Method of downhole hydraulicking of mineral resources

The method of downhole hydraulicking of mineral resources consists in sinking main holes, fitting the main holes with casings down to a depth below a lower boundary of a pay-out bed, installing an apparatus for hydraulicking mineral resources in each main hole, breaking rock and forming cavities in a bedrock by a jet from a monitor provided in the apparatus for hydraulicking mineral resources. Auxiliary holes are sunk each above a face of each cavity, using a drilling tool, down to the cavity so that the mineral enters the cavity from the auxiliary hole as soon as the drilling tool is withdrawn therefrom. Pulp is lifted to the surface through the main holes until overburden rock is identified in the pulp.

FIELD OF THE INVENTION 
The present invention relates to mining and has specific reference to 
methods of downhole hydraulicking of mineral resources. 
The present invention may be of utility in the hydraulic mining of solid 
mineral resources and building materials such as clay, sand, phosphate 
rock, peat, oxide-bearing iron and manganese ores, bauxites. 
It may find application in off-shore mining projects, those confined to the 
continental shelf in particular, in erecting underground facilities for 
the storage of gases and liquids and disposing of industrial waste, in 
driving collectors which, on being filled with concrete, can be used as 
strip foundations. 
BACKGROUND OF THE INVENTION 
Widely known in the art is a method of downhole hydraulicking of mineral 
resources (U.S. Pat. No. 3,951,457) according whereto development holes 
are sunk from the surface down to a pay-out bed and casings are installed 
in the holes so that the casing shoes are at least 4-6 m above the face of 
each hole. An apparatus for hydraulicking mineral resources, consisting of 
a monitor located at the lower end of the apparatus and a pulp-lifting 
mans (commonly a jet pump) at the end face of the apparatus, is lowered 
into the casing so that the monitor is below the casing shoe. A liquid, 
pressure-fed into the hole, turns into a high-pressure jet on passing 
through the monitor and breaks the rock. The pulp which forms is lifted to 
the surface. In operation, the apparatus travels upwards and forms 
cavities the floors where slope downward toward the hole so that the pulp 
can flow to the jet pump. 
The prior art method of downhole hydraulicking of mineral resources is 
ineffective in working water-bearing beds and those containing drift sand. 
In incompetent beds, the water jet has a short range and the yield of 
mineral from the cavities is low. As the mineral is being broken and 
removed from the face, a continuous caving in takes place in this case. 
The caving in spreads to the overlaying strata and reached the dead rock 
of the overburden with the result that this rock is lifted to the surface. 
Sagging of the ground surface is a hazard which is very likely to occur in 
practicing the prior art method of downhole hydraulicking of mineral 
resources when shallow pay-out beds are being worked or the overburden is 
an incompetent one. This creates a professional hazard and endangers the 
safety of the hydraulic mining equipment. 
SUMMARY OF THE INVENTION 
It is an object of the invention to enhance the effect of hydraulicking 
mineral resources from water-bearing pay-out beds displaying a drift-sand 
behaviour. 
The essence of the invention is that in a method of downhole hydraulicking 
mineral resources, involving the sinking of main holes, fitting casings 
into the main holes, introducing an apparatus for hydraulicking mineral 
resources, incorporating a monitor and a means of lifting pulp to the 
surface, into each main hole, feeding liquid into the main holes, breaking 
rock and forming cavities by a liquid jet from the monitor of the 
apparatus for hydraulicking mineral resources, lifting pulp to the surface 
through the main holes until the rock constituting an overburden is 
identified in the pulp, according to the invention the main holes are sunk 
and provided with the casing down to a depth below a lower boundary of a 
pay-out bed and the cavities formed by the jet from the monitor of the 
apparatus for hydraulicking mineral resources in breaking the rock in each 
main hole are located in a bedrock, whereby, after the cavities have been 
formed in the bedrock, auxiliary holes are sunk above faces of the 
cavities with the aid of a drilling tool so as to become connected to the 
cavities with the result that the mineral enters the corresponding cavity 
from the pay-out bed as soon as the drilling tool is withdrawn from the 
corresponding auxiliary hole. 
It is expedient to install means of hole reaming in the auxiliary holes and 
to ream these holes through a distance between the connection of each 
auxiliary hole with the corresponding cavity and the rock of the pay-out 
bed in order to enhance the effect of hydraulicking mineral resources. 
It is also expedient to form cavities from each main hole in a direction 
opposite to that sunk in which are the subsequent main holes in order to 
ensure safety for the personnel and the ground equipment for hydraulicking 
mineral resources. 
The present invention contemplates the location of the cavities in the 
bedrock and an extension of the range of breaking the rock, therefore its 
implementation creates the prospect of enhancing the effect of 
hydraulicking mineral resources from water-breaking bed with drift-sand 
behaviour which offer low gain of worked by conventional mining and 
open-cast methods.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The method of downhole hydraulicking of mineral resources consists in the 
following. 
Referring to FIG. 1, main holes 1 are sunk from the surface of the earth 
(or, alternatively, from an off-shore rig or a mine working) to a depth 
below a lower boundary 2 of the pay-out bed 3. A metal casing 4 is 
installed in each main hole 1 so that a lower end face 5 of the casing 4 
is below the lower boundary 2 of the pay-out bed 3. An annular space 
formed between the lower end face 5 of the casing 4 and the rock of the 
pay-out bed 3 is filled with concrete which, on being set, serves as a 
hydraulic seal 7 of the main hole 1 at the interface between the pay-out 
bed 3 and a bedrock 6. A concrete plug formed in the main hole 1 is 
drilled out. An apparatus 8 for hydraulicking mineral resources, 
incorporating a monitor 9 and a means of lifting pulp to the surface in 
the form of a jet pump 10, is installed in each main hole 1 so that the 
monitor 9 is located at a depth below the lower end face 5 of the casing 
4. 
The distance between the lower boundary 2 of the pay-out bed 3 and a face 
11 of each main hole 1 is decided by the distance between the lower 
boundary 2 of the pay-out bed 3 and the lower end face 5 of the casing 4, 
which is 1-1.5 m, the length of the apparatus 8 between the monitor 9 and 
a lower end face 12 of the apparatus 8, which is 2-3 m, and the depth of a 
sump 13 of the main hole 1 accumulated wherein is pulp, which is 1-2 m. 
Adding up, the distance between the lower boundary 2 of the pay-out bed 3 
and the face 11 of each main hole 1 is roughly 4-6 m. 
A liquid, which can be industrial water containing sediments and chemical 
admixtures, is pressure fed into the main holes 1, reaching the monitor 9 
of each apparatus 8. A high-pressure jet issuing from the monitor 9 breaks 
the bedrock 6 to form a crater which is then transformed into a cavity 15 
as the monitor 9 of the apparatus 8 is smoothly displaced along an axis 14 
of the main hole 1. Next, the monitor 9 of the apparatus 8 is returned to 
the initial depth, turned towards the location of a next cavity 15 and set 
to operate so as to form this cavity. Continuing in this way, all the 
vertical cavities 15 (FIG. 2) are formed within a cavity sector 16. The 
floor 17 (FIG. 1) of the cavities 15 makes an angle .alpha. of 
5.degree.-7.degree. with the horizontal so that the pulp resulting from 
the breaking of the bedrock 6 can flow into the sump 13 of the main hole 1 
due to gravity. An upper wall 18 of each cavity 15 is located close to the 
lower boundary 2 of the pay-out bed 3, i.e. roughly at 1- 1.5 m, provided 
the monitor 9 is set horizontally. Since the monitor 9 of the apparatus 8 
works at a depth which is below the lower boundary 2 of the pay-out bed 3, 
is operating range is at its maximum (11-13 m) which is used to form 
cavities 15 in the bedrock 6 without providing the cavities 15 with a 
connection to the pay-out bed 3. The cavities 15 are thus formed from the 
main holes 1 in a dewatered rock so that the high-pressure monitors 9 of 
the apparatus 8 operate at their maximum effective range and the rate of 
breaking the bedrock 6 is at its maximum as well. 
The axis of the monitor 9 of each apparatus 8 and the high-pressure jet 
issuing from the monitor 9 are directed at right angles to the axis 14 of 
the main hole 1. In sand and clay, the sloping floor 17 of the cavities 15 
is formed due to an erroding effect of the pulp flowing from the face 19 
of the cavity 15 to the sump 13 of the main hole 1. In competent rock, the 
sloping floors 17 of the cavities 15 are formed with the aid of the 
high-pressure jet of the monitor 9 the axis whereof makes a small angle 
with the axis 14 of the apparatus 8 for hydraulicking mineral resources. 
Auxiliary holes 20 are sunk successively down to the cavities 15 so as to 
become connected thereto, using a drilling tool 21 with a bit 22. They are 
located above the faces 19 of the cavities 15 at a distance from the main 
hole which equals the maximum range broken whereat is the bedrock 6. On 
withdrawing the bit 22 from each auxiliary hole 20, the mineral is 
discharged into the corresponding cavity 15. 
Each auxiliary hole 20 some 180-250 m in diameter clears the way, on being 
connected to the corresponding cavity 15, for the mineral of the pay-out 
bed 3 to proceed to the main hole 1 via the cavity 15, provided the 
drilling tool 21 is removed from the auxiliary hole 20. Ater that the 
drilling rig is dismantled and the personnel is sent away from the mouth 
of the auxiliary hole 20. 
Means of hole-reaming are lowered into the auxiliary holes 20 to ream them 
through distances between their conections to the cavities 15 and the rock 
of the pay-out bed 3. The reaming operations produces chambers 23 with a 
diameter which is 3-5 times that of the auxiliary holes 20. 
Suitable for use as the hole-reaming means are mechanical reamers, monitors 
and explosives. The rock extracted from the pay-out bed 3 falls into the 
sump 13 of the main hole from the cavity 15, where the inlet into the jet 
pump 10 of the apparatus 8 is located, and is lifted to the surface by the 
apparatus 8. 
The lifting of the pulp to the surface over the main hole 1 goes on until 
the rock of the overburden 24 is identified in the pulp. The apparatus 8 
is withdrawn then from this hole and fitted into the next one. 
Referring to FIG. 2, the cavities 15 are formed from each main hole 1 and 
the auxiliary holes 20 are started towards the faces 19 of the cavities 15 
in a direction opposite to that sunk in which are the subsequent main 
holes 1. The arc of the sector 16 formed wherein are the cavities 15 from 
each main hole 1 is decided by the geological features of the bedrock 6 
and the drift-sand behaviour of the pay-out bed 3. The arc of the sector 
16 should not exceed 180.degree.. 
On extracting all the mineral, the overburden 24 (FIG. 1) may sag so that a 
trough 25 is formed above the auxiliary holes 20 but this is located at a 
distance from the mouth of the depleted main hole 26 so that no danger 
exists for the equipment and personnel. 
The downhole hydraulicking of mineral resources enhances the effect of 
hydraulic mining and ensures safety for the ground equipment and 
personnel.