Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~X9glS~
DS23-1386-2ll
The present inverltiorl relates to a method for
pneumatically discharging hydromechanically conveyed hydraulic
building material for undergrourld operations. The inventiorl also
relates to an apparatus for carrying out this method.
Hydraulic building materials which are used undergrourld
are substances with consisterlcies ranging from grar,ular to
powderized and having different water/solid factors, which are
frequently processed with aggregates of synthetic material or
fiber mixtures, among other things, during gunning. The inverltior
relates in particular to gun-applied concrete made of these
materials, or gun-applied mortar, which in turn is applied several
centimeters thick to the stone walls of underworkillgs, in
particular of drifts, leaving o~lt the floor, as soon as possible
after the roof fall has been WOII, for example by blasting, in
order to increase the self-supporting capacity of the surrounding
ground. In addition to this roof fall protection when driving
rooms in mining and tunrlel constructiorl, the inventive method also
serves the purpose of sealing fire and ventilation dams and
smoothing walls in order to reduce air resistance, as well as for
timbering in general. Activator, which is preferably liquid, may
be added to the building material in the interests of early
strength, in order to guarantee optimal bearing capacity after as
short a time as possible to keep down the convergerlce of the rock
stratification, among other things.
The hydromechanical conveyance of the wet building
material, in particular in the form of mortar or concrete, is
advantageous as compared to dry conveyance, which is also known,
in the case of which the necessary mixing water and possibly the
activator are added to the building material at the end
ca~f
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of the pipeline, in that -the applied layers have a uni
form composition in accordance with a given recipe, which
eliminates the fluctuations in the solidity of the applied
layers ~esulting from uneven composition of the building
5 material and uncon-trolled addition of water. The inven-
tion therefore assumes a previously known method by which
the building material is discharged by aid of a mouth
piece, provided with a nozzle, of a conveying pipeline or tube
assembly acted upon by a pump, and gunned onto the surface to
be coated.
In the case of the previously known apparatus, the building
material is conveyed hydromechanically in the axial direction
of the nozzle. A short distance before the nozzle, com-
pressed air is added to the hydromechanically conveyedstream via nozzle channels arranged radially in the mouth
piece. The resulting acceleration of the building material
is subject to limits, however. For the nozzle device must
take the limited compressibility of the wet building material
into consideration due to the danger of clogging. The hydro-
mechanical conveyance of the building material has an aggra-
vating effect on this when the building material, for e~am-
ple due to the reduced friction in the conveyor pipe, is
conducted in the latter with a relatively large cross-
section and cannot be supplied simultaneously by a distri-
butor to a number of discharge pipes or tubes. For in such
cases the hydromechanically conveyed stream must also be
reduced to a smaller cross-section at the mouth piece,
which is determined by -the handling of the mou-th piece with
the necessary strength of an operator, provided manipula-
tors or monitors cannot be used.
Since, regardless of these difficulties, the activator is
preferably added only at the last minute due to the danger
that the hardening building material might interfere with
the paths of hydromechanical conveyance, this is done with
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DS23-1386-211
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one or more nozzles at the end of the hydromechanical conveyance
path~ However, this means that the activator does not mix
completely and homogeneously with the hydraulic building
material. The produced layers are therefore in-homogeneous where
the required early strength is not attained. Furthermore, there
are also losses of activator liquid which is then carried along by
the radially directed air blast and leads to concerltratiorls of
noxious substarlces in the atmosphere.
This, along with other causes, may lead ~o rebound
losses, i.e. a percentage of discharged building material which
does not stick, but falls down. It is true that the percentages
ranging from 30% to 40% which are usual in dry methods are not
reached by the wet methods, but the quota of the latter has
different causes. It depends, among other things, on the adhesive
power of the building material, the angle of impact of the
building material stream discharged from the mouth piece, and
similar parameters. In particular, the systematic changes in the
supporting capacity of the substratum hit by the gunned building
material constitute one of the most important causes for
rebounding. For regardless of the force of impact, for example,
on a rock surface, the resistance of the substratum changes in the
course of the application of the gunning layer and is generally
lower the more the applied layer thickness increases. The early
strength of the building material thus plays as much of a part in
this connection as the quantity of building material discharged in
each particular case. But the known apparatus does not allow for
any control of the speed of impact or any use of activator to
avoid excess rebound losses, at least not to the necessary extent.
The method of the present invention is based on the known
scheme for applying hydraulic building material in underground
operations, namely pumping the material through a conveying
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pipeline and gunning it from a nozzle onto the surface to be
coated. With the present method, this is achieved in such a way
that it can be better controlled, and in particular, offers the
possibility of achieving higher economy while sparing the
atmosphere. Further, the applied layers of building material are
made more effective with the use of activators, and the new method
also provides the conditions necessary for reducing systematic
rebound losses that were a problem with prior application methods.
According to one aspect to the invention, there is
provided a method for pneumatically discharging hydromechanically
conveyed hydraulic building material for underground operations,
compressed air being supplied to the wet building material, pumped
in a dense stream, in front of a mouth piece serving the discharge
thereof and having in particular a nozzle shape, the compressed
air being gunned out together with the building material,
characterized in that the compressed air stream is a turbulent air
stream and the dense stream of the pumped building material is
added to the compressed air supplied in a stream, sealed off from
the outside air by the wet building material, the dense stream
thereby being distributed in the compressed air stream and
conveyed along with the latter to the mouth piece and discharged
therefrom.
According to a further aspect of the present invention,
there is provided an apparatus for carrying pneumatically
discharging hydraulic building material comprising a mouth piece
mounted on a conveyor pipeline of a hydromechanical conveying
system for discharging gunned concrete or gunned motor onto the
stone walls of underworkings, the mouth piece forming the end of a
pneumatic conveying pipe, the end of which opposite the mouth
piece is closed and provided with a compressed air inlet which
adapted to generate turbulence in the air stream passing
therethrough and in that the mouth piece has between the
compressed air inlet and the mouth piece a lateral pipe outlet
into which the conveyed pipeline or tube assembly opens.
According to another aspect of the present invention,
there is provided a method wherein building material is supplied
to a conveying air stream in such a way that the dense stream of
the building material is divided up and the resulting building
material particles are accelerated in such a way that they remain
suspended in the conveying air stream. This conveying air stream
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containing the building material in a density dependent, on the
one hand, on the air speed and air quantity, among other things,
and, on the other hand, on the quantity to be conveyed, can be
discharged at the mouth piece without any danger of clogging, and
may also be constricted in the case of nozzle-shaped mouth pieces
and thus discharged at an increased speed which essentially
depends upon the quantity of compressed air when the cross-section
and quantity being conveyed are given. On the other hand, the
breaking up of the dense stream in which the building material is
hydromechanically conveyed leads to an enlargement of the free
building material area, which in turn offers favourable conditions
for improving the inclusion of an activator, if used.
The invention thus offers the advantage of causing an
essential reduction of the weight to be manipulated at the mouth
piece and of discharging the building material in a loosened
state, thus favoring an even distribution of the building material
on the particular substratum and thereby causing a considerable
reduction of rebound losses. The breaking up of the dense stream
by means of the compressed air stream does not have any
detrimental consequences for the building material because this
process, insofar as it leads to a demixing of the building
material, is revoked during impact. The air consumption is kept
within tolerable limits because the resulting pneumatic conveying
path is limited to the mouth piece and is relatively short.
With the improved method, it is possible to introduce
activators into the compressed air stream before it is mixed with
the dense stream of building material. The distribution of the
activator in the compressed air stream, in particular, its
atomization in the air stream, leads to a considerable increase in
the number of activator particles, thereby accordingly increasing
the probability than an activator particle meets a building
material particle due to the relative speed of these particles
resulting from the addition of the dense stream. This allows for
a considerable reduction in the amount of activator used while at
the same time obtaining a considerable improvement in the
effectiveness of the activator.
This effect, which is desirable not only from the point
of view of an economical use of activators, but also in view of
the distribution of the building material particles in the
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conveying air stream, which should be as even as possible, can be
reinforced by generating a turbulent compressed air stream. The
turbulence of the compressed air stream can also contribute to
increasing the density of the building material in the conveying
air stream, thereby reducing the quantity of compressed air
necessary for discharging the building material.
Preferably the compressed air stream and the dense stream
intersect one another at an angle ranging from an acute angle to
90. This considerably increases the relative speeds of the
building material and compressed air, as opposed to the axial
supply of the dense stream, so that the separation of the building
material and the distribution of the resulting particles in the
conveying air stream takes shape more favorably.
The velocity of the discharge can be adjusted by the flow
control valves which are provided in the air stream. This allows
for a reduction in the rebound losses, which up to now have
increased disproportionately quickly, for systematic reasons, when
the layer thickness increases. The reduction of the conveying air
stream allows the pumps used for hydromechanical conveyance, which
is usually designed as a reciprocating pump but occasionally as a
spiral pump, to work evenly with the given quantity to be conveyed
but the quantity and speed of the building material contained in
the impinging gunning stream can still be adapted.
It has been found that if the conveying air stream is
constricted after the air stream is mixed with the dense stream,
and thereafter the mixture is expanded, the building material will
be accelerated as it is discharged from the end of the
hydromechanical conveying pipe from its relatively low speed to
the considerably higher pneumatic conveying speed, and preventing
sedimentation of synthetic material.
The reaction time required by one or more additives to
the conveyed concrete to take effect, is of varying length
depending on the additive. This reaction time must be
sufficiently long. On the other hand, it must not exceed a
certain period because otherwise the tendency to clogging is
increased disproportionately. By selecting an appropriate length
of the discharge pipe and an appropriate reduction, the reaction
time can be predetermined.
1299152
The details, further features and other advantages of
the invention can be found in the following description
of embodiments of an apparatus suitable for performing
the above method, with reference to the figures in the
drawing. These show:
Fig. 1 a schematic and cut~off view of the construc-
tion of a mouth piece according to the inven~
tion,
Fig. 2 a modified embodiment of the invention viewed
according to Fig. 1,
Fig. 3 an embodiment of the invention modified further,
viewed according to Figs. 1 and 2,
Fig. 4 a variant of the embodiment according to Fig.
3,
20 Fig. 5 a further variant of the embodiment accorqing
to Figs. 3 and 4,
Fig. 6 a schematic side view of the compressed air
delivery in a mouth piece according to the
invention,
Fig. 7 a modified embodiment of the invention viewed
according to Fig. 1,
0 Fig. 8 an embodiment modified further with respect to
the view in Fig. 7,
Fig. 9 a further embodiment of the compressed air
delivery viewed according to Fig. 6,
Fig. 10 a modified embodiment of the compressed air
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delivery viewed according to Figs. 6 and 9~,
and
Fig. 11 an embodiment further modified, viewed accor-
ding to Figs. 6, 9 and 10.
Mouth piece 2 shown in Fig. 1 is located on the end of
a conveyor pipeline 3 of a known hydromechanic conveyor
system for gunned concrete, the details of which are not
reproduced here, the system being shown schematically
at 4. Mouth piece 2 is screwed by aid of an annular
flange 5 onto matching annular flange 6 of conveyor
pipe 3, a tube connector being located between pipe 3
~shown cut-off) and a stationary conveyor pipeline.
Mouth piece 2 consists of a T-shaped pipe, the verti-
cal part of which is formed by a section of pipe 7
exhibiting flange 5 and branching off at right angles
to pipe 8, which is narrower by comparison, of the
mouth piece. Pipe 8 is connected by flange 9 to a cor-
responding flange 10 of a nozzle 11, out of which the
building material emerges in accordance with arrows 12.
At the opposite end, a compressed air connection 15 is
connected by aid of a flange 14 to a matching flange 15'
of pipe 8. The details of the compressed air connection
15 can be seen in the view of Fig. 6.
The compressed air supplied at 16 then enters a tubular
chamber 17, first passing blades 18 of a control device
19. These blades generate angular momentum followed by
turbulence in the air stream, which is indicated by
arrows 20 in the figures.
A further pipe 21 is attached concentrically in tubular
chamber 17, the front end of this pipe 21 being provided
~299~52
with a conical seal 22 protruding beyond control dev~ce
19. The conical seal has several openings 23, 24 on its
conical surface, through which a preferably li~uid acti-
vator can penetrate. The conical seal is generally
equipped in practice with high-pressure atomizing noz-
zles for liquid activators.
According to the view in Fig. 1, the compressed air is
supplied via a connection piece 25 with blockage and
control unit 26 in accordance with arrow 27. The ac-
tivator is also supplied to pipe 21 via a connection
piece 28, a blockage and control unit 29, in accordance
with arrow 30.
In operation, a reciprocating pump continuously deliv-
ers building material 4 consisting of a hydraulic sub-
stance whose consistency ranges from granular to pow~erized
water, sand 31 and aggregates 21, through connection
piece 7 into pipe 8. The extremely turbulent compressed
air stream following control device 19 carries along the
activator penetrating through openings 23, 24, distribu-
ting it in a form ranging from mist to drops over the
entire clear opening of pipe 8. Building material 4 is
added to this turbulent compressed air stream in accor-
dance with the hydromechanical conveyance at the openingof connection piece 7. At the same time the compact
stream is broken up and separated into particles which
are kept in suspended distribution in the compressed
air stream. The building material particles carried
along by the stream reach nozzle 11 and are discharged
by same in accordance with arrows 12. In free flight
they cross the distance to a surface (stone surface),
on which they settle down in the form of an uninterrup-
ted layer.
According to ~he embodiment of Fig. 2, pipe section 7
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and flanged pipe 3 are not arranged at right an~les, but at ar,
acute arlgle to the pipe. This ~avors the hydromechar,ical
conveyance by reducing supply resistance, ar,d may therefore have a
favorable effect under certain circumstances.
According to the view of Fig. 3, the cross-section of
mouth piece pipe 8 is reduced behind the opening of pipe section 7
by a stationary plate, the baffle plate of which is shown at 38.
This baffle plate COJIsists of a weir limited by the circular
walling of the pipe, the edge of the weir exhibiting a rour,d
inside surface 39. Baffle plate 38 creates a cross-sectional
reduction restricting the compressed air stream 40, whereby
turbulence which favors the separation of dense stream 41 through
pipes 3 ar,d 7 comes about additionally on surface 39. Some of
this turbulence is shown schematically at 42.
The embodiment according to Fig. 4 uses, instead of the
disk shape of baffle plate 38, a plate 43 with a trapezoidal
cross-section in order to counteract sedimentation in its
turbulent region.
This tenderlcy is counteracted even more by the embodiment
according to Fig. 5, because here the cross-section of plate 44 in
nozzle pipe 8 exhibits a bulge 45 on which conveyirlg air stream
46, which forms following the opening of pipe 7, is accelerated.
In the embodiment according to Fig. 7, an adjustable
baffle plate 38 is displacable in the cross-section of nozzle pipe
8 in the direction of double arrow 36 that is the direction of
pipe section 7 by aid of a regulating device 47. This results in
the possibility of setting up an adjustable aperture 48 in the
pipe 8 which the conveying air stream must go through immediately
following the opening of pipe 7. Such an adjustable plate 38'
allows mouth piece 2 to be adjusted to accommodate different
compositions of building material, such as different water/solid
factors.
e~
129~152
In the embodiment according to Fig. 8, a telescopic pipe
49 displaceable in pipe 7 is used instead of an adjustable plate
38' to adjust the cross-section of the aperture 48 in nozzle pipe
8. The telescopic pipe 49 forms the extension of pipeline 3,
which may be axially displaced and adjusted in pipe 7 by aid of an
annular adjusting device 50. A seal 51 seals off the casing of
pipe 49, preventing compressed air of compressed air stream 40, or
conveying air stream 46 in mouth piece pipe 8, from escaping from
the nozzle. The axial adjustability of telescopic pipe 49 makes
it possible to alter the cross-section of aperature 48 in a
particularly easy manrler. Furthermore, pipe 8 has a multi-part
design in the view of Fig. 8, consisting of pipe sections 52, 53
and nozzle 54. This means that not only flanged nozzle 54 can be
removed, but also the following pipe 53, which makes it
considerably easier to remove clogs and service mouth piece 2.
In operation, both the quantity of activator may be
controlled, by blockage and control unit 29, and the guantity of
compressed air, by blockage and control unit 26. The supply of
compressed air may be controlled via control unit 26 in such a way
that the speed at which the conveyirlg air stream at 12 is
discharged may be slowed down in accordance with the constructior
of the layer.
The additives, in particular activators, added to the
hydraulic building material being conveyed are frequently
contaminated. In many cases the additives may be inhomogeneous.
When relatively large quantities of such additives must be
conveyed, clogging often occurs. According
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129~15Z
- 12 -
to the view in Fig . 9, compressed air connection 15 is
provided for these circumstances and exhibits a stationary
piston 56. Piston 56 has a reduced portion 59, which
exhibits a connection 60 for the supply of additive on the
outside. The reduced portion has a hollow design, the
cavity continuing into piston 56, as shown at 63. ~adial-
ly oriented cross bores 61, 62 open out into parallel
air channels 57, 58, which are acted upon by the compressed
air supplied at 16, the stream of which is thereby sepa-
rated into several different streams. In this manner,relatively broad flow channels may be realized for the
additive without any possibility of the additive and the
air stream being insufficiently mixed. For the additive
is introduced into the turbulent air stream via radial
cross bores 61, 62.
In many eases it is also necessary to introduce more than
one additive, whereby the additives are inténded to be
combined only in the air stream. Embodiments of a com-
pressed air conneetion 15 with sueh a design are shownin Figs. 10 and 11.
Aeeording to Fig. 11, piston 56 has a eylindrieal design.
It eloses off a ehamber 70 of pipe 71 whieh forms the
eompressed air eonneetion. However, there are a number
of axial ehannels 57, 58 in piston 56 which correspond
to the design in the embodiment aeeording to Fig. 9.
The additive is supplied in the embodiment aeeording to
Fig. 10, however, at two plaees, i.e. via eonneetions 64,
65 and eross bores 66, 67, to the air stream divided up
into different streams in axial channels 57, 58.
A modified embodiment, which is shown in Fig. 11, also
has two eonneetions for additives, which are shown at
68 and 76. Connection 76 acts upon an axial channel whieh
arrives at a dead end at the above-described conical seal
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- 13 -
22 with openings 23 and 24. ~he further connection 68
supplies parallel channels 72, 73. The latter act upon
cross bores 74, 75 in piston 56, thereby supplying the
particular additive to air channels 70, 71, into which
the main air stream introduced at 16 is divided.
One or more additives can only take effect in the con-
crete material being conveyed after a reaction period
which depends upon the conditions of the particular case.
This results in the sojourn time of the concrete, which
is already mixed with the additives, being as long as
possible, but not too long, in the entire apparatus.
Under these circumstances, a mouth piece provided on a
tube has the advantage that it makes it possible to de-
termine the reaction time by means of the length of thetube and the rate of flow. A tube also has the advantage
that the gunning apparatus proper does not need to be
carried or handled, but only the much lighter replaceable
tube, in which the concrete is conveyed to the mouth piece
in the tunnel stream as described.
In order to realize the necessary length of tube, on the
one hand, and not to extend the sojourn time too long, on
the other, the speed of the concrete may he increased be-
fore the mouth piece. This is accomplished expedientlyby a discharge pipe or a discharge tube having a smaller
cross-section than the concrete inflow. Such a design
also has the advantage that extremely small quantities
of concrete may also be processed because the discharge
tube has a relatively small cross-section.
If the mouth piece is provided wïth a nozzle, the usual
conversion af pressure to speed takes place in the nozzle.
In case such an increase of speed is not required at the
discharge, the nozzle may be dispensed with.
