SYSTEMS AND METHODS FOR MONITORING SLOPE STABILITY

Abstract

This description relates to the monitoring and evaluation of mechanical stability and fluid accumulation on natural or artificial slopes comprising mainly unconsolidated material, such as embankments, dams, roads, landfills, as well as artificial piles of bulk materials that may occur in the storage of grains, gravel, stones, sand, coal, cement, fly ash, salts, chemicals, clays, crushed limestone, as well as piles of mining minerals, including crushed, ground and / or agglomerated minerals and materials as they come out of the mine.

Description

SYSTEMS AND METHODS FOR MONITORING SLOPE STABILITY CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority over the U.S. provisional application serial no. 62 / 939,156, filed on November 22, 2019, the contents of which are incorporated herein in full by reference. FIELD This description relates to the monitoring and evaluation of mechanical stability and fluid accumulation in natural or artificial slopes, primarily including unconsolidated materials such as embankments, dams, roads, and landfills. This description also relates to the monitoring and evaluation of mechanical stability and fluid accumulation in artificial stockpiles of bulk materials, which may occur in the storage of grains, gravel, stones, sand, coal, cement, fly ash, salts, chemicals, clays, and crushed limestone. Furthermore, this description relates to the monitoring and evaluation of mechanical stability and fluid accumulation in stockpiles of mining minerals, including crushed, ground, and / or agglomerated minerals.This description also relates to the monitoring and evaluation of mechanical stability and fluid accumulation in materials as they come out of the mine. Monitoring unconsolidated materials for mechanical stability and fluid accumulation is a significant challenge. Slope failures and landslides of unconsolidated materials, soft soils, and sediments generally occur when the static stress due to the weight of the accumulated material exceeds the shear strength of the material itself. The literature distinguishes between different failure modes, such as translational failure, rotational failure, and wedge failure. Such monitoring is critical in the mining industry, where personnel are frequently in close proximity to large quantities of unconsolidated materials that pose an occupational hazard. In some cases, the extracted ore is oxidized or calcined at high temperatures before being stockpiled for later processing. Unconsolidated materials can also be found in tunnels, including mining tunnels, and generally during the excavation of large pits, canals, roads, and a variety of other earthworks. Piles of unconsolidated materials are also encountered when valuable materials such as ores, coal, and bauxite are transported, stored, and shipped (for example, on ships such as bulk carriers). Also within the mining industry, large accumulations of unconsolidated materials are found in "heap leaching," which is a production technique commonly used for one or more base and precious metals, including copper, gold, silver, nickel, and uranium. MA / a / ZUZZ / UUOl zo During heap leaching, large piles of unconsolidated material are irrigated with a leaching solution. These piles frequently exceed 10 meters in height and can reach over 100 meters. The leaching solution is selected to cause valuable minerals to leach out of the ore. Heap leaching is a chemical extraction process that involves irrigating a large pile of unconsolidated material, including crushed or mechanically prepared ore, with a chemical solution. The chemical extraction of metals using aqueous solutions containing acids, salts, and other agents is generally referred to as hydrometallurgy. Heap leaching of these metals often involves accumulations of unconsolidated material that can exceed 10 meters or even 100 meters in height. A heap failure can severely damage valuable mining and material handling equipment and is dangerous for anyone nearby. For leach pads, which are typically constructed on a lined surface, the most common stability failure mechanism is block or translational failure along the interface with the lowest shear strength parameters, which is usually the liner. More complex composite failure modes are also possible. Another problem is that, in certain mining operations, sludge and fluids from a variety of chemical refining or hydrometallurgical processes accumulate in large tailings ponds. It is common practice in the industry to construct the containment walls for these tailings ponds from excavated and potentially poorly consolidated material. The material contained in the tailings pond typically contains a large amount of water. Mine operators are often interested in recovering the water contained in the tailings ponds and recycling it back into the mining process. Upon closure of mining operations, the water contained in a tailings pond must be removed to allow for soil remediation and proper abandonment of the area in accordance with best environmental practices. In many cases, the tailings ponds and their associated containment walls remain after the conclusion of mining operations.In most cases, slope failure occurs within an accumulation of unconsolidated material and depends largely on the volume of fluids within the pore space of the material itself. The volume of fluids can change as a result of artificial irrigation, rain and snow accumulation, permafrost thaw, or changes in the water table of the underlying aquifer. Excessive fluid accumulations lead to a buildup of pore pressure within the material, which in turn results in a reduction of frictional strength and cohesion—for example, a loss of overall shear strength. Under these conditions, the unconsolidated slope will eventually fail under its own weight.In the case of a mining heap, where fluid can become trapped in varying concentrations due to complex fluid percolation patterns and flow barriers (such as permeability plugs), slope failure can also occur at the base or top of the heap. In general, slope failure can also depend on the heterogeneity and size distribution of the unconsolidated material and the geomorphology of the terrain. Sudden slope failure, also known as slope collapse or slope liquefaction, poses an ongoing risk to the mining, construction, and freight industries, as well as to any area where large quantities of materials are stored. It is also a natural hazard, which can result in landslides and soil movements in a variety of terrains and environments. These risks are often exacerbated by events such as heavy rainfall, snowmelt, and seismic activity. Seismic events can trigger slope liquefaction by causing a sudden increase in pore water pressure or water accumulation, leading to a reduction in the slope's shear strength. Slope failure can result in tragic loss of life, environmental damage, damage to specialized equipment or infrastructure, and a significant loss of productive time. Furthermore, for a given set of unconsolidated material characteristics (including permeability, porosity, and / or roughness), the optimal geometry and aspect ratio of a stockpile, retaining wall, or slope—including an artificial slope resulting from construction and engineering work—can be determined based on the actual volume of fluids present or expected to be present within the stockpiles and the availability of means to control those volumes on a large scale. An optimal stockpile or slope design can lead to preferred outcomes, such as increased metal extraction from leach pads, extended asset life, operational continuity, or enhanced operational safety. Dewatering is often used as a mitigation strategy against liquefaction or slope failure in, for example, open-pit mining operations, or to mitigate the settlement or subsidence of heavy structures such as buildings, bridges, or foundations during construction or excavation. In mining, dewatering strategies are also used to allow the safe movement of heavy equipment and machinery, including surface equipment that must travel over areas that have been previously flooded, for example, due to seasonal rains. However, dewatering can be a complex and costly process with a wide range of techniques and equipment available. The improper deployment of dewatering strategies will not only result in MA / a / ZUZZ / UUOl zo excessive costs, but it can also fail to prevent slope failure as expected. The dehydration of active or previously abandoned mine shafts and tunnels is a constant concern for mine safety, particularly when these areas are difficult to access. Drilling or breaching an abandoned mine shaft filled with water can pose a considerable risk of equipment loss, asset damage, or even loss of life. Many underground mines can only operate with pumps that actively remove water seeping from the subsurface into the tunnels and other structures. The risk of changes in fluid levels is present in rocky but highly porous materials such as limestone or karst. In fact, seasonal flooding can be a recurring problem in such areas, and monitoring groundwater levels can help develop mitigation or dewatering strategies. A common associated phenomenon is the formation of a sinkhole, which can occur in densely populated areas. For example, a sinkhole can form when the surface of a rock subsides as it is eroded from below by a rising water table. Based on the above, there is an ongoing need to monitor and map changes in fluid levels at depth within large volumes of earth, including slopes, tunnels, or mine shafts. Such monitoring is important not only for preventing slope failures but also for planning and operating dewatering, water reclamation, soil remediation, or spill mitigation operations. For example, knowing the amount of fluid present in the sludge and unconsolidated sediments contained in a tailings pond can inform the operator about the effectiveness and residual value of any water reclamation and densification operation, the optimal placement of dewatering pumps or channels, and how to plan water reclamation and densification operations.In soil reclamation activities, densification is a primary objective. The goal is to restore moist soil to a state with sufficient shear strength to support the weight of people, vehicles, buildings, reforestation, or similar activities without sinking or shifting. Densification requires removing most of the water trapped within the soil grains as a result of industrial processes such as mining operations. For these and other applications, having a way to directly monitor soil density is critical. BRIEF DESCRIPTION OF THE INVENTION This summary is provided to comply with § 1.73 of Title 37 of the CFR, which requires a summary of the invention briefly stating the nature and substance of the invention. It is presented and understood not to be used to interpret or limit the scope or MA / a / ZUZZ / UUO 1 or meaning of the claims.In one embodiment, there is a method for monitoring slope stability by determining the density of at least a portion of a heap by measuring the incidence of atmospheric muons, wherein the method comprises: associating one or more muon detectors with the heap by placing a muon detector within an upper lining material, placing a muon detector within a trench, borehole, tunnel, or pipe located beneath an impermeable lining, placing a muon detector within a trench, borehole, tunnel, or pipe located within a first portion of the heap, placing a muon detector within a trench, borehole, tunnel, or pipe that is horizontally offset from the heap, placing a muon detector on the floor of a pit located between two or more heaps, placing a muon detector on a side surface of the heap, or a combination of the above placements.Measure the incidence of atmospheric muons on one or more muon detectors, and determine the density of at least a portion of the heap by comparing the incidence of atmospheric muons detected by one or more muon detectors with a known muon attenuation of the materials in the heap and a known muon flux at the Earth's surface. In another modality, comparing the incidence of atmospheric muons with a known attenuation of the materials in the heap includes one or more of: comparing the muon attenuation for a known density of an initial sample of the heap materials with the muon attenuation in the heap, comparing the muon attenuation in the heap measured over a previous time interval with the muon attenuation in the heap, comparing the muon attenuation of the process fluids with the measured incidence of atmospheric muons on one or more muon detectors, or comparing the muon attenuation in the heap with a known muon flux at the earth's surface, including a surface flux measured by a secondary detector. In another modality, the initial sample of the heap materials is one or more samples of a dry mineral, a sample of pre-moistened mineral, or an agglomerated mineral. In another modality, the initial sample of materials from the pile is measured from two or more different locations in the pile. In another modality, the measured incidence of atmospheric muons is measured by detecting at least two muon trajectories that are oriented in different directions. In another modality, there is also a stage of moving at least one muon detector. In another modality, associating one or more muon detectors with the heap includes placing a muon detector inside a top lining material. In another approach, associating one or more muon detectors with the heap involves placing a muon detector inside a trench, borehole, tunnel, or pipe located below MA / a / ZUZZ / UUOl zo an impermeable lining or between the first part of the pile and a second part of the pile. In another configuration, the heap includes two or more leach pad area modules. In another configuration, associating one or more muon detectors with the heap includes placing a muon detector within a trench, borehole, tunnel, or pipe that is horizontally offset from the heap. In another scenario, the pile is a dam. In another modality, associating one or more muon detectors includes placing at least one muon detector that is horizontally displaced from the tip of the dam or placing at least one muon detector that is horizontally displaced within the dam and below the materials retained by the dam. In another modality, associating one or more muon detectors with the pile includes placing a muon detector on the floor of a pit that is located between two or more piles. In another modality, associating one or more muon detectors with the heap includes placing a muon detector on a lateral surface of the heap. In another modality, it also includes determining a fluid content of at least a part of the pile by measuring, for the part of the pile that includes unconsolidated material, a change in the apparent density of the unconsolidated material between an initial sample value and a current value. In one embodiment, there is a system for monitoring slope stability by determining the density of at least a portion of a heap by measuring the incidence of atmospheric muons, where the system comprises: one or more muon detectors associated with the heap that are located within an upper lining material, within a trench, borehole, tunnel, or pipe located below an impermeable lining, within a trench, borehole, tunnel, or pipe located within a first portion of the heap, within a trench, borehole, tunnel, or pipe that is horizontally offset from the heap, on the floor of a pit located between two or more heaps, on a side surface of the heap, or a combination of the above locations, wherein the system measures the incidence of atmospheric muons on one or more muon detectors,and wherein the system determines the density of at least a portion of the heap by comparing the incidence of atmospheric muons detected by one or more muon detectors with a known muon attenuation of the materials in the heap and a known muon flux at the Earth's surface. In another configuration, the heap includes two or more leach pad area modules. In another configuration, one or more muon detectors associated with the heap are located within a trench, borehole, tunnel, or pipe that is horizontally offset from the MA / a / ZUZZ / UUOl zo montón. In another scenario, the pile is a dam. In another modality, one or more muon detectors are associated with the dam by placing them horizontally offset from the pile outside the dam or by placing them inside the dam and under the materials retained by the dam. In another modality, one or more muon detectors are associated with the pile by placing them on the floor of a pit that is located between two or more piles. In another modality, one or more muon detectors are associated with the heap by placing them on a lateral surface of the heap. In another mode, the system also determines a fluid content of at least a part of the pile by measuring, for the part of the pile that includes unconsolidated material, a change in the apparent density of the unconsolidated material between an initial sample value and a current value. Additional modalities are also described. In one embodiment, there is a method for determining the volume fraction of fluids within an accumulation of unconsolidated material, such as a pile, heap, or tailings pond wall, or an underground mining tunnel, wherein the method is based on first determining an excess bulk density distribution in the unconsolidated material from an analysis of the attenuation of atmospheric muon flux through the accumulated material compared to the intrinsic matrix density of the unconsolidated material or its bulk density under initial conditions, including dry conditions or conditions at various compaction levels, wherein the muon flux through the accumulated material is measured along multiple directions from a muon detector having directional sensitivity and trajectory reconstruction capabilities.and where the excess apparent density is further analyzed to determine the volumetric fraction of fluids or the moisture content within the pore spaces of the unconsolidated material. In another modality, the volumetric fraction of the fluids is also analyzed together with a model of mechanical stresses within the unconsolidated material to determine an interstitial pressure within the accumulated material, and the volumetric fraction is determined by a model that takes into account soil compaction, and / or evaporation of water into the air and / or temperature changes in the pile. In another approach, changes in the volumetric fraction of fluids are determined from an analysis of the distribution of excess bulk density measured over time. In yet another approach, accumulated pore pressure is used to determine the risk of liquefaction or collapse of the accumulated material, including the risk of slope collapse for the walls of an open pit or containment pond, or the risk of landslides. MA / a / ZUZZ / UUOl zo In another modality, there is a method to determine the optimal processing time for mineral dissolution and metal extraction from a pile of crushed mineral material based on the determination of the amount of process fluids, such as leaching fluids, in the pile. In another modality, there is a method to optimize the economic value of said pile of crushed mineral material based on an analysis of the amount of process fluids and their distribution in the pile, the processing time required for the extraction of metal from different areas in the pile and the risk of slope collapse or liquefaction of piles due to accumulated interstitial pressure. In another modality, there is a method where the optimization enabled by the determination of moisture content through a density measurement using atmospheric muons is carried out by taking advantage of a variety of external parameters, such as the mineral composition of the material and its heterogeneity in the pile or the temperature profile throughout the pile. In one modality, there is a method to reduce or optimize the consumption of leaching solution on a leaching pad for a given tonnage of metal recovered and an estimated net present value (NPV) of the asset. In another modality, there is a method for determining the best remediation strategy and locating areas where intervention can take place to increase extraction efficiency; such intervention may include altering the flow of leaching in irrigation pipes or sprinklers to favor certain parts of the heap; other interventions may include creating drainage channels, including surface drainage channels or drainage boreholes, as well as intervention boreholes to deliver process fluids, air, or bacteria control agents at depth. In another modality, the appropriate corrective actions against slope collapse are determined from an analysis of the distribution of fluid volumes within the unconsolidated material. In another approach, appropriate corrective actions include determining the optimal location and depth of drilled dewatering holes to reduce accumulated pore pressure. In one modality, there is a method to assess the stability of access roads and make an informed decision about the passage of heavy trucks or machinery. In one embodiment, there is a system for determining the flux and direction of atmospheric muons through unaccumulated material, wherein said system further comprises a segmented detector consisting of a combination of scintillator and Cherenkov detectors, wherein the scintillator and Cherenkov detector can have substantially different shapes or segmentations to further optimize the determination of the trajectory of incoming atmospheric muons and the selection of signals due exclusively to ultrarelativistic particle radiation, such as the atmospheric muon, from other sources of nuclear radiation, including natural radioactivity due to materials and minerals contained in a heap of mining materials, and the light produced in the scintillator or in the Cherenkov detectors or in both is collected by different fiber optic collimators, including collimators of different sizes.and routed independently to separate photosensitive channels or detectors through a multitude of optical fibers. In another modality, individual photodetector channels may belong to one of the groups of multi-anode photomultipliers, solid-state photodetectors (such as silicon photomultipliers), electron multipliers, microchannel plates, and scientific cameras, including any combination of these. In another configuration, the photosensitive detectors are separable from the combination of scintillator and Cerenkov detectors, and the position of the photosensitive detectors within the system for measuring atmospheric muon flux is optimized in terms of space and geometric constraints. In another modality, the segmented optical detector elements are placed in multiple parallel planes separated by an optimized distance in order to optimize an angular resolution with which the directions of incoming atmospheric muons are determined. In another configuration, the segmented optical detector elements are placed on the outer ring of a cylindrical tool suitable for placement in a borehole. In another modality, at least one muon detector is placed on a transport medium and the transport medium includes one or more pulleys, a rail system or traction-generating wheels that allow the muon detector to be moved to different points under the pile of material being monitored, and the auger has an opening at each distal end to provide measurements at different viewing angles or to allow maintenance and reuse of the detector. In one embodiment, there is a distributed muon detector system that includes an array of unpowered optical detection units consisting of a combination of segmented scintillator and / or Cherenkov detectors, wherein multiple optical signals from the different and substantially well-separated optical detection units are collected through optical fibers and routed with minimal signal loss to an independent signal processing unit. In another embodiment, there is at least one independent processing unit that also comprises a power supply, a combination of multichannel photodetectors or multiple photodetectors and multichannel digitizing electronics. In another configuration, the independent processing unit also includes data ports for data transfer and control, or a dedicated network computer that includes a computer with a wireless or wired data connection. In another modality, the distributed detection units and light-collecting optical fibers are buried in a trench, such as a trench under a pile of mining material or in the top lining section of a leaching heap, or are placed through multiple holes located around an accumulation of unconsolidated material. In another modality, there is a semi-autonomous system for the detection of atmospheric muons that is battery-powered and optionally includes one or more of a set of solar panels, a wind turbine, a gasoline generator, a natural gas generator, or a diesel generator. In one modality, there is a method to facilitate the remediation of wet soils, such as those of tailings ponds, based on a measurement of the density of the moisture-rich material, according to which the shear strength of the remediated material can be determined. In one modality, there is a method to facilitate the recovery of water from tailings ponds based on the measurement of the overall density by accumulation of coarse grains, fine grains and sediments, with which to determine the amount of recoverable free water. In one mode, there is a visualization interface for moving the moisture content or measured density from a muon detector system where the data is displayed in a 2D projection superimposed on the presence of irrigation lines and mining equipment in a spatially realistic manner. In another mode, the visualization interface is configured to show moisture content trends over time for each of the measurement voxels, including the visualization of supersaturation or undersaturation conditions that relate to the risk of slope collapse or low efficiency for metal extraction by leaching. In one modality, there is a method for determining the location and distance of pre-existing tunnels when conducting underground mining drilling operations, for example, to reduce the risk of intersecting pre-existing tunnels that may be filled with water. In one configuration, the system is portable and configured to be transported around an underground mine by vehicle to perform prospecting with a single sensor. BRIEF DESCRIPTION OF THE DRAWINGS The aspects, characteristics, benefits and advantages of the modalities described herein MA / a / ZUZZ / UUOl zo document will be evident with respect to the following description, the accompanying claims and the accompanying figures where: Figure 1 is a schematic view of at least a part of a system according to the present description. Figure 2 is a schematic view of at least a part of a system according to the present description. Figure 3 is a schematic view of at least a part of a system according to the present description. Figure 4 is a schematic view of at least part of a system according to the present description. Figure 5A is a schematic view of at least a part of a system according to the present description. Figure 5B is a schematic view of at least a part of a system according to the present description. Figure 6 is a schematic view of at least a part of a system according to the present description. Figure 7 is a schematic view of a scintillator according to the present description. Figure 8 is a schematic view of a scintillator sensor element according to the present description. Figure 9 is a schematic view of an elongated scintillator according to the present description. Figure 10A is a schematic view of a muon detector according to the present description. Figure 10B is a schematic view of a muon detector according to the present description. DETAILED DESCRIPTION OF THE INVENTION This description is not limited to the specific systems, devices, and methods described, as these may vary. The terminology used herein is solely for the purpose of describing particular versions or modalities and is not intended to limit the scope. As used herein, the forms “a” and “the” include plural references unless the context clearly indicates otherwise. Unless otherwise defined, all technical and scientific terms used herein have the same meanings commonly understood by a person skilled in the art. Nothing in this description should be construed as an admission that the modalities described herein are not entitled to predate this description under any law. MA / a / ZUZZ / UUOl zo a prior invention. As used herein, the term "comprising" means "including, among others." This description offers an alternative method for monitoring slope stability and determining fluid volumes within large structures such as stockpiles, mine leach pads, pond retaining walls, artificial dams, underground tunnels, open pits, or access roads. The systems and methods described herein are based on a direct measurement of excess bulk density due to fluid accumulation, which can be directly interpreted in terms of the total mass or volume of fluid within the unconsolidated material. This description is not exhaustive and is applicable to monitoring the stability of open-pit and underground mine walls, as well as the stability of bulk cargo or stored materials. As used herein, the terms “heap,” “pile of material,” “wall,” or “walls” mean a mass of unconsolidated material. As described above, the specific form of the unconsolidated material constituting the heap, pile of material, wall, or walls is not exhaustive and includes one or more piles of material, pond retaining walls, pond containment dams, artificial dams, tunnels, open ditches, or access roads. As used herein, "unconsolidated material" means sediment that is loose or unstratified, or whose particles are not cemented, found at the surface or at depth. A measure of apparent density is determined by measuring the rate of atmospheric muon events passing through the volume of unconsolidated material under investigation. Atmospheric muons are part of the natural cosmic ray flux and arrive from space at all points on the Earth's surface. The atmospheric muon flux is measured by the number of particles passing through a solid, centered at an angle around a given direction, per unit time. Similar to X-ray radiography, and for a given incoming muon flux, the attenuation of the muon flux through a given section of a heap, dam wall, open pit walls, underground structure, or similar object, depends on the average bulk density of the material integrated along the particle (muon) path through the volume under investigation.The apparent density thus measured is the average density of all materials within the volume under investigation, including rock grains, fluids, and empty pore spaces. By measuring the muon flux through such an object of interest along different directions, it is possible to create a map of the apparent density distribution. Muon flux measurement is obtained with one or more muon detectors that can MA / a / ZUZZ / UUOl zo are placed at different viewing angles with respect to the object or volume under investigation. From the muon flux measurements through the volume, a three-dimensional tomographic density map can be formed. In some modalities, a single measurement point is provided, and the density information remains three-dimensional in nature but can be represented by a two-dimensional projection. In other modalities, multiple measurement points are provided. As described herein, each muon detector can detect the passage of single-particle muon events and can also determine the direction of those events. Muon detectors are not limited to and include one or more scintillator detectors, gas detectors, solid-state detectors (e.g., silicon detectors and TFT arrays), transition radiation detectors, and Cherenkov detectors. As those skilled in the technique will understand, the density of the initial phase of the unconsolidated material is either measured separately in situ or is a known value. The initial phase of the unconsolidated material includes one or more of a dry mineral material, a pre-wetted mineral material, or an agglomerated mineral material. In certain methods, the density of the initial phase of the unconsolidated material is measured by obtaining multiple samples from different locations within the mining operation. After the density of the initial phase has been measured separately or otherwise determined, it can be used in calculations to determine the fluid content. Any change in the apparent density of the unconsolidated material compared to the initial phase, including spatial changes or changes over time due to an approaching fluid front, can be interpreted as a change due to the presence of fluid volumes in the unconsolidated material. The average apparent density pb of the unconsolidated material governs the muon flux, and pb is given by Equation 1, where φ is the matrix porosity of the unconsolidated material and pm is the matrix density. In Equation 1, no fluid is present, and the contribution of air is neglected. Pf = ^-φ)Pm (1) For materials with a pore space totally or partially filled by fluids, the apparent density is shown in Equation 2, where S is the fraction of the empty pore space in the material occupied by the fluid, also known as fluid saturation in the material or moisture content of the material, and pt is the density of the fluid. P = Pb = (1 - Φ')pm+ φSρf(2) For the cases mentioned above, including that of a leaching fluid seeping through a heap, pt is well known and approximately equal to the density of water. Therefore, a measurement of a representative, well-mixed sample of dry or initial materials provides a direct measurement of their porosity, while a comparison between the bulk density under dry or initial and saturated conditions yields a direct determination of the fluid saturation S. In many cases, φ is known or can be determined beforehand, and thus any measurement of an excess bulk density distribution in a heap or wall is a direct measurement of the fluid contained within the heap or wall. Adjustments can also be made, as experts will appreciate, to account for compaction or settlement of the heap by its own weight.When this measurement is performed using a single muon detector with the required particle tracking capabilities, an accurate 3D analysis of the fluid distribution is obtained. When multiple detectors are used, additional constraints on the density distribution can be imposed, or the coverage can be expanded. Because muons are highly penetrating, energetic subatomic particles, the volume investigated can be very large. In certain configurations, the piles can be tens of meters high. In other configurations, thick walls can be investigated, including retaining walls for tailings ponds frequently used in mining operations. The volume of unconsolidated material that can be investigated can be at least 10 m³, at least 100 m³, at least 1,000 m³, at least 100,000 m³, at least 500,000 m³, or at least approximately 1,000,000 m³, and closed intervals formed by combining two or more of the above values ​​as endpoints. It is well known that the average atmospheric muon flux on Earth has different intensities at different elevations and latitudes. Furthermore, it can change slowly over time due to effects related to the solar activity cycle and any induced variations in Earth's magnetosphere in space. Other variations can arise from changes in overall density throughout the atmospheric air column, such as seasonal changes. Finally, the muon flux at very high angles to the vertical could be affected by the presence of geographical features, such as nearby mountains, which could effectively act as a filter. These variations can introduce a systematic error in our measurement of muon opacity, which is the effective attenuation of the muon flux through bulk matter. It is possible to minimize systematic effects due to uncertainties in muon flux normalization using one or more reference detectors by normalizing at least one density map to the muon flux measured along a fixed reference direction, or by normalizing at least one density map to a map taken during a previous time interval. When density maps are normalized to the muon flux measured along a fixed reference direction, it is possible to reconstruct a spatially relevant relative density map that remains valuable for assessing slope stability. In certain preferred configurations, it is also possible to normalize the overall atmospheric muon flux using muon trajectories arriving at the detector from a direction outside the region of interest or the volume under investigation. This is known as side-tracking normalization.For example, in monitoring piles or walls, a detector placed on the outer surface of the pile can distinguish the muon paths that have passed through the pile (and therefore carry information about its density) from the paths that reach the opposite side of the detector, which carry information about the local atmospheric muon flux required for normalizing muon opacity measurements. The description includes similar configurations for monitoring open pit walls, cargo, and other accumulations of bulk materials. Figure 1 illustrates one embodiment of the description. In Figure 1, muon detectors 201 and 202 are positioned around a section of a material heap 100, which may be a heap of ore extracted from a leach pad. The heap 100 further comprises two side walls 102 and a top surface 101. It should be noted that, although the heap 100 is depicted in Figure 1 as having a flat, rectangular top surface, the shape of the heap is not so rigid. Heaps can have irregular shapes, including shapes with varying elevations or a non-polygonal outline. Muon detector 201 is positioned laterally on the heap, and muon detector 202 is positioned beneath it. A plurality of muon particles originating from space traverse the heap, first passing over the top of the heap and then reaching muon detectors 201 and 202.Muon particles pass through the heap in all possible directions. Muon detectors 201 and 202 can detect the arrival of each muon particle at their surface and determine the muon's incoming direction, event by event. According to Figure 1, muon trajectories 301a and 301b pass through heap 100 and reach detector 201, and muon trajectories 302a and 302b pass through heap 100 and reach detectors 201 and 202. Muon trajectory 302c does not pass through the heap, but nevertheless reaches detector 201. Muon trajectories 310 and 311 also pass through at least part of heap 100, but because these trajectories do not reach any muon detector, their arrival and direction are not recorded.Experts in the technology acknowledge that, in some modes, muon detectors 201 and 202 have an intrinsic angular resolution, meaning that muon arrival trajectories can only be determined within a certain solid angle, and that this angular resolution differs for muon particles arriving from different directions. Furthermore, it is also recognized that information about density and fluidity can only be obtained after sufficiently high event statistics have accumulated over time. Therefore, in certain modes, muon trajectories are grouped into voxels. ML / a / ZUZZ / UUO 1 three-dimensional zo that are larger than the solid angle due to the resolution of the muon detectors. The muon trajectories belonging to a particular voxel are summed and analyzed together to calculate the average value of the apparent density and / or the amount of liquid within the volume of the voxel itself. For example, and with reference again to Figure 1, the surface 101 of heap 100 is subdivided into a grid 103, with each grid pixel defining the base of the truncated pyramid voxels 401, 402a, and 402b, each traversed by a small subset of the total muon flux. Due to the directional nature of muon detector resolution and in combination with the muon detector's orientation, the muon flux can be mapped three-dimensionally. The size and shape of each pixel in grid 103 are not fixed and can be modified when viewing the density map. In some cases, it may be advantageous to choose a finer or coarser grid based on the available statistics. For example, the grid spacing can be chosen based on the uncertainty with which the apparent density can be determined due to the intrinsic statistical nature of the measurement, including choosing a grid with non-uniform spacing or a grid that defines inverted pyramidal voxels with an increasing base area (at the top of the heap) as one moves away from the location of the muon detector below the heap.In particular, as the muon rate decreases for larger muon angles relative to the vertical, the statistical precision of the method decreases and can be improved by increasing the pixel size, for example, by favoring measurement precision over position reconstruction. In some other cases, the grid 103 can become denser, and the volume of each voxel 401, 402a, and 402b can be reduced over time as more and more muon trajectories are measured in the detector. In such cases, one can effectively opt to compensate for greater measurement sensitivity with greater position resolution over time, as defined by the choice of pixel areas throughout the volume. In still other modalities, the pixels can have a non-rectangular base, for example, the base of the pixel can be an arc segment.In one such modality, instead of a square grid, the pixel would be arranged to form concentric circles or arc segments. Those skilled in the art will understand that muon tracking data in a muon detector can be collected simultaneously in many directions and can be organized into an arbitrary number of voxels. When multiple detectors are implemented in a stack, some of the voxels may overlap with each other, which can further restrict the three-dimensional analysis of the density in the stack. Those skilled in the art will also understand that in the modalities where a detector When a muon detector is placed near the edge of a pile, the muon detector will also measure the trajectories of lateral muons, such as trajectory 301b, which will provide an independent local measurement of the flux of incoming atmospheric muons, or of a muon flux not affected by the water content within the volume under investigation. When such independent measurements are obtained, they can normalize the apparent muon flux measured by other muon detectors. The number, position, orientation, and size of the muon detectors are not restrictive. The muon detectors can be selected, oriented, and positioned according to prospecting design optimization techniques that take into account the shape of the unconsolidated material volume being investigated, the thickness of the unconsolidated material, the desired precision in density measurement for a particular observation time, the total cost of the muon detector hardware, and the ease of installation and, therefore, the cost of installing the muon detectors. In most cases, prospecting design optimization is performed based on direct model simulations that predict an expected counting rate as a function of at least one of the muon detector positions, muon detector segmentation, and trajectory reconstruction efficiency and precision.This optimization of the survey design can also be used to determine the shape, size and orientation of each muon detector, as well as the orientation of the active detector elements that determine the muon trajectories. In certain modalities, one or more of the muon detectors are segmented. The segmentation is not limited and includes detector plane layers or surfaces that contain individual detection elements in a crossed pattern (such as simple X-Y patterns, ladders, helical patterns). The segmentation provides the ability to measure multiple points along the direction of the muon, which allows for the reconstruction of a straight trajectory. In such modalities, the segmentation determines the trajectory resolution capabilities of the detector. Ultimately, the segmentation determines the trajectory resolution capabilities of the detector. Greater segmentation will generally result in a more precise trajectory reconstruction, which could be used to obtain a finer reconstructed density map.However, segmentation also increases the cost of the muon detector because it increases the number of sensor elements required and the number of electronic channels required. The construction of muon detectors is not restrictive and includes one or more gas electron multipliers (GEMs), wiring chambers, liquid chambers, and / or time projection chambers that can reconstruct a muon trajectory with the information left by the muon ionization trajectory in a single gas volume. In many pile density mapping applications, it may be advantageous to place the MA / a / ZUZZ / UUOl muon detector at the base of the heap and bury the muon detector beneath the heap while the heap is being constructed. Alternatively, the muon detector can be placed within or on top of the upper coating material or beneath the leaching platform when buried, or the muon detector can be placed directly on top of the fluid-impermeable coating of the leaching platform. In some embodiments, the muon detector can be placed beneath the fluid-impermeable coating. The placement of one or more muon detectors can be achieved by at least one of a hole, a trench, a horizontal borehole, a vertical borehole, an inclined borehole (i.e., drilled at an angle), or a directional drilling borehole (this is different from inclined, i.e., a well that changes direction).Placing the muon detector in this way maximizes the viewing angle of the muon detector or of a system that includes a plurality of muon detectors. In heap leaching, the operator needs to recover the leaching fluid that has passed through the material because it contains high levels of dissolved metals and the extracted metal. For this purpose, leaching pads are constructed on a fluid-impermeable liner. Immediately above the liner is a layer known as the top liner section. The top liner section includes a matrix of highly permeable liner material to facilitate the collection of the leaching fluid and the dissolved metals it contains into collection pipes for transport to a processing plant (typically a solvent extraction and electrowinning plant). The mineral material to be processed is placed or stacked on top of the top liner.Once processing is complete, the mineral material can be removed and disposed of to provide space for the freshly mined ore to be placed on the leach pad. Reusing an existing leach pad can be cost-effective and minimizes the area required for mineral processing. A plurality of collection pipes are placed within the top lining material to collect the leaching fluid. In certain other methods referred to herein as static heap leaching, a multi-stage process is employed. During static heap leaching, a first liner is placed in position, and a first volume of ore is deposited on top of it. The first liner is impermeable to fluids and collects any fluid that seeps through any volume of ore placed above it. The first volume of ore is irrigated, and a first leaching fluid, charged with extracting metals, is collected. Once irrigation and the collection of the first leaching fluid are complete, a second liner is optionally placed. MA / a / ZUZZ / UUOl or lining over the first ore volume, and a second ore volume is deposited over the second optional lining. Although two layers of lining and ore volume are described above, it is appreciated that any number of alternating linings and ore volumes can be provided, and that additional linings above the first lining are not necessarily required. Between each pair of ore volumes, linings are optional. However, as described above, there must be at least one lining below the lowest ore volume to collect any fluid that seeps through any ore volume placed above the line.In static heap leaching, when the irrigation of a volume of ore is stopped and a new liner is placed on the volume of ore, the density of the volume of ore does not change substantially and, therefore, for ease of analysis, any change in heap density over time can be attributed to additional volumes of ore being deposited. Static heap leaching can include 1, 2, 3, 4, 5, 6, 7, or 8 ore volumes. As described above, each layer can optionally include a liner. If a liner is included, an additional top liner layer can optionally be placed on top of and in contact with the existing liner. When no additional liners are included beyond the first liner, the leaching fluid filters from the top ore volume, through any intermediate ore volumes, and finally into the top liner layer and the corresponding liner, which collects the now-laden leaching fluid containing dissolved metals. Figure 2 depicts a static heap leaching configuration. In Figure 2, heap 100 includes a first liner 133, a first ore volume 132, an optional second liner 130, and a second ore volume 135. As described above, the second liner is impermeable to fluids irrigated from the top of heap 100, preventing fluids from entering the first ore volume 132. When the muon detector 202 is placed at the bottom of the first ore volume, the top surface 134 is divided into pixels that define density voxels 412a and 412b. In Figure 2, any density changes observed in the voxels can be attributed to fluid entering or leaving the second ore volume 133. In another method, metals are extracted from the ore by dynamic heap leaching. In dynamic heap leaching, so-called "on stacks" and "off stacks" are successively built up and dismantled at the end of the treatment process. In this case, a muon detector placed at the bottom of the heap is MA / a / ZUZZ / UUOl zo can be reused over time to analyze multiple heaps. In dynamic heap leaching, it is convenient to place the detector under the base liner of the pad or within the top liner material. In other cases, the heap leaching process is adapted to the terrain's morphology. For example, in valley fills or valley leaching operations, the leach pads are placed at the bottom of a valley, and the natural slope provides a convenient way to collect the process fluids that seep through the crushed ore pile. In these cases, because at least some portions of the surrounding terrain are above the crushed ore pile, muon detectors can be placed in boreholes, tunnels, or caves excavated on the side of the valley fill. In general, it is important that prospecting muon detectors do not interfere with the operation of equipment such as bucket-wheel excavators and moving ore conveyors used to build or dismantle the stockpile. In some configurations, it may be advantageous to place the detector in a borehole, including an inclined borehole, drilled to allow the detector to be positioned directly below the stockpile, albeit at a certain depth below the base lining. Multiple boreholes could be used, including horizontal boreholes or tunnels excavated to greater depths below the stockpile. To improve coverage, multiple muon detectors can be placed in different positions along the same borehole or within multiple boreholes. In some configurations, the muon detector is placed inside a pipe and configured to move within that pipe, which is located at the base of the heap. When the muon detector is placed inside a borehole, tunnel, or pipe, it can be moved to different positions beneath the heap to cover larger volumes more cost-effectively. In these configurations, the detector's position can be changed according to the heap construction schedule or associated mineral processing operations. These configurations are called mobile muon detectors. The movement of mobile muon detectors is not predetermined. The propulsion source for mobile muon detectors can be either internal or external. Internal propulsion sources include one or more integral electric motors, integral internal combustion engines, propellers, turbines, jets, or thrusters. External propulsion sources can include high-pressure liquid or gas within the borehole, tunnel, or pipe, similar to the scrapers used in oil pipelines, and cables used to pull the muon detector. When a cable is used to move a muon detector, it is called a tethered muon detector. The cable used with the muon detector can provide one or more power sources. MA / a / ZUZZ / UUOl electrical, data connections, or pressurized liquids or gases (such as compressed air). The cable can be shielded to prevent damage. It is also envisioned that a single cable or multiple cable segments together can move several mobile muon detectors simultaneously along a borehole, tunnel, or pipe. This allows for the reuse of the same sensor according to the operating schedule in, for example, a dynamic leaching heap. The mobile muon detectors can also be spaced according to the measurement requirements, for example, to provide multiple viewing angles or different spacing options, all without interfering with operations on the heap surface. The mobile muon detectors can be moved by a motorized winch system or even a hand-crank system.A mobile muon detector offers additional advantages in that it can be retrieved for maintenance or replacement. Finally, various combinations of multiple surface, borehole, and side detectors are considered to create an optimal survey of the heap under study. Each of Figures 3 and 4 represents a modality of the present description. Figure 3 shows a top view of a dynamic leaching pad, and Figure 4 shows a side view of the leaching pad in Figure 3. The leaching pad area 200 includes one or more leaching pad area modules 201, 202, 203, 204, 205, 206, 210, 211, 212, 213, 214, 215, 216, and 230. The size of the leaching pad area modules is not fixed and depends on the associated mining operation. In some modalities, the leaching pad area modules are approximately 50 m wide and approximately 150 m long. The leach pad area modules 201, 202, 203, 204, 205, 206, 210, 211, 212, 213, 214, 215, 216 and 230 are continuously emptied and filled by moving equipment, such as a mobile bucket wheel excavator 301 and a mobile stacker 302.The mobile bucket wheel excavator 301 and the mobile stacker 302 can move on rails 312, 313, 314. In some embodiments, the mobile bucket wheel excavator 301 and the mobile stacker 302 can move by means of continuous paths 312, 313, 314. As the excavator and the stacker advance at substantially the same speed, a gap 303 is maintained between the mobile bucket wheel excavator 301 and the mobile stacker 302. At one boundary of the gap 303, the mobile bucket wheel excavator 301 removes spent ore, and at the other boundary of the gap 303, the mobile stacker 302 deposits fresh ore for leaching. As shown in Figure 3 and Figure 4, the leach pad area module 203 is in the process of being filled with new material and, therefore, the leach pad area module is inactive and does not produce charged leach fluid for processing (although it is possible that some of the charged fluid is in the process of being MA / a / ZUZZ / UUOl (ore collected for processing). Mobile bucket wheel excavator 301 and mobile stacker 302 are moved and positioned according to the production schedule of the associated mine. The trajectories of equipment 312, 313, and 314 allow this equipment to turn 180 degrees and move to the next section of the leaching area, where leach pad area modules 211, 212, 213, 214, 215, 216, and 230 are located. In this way, all the pads that define leach pad area modules 201-206, 210-216, and 230 of leaching area 200 are continuously loaded with ore, irrigated with leaching fluid, and the spent ore is removed. With reference again to Figure 3 and Figure 4, horizontal boreholes 403 and 404 have been drilled to a predetermined depth below ground level 400 and contain muon detectors 104, 105, 106, 107, 108, and 109. In Figure 3, boreholes 403 and 404 are shown passing through the leach pad area system 200 and the leach pad area modules 201–206, 210–216, and 230. It should be noted that although boreholes 403 and 404 are shown passing through the aforementioned system, the number and configuration of boreholes 403 and 404 are not exhaustive. Other borehole configurations can also be advantageous, such as boreholes that traverse a leach pad area module in a transverse or inclined direction. In some cases, boreholes can be replaced by drilled tunnels or excavated trenches prior to leach pad construction.This can be useful in most implementations, but it is especially cost-effective when used in newly constructed heap leaching operations. This is because, in a new deployment, the borehole can be added before being covered with ore, thus avoiding the need for expensive tunneling operations. Boreholes 403 and 404 can also be replaced with pipes embedded in a heap, so that the pipes are used to collect the loaded leach solution that seeps to the bottom of the heap. As shown in Figure 3 and Figure 4, muon detectors 104–109 can be moved along the boreholes, and their position and spacing can be selected according to measurement needs or operator requirements. For example, in Figure 3, muon detectors 104 and 105 are positioned relatively close together to provide greater coverage in the area between production modules 213 and 214. One advantage of the configuration shown in Figures 3 and 4 is that the muon detectors 104–109 remain in place and can be reused during a cyclical mining operation, such as when spent ore from a leach pad area module is removed and replaced with fresh ore for processing. Therefore, this configuration allows the same infrastructure of muon detectors, drills, and similar equipment to screen a larger and more productive quantity of ore during operations. Figure 4 is a side cross-sectional view of the configuration in Figure 3, showing the fluid-impermeable lining 410 above ground level 400. The fluid-impermeable lining material 410 acts as a barrier to prevent process fluid from escaping into the ground. A special top lining material 411 is deposited over the fluid-impermeable lining 410. The top lining material 411 can be approximately 0.5 m to 1.0 m thick and is composed of highly permeable materials so that all fluids that leak from the modules in the leach pad area 211–214 are collected by collection pipes (not shown). The collection pipes are embedded in the top lining.Muon detectors 104, 105, and 108 are located in borehole 403 and detect the passage of muon trajectories and also the directions in which they intersect with the modules of the leach pad area 211, 212, 213, and 214. By reconstructing muon trajectories 420-425, it is possible to construct a density map of the heap over time. The drilling method for boreholes 403 and 404 is not exhaustive and includes drilling with one or more directional drilling tools, an inclined rig (including coiled tubing rigs), a tunnel boring machine, or a tool called a badger tool or excavator. Boreholes 403 and 404 may be double-ended boreholes with access from both sides and may feature a lining or casing material to protect their internal walls from collapse or deformation, as well as to facilitate repositioning muon detectors 104-109. Muon detectors 104-109 may also be retrieved for maintenance. Muon detectors 104-109 may be wheeled or attached to a track or transport system and be dragged or pushed from the surface along the borehole.In certain implementations, the wheels may be retractable, spring-loaded, or adjustable to different borehole diameters. To facilitate the movement of the muon detectors, such wheels can be positioned at various points around the azimuth defined by their housing. Without loss of generality, the wheels can be replaced by rollers to further facilitate the transport of each muon detector.104-109 In certain configurations, muon detectors are part of a distributed muon detection system. Each individual detector or sensor constitutes a node in this system, and the distributed muon detection system can be deployed and positioned to maximize heap coverage according to a prospecting design methodology. Monte Carlo simulations used to estimate the count rate, coverage, and sensitivity of each muon detector for a given heap geometry and thickness are one such prospecting design methodology capable of optimizing the position of MA / a / ZUZZ / UUOl zo muon detectors while considering the installation and muon detector costs. For example, in the case of shallow leach pads, such as those about 3 m thick, these techniques can be used to determine the preferred depth of the boreholes needed to optimize heap coverage with a few well-spaced measurement points. Conventional muon detectors are stand-alone units containing i) an array of sensing elements to determine the tracking information associated with a muon event; i) an integrated signal transducer capable of digitizing the sensing elements' information event by event, such as a photodetector system or a multichannel photodetector connected to custom signal digitization electronics; i) a telemetry or data communication system capable of transporting the digital information to a local or remote computer host; and iv) a connection to an external power source to provide the onboard power required for the readout electronics and telemetry system. For the distributed muon detector system described herein, novel configurations can be particularly advantageous. For example, the individual nodes described may consist solely of optical sensing elements (e.g., a scintillator array) connected by optical signal transmission lines, such as one or more flexible fiber optic cables. These fiber optic cables can be routed to one or more processing units external to the individual nodes, where the signal is subsequently digitized by optical sensors, and the event-by-event information is then processed and transmitted to a central computer. In this way, the individual nodes of the distributed sensor system may not require any electrical power connection.Given the low signal loss and relatively low cost of fiber optic cables, such a configuration can allow for the cost-effective connection of multiple passive sensing nodes over distances of up to hundreds of meters. When the processing unit is separated from the sensing nodes and placed outside the borehole or observation trench, a distributed sensor deployment can be highly cost-effective and particularly convenient for maintenance or troubleshooting. The nodes in the distributed muon detector system described herein can be independently connected to one or more data communication cables or optical signal transmission lines. The detection nodes can be passive, consisting only of the scintillator elements and optical connections, which do not require electrical power. Alternatively, the detection nodes can be battery-powered or connected via a power cable. For example, the detection nodes can also be MA / a / ZUZZ / UUOl zo connect to a pull cable, including combined multifunction cables that carry the signal and / or power and provide a means of moving the detection node. In certain other implementations, data communication to and from one or more detection nodes may take place via wireless communication. Finally, detector operation, including that of multiple nodes within a distributed muon detection system, may be remotely controlled from a common or shared signal processing unit conveniently located outside the heap, such as on the surface or in a trench. Data communication to and from the processing unit, including to and from a remote computing host, may use a cellular data network or proprietary communication networks.Similarly, electrical power for the central processing unit or for individual sensing nodes can be provided by a combination of batteries, including replaceable batteries, solar panel installation, small wind turbines, or gasoline or diesel generators. A distributed muon detection system, as described, can also be used to survey large structures such as tailings ponds in mining ponds, as well as to determine the density of the material within the tailings pond itself. Conventional tailings pond dams and other containment wall structures are designed with a 2:1 aspect ratio between the base of the dam and its height. This design presents challenges when using the cosmic ray method to determine the density distribution and water volumes within the structure because the smallest viewing angle available from the base of the dam can be as large as α(2 / 1) ~ 63 degrees from the vertical, or even larger when the aspect ratio is higher.Because the atmospheric muon flux has a strong peak in the vertical direction, relatively few muons are available at such large angles, resulting in reduced statistical accuracy, longer observation time, or both in determining density changes. With reference to Figure 5A, a retaining wall 500 is built on firm ground 501 and acts as a dam for a tailings pond 502. When the muon detector 503 is placed at the foot of the dam, the minimum angle at which it can receive useful muon trajectories 504-507 is at least Omin= atan(L / H) from the vertical direction. In contrast, and with reference to Figure 5B, when the muon detector 503 is vertically displaced in the borehole 508 at the front of the dam, the minimum viewing angle to the top of the dam becomes atan(L / (H+h)). Typically, dam heights are in the range of approximately 50 m to approximately 150 m; therefore, even a relatively shallow borehole or excavation can MA / a / ZUZZ / UUOl significantly improve the situation. Furthermore, with this implementation, it is now possible to analyze the dam face as shown by the muon trajectories 509 and 514. In still other configurations, not exclusive to those described above, a muon detector 518 could be placed inside the tailings pond itself. This provides access to a different set of muon trajectories 515-517 and 519 and viewing angles with which to further analyze the three-dimensional fluid distribution and density within the pond. This is particularly advantageous for monitoring the densification process at the base of the pond or soil reclamation, as well as for determining the residual water content in the pond. Furthermore, it is observed that in some situations (not shown), muon trajectories can pass through the tailings pond material 502 without passing through the dam 500 and subsequently strike the muon detector 503 after passing through the firm ground 501.Furthermore, in other soil stability implementations and applications, the muon detector can be placed at the bottom of a pit, such as an open pit used in mining operations. In this case, the detector can be primarily directed at analyzing the face of the pit wall, as shown in Figure 6. This configuration can be useful for monitoring the stability of the open pit wall. In Figure 6, the muon detector 600 is placed at the bottom of an open pit and can provide the fluid distribution behind the pit walls, as indicated by the muon paths 601 and 602. In many cases, pit excavation can reach depths greater than the water table (609). In such cases, water must be actively managed and pumped to continue operations, for example, using dewatering wells 603 and 604. However, the water table tends to rise and return to its original level. Water movement can be facilitated by the possible presence of one or more faults 605, which effectively provide a migration path for water that can result in seepage in the upper parts of the heap.For example, as water moves across the main water table surface 611, this results in elevated pore water pressure at locations 612, causing water to discharge from the seepage faces 610. As the volume of water in the walls increases, so does the pore water pressure, leading to a decrease in the rock's shear strength and an increased risk of slope failure. In certain configurations, it may be convenient to place a detector at several points along an access path that descends into the pit, for example, detector 607 at position 606. In still other configurations, detectors can also be placed in caves or tunnels specifically prepared to monitor slope stability, access a dewatering well, or that are specifically manufactured to allow muon detectors to monitor the presence of fluids deep within the pit walls. MA / a / ZUZZ / UUOl zo In order to construct a suitable muon detector, those knowledgeable in the field will recognize that several technologies are available. However, these are not necessarily cost-effective or suitable for field use. In one approach, a method used to determine the direction of subatomic particles, such as atmospheric muons, can involve determining multiple points along the particles' trajectory. This can be achieved with arrays of elongated strips of scintillating material, including scintillating fibers or sealed channels filled with a liquid scintillating material. With reference to Figure 7, a scintillator 700 is constructed using an arrangement of elongated scintillator elements 701–704 oriented along an X-direction, followed by a second plane of elongated scintillator elements (705–708) oriented primarily in an orthogonal Y-direction. When a muon passes through such a detector plane, its arrival position can be determined by comparing the data along the elongated X- and Y-oriented scintillator elements. A muon detector that includes at least two of these detector planes (i.e., two X-planes and two Y-planes) can determine two points along the cosmic ray path, from which the muon's original direction can be calculated. Typical lengths of each scintillator element are 0.5 to 2 m long, 0.5 to 2 cm thick, and 1 to 5 cm wide. Referring again to Figure 7, each of the scintillator elements in both planes is directly coupled to multiple optical detectors, as shown in 709-712, which are mounted directly at the end of the scintillator elements. In some embodiments, it may be more cost-effective or convenient to use a common multichannel optical detector such as a multi-anode photomultiplier tube or a solid-state multichannel photodetector. In these implementations, elements 709-712 would now simply be optical coupling ports where the scintillator light generated in the scintillator elements is collected in an optical fiber, such as a plastic or glass optical fiber. In one embodiment, and with reference to Figure 8, the scintillator sensor element 800 is made by filling a housing 801 with a liquid scintillator material 802. To maximize light collection efficiency while maintaining a sealed housing, the scintillator element 800 is coupled to a threaded fiber optic collimator 804. Fiber optic collimators have a relatively large-diameter lens that can efficiently extract the scintillator light and route it to a conventional optical fiber via a standard connector. Typically, the fiber optic collimator is separated from the liquid scintillator material by a glass window. In some implementations, the fiber optic collimator assembly may also include a condenser lens, which serves to align the paths of the light rays emerging from the window and facilitate light capture and transmission.As shown in Figure 8, a muon path 803 generates two scintillation events, the light from which is collected by the optical collimator 804. Optical fibers are thin and flexible and are therefore a preferred choice for routing multiple optical signals to a single multichannel optical detector. A threaded collimator insert is particularly advantageous because it maintains the airtight seal of the liquid scintillator housing and is generally more reliable for field use than any approach based on a glued optical connection. An alternative implementation of a muon detector includes a detector plane comprising an array of parallel, elongated scintillator sensor elements oriented along a given direction, with optical readouts at both ends. The arrival position of muons along the direction of each elongated scintillator sensor element is determined by comparing the collected scintillator light at both ends, either by comparing different signal amplitudes or arrival times at either end of the sensor element. The arrival position of muons in the direction perpendicular to the elongated scintillator sensor element is determined by the width of each elongated scintillator element.In other implementations, and with reference to Figure 9, the scintillator 900 includes a plurality of elongated scintillator elements 901 arranged within a cylindrical housing 902 to fit into a suitable cylindrical housing (not shown) for deployment within a bore. Suitable configurations include those in which the elongated scintillator sensor elements have a double-sided optical readout and are arranged in an annular pattern and oriented parallel to the housing 902. Further implementations in which fiber optic collimators are used for the optical readout of each elongated scintillator element are particularly advantageous in a cylindrical detector because the use of thin, flexible optical fibers can achieve greater space savings. In some implementations, the cylindrical detector has a hollow core. The hollow core can house the readout and digitizing electronics. In other implementations, the hollow core is at least partially filled with an additional elongated sensor element, for example, a non-scintillator detector element such as a Cerenkov light detector. Cerenkov light detectors generate a signal only for ultrarelativistic charged particles traveling at superluminal speeds within their medium, such as most atmospheric muons traveling through water, and are insensitive to background radiation components, such as gamma rays and neutrons, which might otherwise leave an unwanted or spurious signal on scintillator sensor elements.As such, a muon event can be selected using a combination of scintillator and Cherenkov signals, resulting in significant background suppression against electronic noise and / or unwanted gamma-ray and neutron signals. Such a modality can be particularly useful in the MA / a / ZUZZ / UUOl zo cases where muon detector is installed at a shallow depth with the intention of focusing on the so-called hard or high-energy component of the atmospheric muon spectrum. Unlike scintillator light, which is produced by ionization effects within the scintillator material, the amount of Cherenkov light produced by an ultrarelativistic muon is proportional to the muon's energy. Consequently, the detected amount of Cherenkov light provides additional information about the energy of the incoming muon. Furthermore, for a given muon energy, the Cherenkov light is emitted at a fixed angle relative to the muon's trajectory. With this information, the angle at which the Cherenkov light is emitted can be reconstructed, which can yield further information about the muon's trajectory. This is typically done by reconstructing a ring of light emission with a segmented multichannel photodetector. Such a ring-imaging detector can also be used in an underground muon detector to, for example, collect the Cherenkov signal at multiple points around the Cerenkov radiating element. Water is a preferred Cerenkov radiator for atmospheric muons. In fact, in all the detector implementations listed above, water-based Cerenkov radiators can be used instead of liquid or plastic scintillator sensor elements. In still other configurations, and with reference to Figures 10A and 10B, each detector plane in the muon detector can be implemented using an arrangement of a primarily cubic or Cherenkov scintillator element used to form a pixel detector. Figure 10A shows one configuration of a 1000-pixel detector that includes a pixel array 1001a, 1001b, 1001c, 1001d, 1001e, 1001f, 1001g (note that the interior pixels of the pixel array are unlabeled). The pixel array can be viewed through a readout window (not shown). In another variation shown in Figure 10B, the channels are filled with a liquid scintillator. In Figure 10B, the liquid scintillator 1010 includes at least one chamber 1011 filled with scintillator liquid 1012. When one or more atmospheric muons 1013 collide with the chamber 1011 and the scintillator liquid 1012, the scintillator liquid 1012 emits light 1014.The emitted light 1014 is collected by the optical collimation system 1015, which is coupled to one or more optical fibers 1016. The optical fibers 1016 transmit the light to one or more photodetectors (not shown) that produce an electrical signal indicating the passage of atmospheric muons. Two layers of pixel detectors can be used instead of cross-layers of elongated scintillator sensor elements with single- or double-sided optical readout. Typical scintillator elements in a pixel detector can have a width of approximately 5 mm to approximately 50 mm, a depth of approximately 5 mm to approximately 50 mm, and a height of approximately 5 mm to approximately 15 mm. Gaseous charged particle detectors, including multi-wire chambers, gaseous electron multipliers (GEMs), time-projection chambers, or small-diameter Geiger or proportional tube arrays, may also be suitable as an alternative to scintillator detectors for the purpose of detecting and determining the trajectory direction of atmospheric and subterranean muons. After placing a muon tracking detector beneath a mine heap, stockpile, dam wall (including the wall of a retention pond), or open pit wall, directional measurement of atmospheric or subsurface muon flux can provide a map of the bulk density distribution of the volume under consideration, including areas of excess density due to water accumulation over time. This information can be used to provide advanced diagnostic information on the risk of slope failures or to optimize metal extraction through heap leaching or water reclamation processes. While muon detectors primarily measure bulk density, this information can be combined with a variety of other methods to better determine slope stability parameters, economic value, and leaching or dewatering processing times. Such additional data can come from gravity, EM, resistivity, or seismic surveys, borehole measurements (e.g., temperature, pressure density, resistivity, nuclear spectroscopy, etc.), and sampling data (cores, fluid collection, etc.). Slope failure is ultimately related to pore water pressure. Pore water pressure increases with water volume, which can be identified through excess density distribution analysis. A deep-reading geospatial monitor, such as the one described herein, can provide unique information on the presence of risk areas and be used to inform an early warning system to alert the operator of potential slope failures. The information gathered in this way can also be used to trace the movement of groundwater back to its source and thus design effective dewatering techniques and interventions. The information provided by muon density measurements can also be used to determine whether other dewatering techniques should be employed, including the location and depth of dewatering wells.In the case of a heap leach, the operator can adjust the irrigation program, including the flow, volume, and location of the irrigation lines, as appropriate, to minimize the risk of slope failure or to maximize metal recovery. The slope stability analysis described above can be used to determine safe operating zones for access by mining equipment and heavy machinery. MA / a / ZUZZ / UUOl zo When fluid volumes are too high, the risk increases that equipment will sink, at least partially, into the unconsolidated material, which can result in a significant loss of access and productive time. This problem can occur in leach pads, but it can also occur on exposed mine access roads, which are important in many mining operations, including open-pit mining. In the case of a leaching heap, deep-read geospatial information on the volume and location of the leaching agent at different points of the heap provided by muon detectors can also be used to better estimate the net present value (NPV) of the asset. The present description should not be limited to the particular embodiments described in this application, which are intended to illustrate various aspects. Many modifications and variations may be made without departing from its spirit and scope, as will be evident to those skilled in the art. Functionally equivalent methods and apparatus within the scope of the description, in addition to those listed herein, will be evident to those skilled in the art from the preceding descriptions. It is intended that such modifications and variations be within the scope of the appended claims. The present description is limited only by the terms of the appended claims, together with the full scope of equivalents to which those claims are entitled.It should be understood that this description is not limited to particular methods, reagents, compounds, compositions, or biological systems, which, of course, may vary. It should also be understood that the terminology used herein is intended solely to describe particular modalities and is not meant to be exhaustive. With regard to the use of any plural and / or singular term in this document, those skilled in the art may translate from plural to singular and / or from singular to plural as appropriate to the context and / or application. Various singular / plural permutations may be expressly stated in this document for the sake of clarity. Those skilled in the art will understand that, in general, the terms used herein, and especially in the appended claims (e.g., the bodies of the appended claims), are generally understood as "open" terms (e.g., the term "including" should be interpreted as "including, among others," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes, among others," etc.). While various compositions, methods, and devices are described in terms of "comprising" various components or steps (interpreted as "including, among others"), the compositions, methods, and devices may also "consist essentially of" or "comprising" the various components and steps, and such terminology should MA / a / ¿U¿¿ / UUO1 ¿or be interpreted as a definition of essentially closed groups. Those skilled in the technique will further understand that, if a specific number of an introduced claim recitation is intended, that intention will be explicitly stated in the claim and, in the absence of such recitation, that intention will not be present. For example, as an aid to understanding, the following appended claims may contain the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as meaning that the introduction of a claim mention by means of the indefinite articles "a" or "an" limits any particular claim containing such an introduced claim mention to modalities containing only one such mention, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (for example, "a" and / or "an" should be construed as "at least one" or "one or more"); the same applies to the use of definite articles to introduce claim recitations. Furthermore, even if a specific number of an introduced claim recitation is explicitly stated, those skilled in the art will recognize that such a recitation must be interpreted as at least the number stated (e.g., the simple recitation of "two recitations," without any other modifiers, means at least two recitations, or two or more recitations). Moreover, in those cases where a convention analogous to "at least one of A, B, and C, etc." is used, in general, such a construction is understood to mean that someone experienced in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include, among others, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those cases where a convention analogous to "at least one of A, B, or C, etc." is used...In general, this construction is understood to mean that someone skilled in the art would understand the convention (for example, "a system having at least one of A, B, or C" would include, among others, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). Those skilled in the art will further understand that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, claims, or figures, should be understood to include the possibilities of including one of the terms, any one of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A or "B," or "A and B." Furthermore, when the characteristics or aspects of the description are described in terms of Markush groups, experts in the technique will recognize that the description is also described in terms of any individual member or subgroup of members of the Markush group. As a person skilled in the art will understand, for all purposes, including providing a written description, all intervals described herein also encompass all possible subintervals and combinations thereof. Any enumerated interval can be readily recognized as sufficiently descriptive and allowing the same interval to be divided into at least equal halves, thirds, quarters, fifths, tenths, and so on. By way of non-exhaustive example, each interval discussed herein can easily be divided into a lower third, a middle third, an upper third, and so forth. As a person skilled in the art will also understand, all language such as "up to," "at least," and the like includes the recited number and refers to intervals that can be further divided into subintervals as discussed above.Finally, as someone skilled in the technique will understand, a range includes each individual member. Thus, for example, a group that has 1 to 3 devices refers to groups that have 1, 2, or 3 devices. Similarly, a group that has 1 to 5 devices refers to groups that have 1, 2, 3, 4, or 5 devices, and so on. Several of the features and functions described above, and others, or alternatives thereof, can be combined in many other different systems or applications. Technicians may subsequently develop various alternatives, modifications, variations, or improvements not currently foreseen or unforeseen, each of which is also intended to be encompassed by the described modalities.

Claims

NOVELTY OF THE INVENTION Having described the present invention as above, the following claims are considered novel and, therefore, are claimed as property: CLAIMS 1. A method for monitoring slope stability by determining the density of at least a portion of a pile by measuring the incidence of atmospheric muons, wherein the method comprises: associating one or more muon detectors with the pile by placing a muon detector within an upper lining material, placing a muon detector within a trench, borehole, tunnel, or pipe located beneath an impermeable lining, placing a muon detector within a trench, borehole, tunnel, or pipe located within a first portion of the pile, placing a muon detector within a trench, borehole, tunnel, or pipe that is horizontally displaced from the pile,placing a muon detector on the floor of a pit located between two or more heaps, placing a muon detector on a lateral surface of the heap, or a combination of the above locations, measuring an atmospheric muon incidence on one or more muon detectors, and determining the density of at least a portion of the heap by comparing the atmospheric muon incidence detected by one or more muon detectors with a known muon attenuation of the materials in the heap and a known muon flux at the earth's surface.

2. The method of claim 1, wherein comparing the incidence of atmospheric muons with a known attenuation of the materials in the heap includes one or more of: comparing the muon attenuation for a known density of an initial sample of the heap materials with the muon attenuation in the heap, comparing the muon attenuation in the heap measured over a prior time interval with the muon attenuation in the heap, comparing the muon attenuation of the process fluids with the measured incidence of atmospheric muons on one or more muon detectors, or comparing the muon attenuation in the heap with a known muon flux at the earth's surface, including a surface flux measured by a secondary detector.

3. The method of claim 2, wherein the initial sample of the heap materials is one or more of a sample of dry ore, a sample of pre-moistened ore or agglomerated ore.

4. The method of claim 2, wherein the initial sample of materials from the heap is measured from two or more different locations in the heap.

5. The method of claim 2, wherein the measured incidence of atmospheric muons is measured by detecting at least two muon trajectories that are oriented in different directions.

6. The method of claim 1, further comprising moving at least one muon detector.

7. The method of claim 1, wherein associating one or more muon detectors with the heap includes placing a muon detector within an upper coating material.

8. The method of claim 1, wherein associating one or more muon detectors with the heap includes placing a muon detector inside a trench, borehole, tunnel, or pipe that is under an impermeable lining or between the first part of the heap and a second part of the heap.

9. The method of claim 1, wherein the heap includes two or more leaching pad area modules.

10. The method of claim 1, wherein associating one or more muon detectors with the heap includes placing a muon detector inside a trench, borehole, tunnel, or pipe that is horizontally offset from the heap.

11. The method of claim 1, wherein the heap is a dam.

12. The method of claim 11, wherein associating one or more muon detectors includes placing at least one muon detector that is horizontally offset from the tip of the dam or placing at least one muon detector that is horizontally offset within the dam and below the materials retained by the dam.

13. The method of claim 1, wherein associating one or more muon detectors with the heap includes placing a muon detector on the floor of a pit that is located between two or more heaps.

14. The method of claim 1, wherein associating one or more muon detectors with the heap includes placing a muon detector on a lateral surface of the heap.

15. The method of claim 1, further comprising determining a fluid content of at least a portion of the heap by measuring, for the portion of the heap that includes unconsolidated material, a change in the apparent density of the unconsolidated material between an initial sample value and a current value.

16. A system for monitoring slope stability by determining the density of at least a portion of a heap by measuring the incidence of atmospheric muons, wherein the system comprises: one or more muon detectors associated with the heap by being located within an upper lining material, within a trench, borehole, tunnel, or pipe located beneath an impermeable lining, within a trench, borehole, tunnel, or pipe located within a first portion of the heap, within a trench, borehole, tunnel, or pipe horizontally offset from the heap, on the floor of a pit located between two or more heaps, on a lateral surface of the heap, or a combination of the above locations, wherein the system measures an incidence of atmospheric muons on one or more muon detectors,and wherein the system determines the density of at least a portion of the heap by comparing the incidence of atmospheric muons detected by one or more muon detectors with a known muon attenuation of the materials in the heap and a known muon flux at the Earth's surface.

17. The system of claim 16, wherein the heap includes two or more leaching platform area modules.

18. The system of claim 16, wherein one or more muon detectors associated with the heap are located within a trench, borehole, tunnel, or pipe that is horizontally offset from the heap.

19. The system of claim 16, wherein the heap is a dam.

20. The system of claim 19, wherein one or more muon detectors are associated with the dam by placing them horizontally offset from the pile outside the dam or by placing them inside the dam and below the materials retained by the dam.

21. The system of claim 16, wherein one or more muon detectors are associated with the heap by being placed on the floor of a pit that is located between two or more heaps.

22. The system of claim 16, wherein one or more muon detectors are associated with the heap by placing them on a lateral surface of the heap.

23. The system of claim 16, wherein the system further determines a fluid content of at least a portion of the heap by measuring, for the portion of the heap that includes unconsolidated material, a change in the apparent density of the unconsolidated material between an initial sample value and a current value.

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