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.

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.

Field Tests for Investigating the Extraction Rate of Piles Using a Vibratory Technique

Factors directly affecting the extraction rate of the piles pulled out by a vibratory pulling system are summarized and classified into five categories(excitation force,resistance,vibration amplitude,pile plumbness keeping,and slowing down at the later stage) from the mechanics and engineering practice.Field tests on steel sheet piles extracted by vibratory technique in different soil conditions are conducted to ascertain how these factors affect the extraction rate of a pile with regard to three major actors of vibratory pile pulling:the pile to be extracted,the selected pulling system,and the imposed soil conditions.The extraction rates of three different sheet pile types(having up to four different lengths) pulled out by two different vibratory pulling systems are documented.The piles with different lengths and types,pulled out with or without a clutch,have different extraction rates.The working parameters governing the vibratory hammer,such as excitation force and vibration amplitude,exert significant influences on the rate of pile extraction,especially in the early stages of up-lift process.The extraction rate of the piles driven in different soil conditions is uniform because different extraction resistances mainly refer to shaft friction.The properties of the pile-soil interface influence the extraction rate of the piles,and the extraction rate decreases with the time for which the piles have been buried in the earth.