WO2014000069A2

WO2014000069A2 - Process of environmental recovery of inactive and exhausted mining areas, and use of mining and/or drilling residues in the environmental recovery of inactive and exhausted mining areas

Info

Publication number: WO2014000069A2
Application number: PCT/BR2013/000109
Authority: WO
Inventors: Júlio César SIMÕES PREZOTTI
Original assignee: Manancial Projetos E Consultoria Ambiental Ltda.
Priority date: 2012-06-26
Filing date: 2013-04-09
Publication date: 2014-01-03
Also published as: WO2014000069A3; BR102012019092B8; BR102012019092B1

Abstract

The present invention relates to a process of environmental recovery of inactive or exhausted mining areas, with the use of mining and/or drilling residues, which comprises the steps of: i) preparing the area or "cell" to be re- claimed, comprising: a) cleaning said cell, through the removal, containment or relocation of loose or unstable rocks; b) building drainage systems in said cell (including its surroundings); and c) sealing the surface of said cell; d) optionally, building an accumulation lake; ii) filling said cell with mining and/or drilling residues; and iii) enclosing said filled cell with a sealing layer. The present invention further comprises the use of mining and/or drilling residues in the- environmental" recovery of inactive or exhausted mining regions, by using said residues.

Description

"PROCESS OF ENVIRONMENTAL RECOVERY OF INACTIVE AND EXHAUSTED MINING AREAS, AND USE OF MINING AND/OR DRILLING RESIDUES IN THE ENVIRONMENTAL RECOVERY OF INACTIVE AND EXHAUSTED MINING AREAS."

[001] FIELD OF THE INVENTION

[002] The present invention relates to a process of environmental recovery of inactive or exhausted mining areas, with the use of mining and/or drilling residues, particularly to a process of industrial residues landfill for the morphological restoration of these areas near to their original condition, approaching the concept of rehabilitation applied to these areas. The present invention also relates to the use of mining and/or drilling residues in the environmental recovery of inactive or exhausted mining regions, particularly mining residues from ornamental rocks and drilling residues from onshore or land oil wells.

[003] BACKGROUND OF THE INVENTION

[004] The recovery process of inactive mining areas with the aid of mining residues, according to the invention, makes use of two types of residues: those arising from the processing of ornamental rocks and those from the exploration of onshore oil wells.

[005] The production process of ornamental rocks processing may be devel- oped in three stages: (A) Extraction of the natural rock in block form; (B) cutting or sawing the blocks into raw sheets; and (C) finishing, which consists in polishing and cutting the sheets in predetermined sizes, resulting in a finished product for marketing.

[006] During the entire process, there is a significant generation of residues, both in semisolid and solid state. According to studies, the losses in the process reach up to 30% of the blocks, mainly in the form of discarded abrasive slurry.

[007] Consider, therefore, the pollution potential of the abrasive and polishing slurry discarded from process may pose to the environment, especially to the soil and surface and ground waters of the nearby areas.

[008] Table 1 below presents a flow chart illustrating the production process and the residues generated in the processing of ornamental rocks. TABLE 1

[009] The process of block cutting or sawing may be described by considering two steps: rock washing and sawing. [010] The cutting process is initiated by washing the blocks from the ornamental rock extraction area to remove soil that adheres to the block during the extraction process and handling for transportation.

[011] After washing, the sawing of the blocks starts in the cutting machines, which process is accomplished with the aid of abrasives (metallic shot), lime for lubrication of the blades and preventing oxidation of the cut sheets, and water.

[012] The abrasive slurry, which is a mixture composed of the metallic iron and/or steel shot, lime and water, is produced in tanks and distributed by showers on the block and the moving cutting blades through pumping, with recirculation and periodic discharge of excess slurry, mainly due to the increase of its density by adding the material removed from blocks of rock.

[013] The discarded abrasive slurry - fluid slurry - is defined as a semisolid residue because it has such a moisture content that it enables its flow through pipes in a hydraulic regime. It is noteworthy that fluid slurry constitutes the main residue resulting from the processing of ornamental rocks, with regard to the amount generated.

[014] In the finishing process, the raw sheets (cut pieces) are polished and the polished sheets are cut in predetermined sizes, resulting in a finished product for marketing.

[015] At this stage of the processing of ornamental rocks, semisolid residues (fluid slurry) are also generated, containing rock material with fine granulometry and difficult sedimentation, but in lesser quantities as compared with the abrasive slurry discarded in the block cutting process.

[016] Other residues are also generated in the finishing process, such as plastic, metallic, and cardboard packaging, worn abrasive pads, among others, that will not be part of the proposed recovery of mining degraded areas.

[017] Despite the long period of exploration of ornamental rocks in the state of Espirito Santo and in Brazil, there are few publications in the literature on the environmental impacts caused by residues from the activities of this sector; see J.C.S. Prezotti, "Resultados de monitoramentos de estacoes de tratamento de efluentes liquidos de industrias de beneficiamento de marmore e granito, implantadas no Municipio de Cachoeiro de Itapemirim" ("Results from treatment plant monitoring of residueswater from the processing of marble and granite, installed in the city of Cachoeiro de Itapemirim") In: Seminario Estadual Sobre Saneamento e Meio Ambiente, 5, 5 Vitoria, ABES, 2003.

[018] With regard to research on the classification of the discarded abrasive slurry, in terms of potential risks to the environment and public health, some authors, such as Moura, W.A. et al. "Utilizacao do residuo de corte de marmore e granito em argamassas de revestimento e confeccao de lajotas0 para piso" ("Using the marble and granite cutting residues in facing mortar and in the manufacture of tiles for flooring") Sitientibus, Feira de Santana, n. 26, p. 5-6, Jan./Jun. 2002, available at: www.ufes.br/sitientibus/tecnologia_26>, obtained data that indicated that these ornamental rock processing residues belong to Class ll-A, Non-Inert,5 according to N BR 10004/2004.

• - [019] To "obtain the qualitative characterization of the fluid slurry, samples were taken in fluid slurry dehydrated by primary sedimentation processes from the cutting process of ornamental rocks.

[020] Samples were sent to laboratories accredited with the supervising envi-0 ronmental agency of the state of Espirito Santo, where heavy metals were analyzed in leachate extracts (NBR 10.005/2004) and in the solubilized extract (NBR 10.006/2004), and the pH of the collected samples was analyzed. The results obtained in laboratory tests indicate that the classification of dehydrated semisolid residues (dehydrated fluid slurry) is Class ll-A, Non-Inert.

[021] In these studies, permeability tests and compacting of dehydrated fluid slurry collected in the companies concerned were also carried out. The permeability of the sample at 20 °C resulted in 3.578 x 10-6 cm/s, with a molding humidity of 22.2%.

[022] The discarded abrasive slurry resulting from the process of granite or marble block cutting, after being subjected to the dehydration process which results in a moisture content below 30% represents the main residue, in qualitative and quantitative terms, of the processing of ornamental rocks. [023] The amount of abrasive slurry discarded in the process of block cutting, after dehydration, may be obtained by considering the sizes of the granite blocks in terms of average values, the operating characteristics of the cutting equipment and the inputs used in the cutting process, resulting in approxi- mately 14,007.86 kg/cut with final moisture content of 30%, according to the conducted field survey.

[024] In relation to the residues generated by oil exploration, onshore oil wells are opened by rotary equipment using fluids composed of water and mixtures of clays and additives, forming the drilling mud. Drilling mud is injected into the well and keeps the ideal pressure so that the walls of the well will not collapse. As drilling proceeds, all the ground material comes to the surface mixed with the slurry.

[025] The slurry discharged from drilling, in view of the need to use fluids, acquires concentrations of chemicals, often changing the inert characteristics of the drilled layers, thus requiring environmental management of the dis- posed mud, known as drill cuttings, as solid residues. ^{: " 1} ' ^*

[026] In this context, arises the need to have residues treatment technologies, aiming at preserving the environment.

[027] Studies carried out by the main generator of such residues in Brazil, in this case Petrobras, and confirmed by analyzes conducted by the present inventor, show characterizations that enable to classify them as belonging to Class ll-A, Non-Inert, according to NBR 10.004/2004.

[028] Aiming at the environmental characterization of the drilling residues from its onshore oil wells located in the north part of the state of Espirito San- to, Petrobras - Petroleo Brasileiro S.A. - developed a sampling plan considering the different phases of the drilling process, being formed by "n" sub- samples obtained in the intervals of variations that occurred in function of the geology of the area.

[029] The collection of "n" subsamples occurred during three different stages of well drilling, wherein five (5) subsamples were collected during the 1st phase, 20 (twenty) subsamples during the 2nd phase and 29 (twenty nine) subsamples during 3rd phase. [030] The results of physicochemical analyzes made it possible to characterize said residues as Class ll-A, Non-Inert, according to NBR 10.004/2004: Solid residues - Classification.

[031] The environmental characterization of such residues by collecting sev- en (7) subsamples in different buckets of trucks destined to the residues landfill installed in an inactive mining site to be subjected to this process showed the same Classification: Class ll-A, Non-Inert, according to NBR 10.004/2004: Solid residues - Classification.

[032] To estimate the amount of drill cuttings generated by an onshore oil well drilled by Petrobras towers located in northern Espirito Santo, the average currently received at the residues landfill subjected to this process was considered, at about 300 m3/month per tower drilling to a total depth of between 1 ,200 and 1 ,500 meters.

[033] The prior art contains several documents relating to the disposal of min- ing residues and the restoration of inactive mining areas.

" [034] Thus, an overview of the situation of the disposal of drill cutting'sis dis-^~ closed in an Internet article that can be found at: Drilling Residues Management Technology Descriptions, www.roughneckcity.com/.

[035] Various processes have been employed in the prior art for disposing drill cuttings from oil wells.

[036] In one process, the cuttings are stabilized, and then buried or spread over highways. To this end, the cuttings are mixed with an equal weight of an environmentally friendly product, such as fly ash or fluidized bed coal ash, with a low metal content. This operation doubles the original volume of cut- tings, which is then 1) buried or 2) spread over a large surface area on the ground in a thickness determined by rules, or 3) spread over a road, covered and compressed, or still 4) injected into a subsurface or void or 5) transported to a commercial facility.

[037] These stabilization procedures, although effective, have disadvantages, such as doubled volume, the cost of burying the increased volume, if this is the disposal option, the need for large areas for spreading the material, if this is the option, and so on, each option has disadvantages, especially as to the cost of covering a road surface, for example, or of injecting into a well or transporting to a disposal facility.

[038] U.S. Patent 4,942,929 describes a process for reclaiming and partially reusing drill cuttings from wells comprising separating construction-grade gravel from the drilling fluid and washing the gravel before storage or using the same as a construction material.

[039] U.S. Patent 4,611 ,951 describes a process for the recovery of excavated mine sites and otherwise useless lands with the use of sludge and residues obtained from ore processing.

[040] U.S. Patent 5,249,889 describes a process for preparing an aggregate mixture from by-products of residues to recover an area without the use of native soil or other material transported by trucks. The residues materials include lime sludge, coal ash, wood ash, chipped concrete residues and yard residues. The area is restored using ash or concrete residues in varying combination with the lime sludge. The pH characteristics and low permeabil- ity^'of lime sludge are used to prevent heavy metals and other potential pollutants in the ashes from leaching into the ground water. The yard residues material is then layered over the lime sludge/ash/concrete aggregate mixture to serve as a final cover and to support the growth of permanent vegetation. The recovered area is in compliance with the applicable environmental regulations and is completed without excavation or use of native or transported soils.

[041] U.S. Patent 5,237,945 describes a water barrier formed from a clay- fiber mat. It is a water-barrier based on fabric filled with a water-absorbent material such as granular bentonite clay. This article acts as a barrier.

[042] U.S. Patent 6,322,489 discloses a process for restoring wetlands by separating drill cuttings from drilling fluid, mixing the cuttings with a stabilization medium and then filling a desired position in the wetlands with the reconstituted material.

[043] U.S. Patent 6,381 ,899 describes a method for converting well drill cuttings containing petroleum hydrocarbon in an environmentally friendly humus-like product, wherein salt is washed therefrom, the washed cuttings mixed with a feedstock having carbon and nitrogen contents sufficient to initiate a biopile composting reaction, forming a product by continuing the biopile composting reaction until i) the biopile is reduced in weight and/or volume to a weight and/or volume that approaches the original weight and/or volume of the drill cuttings before the feedstock was added thereto, and ii) the total petroleum hydrocarbon content of the biopile is reduced to an environmentally friendly level for spreading on the earth's surface..

[044] The published patent application U.S. 2009/0238643 describes a method of using oil-contaminated drill cuttings from drilling operations primarily in gravel or dirt roads to provide dust suppression or as a component of the top course of a road. The drill cuttings are mixed with virgin aggregates, asphalt compounds and/or recycled hydrocarbons including recycled rubber from tires and recycled asphalt shingles for incorporation into a road bed to improve the structure of the road. If not used as proposed in this document, it is alleged that the cuttings would be disposed at a landfill.

-^;" - [045] The published patent application U.S: 2012/0000654 A1 relates to a composition for filling a mining borehole utilizing glass residues and fly ash. The composition is a cost-effective mixture of cement, fly ash, glass and water and may incorporate additional fine and coarse aggregates as well as chemical admixtures. The use of barrier pillars is reduced by using the filling composition.

[046] The state of the art still requires environmental recovering technologies for inactive or exhausted mining areas, in which mining and/or drilling residues are used, including residues from ornamental rock mining and onshore oil drilling, which are usually disposed of in the environment, resulting in great environmental damage.

[047] As described below, the present invention solves the above-mentioned technical problem, by providing a new and unexpected process and use, resulting in the remodeling of the landscape in morphological harmony with the surroundings, mitigating the visual impact generated by environmental degradation, restoring the original landscape of the mined site, geologically stabi- lizing the affected area, and disposing residues that had hitherto only a pollutant and useless nature.

[048] SUMMARY OF THE INVENTION

[049] The present invention relates to a process of environmental recovery of inactive or exhausted mining areas, with the use of mining and/or drilling residues, which comprises the steps of:

i) preparing the area or "cell" to be recovered, comprising: a) cleaning said cell, through the removal, containment or relocation of loose or unstable rocks;

b) building drainage systems in said cell (including its surroundings); and

c) sealing the surface of said cell;

d) optionally building an accumulation lake;

ii) filling said cell with mine and/or drilling residues;

iii) enclosing said filled cell with a sealing layer; and

iv) revegetating said enclosed cell:' ^{" ' * '}

[050] This process is assisted by units of administrative support.

[051] In a preferred embodiment of the invention, said process comprises the steps of:

a) cleaning said area for removal, containment or relocation of loose or unstable rock blocks that are still in the previously tilled area;

b) building drainage systems of rainwater precipitated onto (outside) said residues cell, directing said water directly to receiving water bodies;

c) sealing the entire surface area of the exhausted mining area;

d) building the control drainage system at the bottom of said cell, for detecting leaks of percolated liquids;

e) building the drainage system of percolated liquids - precipi- tated rainwater - inside said cell;

f) building an accumulation lake for percolated liquids drained from inside said cell with a view to further use in industrial processes, or re- lease into water bodies, provided that they have physical and chemical parameters in accordance with the standards for releases established by CONAMA Resolution no. 430, of May 13, 2011 ;

g) building of units for administrative support (e.g. visitation and implementation of environmental controls, residues weighing scale, security gatehouse, etc.);

h) topographic remodeling ensuring the stability of the pile, said cell being filled with residues, and sloping for morphological restoration; i) final enclosure of the cell with a sealing layer;

j) revegetating on the sealing layer; and

k) removing the units for administrative support after revegeta- tion of the enclosed cell, restoring the site to its original condition.

[052] The present invention further relates to the use of mining and/or drilling residues in the environmental recovery of inactive or exhausted mining re- gions, by using said residues.

[053] The mining residues employed in the present invention may be residues from mining of ornamental rocks and the drilling residues may be residues from onshore or land oil wells, which are classified as belonging to Class ll-A and Class ll-B, according to NBR 10.004/2007.

[054] The inactive or exhausted mining regions to be recovered according to the invention correspond to mines, quarries, fields, hills, mountains, slopes, land depressions, among others.

[055] Hence, the present invention provides a process and an use for the recovery of inactive or exhausted mining areas, with the use of mining and/or drilling residues to be enclosed in a residues cell that restores the inactive/exhausted mining area to its original aspect.

[056] The present invention further provides a process and an use for the recovery of inactive or exhausted mining areas, which enables said recovered area to work as an industrial residues landfill.

[057] BRIEF DESCRIPTION OF THE DRAWINGS

[058] FIGURE 1 is a schematic view of the dual-sealing system at the bottom of the cell, employing the geocomposite blanket (10). [059] FIGURE 2 is a schematic view of the dual-sealing system at the bottom of the cell, employing the geotextile blanket (11).

[060] FIGURE 3 is a schematic view of the installation of surface water flow channels and the lateral sealing of the cell walls.

[061] FIGURE 4 is a schematic view of the drainage beds intermediate to the layers of residues and surface water flow channels.

[062] FIGURE 5 is a schematic view of the network of perforated collector pipes and the monitoring box.

[063] FIGURE 6 is a schematic view of the control drainage system in a her- ringbone pattern to be installed at the bottom of the cell.

[064] FIGURE 7 is a schematic view of the cell enclosure installed in a buried trench.

[065] FIGURE 8 enclosed is a schematic view of the cell enclosure installed in a non-buried trench, without a structural layer.

[066] FIGURE 9 enclosed is a schematic view of the cell enclosure installed in a non-buried trench, with a~structufal layer. - "^~

[067] DETAILED DESCRIPTION OF THE INVENTION

[068] The various steps of the process and the use of the present invention will be described in detail below with reference to the enclosed drawings.

[069] According to the present invention, the term "cell" means final disposal site for the residues, properly constructed with the civil works necessary to carry out the environmental controls established by the relevant legislation, in accordance with the features of the residues to be disposed of therein.

[070] Throughout the present specification and in the drawings, the residues cell is generally indicated by number (100).

[071] a) Cleaning the area for removal or containment of unstable rock blocks:

[072] The geotechnical procedure and the removal of loose or unstable blocks in tilled areas, the initial stage of the environmental recovery process of the invention, consists of removing boulders or rock blocks, or other minerals, usually irregular, with the risk of free fall or sliding. The removal is done with the aid of mechanical or manual conventional means of the art. [073] The removed materials may be relocated and may remain within the area to be recovered, being covered with the sealing system to be installed at a later stage, or they may be exploited commercially.

[074] b) Building drainage systems of rainwater precipitated onto (out- side) said cell, directing said water directly to receiving water bodies:

[075] Usually, in industrial residues cells, the rainwater precipitated on these residues undergoes contamination and thus cannot be disposed of in the environment without preliminary treatment.

[076] The rainwater precipitated around said residues cell and that is not in contact with it may be directed straight to the local receiving water bodies.

[077] Thus, the entire perimeter of the industrial residues cell to be installed in the area previously degraded by mining shall be provided with rainwater drainage systems, which will be designed and sized according to the contribution basin to be drained in order to prevent the flow of ground water to the interior of the cell.

[078] In case it is impossible to build these systems, in calculating the volume of percolated liquids within the cell, the total area resulting from the sum of the residues cell area and its surrounding area whose declivity will contribute with rainwater should be considered.

[079] c) Sealing the surfaces of the exhausted mining area:

[080] Inside the cell:

[081] According to Figure 1 , one embodiment of the invention contemplates at the bottom of the cell (100) a dual-sealing system, consisting of a high- density polyethylene blanket (12), which approximately 1.0 mm to approxi- mately 2.0 mm thick, particularly 1.5 mm thick.

[082] There are two options for the protection of the high-density polyethylene blanket (12). In one alternative, a geocomposite blanket (10) is used. Alternatively, a geotextile blanket (11) is used, as detailed later in the present application.

[083] Figure 1 illustrates the blanket (10), and Figure 2 illustrates the blanket (11). [084] The blanket (12) is seated on a layer of compacted clay (18). In said layer of compacted clay (18), inserted into grooves dug into its surface in places previously detailed, a control drainage system is built in a herringbone pattern for leak detection of percolated liquids that should not pass through the sealing layers. This system can be found in Figure 5.

[085] The system consists of using a perforated collector pipe (16) wrapped in a non-woven geotextile blanket (11) seated within a sand layer (17).

[086] The geocomposite blanket (10) is described later in the present application.

[087] For mechanical protection of the high-density polyethylene blanket (12), a layer (15) of dehydrated abrasive slurry is implanted thereon, thus not allowing the passage of tractors or other vehicles and equipment that damage the high-density polyethylene blanket (12). On this abrasive slurry layer (15) a drainage bed (14) wrapped in a non-woven geotextile blanket (11) must be implemented aiming at the subsurface drainage of percolated liquids through the residues layer (tS sfrranged thereon. ^{~ ~}

[088] Figure 1 illustrates the various components of the dual-sealing system at the bottom of the cell (100).

[089] In order to compose the several layers illustrated in the dual-sealing system at the bottom of the cell (100) of Figure 1 , number (20) represents a layer of the existing mineral after exploration. On the same is placed a layer (19) of grit or other existing minerals, whose physical characteristics are similar to those of said grits, particularly grits no. 03 and 04, which will serve as a draining layer. Said layer (19) contains a perforated collector pipe (16) wrapped by a non-woven geotextile blanket (11), to transport the liquids drained by the side walls of the cell (100), and that had no contact with the residues, to the outside of the cell (100). Then, a layer of compacted clay (18) is added, on which a layer of sand (17) is placed having inside a perforated collector pipe (16) surrounded by a non-woven geotextile blanket (11). Then, the high-density polyethylene blanket (12) is installed, and thereon an abrasive slurry layer (15) dehydrated for mechanical protection of the blanket (12). A draining bed (14) wrapped by a non-woven geotextile blanket (11) separates the blanket (12) from the first layer of residues (13) being used to fill the cell (100).

[090] According to the invention, the term "mechanical protection" means protecting the high-density polyethylene blanket (12) from direct friction from the wheels of tractors and other equipment that could damage it.

[091] The term "layer of residues (13)" means a layer composed of mining residues from ornamental rocks, as detailed in Table 1 above, disposed along with the drilling residues from onshore oil wells in random proportions, i.e. without set percentages, with a thickness that depends on the results of geotechnical studies to be performed for each particular case.

[092] The term "drainage bed (14)" means a layer of from about 30.0 cm to about 50.0 cm thick, particularly 30.0 cm thick, composed of grit or other types of existing minerals, whose physical characteristics are similar to those of said grits, particularly grits or other similar minerals with granulometry be- tween about 25.0 mm and about 100.0 mm.

[093] The' eri rr-^' ehydra ed^'"a rasive-s1urry layer (15)" means a layer Of fesi-^*"^*"'™ """^e&" dues composed only of abrasive slurry dehydrated with about 30.0 cm to about 40.0 cm thick, particularly 30.0 cm thick.

[094] The term "sand layer (17)" means a layer from about 30.0 cm to about

40.0 cm thick, particularly 30.0 cm thick, composed of sand, having inside a perforated collector pipe (16) wrapped by a non-woven geotextile blanket

(11), to collect any liquids that pass through the high-density polyethylene blanket up to a monitoring box (24) located externally to the cell (100).

[095] The term "perforated collector pipe (16)" means a PVC pipe having a diameter between 65 and 230 mm with a perforated area of 80 to 240 cm²/meter for the drainage of liquids.

[096] The term "layer of compacted clay (18)" means a layer composed of clay having approximately 0.80 m to 1.00 m thick, particularly 1.0 m thick, compacted with a permeability coefficient above K≤ 1 x 0-6 cm/s.

[097] The term "layer (19) of grit" means a layer of grit or other existing minerals, whose physical characteristics are similar to those of said grits, particularly grits no. 03 and 04, said layer being from about 30.0 cm to about 40.0 cm thick, particularly 30.0 cm thick. A perforated collector pipe (16) is placed inside it, wrapped by a non-woven geotextile blanket (11), in order to drain liquids percolating through the geocomposite blanket (10) implanted under the high-density polyethylene blanket (12) installed on the side walls of the cell (100).

[098] The term "mineral (20) still existing after exploration" means the remainder of the mineral in the previously explored deposit, on which the cell (100) is implanted, endowed with all the works and devices for achieving the necessary environmental controls.

[099] Sides of the cell:

[100] On the sides of the cell (100), a high-density polyethylene blanket (12) is implanted, preventing in this way the layers of residues (13) to be disposed inside the same from coming into direct contact with the mineral (20) still existing after exploration. This prevents the percolated liquids inside the layers of residues (13) from permeating any cracks generated in explosive disman- tling processes' o the layer (20)ro^~f the mineral still existing after exploration:^™ [101] Aiming at the mechanical protection of the high-density polyethylene blanket (12) against the effects of punching the edges of the mineral (20) still existing after exploration, one or more among the two different options de- tailed below may be adopted.

[102] Option 1 :

[103] In case the vertical or inclined walls in the area to be recovered have heights greater than the maximum installation height of the high-density polyethylene blanket (12), the above-mentioned geocomposite blanket (10) is installed thereunder, the functions of which are to provide mechanical protection and still allow drainage of rainwater precipitated onto the vertical walls above the maximum height of the high-density polyethylene blanket (12), thereby avoiding the presence of that accumulated water that could compromise the satisfactory stability of the residues mass, relieving pressure and preventing the formation of hydrostatic thrust.

[104] The geocomposite blanket (10) should have the following characteristics: [105] - be lightweight and flexible for drainage purposes, have a draining core comprising a three-dimensional geoblanket with 10 or 18 mm thick;

[106] - be composed by a drainage system with three basic elements: the draining element, which captures and conducts infiltration/percolation water; the filtering element, which prevents the loading of particles into the draining element, which would cause clogging and the consequent loss of flow; and the collecting element, which conducts the drain water to discharge;

[107] - be able to maintain a high flow capacity, even when installed at great depths under the effect of compression of the high-density polyethylene blanket (12);

[108] - if installed in a vertical position, to relieve the hydrostatic thrust, providing better stability conditions and improving the performance of the sealing systems, avoiding undesirable leakage;

[109] - if installed in a horizontal position, to provide efficient drainage of ex- cess water accumulated by relieving pore pressures and ensuring the integri-

- ty of the work. ' — - · ^{.. .. . ..}..^..

[1 10] Figure 3 illustrates the application of geocomposite blanket (10) in the mechanical protection of the high-density polyethylene blanket (12) and the drainage of rainwater that will flow through the vertical walls of the cell (100).

[1 1 1] Figure 3 further illustrates various components of the installation of surface water runoff channels (21) and of the lateral sealing of the walls of the cell (100).

[112] Option 2:

[1 13] In case there are no vertical or inclined walls in the area to be recov- ered that have heights greater than the maximum installation height of the high-density polyethylene blanket (12), the above-mentioned non-woven geo- textile blanket (11) will be installed thereunder, only to provide mechanical protection, with the sole function of protecting it against the effects of punching the edges of the mineral (20) still existing after exploration.

[1 14] Figure 2 illustrates the various components of the dual-sealing system at the bottom of the cell (100), by using the geotextile blanket (11).

[115] Top of the cell (100): [ 16] For sealing the top of the cell (100), that is, when residues disposal within the same ends, sealing follows the methodology to be established for each particular case for vegetation and morphological recovery of the site, to be determined by observing the needs to adapt the area in question to the 5 overall context of the existing landscape around it.

[1 17] The different forms of sealing the top of the cell (100) when it is closed are described in detail in the present application.

[1 18] d) Building the drainage system of percolated liquids - rainwater precipitated from inside the cell (100):

0 [1 19] According to the invention, the proper final disposal of surface water that are in contact with the residues inside the cell (100) and are thereby contaminated generating percolated liquids is the reuse in ornamental rocks processing companies, which use large quantities of water for the activities of cutting and polishing, and even the drilling towers of onshore oil wells, which 5 feature intensive use of water.

i"'^"-'--^',-[-t26]-With-^,a^'vtew-fo^'ve^"rtically---draining the rainwater which precipitates ^'6 nto' the residues and thus form percolated liquids inside the residues mass, preventing the formation of water columns that produce pressure and hydrostatic thrusts, and also to enable the drainage of water present in the residues0 moisture, a drainage system is provided, which comprises drainage beds (14) positioned between the various layers of residues (13).

[121] The beds (14) with a thickness of 30.0 cm are formed by draining material and a non-woven geotextile blanket (11).

[122] The draining material, of high granulometry, in the range of 25 to 1005 mm, is generated by grinding the midden of the granite blocks not used in the process of ornamental rock cutting.

[123] Figures 1 , 2, 3 and 4 show the details of these drainage beds (14) of percolated liquids inside the residues mass (13).

[124] For surface drainage of rainwater precipitated onto the residues mass0 within the cell (100) surface water runoff channels (21) are provided, said channels being of trapezoidal shape, coated with high-density polyethylene blanket (12) installed on the outer side of each layer of residues (Figure 4). [125] The percolated liquids generated within the residues mass and drained by drainage beds (14) are directed to surface water runoff channels (21). The channels (21) also collect the rainwater precipitated onto the residues mass, and send it to the water falls (23) which are surface water runoff channels (21) built vertically from excavation on the slope outside the residues mass.

[ 26] From these water falls (23), the water will be directed to an accumulation lake (24), from where, as needed, water trucks (not shown in the drawings) capture and transport it for reuse in the industrial processing of ornamental rocks and drilling of oil wells (Figure 6).

[127] For sizing calculations for both runoff channels (21) and for the water falls (23), the areas of rainfall to be drained and the intensity of the highest rainfall historically measured for the site of interest are taken into consideration.

[128] The description of the slopes (22) is also provided in the present appli- cation.

[129] Figure 4 illustrates the various constituents of drainage beds (14) intermediate to the layers of residues (13) and surface water runoff channels (21).

[130] Figure 5 illustrates the monitoring box (25) and the network of perforat- ed collector pipes (16).

[131] e) Building control drainage system at the bottom of the cell (100):

[132] For environmental safety reasons, the present invention provides for the installation at the bottom of the cell (100) of a leak detection system of percolated liquids, called control drainage system in the form of a herring- bone pattern, for leak detection of percolated liquids.

[133] This system will consist of a network of perforated collector pipes (16) of nominal diameter comprised between 65 and 230 mm with an open perforated area of 80-240 cm²/m connected in the form of a herringbone pattern (Figures 1 , 2 and 6), seated within a sand layer (17), which in turn will sup- port the high-density polyethylene blanket (12). [134] The perforated collector pipes (16) are seated and enclosed in a non- woven geotextile blanket (11), and connected to a monitoring box (25) positioned outside the cell ( 00).

[135] According to the invention, the term "monitoring box (25)" means a box built in concrete, with sealed bottom in the dimensions of 50 x 50 cm and variable height, provided only with an inlet pipe, whose sole purpose is to enable the implementation of environmental controls, verifying the existence of any leaks of liquids that could have gone through the high-density polyethylene blanket (12).

[136] Figure 6 illustrates the various components of the control drainage system in the form of herringbone pattern to be implanted at the bottom of the cell (100), namely surface water runoff channels (21), water falls (23) and accumulation lake (24).

[137] f) Building an accumulation lake (24) of percolated liquids and sur- face rainwater for further use in industrial processes:

^{" '} [138] The size of the accumulation lake (24) should bexalculated cohsidgring' - the time series of average monthly rainfall intensity occurring at the recovery site of the area degraded by mining.

[139] With the result of the volume of water to be accumulated obtained by multiplying the historically measured average monthly intensity by the contribution area, the water loss by evaporation to the site should also be considered and decreased.

[140] Periodic removal of accumulated percolated liquids for reuse in the cited industrial processes is provided.

[141] g) Building of units for administrative support:

[142] In places degraded as a result of mining activities and later recovered by the application of the present invention, support units are provided (not shown in the drawings), to operate as industrial residues landfills duly licensed by the supervising environmental agencies.

[143] Equally provided is the installation of a highway scale (not shown) in order to measure the exact amount of residues that will be disposed of in the cell (100) of the residues landfill, and also for the subsequent issuance of final disposal slips and service invoices for the residue-generating companies, thus facilitating the monitoring work of environmental agencies.

[144] The condition for the area to be recovered to work as an industrial residues landfill is the provision of an easy-to-access highway system, limited by 5 a control gate, preventing the improper entry of trucks with unknown residues and people.

[145] Additionally provided is the inner area to maneuver the residues transportation vehicles (not shown in the drawings), which should have access to the points of entry of residues into the cell.

10 [146] h) Topographic remodeling ensuring the stability of the residues mass, with the filling of the cell with residues, and sloping for morphological restoration:

[147] Stability of the residues mass:

[148] The Occupation Plan of the cell (100) indicating the sequence of the 15 layers of residues (13) to be filled is a function of previous studies carried out c ^{; ! *} ith the^' ypes of residues to be disposed^' therein; in order to ensure the stability of the residues mass.

[149] In the case of degraded areas to be recovered, whose cells (100) occur completely buried in the ground, that is, when there are no heights at the res- 20 idues mass that threaten its stability, previous studies for proof of stability may be dismissed.

[150] However, in most cases, the areas to be restored have sides taller than others, resulting in situations in which the residues mass does not have structural support on one side thereof, and therefore must have its own struc- 25 tural stability.

[ 51] Filling the cell (100) with residues (13):

[152] The residues (13) transportation vehicles (not shown in the drawings) are registered when they enter the landfill, then informing their origin and classification, necessarily Class ll-A and ll-B, according to the NBR 30 10.004/2007, transported volume and/or weight, and the moisture content of said residues. [153] The vehicles are then forwarded to the scale (not shown in the drawings) for weighing, and then directed to the dumping points (not shown in the drawings) into the cell (100).

[154] It is preferred that the procedure proposed in this invention for dumping, i.e. the unloading of the residues (13), occurs during drought periods and in situations that do not endanger the safety of operators, within the cell (100) or on ramps built at heights above the final level of the residues mass (not shown in the drawings), which should be provided with due safety devices for proper operation.

[155] Thus, the residues (13) are dumped directly from the trucks into the cell (100) and spread and compacted, respecting the drainage beds (14) between layers of residues, and also the surface rainwater runoff channels (21).

[156] Regarding the Occupation Plan of the cell (100) that will establish the number of layers to be filled and the lifetime of the cell (100), i.e. the time allotted for their entire filling, it is defined according to the results obtained intfte^'studres^rrred out to ensure the stability o the residues mass, thus es-^~ tablishing the number of layers with their heights, and the quantities commercially provided for receiving residues from the residue-generating companies.

[157] Sloping for morphological restoration:

[158] According to the present invention, the topographic remodeling obtained for the area previously degraded by mining will comprise sloping, i.e. performing simple earthworks (moving residues with cuts and landfills), seeking to redraw the original topography of the mined area through inclined slopes (22) with the heights defined by the layers of residues (13), and with the construction of horizontal plateaus (31) between these layers to ensure that the machines have the mobility to carry out the activities.

[159] This procedure is intended to redesign the landscape in morphological harmony with the surrounding environment, in order to mitigate the visual impact, restore the original form of the mining site and stabilize the terrain making use of the landfill residues.

[160] In the restoration proposed by the invention, after the end of the industrial landfill activities, topographic remodeling assists biological recovery. Na- tive (endemic), rare and endangered species of the region are part of this process.

[161] According to the invention, the term "inclined slope (22)" relates to the outer part of each layer of residues (13), i.e. parts that are not near the walls of the cell (100) or confined between the various layers of residues (13), said slope (22) being constructed with angle and height defined in terms of ge- otechnical studies to be performed to ensure the stability of the residues mass.

[162] i) Final enclosure of the cell (100), when finished:

[163] After the closure of a residues cell (100) in licensed industrial landfills, its final enclosure is required using a sealing top layer, whose main function is to prevent contact from the rainwater with the residues disposed of therein, thus avoiding the generation of percolated liquids that must be treated before being released into the environment, therefore eliminating operating costs.

[164] In the case of a cell (100) installed in a buried area:

[165] Figure 7, which is a schernatic view όΐ a cell (100) enclosure^" installed in a buried trench, shows details of filling with residues (13) in a mined area excavated below ground level, i.e. when there are no vertical sidewalls or slopes resulting in heights higher than the maximum installation heights of the high-density polyethylene blanket (12).

[166] As shown in the schematic representation of Figure 7, the protection of residues (13) therein disposed, i.e. the enclosure of the cell (100) will occur with the installation of a layer of compacted clay (18) on the last layer of residues ( 13) and a drainage bed (14) over the same.

[167] The drainage bed (14) allows the flow of rainwater that infiltrates a layer (26) of topsoil placed on it, enabling the vegetation growth (27) proposed for the site.

[168] The thickness of the layer (26) of topsoil is a function of the revegeta- tion project proposed for the site.

[169] In the case of a cell (100) installed in a non-buried area resulting in vertical or inclined sidewalls: [170] In this case, the vertical or inclined sidewalls formed by layers of residues (13) include two different alternatives for the construction of the sealing layer (18) which is responsible for the cell enclosure (100).

[171] The first alternative is to construct a sealing layer (18) without a struc- tural function, that is, this layer will not have the function of assisting in the stability of the residues mass, but only isolating it from rainwater which will precipitate on them.

[172] Figure 8 is a schematic view of the enclosure of the cell (100) installed in a non-buried trench without a structural layer.

[173] The enclosure is constructed using a layer of compacted clay (18) on the layer of residues (13), with a drainage bed (14) leaning on it, which will serve to drain the rainwater that will precipitate onto the layer (26 ) of topsoil used for vegetation growth (27) that will be part of the reclaimed vegetation of the degraded area.

[174] The second alternative is to build a sealing and structural layer (28), -which, in this case, in addition to ensuring no ^"contamination of the rainwater which precipitate onto the site, should also have the function of contributing to the final stabilization of the inclined slopes (22) of residues.

[175] For this, we propose the use of techniques already applied globally, to be determined from geotechnical testing of the residues mass as it is being filled.

[176] The present invention proposes that as each inclined slope (22) is finished during the filling of the cell (100) with residues (13), the sealing and structural layer (28) of said slope is installed, as shown in Figure 8, whose function will be of great importance for the final goal which is the expected stability of the entire residues mass.

[177] The techniques already applied globally useful for the present process are the Anchored Walls technique and the Soil Nailing technique.

[178] According to the invention, the term "sealing and structural layer" (28) refers to the civil construction structure installed on the outside of the inclined slope (22), which will result in an outer surface of reinforced concrete in which the techniques of anchored walls or soil nailing may be used, the func- tions of which are to seal layers of residues (13) from the action of rainwater that precipitate on them, and also to contribute to the stability of the residues mass.

[179] Figure 9 shows a schematic view of the enclosure of the cell (100) that is not buried and has a sealing and structural layer (28).

[180] j) Revegetation over the sealing layer:

[181] In the case of a cell (100) installed in a buried trench:

[182] Generally, the revegetation technique by natural succession regeneration, in which the degraded area is isolated and only the soil is transferred so that the surrounding vegetation can grow towards it and encompass it once again, it is widely used and has shown good final results in the revegetation of degraded areas.

[183] In the case of a cell (100) installed in a buried area that does not result in a topography with high declivities after closure, the revegetation technique by natural succession regeneration will meet the needs of the sites

[184] In the case df a cell (100) installed in a nonf-buried trench which^* results in inclined slopes (22):

[185] For very steep and high walls, which is the case in most areas degraded by mining, the vegetation is unable to settle naturally. In the present re- covery process, the topographic remodeling to be achieved will assist biological recovery.

[186] When residues is no longer dumped in the cell (100) and the works for installing the sealing and structural layer (28) of the inclined slopes (22) are completed resulting in reinforced concrete surfaces, the soil nailing technique of organic blankets (29) is proposed on this layer, for planting species of primary vegetation for the formation of vegetation islands (30) (Figure 9).

[187] This nailing must be performed in a spaced manner, i.e. it should not necessarily cover the whole surface of the resultant reinforced concrete on the layers of residues (13), and it will be defined in terms of what is intended to recover in terms of vegetation in each particular case.

[188] According to the present invention, the term "organic blankets (29) for planting" refers to blankets made of plant residues, including coconut fiber and the like, which will serve to fix the primary vegetation to be sown, and which will decompose over time, leaving only the vegetation that has developed and taken root directly in the sealing and structural layer (28).

[189] The term "vegetation islands (30)" corresponds to the sites positioned on the sealing and structural layer (28) of the inclined slopes (22) of residues (13) where organic blankets were fixed (29) for planting in order to make possible the development of vegetation.

[190] Due to the little amount of substrate initially existing in organic blankets (29) for planting installed for the development of primary vegetation, the lat- ter, when it dies, will initiate the process of biological recovery with the formation of minimal substrate for the natural development of other endemic, rare and endangered species present in the local flora in a accelerated and monitored way.

[191] k) Removal of civil works (not shown in the drawings):

[192] The final object of the invention for the recovery of areas degraded by mining is the-morphol0gicar¾

[193] Thus, when residues is no longer received, when the cell (100) is enclosed and after vegetation restoration, it is critical to remove the civil works implemented (not shown) at the site for the normal functioning of industrial residues landfill.

[194] Such removal shall be duly informed to the supervising environmental agency, confirming the final destination suitable for the different types of civil construction residues generated.

Claims

1. A process for environmental recovery of inactive or exhausted mining regions, by using mining and/or drilling residues, characterized by comprising the steps of:

b) building drainage systems in said cell (including its surroundings); and

c) sealing the surface of said cell;

d) optionally, building an accumulation lake;

ii) filling said cell with mining and/or drilling residues; and iii) enclosing said filled cell with a sealing layer.

2. The process according to claim 1 , characterized by comprising the further step of iv) revegetating said enclosed cell.

3. The- process according to claim 1 ότ -2, ^"Characterized in that, in step ii); said mining residues are residues resulting from the mining of ornamental rocks and said drilling residues is residues resulting from onshore oil wells.

4. The process according to claim 3, characterized in that said residues are classified as belonging to Class ll-A and Class-ll-B, as per NBR 10.004/2007.

5. The process according to any one of claims 1 to 4, characterized in that said process is assisted by administrative support units.

6. The process according to any one of claims 1 to 5, characterized in that said inactive or exhausted mining regions are selected from the group con- sisting of mines, quarries, fields, hills, mountains, slopes and land depressions.

7. The process according to claim , characterized in that it further comprises the steps of:

a) cleaning said mining area for removal, containment or reloca- tion of loose or unstable rock blocks that are still in the previously tilled area; b) building drainage systems of rainwater precipitated onto said residues cell (100), directing said water directly to receiving water bodies; c) sealing the surface area of the inactive mining area;

d) building the control drainage system at the bottom of the cell (100), for detecting leaks of percolated liquids;

e) building the drainage system (104) of percolated liquids - precipitated rainwater - inside the cell;

f) building an accumulation lake (24) for percolated liquids drained from inside the cell (100) with a view to reuse them in industrial processes, alternatively release into water bodies;

g) building of units for administrative support;

h) topographic remodeling ensuring the stability of the pile, said cell (100) being filled with residues (13), and sloping (22) for morphological restoration;

i) final enclosure of the cell with a sealing layer (28);

j) revegetation with vegetation islands (30) on the sealing layer (28); and

^~ k)^{^} - ""removing -the units fbr^'ad mi histrative support, restoring ^"the site to its original condition.

8. The process according to claim 7, characterized in that in step a) the unstable blocks removed remain in place, alternatively being removed for com- mercial use.

9. The process according to claim 7, characterized in that the residues (13) are classified as belonging to Class ll-A and Class-ll-B, as per NBR 10.004/2007.

10. The process according to claim 7, characterized in that the residues (13) comprise mining residues from ornamental rocks and drilling residues from onshore oil wells.

1 1. The process according to claim 7, characterized in that the sealing of the bottom of the cell (100) comprises in step c) placing a drainage layer (19) of grit in successive layers from the mineral (20) remaining from the exploration, provided with a perforated collector pipe (16) wrapped by a non-woven geo- textile blanket (11), a layer of compacted clay (18), a layer of sand (17), the inside of which having a perforated collector pipe (16) wrapped by a non- woven geotextile blanket (11), followed by a blanket (12) and thereon a layer (15) of about 30.0 cm to about 40.0 cm thick of abrasive slurry dehydrated for mechanical protection of the blanket (12) and a drainage bed (14) of about 30.0 cm to about 50.0 cm thick wrapped in a non-woven geotextile blanket 5 (11) separating said blanket (12) from the first layer of residues (13) to be used to fill the cell (100).

12. The process according to claim 1 1 , characterized in that the perforated collector pipe (16) comprises a PVC pipe having a diameter between 65 and 230 mm with a perforated area of 80 to 240 cm²/meter for the drainage of0 liquids.

13. The process according to claim 1 1 , characterized in that the layer of compacted clay (18) comprises a layer composed of clay approximately 0.80 m to 1.00 m thick, particularly 1.0 m thick, compacted with a permeability coefficient above K < 1 x 10-6 cm/s.

5 14. The process according to claim 7, characterized in that the sides of the

- - cell (100) being protected by a btanket (†2) to prevent direct contact of the" layers of residues (13) with the mineral (20).

15. The process according to claim 14, characterized by installing under said blanket (12) a geocomposite blanket (10) if the vertical walls of the area to be0 reclaimed have a height greater than the maximum installation height of said blanket (12).

16. The process according to claim 14, characterized by installing under said blanket (12) a non-woven geotextile blanket (11) if the vertical or inclined walls of the area to be reclaimed with a height greater than the maximum5 installation height of said blanket (12) are absent.

17. The process according to claim 7, characterized in that in step d) the rainwater that precipitate on the residues (13) is drained with the aid of drainage beds (14) with a thickness of about 30.0 cm to about 50.0 cm and composed of i) draining materials with a particle size between 25 and 100 mm0 resulting from grinding of midden of granite blocks from the exploration, and ii) a non-woven geotextile blanket (11) , said beds (14) being positioned between the various layers of residues (13) to be deposited in the cell (100).

18. The process according to claim 17, characterized in that the percolated liquids drained by the beds (14) are directed to surface water runoff channels (21) of trapezoidal shape installed on the outer side of each layer of residues (13) and coated with the blanket (12).

19. The process according to claim 18, characterized in that the channels

(21) additionally collect and send the rainwater to water falls (23).

20. The process according to claim 19, characterized in that from said water falls (23) the rainwater is directed to an accumulation lake (24) for collection and industrial reuse.

21. The process according to claim 7, characterized in that in step e) the control drainage system (104) for detecting leaks of percolated liquids comprises a network of perforated collector pipes (16) of nominal diameter comprised between 65 and 230 mm with an open perforated area of 80-240 cm m connected in the form of a herringbone pattern, seated within a sand layer (17), which supports the blanket (12), said pipes (16) being wrapped by the blan- - ket^;(11). · - --^^· · - ^· · ^..

22. The process according to claim 21 , characterized in that said perforated collector pipes (16) are connected to a monitoring box (25) built in concrete with a sealed bottom of 50 x 50 cm and variable height, equipped with only an inlet pipe for performing environmental controls, said box (25) being positioned externally to said cell (100).

23. The process according to claim 7, characterized in that in step h) the unloading of residues (13) occurs within the cell itself (100) and alternatively on ramps built in heights above the final level of the residues mass (13), said residues being spread and compacted respecting the drainage beds (14) between the layers of residues and the runoff channels (21).

24. The process according to claim 7, characterized in that additionally in step h) the stability of the residues mass (13) is ensured by inclined slopes

(22) .

25. The process according to claim 7, characterized in that step i) of enclosure of the cell implanted in a buried trench comprises a layer of compacted clay (18) on the last layer of residues (13) and over the same a drainage bed (14) for draining infiltrated rain through a layer (26) of topsoil.

26. The process according to claim 25, characterized in that the topsoil (26) is used for vegetation growth (27).

27. The process according to claim 7, characterized in that alternatively the cell closure (100) comprises a sealing and structural layer.

28. The process according to claim 27, characterized in that the sealing and structural layer (28) comprises a civil construction structure implanted on the outer part of the inclined slope (22) resulting in an outer surface of reinforced concrete.

29. The process according to claim 28, characterized by additionally fixing on said sealing and structural layer (28) organic blankets (29) for planting species of primary vegetation, including those made with plant residues for the formation of vegetation islands (30).

30. An use of mining and/or drilling residues, characterized in that it is for the environmental recovery of inactive or exhausted mining regions, by using said residues.

31. The use according to claim 30, characterized in that said mining residues is residues resulting from the mining of ornamental rocks and said drilling residues is residues resulting from onshore oil wells.

32. The use according to claim 31 , characterized in that said residues is classified as belonging to Class ll-A and Class-ll-B, as per NBR 10.004/2007.

33. The use according to any one of claims 30 to 32, characterized in that said inactive or exhausted mining regions are selected from the group con- sisting of mines, quarries, fields, hills, mountains, slopes and land depressions. '