Prediction of ground-borne vibration induced by impact pile driving:numerical approach and experimental validation

Deep foundations are currently used in engineering practice to solve problems caused by weak geotechnical characteristics of the ground.Impact pile driving is an interesting and viable solution from economic and technical points of view.However,it is necessary to ensure that the environmental drawbacks,namely ground-borne vibration,are adequately met.For this purpose,the authors propose an axisymmetric finite element method-perfectly matched layer(FEM-PML)approach,where the nonlinear behavior of the soil is addressed through an equivalent linear methodology.Given the complexity of the problem,an experimental test site was developed and fully characterized.The experimental work comprised in-situ and laboratory soil characterization,as well as the measurement of vibrations induced during pile driving.The comparison between experimental and numerical results demonstrated a very good agreement,from which it can be concluded that the proposed numerical approach is suitable for the prediction of vibrations induced by impact pile driving.The experimental database is available as supplemental data and may be used by other researchers in the validation of their prediction models.

Ground-borne vibrations induced by impact pile driving: experimental assessment and mitigation measures

Impact pile driving is an interesting technique for the construction of deep foundations from a practical and economical point of view.However,the generalization of this technique can be restricted due to the excessive vibration levels that can be generated,which can be especially problematic in residential areas.However,different mitigation measures can be applied to prevent excessive vibration levels inside buildings located near construction sites.To compare its efficiency through a numerical prediction tool,two experimental test sites are first presented and characterized.From the results obtained,it was found that the construction of an open trench near the impact source can be used as an efficient mitigation measure to reduce the maximum vibration levels evaluated in this study.

The Influence of Water-Jet Modification of Soil Conditions on Reduction of Vibrations during Sheet Pile Driving in the Subsoil

Vibratory driving is the most efficient method of sheet pile installation. The elimination or at least reduction of harmful consequences of sheet pile vibratory driving becomes an increasingly important and often the decisive factor in the selection of the excavation protection technology. In difficult soil conditions with strength soil parameters, pressure water jetting precedes sheet pile driving. This technique changes the soil properties, destroying its existing structure near the installed sheet pile. Unfortunately, the results and achievements of contractors using this technique are very often held confidential or simply remain in the records and it is difficult to find papers on this subject. This article features a detailed description of jet-assisted sheet pile driving, including a prefabrication description for the sheet pile toe used to jet water through, water pressure and quantity data and the results with regard to reduce vibrations and noise, as well as to the increase in sheet pile vibratory driving performance.

Circular and Faceted Monopile Installation Fatigue Damage

There are currently no models predicting localised stressing induced in monopole foundations resulting from pile driving installation. A scaled down test was conducted for both circular and faceted monopile, during which monopile stressing was measured. From the stress data gathered fatigue damage was estimated. Fatigue damage of the faceted geometry is significantly larger than that of the circular geometry. It is shown that in the worst case the fatigue damage incurred is still negligible compared to the full service life of the foundation. Suggestions for future developments are made, such developments can be helpful in providing greater understanding of the occasional cases where fatigue damage resulting from pile driving is not negligible and has perhaps resulted in failure.

Drivability of Large Diameter Steel Cylinders During Hammer-Group Vibratory Installation for the Hong Kong–Zhuhai–Macao Bridge

The Hong Kong–Zhuhai–Macao Bridge(HZMB)involved the installation of 120 mega-cylinders with a diameter of 22 m,weights up to 513 t,and penetration depths up to 33 m using an eight-vibratory hammer group.Due to the lack of engineering experience on the drivability of large-diameter cylinders under multiple vibratory hammers,predicting the penetration rate and time of steel cylinders is an open challenge that has a considerable impact on the construction control of the HZMB.In this study,the vibratory penetration of large-diameter steel cylinders in the HZMB is investigated based on geological surveys,field monitoring,and drivability analysis.The vibratory penetration rate,installation accuracy,and dynamic responses of the steel cylinders at both the eastern and western artificial islands are analyzed.The dynamic soil resistance has a great influence on the cylinder drivability.However,the current design methods for estimating the vibratory driving soil resistance are proven inaccurate without considering the scale effects.Therefore,a modified method with a normalized effective area ratio A_(r,eff)is proposed in this study to calculate the vibratory soil resistance for open-ended thin-wall cylinders under unplugged conditions.Considering the scale effects on the vibratory driving soil resistance,the proposed method leads to closer results to the measured data,providing a reference for future engineering practice.