PASSIVE TAILINGS COMPACTOR

Abstract

The Passive Tailings Compactor is a system of components for facilitating the continuous passive drainage and consolidation of fine-grained sediments in active and continuous deposition environments. The invention consists of a flotation device, an anchor mass, and a drainage conduit which acts as a tether between the flotation device and the anchor. The flotation device also serves to orient the drainage conduit horizontally. As water or sediment levels rise, the flotation device rotates, releasing drainage conduit wrapped around its axis. This allows the flotation device to move upwards, extending the drainage conduit passively. The flotation device uses asymmetrical fixed weights to resist lesser rotational forces. The drainage conduit serves to create a path of relatively high hydraulic conductivity, protected by a filter barrier, for the dissipation of pore pressures and consolidation of buried sediments. The anchor mass fixes the system in place.

Claims

1-6. (canceled)

7. A passive tailings compactor for installing and maintaining a vertical drainage pathway through tailings, comprising: a drainage conduit which serves to enable the flow of water from the tailings while filtering and excluding solid particles; an anchor attached to one end of the drainage conduit; and a flotation device attached to the other end of the drainage conduit having a central axis about which a length of the drainage conduit is wrapped; wherein the flotation device is asymmetrically weighted or shaped to resist rotation.

8. The passive tailings compactor of claim 7, wherein the relative net buoyancy of the flotation device is less than that of water, but higher than that of the tailings, thereby allowing the flotation device to remain submerged in water and still rest above the tailings.

9. The passive tailings compactor of claim 7, wherein the drainage conduit is a coarse rope material core wrapped with a geotextile filter cloth sheath.

10. The passive tailings compactor of claim 7, wherein the drainage conduit is a coarse rope material core wrapped with a sheath of tightly woven, fine nylon strands.

11. The passive tailings compactor of claim 7, wherein the drainage conduit is a pre-fabricated vertical wick drain.

12. The passive tailings compactor of claim 7, wherein the drainage conduit is a perforated tube core wrapped with a geotextile filter cloth sheath.

13. The passive tailings compactor of claim 7, wherein the drainage conduit is a perforated tube core wrapped with a sheath of tightly woven, fine nylon strands.

14. The passive tailings compactor of claim 7, wherein the anchor is a frictional stake.

15. The passive tailings compactor of claim 7, wherein the anchor is a plate having a large cross-sectional area.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1: Isometric view of passive tailings compactor system in operation with a cut-away showing the asymmetrical mass contained within the flotation device.

[0016] FIG. 2: Detailed cross section of an example drainage conduit's components and function

[0017] FIG. 3: Front plan view of passive tailings compactor system with half displayed as a cross section (object is symmetrical)

[0018] FIG. 4: Side view showing passive tailings compactor system floating on supernatant water above multiple layers of deposited mineral sediments (tailings) being drained and compressed. Two different sections are displayed: the asymmetrical mass inside of the flotation device, which generates a torque resisting the unwinding of drainage conduit from the flotation device spool, and a section through the spindle showing the drainage conduit wrapped for storage.

BEST MODE FOR CARRYING OUT INVENTION

[0019] A system of components which facilitates the continuous release of trapped interstitial water from fine-grained sediments being actively deposited 16 in a containment facility (tailings storage facility) by creating a network of vertical drainage pathways in the sediment materials which are continuously extended upwards in tandem with pond or sediment elevation increases, connecting the surface or supernatant pond to all sediment horizons via a drainage pathway of relatively high hydraulic conductivity. The invention allows for the benefits of sediment consolidation and dewatering to be realized during the continued operation of a facility, and not only after the facility has completed operations and is preparing for remediation. The system is comprised of three primary components: a flotation device, an anchor mass, and a drainage conduit connecting the previous two components. The system extends upwards passively as the depth of sediment and or water increases. A description of each component and its purpose is provided: [0020] a. Anchor Mass: A weight of high specific gravity or cross-sectional area which provides an anchor to the system, holding the base of the drainage conduit 5 fixed in location in three dimensions. This weight would be heavy and sharply shaped 6 to penetrate existing soft or unconsolidated sediments in operating facilities, facilitating the extension of the drainage system into previously-deposited sediments. It can also be lighter and shaped to provide a large cross-sectional area which would resist being pulled through fine sediments, effectively anchoring the system with less anchor material 15. [0021] b. Flotation Device: A device which serves firstly to allow for the passive vertical extension of the passive tailings compactor system (by floating on top of supernatant water 7 or sediments 8), secondly to vertically orient the system, and thirdly to store drainage conduit 5 required for future vertical extensions of the system. Maintaining the shortest possible distance from anchor to floatation device is an important function of the flotation device, as it allows for dense networks of these passive tailings compactor systems to be place closely together without tangling. The flotation device would be of similar shape and design specifications to the marker buoy for fishing and navigational purposes described by Rovner in U.S. Pat. No. 3,653,085-A granted on May 7, 1970. Specific functionalities and characteristics include: [0022] i. The flotation device is essentially a spool constructed in a shape which results in high relative buoyancy (by creating hollow air pockets 3) or of a material which is inherently buoyant in water and/or mineral sediments. The flotation device is required to have a high chemical stability in water, under continuous exposure to sunlight, and potentially in harsh and unique chemical environments for long time periods (years). A suitable material could be cast high-density polyethylene plastic 1 shaped to create trapped air pockets 3 that increase the buoyancy of the device. Materials and size for this component could be modified for each unique environment. [0023] ii. The flotation device serves as a spool around its central axis 4. Drainage conduit 5 is wrapped around this spool for storage prior to being deployed. The flotation device rotates around this axis as the device's high relative buoyancy (as compared to water or mineral sediments) results in upward movement and a rotational force on the device caused by the anchor component and connected drainage conduit generating a torque around the axis of the spool 4. In this manner the drainage conduit is extended upwards as sediment 8 or water 7 levels, through continued deposition of sediment slurries 16, increase in elevation and the flotation device rotates around its central axis releasing more drainage conduit. [0024] iii. The flotation device 1 is round and smooth in the dimension perpendicular to the rotational axis in order to reduce frictional forces which might resist the rotation of the device around its central axis. This allows the flotation device to rotate more easily when sitting upon water or high-friction mineral sediments/slurries 8, ensuring the effective extension of the drainage conduit 5. [0025] iv. The flotation device 1 is asymmetrically weighted with two attached masses 2 with high specific gravity to ensure that extension of the drainage system occurs only as a result of water or sediment elevation increases, and not due to other environmental forces such as wind. The flotation device has a dense mass attached 2 as far from the rotational center of mass as practical. The mass can be cast into the body of the flotation device or connected using other means such as rivets or bolts. This mass creates a moment arm, or torque around the rotational axis which serves to resist the rotation of the flotation device from its resting position where the asymmetrical masses occupy the lowest portion of the flotation device relative to the water level. Only an opposed rotational force of greater magnitude can cause the device to rotate, releasing drainage conduit. The size of this counter-rotational force (controlled by the mass of the asymmetrical weighting and its distance from the rotational axis) is designed to allow rotation due to the buoyant force generated by the flotation device, but not due to other forces of lesser magnitude such as wind-induced rotational forces. [0026] c. Drainage Conduit: a rope or similar tether system 5 with favorable hydrological characteristics that is connected at one end to the system anchor 6, and at the other wrapped around and connected at its end to the flotation device 1. The conduit must provide a path of lower hydraulic conductivity for water to flow along its length 10, from areas of relatively high pressure toward areas of relatively lower pressures. The drainage conduit must also be designed and constructed such that it incorporates a filter barrier 14, or is by its nature a filter barrier, which prevents fine mineral particles 12 from entering the drainage conduit. These particles could block the drainage conduit impacting its ability to serve as a low-resistance drainage pathway. When meeting these criteria, the drainage conduit can serve the purpose of accelerating the drainage of trapped interstitial water 9 by allowing it to flow into the drainage conduit where it can report to surface or another area of relatively lower pressure 11. This allows for the consolidation of said sediments 12 by removing some of the water volume between mineral particles. Drainage conduit 5 can be comprised of a variety of different material types and physical structures and sizes to provide optimal characteristics in different material types and environmental conditions. A drainage conduit could be comprised of different combinations of fibrous materials that exhibit the following properties: [0027] i. A core comprised of a material with significant cross-sectional voids which provides continuous drainage pathways along the conduit. This core would provide tensile strength to the conduit 13. Void space required would be a function of desired dewatering flow rates. [0028] ii. A sheath comprised of fine strands of tightly woven fibers, or similar filter cloth materials wrapped around the core. This sheath serves as a filter barrier, allowing water to access the drainage conduit, but blocking fine mineral sediments which could potentially cause the conduit to become blocked, reducing the hydraulic conductivity of the conduit 14. [0029] iii. Be supple enough to be rolled around the flotation device spool for long duration without developing weakness or excessive memory. [0030] iv. Be resistant to environmental stresses such as moisture, friction, sunlight, freezing, heat, and chemically inhospitable environments such as acidic or basic conditions. An example of a suitable drainage conduit material is a pre-fabricated vertical wick drain, as is currently commercially available, and described in U.S. Pat. No. 4,622,138A and U.S. Pat. No. 5,820,296A. These drains are comprised of a semi-rigid core which creates a void space for water to flow through. This core is wrapped by a geotextile material which serves as the filter barrier as described previously. In current commercial use, these drains are installed from the surface downwards by heavy equipment (either pushing or drilling them downwards). In the passive tailings compactor, these drains would simply be employed as the drainage conduit/tether 5 which unwraps from a spool and extends upward with basin elevation.

REFERENCE LIST FOR DRAWINGS

[0031] 1. Flotation device [0032] 2. Asymmetrical weight [0033] 3. Air gap [0034] 4. Spool spindle [0035] 5. Drainage conduit [0036] 6. Anchor mass [0037] 7. Supernatant water surface [0038] 8. Mineral sediment surface [0039] 9. Pore water flow path in mineral sediments [0040] 10. Pore water flow path in drainage conduit [0041] 11. Pore water discharging from drainage conduit into supernatant pond or open atmosphere [0042] 12. Mineral particle [0043] 13. Core of drainage conduit [0044] 14. Filter barrier of drainage conduit [0045] 15. Flat anchor plate