LIST OF PUBLICATIONS BY K.R. MASSARSCH click here GRV experts participate actively in research and development projects and are engaged as lecturers at natioanl and international conferences. Below you find a selection of recent publications which can be downloaded. Please do not hesitate to contact us for more information. Massarsch, K.R., Zackrisson, P. and Fellenius, B.H. 2017. Underwater resonance compaction of sand fill. 19th International conference on soil mechanics and geotechnical engineering, Seoul, Korea, 17-22 September, 2017. Proceedings 2017, pp. 2587-2590. Download Underwater compaction of sand fill was required for the stabilization of bridge piers to mitigate the effects of ship impact. Steel caissons were installed to great depth and loose soil layers were excavated and replaced by sand fill. The resonance compaction method was used to increase the stiffness and strength of the sand fill. Vibratory compaction was performed using a variable frequency vibrator, attached to a flexible compaction probe. Compaction was monitored and optimized using an advanced electronic process control system. The compaction effect was controlled using cone penetration testing. Massarsch, K.R, 2017. Recent developments in vibratory driving and soil compaction. 3rd Bolivian International Conference on Deep Foundations, Santa Cruz de la Sierra, Bolivia, April 27-29, Vol. 1, 123-139. Download During the past two decades, the capacity and performance of hydraulic vibrators has undergone a rapid development. By the use of vibrators with variable frequency and eccentric moment, the transmission of the vibration energy to the surroundings can be controlled. Methods and empirical rules for estimating the drivability of sheet piles are presented. The application of modern vibrators is not limited to the driving of piles and sheet piles. The efficiency of vibratory compaction can be enhanced by adapting the vibrator to the resonance frequency of the vibrator-pile-soil system. The optimization of the compaction process by electronic process control is highlighted and illustrated. A new concept is proposed where the dynamic penetration resistance is correlated to the pile penetration speed, measured in terms of the number of vibration cycles during the driving. The validity of the concept is demonstrated by a case history. Finally, examples of pile and ground improvement solutions are presented which take advantage of the fundamental aspects of vibratory driving. Massarsch, K.R. and Fellenius, B.H. 2015. Engineering Assessment of Ground Vibrations Caused by Impact Pile Driving. Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 46 No.2 June 2015, pp. 54 – 63. Download Ground vibrations are an important design consideration for piles driven by impact hammers. The first task is to determine allowable vibration levels; the second task is to predict the intensity of ground vibrations during driving and the attenuation of ground vibrations with increasing distance. The paper describes the Swedish vibration standard which is applicable for pile driving. Commonly used vibration parameters, associated with the evaluation of vibration measurements, are discussed. The importance of pile impedance for ground vibrations is highlighted. A simplified calculation method is proposed which can be used to estimate vertical ground vibration velocity as a function of distance from the driven pile. Two case histories have been evaluated and compared with theoretical predictions, using the proposed method of analysis. Massarsch, KR, Fellenius, BH: 2012. “Early Swedish contributions to geotechnical engineering”; Full-scale testing and design. Honoring Bengt H. Fellenius. Eds: Hussein, MH, Massarsch, KR, Likins, GE, Holtz, RD, American Society of Civil Engineers, ASCE. Geotechnical Special Publication, GSP 227, 2012, 1 - 18 p. Download
The importance of vibration problems induced by pile driving is addressed and guidelines for establishing limiting vibration levels with respect to buildings with different foundation conditions are presented. Basic concepts of pile dynamics and stress wave measurements, which are widely used for the determination of driving resistance and bearing capacity of impact-driven piles, provide important information about ground vibration caused by pile penetration. Dynamic hammer properties and geometry as well as the driving process are important for ground vibration emission from the pile. It is shown that the energy-based, empirical approach, which is still widely used by practicing engineers, is too crude for reliable analysis of ground vibrations and can even be misleading. The main limitations of the energy approach are the assumption that driving energy governs ground vibrations, the omission of geotechnical conditions and soil resistance, and the uncertainty with regard to input values. Three types of ground waves are considered during pile driving: spherical waves emitted from the pile toe, cylindrical waves propagating laterally from the pile shaft, and surface waves, which are generated by wave refraction at the ground surface at a critical distance from the pile. These three wave types depend on the velocity-dependent soil resistance. The most important factor for analyzing ground vibrations is the impedance of each system component, i.e., the pile hammer, the pile, and the soil along the shaft and at the pile toe. Guidance based on geotechnical conditions is given as to the selection of appropriate impedance values for different soil types. A theoretical concept is presented, based on a simplified model, considering the strain-softening effect on wave velocity in the soil, which makes it possible to predict the attenuation of spherical and surface waves and of cylindrical waves generated at the pile toe and the pile shaft, respectively. The concept is applied to define k-values, which have been used in empirically eveloped models and correlated to type of wave and soil properties. An important aspect of the proposed prediction model is the introduction of the vibration transmission efficacy, a factor which limits the amount of vibration force that can be transmitted along the pile-soil interface (toe and shaft). Results from detailed vibration measurements are compared to values calculated from the proposed model. The comparison is very good and suggests that the new model captures the important aspects of ground vibration during penetration of the pile into different soil layers. Finally, based on the presented model, factors influencing the emission of ground vibrations during impact pile driving are discussed.
Wersäll, C. (2008) Blast-Induced Vibrations and Stress Field Changes around Circular Tunnels. Master of Science thesis ISSN 1652-599X, Division of Soil and Rock Mechanics, Royal Institute of Technology. Download ABSTRACT Blast-induced vibrations is a common problem in urban areas during rock excavation and can cause damage to existing structures. Risk management of this problem is regulated in various standards for assessment of damage in buildings and other structures above ground. For underground structures, however, there exists no proper method for damage assessment which is why guidance levels intended for on-ground structures are implemented below ground even though the damage criteria are different. New methods for determining these criteria are therefore necessary. The aim of this study is to propose a more refined concept of blast-induced vibration analysis which can be applied in that process. The problem of dynamic interaction of waves with underground structures is idealized to a cylindrical tunnel in an infinite elastic material (with no material damping) subjected to a plane sinusoidal wave. The main focus is on the compressional wave since this is the predominant type in blast-induced vibrations. However, the interaction of a shear wave is also evaluated briefly for understanding due to its simpler nature. The dynamic response of a circular tunnel was investigated by mathematical analysis and numerical simulation using the three-dimensional distinct element software 3DEC. It was found that a cylindrical cavity shows resonance phenomena when the wavelength of the P-wave is equal to the circumference of the cavity or when the wavelength of the SH-wave is equal to the diameter. This implies that there is a risk of vibration amplification due to resonance during blasting since the dominating frequency of the vibrations is often of the same order of magnitude as the resonance frequency. Furthermore, the tangential stresses caused by the propagating wave are not negligible and might cause damage to the tunnel. The maximum tangential stress can be approximated by a simple relationship.