Differences in ground vibrations generated from installation


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Differences in ground vibrations generated from installation of bored and vibrated retaining walls
- A field study
Markus Daniels & Katarina Lovén
Master of Science thesis 14/12 Division of Soil and Rock Mechanics Department of Civil and Architectural Engineering Royal Institute of Technology, KTH
Stockholm 2014

© Markus Daniels & Katarina Lovén Master of Science thesis 14/12 Division of Soil and Rock Mechanics Royal Institute of Technology Stockholm 2014 ISSN 1652 – 599X

Preface
This is a Master of Science thesis performed at the Division of Soil and Rock Mechanics, KTH. The thesis was carried out for and supported by Skanska Grundläggning. The initial idea for the subject came from the authors and has been developed to satisfy both KTH and Skanska Grundläggning. The results from this thesis will be used as a support when vibrations generated from retaining wall installations can be a problem. We would like to thank our supervisors; Stefan Larsson, professor at KTH, for believing in the subject and giving us the ingredients of how to write a thesis, and Joakim Berg, district manager at Skanska Grundläggning, for believing in the subject and for helping us with all practical issues that we have faced during the study. Further, we like to thank the people that made the field test possible. Kent Allard, from Geometrik and the Division of Soil and Rock Mechanics at KTH, and Kent Lindgren, from KTH Wallenberg Laboratory, for helping us perform the field measurements and involving us in the theories behind signal acquisition. Fanny Deckner, geotechnical engineer at NCC and PhD at KTH, for borrowing us the measuring devices and for sharing experience from previous field tests. Hans-Erik Forslars and his team at the construction site for helping us with all arrangements. Finally we want to thank Carl Wersäll for the help with developing the subject, how to perform the measurements accurate and for all help regarding the processing of the results. Also thanks to Rainer Massarsch who shared useful knowledge with us.
Stockholm, June 2014
Markus Daniels & Katarina Lovén
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Abstract
For construction sites where vibrations may be a problem to the surrounding environment, it is important to choose the right construction method that will create acceptable levels of vibrations. The vibrations created when installing bored steel pipe piles are considered to be of smaller magnitude than the vibrations generated from vibratory driven piles. Although, there are no reliable prediction models and no field studies available regarding ground vibrations generated from bored steel pipe piles. By comparing the vibrations generated when installing a bored RD-pile with a vibratory driven sheet pile in similar conditions, their different impact on ground vibrations could be evaluated. This was achieved by performing a field study where the ground vibrations were measured for both methods at the same construction site. The results showed that the vibrations were smaller for the bored RD-pile wall compared with the vibratory driven sheet pile wall and that the vibrations were of different character. The results indicated that boring, by destroying and removing the material ahead, will generate smaller vibrations compared with the pile being forced through the material.
Keywords: bored piles, ground vibrations, RD-pile wall, sheet pile wall, vibratory driven piles.
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Sammanfattning
För grundläggningsarbeten på platser där vibrationer kan anses vara ett problem för omgivningen är det viktigt att välja installationsmetoder som kommer att generera acceptabla vibrationsnivåer. Vibrationer som skapas vid borrning av stålrörspålar anses vara mindre än vibrationer skapade från vibrering av spontplank. Trots detta finns det idag inga tillgängliga vibrationsstudier från borrade stålrörspålar eller tillförlitliga modeller för att förutse dessa vibrationer. Genom att jämföra vibrationerna som skapas vid installation av en RD-vägg med en vibrerad spont i liknande geologiska förhållande kunde deras inverkan på markvibrationer utvärderas. Detta uppnåddes genom en fältstudie där markvibrationerna mättes hos båda metoderna på samma plats. Resultaten som uppnåddes visade att vibrationerna genererade från RD-väggen var mindre jämfört med vibrationerna uppmätta hos sponten. Vibrationerna var också av olika karaktär. Resultatet indikerade att borrning, genom att bryta sönder och avlägsna materialet framför sig, genererar mindre vibrationer jämfört med en spont som blir tvingad genom materialet.
Nyckelord: borrade pålar, markvibrationer, RD-vägg, spont, vibrerade pålar.
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Nomenclature

Abbreviations

DTH OCR PI PPV RD SRSS TVS

Down the hole Over consolidation ratio Plasticity index Peak particle velocity Ruukki drilled Square root of the sum of squares True vector sum

Symbols

Greek symbol ̅

Explanation Absorption coefficient Impedance ratio Tuning ratio Cyclic shear strain Degradation index Critical angle Angle of incident wave Angle of refracted wave Wave length Poisson’s ratio Damping ratio Pi Density Stress Shear strength Cyclic shear stress Phase angle Circular frequency Load frequency Natural frequency

Latin symbol

Explanation Amplitude Displacement amplitude of incident wave Area of loop Acceleration Wave propagation velocity Damping (only for equation 2.6) Wave velocity in pile Wave velocity in hammer Compression wave velocity / P-wave velocity
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Unit rad ° ° m kg/m3 Pa kPa Pa rad rad/s rad/s rad/s
Unit m m J m/s2 m/s Ns/m m/s m/s m/s

Shear wave velocity / S-wave velocity Diameter Depth of pile Critical distance Young’s modulus Eccentric distance Static surcharge force Building factor Centrifugal force Driving Force Foundation factor
Horizontal component of centrifugal force Material factor Vertical component of centrifugal force Frequency Driving frequency Shear modulus Initial shear modulus Secant shear modulus Tangent shear modulus Moment of inertia Damping factor Stiffness Calibration coefficient Hammer length Length of pile Wavelength in pile Oedometer modulus Specified eccentric moment Eccentric moment from a single eccentric mass Magnification factor
Mass Weight of single eccentric mass Number of cycles with large strain Function of the wave (for equation 2.15) Rotation per minute (for equation 2.21) External force Amplitude of external force Distance from vibration source Dynamic soil resistance along pile shaft Dynamic soil resistance at pile toe Radius Eccentric radius Contact area between shaft and soil Sensitivity Period of vibration Time Degradation parameter Voltage output from DAT recorder
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m/s mm m m Pa m N N N -
N N Hz Hz Pa Pa Pa Pa m4 N/m (m/s2)/V m m m Pa kgm kgm -
kg kg rpm N N m kN kN m m m2 s s V

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Differences in ground vibrations generated from installation