This can be performed when ground conditions are "soft" or incompetent. Polyurethane Grouts of an expansive type are particularly suitable for this purpose since they are injected in liquid form (allowing for excellent penetration) and during reaction are expansive, which simultaneously creates compaction and consolidation. This increases in-situ strength enormously and generally, also provides a waterproof barrier.
Whether during construction of new mine portals, or following harsh climatic changes, the face of highwalls can present significant hazards. Sub-Technical can provide easily deployed methods to contain and secure these areas. Methodology can vary from installation of bolted mesh covering and may include polyurethane grouting which consolidates broken rock and makes the area safe.
Low Cover Crossing
Mining - in Appalachia in particular - often presents issues where valleys must be crossed underground to gain access to reserves. Often this means that a number of surface features existing in the valley must be protected from the possibility of undermining in close proximity, causing damage. Additionally, the safety of the workforce and integrity of entries underground must be assured. Surface features may include the following: Buildings, Roads, Rivers, Railroads, Sewers and Utilities.
A common means of retention and support, Sub-Technical has the equipment and workforce to effectively place these anchors. Where doubtful conditions exist engineers may wish to consider polyurethanes grout as the anchoring medium due to its versatility and mechanical properties. Sub-Technical is also involved in remedial measures to seal and reconstitute failed anchors to and beyond original test criteria.
Acid Mine Drainage (A.M.D.)
Sub-Technical has been involved with various agencies to mitigate a wide variety of discharge sources. Some involving passive treatment areas for known outputs, some occurring through channels in hydrology; and others occurring as a result of earthworks, [surface or sub-grade]. Regardless, our choice of grout sealant (which are unaffected by Ph levels) and our experience in all of the above situations make us a clear choice to resolve these problems.
Concrete Crack Injection
Concrete structures deteriorate for many reasons, such as load changes overstressing, freeze/thaw and age. Containment structures leaking can be sealed. Support structures can be rehabilitated.
With over a decade of direct experience with this geologic feature we have the ability to secure the conditions from leaking and eliminating the possibility of "blow out" from extruding clays. Pits and quarries can suffer huge pumping costs as a result of not addressing these problems. The extent of the effects of "Karst" are truly global; and the issues pertinent to it are numerous, including subsidence, sink holes, damage to utilities, property and general infrastructure. It effects many aspects of ground, hydrology and can be extremely destructive.
Mine Entry Bulkhead Sealing
Sub-Technical is extremely familiar with the installation of, and repair of, bulkhead seals thereby ensuring that new installations are water-tight and that repairs are competent and secure. We have pioneered many engineered modifications which increase effectiveness and longevity.
A variety of problems can occur with ponds: failed liners, ground movement, failed decant pipes, rodent excavation, etc. All of the above can be remediated with expansive polyurethane grouts, (NSF approved for use in drinking water applications) generally the likely repair scenario can be defined with a phone call to our office.
Often there are streams in areas where undermining has caused fracturing to the surface and subsequent loss of flow to those fractures. Polyurethane grout is injected in the area below the stream bed to create an impervious flexible membrane, sealing the flow paths through the fractures and permanently restoring stream flow.
Well Water Sealing
Many situations can be present when dealing with well closure - Artesian output, A.M.D., improperly performed cement / bentonite grouting, damaged casing, and crossflow. All of these anomalies can be cured using expansive grouts, with environmental approvals (NSF approved for use in drinking water applications) and the accumulated knowledge and applications experience that comes with dealing with Sub-Technical.
Artesian Water Sealing
When Artesian flows are a problem, Sub-Technical has perfected methodologies and custom designed grout formulations to close down flows quickly, safely and most effectively.
Bulkhead Water Sealing
Whether existing structures which are leaking, or fresh entries which require sealing, Sub-Technical has the permanent water control solution with polyurethane grout.
This is a combination process where the placement of fill material (usually limestone gravel) is done by pneumatic stowing followed by injection of the stowed material with polyurethane grouting tight permanent seals.
Where concrete liners deteriorated through ground pressures or water intrusion and freeze thaw cycle. Polyurethane injection can control water and consolidate poor ground conditions providing effective long term relief.
Ventilation Seal Repair
A very "hot" topic in recent times. Leaking ventilation seals, whether gasses or water is the problem, is a hazard that no responsible operator should ignore. Sub-Technical is certainly capable of performing this work at a consummate expense.
Void Filling is performed for a variety of reasons - sometimes structural and often also related to water control and even ventilation. Sub-Technical has developed techniques and materials that directly address these issues. Polyurethane grouts with reaction times in seconds allow extremely rapid deployment. Due to their speed of set-up they can eliminate, or greatly reduce the need for formwork. Consequently, these systems compete with other conventional cementitous systems very favorably.
To combat excessive flushing of gob into the working area while retrieving face equipment during longwall moves.
The process retains gob material with high density foam to allow rapid recovery rates while maintaining safe working conditions. It can often be combined with roof application where bad conditions exist. (Flame retardants available for approved applications.)
Coal mine longwall face falls (loss of immediate roof through frontal abutment pressure).
This is a combination process where the placement of the fill material (usually limestone gravel) is done by pneumatic stowing followed by injection of the stowed material with Polyurethane grouts providing tight permanent seals. Where surface soils require cessation of movement, topical application of Polyurethane can form a surface crust to stabilize them. Deeper injection provides coverage to sub-levels consolidating the mass of material. Very high compressive strengths are achieved when used with certain soils.
The maintenance of a mines roof condition is the key to safety and productivity. When dealing with roof problems a mine should consider that polyurethane grouts can provide a lasting solution that will not fail, providing that the contractor is competent and his recommended materials are appropriate.