Liner system for mines, tunnels and other ground structures

Abstract

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.

What is claimed is: 
     
         1 . A method of applying a liner system to an earthen surface such as a mine wall, tunnel bore wall or other earthen wall, comprising:
 (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.   
     
     
         2 . The method of  claim 1  wherein 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 is of the of the first polyurethane or polyurea compound is lower than the elastic elongation of the second polyurethane or polyurea compound. 
     
     
         3 . The method of  claim 1  wherein 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. 
     
     
         4 . The method of  claim 3  wherein the fire-resistant top coat layer is applied in multiple passes. 
     
     
         5 . The method of  claim 4  wherein the structural foam primer layer is applied with an average thickness that is at least 3 times greater than an average thickness of the applied fire-resistant top coat layer. 
     
     
         6 . A method of applying a liner system to an earthen surface such as a mine wall, tunnel bore wall or other earthen wall, comprising:
 (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;   (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.   
     
     
         7 . The method of  claim 6  wherein:
 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. 
 
     
     
         8 . The method of  claim 6  wherein the structural foam primer layer has a color that is distinct from a color of the fire resistant top coat layer. 
     
     
         9 . The method of  claim 6 , further comprising:
 (c) subsequent to step (b), 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.   
     
     
         10 . The method of  claim 6 , further comprising:
 (c) prior to step (a), attaching a mesh retaining structure by applying a plurality of bolts into the earthen surface, and attaching the mesh retaining structure to the bolts.   
     
     
         11 . The method of  claim 6  wherein the isocyanate of the structural foam primer layer is a diisocyanate and the isocyante of the fire resistant top coat later is a diisoycanate. 
     
     
         12 . The method of  claim 11  wherein:
 the diisocyanate of the structural foam primer layer is 4,4-diphenylmethane diisocyanate; 
 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. 
 
     
     
         13 . The method of  claim 6  wherein a strength of the fire resistant top coat layer is greater than a strength of the structural foam primer layer. 
     
     
         14 . The method of  claim 6  wherein the structural foam primer layer fills small cracks in the earthen surface and adheres earthen material on opposite sides of such cracks together. 
     
     
         15 . The method of  claim 6  wherein the earthen surface has a temperature of zero degrees Centigrade or lower. 
     
     
         16 . A liner system applied to an earthen surface of a mine wall, tunnel bore wall or other earthen wall, the liner system comprising:
 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;   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.   
     
     
         17 . The system of  claim 16  wherein:
 the structural foam primer layer has 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. 
 
     
     
         18 . The system of  claim 16  wherein the structural foam primer layer has a color that is distinct from a color of the fire resistant top coat layer. 
     
     
         19 . The system of  claim 16 , further comprising:
 a mesh retaining structure located to the exterior of the fire resistant top coat layer and attached via a plurality of bolts that extend through the fire resistant top coat layer and the structural foam primer layer and into the earthen surface.   
     
     
         20 . The system of  claim 16 , further comprising:
 a mesh retaining structure embedded at least partially within one or both of the structural foam primer layer and/or the fire resistant top coat layer.   
     
     
         21 . The system of  claim 16  wherein the isocyanate of the structural foam primer layer is a diisocyanate and the isocyante of the fire resistant top coat later is a diisoycanate. 
     
     
         22 . The system of  claim 21  wherein:
 the diisocyanate of the structural foam primer layer is 4,4-diphenylmethane diisocyanate; 
 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. 
 
     
     
         23 . The system of  claim 16  wherein a strength of the fire resistant top coat layer is greater than a strength of the structural foam primer layer. 
     
     
         24 . The system of  claim 16  wherein the structural foam primer layer fills small cracks in the earthen surface and adheres earthen material on opposite sides of such cracks together.