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|Eccentric value, kg-cm||1||0.55||0.35||0.25|
|Frequency, Vibrations per minute||1,500||1,300-1,500||1,500||1,200-1,500|
|Greatest dynamic force, kN||250||140||83||62|
|Mass of vibrating parts, tons||0.7||0.4||0.35||0.25|
|Mass of static parts (with electric motor), tons||1.5||0.8||0.85||0.5|
|Amplitude of vibrations (without pile), mm||14.3||13.8||10||10|
|Power of electric motor, kW||40||28||16||11|
|Dimensions, mm||l,270 x 800||l,000 x 960||l,250 x 680||830 x 760|
|Height (without driving cap), mm||2,250||1,150||1,250||1,380|
|Mass of pile driver, tons||2.2||1.2||1.2||0.75|
The simplest type of vibratory pile driver mentioned above is characterized by a relatively high eccentric value and considerable mass. In the USSR, low-frequency vibratory pile drivers of several standard sizes are produced and used. Their technical characteristics are presented in Table 4.23.
|Eccentric value, kg -cm||9.3||26.3||22.4/29||50|
|Frequency, vibrations per minute||420||408||437/ 556||475/ 550|
|Dynamic force, kN||250||44||480/ 620||1,250/ 1,700|
|Electric motors: power, kW||60||100||120||200|
|Number of electric motors||1||1||2||1|
|Amplitude of vibrations (without pile), mm||20||36||36||50|
|Mass of vibratory pile driver (without driving cap and control panel), kg||4,560||7,200||8,000||15,600|
The SP-42B vibratory pile driver is intended for driving reinforced concrete piles with cross sections of 30x30 and 35x35 cm weighing 2 tons, steel piles (I-beams Nos. 45-55), and "Larsen IV" and "Larsen V" sheet piles into weak, water-saturated soils. This machine is an improved model of the previously produced VP-1 vibratory pile driver . This vibratory pile driver consists of an electric motor, a vibration exciter whose welded body contains two pairs of shafts with unbalanced weights loads (eccentrics), and a removable hydraulic driving cap. A three-phase vibration resistant VMT-6 electric motor with a wound rotor is attached to the upper plate of the vibration exciter. It transmits rotary motion to the unbalanced shafts through rack and pinion gears. Pinion gearing provides synchronization of the rotary motion.
The vibratory pile driver is outfitted with two types of hydraulic driving caps: one for driving reinforced concrete piles and one for driving the metallic elements mentioned above. The side surface of the vibratory pile driver has two pairs of grips for suspending the vibratory pile driver on pile driver masts (for masts with guides that are 625 mm wide).
The VI-722 vibratory pile driver is designed for driving reinforced concrete piles with a cross section of 40x40 cm and tubular piles up to 1 m in diameter weighing up to 20 tons into class B soil (according to the classification in 'Edinye normy i rastsenki na stroitel'nye raboty' [Unified Standards and Estimates in Construction Work]).
The mechanical diagram of the Vl-722 vibratory pile driver (Figure 4.16) is similar to that of the VP-3M, but it differs from the latter in that it has two VMT-6 vibration resistant electric motors that transmit rotary motion to the unbalanced shafts through a chain coupling, a reduction gear, and a system of gear wheels. The use of a reduction gear makes it possible to produce two rotational frequencies of the unbalanced shafts (437 and 556 rpm).
Figure 4.16. The VI-722 two-frequency vibratory pile driver.
The driving cap (see figure 4.17) is attached to the lower plate of the vibration exciter by means of bolts and it is actuated by a hydraulic station attached to its upper plate. The hydraulic station has two gear-type pumps (both with clockwise or both with counterclockwise rotation). The working fluid is fed into the one cavity or the other of the hydraulic cylinder when the rotation of the electric motor of the hydraulic drive is reversed (3-kW squirrel-cage induction motor).
Figure 4.17. Diagram of wedge-type driving cap of vibratory pile driver.
The driving cap for tubular piles differs from the driving cap for square piles only in the number of wedges. The former has six wedges and the latter has four. The wedges clamp the driving cap to the pile when they move downward along the slanted guides of the welded casing of the driving cap and release the pile when they move upward. Movement of the wedges (1) (figure 4.17) is accomplished by hydraulic cylinder (2) by way of lever (3) and elastic coupling (4).
The most powerful vibratory pile driver produced in the USSR and abroad is the VPM-170 vibratory pile driver (technical data presented in Table 4.23). Its vibration exciter has eight unbalanced shafts arranged in pairs in four vertical tiers (figure 4.18). The unbalanced shafts are put into rotational motion by a series-produced electric motor (the AK-113-8M) through a set of pinions and a rotational frequency switching unit that makes it possible to have two eccentric rotational frequencies and two different force values. The second (from the bottom) row of pinions in the gearing with the unbalanced shafts there are two synchronizing pinions that make it possible to connect two or more vibratory pile drivers in series and to synchronize their operation.
Figure 4.18 The VPM-170 Low-Frequency Vibratory Pile Driver
The VPM-170 vibratory pile driver is designed for driving tubular piles 1.6 meters in diameter into any type of soil (except rocky soil) without removing the soil from the cavity of the pile. The pile driver is started up from the control panel, which can change the rotational frequency from 0.5 times the rated value to the rated value (according to the name plate) and it can allow the electric motor to operate at a reduced rotational frequency for a limited amount of time.
The vibratory pile driver is connected to the pile by a special adapter, the upper part of which is attached to the bottom plate of the pile driver and the lower part of which is attached to the tubular pile by nuts and bolts. The VPM-170 is not designed for use with hydraulic driving caps or ASN-type driving caps.
Of particular interest among vibratory pile drivers is the VU-1.6 (manufactured by Mintransstroi). It is designed for driving reinforced concrete tubular piles measuring 1.6 m in diameter to depths of up to 30 m while, at the same time, working and removing the soil from the cavity of the tubular pile (figure 4.19). These joint operations, which significantly increase productivity, are possible because the body of the pile driver has a through-hole 1.4 meters in diameter, so that the soil can be removed without removing the pile driver. This vibratory pile driver has a welded steel body with a cylindrical opening in the center. Inside the body there are four symmetrically arranged shafts with eccentrics that are connected to one another by conical synchronizing pistons on the ends of the shafts. Each pair of shafts is caused to rotate by an electric motor through a reduction gear with cylindrical pistons. Opposite shafts rotate in opposite directions, as a result of which the vibratory pile driver produces vertical vibrations.
Figure 4.19. The VU-16 vibratory pile driver.
|Eccentric value, kg-cm||34.5|
|Frequency, vibrations per minute||495|
|Dynamic force, kN||958|
|Power of electric motor, kW||150|
|Mass of vibratory pile driver(without driving cap and control panel), tons||11.7|
The electric motors are at the top of the housing and are attached to it by bolts. A conical adapter ending in a flange is welded onto the bottom plate of the vibration exciter's housing. For connecting the vibratory pile driver to the tubular pile, the protruding reinforcement bars must be threaded. The vibratory pile driver is mounted on the end of the pile in such a way that the ends of the rods enter the openings of the flange. The soil is worked and removed from the cavity of the tube by a special grab and hydromechanical methodwashing out the soil with a hydraulic excavator and removing it with a hydraulic elevator. The vibratory pile driver has a control panel similar to that of the VPM-170.
Foreign firms produce vibratory pile drivers for metal tubes, sheet piles, and cylindrical and prismatic reinforced concrete piles. In general, the main parameters (force, power, vibrational frequency, mass) are similar to those of vibratory pile drivers manufactured in the USSR. They also differ little in design from the latter.
Foreign firms make frequent use of hydraulic driving caps with the pumping station on the ground or on the pile driver. Many designs use standardized units, making it possible to increase their power by combining several (up to four) vibratory pile drivers into a single unit. Without exception, all are mounted on the crane by means of a spring shock-absorber.
In recent years vibratory pile drivers have been put to their greatest use in Japan, where six firms produce 55 models and variations of these models. The greatest number of vibratory pile drivers (21 models) is produced by the firm Kensetsu Kikai Chosa. Their technical data is presented in Table 4.24.
|Eccentric value, kg-cm||0.17||0.292||0.69||1||1.32||2.1||2.5||3.5||5||12||12|
|Frequency, vibrations per minute||1250||1300||1200||1100||1250||1100||1150||1100||1100||510||510|
|Dynamic force, kN||30||54||110||135||232||283||370||486||676||349||349|
|Vibrational amplitude (without pile), mm||4||4||6||6||7||7.5||8||9||9||21||22|
|Necessary power input, kW-A||10||20||45||80||100||120||150||200||250||250||250|
|Eccentric value, kg-cm||15||17||10||25||50||1||1.5||2.2||3||4.5|
|Frequency, vibrations per minute||400||560||1100||620||620||1500||1500||1500||1500||1700|
|Dynamic force, kN||40||60||135||107||214||25||37||55||75||145|
|Vibrational amplitude (without pile), mm||25||26||12||33||32||4||5||4||5||2|
|Necessary power input, kW-A||250||450||600||600||1200||100||150||200||250||400|
Let us examine the most typical design for vibratory pile drivers manufactured by the Mitsubishi Company (Table 4.25). The VD-22 vibratory pile driver (Figure 4.20) is designed for steel sheet piles and for metallic piles and tubes measuring up to 300 mm in diameter.
Figure 4.20 The Mitsubishi VD-22 Vibratory Pile Driver (Japan)
|Eccentric value, kg-cm||0.878||1.314||2.308||3.183|
|Frequency, vibrations per minute||1150||1150||1100||1100|
|Dynamic force, kN||130||145||315||431|
|Vibrational amplitude (without pile), mm||4.6||5.6||6.4||6.9|
The vibration exciter consists of three electric motors arranged on the same vertical axis in the steel housing. The rotor shafts have eccentrics and the eccentric value of the middle shaft is twice as great as the end eccentrics, so that when the end eccentrics rotate in one direction and the middle one in the opposite direction, vertically directed vibrations are produced. The vertical arrangement of the vibratory pile driver is convenient for driving (or extracting) piles in foundation pits or sheet piling. The VD-22 vibratory pile driver may be used with mechanical or hydraulic driving caps (a mechanical driving cap is shown in Figure 4.20).
Technical data on vibratory pile drivers manufactured by other Japanese firms is presented below (Tables 4.26, 4.27, and 4.28).
|Eccentric value, kg-cm||0.035||0.08|
|Frequency, vibrations per minute||1300||1300|
|Dynamic force, kN||15||40|
|Vibrational amplitude (without pile), mm||20||20|
|Eccentric value, kg-cm||0.845||1.295||1.727||2.2||2.6||3.5||4.6|
|Frequency, vibrations per minute||1100||1100||1100||1100||1100||1100||1100|
|Dynamic force, kN||114||175||234||298||352||474||622|
|Vibrational amplitude (without pile), mm||6.5||6.3||7||7.1||7.7||8.1||7.7|
|Power of electric motor, kW||15||22||30||40||50||60||90|
|Eccentric value, kg-cm||0.076||0.095||0.095||0.095||0.25||0.25||0.5||0.8|
|Frequency, vibrations per minute||1800||1500||1600||1600||1600||1600||1380||1380|
|Dynamic force, kN||13||35||35||35||56||56||110||120|
|Vibrational amplitude (without pile), mm||12||15||15||15||17||17||20||25|
|Power of electric motor, kW||3.3||4.4||4.4||4.4||5.9||5.9||10.3||16.2|
Beginning in 1978 the Japanese firms Mikasa Sengyo and Yamada Kikai Koyo began manufacturing vibratory pile drivers powered by internal combustion engines. Mikasa Sengyo produces two models of light vibratory pile drivers with a power of 5.9 kW that have internal combustion engines with a carburetor (see Table 4.27).
Table 4.29 shows data on vibratory pile drivers manufactured in the Federal Republic of Germany and in the United States.
|Menck, FRG||Foster, USA|
|Dynamic Force, kN||440||1,120||500|
|Frequency of vibrations/min||3,000||1,120||890/1,500|
|Mass of vibratory pile driver (without driving cap,) tons||3.9||18.1||4.13|
|Length of reinforced concrete pile, m||-||20||15|
|Length of metal pile, m||20||25||20|
MON-type vibratory pile drivers are high-frequency machines and are designed for driving and extracting metallic tubes 150 to 300 mm in diameter. They are used together with cranes or with drivers of similar capacity.
Yamala Kikai Koyo manufactures eight models of vibratory pile drivers with 4.5 to 22 kW internal combustion engines. The most powerful of these are powered by diesel engines (see Table 4.28).
The GKN Company (England) produces a vibratory pile driver designed for driving reinforced concrete piles and metallic piles with a 368-kW diesel. The vibratory frequency of this pile driver is 60 to 130 Hz, the force is 10 MN, and the mass is 10 tons. Regulation of the vibrational frequency makes it possible to achieve optimal driving under various soil conditions.
According to the method of O. A. Savinov and A. Ya. Luskin, the characteristics of a vibratory pile driver may be calculated in the following manner.
For a given maximum insertion depth, the total calculated critical resistance to failure for piles is:
for sheet piles:
|Type of soil||tcr, kPa||t'cr, kN/m|
|Wooden piles, steel tubes||Reinforced concrete piles||Reinforced concrete tubular piles, open at the bottom, inserted with excavation of soil||Light profile sheet pile||Heavy profile sheet pile|
|Water-saturated sandy and slightly plastic clayey soils||6||7||5||12||14|
|Same, but with layers of thick clay or gravely soils||8||10||7||17||20|
|Only slightly plastic clayey soils||15||18||10||20||25|
Same, semi-hard and hard
The eccentric moment of the vibratory pile driver's eccentric masses is:
|Sandy soils||Clayey soils|
|Vibration frequency, per minute|
Steel sheet pile, steel tubes with open end, and other elements with cross-sectional area up to 150 cm2
|Wooden and tubular steel (with closed end) with cross-sectional area up to 800 cm2||-||10-12||6-8||-||12-15||8-10|
|Reinforced concrete, square or rectangular cross section with area up to 2,000 cm2||12-15||-||-||15-20||-||-|
Reinforced concrete tubular piles with large diameter, inserted with excavation of soil from tube cavity
The frequency of vibrations (angular velocity of the eccentrics on the vibration exciter) is:
The minimum mass of the vibratory pile driver is:
For piles inserted into water-saturated sandy and slightly clayey soils, the following values are recommended for the required pressure p0 (MPa) :
After the main characteristics are obtained, the required power of the motors is determined:
The power (in kw) spent on overcoming resistances in the vibration exciter mechanism is:
The power (in kW) required to overcome the resistance of the ground is:
Since the derivation of the formula did not take into account energy losses to vibration of the ground, it is recommended that, in every case, the value of Nmax obtained by this formula be increased by 10 to 20 percent.