US 3478520 A
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United States Patent 3,478,520 METHOD FOR FILLING ABANDONED MINES Albert Andy, Washington, Pa., assignor of one-fourth each to Anthony Andy, William Andy, and Victor Andy, all of Washington, Pa. No Drawing. Filed Nov. 16, 1967, Ser. No. 683,482 Int. Cl. E02d 27/32; E21f 15/.00
US. Cl. 61-35 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method for filling abandoned mines or mine cavities with a material which will completely fill such mines or mine cavities as the result of application of heat to the material when located in the mine so as to serve also as a strong mechanical reinforcement for the roofs of the mines and cavities.
In the past, various methods have been used for partially filling or reinforcing abandoned mines and mine cavities, such as the erection of posts or pillars to support mine roofs and the introduction of concrete, a rather expensive material, to form such pillars to partially fill such cavities and adequately support the ground thereabove to prevent subsidence. While these methods have been at least partially successful, they have not provided a complete filling of the voids or cavities and therefore have permitted an objectionable amount of subsidence or withdrawal of support of foundations for homes and other structures resulting in cracking the walls and sinking of foundations, causing considerable expense for reconstruction without assurance that the subsidence will not recur.
An outstanding disadvantage of such methods has been not only the ineffectiveness in preventing subsidence but the very high cost involved in the use of concrete that is, lime, sand and gravel, since mines involve very large volumes of air space that must be filled.
An object of my invention is to overcome the above named disadvantages of presently used methods for reinforcement of mine roofs or for partially filling mine cavities.
A further object of the invention is to provide a comparatively inexpensive method for completely filling mine cavities and at the same time providing a very strong mechanical support for the roofs or ground structure above so as to eliminate any possibility of subsidence.
Another specific object of the invention is to introduce, into mine cavities, a granular material which will expand many fold as a consequence of the application of heat, such as an expandable polystyrene, so as to completely fill an abandoned mine and its various cavities with a minimum of effort and expense, as well as a minimum amount of time, so as to make such method very inexpensive and therefore highly practical.
In accordance with the present invention, a material is used which will have the characteristics of expanding many fold when placed in a mine cavity or any other cavity in the ground, also which will have adequate structural strength when expanded to support mine roofs or layers or strata of coal or earth thereabove to avoid the possibility of subsidence of structures built on the ground surface. I have found that expandable polystyrene ice has this unique quality, as well as the additional unknown characteristic of not being subject to deterioration, after expansion in ground cavities, by mine acid, water streams and the like which are usually present.
However, in order to expand such polystyrene, it is necessary to apply a predetermined amount of heat in order to initiate expansion and to continue such expansion until the volume of polystyrene expands many fold. Various ways may be employed for introducing such heat into mine cavities. For example, steam heated pipes may be introduced through hollow shafts sunk through the top layers above the mine cavities, with heating coils extending into or immediately adjacent the granular expandable material in the mine cavities so as to apply the necessary heat to initiate expansion of the polystyrene.-
Instead of steam, propane gas may be introduced to supply a burner adjacent the granular expandable material in the mine cavity. Still another means is an electric heating coil which is energized by a supply line introduced in a similar manner as the steam pipes, which coil is placed immediately adjacent the polystyrene to apply sufiicient heat for complete expansion thereof to enable the filling of mine cavities and voids. The expandable polystyrene is preferably of a granular size slightly greater than that of sugar.
In some instances, exothermic materials may be mixed with the polystyrene particles, such as those used in exothermic sideboards for ingot molds to prevent piping, which exothermic materials can be ignited so as to give off heat by the application of a predetermined igniting temperature. Such exothermic materials are well known in the art, therefore, any of such materials may be mixed with the expandable polystyrene particles so as to generate or give 01f a certain amount of heat after a predetermined temperature or heat has been applied thereto, such as by the methods described above. In short, any used for the purpose of initiating expansion of the exmethod of introducing heat into the mine cavities may be used for the purpose of initiating expansion of the expandable polystyrene or equivalent material.
Unusual and unexpected characteristics of the polystyrene when in expanded condition are the remarkable and amazing structural strength which provides very strong support for the roof of the mined areas and uniform distribution of the roof load throughout the entire area that is mined so as to prevent any concentration of loading on any one single pillar or several pillars, such as used in the past, which are subject to failure in spite of the very high expense involved in the construction of such pillars, or in the wasteful leaving of unmined pillars solely to serve as supports.
Still another unusual characteristic providing unexpected results by the expanded polystyrene is its great resistance to mine acid drainage or to underground streams, as well as to air and moisture, that is, its-stability or.tendency not to disintegrate as a consequence of continual exposure to mine acid, underground streams dampness, etc.
While I have described granular, expandable polystyrene as a very suitable material to accomplish the purposes of the present invention, it should be understood that others, after having had the benefit of the present disclosure, may select other full chemical equivalents, that is, materials which can be expanded by the application of heat, to provide a similar cellular structure with similar characteristics. Instead of applying heat to initiate expansion, other known means may be used instead, such as the use of catalysts, exothermic materials or the like to initiate and to continue expansion until complete filling of the mines or mine cavities has been accomplished.
Thus it will be seen that I have provided a highly efficient and eifective method for filling abandoned mines and mine cavities, which method can be accomplished more quickly and inexpensively than heretofore possible so as to make it practical, for the first time, to completely fill all voids of mine cavities and thus provide suflicient structural support to prevent subsidence, as well as to completely fill the voids and thus prevent introduction of underground streams which could become polluted with acids as a consequence of infiltration in the mines cavities.
I claim: I
1. The method of filling mines and underground cavities in a manner so as to adequately reinforce the ground thereabove in order to prevent subsidence, comprising introducing into said mines and cavities particles of expandable plastic material having the property of expanding many fold upon the application of heat and having high structural strength and resistance to mine acid drainage, moisture and air, sinking, through the ground surface above said mines and cavities, supply lines for applying heat in contiguous relationship to said particles of expandable plastic material sufficiently to initiate and con- References Cited UNITED STATES PATENTS 3,294,602 12/ 1966 Francis et al. 264-45 X 3,311,575 3/1967 Graham 260-25 3,320,188 5/1967 Dijkema 26025 3,340,693 12/1967 Row 61-36 3,388,195 6/1968 Christenson 264-45 JACOB SHAPIRO, Primary Examiner US. Cl. X.R.