Patent Application
20130343822
This application relates generally to systems for protecting against falling rock in mines, tunnels and other environments and, more particularly, to a sprayable system that is applied to provide such protection.
One standard process for protecting workers and equipment in mine and tunnel bores against falling rock utilizes a steel mesh that is applied to the rock surface using bolts. After installation of the steel mesh shotcrete is applied. The shotcrete is heavy, slow to dry and tends to crack as the ground moves behind it.
It would be desirable to provide a light weight system that is rapid to dry and flexes as the ground behind it moves, (ii) a system that can be installed before or after any steel mesh and bolts are installed or without such meshing and/or (iii) a system that can also provide effective sealing.
A multi-layer liner system is provided, which may be applied using a spray process, where the initial layer facilitates adhesion to the earthen surface (e.g., rock wall surface) and a subsequent layer provides strength and elongation needed to maintain support system integrity even in the case of some rock movement at the wall surface. In one implementation, the initial layer is a structural foam primer layer and the subsequent layer is a fire-resistant top coat layer.
The liner system can be used to provide structure support to the earthen surface and/or for sealing of the earthen surface.
The liner system can be used in combination with a mesh structure, which can be applied before or after the application of the layers, but can also be used without such a mesh structure.
In one aspect, a method is provided for applying a liner system to an earthen surface such as a mine wall, tunnel bore wall or other earthen wall. The method involves (a) utilizing a plural component spray process to apply a structural foam primer layer in the nature of a first polyurethane or polyurea compound onto the earthen surface, the compound capable of adhering to wet surfaces; and (b) subsequent to step (a), utilizing a plural component spray process to apply a fire-resistant top coat layer in the form of a second polyurethane or polyurea compound that is different than the first polyurethane or polyurea compound.
In one implementation of the foregoing aspect, the modulus of the of the first polyurethane or polyurea compound is higher than the modulus of the second polyurethane or polyurea compound, the tensile strength of the of the first polyurethane or polyurea compound is lower than the tensile strength of the second polyurethane or polyurea compound, the ultimate elongation of the of the first polyurethane or polyurea compound is lower than the ultimate elongation of the second polyurethane or polyurea compound and the elastic elongation of the of the first polyurethane or polyurea compound is lower than the elastic elongation of the second polyurethane or polyurea compound. The first layer will adhere to a variety of surface conditions in an underground environment, including dry rock and wet/damp rock. The first layer will fill in voids (cracks) in the underground rock faces and will provide a “gluing effect” to prevent loose debris and rock from breaking away from the surface. The second coat of the system has the high elongation to allow for rock movement while maintaining the integrity of the support system.
In one implementation, the structural foam primer layer is applied in at least first, second, third and fourth passes, each from a respective first, second, third and fourth direction, to assure coverage of irregularities in the earthen surface.
In instance of the foregoing implementation, the fire-resistant top coat layer is also applied in multiple passes.
In one embodiment, the structural foam primer includes an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant and (iii) a foaming agent, and the fire resistant top coat layer includes an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant.
In one implementation of the foregoing method, the structural foam primer layer is applied at an average thickness of between about 100 mils and about 6000 mils, and the fire resistant top coat layer is applied at an average thickness of between about 100 mils and about 500 mils.
In another aspect, a method is provided for applying a support system that reduces risk of falling rock or debris from an earthen surface such as a mine wall, tunnel bore wall or other earthen wall. The method involves (a) utilizing a plural component spray process to apply a structural foam primer layer onto the earthen surface, the structural foam primer including an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant and (iii) a foaming agent to create a foaming characteristic having the ability to adhere to wet surfaces; and (b) subsequent to step (a), utilizing a plural component spray process to apply a fire-resistant top coat layer over the structural foam primer layer, the fire resistant top coat layer including an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant, but not including any foaming agent.
In one implementation of the foregoing method, the structural foam primer layer is applied at an average thickness of between about 100 mils and about 6000 mils, and the fire resistant top coat layer is applied at an average thickness of between about 100 mils and about 500 mils.
In one implementation, the structural foam primer layer has a color that is distinct from a color of the fire resistant top coat layer, enabling a visible inspection to assure proper coverage.
In one implementation, the method also involves, subsequent to applying the fire resistant top coat layer, attaching a mesh retaining structure by applying a plurality of bolts through the fire resistant top layer and the structural foam primer layer and into the earthen surface, and attaching the mesh retaining structure to the bolts.
In another implementation, prior to applying the structural foam primer layer, a mesh retaining structure is applied by applying a plurality of bolts into the earthen surface, and attaching the mesh retaining structure to the bolts.
In one embodiment, the isocyanate of the structural foam primer layer is a diisocyanate and the isocyante of the fire resistant top coat later is a diisoycanate.
In one implementation of the foregoing embodiment, the diisocyanate of the structural foam primer layer is 4,4-diphenylmethane diisocyanate, and the diisocyanate of the fire resistant top coat layer is selected from the group consisting of isophorone diisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate or hexamethylene diisocyanate.
In one implementation, the strength of the fire resistant top coat layer is greater than the strength of the structural foam primer layer.
When properly applied, the structural foam primer layer may fill small cracks in the earthen surface and adheres earthen material on opposite sides of such cracks together.
In another aspect, a liner system applied to an earthen surface of a mine wall, tunnel bore wall or other earthen wall includes a plural component structural foam primer layer adhered to the earthen surface, the structural foam primer including an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant and (iii) a foaming agent; and a plural component fire-resistant top coat layer over the structural foam primer layer, the fire resistant top coat layer including an isocyanate in combination with (i) one or more of an alcohol, a hydroxyl, a polyol or an amine and (ii) a fire retardant, but not including any foaming agent.
The structural foam primer layer may have an average thickness of between about 100 mils and about 6000 mils, and the fire resistant top coat layer has an average thickness of between about 100 mils and about 500 mils. However, variations are possible depending upon a variety of factors such as surface profile (depth of voids in the rock surface), desired visual appearance, or variable in engineering of the applied system.
The structural foam primer layer may have a color that is distinct from a color of the fire resistant top coat layer. During installation, this color difference can be observed by the installer, or by a subsequent inspector, to verify the continuity and completeness of the liner system.
A mesh retaining structure (e.g., wire mesh) may be located to the exterior of the fire resistant top coat layer. A plurality of bolts may be used to attach the mesh, where the bolts extend through the fire resistant top coat layer and the structural foam primer layer and into the earthen surface. Holes may be drilled through the layers and into the earthen surface in order to received such bolts. Alternatively, the mesh retaining structure may be applied prior to spraying of the layers, such that the mesh is embedded at least partially within one or both of the structural foam primer layer and/or the fire resistant top coat layer. In some case the mesh may not be used at all.
The isocyanate of the structural foam primer layer may be a diisocyanate and the isocyante of the fire resistant top coat later may be a diisoycanate. By way of example, the diisocyanate of the structural foam primer layer is 4,4-diphenylmethane diisocyanate, and the diisocyanate of the fire resistant top coat layer is selected from the group consisting of isophorone diisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate or hexamethylene diisocyanate. By way of example, the primary layer may be Custom Linings Structural Foam Primer and the top coat layer may be Custom Linings 711 FR Fire Resistant Lining, both available from Custom Linings, Inc. of Beuna Vista, Colo.
Referring now to
The method and system described above provides advantages over known shotcrete liner systems. For example, the layers of the present system cure rapidly (e.g., within minutes), providing for a much more rapid speed of installation. The materials utilized also enable application of the liner system to frozen wall surfaces. Moreover, as previously suggested, the present liner system and method can be implemented such that the layers are applied before any application of bolts and mesh, thereby reducing risk of earthen material falling during the application of such bolts and mesh.
As used herein, the term plural component processing technique means blending two or more chemicals together in a specific or varying ratio with either direct impingement equipment, equipment utilizing a static mixer assembly to mix/bled the chemicals or by mixing in an open container by hand or by other mechanical mixing method to produce material that cures to some degree. In the illustrated embodiment, an impingement mix spray process is shown using a spray mechanism 18.
In order to most effectively provide adequate coverage of irregular surfaces (e.g., surfaces with jutting or protruding angular rock structure), the layers may be applied in multiple passes having different spray directions. Generally, at least four passes with at least for different spray directions are desired (e.g., one pass with a left to right movement, where the spray is direction at forty-five degree angle in the direction of movement, one pass with a right to left movement, where the spray is direction at forty-five degree angle in the direction of movement, one pass one pass with a top to bottom movement, where the spray is direction at forty-five degree angle in the direction of movement, and one pass with a bottom to top movement, where the spray is direction at forty-five degree angle in the direction of movement).
It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/662,051, filed Jun. 20, 2012, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61662051 | Jun 2012 | US |
