US 3469405 A
Description (OCR text may contain errors)
P 1969 R. H. REINHOLD 3,469,405
MINE WATER BARRIER Filed Aug. 14, 1968 I "I 9E Y "J L AAM Fig.1 5
. INVENTOR. 5
RichardHReinlm/d HIS ATTORNEYS" United States Patent 3,469,405 MINE WATER BARRIER Richard H. Reinhold, Pittsburgh, Pa., assignor to Layne- New York Company, Inc., a corporation of New York Filed Aug. 14, 1968, Ser. No. 752,683 Int. Cl. E02d 19/12; E2112 17/16; E02b 7/02 U.S. C]. 61-35 7 Claims ABSTRACT OF THE DISCLOSURE A method of constructing a mine water barrier in an underground mine entry by making two substantially parallel rows of borings transversely of the entry, feeding mineral aggregate into the entry through the borings, and grouting the aggregate. The grouted aggregate sets up to form a pair of walls spaced longitudinally in the entry. A number of holes are drilled between and parallel to the borings into the entry. Additional mineral aggregate and/or cementitious fill material is fed under pressure through the holes into the entry between the walls and permitted to set up to form a substantially water impervious barrier.
This invention relates to water barriers and particularly to a method of constructing a barrier for preventing water from flowing through an underground mine entry and onto ground surface.
Abandoned underground mines present large problems to land conservation and reclamation activities. Not only have they interfered with use of the ground surface above them, due to weakened ground support, but also provide serious health hazards to persons living and/or recreating near them. One critical menace to health is the presence in mines, particularly coal mines, of water which is acid and contaminated, for example by oxidation of pyrites, etc. in the exposed, deserted coal measures. In many coal mines, the mine entry extends a great distance into the side of the coal-bearing hill from the mine entrance. Mining of these hills generally was carried out by opening rooms off the entry, and taking coal out of the rooms through the entry to daylight at the mine entrance.
Over the years, surface water has continuously drained into the mines, and taking the path of least resistance, has exited from the mines through the entry, forming pools of stagnant and contaminated water near the mine entrance.
Previous attempts to prevent the formation of such hazardous pools have included building concrete, masonry or cement bulwarks across the entry only at the mine entrance, or cutting back a substantial portion of a hill side to present a large, flat rock face against which a similarly sized concrete darn structure was constructed. Neither method has proved entirely satisfactory, since, in the first case, the mine water has merely passed through the rock adjacent the closed mine entry; and in the second case, ground excavation and dam construction costs, including materials, have been so excessive as to make this method economically unfeasible.
I have invented a new method of constructing a mine water barrier useful for sealing a mine entry to prevent contaminated water from escaping from a mine through the entry. My method also provides for sealing of rock formations adjacent the mine entry and can be modified to seal rock a substantial distance above the part of the barrier in the entry itself.
Briefly, my invention is a method of building, from ground surface, a barrier in a mine entry usually a substantial distance below the ground. Two support walls are spaced longitudinally from one another across the entry. They are constructed in the following manner. Two spaced rows of borings, each of which boring is usually 3,469,405 Patented Sept. 30, 1969 six inches in diameter, are made in the ground surface above and across the mine entry. The borings may extend through the entry into the rock floor thereof, for instance a distance of about six inches, to provide a SOlld footing for the barrier, i.e., one which is not founded on gob (waste material left in the entry) or roof cave (material which has fallen from the ceiling of the entry). Mineral aggregate material, such as gravel, is gravity fed through each of these borings into the mine and tamped from surface level to provide a firm, substantially frusto-conical support having its largest diameter on the entry floor and which extends to the entry ceiling. Finally, liquid or fiowable grout is forced through a grouting tool lowered into the borings and into each gravel support. When the grout sets up, a pair of substantially water-tight walls are formed. By constructing these support walls in this manner, they have a substantial contact with the ceiling of the entry adjacent the boring while the size of the base of the wall is controlled.
A row of holes is then made from ground surface into the entry. These extend between the support walls and across the entry. Additional mineral aggregate material, either larger or similar to that used to form the supports for the Walls, fly ash, concrete or other cementitious material is gravity fed or blown under pressure through these second or middle holes into the area in the entry between the walls. If material, as gravel, is used, the material is grouted as before. If fly ash or cement is used, it will set up. In either case, upon hardening of the materials used, the combination of the walls and fill in the central area form a substantially water impermeable barrier.
As the grouting tool is withdrawn from the entry through the borings, additional grouting material may be pressure fed at vertically spaced intervals into the rock formation adjacent the borings to seal any rock fissures above the entry. This provides a substantially watertight barrier above the entry in the rock to withstand a head of water behind the barrier and borings.
An understanding of my invention will result from the following description, and the accompanying drawings wherein:
FIG. 1 is a perspective phantom view taken along a wall of a mine entry of a barrier made in the mine by the method of my invention; and
FIG. 2 is a cross sectional view of a single row of borings extending into a mine entry and showing schematically a suitable grouting tool for use in practicing my invention, and a modification of my invention.
In FIG. 1, I have illustrated a mine entrance 2 which is opened in the slope 3 of a coal-bearing hill. An entry 4 extends a substantial distance from the entrance into the hill. A barrier 5, according to my invention, is positioned far into the entry and at great depth below ground surface 6.
The barrier constructed according to my method comprises a pair of support walls 7, 8 which extend across the entry. The support walls are spaced from one another longitudinally in the entry, leaving an area 9 within the entry.
In constructing my mine water barrier, a first row of borings 10 are made in the ground surface 6 above and across the mine entry 4. The borings are preferably six inches in diameter but may be larger or smaller crosssection. Each boring 10 extends into the entry 4, and may extend into the floor 11 a depth 11a (FIG. 2) of approximately six inches. Where gob or roof cave covers the floor at the point of boring, it is believed necessary that the additional depth be bored to provide a solid footing for my barrier.
A second row of borings 12 are then made across the entry 4 from surface 6 in the same manner as the borings 10. The borings 10, 12 are preferably equally spaced across the entry. For example, for a foot wide by 4 foot high entry, five borings are made in each row; they are spaced from each other on two foot centers.
The rows of borings 10, 12 are made substantially parallel to one another and are spaced from one another. The distance between the rows, and thus the walls, depends upon the head of water to be contained behind the barrier; the greater the pressure of the water, the greater the distance required between the walls.
After the borings 10, 12 have been made, a grouting tool such as a flush joint tube having approximately a 2 /2" diameter is dropped into a boring. Although there is no specific order in which the borings must be made or filled, I prefer to use as a starting point, a boring at one end of one of the rows of borings 10, 12 and work therefrom across the mine entry.
A preferred flush joint tube construction is shown in FIG. 2. Briefly, it comprises a casing 13 having a length such that it extends from the bottom of a boring to ground surface and above. An end cap 14 closes the casing at the lower end of the tube and provides a tamping surface. Adjacent the end cap and extending approximately one foot along the length of the casing, there are a number of holes or perforations 15 which surround the tube casing.
A barrier wall is made according to my method by feeding the aggregate or gravel into the entry through the starting boring to form a cone-shaped mound of gravel. The gravel is then compacted by reciprocating the casing 13 of the flush joint tube from above ground to cause the end cap 14 to tamp the apex of the cone. As the gravel mound is compacted by tamping, additional gravel is gravity fed onto the top of the mound and tamped, the feeding and tamping of the gravel continuing until the gravel reaches ceiling 16 of the entry. To cause the gravel to slump and thus form a broad based cone, air, water and/ or fly ash may be introduced during the feeding and tamping of the gravel. Preferably, feeding and tamping is stopped when the gravel forms a frusto-conical support between the entry floor and ceiling. The top of the support, based upon an entry having a four foot height, extends approximately one foot radially around the boring at the entry ceiling. Several borings may be gravel-filled and tamped simultaneously. The objective is to form a number of supports, each having substantial contact with the ceiling of the entry to form a firm gravel wall across the entire entry.
After the gravel is formed into the firm structure support, the flush joint tube is forced through the gravel to the floor of the entry. Grouting material is pressure fed into the gravel supports. The grouting tool is lifted periodically to spread the grout throughout a support. When all the gravel supports in a row have been grounted, these supports arranged across the mine entry set up to provide a firm wall, as shown at 7 in FIG. 1. A similar procedure of filling the borings is followed to make parallel wall 8.
The area 9 between the two walls in the entry is then filled to complete my barrier. This is done by making or boring from ground surface a number of holes 17 in a row which is substantially parallel to the two rows of borings 10, 12. Preferably, these holes are at least six inches in diameter, although they may be larger or smaller. For a ten foot entry width, I prefer to make three such holes.
The area 9 between the walls is determined by the dimensions of the entry and the spacing and configuration of the walls. Where the entry floor is not solid, i.e., when 'gob or roof cave are present in the area between the walls,
it is preferable that the floor between the walls not be covered by gravel. In FIG. 1, again based upon an entry ten feet by four feet, this is approximately twenty square feet of floor 11.
The walls 7, 8 are allowed to set up or harden providing a solid mass against which to pressure grout the area 9. If not set up, the grout would flow freely through the walls and be wasted. Mineral aggregate or gravel is then gravity fed through holes 17 to substantially fill the area 9. The gravel may be grouted and tamped to make a firm fill structure 9a. The structure 9a may be made using the same size gravel as that used in making the two walls 7, 8 or may be made of larger or smaller gravel. It is important to the stability and integrity of the barrier that the fill used in the area 9 be as homogeneous a mass as possible, and that the fill mixture be compatible with the materials forming the walls of my barrier.
A cement may also be used in the area 9. It should have, preferably a 500 pound concrete compressive strength (p.s.i.) to provide a strong, water tight barrier when it sets up. It is particularly desirable to use cement in the area 9 if gob is present.
A barrier support having great strength against water pressure is achieved, as shown in FIG. 2, by inserting a tube 18 into a cone of gravel before grouting the gravel to form the barrier Walls 7 and 8. This tube, preferably, is ordinary pipe having a 1 /2 nominal diameter. The pipe is lowered into a hole 10 on the end of a length of connected pipe and is joined to the lower end thereof by a separable connection, such as a left hand-right hand coupling. When the pipe is completely in the hole, this connection is slightly above the ceiling of the entry. After the pipe is completely lowered into the entry, additional gravel is fed around it and grouted. When the grout sets up, the pipe 18 is embedded in the fill 9a providing additional stability. The upper pipe lengths are then backed out of the hole separating them from the embedded pipe 18 at the coupling. A pipe 18 may be used in any or all of the borings 10, 12 and 17 in the same manner.
Many types of grouting are suitable for use in my barrier construction. I prefer to use a fiowable grout comprising 3 parts fly ash and one part portland cement, commonly known as Type II portland. To promote setting up of the grout, a silica gel additive can also be used, or a caustic solution or accelerator. Various commercial grouts are satisfactory including those grouts derived from a gel base, a reactant and accelerator, or a silicate, an amide, chloride, aluminate, bicarbonate and cement.
In a further modification of my invention, we apply grouting principles to the rock above the entry immediately adjacent the barrier in the entry. In any one or all of the borings 10, 12 and holes 17, grout is placed under pressure through the borings and into the rock voids and fissures in the area 19 above the entry. By grouting the rock areas above the main barrier in the entry, from each boring, it is practicable to make a pair of substantially water tight dams above the barrier. Then grout is pumped through the holes against the dams under pressure to seal the rock area above the barrier. Such a construction enables great heads of water to be retained in the mine behind the barrier. Destruction of open areas, such as lakes, ponds and streams by contaminated water is thus prevented.
My barrier is economical to construct since earth moving costs are avoided and drilling methods are used. The bulk materials used, such as gravel, fly ash, sand and cement and the like are relatively inexpensive to purchase and apply.
Although I have described a preferred embodiment of my invention, it is understood that it may be otherwise embodied within the scope of the appended claims.
1. A method of constructing from ground level a barrier for preventing water from escaping an underground entry comprising:
(1) making a first row of borings from ground level into the entry and laterally across the entry;
(2) making a second row of borings from ground level into the entry and laterally across the entry, the rows being spaced from one another longitudinally in the entry;
(3) feeding and tamping sufiicient mineral aggregate into each of the borings to close the entry and grouting said aggregate to form a pair of spaced support walls;
(4) drilling holes between the support walls; and
(5) filling the space between the support walls with cementitious aggregate whereby the aggregate fill and the walls will set up to form :a substantially impervious Water barrier in the entry.
2. The method set forth in claim 1 wherein at least one of the borings and the holes are drilled substantially simultaneously.
3. A method as set forth in claim 1 in which the walls in the entry are permitted to substantially set up before filling aggregate into the entry between the walls.
4. The method set forth in claim 1 including drilling the borings to extend through the entry and into the entry floor.
5. The method set forth in claim 1 including inserting a pipe length into one of the borings and holes through the mineral aggregate to provide additional strength to the barrier.
6. The method as set forth in claim 1 and including the area between the borings and holes over the entry and below ground level above the barrier.
7. A method of building a support wall in an underground entry against which cementitious aggregate can be pressure cast comprising the steps of:
(1) making a row of borings from ground level laterally across the entry;
(2) alternately passing loose mineral aggregate into the entry through the borings and performing a step for causing the aggregate to extend across the entry and to have substantial contact with the ceiling of the entry; and
' (3) filling the interstices of the aggregate with a cementitious grouting material, whereby the support wall formed will be substantially impervious to OTHER REFERENCES Civil Engineering and Public Works Review (Great Britain), August 1963, p. 1006.
JACOB SHAPIRO, Primary Examiner US. Cl. X.R.