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. and Fellenius, B. H. (2008) Ground Vibrations induced by Impact pile Driving. Keynote Lecture, International Conference on Case Histories in Geotechnical Engineering. Arlington, 2008. Download ABSTRACT 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.