop. science, debate, etc.)abstract
- I Sverige slås årligen ett stort antal prefabricerade pålar som kan påverka omgivningen påtagligt i form av vibrationer och markrörelser. Redan slagna pålar kan utsättas för horisontalrörelser då resterande pålar i pålgruppen installeras. Pålkommissionens Rapport 95 ”Omgivningspåverkan vid pål- och spontslagning” beskriver en beräkningsmetod som bygger på empiriska tumregler, men som saknar vetenskaplig förankring.Nyligen avslutades ett SBUF-projekt ”Massundanträngning i samband med pålslagning i lera” där resultat från fältmätningar jämfördes med olika beräkningsmetoder. I projektet visades, med stöd av fältmätningar, att beräkningsmetoden enligt Pålkomissionens rapport inte kan förutsäga den horisontella jordförskjutningen på ett tillfredsställande sätt. Istället rekommenderas avancerade beräkningsmetoder, såsom FEM. I föreliggande artikel beskrivs hur jordens horisontalförskjutning kan uppskattas med en enkel beräkningsmodell vid plan eller lutande markyta. Även åtgärder för att minska jordundanträngningen, såsom lerproppdragning, diskuteras.
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| 24. |
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| 25. |
- Norberg, Karl, et al.
(author)
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Effektiv utformning av övergångszoner : – mot ett minskat underhållsbehov av ballastfria spår
- 2023
-
In: Bygg och Teknik. - 0281-658X .- 2002-8350. ; :1, s. 30-33
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Journal article (pop. science, debate, etc.)abstract
- 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
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| 26. |
- Wersäll, Carl, et al.
(author)
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Dynamic response of vertically oscillating foundations at large strain
- 2014
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In: Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014. - : CRC Press. - 9781138001480 ; , s. 643-647
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Conference paper (peer-reviewed)abstract
- A method for calculating the dynamic response of a vertically oscillating foundation on soil with strain-dependent properties is developed. Strain-dependent stiffness and damping are incorporated by an iterative procedure, presenting the response in frequency domain. The calculated dynamic displacement amplitudes are compared to small-scale tests using a vertically oscillating plate. The calculated dynamic quantities agree well with measured amplitudes over a wide frequency range.
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| 27. |
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| 28. |
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| 29. |
- Wersäll, Carl, et al.
(author)
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Field Testing of Automatic Frequency Control for Intelligent Compaction of Embankments
- 2022
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In: Advances in Transportation Geotechnics IV, Proceedings of the 4th International Conference on Transportation Geotechnics Volume 3. - Cham : Springer Science and Business Media Deutschland GmbH. ; , s. 143-152
-
Conference paper (peer-reviewed)abstract
- 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.
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| 30. |
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| 31. |
- Wersäll, Carl
(author)
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Frequency Optimization of Vibratory Rollers and Plates for Compaction of Granular Soil
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Vibratory rollers are commonly used for compaction of embankments and landfills. This task is time consuming and constitutes a significant part of most large construction and infrastructure projects. By improving the compaction efficiency, the construction industry would reduce costs and environmental impact.This research project studies the influence of the vibration frequency of the drum, which is normally a fixed roller property, and whether resonance can be utilized to improve the compaction efficiency. The influence of frequency on roller compaction has not before been studied but the concept of resonance compaction has previously been applied successfully in deep compaction of fills and natural deposits.In order to examine the influence of vibration frequency on the compaction of granular soil, small-scale compaction tests of sand were conducted under varying conditions with a vertically oscillating plate. Subsequently, full-scale tests were conducted using a vibratory soil compaction roller and a test bed of crushed gravel. The results showed that resonance can be utilized in soil compaction by vibratory rollers and plates and that the optimum compaction frequency from an energy perspective is at, or slightly above, the coupled compactor-soil resonant frequency. Since rollers operate far above resonance, the compaction frequency can be significantly reduced, resulting in a considerable reduction in fuel consumption, environmental impact and machine wear.The thesis also presents an iterative equivalent-linear method to calculate the frequency response of a vibrating foundation, such as a compacting plate or the drum of a roller. The method seems promising for predicting the resonant frequency of the roller-soil system and can be used to determine the optimum compaction frequency without site- and roller-specific measurements.
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| 32. |
- Wersäll, Carl, et al.
(author)
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Frequency Variable Surface Compaction of Sand Using Rotating Mass Oscillators
- 2015
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In: ASTM geotechnical testing journal. - 0149-6115 .- 1945-7545. ; 38:2, s. 198-207
-
Journal article (peer-reviewed)abstract
- The influence of vibration frequency was studied in 110 small-scale compaction tests conducted using a vertically oscillating plate. The underlying soil was dry sand, or sand close to the optimum water content. The results showed that there is a resonant amplification, providing a slightly higher degree of compaction. Frequency has a major influence on soil compaction. An iterative method for calculating the dynamic response of the plate, incorporating strain-dependent properties of the soil, is also presented. The calculated frequency response agrees fairly well with measured quantities.
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| 33. |
- Wersäll, Carl, et al.
(author)
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Heavy vibratory plate compaction of silty sand: A field study
- 2022
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In: Soils and Foundations. - : Elsevier BV. - 0038-0806 .- 2524-1788. ; 62:5, s. 101208-
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Journal article (peer-reviewed)abstract
- Heavy vibratory plate compaction is an efficient technique for improvement of granular soils. However, its practical application is limited by insufficient knowledge about the compaction process and the optimum procedure of execution. In this study, compaction tests were conducted in the field with a 40.5-ton heavy vibratory plate compactor. The site consisted of partially saturated, overconsolidated medium-dense silty sand and sandy silt. Such conditions can generally be characterized as difficult for vibratory compaction. The objective of the tests was to study the compaction depth and the influence of treatment layout, duration of compaction, and vibration frequency. In-situ measurements conducted before, during and after treatment included static cone penetration tests, flat dilatometer, and heavy dynamic probing. The in-situ tests showed a statistically significant compaction after treatment. The main conclusions highlight the importance of a sufficient centrifugal force of the vibratory hammer to cause disconnection between the plate and the soil. Other important parameters are the vibration frequency and the duration of treatment, which can be optimized by field monitoring. Full coverage of the ground surface is required for compaction of the entire soil volume. It was also found that the compaction depth corresponds to the side length of the plate, in line with previous studies.
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| 34. |
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| 35. |
- Wersäll, Carl
(author)
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Influence of Frequency on Compaction of Sand in Small-Scale Tests
- 2013
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Licentiate thesis (other academic/artistic)abstract
- Vibratory rollers are commonly used for compaction of embankments and landfills. In a majority of large construction projects, this activity constitutes a significant part of the project cost and causes considerable emissions. Thus, by improving the compaction efficiency, the construction industry would reduce costs and environmental impact. In recent years, rollers have been significantly improved in regard to engine efficiency, control systems, safety and driver comfort. However, very little progress has been made in compaction effectiveness. While the compaction procedure (e.g. layer thickness and number of passes) has been optimized over the years, the process in which the machine compacts the underlying soil is essentially identical to the situation in the 1970s.This research project investigates the influence of one crucial parameter, namely vibration frequency of the drum, which normally is a fixed roller parameter. Frequency is essential in all dynamic systems but its influence on the compaction efficiency has not been studied since the early days of soil compaction. Since laboratory and field equipment, measurement systems and analysis techniques at the time were not as developed as they are today, no explicit conclusion was drawn. Frequencyvariable oscillators, digital sensors and computer‐based analysis now provide possibilities to accurately study this concept in detail.In order to examine the influence of vibration frequency on the compaction of granular soil, small‐ scale tests were conducted under varying conditions. A vertically oscillating plate was placed on a sand bed contained in a test box. The experiments were carried out in laboratory conditions to maximize controllability. The first test setup utilized an electro‐dynamic oscillator where dynamic quantities, such as frequency and particle velocity amplitude, could be varied in real‐time. The second test setup included two counter‐rotating eccentric mass oscillators, where tests were conducted at discrete frequencies. This type of oscillator has a force amplitude that is governed by frequency.The main objectives of the tests were to determine the optimal compaction frequency and whether resonance can be utilized to improve compaction efficiency. Results showed that resonance had a major influence in the electro‐dynamic oscillator tests, where the applied force amplitude is low, and the optimal compaction frequency is the resonant frequency under these circumstances. In the rotating mass oscillator tests, where a high force was applied to the plate, resonant amplification was present but not as pronounced. Since force increase with frequency, the optimal frequency to obtain the highest degree of compaction is very large. In a practical regard, however, frequency should be kept as low as possible to minimize machine wear and emissions while still achieving a sufficient compaction of the soil. Considering the practical issues, it is proposed that surface compactors should operate slightly above the resonant frequency. However, the applicability to vibratory rollers must be confirmed in full‐scale tests.The thesis also presents an iterative method to calculate the frequency response of a vibrating plate, incorporating strain‐dependent soil properties. Calculated dynamic quantities are compared to measured values, confirming that the method accurately predicts the response.
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| 36. |
- Wersäll, Carl
(author)
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Optimering av packningsparametrar för vibrationsvältar
- 2015
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Conference paper (other academic/artistic)abstract
- Jordpackning av bankar och fyllning utförs normalt med vibrationsvält i olika typer av anläggningsprojekt. I ett doktorandprojekt vid KTH studeras hur denna process kan effektiviseras genom att optimera vissa packningsparametrar. Huvuddelen av projektet syftar till att finna den optimala vibrationsfrekvensen. Omfattande småskaleförsök har utförts i laboratorium som visar att frekvensen har stort inflytande över packningseffektiviteten. Fullskaleförsök kommer att visa om och hur dessa resultat kan implementeras i praktiken. Inom projektet har även en beräkningsmodell utvecklats som enkelt kan förutsäga den dynamiska responsen av en vibrerande platta på markytan. Projektet finansieras av Svenska Byggbranschens Utvecklingsfond (SBUF), Dynapac Compaction Equipment AB, Trafikverket, PEAB och Fredrik Bachmans minnesfond.
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| 37. |
- Wersäll, Carl, et al.
(author)
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Planning and Execution of Rock Blasting Adjacent to Tunnels
- 2009
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In: Environmental Vibrations. - 9787030257659 ; , s. 749-756
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Conference paper (peer-reviewed)abstract
- Prediction and monitoring of vibrations from rock blasting is of practical importance. Damage to rock tunnels caused by blasting is fundamentally different to that of conventional buildings. Different damage mechanisms are discussed as well as methods to monitor the development of cracks by analysis of frequency content. For the assessment of the damage potential it is essential to understand wave propagation in rock and the dynamic response of cavities to vibration excitation. Vibration frequency and wavelength in relation to the size of the cavity are important parameters. Vibration amplification of a circular tunnel to a plane wave is analyzed and guidelines given for practical design applications. Filtering the vibration signal, which is often required in national standards, car. give misleading results for tunnels in rock.
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| 38. |
- Wersäll, Carl, et al.
(author)
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Resonant roller compaction of gravel in full-scale tests
- 2018
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In: Transportation Geotechnics. - : Elsevier Ltd. - 2214-3912. ; 14, s. 93-97
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Journal article (peer-reviewed)abstract
- Results from a recent study indicated that compaction by vibratory roller can be made more time- and energy-efficient by operating at a vibration frequency close to resonance. In this paper, the results are verified and the reduction in operating time is quantified by conducting detailed full-scale tests under realistic conditions at two frequencies: the standard operating frequency of the roller and a lower frequency slightly above resonance. Compaction was done in two tests per frequency with 16 passes in each test. The obtained compaction was quantified using a combination of measurement techniques, including laser levelling, nuclear density gauge and static plate load tests. The results confirm that the lower frequency is more efficient for compaction and that utilizing resonance in the roller-soil system can reduce the number of passes. In addition, lowering the frequency reduces energy consumption, environmental impact and machine wear.
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| 39. |
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| 40. |
- Wersäll, Carl, et al.
(author)
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Roller compaction of rock-fill with automatic frequency control
- 2020
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In: Proceedings of the Institution of Civil Engeneers. - : ICE Publishing. - 1353-2618 .- 1751-8563. ; 173:4, s. 339-347
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Journal article (peer-reviewed)abstract
- A new intelligent compaction method for vibratory soil compaction rollers that automatically and continuously adjusts the vibration frequency to obtain resonance in the coupled roller-soil system was evaluated in full-scale field tests on a 1 m high rock-fill embankment. This method has been called automatic frequency control (AFC). Compacting at the resonant frequency results in maximised deformations in the soil by optimising the dynamic behaviour of the system and improving the interaction between the drum and the soil. The embankment was also compacted conventionally at a fixed standard frequency in order to quantify the difference between the two methods. Applying AFC resulted in a higher degree of compaction of the embankment layer. The effect was most significant at the top of the embankment, where considerable compression was obtained - in contrast to the very loose material resulting from conventional compaction - thus eliminating the need for subsequent static passes. Spot tests showed a considerably stiffer embankment surface after a high number of passes using AFC. Other observed benefits of AFC include a more homogeneously compacted embankment, which benefits long-term behaviour, up to 15% reduced fuel consumption, reduced environmental impact and less machine wear.
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| 41. |
- Wersäll, Carl, et al.
(author)
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Small-Scale Testing of Frequency-Dependent Compaction of Sand Using a Vertically Vibrating Plate
- 2013
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In: ASTM geotechnical testing journal. - 0149-6115 .- 1945-7545. ; 36:3, s. 394-403
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Journal article (peer-reviewed)abstract
- Vibratory rollers generally operate at a fixed vibration frequency. It is hypothesized that the compaction of soil could be made more efficient if the frequency could be adapted to specific project conditions. In order to study the applicability to surface compaction, the frequency dependence of compacting dry sand with a vertically vibrating plate was investigated experimentally in 85 small-scale tests. Tests were performed in a test box simulating the free-field condition and with concrete underlying the sand bed. The results show that there is a distinct frequency dependence, implying a significantly improved compaction effect close to the compactor soil resonant frequency. It is suggested that particle velocity is the governing amplitude parameter for vibratory soil compaction, rather than displacement or acceleration. As the soil is compacted, it is also displaced, resulting in surface heave. A larger vibration amplitude implies greater displacement relative to the compacted volume. It was also observed that the compaction and strain-dependent reduction of soil stiffness are closely related.
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| 42. |
- Wersäll, Carl, et al.
(author)
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Soil compaction by vibratory roller with variable frequency
- 2017
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In: Geotechnique. - : Thomas Telford Ltd.. - 0016-8505 .- 1751-7656. ; 67:3, s. 272-278
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Journal article (peer-reviewed)abstract
- Full-scale tests were conducted to study the influence of the operating frequency of a vibratory roller on the compaction of crushed gravel in a controlled environment. Tests were performed at both fixed and variable frequencies. The average densification of the soil was represented by settlement of the ground surface, and depth-dependent density variation before and after compaction was determined by horizontal nuclear density gauge measurements. The resonant frequency was approximately 17 Hz and frequencies in the range 15–35 Hz were tested. The optimum compaction frequency was determined to be around 18 Hz; that is, slightly above resonance, as compared with the standard operating frequency of the roller, 31 Hz. Lower compaction frequency significantly reduces the required engine power and thus fuel consumption and environmental impact, while increasing the lifespan of the roller. Furthermore, the soil closest to the ground surface is loosened at high frequency. This can be avoided with a lower compaction frequency and the need for subsequent static passes can thereby possibly be eliminated.
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| 43. |
- Wersäll, Carl, et al.
(author)
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Soil Heave Due to Pile Driving in Clay
- 2013
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In: Sound Geotechnical Research To Practice. - Reston, VA : American Society of Civil Engineers (ASCE). - 9780784412770 ; , s. 481-499
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Conference paper (peer-reviewed)abstract
- Soil heave due to pile driving in clay is discussed and, in particular, its influence on adjacent piles. Finite element studies and results of model tests are presented and compared with field measurements. It is demonstrated that in the vicinity of the driven pile, the soil is displaced mainly in the lateral direction, similar to soil subjected to passive earth pressure. General rules of estimating soil heave inside and outside a pile group are examined. A method is proposed for estimating soil heave when driving a group of piles. Practical application of predicting soil heave is illustrated by an example.
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| 44. |
- Wersäll, Carl, et al.
(author)
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Stiffness of Ballastless Railway Embankments Determined by Repetitive Static Plate Load Tests
- 2023
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In: Transportation Infrastructure Geotechnology. - : Springer Nature. - 2196-7202 .- 2196-7210. ; 10:6, s. 1032-1049
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Journal article (peer-reviewed)abstract
- 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.
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| 45. |
- Wersäll, Carl, et al.
(author)
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Vibration Source Localization along Railway Tracks
- 2012
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In: Noise and Vibration Mitigation for Rail Transportation Systems. - Berlin : Springer. - 9784431539261 ; , s. 267-274
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Book chapter (peer-reviewed)abstract
- Ground-borne vibration from railway traffic is an increasing problem in urbanized areas and measures are often needed to minimize its effects on the environment. An important question when dealing with railway problems is to identify the source(s) of vibration emitted along the railway track. Once this information is available, it is often possible to mitigate the problem by improving stiffness of the railway track and/or to upgrade worn-out or damaged rail sections and turnouts. This paper describes a method which makes it possible to determine the locations of track sections which are likely to emit strong ground vibration. A purpose-built track-bound vehicle which can be vibrated continuously at different frequencies can identify track sections having unfavorable dynamic foundation conditions. A theoretical concept is proposed to calculate the potential of energy emission from the vehicle moving along the track. Further, an innovative method is presented which makes it possible to determine the location of vibration sources by measurement of ground vibrations from existing railway traffic. This information can be used to determine the location of track sections where remedial measures are needed. Results are presented, illustrating application of the concepts, which can also be applied to other types of vibration problems.
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| 46. |
- Wersäll, Carl, et al.
(author)
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Vibrovältar och jorddynamik - mot effektivare packning
- 2013
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In: Bygg och Teknik. - Stockholm : Förlags AB Bygg & teknik. - 0281-658X .- 2002-8350. ; :1, s. 32-35
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Journal article (pop. science, debate, etc.)abstract
- Packning är den vanligaste jordförstärkningsmetoden och används i stort sett i alla byggprojekt. Ökande byggkostnader och striktare utsläppskrav gör att det finns ett behov av att effektivisera packningsprocessen. I ett doktorandprojekt vid Kungliga Tekniska högskolan (KTH) studeras hur jordpackning med vibrovält kan bli mer effektivt genom att ta hänsyn till amspelet mellan vält och jord samt vältens och jordens dynamiska egenskaper. Projektet inansieras av Svenska Byggbranschens Utvecklingsfond (SBUF), Dynapac, Peab och KTH och utförs som ett samarbete mellan KTH, Dynapac och Peab.
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| 47. |
- Wersäll, Carl, et al.
(author)
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Är Ev2-modulen något att räkna med? : Utförande och tillämpning
- 2023
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In: Bygg och Teknik. - : Byggteknikförlaget. - 0281-658X .- 2002-8350. ; :1, s. 40-45
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Journal article (pop. science, debate, etc.)abstract
- 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
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