MINING SUBSIDENCE
RECLAMATION CONSULTANTS

NORM TRIBE P.ENG.---&---L.J. (JOHN) TRIBE P.ENG.


INTRODUCTION

RECLAMATION OF MINE SUBSIDENCE



    · Old mine openings present hazards to the public

    · Liabilities to the property owners.



OUR PRODUCT



    · A method of plugging
      - Mine shafts
      - Ventilation raises
      - Mine cave subsidence.

    · Meets the Ministry of Energy and Mines requirements
    · Has not failed in over 280 reclamation sites.
    . Our method is adaptable to the installation of bat access gates where required.


PROCEDURE



    · A flexible, expandable, plug is used to stabilize the subsidence.
    · Modern geotechnical methods are used to seal the hole and stabilize the ground.
    . 4' to 8' CSP culvert pipe can be fitted into the plug with 6.5" X 24" steel grating for bat access.



METHOD



  • Preparation

      · Old fill and cave material is removed from the opening to the point where the opening is defined.
      · Top soil is pulled back and stockpiled for later use.
      · The ground around an area of subsidence is nearly always unstable.
      · The rock around these cave-ins is usually still moving as the rock adjusts to the removal of the ore.

  • The Plug

      · The plug must be designed to accommodate this movement and provide structural support.
      · A dynamic, expandable, flexible plug is required that expands to fill the hole.
      · Recycled open pit mine equipment tires provide the expandability and the support.
      · A variety of tires is needed as mine openings come in various sizes.
      . If bat access is required the CSP with bat gate is positioned first and the plug is fitted around it.
      · It is necessary to adapt the use of the recycled tires to the size of the hole.
      · Many of the openings can be successfully plugged by arranging the tires in a stack of four to six tires, cabled together with galvanized 5/16th inch steel cable.
      · The tires are compressed by the excavator and forced into the hole.
      · The compressed stack is allowed to expand to fill the hole.
      · A layer of material is placed above the plug to create a platform.
      · With the throat of the hole now stabilized, an area around the hole can be cleared to allow room for the matte which is bigger than the hole by about half again. This is to allow for hitches in the solid country rock.
      · As this larger area is cleared more topsoil is added to the stockpile for later use.

  • The Matte

      · The next layer is referred to as the matte. The matte is made up of a number of highway truck tires linked together by cable and is sufficient large to cover the area of subsidence and a minimum of one meter onto stable rock on all sides.


  • The Mesh

      · The mesh is a commercial geotextile material used universally to stabilize difficult ground conditions and is placed so that it completely covers the matte.


  • The Cloth

      · The next layer is a commercial geotextile material referred to as cloth and is placed so that it covers the mesh.

  • The Final Step, Backfill, Recontouring and Reseeding.

      - The next layer is composed of gravel or broken rock or what ever material is available and is applied to a depth of at least one meter over the patch.
      - The contour of the final reclamation is established with drainage leading surface water away from the hole and diverting any flow of water which may be directed toward the opening.
      - The final layer is topsoil which was salvaged earlier.
      - The final step is the reintroduction of suitable vegetation.



COSTS


  • The cost of the method outlined here is one of the more attractive aspects to an otherwise rather ugly situation.
  • Costs vary tremendously depending on the location of the hole, the size of the hole, accessibility of the hole and proximity to towns etc.
  • For the average of over 200 sites reclaimed to date, the costs per site is under $5,000 per hole.



RESULTS

  • To date over 200 holes have been repaired, many between occupied homes in the Bellevue, Blairmore, Coleman and Canmore areas of Alberta, and many more within the city limits of these towns, adjacent to schools, within areas frequented by children, as well as near to trails used by dirt-bikers, skidooers and hikers who frequent the neighboring hills adjacent to these towns. This method has proven to be successful in all cases to date. In no case has the plug shifted or the integrity of the reclamation been lost.



PHOTO ESSAY


  • Adanac Portal Site
      The Adanac Portal is easily accessible in summer or winter as the access road is an old rail grade and is only 100 meters off a well traveled forestry road. The portal had previously been blocked using old mine cars scrap timber and soil.
      Over time the material had settled and left the portal accessible to anyone curious enough to squeeze the opening.
      This portal was the main haulage for the Adanac Mine, and the whole of the mine drains through this opening. Build up of water must be avoided in these situations as drainage for the mine workings was designed into the plug.




    At some time in the past the portal was closed by pushing whatever was handy into the opening. The hole in the upper right had been entered by various curious people.




    Cleaning the portal showed that a thick steel door closed off one side of the entry but the other side was open.




    The plug was constructed adjacent to the portal. The unit was pre-stressed in order to provide structural integrity while the plug was being placed.




    The plug was placed next to the steel door to complete the closure of the portal.




    Geotextile mesh then geotextile cloth is spread over the plug to eliminate the movement of fines.
    Not shown - drainage was installed to allow the drainage of mine water from behind the plug.




    The final sloping resembles the original closure except that reopening an access to the underground has been stopped. Reopening the adit will require a bigger hoe than was used to close it.



  • Adanac Mine Crater

      The Adanac mine workings developed into some of the most spectacular subsidence craters in the entire region. The crater shown here was more than 30 meters (100 feet) across. There is a well used forestry access road nearby used regularly by dirt bikers skidooers and hikers.
      The major challenge in this repair was gaining safe access to the throat of the subsidence so that the plug could be positioned correctly. The backhoe first had to bench up to scale the crater wall, then bench down to position the plug.



    This opening lead to the underground workings and the surface crater was over 30 meters (100 feet) across.




    This photo shows half of the plug that was eventually used to secure the throat of the opening.




    This plug required 12 - CAT 992 loader tires to seal the opening.




    Scaling was initially done for safety reasons. Now the slope is being further reduced to enhance the stability of the feature.




    The tire matte is 5 meters by 8 meters (16 X 25 feet) to ensure that the throat of the opening is covered.




    Geotextile mesh then geotextile cloth is spread over the matte to eliminate the movement of fines.




    Final contouring is done to direct the drainage away from the site, slope the edges and make the area safe. Seeding of indigenous ground cover completes the reclamation.





  • Slot Mine Subsidence

    The slot was formed where a coal seam was mined through, to just below the surface then later subsided, leaving a large slotted opening of undetermined depth. Several of these features were repaired, some over 100 meters (330 feet) in length. Several stacks of large loader tires were used to plug the opening. This was followed up with a tire matte, geotextile mesh, geotextile cloth, backfilling, recontouring, drainage control and reseeding.




    The slot has opened up to expose underground workings




    Several stacks of tires were compressed and inserted into the opening to form the plug.




    A matte of tires is linked together to form a protective barrier and support the mesh and cloth.




    The geotextile mesh is laid over the matte to support the cloth.




    The geotextile cloth is applied over the mesh to support the fines and soil.




    The site is back-filled and recontoured to direct drainage away from the hole and reseeded with indigenous ground cover.




    The site is revisited one year later. The ground cover is well established and the repair is in excellent condition and the environment is well on its way to recovery.





  • Bellvue School Overhanging
    Slot Mine Subsidence

    The slot was formed where a coal seam was mined through to just below the surface. The underground opening then later subsided, leaving a large slotted opening of undetermined depth. This particular one was less than 100 meters behind the Bellview School. There was ample evidence of children playing in these openings and rehabilitation was undertaken to make it safe. Many stacks of large loader tires were used to plug the opening. This was followed up with a tire matte, geotextile mesh, geotextile cloth, backfilling, recontouring, drainage control and reseeding.




    The slot has opened up to expose underground workings.



    The opening into the mine was of undetermined depth.



    Numerous stacks of loader tires were assembled to plug the opening.



    The tires were oriented in such a way as to provide the best seal.



    The tire plug seals off the opening. The tires are forced into place. The rubber expands to make a tight seal. These tires will remain elastic and resilient for hundreds of years when kept away from U.V. light.



    A matte of tires is linked together to form a protective barrier and support the mesh and cloth.



    A heavy duty geotextile cloth is applied over the geotextile mesh.



    The site is then recontoured with drainage directed away from the opening. Seeding is done with local native seed mix and the rehabilitation is complete.



    One year later the site is revisited to find the vegetation well established and the rehabilitation work intact.







  • Bluebell Upper Glory Hole Closure

    The glory hole is the result of the high grade silver ore of the Bluebell Mine being mined through to surface. Years of dumping waste material into this opening has created an unattractive dump as well as a hazard to the childern of Riondel who live within 100 meters of this feature. The opening measures 11 meters by 4 meters and the depth is several thousands of feet deep. The kids of the village have used this opening for a playground for years. Eleven, 240 tonne mine truck tires were used to plug the opening. The tire diameter was approximately 0.4 to 0.6 meters large than the opening thus optimizing the positioning of the rank of tires to make a tight fit. This was followed up with a tire matte, geotextile mesh, geotextile cloth, backfilling, recontouring, drainage control and reseeding. Adjacent to this opening was a 1.4 X 2.0 m subdrift open to the surface. Environmentalists requested that an opening be left as a bat entry to provide access to the underground for the local bats and still deny access to the local kids. The bat entry was designed to be 8" x 24 ", large enough for a bat to fly into but too small for a kid to climb in.




    This adit was designated as a bat entry.



    The opening into the mine was 11 meters by 4.0 meters high and filled with scrap material wood and iron.



    The large mine haulage truck tires are a perfect fit.



    The tires were oriented in such a way as to provide the best seal. This opening required 11 tires standing vertically.



    Loader tires make a nice fit for the bat access opening as is demonstrated by the workers hand.



    A large matte of over 150 tires is linked together to form a protective barrier and support the mesh and cloth.



    A heavy duty geotextile mesh is applied over the tire matte.



    A heavy duty geotextile cloth is applied over the mesh. Care is taken to ensure a good seal against the overhang.



    A site is then backfilled pushing the fill against the hangingwall to provide a good seal.



    Recontouring the site nears completion. The Bat Cave entry is visible in the background, just above the excavator bucket. Positive drainage directs water away from the opening. Seeding is done with local native seed mix and the rehabilitation is complete.





    LINKS AND ADDRESSES


    • HOME PAGE for
      N. TRIBE & ASSOCIATES LTD. (Click below)




    • eMAIL ADDRESS FOR NORM TRIBE P.ENG.
    • norm@nltribe.com

    • eMAIL ADDRESS FOR JOHN TRIBE P.ENG.

    • john@jtribe.org


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