U.S. patent number 3,624,760 [Application Number 04/873,298] was granted by the patent office on 1971-11-30 for sonic apparatus for installing a pile jacket, casing member or the like in an earthen formation.
Invention is credited to Albert G. Bodine.
United States Patent |
3,624,760 |
Bodine |
November 30, 1971 |
SONIC APPARATUS FOR INSTALLING A PILE JACKET, CASING MEMBER OR THE
LIKE IN AN EARTHEN FORMATION
Abstract
A jacket member is placed over a bar which forms a mandrel and
is acoustically coupled thereto by means of adjustable couplers at
a plurality of points therealong. A sonic oscillator of the
orbiting mass type is coupled to the mandrel and driven at a
frequency such as to set up resonant standing-wave vibration of the
mandrel. Sonic energy is thus coupled to the jacket and in turn
into the earthen formation into which the jacket is to be
installed, thereby fluidizing the earthen material and causing the
jacket to be driven into the ground.
Inventors: |
Bodine; Albert G. (Van Nuys,
CA) |
Family
ID: |
25361350 |
Appl.
No.: |
04/873,298 |
Filed: |
November 3, 1969 |
Current U.S.
Class: |
175/56;
175/171 |
Current CPC
Class: |
E02D
7/30 (20130101); E02D 7/18 (20130101); E21B
7/24 (20130101) |
Current International
Class: |
E21B
7/24 (20060101); E21B 7/00 (20060101); E02D
7/18 (20060101); E02D 7/00 (20060101); E02D
7/30 (20060101); B06b 001/10 (); E21b 005/00 () |
Field of
Search: |
;175/19,22,23,56,171 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Claims
I claim:
1. In combination,
an elastic bar member,
a jacket member surrounding said bar member,
sonic oscillator means coupled to one end of said bar member, said
oscillator means being driven at a frequency such as to set up
resonant standing-wave vibration in said bar member, and
means for acoustically coupling said bar member to said jacket
member at a plurality of predetermined spaced points therealong, so
as to rectify the sonic energy such that mainly unidirectional
pulses of such energy are transferred to said jacket member.
2. The device of claim 1 wherein said bar member is a mandrel
having a plurality of successively stepped sections along the
length thereof, running between the oscillator and the end opposite
said one end thereof.
3. The device of claim 1 wherein said jacket member is corrugated,
each of said coupling means being positioned with an end thereof
longitudinally spaced from one of the jacket member corrugations to
form a rectifier gap therebetween.
4. The device of claim 2 wherein said jacket member is corrugated,
each of said coupling means comprising a bushing member removably
attached to the mandrel, each of said bushing members being placed
along said mandrel with one end thereof at a position where a pair
of said sections join, a rectifier gap being formed between said
one end of said bushing member and a corrugation of said
jacket.
5. The device of claim 4 and additionally including removal tip
means attached to the end of said mandrel opposite to the
oscillator-coupled end thereof for providing a predetermined
extension to the mandrel to adapt it to the length of the
jacket.
6. The device of claim 3 wherein each of said coupling means
comprises piston means mounted in said bar member for motion
radially thereof and means for driving said piston means to a
position spaced from an associated corrugation of said jacket
member so as to form said gap.
Description
This invention relates to the driving of jacket or casing members
into the ground and more particularly to the use of sonic energy
for implementing such driving action.
In the prior art, apparatus is utilized for forming piles in which
a mandrel, which may be tapered or stepped, has a thin steel jacket
placed thereover, the two members then being driven into the ground
together by means of a hammer drive. When the mandrel and jacket
are in position, the mandrel is then removed, leaving the steel
jacket in the ground, this jacket then being filled with concrete
to form a "cast-in-place" pile. The use of a tapered or stepped
construction has an advantage in this type of prior art device in
that is provides an optimum use of the steel in that the smaller
diameter lower sections of the jacket are held in the solider,
lower-down portions of the earthen formation, while a larger
diameter portion is provided closer to the surface where the
earthen formation is generally not quite as dense.
A considerable improvement in the efficiency of the driving action
of this type of device can be achieved by utilizing sonic energy to
fluidize the earthen formation and thus implement the driving
action. This type of sonic driving is described, for example, in my
U.S. Pat. Nos. 2,975,846 and 3,379,263.
The device of this invention is concerned with an improved
technique for coupling the sonic energy to the earthen formation by
transferring such energy from the mandrel to the jacket at a
plurality of optimum coupling points therealong, and in an optimum
manner, so as to provide higher efficiency in the utilization of
the sonic energy in driving the jacket member into position.
Further, in one embodiment of my invention, a stepped mandrel and a
correspondingly stepped jacket is utilized, the mandrel providing
heavy mass at one end for good impedance coupling to a relatively
large orbiting mass oscillator and a much lower mass at the
opposite driving end which thus has a high vibrational output for
optimum driving action. The device of the invention further
utilizes sonic rectification of the energy at its coupling between
the mandrel and the jacket to increase the efficiency of the
driving operation to assure its maximum utilization.
It is therefore the principal object of this invention to improve
the efficiency of the driving of a jacket or casing member into an
earthen formation.
Other objects of the invention will become apparent as the
description proceeds in connection with the accompanying drawings,
of which:
FIG. 1 is an elevational drawing indicating the general operation
of one embodiment of the device of the invention,
FIG. 2 is an elevational view in cross section illustrating the
details of construction of this first embodiment,
FIG. 3 is an elevational view with partial cutaway section
illustrating a coupling bushing member which may be used in the
embodiment of FIG. 1,
FIG. 4 is an elevational view with partial cutaway section
illustrating a removable tip portion which may be used in the
embodiment of FIG. 1,
FIG. 5 is an elevational view in cross section of a second
embodiment of the device of the invention, and
FIG. 6 is a cross-sectional view taken along the plane indicated by
6--6 in FIG. 5.
Briefly described, the device of the invention comprises a mandrel
member over which is placed a relatively thin-wall elastic jacket
member. The jacket member is coupled to the mandrel member at
several spaced points therealong. An orbiting mass oscillator is
coupled to one end of the mandrel member and driven at a frequency
such as to set up standing-wave resonant vibration therein, the
coupler points between the mandrel and the jacket preferably being
spaced to provide optimum overall energy utilization. The jacket
and mandrel are placed in the ground, the sonic energy causing
these members to be driven therein. In one embodiment of the device
of the invention, the mandrel and jacket have a stepped
configuration, the driving end having a much smaller diameter than
the end being driven by the oscillator, thus providing optimum
coupling between the oscillator and the mandrel with an impedance
transformation being provided at the driving end to provide optimum
coupling of the sonic energy from the driving tip to the ground.
The coupler members for coupling the sonic energy from the mandrel
to the jacket are adjustable so that they can be positioned for
optimum transfer of energy from the jacket to such mandrel. A
special tip attachment is provided to adapt the mandrel to various
lengths of jacket in the field. In addition, the couplers are
arranged so that they provide sonic rectification in the transfer
of the sonic energy from the mandrel to the jacket for optimum
utilization of this energy.
It has been found most helpful in analyzing the device of this
invention to analogize the acoustically vibrating circuit utilized
to an equivalent electrical circuit. This sort of approach to
analysis is well known to those skilled in the art and is
described, for example, in Chapter 2 of "Sonics" by Hueter and
Bolt, published in 1955 by John Wiley and Sons. In making such an
analogy, force F is equated with electrical voltage E, velocity of
vibration u is equated with electrical current i, mechanical
compliance C.sub.m is equated with electrical capacitance C.sub.e ,
mass M is equated with electrical inductance L, mechanical
resistance (friction) R.sub.m is equated with electrical resistance
R and mechanical impedance Z.sub.m is equated with electrical
impedance Z.sub.e .
Thus, it can be shown that if a member is elastically vibrated by
means of an acoustical sinusoidal force F.sub.o sin.omega.t
(.omega. being equal to 2 .pi. times the frequency of vibration),
that
Z.sub.m =R.sub.m + j (M- (1/C.sub.m ))=F.sub.o sin.omega. t/u (1
)
Where .omega.M is equal to 1 /.omega.C.sub.m, a resonant condition
exists, and the effective mechanical impedance Z.sub.m is equal to
the mechanical resistance R.sub.m , the reactive impedance
components .omega.M and 1 /.omega.C.sub.m cancelling each other
out. Under such a resonant condition, velocity of vibration u is at
a maximum, power factor is unity, and energy is more efficiently
delivered to a load to which the resonant system may be
coupled.
It is important to note the significance of the attainment of high
acoustical Q in the resonant system being driven, to increase the
efficiency of the vibration thereof and to provide a maximum amount
of power. As for an equivalent electrical circuit, the Q of an
acoustically vibrating circuit is defined as the sharpness of
resonance thereof and is indicative of the ratio of the energy
stored in each vibration cycle to the energy used in each such
cycle. Q is mathematically equated to the ratio between .omega.M
and R.sub.m . Thus, the effective Q of the vibrating circuit can be
maximized to make for highly efficient, high-amplitude vibration by
minimizing the effect of friction in the circuit and/or maximizing
the effect of mass in such circuit. The heavy, tapered pile gives
good Q. Moreover, the rectifier action also increases the energy
retention in the mandrel.
In considering the significance of the parameters described in
connection with equation 1, it should be kept in mind that the
total effective resistance, mass, and compliance in the
acoustically vibrating circuit are represented in the equation and
that these parameters may be distributed throughout the system
rather than being lumped in any one component or portion
thereof.
It is also to be noted that orbiting mass oscillators are utilized
in the implementation of the invention that automatically adjust
their output frequency and phase to maintain resonance with changes
in the characteristics of the load. Thus, in the face of changes in
the effective mass and compliance presented by the load with
changes in the conditions of the work material as it is sonically
excited, the system automatically is maintained in optimum resonant
operation by virtue of the "lock-in" characteristic of applicant's
unique orbiting mass oscillators. Furthermore in this connection
the orbiting mass oscillator automatically changes not only its
frequency but its phase angle and therefore its power factor with
changes in the resistive impedance load, to assure optimum
efficiency of operation at all times. This automatic adjustment to
load impedance works particularly well with the rectifier feature
of this invention. The vibrational output from such orbiting mass
oscillators also tends to be constrained by the resonator to be
generated along a controlled predetermined coherent path to provide
maximum output along a desired axis.
Referring now to FIG. 1, a first embodiment of the device of the
invention is illustrated. Mandrel 11 includes stepped sections 11a,
11b and 11c, which are fixedly joined together by suitable means
such as welding, or interference fit, to form a one-piece integral
unit. Mandrel 11 may be formed of cylindrical, thick-walled pipe of
a highly elastic material such as steel. Placed over the mandrel
sections 11a, 11b and 11c are thin-wall steel corrugated tubing
sections 12a, 12b and 12c, which form a jacket around the mandrel.
The jacket sections are coupled to each other by corrugated
couplings 14 and 15, as to be described in connection with FIG. 2.
The mandrel is coupled to the jacket, with rectifier action, by
means of adjustable or selected bushings 17 and 18, as shown in
FIG. 2 and later to be described in connection therewith. Suffice
it to say at this point that the couplings may be adjusted to
provide the rectified coupling (unidirectional portion of the
elastic displacement cycle) of sonic energy in an optimum manner
from the mandrel to the jacket.
An orbiting mass oscillator 16 has its casing attached to the top
end of mandrel 11 and is rotatably driven by drive means (not
shown) coupled to the oscillator through drive shaft 20. Oscillator
16 may be of the type described in my U.S. Pat. No. 3,379,263,
which utilizes a pair of eccentric rotors which are rotated in
opposite directions so that they produce vibration of mandrel 11
along the longitudinal axis thereof. The speed of rotation of
oscillator 16 is adjusted to a frequency whereat resonant
standing-wave vibration of the mandrel occurs. The resonant energy
is coupled from the mandrel through jacket 12 to earthen formation
25 to fluidize the formation thereby causing the mandrel and the
jacket to be driven therein.
Referring now to FIGS. 2-4, the details of construction of a first
embodiment of the device of the invention are illustrated. As
already noted, cylindrical corrugated steel jackets 12a -12c fit
over associated mandrel sections 11a -11c respectively. Jacket
section 12a is joined to jacket section 12b by means of cylindrical
corrugated coupler 14, which matingly engages the ends of these
sections in the manner of screw threads. Jacket section 12b is
similarly coupled to section 12c by means of coupler 15. Acoustical
coupling is provided between mandrel section 11a and jacket section
12a by means of adjustable or selected bushing coupler member 17,
the details of which are illustrated in FIG. 3. Bushing 17 includes
a cylindrical tapered spacer member 17a. The bushing may be held to
the mandrel in a desired position opposite shoulder portion 14a of
coupler 14 by means of the wedge action provided by collet 17b with
the tightening of screws 17d. Further holding action for retaining
the bushing to the mandrel is provided by setscrew 17c. Prior to
the time that jacket section 12a is placed over mandrel section
11a, bushing 17 is placed in the desired position for coupling
energy therebetween and attached to the mandrel in this position by
means of collet 17b and setscrew 17c. This adjustment should be
made to provide a small rectifier gap 19 between the jacket and the
mandrel so that only unidirectional pulses of sonic energy are
transferred to the jacket (i.e., the half-cycle of the sonic energy
which provides a downward pulse), the mandrel being substantially
uncoupled from the jacket on the upward vibratory excursion. The
device thus functions as a sonic rectifier, downward driving pulses
of sonic energy being provided from the mandrel to the jacket.
Bushing 17 should be positioned in place or dimensioned so that gap
19 is such as to afford optimum transfer of downward pulsating
energy. This gap has to be less than the longitudinal distance
traversed by the mandrel in an elastic half-cycle. Coupler bushing
18 is similarly adjusted in position for optimum coupling of
unidirectional sonic energy between mandrel section 11b and the
shoulder portion 15a of jacket coupler 15.
The frequency of oscillator 16 is adjusted to provide a
standing-wave pattern in the mandrel as indicated by graph lines
30. The resonant vibration as shown should be at a frequency
whereby any two of the coupling points, i.e., in this instance
those at coupler bushings 17 and 18, are spaced within a quarter
wavelength of the standing-wave pattern so that the sonic drives on
the jacket at these various points are in unison, thereby
minimizing the stress on jacket. A removable tip portion 37 is
utilized, various lengths of these tip portions being available for
installation at the end of the mandrel to match various lengths of
jackets so as to provide rectifier action as the need may arise in
the field. Tip portion 37, or any of the other joints in the
mandrel, may have a tongue 37a thereon which fits into cavity 38 in
the center portion of the adjoining portion of the mandrel, joinder
between the two members being attained by means of a tapered key 40
which fits through apertures in tongue 37a and mandrel 11c and is
held to the mandrel by means of bolt 42 and nut 43.
Several significant features of this first embodiment should be
noted at this point. First, the stepped mandrel structure provides
a heavy mass at one end for optimum coupling to a large massive
oscillator, and a much lower mass at the opposite end to provide an
effective step-up transformation of the vibration resulting in
high-amplitude vibration at the driving end, where it is most
needed. Secondly, the adjustable or selected bushings 17 and 18
provide means for adjusting the coupling between the mandrel and
the corrugated jacket to optimum rectifier advantage for each
particular installation requirement. Likewise, the use of a
removable driving tip enables the use of a tip member which
provides optimum driving. Further, the adjustment of the coupling
between the mandrel and the jacket through the adjustable bushings
to provide sonic rectification, i.e., vibrational drive only in the
downward direction, provides the advantages of minimizing the
stress placed on the jacket and further makes for better
utilization of the sonic energy in that it is not dissipated in an
upward loaded excursion, which provides no useful effect in the
driving action. The sonic vibrational system by virtue of the sonic
rectifier action is made to have a higher effective Q in view of
the fact that the ratio between the energy stored to the energy
dissipated in each vibrational cycle is thereby increased.
When the jacket has been installed in the desired position, the
mandrel is lifted out therefrom and the jacket filled with concrete
to form the piling.
Referring now to FIGS. 5 and 6, a second embodiment of the device
of the invention is illustrated. In this embodiment, the tapered
mandrel and jacket of the first embodiment are not used, the
mandrel being coupled to the corrugated jacket by means of a
plurality of specially designed coupler devices.
Mandrel 51 has a plurality of coupler units 53 installed therein at
spaced intervals therealong. Each coupler unit 53 may include three
piston units 54, slidably supported in radial cylinders 56 formed
in the mandrel. Pistons 54 are hydraulically actuated by
pressurized fluid fed through line 58 to channel 59 formed in the
center of the mandrel. With the pistons 54 unactuated, jacket
member 60 is placed over the mandrel. The pistons 54 are then
hydraulically actuated to drive them to the position indicated by
the dotted lines in FIG. 6, the radial travel of the pistons being
arrested by the abutment of piston shoulder 54a against shoulder
66a of retainer plate 66, which is fixedly retained in the mandrel.
The travel of piston 54 is thereby arrested as shown by the dotted
lines, in a position whereat there is a small gap between piston
head 54b and the inner wall of corrugated jacket 60 both radially
and longitudinally. This gap provides the rectifier gap necessary
to achieve the desired sonic rectification. Thus, with the
excitation of oscillator 16 at a frequency such as to cause
longitudinal resonant standing-wave vibration of mandrel 51, and
with pistons 54 in their extended position, unidirectional sonic
pulses are coupled from the mandrel to the corrugated jacket at the
longitudinal gaps formed between the piston heads and the adjacent
jacket corrugations. This second embodiment thus provides another
way of transferring unidirectional sonic downward driving pulses to
the jacket at several points therealong.
The device of this invention thus provides improved means for
acoustically driving a pile jacket in which unidirectional sonic
driving pulses are applied to the jacket in the driving direction
at several points therealong.
* * * * *