SOFTWALL MINING METHOD AND DEVICE

Abstract: Disclosed is a method and device for mining slurryable minerals where the overburden (50) is unstable and subject to collapse when undercut. More or less parallel elongated trenches (60) are formed to the bottom of the mineral seam and connected by a perpendicular trench (66). A plurality of softwall mining devices (20), supported by face equipment (22) are placed in the perpendicular trench. The devices slurry the mineral material and move into the mineral seam (56). Overburden sloughs behind the mining devices. The subsided overburden (54) is supplemented as necessary with injected material. Slurried mineral flows to the parallel trenches (60) for removal to the surface. After the softwall devices have advanced the length of the parallel trenches (60), the devices are withdrawn and placed in additionally developed trenches elsewhere in the ore reserve.

Description: SOFTWALL MINING METHOD AND DEVICE FIELD OF THE INVENTION This invention pertains in general to the field of mining and, in particular to a novel device and method for mining slurryable, shallow mineral deposits with earthy overburden in a longwall fashion. DESCRIPTION OF RELATED ART Surface mining is and has historically been employed to recover stratified minerals under overburden to economic depths. Underground mining is traditionally employed when overburden depths exceed those economically removable by surface mining or when major surface disturbance is unacceptable. Prior inventions have been patented for longwall mining of reserves using trenched entry where overburden is sufficiently competent to bridge over longwall shearing and conveying equipment and where floor strata are competent to withstand mining stresses. (See Simpson 4,017,122.) Simpson does not accommodate soft, plastic, fluid, loose, unstable, clayey, sandy, dirt, soil, or similar (earthy) ground conditions often encountered in mining shallow ore deposits. Earthy conditions can allow the mine roof to fall ahead of shield supports or allow the floor to heave up behind the face conveyor ahead of the shield pontoons. This creates safety hazards, dilution of ores, and expensive control installation. The present invention provides a means for mining slurryable ore reserves where overburden is earthy. Floor conditions are also reduced to being an insignificant issue. BRIEF SUMMARY OF THE INVENTION The idea of adapting longwall mining equipment and methods to recover ore from slurryable deposits with earthy overburden is novel. The term "softwall" is a new term applicable to this type of mining. In particular, the subject invention is directed at phosphate matrix mining. A plurality of elongated, substantially parallel, mains trenches extend the full length of area to be mined. The trenches are nominally 1,000 feet apart. Heading trenches substantially perpendicular to the main panel trenches are excavated for placement and removal of the mining equipment. The trenches are formed by excavating the overburden materials to the top surface of the mineral bed. The mineral bed in the trench is separately excavated and beneficially recovered. Trench side wall slopes are as steep as is geologically reasonable and safe to minimize excavation. Forming a header trench leaves an exposed longwall. The softwall mining equipment is installed in the header trench. The phosphate is then mined, for example, by slurrying the ore as the mining equipment moves in a direction generally parallel to the main panel trenches. The slurried ore flows into the main panel trenches where it is removed to the surface for processing. The softwall mining equipment includes an outer shell to support the overburden stresses. Forward motion is created by extending a cutting head into the ore reserve and retracting said head in such a manner as to pull the outer shell forward. Unsupported overburden behind the outer shell is encouraged to fill the cavity. Where backfilling is used, materials are injected through the outer shell. Operation of the softwall equipment and backfilling is performed automatically from controls in the trench or on the surface. When softwall mining equipment has traveled a predetermined distance to the next header trench, the equipment is removed and placed in another header trench for mining additional ore. Trenches not scheduled for further use would be reclaimed. Alternatively, the equipment can be repositioned at the exit header and again advanced in the opposite direction to mine the next lower level of the ore seam. Another alternative would be to utilize several sets of softwall mining equipment in a seam thicker than one set of equipment can mine. The uppermost level would be mined first. Adjacent lower levels would be mined with predetermined horizontal separation distances between sets of equipment. Yet another alternative, where ore can be slumped, is to position the softwall mining equipment at or near the bottom of the ore seam. With or without forward injection of fluids into the ore seam, the slurried ore would slump into the softwall mining equipment and move into the main panel trenches. Instead of using parallel main panel trenches and a common header trench, a single mains trench can be used with a header constructed in a "T" manner. One set of softwall mining equipment would be placed in each header branch of the "T" with slurried ore feed to the trunk main panel trenc . The equipment can also operate in a spiral fashion following main panel trenches constructed to curl in a continuous pattern through the ore reserve. OBJECTS AND ADVANTAGES Besides the objects and advantages of the softwall mining device described above in this patent, several objects and advantages of the present invention are: a. to provide a more economical means of mining slurryable ores; b. to provide a means of removing ares by longwall methods under earthy overburden: c. to provide a means of longwall mining without use of panel development and outbye roof support; d. to provide an alternative means of mining sticky clay ore; and, e. to provide a means of mining material varying from solid to liquid phases without special concern for the phase. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows an orthographic of a softwall mining device. Figure 2 shows a plan or top view of a softwall mining device. Figure 3 shows an end view of a softwall mining device. Figure 4 shows a more detailed end view of the cutting head or face sluicing chamber. Figure 5 shows a plurality of softwall mining devices connected with a tensioning cable. Figures 6, 7 , and 8 show cooperative action of a plurality of softwall mining devices working together. Figure 9 shows employment of a softwall mining device in an ore body thicker than the device height. Figure 10 shows use of a plurality of softwall mining devices with two parallel mains trenches and a perpendicular header trench. Figure 11 shows a plurality of softwall mining 5 devices using an alternative "T" trench configuratio . REFERENCE NUMERALS IN DRAWINGS 20 Face Sluicing Chamber (FSC) 10 21 Pressurized Water Supply Lines and Electrical Controls 22 Rear and Roof Bearing Support (RBS) 23 Overlapping Seal 24 Extension Ram 15 25 Extension and Support Guide Bearing Assembly 26 Extension Guides 27 RBS Overlapping Side Covers 28 Extension and Support Assembly 29 Softwall System Control Line 20 30 Support Braces 31 Rear Injector 32 Pressurized Injection Nozzles 33 Softwall System Control Line Alignment Hole 34 Water Injection Control Unit 25 35 Cutting Edge Injection Nozzles 36 Vertical Rotating Guide 37 Rigid Support Post 38 Vertical Rotating Ram 39 FSC Seal 30 40 Penetrating Edge Orifice 41 Elongated Slot 42 Inner Plate Water Conduit 44 Surface Compaction Equipment 50 Original Overburden Surface 35 52 Subsided Surface 54 Subsided Earthy Overburden 56 Ore Matrix Mining Face 57 Ore Matrix 58 Closed End of FSC 59 Panel Width 60 Trench Excavation Development 61 FSC Advance Sequence 62 Trench Gate Slurry Handling Equipment 63 Direction of Mining Advance 64 Constant Tensioning Device 65 Flow Direction of Slurried Ore 66 Header Trench 68 Multiple Lift Mining Sequence DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION A typical embodiment of softwall mining equipment is illustrated in Figures 1 through 4. Figure 1 is an isometric schematic of a softwall mining device, the object of the invention. A device consists of a Face Sluicing Chamber (FSC) 20 partially enclosed within a Rear and Roof Bearing Support (RBS) 22. The function of the device is to remove ore matrix away from the ore face. This is accomplished by the forward extension of FSC 20 from within RBS 22 by means of the actuation of Extension Ram 24. Forward movement is enhanced by the action of a plurality of Cutting Edge Injection Nozzles 36 mounted on FSC 20 as shown in Figure 4. Elongated Slots 41 are provided to movably join the tongue and grooved edges of FSC 20 together with other softwall mining devices. Rigidly mounted on RBS 22, Extension Guides 26 provides directional thrust control for device forward movement. A plurality of rigidly mounted Support Braces 30 provide vertical strength to FSC 20. A retractable and extendable Vertical Rotating Ram 38, pivotally mounted to both FSC 20 and Extension and Support Assembly 28, provides vertical movement control. A plurality of Rear Injectors 31 extend through RBS 22 to apply fluids into the collapsed overburden. Figure 2 shows a softwall mining device in plan view. Extension and retraction of FSC 20 from RBS 22 is provided by Extension Ram 24 attached fixedly to RBS 22 and pivotally to Extension and Support Assembly 28. An Extension and Support Assembly 28 is attached slidingly to both Extension Guides 26 by means of a plurality of Extension and Support Guide Bearing Assemblies 25 and directly to Vertical Rotating Guide 38. A plurality of Pressurized Water Supply Lines and Electrical Controls 21 and Water Injection Control Unit 34s are attached to FSC 20 to provide control of injection fluid pressure and volume. A plurality of Pressurized Injection Nozzles 32 fed from Water Injection Control Unit 34 are mounted on FSC 20 to supply fluid injection within the enclosure of FSC 20. Figure 3 is a schematic representation of the cross section of the mining equipment. The leading edge of a RBS 22 is typically beveled to reduce forward resistance. A Vertical Rotating Guide 38 is fixedly connected more or less vertically to the rear portion of FSC 20. A Rigid Support Post 37 is rigidly mounted to the floor and roof of RBS 22 for strengthening the device. A Softwall System Control Line Alignment Hole 33 is provided in Extension Guides 28. RBS Overlapping Side Covers 27 are rigidly connected to RBS 22 to reduce the likelihood of foreign materials entering the device when used in combination with other softwall mining devices. Figure 4 shows a more detailed end view of FSC 20. Pressurized injection fluid is delivered to a plurality of Water Injection Control Unit 34s through a series of Pressurized Water Supply Lines and Electrical Controls 21. The Water Injection Control Unit 34s are mounted on the outside surface of FSC 20 and distribute pressurized injection fluids to the respective nozzles Pressurized Injection Nozzles 32 inside FSC 20. A plurality of Pressurized Injection Nozzles 32 are mounted inside FSC 20 to inject fluids into the ore to break ore from its insitu condition and create a slurry. A FSC 20 is machined with a channel Inner Plate Water Conduit 42 to provide a conduit for injection fluids to travel from Water Injection Control Unit 34 to Penetrating Edge Orifice 40 where the fluids are injected through multiple Cutting Edge Injection Nozzles 35. The Cutting Edge Injection Nozzles 35 are mounted rigidly on the leading edge of a FSC 20 to inject fluids into the ore matrix to aid in penetration. A FSC Seal 39 provides a seat to prevent external materials from entering the RBS 22 enclosure. Figure 5 shows a plurality of softwall mining devices connected with a Softwall System Control Line 29 through Softwall System Control Line Alignment Holes 33. At the device most upstream in the slurry flow a Softwall System Control Line 29 is secured with a Constant Tensioning Device 64 flexibly attached to the most upstream device. Adjoining devices are provided with Overlapping Seal 23 and 39 to minimize leakage of foreign materials into the devices . Figures 6 through 8 refer to the operation of the softwall mining devices. There are a number of ways the devices of the invention can be operated. The following illustrations are not meant to be exhaustive but rather to illustrate only some of the possible ways and sequences in which it can be used to recover ore slurry material. Figure 6 is a schematic representation in plan view of the first step in operation of the softwall mining devices. Said devices are assembled along Ore Matrix Mining Face 58 with full retraction of FSCs 20 in preparation for an extension push against Subsided Earthy Overburden 54 into Ore Matrix Mining Face 56. A Surface Compaction Equipment 44 could be used on the surface for additional overburden compaction. Figure 7 is a schematic representation in plan view of a possible second step in the operation of devices showing an FSC Advance Sequence 61 of FSC 20 against the uniform alignment of adjacent RBSs 22 bearing against Subsided Earthy Overburden 54. Figure 8 is a schematic representation showing a third step in operation of softwall mining devices in plan view. In this step, the rear bearing support units RBS 22 are retracted in a sequence shown in the respective boxes Direction of Mining Advance 63 causing subsidence of the Subsided Earthy Overburden 54 behind the devices. The cycling of the 3 steps will occur in batches and groups of devices at various points along the mining face such that all three steps are simultaneous at different positions along the face. The 3 steps to the mining cycle are repeated to provide uninterrupted mining and flow of ore from the mining face. Figure 9 shows Multiple Lift Mining Sequence 68 with a softwall mining device or a set of devices in an ore body thicker than the device height. Subsidence of the Original Overburden Surface 50 will occur in stair step fashion producing Subsided Surface 52 as Ore Matrix 57 is removed. Figure 10 shows use of a plurality of softwall mining devices with two parallel mains trenches 60 and a perpendicular Header Trench 66 extending the full distance of the Panel Width 59. A plurality of adjacent softwall mining devices progresses more or less parallel to Ore Matrix Mining Face 56. A Closed End of FSC 58 divides Header Trench 66 forcing slurried ore to follow Flow Direction of Slurried Ore 65. Slurried ore is collected for transport and processing by Trench Gate Slurry Handling Equipment 62 at each mains trench. Figure 11 shows use of a plurality of softwall mining devices using an alternative "T" trench configuration with two Header Trenches 68 feeding into one mains Trench Excavation Development 60.

Claims: CLAIMS 1. A device for mining minerals comprising: a. a weight-bearing shell; b. a movable chamber; and c. means for extending and retracting said chamber relative to said shell; whereby ore can be recovered from under earthy overburden. 2. A device for mining minerals as recited in claim 1, further comprising a means for injecting fluids from forward edges of said chamber to enhance forward movement of said device. 3. A device far mining minerals as recited in claim 2, wherein said means for injecting fluids from forward edges of said chamber include nozzles. 4. A device for mining minerals as recited in claim 1, further comprising a means for injecting fluids inside said chamber to slurry ore. 5. A device for mining minerals as recited in claim 4 wherein said means for injecting fluids inside said chamber to slurry ore include angularly mounted nozzles. 6. A device for mining minerals as recited in claim 1, wherein said chamber is pivotally joined to said shell to provide directional cutting and movement of said device. 7. A device for mining minerals as recited in claim 1, wherein said chamber contains an auger to promote evacuation of slurried ore from said device. 8. A device for mining minerals as recited in claim 1, further comprising rear mounted injectors for dispensing materials into collapsed overburden. 9. A method of mining minerals from a thick seam of slurryable ore located under earthy overburden comprising the following steps: a. Forming an elongated first trench of a first predetermined width to a depth substantially equal to the bottom of the seam; b. Forming a second elongated trench of second predetermined width substantially perpendicular to and at one end of said first trench to form a softwall face: c. Providing a plurality of softwall mining devices in said second trench; and d. Advancing said softwall mining devices in a direction generally parallel to said first trench to mine said seam. 10. A method according to claim 9: a. wherein mining is accomplished by advancing a plurality of said softwall mining devices set at varying heights in said seam; such that i. a first set of said softwall mining devices is set to slurry ore from the top of said seam to the base of the first of said softwall mining devices; ii. a second set of said softwall mining devices is set to slurry ore from the base of the first set of said softwall mining devices to the base of the second of said softwall mining devices; and ii. other sets of softwall mining devices are set to slurry ore from the base of the immediately higher set of said softwall mining devices to the base of the previous pass, until the reserve is mined to a predetermined extent. 11. A method according to claim 10, wherein: a. a set of softwall mining devices is set to slurry ore from the top of said seam; b. said set of softwall mining devices proceeds a predetermined distance through said seam; c. said set of softwall mining devices is removed and placed at the new top of said seam; d. said set of softwall mining devices proceeds a predetermined distance through said seam; and e. said set of softwall mining devices continues to be removed and replaced into said seam until a predetermined amount of said seam is removed. 12. A method according to claim 9, wherein mining is down dip to provide drainage of natural or mining waste water. 13. A method according to claim 9, wherein an end of said second trench is at an end of said first trench; and a third elongated trench is formed substantially parallel to said first trench and at the end of said second trench not connected to said first trench to provide egress of slurried mined mineral into either or both said first and third trenches. 14. A method according to claim 9, wherein a support facility is located on overburden surface to provide liquid for injection into the mined out area to promote more complete subsidence. 15. A method according to claim 9, wherein a support facility is located on overburden surface to provide ore slurry removal from said first trench at or near the end of said second trench.

Inventors: PETERSON RANDALL D, PETERSON, RANDALL, D.
Applicants: IMC AGRICO CO, IMC-AGRICO COMPANY
Application year: 1998
Main classification: E21C41
IPC codes: E21C25, E21C41