US3638754A

US3638754A - Pressure and sound shield for blast excavation of tunnels and the like

Info

Publication number: US3638754A
Application number: US98826A
Authority: US
Inventors: Edward J Sosnowicz; Frank M Willis
Original assignee: EI Du Pont de Nemours and Co
Current assignee: ETI EXPLOSIVES TECHNOLOGIES INTE
Priority date: 1970-12-16
Filing date: 1970-12-16
Publication date: 1972-02-01
Anticipated expiration: 1989-02-01

Abstract

An apparatus for attenuating pressure and sound comprising a frame mounted on motion-transmitting means, and a transverse barrier mounted on said frame, said barrier comprising a rigid core and a deformable sealing member completely surrounding the periphery of said core, said sealing member being extensible and retractable with localized radial variability, thereby giving the barrier a variable edge contour.

Description

UllllCu Olfdttn 1 alsuu. 3,638,754

Sosnowicz et a]. 51 Feb. 1, 1972 54] PRESSURE AND SOUND SHIELD FOR [56] References cm BLAST EXCAVATION OF TUNNELS UNlTED STATES PATENTS AND THE LIKE 3,397,756 8/1968 Andrews et a]. ..l8l/33.03 [72] Inventors: Edward J. Sosnowicz, Colwyn, Pa.; Frank M wuu Hedgesvme w FOREIGN PATENTS OR APHJCATIONS 73 Assi nee: E. I. du Pont de Nemours and C an 1,011,611 7/1957 Germanv... ..l8l/33.4 1 8 Wilmington Del. p 1 405,380 2/1934 Great Britain ..18i /33.1

[22] Filed: Dec. 16, 1970 Primary Examiner -Robert S. Ward, Jr.

An J. Fl 21 Appl. No.: 98,826 m [57] ABSTRACT 52 us. Cl. ..l8l/33 R 181/33 HE, 121/33 K, An apparatus f attenuating pressure and Sound comprising a 131/33 GB, 299/13 frame mounted on motion-transmitting means, and a trans- CL E210} 1 verse barrier mounted on said frame, said barrier comprising a [58] Field of Search ..l81 /33 R, 33.1, 33.12, 33.223, rigid core and a deformable sealing member completely surl8l/33.4, 36 R, 36.4, 30, 33.03; 299/13 rounding the periphery of said core, said sealing member being extensible and retractable with localized radial variability, thereby giving the barrier a variable edge contour.

11 Claims, 4 Drawing Figures SHEET 1 BF 2 PATENTEB FEB 1 i972 PATENTEU FEB 1 1972 SHEEY 2 BF 2 l 21 2 L 1 I 5 IF L [l L 1| L mgr-3 (25) 34%| Il- L Ii 2 0 22 1. 2- o o 380 I4 INVENTORS EWARD J.SOSNOWICZ FRANK ".WILLIS A ORNEY PRESSURE AND SOUND SHIELD FOR BLAST EXCAVATION OF TUNNELS AND THE LIKE BACKGROUND OF THE INVENTION This invention relates to'a conveyable, adjustable apparatus for attenuating pressure and sound, e.g., a blast shield, adapted to provide an intermittent seal in an opening or passageway such as a tunnel at different locations therein.

The energy released by the detonation of high explosives has long been utilized in excavation operations, e.g., in tunneling. The blasting technique requires that holes be drilled in a suitable pattern in a face in a geological formation such as rock, that each hole be loaded with a charge of detonating explosive, and that the charge in each hole be detonated, e.g., by actuation of a blasting cap in contact with the charge. in order to'safeguard personnel and equipment from the blast pressure and rock throw efiects resulting from the blast, it has been common practice to connect the initiating devices placed in contact with the charges (or with detonating cords leading to the charges) to a remotely located common actuating device such as a blasting machine, clear the immediate blast area of personnel and equipment, and energize the remotely located actuating device. With this type of operation, a considerable percentage of the time consumed in the excavation process is unproductive time, i.e., time when neither disintegration of the formation nor removal of disintegrated material from the excavation (mucking) to a disposal area is taking place. For example, drilling and drill-hole-loading equipment and personnel have to be moved up to the face from their protected locations, and moved back again prior to the blast; the blasting leads (cap leg wires, or lengths of detonating fuse or safety fuse) have to be connected to form the blasting circuit to the remote actuating device; and following the blast, after a ventilation period (smoke time") which is necessary to clear the airborne fumes and dust produced as a result of the blast, the mucking equipment has to be moved up and then moved back again prior to the next blast.

It now has become possible to perform the drill-and-blast excavation technique on a quasi-continuous basis by the use of the excavation machine and method described in our copending, coassigned application, Ser. No. 49,662, filed June 25, 1970, the disclosure of which is included herein by reference. This machine, which performs all of the operations required to advance a face by drill and blast while remaining stationed at the face, has the capability, in rapid sequence, of drilling and loading holes with explosives, and thereafter initiating the explosive by the delivery of energy thereto, and also of removing muck and airborne fumes and dust from the face and attenuating blast pressure and noise during the drill-load-blast sequences. The drilling, loading, and explosive initiation are performed by one or more drill-and-blast modules, e.g., of the type described in copending, coassigned application, Ser. No. 878,005, filed Nov. 19, 1969.

A drill-and-blast excavation machine, or any other apparatus employed in drill-and-blast excavation processes which remains stationed at the face during blast, requires the provision of a means of protection against damage by rock impact and blast pressure, both to the apparatus as well as to personnel if they are to be located at controls on or near the apparatus. Protection of the apparatus and, with sufiiciently small blasts, personnel as well may be achieved by means of self-shielding, i.e., armoring of the components of the apparatus and personnel cab, or common shielding in the form of a transverse barrier between the face and unannored components. ln order for the excavation process to be performed with maximum economy, however, i.e., with sufficiently large blasts, and with personnel located on or near the apparatus, shielding means is needed which is capable of reducing the blast pressure and attendant noise level encountered at the personnel station to within acceptable toleration limits. in other words, shielding apparatus is needed which is capable of (a) being conveyed through an excavated passage to a new location in the direction of each new face produced, (b) engaging the surrounding surface at each new location, and (c) sealing off the space ahead of the shielding apparatus from that behind it.

SUMMARY OF THE lNVENTlON This invention provides an apparatus for attenuating pressure and sound which comprises a frame mounted on motiontransmitting means, preferably power-driven, e.g., wheels, crawlers, tractor treads, or runners, and a transverse barrier mounted on said frame, said barrier comprising a. a rigid core having opposing top and bottom surfaces and an edge surface adjacent thereto, said core being mounted on said frame in a manner such that the top and bottom surfaces are substantially normal to the front to rear axis of the frame;

b. a deformable sealing member completely surrounding the periphery of said core, said sealing member being extensible and retractable with localized radial variability in a manner such that radial dimensions of said barrier are adapted to change and to differ from one another; and

c. means for holding the apparatus in place when in use.

Preferably, the core is divided into two or more segments, at least one segment being adapted to move in a manner such that an overall dimension of the core can be varied, e. g., pivoting of an upper segment with respect to a lower segment to vary the overall vertical dimension of a core mounted on end on a substantially horizontal frame.

A preferred deformable sealing member comprises a plurality of overlapping, extensible and retractable sectional components, such as adjacent flaps, arranged in an overlapping relationship, e.g., so as to constitute a multi-ply layer, the flaps being secured to pivotal hinge plates for adjustment.

The term core" as used herein to describe the rigid member of the barrier refers to a central structural member which is platelike in its general overall form. That is, this member, like a plate, has two opposing boundaries of large dimension(s) relative to the dimension normal thereto, i.e., the thickness dimension. The large-dimensioned boundaries are the top and bottom surfaces of the core, and the surface or surfaces adjacent to these boundaries are edge surfaces or ends of the core. The term is meant to include single-unit structures, e.g., a single plate, slab, or disk, as well as multiunit structures, e.g., two or more plates in adjacent or offset and end-to-end position, as will be described in greater detail hereinafter.

The front to rear axis of the frame is the axis parallel to the forward-backward direction of travel of the frame. The barrier mounted on the frame is transverse" inasmuch as the top and bottom surfaces of the core are substantially normal to the frames front to rear axis, and therefore normal to the axis of a tunnel or shaft through which the apparatus travels.

The term radius and various modifications thereof as used herein to describe the variability of the dimensions of the barrier is a line on the cores top or bottom surface which begins at the latters center and extends out from the edge surface to a point where said line is intersected by a normal thereto which passes through a point, line, or surface of the sealing member farthest extended from the edge surface.

The term localized radial variability" when used herein to describe the extensibility and retractability of the deformable sealing member on the core denotes that the variability in radius length of the barrier due to extension and retraction of the sealing member is not only a general overall variability as is achieved with a radially uniform extension and retraction of the sealing member, but also localized" in the sense that the extension and retraction can be radially nonuniform so that the lengths of radii emanating from the above-described center can be changed to different degrees. Stated differently, each of a number of local areas or sections of the sealing member can be extended or retracted to a degree which can differ from that to which other areas or sections are extended or retracted. This gives the barrier a variable edge contour,

which can be adjusted as required to conform substantially to different contours of surrounding surfaces, e.g., different sections of the internal surface of a tunnel or shaft, so that a seal can be effected between the barrier and such surfaces. The edge contour" is the contour of the surface portion of the sealing member which contacts the surrounding surface e.g., walls of a tunnel. The adjustable edge contour of the barrier as well as the conveyability of the shielding apparatus make the apparatus particularly useful as a passageway-sealing blast shield in underground drill-and-blast excavation operations, in which the apparatus is required to be moved ahead as a face or heading is advanced and intermittently to effect a seal with surface sections, each time at a new location at which the surface contour is apt to vary more or less considerably from the surface contour at previous locations. An effective seal is important to provide adequate sound attenuation so that personnel can be located on or near machinery remaining in the vicinity of the face during blasting.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, which illustrate specific embodiments of this invention:

FIG. 1 is a side elevational view of a shielding apparatus of this invention shown in position in an opening such as a tunnel;

FIG. 2 is a plan view of the shielding apparatus illustrated in FIG. 1;

FIG. 3 is a front view of the shielding apparatus illustrated in FIG. I; and

FIG. 4 is a detailed view of component 13 of the apparatus illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the shielding apparatus is illustrated in FIGS. 1, 2, and 3. The apparatus, which is shown in position in a substantially horizontal opening such as a tunnel, has a carriage 1 comprising a substantially horizontal frame 2 mounted on motion-transmitting means 3, in this case a pair of spaced crawlers. The horseshoe-shaped opening has a ceiling 36, floor 37, and

walls

38a and 38b which are somewhat irregular in contour. Mounted on frame 2 at the forward end thereof is a transverse barrier 4 comprised of a segmented rigid core 5 having a continuous deformable sealing member 6 secured thereto. Rigid core 5 consists of a lower segment 5b, e.g., a plate, which is fixedly mounted to frame 2 in a substantially vertical attitude, e.g., by means of bolts 7; and an upper segment 50, e.g., a plate, which is pivotally secured to lower segment 512 at hinge joints 8 in a manner such that the bevelled lower edge of upper segment 5a is adjacent to the upper edge of lower segment 5b, upper segment 50 thereby being enabled to pivot about a horizontal axis. The top and bottom surfaces, 50 and 5d, respectively, of core 5 are the two surfaces formed from the two pairs of coplanar surfaces of

segments

5a and 5b when segment 5a is in the vertical position, the top surface, 50, being forward of the bottom surface 5d, with respect to the forward direction of travel of carriage 1.

Surfaces

5c and 5d thus are substantially normal to the front to rear axis of horizontal frame 2. Tilting and lifting of upper segment 5a is achieved by the action of cylinders 9 and 10, the piston rods of which are pivotally connected to the upper segment portion of bottom surface 5d and the cylinder ends to a generally A- shaped anchoring member 11. Cylinders 9 and 10, acting in conjunction with anchoring member 11, also constitute bracing means for core 5. Pivoting of upper segment 5a effects a change in the overall vertical dimension of core 5, permitting the apparatus to be moved in a constricted area without hindrance and to be used in openings of various sizes by selecting a suitable respective positioning of

segments

5a and 5b.

Sealing member 6 is shown as, and preferably is, a two-ply layer of extensible and retractable sectional components, each comprised of a deformable tab or flap usually rectangular. In each ply, the sectional components are positioned in side-byside adjacent relationship, the adjacent surfaces of the components, 12a, in one ply being staggered with respect to the adjacent surfaces of the components, 12b, in the other ply so that the components of one ply and those of the other mutually overlap at the adjacent surfaces. Components 12b are longer than components 12a and extend farther out from the edge surfaces of core 5 than do components 120.

Sectional components

12a and 12b are made of a tough but somewhat flexible material, such as a fiberor metal-reinforced elastomer, e.g., rubber. Sealing member 6 completely surrounds the periphery of core 5 in the vicinity of the cores outer edge surfaces.

The sealing member adjustment means 13 for extending and retracting

sectional components

12a and 12b, shown in greater detail in FIG. 4, are pivotable rigid metal hinge plates 14, each plate having secured thereto one sectional component' 12b of one ply and one pair of adjacent sectional components 12a of the other ply. The

flaps comprising components

12a and 12b are secured to the front surface 5c of core 5 near the latters edge surfaces in the manner shown in FIG. 4, e.g., by bolts 15, components 12a being sandwiched between components 12b and surface 50. A rectangular hinge plate 14, in the vicinity of one of its short ends, is secured to components and 12b, e.g., by bolts 16, in the manner shown in FIGS. 2 and 4, each pair of components 12a being sandwiched between a hinge plate 14 and a component 12b. Each hinge plate 14 in the vicinity of its short end opposite that to which

components

12a and 12b are secured, is pivotally connected to the piston rod ofa separate cylinder 17, the cylinder end of which is pivotally connected to back surface 5d of core 5. Hinge plates 14 also are pivotally connected to core 5 near the latters edge surfaces at hinge joints 18. Actuation of cylinders 17 pivots hinge plates 14, causing deflection of

components

12a and 12b.

Optionally, a second transverse barrier 19, substantially the same as barrier 4, can be fixedly mounted on carriage frame 2 behind anchoring member 11 in substantially the same manner as barrier 4.

Elements

20, 20a, 20b, 20c, 20d, 21, 22, 23, 24, 25, 26a, 26b, 27, and 28 on barrier 19 are counterparts to

elements

5, 5a, 5b, 5c, 5d, 6, 7, 8, 9, 10, 12a, 12b, 14, and 13 on barrier 4, respectively. The second barrier provides additional capability in pressure and noise level reduction. The portions of sealing members 6 and 21 adapted to seal against wall 38a are omitted in FIG. 1 for purposes of clarity.

The apparatus is adapted to be held intermittently to a structure surrounding the edge surfaces of

shields

5 and 20, e.g., to ceiling 36 and

walls

38a and 38b, by operation of anchoring means mounted on frame 2 between the barriers. Anchoring member 11 has a substantially horizontal platelike upper portion atop two pairs of legs fixedly mounted on opposite sides of frame 2 as in an A-shaped configuration. A side-clamping device is mounted on each leg of anchoring member 11, clamping

devices

29 and 30 on a pair of legs on one side of the apparatus, and clamping

devices

31 and 32 on a pair of legs on the other side of the apparatus. Each clamping device is comprised of a cylinder mounted on anchoring member 11 with its cylindrical axis substantially parallel to, and substantially normal to the front to rear axis of, frame 2; and having its piston rod pivotally connected to a pad having a serrated outer surface. Two top clamping devices, 33 and 34, are mounted on frame 2, each being comprised of a cylinder vertically mounted on frame 2, passing through the horizontal upper portion of member 11, and having its piston rod pivotally connected to a pad having a serrated outer surface. Actuation of the cylinders in clamping

devices

29, 30, 31, 32, 33, and 34 allows the serrated surfaces to be pushed against, and released from, the

walls

38a and 38b and ceiling 36 of a tunnel thereby holding the apparatus in position in use and freeing it as required.

The cylinders" mentioned above are actuated by fluid power and can be hydraulic or pneumatic, hydraulic being preferred on the basis of smaller power package requirements and ease of control.

Since

transverse barriers

4 and 19 are adapted to engage surrounding surfaces, cores 5 and can have openings therein when necessary to permit passage of equipment and/or personnel. All such openings which permit communication between the external environments ahead of and behind the barrier are adapted to be closed ofl intermittently. For example, cylinder-operated closure member 35 in segment 5b, seen in the view shown in FIG. 3, is adapted to open and close an access opening in segment 5b.

A typical operation of the shielding apparatus shown in the drawings to attenuate pressure and sound resulting from blasting in a drlll-and-blast excavation process for advancing a geological face in a tunnel will now be described. With the

sectional components

12a, 12b, 26a, and 26b in an attitude such that they are disengaged from the

walls

38a and 38b, ceiling 36, and floor 37 of the tunnel, upper segments 50: and 20a in forwardly tilted positions, and the serrated surfaces on the pads connected to the cylinders of clamping

devices

29, 30, 31, 32, 33, and 34 disengaged from the

sidewalls

38a and 38b and ceiling 36 of the tunnel, the apparatus is moved to a location before a 60 sq. ft. face such that transverse barrier 4 is about feet from the face. The apparatus is anchored in place by actuation of the cylinders in clamping

devices

29, 30, 31, 32, 33, and 34, whereby the serrated surfaces are extended against the ceiling 36' and

sidewalls

38a and 38b of the tunnel. By actuation of

cylinders

9, 10, 24, and 25,

upper segments

5a and 20a are lifted until they are substantially vertical or stopped before reaching the vertical position by the surrounding geological structure. Cylinders 17 attached to hinge plates 14 on core 5, and their counterpart cylinders attached to hinge plates 27 on core 20, are actuated so as to pivot

hinge plates

14 and 20 and thereby deflect the

flaps comprising components

12a, 12b, 26a, and 26b backward until they firmly engage the

walls

38a and 38b, ceiling 36, and floor 37 of the tunnel, effecting a seal therewith. The degree to which the flaps have been deflected varies from one flap to another because of irregularities in the contour of the walls, ceiling, and floor surfaces, i.e., there is localized radial variability in the degree of extension of sealing members 6 and 21. Closure member is in the closed position. The tunnel cross section at the location of

barriers

4 and 19 is 98.5 percent closed. When an explosive charge weighing about 3 pounds is placed in a borehole in the face and detonated therein, the air blast pressures ahead of and behind transverse barrier 4, as measured by side-on pressure gages are 4.58 p.s.i. and 0.598 p.s.i., respectively, equivalent to sound levels of l84.3 decibels and 166.5 decibels, respectively. Additional attenuation is achieved when optional barrier 19 is employed.

After blasting, the

flaps comprising components

12a, 12b, 26a, and 26b are deflected forward by actuation of the cylinders 17 attached to hinge plates 14 and the cylinders attached to hinge plates 27; the serrated surfaces of clamping

devices

29, 30, 31, 32, 33, and 34 are disengaged from the ceiling 36 and

sidewalls

38a and 38b of the tunnel by actuation of the cylinders in these devices;

upper segments

5a and 20a are tilted forward by actuation of

cylinders

9, 10, 24, and 25; and, after removal of rock fragments from the path of the shielding apparatus, carriage l is moved ahead to a new position.

When in use, the shielding apparatus of the present invention is positioned in an opening or passageway with the top and bottom surfaces of the core substantially normal to the direction in which a pressure wave is expected to travel, e.g., normal to the axis of a tunnel or shaft, or parallel to a face to be blasted. in order for the apparatus to provide the required pressure and sound attenuation, it must itself be resistant to the pressure exerted on it as well as to missile impact if the apparatus is positioned within range of missile throw in a blasting operation. For this reason, the core is rigid in construction and made of one or more high-strength materials, preferably comprising a metal, metal-reinforced, or wooden plate or slab (single unit or end-to-end multiunit construction). The core also can have a laminar structure of side-by-side adjacent layers in planes normal to the thickness dimension, e.g., layers of different materials such as a layer of granular material or corrugated metal between two metal plates. With metal cores the use of a more sound-absorbent material such as wood or an elastomer as a covering on the surface confronting the pressure wave may be desirable to reduce a gong" tendency.

As stated above, the core can have a single'unit structure, i.e., that of a single plate, slab, or disk, or can be comprised of two or more segments, fixed or mutually movable. A preferred multiunit structure is one in which two or more segments of the core are arranged in adjacent end-to-end position (i.e., with corresponding top surfaces and bottom surfaces of the segments adapted to be substantially coplanar) (FIG. 1), or ofiset end-to-end position (i.e., with the segments adapted to be in substantially parallel, noncoincident planes). With such a structure, the topmost segment of the core can be pivotable about a horizontal axis parallel to the long dimension of the end surface which is in end-to-end position with the next segment, allowing easier adjustment of the overall height of the transverse barrier to permit movement of the apparatus through the opening and adaptation to openings of various heights. Pivoting of core segments about a vertical axis can be provided to adjust the overall width of the barrier, if required. Mutually sliding segments also can be employed. In most cases, it will be simpler to have an adjacent end-to-end (substantially coplanar) multiunit structure, and this is preferred. With multiunit structures, there should be substantially no free space between the two adjacent or nearest end surfaces of each pair of segments in the structure, and therefore there is an intervening rigid member such as a plate or slab joining the two nearest end surfaces of spaced-apart offset pairs of plates, producing a stepped design. Also, in multiunit structures, although the segments of the core are adapted to be in substantially parallel planes, one or more segments can be adapted to move so that an angle can be present between a pair of segments.

The configuration of the core as well as any segments present therein can vary as desired. Any convenient design suitable for use in the passageway in question can be used. Top and bottom surfaces which are rectangular, square, oval, round, horseshoe-shaped, etc., can be used. The thickness of the core, and the segments thereof, can be substantially uniform, or it may vary to provide a desired effect.

The deformable sealing member secured to the rigid core in the vicinity of the latters edge surfaces is extensible and retractable with localized radial variability, i.e., each of a number of local areas or sections of the layer can be extended or retracted to a degree which can differ from that to which other sections are extended or retracted. Localized radial variability is achieved more easily with a layer of individually extensible and retractable sectional components, and a sectionalized sealing member therefore is preferred. To assure effective sealing, the adjacent sides of sectional components overlap, e.g., as in an echelon arrangement of components or in a multi-ply layer wherein the sectional components of one ply overlap the sectional components of an adjacent ply. The layer of sectional components can consist of elastomeric inflatable and deflatable bladderlike members secured to the edge surface(s) of the core in the nature of a sectionalized collar. The collar sections extend to the surrounding surfaces as a result of expansion when inflated, and retract from these surfaces as a result of contraction when deflated. Another inflatable-deflatable type of sealing member consists of flexible hoses attached edgewise to the core at or near the edges thereof, the hoses hanging limp and therefore disengaged from the surrounding surfaces when unpressurized, and rigid and erect and in engagement with the surrounding surfaces when pressurized with fluid. Alternatively, the sealing layer can be a mechanically deflectable or slidable flap or wedge, preferably sectionalized, of a heavy elastomeric material, mounted near the edge surface(s) of the core, the flap(s) or wedge(s) being extended to, and pressed against, the surrounding surface and retracted therefrom, for example, by the actuation of cylinders connected to metal hinge plates fastened to the flap(s) or wedge(s). When a single flap or wedge is employed along an entire surface of the core, localized sectional extensibility and retractability can be achieved by employing a number of separate hinge plates to move sections of the flap as required to seal the opening. Optimum scaling is achieved with flap or wedge sections, however, and therefore it is preferred to have a single-ply or multi-ply layer of adjacent flaps or wedges, each flap or wedge, or pair of adjacent flaps or wedges, in a given ply preferably being movable via a separate device, e. g., a metal hinge plate, as is illustrated in FIGS. 1, 2, 3, and 4. The flap or wedge type of sealing layer is preferred since it is more rugged than inflatable layers, being less prone to failure as a result of accidental cutting, e.g., on rock.

The core of the apparatus of the present invention is mounted on a rigid supporting frame of a carriage on which it is conveyed through an opening or passageway for use at different locations therein. The nature of the carriage depends on the type of opening in which the apparatus is to be used, e.g., a substantially horizontal tunnel or a vertical shaft, additional components to be mounted on the frame, etc. In most instances, in the interest of efficiency, the motion-transmitting means of the carriage will be power-driven, e.g., wheels or crawlers. Since the shielding apparatus is used to great advantage in conjunction with drilland-blast excavation machines which remain stationed at a face during blast, the carriage of the shielding apparatus can be the carriage of an excavating machine, e.g., the machine described in the previously mentioned application, Ser. No. 49,662, filed June 25, 1970. One or more transverse barriers are mounted on the frame, more barriers giving a greater degree of pressure and sound attenuation.

Inasmuch as the core is mounted with its top and bottom surfaces normal to the frame's front to rear axis, and therefore normal to the axis of a tunnel or shaft and in the travel path of a pressure wave, the barrier mounting must be strong. This means that the core should be secured to the carriage frame at a number of balanced points on the back surface of the core e.g., across both segments a and 5b in the core shown in H0.

in order that the shielding apparatus be able to withstand the force of the pressure wave to which it is to be repeatedly subjected, the apparatus is adapted to be anchored intermittently to the massive structure surrounding the edge surface(s) of the core, i.e., to be anchored temporarily, released, reanchored, etc., to the surfaces of an underground opening. This can be accomplished by clamping devices of various kinds, e.g., metal anchor rods or pads connected to fluidpower-actuated cylinders mounted on the carriage frame, e.g., on the frame per se or on a structural member mounted on the frame. The outer surfaces of the rods or pads which engage the surrounding surfaces can be serrated if desired. Actuation of the cylinders in the clamping devices allows the rods or pads to be pushed against the surrounding formation, thereby clamping the apparatus in position. The anchoring means exert pressure in two opposite directions, and preferably also in a third direction normal to the two opposite directions. When the shielding apparatus is used in a drill-and-blast excavation machine, such as that described in application, Ser. No. 49,662 filed June 25, 1970, the anchoring means, as well as the carriage, of the excavating machine may be common components for the excavating machine and shielding apparatus.

The utility of the present shielding apparatus has been described in greatest detail with respect to the sealing off of tunnels and shafts during blasting operations, for it is in this area that the apparatus affords special advantages, allowing drill-and-blast operations to be performed safely with machinery which remains stationed at the face during blast and with personnel on or near the machinery. However, the apparatus can be employed for various other purposes, for example to seal off such passageways as worked out sections (entries or breakthroughs) in active or inactive mine workings, in particular in coal mines, so as to provide an exlplosionproof bulkhead. The shielding apparatus can be use of course, wherever sealing of an irregular opening having no closure means of its own is required for sound and/or pressure attenuation, e.g., a tunnel or shaft seal to attenuate noise produced by drilling equipment or other machinery.

We claim:

1. An apparatus for attenuating pressure and sound which comprises a frame mounted on motion-transmitting means, means for holding the apparatus in place when in use, and a transverse barrier mounted on said frame, said barrier comprising a. a rigid core having opposing top and bottom surfaces and an edge surface adjacent thereto, said core being mounted on said frame in a manner such that the top and bottom surfaces are substantially normal to the front to rear axis of the frame, and

b. a deformable sealing member completely surrounding the periphery ofsaid core, said sealing member being extensible and retractable with localized radial variability in a manner such that radial dimensions of said barrier are adapted to change and to differ from one another.

2. An apparatus of claim 1 wherein said core is segmented, at least one segment being adapted to move in a manner such that an overall dimension of said core can be varied.

3. An apparatus of claim 2 wherein a segment of the core pivots about a horizontal axis to change the vertical dimension of said core.

4. An apparatus of claim 3 wherein the core has two segments.

5. An apparatus of claim 1 wherein said deformable sealing member comprises a plurality of overlapping, extensible and retractable sectional components.

6. An apparatus of claim 5 wherein the sectional components are flaps.

7. An apparatus of claim 6 wherein the flaps are secured to pivotable hinge plates for extension and retraction.

8. An apparatus ofclaim 7 wherein the flaps form a continuous multi-ply layer.

9. An apparatus of claim 7 wherein the means for holding the apparatus in place when in use is a plurality of friction-engaging clamping devices mounted on the frame.

10. An apparatus ofclaim 7 wherein the core comprises two segments in adjacent end-to-end position wherein one seg ment is above the other, the lower segment being fixedly mounted on said frame and the upper segment being pivotable with respect to the lower segment.

11. An apparatus of claim 10 wherein the deformable sealing member is fabricated of elastomeric material.

Claims

1. An apparatus for attenuating pressure and sound which comprises a frame mounted on motion-transmitting means, means for holding the apparatus in place when in use, and a transverse barrier mounted on said frame, said barrier comprising a. a rigid core having opposing top and bottom surfaces and an edge surface adjacent thereto, said core being mounted on said frame in a manner such that the top and bottom surfaces are substantially normal to the front to rear axis of the frame, and b. a deformable sealing member completely surrounding the periphery of said core, said sealing member being extensible and retractable with localized radial variability in a manner such that radial dimensions of said barrier are adapted to change and to differ from one another.

4. An apparatus of claim 3 wherein the core has two segments.

6. An apparatus of claim 5 wherein the sectional components are flaps.

8. An apparatus of claim 7 wherein the flaps form a continuous multi-ply layer.

10. An apparatus of claim 7 wherein the core comprises two segments in adjacent end-to-end position wherein one segment is above the other, the lower segment being fixedly mounted on said frame and the upper segment being pivotable with respect to the lower segment.