Super Stopping: 

A Permanent Solid Stopping for Directing Ventilation Airflows 

in Large-opening Metal/Nonmetal Mines

Objective 

 To identify and evaluate a permanent stopping to direct 

ventilation airflows in large-opening metal/nonmetal mines. 

Background 

Significant air quantities are necessary in underground 

mines to dilute airborne contaminants to statutory concentrations. These contaminants include diesel particulate matter, 

diesel and blasting fumes, and silica dust. Diluting airborne 

contaminants is fundamental to safeguarding the health of 

underground workers. Typically, underground mine ventilation 

air quantities are produced by fans, while stoppings direct the 

required ventilation airflow to the active working areas. 

Stoppings are subjected to air pressures that are generated by the 

mine ventilation fans or stone production blasts. Maximum 

ventilation effectiveness is achieved by using a stopping that will 

withstand the pressure dynamics occurring at the stopping 

location in the mine and endure the timespan for which the 

stopping is to be used. Other important stopping design considerations include ease of installation and resistance to damage 

from repetitive motion caused by air movement against the 

stopping.

Description 

The Super Stopping (Figure 1) is designed for use as a 

permanent, long-term ventilation control in large-opening 

metal/nonmetal mines. The stopping is composed of lowdensity, composite cement and fly ash blocks 48 inches long by 

48 inches high by 32 inches wide and weighing approximately 

1,200 lb. The Super Stopping is a massive, high-strength structure designed to last for the life of the mine. It is constructed by 

using an extended-reach forklift to lift and set each block. 

Factory-installed holes are cast into the blocks to readily receive 

the forklift tines. The Super Stopping is constructed in three 

phases: (1) site preparation and foundation, (2) block stacking 

and adhesion, and (3) top capping and sealing. 

Phase 1 – Site Preparation and Foundation 

The stopping construction site should be reasonably uniform 

on the walls (ribs) of the mine, level on the floor, and of 

relatively equal distance from roof to floor across the opening. 

The footing for the stopping should consist of standard 3,000-psi 

concrete embedded with standard 6-inch by 6-inch steel wire 

mesh reinforcement. It should be 44 inches wide to provide an 

extra 6 inches on each side of the stopping block, at least 

6 inches thick, and span the mine entry. 

Phase 2 – Block Stacking and Adhesion 

The first course of blocks is aligned along a chalk line 

struck on the concrete footing. Since it is critical to maintain a 

stable structure as the construction progresses, careful articulation of the blocks with the forklift is necessary for proper vertical alignment of the stopping. Each block is secured in place 

Figure 1.—Schematic of the Super Stopping for use in largeopening mines. 

No. 518 May 2006 
with a high-grade polyurethane construction adhesive. The 

adhesive is applied in a Z-shaped pattern with an approximately 

2-inch spacing on all contacting sides (non-free-face) of the 

blocks. The blocks must be laid tightly to ensure adequate 

adhesive contact for proper bonding and minimal leakage. The 

blocks are stacked using the standard wall-building method of a 

half-block staggering pattern laid in successive layers (Figure 2). 

The fly ash blocks can be scribed and readily cut to fit the rib 

with a simple handheld saw or ax. Layers of blocks are laid 

until the remaining gap between the top of the last block and the 

roof is smaller than the height of the 48-inch block. 

Phase 3 – Top Capping and Sealing 

To complete construction, smaller or standard-size fly ash 

blocks, 24 inches by 16 inches by 8 or 6 inches, are used to top 

cap the stopping structure. Consistent with phase 2, the smaller 

blocks are half-block staggered and cut to conform to the mine 

roof and sides and secured with construction adhesive. The 

blocks should be cut to fit within approximately 3 inches of the 

mine opening surfaces. 

Figure 2.—Partially constructed Super Stopping. 

 The gaps at the top and sides of the stopping are sealed 

using an expansion foam product. The foam is applied to approximately one-half the depth (16 inches) of the blocks until the 

foam completely fills the void. The expansion foam conforms to 

the shape of both the cut blocks and mine opening surfaces, thus 

increasing structural stability and minimizing air leakage. 

Test Results

Stoppings in an underground mine must withstand air blasts 

associated with mine development and stone production blasting. The structural integrity of stoppings can be tested by subjecting them to known blast loads. Blast pressure tests using 

unconfined explosive charges were conducted on the Super 

Stopping in the large underground entries at NIOSH’s Lake 

Lynn Laboratory. The tests confirmed the integrity of the stopping, which included the strength of the adhesive between 

blocks, the effectiveness of the perimeter foam, and the overall 

stability of the stopping. As a benchmark for evaluating the 

Super Stopping, in-mine blast pressures at an operating underground stone mine were measured at approximately 1 psig. The 

Super Stopping was subjected up to 3 psig blast pressure from an 

unconfined explosive charge during the Lake Lynn evaluations. 

The Super Stopping readily withstood these blast test evaluations without damage to its structural integrity. 

For More Information

For more information on the Super Stopping, contact 

Roy H. Grau III, NIOSH Pittsburgh Research Laboratory, 

Cochrans Mill Rd., P.O. Box 18070, Pittsburgh, PA 15236–

0070; phone: (412) 386–6562; fax: (412) 386–6891; e-mail: 

RGrau@cdc.gov.

To receive other information about occupational safety and health 

topics, call 1–800–35–NIOSH (1–800–356–4674), or visit the 

NIOSH Website at www.cdc.gov/niosh 

Mention of any company name or product does not constitute 

endorsement by the National Institute for Occupational Safety 

and Health. 

DHHS (NIOSH) Publication No. 2006–134