I recently wrote a paper entitled Development of a Parametric Model for the Simulation of Impact-Vibration Pile Driving Equipment. It was presented earlier today at the 2023 Spring Research and Arts Conference; the slide show for the talk is here.
One of the impact-vibration hammers featured–probably the “cleanest” one in terms of the results–is the S-402A hammer. Here is more information from other sources about this piece of equipment.
Let’s start with Shirai (1978), who discusses this hammer as follows (pp. 48-50):
The S-402 impact-vibration hammer is designed and used for immersion of freezing pipes into sandy, gravel and clay soils to a depth of 18 m with a diameter of 114 mm and can be used for driving pipes with a diameter of 250 mm or probes up to 3 m long.
Operational (accepted) productivity per shift when freezing pipes are immersed to a depth of 9-10 m – 10 piles, and to a depth of 12-18 m – 5 piles.
The S-402A impact-vibration hammer (Fig. 15) consists of two main parts: a vibration exciter (ram) and a head, connected by means of four pairs of cylindrical compression springs (upper and lower) and rods.
The vibration exciter is a system consisting of two electric motors built into a metal case. On the ends of the shafts eccentrics are fixed. When the rotors rotate with the eccentrics in opposite directions, the housing receives vertically directed vibrations. By limiting these, the impact mode of operation is achieved.
These vibrations have two frequencies, one of which, high, is determined by the rotational speed of the eccentrics, and the second, low, is determined by the total stiffness of the springs and the mass of the vibration exciter. Accordingly selected spring stiffness allows the machine to work in impact mode with a certain frequency of impacts.
It has been established that a more stable and advantageous mode of operation of the S-402A impact-vibration hammer (in terms of obtaining the largest range of vibrations of the impact part) is the ratio of the frequency of impacts and the frequency of rotation of eccentrics, equal to 1:2.
The optimal operating mode of the impact-vibration hammer depends on the initial gap between the ram and the head anvil. The design mode of operation of the S-402A impact-vibration hammer corresponds to zero clearance. However, the practice of immersing the elements has shown that due to the deviation of the values of some parameters of the impact-vibration hammers from the calculated ones, the optimal mode takes place with a negative gap of 2 mm. This gap is set by a uniform tightening, after zero gap, of all springs by 2 mm. The range of vibrations of the impact part in this case reaches 50-55 mm.
The head of the impact-vibration hammer is freely put on the pipe or pile with direct transmission of the impact to the immersed elements through the “floating” anvil. Impact-vibration hammer suspension – cable. The impact-vibration hammer can be used with mounted and pumping equipment on a crane or self-propelled units.Shirai, E.N. (1978) Primenenie Vibrotekhniki v Shakhtnom Stroitelstve (Vibrational Equipment Application in Mining Construction.) Moscow: Nedra.
Rebrik (1966) has additional information on this machine as well (pp.80-81):
Impact-vibration hammer S-402A is designed for driving wooden piles with diameter of 22 cm and length of 6 m, as well as for immersion of metal pipes with diameter of 200 mm and drilling small holes in mire.
Impact-vibration hammer S-402A consists of three main units: the ram, head with grips on the wooden pile and springs with tie rods and bolts. The impact part is a massive cast casing with two electric motors and eccentrics at the shaft ends. The headpiece is a tube with anvils for the springs, the upper end of which is equipped with an anvil. The clearance is regulated by the four pairs of springs. In operation, the vibratory hammer is placed on the top face of the pile and is secured to it with gripping attachments.
Impact-vibration hammer S-402A has another modification (Figure 37), which differs from the first one in the presence of an additional load and head design. If, for normal operation of the first modification, the vibratory hammer requires rigid attachment of the head to the pile or pipe and sufficient clamping of the latter in the ground, the second modification, thanks to the additional load, provides effective immersion of piles and pipes without attachment of the head to them.
- Power of electric motors, kW: 5.6
- Number of motors: 2
- Rotation speed of eccentrics, RPM: 1440
- Impact force, kg: 3200
- Number of impacts per minute: 480
- Impact energy, kg-m: 50
- Weight of impact part, kg: 230
- Total weight, kg: 1000
- Weight without bias weights, kg: 400
- Overall dimensions:
- length: 980
- width: 860
- height: 560
Impact-vibration hammer C-402A was developed by VNIIIStroidormash. It is successfully used for driving wooden piles in a number of Moscow construction organizations.Rebrik, B.M. (1966) вибротехника в бурении (Vibration Technology in Drilling.) Moscow: Nedra.
Deciphering Soviet technical information has been a frustrating part of this whole study, and the citation of Rebrik is no exceptions. While the hammer described in Shirai seems to be the same as the one described in the paper, the one in Rebrik has more in common with the S-402 described in the paper (although it’s not identical either.) Comparison of the two figures will also show that the two machines are not visually similr either. As more information becomes available, we will pass it along.