RU2258810C2 - Method for kimberlite pipe development under difficult hydrogeological conditions - Google Patents

Abstract

FIELD: mining industry, particularly crystal-saving diamond mining when developing permafrost kimberlites under difficult hydrogeological conditions of permafrost zones.

SUBSTANCE: method involves loosening rock, converting rock into pulp and conveying pulp through pulp line by dredger. Before subpermafrost zone opening hole having large diameter is driven from pit bottom for the full depth of field to be developed and inclined borehole is built. The borehole is connected to the hole in point located at said depth and then high-pressure subpermafrost brine is pumped into the pit. Airlift dredger is arranged on water body surface, ripper-dozer provided with all-purpose boring bit is lowered on pit bottom. Loosening of kimberlites weakened by brine is performed by ripper-dozer along helical cuts. Fine ore cuttings are conveyed by means of airlift through pulp line to ore mill. Coarse ore cuttings are moved to ground surface to ore storage through hole, caisson drift and inclined borehole provided with skip hoist. Kimberlite pipe development below pit bottom is performed at right angles of faces depreciation without performing overburden operations.

EFFECT: increased gem diamond yield and resource saving due to deep horizons with opened worked-out space development without overburden operations and improved ecological safety.

4 dwg, 1 ex, 1 tbl

Description

FIELD OF THE INVENTION

The invention relates to the mining industry and is created with reference to the development of deep-lying kimberlite pipes in the permafrost zone with complex hydrogeology. The invention is intended for the development of unique diamond deposits in extreme climatic conditions of the North.

State of the art

There is a method of mining in difficult hydrogeological conditions, including the isolation of water entering the quarry from aquifers by constructing hydraulic curtains around the quarry and the subsequent development of drained blocks using open cast mining equipment and technology [1].

The disadvantage of this method is the significant cost of draining the field and for the burial of part of the groundwater (brines) in underground reservoirs or special storage facilities on the surface, which adversely affect the environment.

There is also known a method of working out deep horizons of fields using waterproofing, including the construction of a grouting curtain around a quarry by pumping special grouting solutions into wells under high pressure, which, filling cracks in the rock mass and solidifying, create a protective screen against formation water entering the quarry space, and the development of the field is carried out using open-source technology. In this case, viscous-plastic and quick-setting mixtures are used as grouting mortars [2].

The disadvantage of this method is the high complexity, significant costs and low reliability of such a design. The latter drawback leads to partial “breakthroughs” of formation water into the depleted quarry spaces and complicate mining operations, worsen sanitary and hygienic working conditions at workplaces and, ultimately, allow environmental pollution.

There is also known a method of open-cast mining of mineral deposits, including loosening and loading the rock mass into a mobile hopper-feeder, transporting it to a sump mixer by a conveyor belt, converting rock mass into pulp, pumping the pulp with a mobile dredging plant and further transporting it through the slurry conduit to the concentration plant and hydraulic dump [3].

However, this method is characterized by a limited scope for deposits with loose deposits, allows significant destruction of the environment, polluting water basins. In addition, the application of this method depends on the climatic conditions of the region and the availability of nearby water sources.

Closest to the invention in technical essence is a method of open underwater mining of mineral deposits, including loosening the rock mass in the aquatic environment, lifting the pulp using an airlift and further transporting the rock mass through the slurry line to the concentration plant [4].

The main disadvantage of this method is the limited scope for loose rocks, for rock kimberlites the method may not be acceptable, since rock kimberlites require explosive destruction, which significantly reduces the yield of high-quality crystalline raw materials at the mining stage.

SUMMARY OF THE INVENTION

The essence of the invention lies in the fact that in a method for the development of kimberlite pipes in difficult hydrogeological conditions, including loosening rocks, turning it into pulp and transporting it with a dredger through a slurry line, a large borehole passes to the final mining depth before opening the permafrost aquifers from the bottom of the quarry, an inclined shaft, which is connected at a given depth to the well, after which a sub-permafrost high-pressure brine is launched into the quarry, on the surface the airlift dredger is placed on the pond, a bulldozer-ripper with a shock executive body is lowered to the bottom of the pond, kimberlites pre-softened with brine are loosened by spiral batches, the destroyed small fraction of ore is transported by an airlift through a pulp pipe to the ore processing plant, the ore processing unit is transported to the beneficiary with a skip hoist, they are fed to the surface to the ore depot, and the kimberlite pipe is mined below the bottom of the quarry at vertical angles blanking the sides without stripping.

In the proposed method, new features in comparison with the prototype are:

- development of a new principle of open underwater mining of deep horizons of kimberlite pipes by flooding the quarry space with permafrost brines, softening rocky kimberlites with brine and their subsequent crushing under water by mechanical loosening, lifting the rock mass with an airlift dredger;

- application of the new principle of forming the sides of the deep horizons of quarries at vertical angles without retaining walls and special protective structures;

- the use of a new scheme of dispersion of ore cargo flows into small and large fractions, and the small fraction from the bottom of the quarry is transported to the surface by airlift pulp duct, and the large fraction through a large diameter well, coffer drift and an inclined shaft to the ore warehouse;

- the use of a caisson drift, in which the brine located is squeezed with compressed air into the chamber for squeezed brine.

These new features eliminate the disadvantages of existing methods for developing mineral deposits and provide the following enhanced positive properties:

- application of the new principle of mining kimberlite pipe deposits underwater will reduce mining costs by eliminating the drainage system, drilling and blasting operations when mining ore from permafrost horizons, and will also minimize harmful emissions from quarries into the environment;

- the introduction of a new principle for the formation of open pit walls in the permafrost zone at vertical angles will allow mining in the open pit without overburden operations;

- softening of kimberlites in a brine medium in an explosive-free way, separation of rock into small and large fractions during production with transportation according to different technological schemes will provide a significant increase in the yield of a large class of jewelry diamonds.

The method is illustrated by drawings. Figure 1 on a cross section of a quarry depicts a process diagram of an open underwater mining kimberlite pipe; figure 2 is a plan of the underwater part of the quarry along the line aa; figure 3 - transport and ventilation inclined shafts; figure 4 - scheme for determining the average length of the rollback.

The method is as follows

The quarry of the kimberlite pipe 1 was worked out to the roof of the aquifer 2. After mining the roof of the aquifer, a large borehole 3 passes to a final depth of 4, inclined shafts 5 are connected to the well 3. The produced water is poured into the pit until a reservoir 6 is formed, depth which is determined by the magnitude of the pressure of produced water. A dredger 7 with an airlift 8 and a suction tip 9 is installed on the surface of the reservoir, and a bulldozer-ripper 10 is placed on the bottom of the reservoir. A skip hoist 11 is placed 11. Development of the sub-permafrost part of the kimberlite pipe 1 is carried out as follows. The bulldozer-ripper 10 loosens partially softened rock brim kimberlites with spiral passes 12, starting from the wellhead of large diameter 3 to the final horizon. Moreover, for better destruction of kimberlites, the spiral-shaped passages of the bulldozer are oriented in two opposite directions. Then, using the airlift 8, the resulting fine fraction is extracted and transported through the slurry line to the beneficiation plant 13. A larger ore fraction that has not passed through the airlift is fed with a bulldozer to the wellhead 3, through which the ore, under its own weight, first gets to the gate valves 14 of the well, and then it is loaded into skips 15, which deliver ore to the ore warehouse 16. If it is necessary to repair the skip lift, the brine from the lock drift 17 using the lock gate valves 18 is squeezed into the caisson chamber 19. N The ore is further degraded using the effect of phase temperature fluctuations in the environment of the sharply continental climate of the North, and then finely crushed ore is fed to the beneficiation plant 13. In order to provide ventilation, two shafts 5 are provided, which are interconnected by failures 20. One of the shafts is assembly and serves to moving workers, auxiliary equipment and airing. For normal operation of miners and economical operation of the skip hoist, the inclination angle of both shafts is 30 °.

An example of a specific implementation of the method

To disclose the technical nature and advantages of the proposed method, an example is given where the initial data are taken as follows: N _to - the final depth of the quarry, N _to = 530 m; N _p - the intermediate depth of the quarry (to the roof of the aquifer), N _p = 330 m; γ _p - angle of slope of the side of the quarry in permafrost, γ _p = 49 °; D _p - the diameter of the ore body, D _p = 300 m; K _to - kimberlite fortress on the scale of prof. Protodyakonova, K _to = 5; q _to - volumetric weight of kimberlites, q _to = 2.5 t / m ³ ;

1. The calculation of the reduction in the volume of stripping operations in the contour of the quarry

The reduction in the volume of stripping operations ΔV _k due to the development of ore reserves within the depths of 330-530 m at vertical angles will be:

ΔVk = V _to -V _p -Q _to

where V _to - the volume of the quarry when paying off its sides at traditional angles to the design depth, m ³ ;

V _p - the volume of the intermediate quarry, m ³ ;

Q _to - the volume of ore reserves mined, m ³ .

Using the formula of a truncated cone we find:

where D _to , D _p - the diameter of the quarry on the day surface, respectively, at depths N _to and N _p , m

D _p = D _p + 2H _p * ctgγ _p = 300 + 2 * 330 * 0.87 = 874 m

D _k = D _p + 2H _p (ctgγ _p = 300 + 2 * 530 * 0.87 = 1222 m.

ΔV _k = 160.9 million m ³

That is, when implementing the proposed method for mining a quarry to a depth of 530 m, it would be necessary using conventional technology to remove 160.9 million m ^{3 of} overburden.

2. The rationale for the release of a large class of jewelry diamonds with the proposed method

As an example, the content of jewelry diamonds per 1 m ^{3 of} mined kimberlites is conventionally assumed to be 0.23 ct per cubic meter of kimberlites.

The output of jewelry diamonds is estimated by the following formula:

P = 100- (K ₁ + K ₂ + K ₃ + K ₄ + K ₅ ),%,

where K ₁ - the share of destructible diamond during drilling,%;

K ₂ - the same with the explosion,%;

K ₃ - the same when loading and transporting,%;

K ₄ - the same with enrichment,%;

K ₅ - the same with jewelry production,%.

According to experimental data, approximate values of the indicators are established as follows:

K ₁ - 4%

K ₂ - 12%

To ₃ - 3% (2% during loading and 1% during transportation)

K ₄ - 18%

To ₅ - 5%, then:

P = 100- (4 + 12 + 3 + 18 + 5) = 58%

In our case, without the use of blasting, the output of jewelry diamonds is determined by the formula:

P = 100- (A ₁ + A ₂ + A ₃ + A ₄ ),%,

where A ₁ - the share of destructible diamonds when loosening a bulldozer;

A ₂ - during transportation;

And ₃ - during enrichment;

And ₄ - in jewelry production.

A ₁ accept 2%, then:

P = 100- (2 + 3 + 18 + 5) = 72%

Comparing the obtained results on the destructibility of diamond during the extraction of kimberlites by drilling and blasting technology and a dredger, we have that the yield of a large class of jewelry diamonds in the proposed method will increase to 14%.

3. The calculation of the performance of airlift

The initial data for calculating the performance of airlift are: geometric lift height N and pulp flow Q. In this case, the pipe diameters, nozzle immersion depth, air flow, pressure and compressor power are determined.

The diameters of the pipes are selected depending on the specified flow rate of the pulp. In this case, at Q = 75-120 l / s we take the pulp-lifting pipe D = 250 mm, the air-conducting pipe d = 88 mm, the casing D _obs = 450 mm.

To characterize the nozzle immersion depth, we introduce the so-called pipe immersion coefficient K equal to

K = N / N _to -H + h / H _g = 1 + h / H _g

The value of the coefficient K is selected depending on a given geometric lift height N _g . In turn, the value of the coefficient K determines the efficiency of the airlift η _airl :

When N _g = 30-60 m, K = 2.0-2.2

η _Earl = 0.5-0.54

Then determine:

N = K N _g = 2.0 * 50 = 100 m

Nozzle immersion depth h (below dynamic level)

h = H-H _g = (K-1) H _g = 50 m

The specific air flow q ₀ (per 1 m ³ pulp) is calculated by the formula obtained for isometric compression of air,

The total air flow rate W _to (m ³ / min) of the compressor is

W _k = a ₁ a ₂ q ₀ Q,

where Q is the specified flow rate of the pulp, m ³ / min,

a ₁ and a ₂ are coefficients that respectively take into account air temperature t and altitude ▽

at t ° C = 0 ° C

a ₁ = 1.06 a ₂ = 0.92 ▽ = 600 m

W _k = 1.06 * 0.92 * 5.58 * 120 = 653 m ³ / min

Starting pressure P _p (MPa) of the compressor at a static pulp level in the sump is

P _p = 0.01 (H + H _gg + h _Tr ^I ) = 0.01 (100 + 30 + 5) = 1.35 MPa,

where N _gst - the geometric distance from the ground level to the static level of the pulp, m;

h _Tr ^I - hydraulic pressure loss in the air tube, 2-5 MPa.

The operating pressure P _to (MPa) of the compressor is

P _k = 0.0098 (h + h _tr ^I ) = 0.098 (100-50 + 5) = 0.54 MPa

According to the values of the working pressure P _k and the total air flow rate W _k , the compressor and the engine recommended for it are selected from the catalogs.

When designing an airlift mixer, the diameters of the holes are taken to be 3-6 mm, and their number is assigned such that the total area of the holes is 1.5-2 times larger than the cross-sectional area of the air pipe.

The volume of the air receiver V _p (m ³ ) at an air flow rate W _k <30 m ³ / min is calculated by the formula

We accept a V300-2K brand compressor with a capacity of 224 kW and a cooling water flow of 13.0 m ³ / h.

4. Calculation of skip lift

a) The source data for the calculation

N = 330 m - the average depth of the quarry.

β = 30 ° - the angle of inclined trunks.

γ = 2.5 t / m ³ - volumetric weight of the rock.

f _to = 5 - coefficient of strength according to prof. M.M. Protodyakonov.

and _max = 100 cm - the maximum piece entering the well (adopted according to the technical capabilities of the bulldozer-ripper).

Q _cm = 200 t / cm - interchangeable productivity of an underwater bulldozer-ripper for feeding large pieces into the well.

and _avg = 40 cm - the average size of the piece entering the well.

ω = 0,008 - specific resistance to movement.

b) Technical calculation

1. Determine the hourly capacity of the skip hoist

,

,

where K _n - the coefficient of uneven receipt of the cargo (K _n = 1,1);

t _c.p. - the preparation time of the bulldozer-ripper for work 1 hour.

2. According to the scheme, we offer the average length of the rollback (figure 4).

a) skip dimensions:

Skip width B for the maximum piece a _max = 100 cm

B = 2.5 and _max = 2.5 m

For the convenience of loading, we take a skip in the form of a square box, then its length B = C its width. The height of the skip along the rear wall h _z = 1.6 m, along the front wall h _p = 1.0 m, taken at a bore angle of 30 °.

b) Determine the volume of skip V _c

c) Determine the capacity of the skip

σ _c = V _c * γ = 8.125 * 2.5 = 20.3 t≈20 t = 20,000 kg

d) Determine the own weight of the skip

Since the rocks are not strong, f = 5, and the loosening coefficient K _p = 1.6 is high due to the presence of lumpy rock mass, the density in the loosened state is γ _times ,

,

,

then we accept the welded construction of the skip in the form of a box on the undercarriage. Then the reduced mass q _{c of} one centimeter of skip:

Hence the mass of the skip M = q _c * B = 9.0 * 250 = 2250 kg.

Given the undercarriage, the weight of the skip is accepted in the calculation of M _s = 4500 kg.

4. Determination of flight time (s)

,

,

where V _1-2 - the average speed of the skip on an inclined section 1-2, take the characteristic winch 3 m / s

V _0-1 and V _2-3 - skip speed at loading and unloading points. Accepted 1 m / s.

t _pz = 150 s - the duration of the preparatory-final operations.

5. Determine the number of skips in work

,

,

where σ _s - 20,000 kg skip loading capacity.

6. Determination of the required strength of the skip hitch S _sc

S _sc = n (σ _c + M _c ) (ω * cosβ + sonβ) = 1.0 (200000 + 45000) (0.008 * 0.866 + 0.5) = 1.0 * 24.1 Kn = 24100 N

7. Selection of rope parameters.

The linear weight of the rope (N / m) is found by the greatest statistical effort when lifting the skip.

σ is the breaking strength of the wires 1400 MPa.

ρ ₀ is the specific gravity of the rope.

f ₁ - 0.15 coefficient of friction of the rope on the soil.

Choose a rope of type (TK) with parameters:

d _k = 35.5 mm; d _ol = 1.4 mm; ρ = 58.8 N / m according to GOST 3085-80.

8. Engine selection

Determine the traction force when lifting a loaded skip

F _g = (G + M _s ) (ωcosβ + sinβ) + ρh _cp (f ₁ cosβ + sinβ);

F _g = (200000 + 45000) (0.008 * 0.866 + 0.5) + 57.0 * 650 (0.15 * 0.866 + 0.5) -147437 N.

We determine the engine power

N _g = K _s * F _g * V / 1000η = 147437 * 3.0 / 1000 * 0.85 = 500 kW.

We accept an asynchronous motor type AK12-52-4 with a capacity of 630 kW and n = 1000 min ^-1 .

9. Choosing a winch.

The diameter of the drum D _b = 60 d _to = 60 * 35.5 = 2130 mm.

The design parameters N, S _h , V and D _b satisfy the winch 2 LGL.

5. Expected improvement of technical and economic indicators

A comparative assessment of the results of the calculation of technical and economic indicators in the development of kimberlite pipes in complex hydrogeological conditions is given in the table. As a basic (traditional) option adopted drilling and blasting method of mining.

Table
EXPECTED TECHNICAL AND ECONOMIC INDICATORS NN s / n The name of indicators Traditional technology Recommended Technology 1 Method for softening kimberlites in a quarry explosive blastless 2 Loading of kimberlite in the face excavator loosening 3 Quarry kimberlite crushing Bvr loosening 4 A method of transporting kimberlites to RP dump truck skip airlift 5 The degree of destruction of jewelry diamonds,% 42 28 including: - drilling 4 - - loosening by a bulldozer - 2 - imploding works 12 - - loading and transportation 3 3 - enrichment eighteen eighteen - jewelry production 5 5 6 The output of jewelry diamonds,% 58 72 7 The increase in the output of a large class of diamonds,% - 14

The recommended option, according to the calculations, provides an increase in the yield of a large class of jewelry diamonds by 14% compared to traditional technology.

Sources of information

1. Androsov A.D. Technology for the development of deep quarries in Yakutia. - Novosibirsk: “Science”, 1996 - p.198-201.

2. Mountain encyclopedia. - M.: “Soviet Encyclopedia”, 1991 - v.5. - p.118.

3. Nurok G.A. The process and technology of hydromechanization of open cast mining. - M .: Nedra, 1995 - p. 238-248.

4. Nurok G.A. The technology of mining from the bottom of lakes, seas and oceans. - M. Nedra, 1979. - p. 151-154.

5. Pesvianidze A.V. Calculation of underground mine installations. - M .: Nedra, 1992

6. Tikhonov N.V. Transport vehicles of mining enterprises. - M .: Nedra, 1985

Claims (1)

A method of developing kimberlite pipes in difficult hydrogeological conditions, including loosening rocks, turning it into pulp and transporting it through a pulp line with a dredger, characterized in that for resource conservation and increasing the yield of a large class of jewelry diamonds, a large borehole passes through the open pit aquifers from the bottom of the quarry to final depth of mining, construct an inclined shaft, which is connected at a given depth to the well, after which launch into the quarry space a sub-permafrost high-pressure brine is placed, an airlift dredger is placed on the surface of the pond, a bulldozer-ripper with a universal crown is lowered to the bottom of the pond, kimberlites pre-softened by brine are loosened using a bulldozer according to the spiraling cuts, the small fraction is transported through the ore-erodite transport , a caisson drift and an inclined shaft equipped with a skip hoist, are fed to the surface to the ore storage, and the mining of kimberlites the lower tubes below the bottom of the quarry are led at vertical angles of redemption of the sides without overburden work.

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