Project Overview
Since 2000, the Shanghai Municipal Government has made clear plans emphasizing the conversion of shoreline functions, with the goal of transforming the production shoreline between the two banks of the Huangpu River into a living shoreline to serve urban development. By the end of 2017, the 45-kilometer shoreline public space between Yangpu Bridge and Xupu Bridge is to be connected and opened. Among them, the 23-kilometer connected section on the east bank of the Huangpu River will have 12 garden bridges built, concentrating the construction of these garden bridges that integrate green spaces, buildings, and river landscape. Project Key Points
The project has a long distance, many surrounding buildings, and is close to the road. Some piles are only 6 meters away from houses and the main pier foundation of the Huangpu Bridge. Construction is difficult, with high requirements and a short construction period. The strata are complex with thick sand layers; the bearing layer from 35m to 40m is entirely silty sand, and the standard penetration test N value at some pile locations exceeds 50. The foundations all use permanent steel pipe piles, material: Q345B, diameter 600mm with wall thickness 19mm, diameter 700mm with wall thickness 19mm, diameter 800mm with wall thickness 19mm, diameter 1200mm with wall thickness 19mm, pile length 40m-50m. Using steel pipe piles for permanent foundations offers high construction efficiency, no mud pollution, rapid soil recovery, and is green and environmentally friendly.
The project contractor is Shanghai Construction Group. For test piles, they initially used high-frequency hydraulic vibratory hammers with small eccentric moment and small amplitude: a European-imported high-frequency hydraulic vibratory hammer with 230t excitation force, an American-imported high-frequency hydraulic vibratory hammer with 400t excitation force, and a domestic YZ400 high-frequency hydraulic vibratory hammer with 400t excitation force. None of the three large-excitation-force high-frequency hydraulic vibratory hammers could meet the pile driving requirements. When driven to 35m depth, before entering the silty sand layer, the steel pipe pile could no longer penetrate. After more than 3 hours of driving, the steel pipe pile still had no penetration. Because the high-frequency hydraulic vibratory hammer has small eccentric moment and small amplitude, it cannot liquefy the sand layer and vibrates together with the strata, causing a series of problems: loud noise and strong vibration. Staff in the project office could no longer work peacefully due to the excessive noise and vibration, and the project department decided to stop construction.
At their wits' end, the Shanghai Construction Group project department could only temporarily use the 230t excitation force high-frequency hydraulic vibratory hammer to drive the first 21m section, then butt-weld the second 21m section, and then planned to transfer a 70RF resonance-free high-frequency hydraulic vibratory hammer from another project department of the group to drive the second section. However, as time passed day by day and the construction period became increasingly tight, the 70RF was slow to arrive. After several setbacks, the project department thought of the resonance-free electric vibratory hammer, but having seen high-frequency hydraulic vibratory hammer manufacturers consistently promote claims that electric vibratory hammers have less force and more vibration and noise, the project department still had doubts. So our company sent a sales specialist and a technical specialist to negotiate with the leaders of the Shanghai Construction Group project department. The project leaders raised a series of questions: Being so close to the main pier foundation of the Huangpu Bridge, will vibration have an impact? Being so close to the nearby postpartum care center, will noise have an impact? The silty sand layer is both dense and thick; can it be vibrated into the ground?
Shanghai Zhenzhong Machinery Manufacturing Co., Ltd. has always adhered to the business philosophy of "starting from the customer, serving the customer," believing that superior product technology would surely accomplish this pile driving task. On the spot, the sales specialist offered to provide a resonance-free electric vibratory hammer free of charge for test pile driving. The project department leaders readily agreed. Based on the geological survey report provided by the project department, as well as the pile type and required driving depth, analysis and calculation were carried out. The company's technical specialist analyzed why the previous high-excitation-force high-frequency hydraulic hammers could not drive the piles: it was not that the excitation force was insufficient, but that the high-frequency hydraulic vibratory hammer has high rotation speed, small eccentric moment, and small amplitude, and therefore could not drive the piles. Thus, the Shanghai Zhenzhong technical specialist recommended the EP550 resonance-free adjustable eccentric moment electric vibratory hammer with 225t excitation force to complete this pile driving task.
Strength proves everything. The company's EP550 resonance-free adjustable eccentric moment electric vibratory hammer not only successfully drove the test pile, which had already passed the 10-day soil recovery period and still had 5 meters left undriven to the required elevation by the high-frequency hydraulic vibratory hammer, through the cohesive silt to the required elevation, but also went on to continuously and successfully drive several production piles, each pile steadily reaching the required elevation in less than 10 minutes on average.
The "resonance-free stepless adjustable eccentric moment technology" is indeed extraordinary. It not only achieves "zero" start and "zero" stop, overcoming the resonance generated when starting and stopping with eccentric moment, but also allows stepless adjustment of the eccentric moment from zero to the design maximum during operation. When workers go down to measure the elevation, the eccentric moment can be adjusted to "zero," allowing safe elevation measurement. There is no need to stop and restart each time like with ordinary vibratory hammers, which also brings resonance hazards. The "resonance-free stepless adjustable eccentric moment technology" also allows reducing the eccentric moment when finishing driving, slowly vibrating the pile down to the required elevation.
In this project, three models of Shanghai Zhenzhong's resonance-free stepless adjustable eccentric moment electric vibratory hammers participated in construction: EP550, EP400, and EP180. They not only completed the pile driving tasks for various pile types, but also won unanimous recognition from the Shanghai Construction Group project department and the group company. The vibration and noise were not as loud as the high-frequency hydraulic vibratory hammer manufacturers had previously claimed. The vibration and noise were often covered by the noise from generators and road traffic. Since pile driving was very smooth and efficient, the vibration impact was even less worth mentioning, almost zero. The crawler crane operator said with a broad smile: "This electric vibratory hammer is much better than the previous hydraulic vibratory hammers. Now I can finally operate the crane in the cab with peace of mind!"

Tip 1: The EP series resonance-free stepless adjustable eccentric moment electric vibratory hammers are a new series of products jointly developed by Zhenzhong Company, Beijing Research Institute of Construction Mechanization, and Japan Kencho Co., Ltd. This series has won the first prize for scientific and technological progress from the Ministry of Construction and was listed as a project in the Ministry of Construction's Guide to Promotion and Transformation of Scientific and Technological Achievements. In the 1990s, it was exported to Japan and hailed as the "new era pile hammer." The Japanese Ministry of Construction (now the Ministry of Land, Infrastructure, Transport and Tourism) tested and evaluated this series and listed it as a new technology promotion product.
Its biggest feature is the use of a hydraulic control eccentric conversion device, which achieves "zero" start and "zero" stop, overcoming the resonance generated when starting and stopping with eccentric moment, and allows stepless adjustment of the eccentric moment from zero to the design maximum during operation to suit different soil layers for pile driving and extraction, thereby achieving ideal pile driving and extraction speed and efficiency.
Tip 2: There may be some misconceptions about vibratory pile hammers. For example, some believe that the higher the rotation speed or frequency of the vibratory hammer, the better the pile driving effect, where "better effect" mainly refers to higher pile driving efficiency and lower energy consumption. However, this is not a correct view. When the vibratory hammer frequency is too high, its eccentric moment is often too small, resulting in too small an amplitude of the vibratory pile hammer. When the amplitude is too small, the soil layer often cannot be "liquefied" or the soil is vibrated denser, preventing the pile from sinking. If the vibratory pile hammer frequency is too low and the eccentric moment too large, the amplitude of the vibratory pile hammer becomes too large; excessive amplitude often brings problems of high energy consumption and strong vibration perception. Extensive pile driving experience shows that different soil layers have a resonant frequency. Only when the vibration frequency of the vibratory pile hammer equals or approaches the resonant frequency can the ideal pile driving effect be achieved, i.e., low energy consumption and high efficiency. Therefore, it is necessary to analyze and compare according to the soil geology and the specific conditions of the pile to be driven or extracted, and to reasonably select the vibratory hammer model in combination with cost-effectiveness.
　　Shanghai Zhenzhong has always taken "striving for leading pile engineering technology and creating first-class product quality" as its corporate goal, and is willing to contribute to China's green and environmentally friendly construction.