Abstract: In a longwall mining operation, a panel to be extracted is formed in a seam of mine material by longitudinally extending headgate and tailgate entries with the panel beginning in a set-up room and ending at a termination line in a recovery room. The recovery room is developed in two stages and is supported by primary and secondary roof support systems that include mechanical roof bolt assemblies, roof trusses, and channel members. The effectiveness of the roof support systems to support the overlying rock strata and withstand the abutment pressure exerted on the strata by the advancing longwall face as it approaches the recovery room is monitored by an instrumentation plan. Data gathered from the instruments is continually monitored as the longwall panel recovery operation progresses.

Abstract: A primary mining post, prop, or support that is yieldable to the settling forces of a mine shaft and has a double ball and socket configuration to respond to the shifting that occurs with roof settling in mine shafts. The post has a ball on each end of the main support body and corresponding sockets in each of the respective top and bottom bases. The main body has means for yielding to the heavy weights put thereon.The double ball and socket configuration allows the heavy weights of a settling subterranean roof to be fully transmitted axially along the length of the main body of the post during off vertical loading without undue buckling and failure. The loading characteristics remain virtually identical with straight vertical and off vertical loading. Traditional supports will buckle and fail under a shifting load since the load forces are distributed differently under a non vertical load.

Abstract: A process for forming agglomerates of metallurgical dust containing metal sulphates for recycling to extractive processes includes adding lime particles and a small amount of water, forming a mixture and extruding the damp mixture and allowing the extruded agglomerates to become hard and shape retentive. The material agglomerated may be water soluble metal sulphate containing particles or mixtures of such particles with other value metal bearing waste or by-products of metallurgical processes. Optionally additional binding agents comprising cement and hydrocarbonaceous substances such as wax may be added to the mixture.

Abstract: An adjustable column for use between ceiling and floor surfaces of a mine has an outer tube having an outer end and an inner end and an inner tube having an inner end in the outer tube at the inner end thereof and an outer end. The tubes are coaxial to an upright axis and an external screwthread on the outer-tube inner end fits with an inner screwthread on the inner-tube inner end so that the tubes can be screwed relative to each other to change the axial length of the column. One of the outer ends is operatively braced against one of the surfaces and the other outer end is spaced from the other of the surfaces. A resiliently compressible support element is braced axially between the other outer end and the other surface.

Abstract: A cable truss system for providing support for underground drifts in geologic structure in a first stage from anchor members secured in the geologic structure for leaving end portions in the drift to which a first system of supports are secured to engage on the geologic structure disturbed by the drift formation, and cable truss members connected to the first system of supports for establishing a second stage of support for the geologic structure disturbed by the drift formation.

Abstract: A cable bolt mine roof crib for support and stabilization of roof rocks employing a series of cable bolts and/or cable members through a cribbing frame for actively supporting the roof and area surrounding an underground opening. The support imposes a restraint on geologic movement of the roof by the placement of rock anchors on the ends of cables at depth through the rock mass. The anchor portions of the cable bolts are placed beyond the zone of failure that would normally take place around an underground opening. The roof crib provides a bearing area for the roof rock which limits deformation and offers support by suspension to maintain interlock of rock fragments of the roof of the underground opening. The strength and length of cable bolts can be adjusted to fit initial tectonic load conditions and subsequent loads placed upon the opening by adjacent mining.

Abstract: This invention relates to a grout composition comprising a Portland cement, a high alumina cement, anhydrous calcium sulphate, an effective amount of a lithium salt and an effective amount of a strong base. According to another aspect of the invention, instead of using a strong base directly in the grout composition, a first compound and a second compound is added to the grout composition which in use react to form an effective amount of a strong base when the grout composition is mixed with water.

Abstract: A roof support column used as a support between the roof and floor of a mine comprises a stacked series of hollow roof support cribs containing a mixture of light-weight aggregate such as volcanic lava, tuft or pumice, and a chemical foam contained in one chamber of a triple-walled high density paper tubing. The other chamber has honeycomb material therein. The combination of these materials results in a roof support crib which has the yielding characteristics of wood. Such cribs called variable yielding cribs are stacked and locked on top of one another to form a vertical cylindrical cribbing support column.

Abstract: The invention concerns a method and apparatus for providing yielding support for a hanging wall above a footwall in a mine working. A support assembly is installed between the hanging wall and the footwall, the assembly including a spacer (10), a pack (30) and a grout-inflatable bag (32). Grout is pumped into the bag (32) and is allowed to set to apply a vertical prestess force to the support assembly. The spacer (10) is substantially stiffer in compression than the pack (30), which is designed to yield under the compressive loading applied by the hanging wall. The use of a stiff spacer (10) serves to elevate the yielding pack to a suitble operative height without the allowable slenderness ratio for the pack to be exceeded.

Abstract: The mine prop headboard (10) is used to support an inflatable grout bag (44) and is located transversely on an end of an elongate mine prop (12) which is in use installed upright between a hanging wall and a footwall in a mine working. The headboard includes a chock assembly which is composed of parallel, elongate timber chocks (14). A steel reinforcement sheet is secured to and extends over the support surface of the chock assembly to provide tensile reinforcement a grout bag is placed on the headboard and is inflated with grout under pressure sufficient to apply a compressive axial force to the prop between the hanging wall and the footwall.

Abstract: In a longwall mining operation, a panel to be extracted is formed in a seam of mine material by longitudinally extending headgate and tailgate entries with the panel beginning in a set up room and ending at a termination line in a recovery room. The recovery room is developed in two stages. In the first stage, the recovery room extends the transverse width of the panel and extends from the termination line a preselected distance to a first sidewall. A roof control system is installed to support the rock strata over the initial width of the recovery room. A primary support system includes mechanical roof bolt assemblies installed in accordance with a preselected bolt pattern. The roof bolt assemblies are supplemented by trusses extending in spaced parallel relation a preselected distance apart from the termination line to the first sidewall. Channel members are secured in end to end relation to the roof closely adjacent to and parallel to the first sidewall.

Abstract: A support sling, useful in the mining industry, for example, for supporting overhead loads such as mine roofs; the sling includes a pair of generally coplanar anchor lengths, sometimes called anchor bolts, having inwardly directed ends mutually facing each other and which, thus, are essentially coaxial; a similarly coaxial take-up coupling structure secures the ends and is constructed, either in active or passive mode, to restrain loads, acting under the force of gravity, from dilating downwardly to extreme conditions, and this in a manner as not to allow for the generation of serious force couples in the sling.

Abstract: Mine roof support systems, components and method, for supporting, whether in active or passive mode, mine roof strata; first and second, mutually spaced series of brackets are supplied for mounting to opposite sides of a mine roof span, and one or more cable assemblies are looped about such brackets and secured to the mine roof strata, such cable assemblies also being provided with take-up means: the invention is suitable and effective for supporting mine roof strata at various, desire mine locations.

Abstract: A method is described for protecting piston cylinder devices against corrosion by a pressure resistant thermoset or cured material coating. At least the outer and inner cylindrical surfaces, for example, of a mine prop, that cooperate with a sealing device, are coated with a three-dimensionally cross-linked, cured or thermoset material having a sufficient thickness on the one hand for providing the intended protection against corrosion and on the other hand to avoid excessive radially directed elastic deformations of the coating. An additive is included in the coating to improve the dry lubricating characteristics, and thus the cooperation between the coating and the sealing devices. The three-dimensionally interlinked thermoset material fills all surface irregularities so that gas and water pockets, for example, in a mine prop, are avoided.

Abstract: A roof support column used as a support between the roof and floor of a mine comprises a stacked series of hollow roof support cribs containing a mixture of light-weight aggregate such as volcanic lava, tuft, or pumice, and a chemical foam contained in a double-walled high density paper tubing. The combination of these materials results in a roof support crib which has the yielding characteristics of wood. Such cribs called variable yielding cribs are stacked and locked on top of one another to form a vertical cylindrical cribbing support column.

Abstract: The yieldable load support comprises a compressible support member in the form of an elongate timber pole. The load support or pole is asymmetrically modified at or near one end thereof in a manner to positively induce sideways brushing of the pole at the modified end, in a preferential direction transverse to the length of the pole, when the support member is placed under longitudinal compressive load of sufficient magnitude.

Abstract: A shoring leg provided with a latch for use in maintaining an end plate on the shoring leg and a jack collar in a predetermined position relative to each other, the latch comprising a latch member mounted on the leg to execute a movement from a latching position to a release position, the latch member defining a recess jaw adapted, when in the latching position, to receive part of the leg end plate and to receive a corresponding part of an adjacent collar of a jack to retain the end plate and the collar in said predetermined position, there being means to retain the latch member in the latching position.

Abstract: A yieldable confined core mine roof support including a container and a filler placed within the container. The container is yieldable and the filler is compressible. The combination of a filler within a container produces a mine roof support which is yieldable under a substantially axial load and which increases in load carrying ability as it yields, impeding any decrease in the distance between a mine roof and a mine floor, minimizing or preventing mine roof collapse and mine floor heave, buckling or punching.

Abstract: A pair of truss brackets are secured to the roof of an underground passage adjacent to opposing ribs of the passage. The truss brackets each include a roof engaging surface and a truss supporting arm member extending from the roof engaging surface. A pair of U-bolts are supported by the arm members of the truss brackets. Each arm member extends horizontally from the truss bracket to an enlarged end portion of the arm member. The U-bolt is horizontally movable in a vertically hanging position on the arm member and is restrained by the enlarged end portion from disengagement from the arm member. The U-bolts are pivoted on the truss brackets to a horizontal position for connection to truss members which are connected to each other and tensioned to apply an uplifting force to the roof. As the truss members are connected and tensioned, the U-bolts are retained for a range of horizontal movement on the arm members to facilitate adjustments in the position of the U-bolts on the truss brackets.

Abstract: For use in underground individual prop support, an individual prop valve is provided whose case integrates a return valve for setting, a non-return valve for drawing, and a pressure-limiting valve for securing the prop against overload. The valve case of the pressure-limiting valve is moved hydraulically if the case is also equipped on the drawing side with a coupling piece which has a gripping groove and locking shoulder. A push bolt which is loaded correspondingly by the pressure fluid acts on the valve case and moves it by a predefined length, so that the non-return valve is hereby opened and the pressure fluid is able to flow from the prop interior through the suction pump connection located on the setting side. Here the channels or spaces are proportioned in such a way that an increased amount of pressure fluid may be discharged, whereby this process is supported by a pump connected to the suction pump connection.

Abstract: An elongated channel member for supporting the surface of an underground rock formation includes a base portion with a bearing surface for contacting the rock strata and an opposite surface having a longitudinally extending central rib and flanged edges for resisting deflection and bending of the channel member under the load of the rock strata. A plurality of openings spaced a preselected distance apart extend through the central rib. A bearing plate is positioned in overlying abutting relation with each opening in the channel member. The bearing plate includes embossed areas and longitudinally flanged edges that are complementary in shape with the central rib and flanges on the channel to securely engage the bearing plate on the channel member. Thus, the bearing plate engages the channel member to restrain longitudinal and lateral movement of the bearing plate on the channel member and stiffen the channel member to resist bending.

Abstract: The invention concerns a prop headboard (10) which is used in conjunction with an elongate mine prop. The headboard supports a preload bag (50) inflatable with a settable grout. The headboard is composed of a headboard member (12) and a pot (34). The headboard member includes a pressed steel sheet (14) having relatively higher end regions (16) and a relatively lower central region (22). The central region is formed with an opening (24). The headboard member also has bag retaining formations (30) which receive opposite ends of a preload bag located on the headboard member. The pot is engaged in the opening in the central region and receives the upper end of an elongate prop, thus supporting the headboard member on the prop with the headboard member extending transversely to the prop.

Abstract: A travelling steel form system includes a three-dimentional framework mechanism with multiple faces crossing and coupling with one another. A set of form panels are fixed to the outer side of the framework mechanism on more than two faces thereof, and are capable of connecting to one another to form a predetermined shape and disconnect from one another to change the shape following expanding and retracting movement of the framework mechanism. A driving device is vertically or horizontally retractably mounted on the front end and or rear end of the framework mechanism for driving the latter to perform movements of expanding the outer diameter or reducing the outer diameter. The system is particularly suited for use in concrete placing work in civil engineering constructions.

Abstract: A grid composite for protecting men and longwall mining equipment during longwall shield recovery includes a regular polymer geogrid structure formed by biaxially drawing a continuous sheet of select polypropylene material which is heat bonded to a polyester fabric. The grid composite is secured over caving shields of longwall mining equipment during a longwall mining operation. The polymer grid composite is ideal for waste containment structures, backfill barriers, and silt barriers in construction and mining applications. In waste containment and backfill barriers, the grid composite is used to form a containment structure. It principle function is to contain waste material usually consisting of a liquid with some percentage of solids.

Abstract: Support column for underground mining and tunnel construction, composed of a load-bearing outer shell and a core of a substance which is to be introduced in the flowable state and is capable of hardening. The upper column component can be slid out of the lower column component and is secured against being slid into the lower column component by a ring-shaped spring element. Active clamping forces can be introduced by means of clamping devices which can be mounted on the outside.

Abstract: The invention relates to a tunnel shuttering, divided into two sections according to a dividing line lying in the plane of the horizontal panel of the shuttering and extending in the longitudinal direction of the tunnel. The tunnelsections may be coupled with one another by a number of connecting links, each of which having one end pivotally connected to one tunnel section about an axis standing in the longitudinal direction of the tunnel and adapted to have the other end removably "hooked" about a projection on the other tunnel section. Furthermore an auxiliary connecting link of a shorter length is provided, the ends of which are pivotally connectable to said other tunnel section and to an intermediate point of the connecting link respectively. Due to this the tunnel shuttering may be selectively used according to the half-tunnel-mode or according to the full-tunnel-mode.

Abstract: A cable attachment assembly having an anchor mechanism for gripping a tension member anchored in a bore hole in a mine roof, and a roof plate mounted on the anchor mechanism in positions for observing the support being offered to the mine roof, or the yielding response of the roof plate on the anchor mechanism, or for monitoring the load-yield relationship of the anchor mechanism relative to the tension member.

Abstract: The present invention relates to an adjustable support element for use in underground mining or tunnel construction, particularly for securing mining cavities at the longwall face and headway. The invention is a single use prop made of inner and outer telescopable tubes which can be filled with a hardenable building material core. The tubes have drainage boreholes for draining excess water from a liquid filling material pumped within the tubes after the prop has been braced between the roof and floor of the mines. Plural bands connected between the outer and inner tubes enable the telescopic movement of the tubes.

Abstract: A mine roof support system is disclosed having a connector. The connector has a first hole through which one end of a first roof supporting rod is inserted and a second hole through which one end of a second roof supporting rod is inserted. The first and second roof supporting rods are fastened to the connector so as to support the roof of the mine. In order to increase the bending arcs of the connector along which the first and second roof supporting rods bend without increasing the weight of the connector, the holes of the connector may be bevelled to form elliptical openings in the connector and the connector may be canted.

Abstract: A backbone-type framework for tents or houses, comprising a rope, a plurality of backbone links connected in series by said rope; a hand winch located at one end of said framework to tension or release the rope; a rope-reverser located at the other end of said framework; each of the backbone links comprises a tube link and two end caps, said end cap has tube portion and an end plate, said tube portion can be inserted into said tube link, said end plate has two holes, the outer end surface of said end plate is oblique.

Abstract: A mine support post having a yieldable mine post construction, made of metal and in telescoping form. The post of the invention comprises a pair of mutually telescoping metal post lengths. The innermost tubular post length has a medial bubble portion of enlarged girth which is oversize relative to the nominal inside diameter of the outermost tubular post length. The result, consequently, is not only to increase the frictional resistance between the post lengths but also to create a bubble zone characterized by elastic/plastic mutually inter-cooperating radial deformation and elastic stress-loading of the telescoping post construction, for further progressively increasing resistance of the composite post structure to compression end loading of such post. The yieldable mine post construction can be made adjustable and also radially preloaded and preset for immediate, desired load resistance.

Abstract: A clamp for clamping attachment to a mine roof channel, which clamp has a pair of top portions and a pair of bottom portions for engaging the top and bottom, respectively, of the mine roof channel. A bolt, such as an eye-bolt, has a threaded portion extending between the top and bottom portions of the clamp forming a component part of the clamp. Such threaded portion, in one modification of the clamp, engages the bottom central portion of the mine roof channel. Loads such as wires, hoses etc. may be supported by the eye of eye-bolt so as to be adjustably positioned close to the sidewalls of the mine.

Abstract: A yieldable mine post system having a yieldable mine post construction, made of metal and in telescoping form. The post of the invention comprises a pair of mutually telescoping metal post lengths. The innermost tubular post length has a medial bubble portion of enlarged girth which is oversize relative to the nominal inside diameter of the outermost tubular post length. The result, consequently, is not only to increase the frictional resistance between the post lengths but also to create a bubble zone characterized by elastic/plastic mutually inter-cooperating radial deformation and elastic stress-loading of the telescoping post construction, for further progressively increasing resistance of the composite post structure to compression end loading of such post. The yieldable mine post construction can be made adjustable and also radially preloaded and preset for immediate, desired load resistance.

Abstract: A push-on gripper plate for use in securement of a mesh screening means on the protruding, threaded, end portion of a rock bolt inserted into a rock face is disclosed. The gripper plate has a generally planar base portion adapted to overlie the mesh screening means and a central opening in the base portion having two or more leg portions positioned on the perimeter of the opening and inclined upwardly, inwardly toward the center of said opening above the plane of the base portion. A plurality of tab portions are positioned on the perimeter of said opening in alternating arrangement with said leg portions, the tab portions being inclined upwardly, inwardly toward the center of the central opening above the plane defined by the base portion.

Abstract: A hydraulic steel mine prop having a bottom ram including an outer cylindrical tube with a cylinder foot at one end and a collar ring at the other end, and with a top ram coaxially guided in the bottom ram. The top ram is substantially a cylindrical tube with a piston at its one end, whereby the piston is guided in and sealed relative to the inner wall of the outer cylindrical tube, and with a prop head at its other end. The top ram includes an inner prop extension stop and a return spring formed as a screw spring which is secured with one end to the prop head and with the other end to the cylinder foot. The return spring passes through a bore in the piston, whereby a further tube which encloses the spring, is arranged coaxially between the prop head and the piston. The piston includes a safety valve which relieves the pressure from a compression chamber when the piston assumes a predetermined end position.

Abstract: The method consists of separately embodying, by means of filamentary winding, the internal wall 11 of an annular caisson on a primary mandrel 9, of securing to this wall separately prefabricated stiffening elements 3, of juxtaposing to the primary mandrel an interpolated mandrel 17 inserted between the stiffening elements, of embodying above said interpolated mandrel the lateral walls and the external wall 12 of the caisson and of removing the single-piece assembly from the interpolated mandrel elements enclosed in the caisson.Application for the embodiment of load-bearing structures.

Abstract: A roof support system is disclosed having a first rod extending into a first bore in the roof of a mine, a second rod extending into a second bore into the roof of a mine, a connector having a first hole through which the free end of the first rod is inserted and a second hole through which the free end of the second rod is inserted such that the first rod is held in securing fashion within the connector, and a nut threadably engaged to the second rod at an end of the second rod which exits the second hole of the connector, the connector and the rods forming a roof support system.

Abstract: An adjustable load-bearing apparatus capable of being operatively disposed on the end of an elongate structural member having a substantially fixed length so as to produce a structural member having an adjustable length. The apparatus includes a saddle for receiving a load-carrying beam, at least two adjustment screw members fixedly attached to the saddle, and respective nuts which bear on a bearing surface of a cross-bar disposed on a bearing plate. A guide sleeve depending from the saddle and slidable longitudinally along a portion of the elonate structural member provides moment coupling between the saddle and the elongate structural member, without subjecting the adjusting screws or nuts to bending moments.

Abstract: A mine roof truss and components thereof, the same including end support brackets, mine roof support plates, and associated structure. The truss structure is designed for maximum strength, and its mine roof support plates are designed for improving truss integrity and also for insuring that the stirrups used suitably preserve the integrity of the truss structure as well as provide safety features for stirrups to be placed under stress when such stirrups are loose or in a hanging position. The mine roof support plates utilized include depending horn portions having respective reaction surfaces for engaging stirrups to be placed in tension, and additionally, provide J-shaped lips forming cradles for the stirrups when the latter are in a hanging or loose position. In this way, the stirrups are preserved against dislodgement and free-fall within the mine which might contribute to a dangerous condition to workmen.

Abstract: An elongate shoring device capable of supporting a high longitudinal loading with the ability to yield uniformly in a direction along the longitudinal dimension of the shoring device when the longitudinal loading on the shoring device exceeds a preset magnitude. The shoring device comprises an inner elongate tube which is received within an open end of an outer elongate tube for longitudinal, telescopic movement within the outer tube. A storage compartment having a variable volume is formed by the inner and outer tube when the inner tube is received through the open end of the outer tube, with the volume of the storage compartment decreasing as the inner tube moves in its longitudinal, telescopic movement into the outer tube. A solid, non-compressible material is contained in the storage compartment, and a relief opening is provided in communication with the storage compartment.

Abstract: A cap shoe for connecting a mine prop to a head tree or cap in the form of a U-shaped girder whose U shanks have corrugations extending the full width thereof is engageable by complementary formations on the flanges of the cap or head tree which is received in the shoe. The latter is welded to the mine prop.

Abstract: Novel crib members useful in building cribbing to support roofs in underground mines or in tunnel construction and all other underground excavations where roof and ground control is of concern. These crib members are made by filling an envelope of a reinforced elastomeric material with concrete. In a preferred form used motor vehicle tires are filled with concrete.

Abstract: A method of installing a tensioned roof bolt in a borehole of a rock formation without the aid of a mechanical anchoring device or threaded tensioning threads by applying thrust to the bolt (19) as the bonding material (7') is curing to compress the strata (3) surrounding the borehole (1), and then relieving the thrust when the bonding material (7') has cured.

Abstract: A high-strength, lightweight flame-retardant and/or self-extinguishing polymer grid is provided for supplemental support of the roof and ribs of a combustible underground opening, such as within a coal mine, to prevent roof materials from falling and/or rib materials from spalling. The preferred polymer grid structure is formed of a polypropylene compounded with flame retardant additives.

Abstract: Stiffening elements are welded between the three rods (T1, T2, T3) of three-rod girders in uderground drift construction. Such stiffening elements consist of thee triangular wire polygons (10, 20, 30) connected to form one piece. Two of the polygons meet at the top rod (T3) to form a wire pyramid. The third wire polygon (30) is perpendicular to the plane determined by the axes of the lower rods (T1, T2). Since neither this third wire polygon (30) nor the adjacent polygon (10), which is one side of the pyramid, needs a cross-strut between the lower rods (T1, T2), a significant saving in materials combined with high resistance to bending is achieved.

Abstract: Hydraulic steel mine prop having a bottom ram including an outer cylindrical tube (1) having a cylinder bottom (14) and an end collar (16), as well as a top ram guided coaxially slideably in the bottom ram by the end collar (16) and a guide ring (12). The top ram is a cylindrical tube (2) comprising a piston (9) sealed and guided relative to the inner wall of the outer cylindrical tube (1). A prop head (4), a setting and withdrawal valve (21), an inner extension stroke limiter, and a return spring (6) are also provided. Each of the outer and the inner cylindrical tubes is received at its facing ends by corresponding projections or facing end grooves of the end collar or piston at one end and at the prop head or cylinder bottom at the other end. Seals are provided at least at the piston, the prop head, and the cylinder bottom. An element is provided between the prop head and the piston for taking up tension forces between these two structural parts.

Abstract: A mine roof support truss and components thereof including support brackets and accommodating stirrups. In the truss construction, a pair of new type mine roof support brackets are utilized in combination with respective stirrups, the latter including interconnecting tie rod structure. The support brackets are unitary and preferably cast in construction, the same including the first portion having an upper bearing surface and a horn portion integral with and depending from such first portion. The horn portion is provided with a lower, upturned J-shaped lip which is useful for retaining a respective stirrup, which is designed to hang, when inactive, from the horn portion at the lip. During installation procedures, the stirrup associated with each horn portion of the respective brackets is elevated to horizontal position and the two stirrups tied together by tie rod means, with or without additional structure.

Abstract: Apparatus (1) for supporting a mine roof (R) has connected plates (7, 9) positioned against the roof at opposite sides of the mine roof. One plate (7) has an upset surface (13) contacting the roof to exert a compressive load on it. Bolts (53) anchor the plates to the roof. A tie rod (64) interconnects the plates and is adjustable to vary the compressive load, and in one embodiment a slip anchor (67) is provided at one end of the tie rod which can also be utilized to estimate the tie rod load. In another embodiment a single quick connect pin (227) is provided between connected plates (207, 209).

Abstract: A yieldable mine post, made of metal and in telescoping form. The post comprises a pair of mutually telescoping metal post lengths, one being slotted to receive selectively a chosen wedge for forced insertion within the slot to spread apart one of the post lengths, as to its diameter, whereby to increase surface friction between the post lengths and, thereby, the frictional resistance offered to progressive incremental displacements of one post length relative to the other in response to the downward movement of a mine roof supported by such post and further to cause resistance to sliding by forcing the outer post length to deform elastically outward and the inner post length to deform elastically inward, thus generating a "friction bubble" of "friction envelope" which progressively moves down the zone of pipe overlap.

Abstract: A contractible mine stopping adapted to be installed to extend as a vertical wall from the floor to the roof of a passageway in a mine, comprising a series of rows of substantially solid substantially non-compressible blocks of substantially fire-resistant material stacked one on top of another, and at least one row of contractible substantially fire-resistant block-like members adapted to contract without loss of structural integrity when the wall is subjected to a compressive load, as during a convergence of the floor and roof on the passageway. Each block-like member is preferably a hollow metal member which, when subjected to a compressive load, is adapted to contract heightwise of the member a distance corresponding to at least a major portion of the height of the member without loss of structural integrity of the member.