1. NIOSH Pittsburgh Research Laboratory
Comparison of the Transverse Load Capacities of Various Block Ventilations Stoppings Under Arch Loading Conditions
Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®.
Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion.
Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience.
Thomas M. Barczak
Timothy J. Batchler
NIOSH Pittsburgh Research Laboratory

2. Mine Ventilation Stoppings
Insufficient capability to withstand transverse loading.
What caused this failure?

3. ASTM E 72 TESTING
CFR Part Ventilation Controls requires stoppings to be evaluated in accordance with ASTM E-72 specifications.
Provide an average capacity of 39 psf.
Freestanding wall.
Roller utilized to prevent rotational restraint at base of wall.
Rollers utilized at contact load/reaction points to prevent inducing any moments or restraint to wall deflection.

4. Problem Statement
This presentation compares the transverse load capabilities of several block materials and wall dimensions commonly used in stopping constructions.
Mine Ventilation stoppings are dependent upon the material strength of the block, the height and thickness of the wall and its boundary conditions.

5. Test Protocol for Arch-Loading
Transverse load
Compression
Tension
Mine Roof
Mine Floor
Wall bridges between mine roof and floor.
Compressive forces are developed within the wall.

6. Mine Roof Simulator (MRS)
Multi axis load frame.
Controlled vertical and horizontal movement of lower platen.
3 million lbs capacity.

7. Simulating Rigid Arching In the MRS
Transverse load

8. Upper Platen Lower Platen Single Column Concrete Wall Adjusting Nuts
20 Kip Load Cell
Metal Plate
Rolling Tray
Platen
Bolt
Lower Platen

9. Arch-Loading Evaluation
The applied horizontal force to the base of the half-wall by the MRS is measured.
This equates to the transverse pressure acting of the stopping wall.

10. Various Block Materials
Standard concrete masonry unit (CMU)
Lightweight aggregate CMU
Hollow core block
Autoclaved aerated concrete (AAC) Materials
Foamed Cement
Extruded Foam Cement

11. Transverse Load Capacities
Several factors influence the transverse load capacity.
Three critical parameters are:
Block Strength
Block Thickness
Wall Height

12. Block Material Properties
Wide range of block materials.
Current ASTM criterion (freestanding wall evaluation)

13. Block Height and Thickness
Transverse load decreases as the entry height increases
Transverse load increases as the wall thickness increases

14. Critical Design Parameters
Direct correlation between block compress strength (fc), wall height (L), wall thickness (t), and transverse load capacity.

15. Impact from Convergence
Convergence causes increased thrust force on the hinge points in the wall.
This additional thrust force increases the wall’s resistance to deflect outward, thus resulting in higher transverse load capacity.
Benefits from convergences is lost once the block strength is reached.

16. Vertical Preload Pressure
30-in half-wall height
45-in half-wall height
60-in half-wall height

17. Rigid Boundary Stiffness
Rigid arch conditions apply when the abutments (mine roof and floor) do not deform.
Lateral displacement is controlled by the stiffness and elastic response of the wall
If the abutments are not rigid, then more lateral displacement will occur, resulting in a decrease in the transverse load capacity.
Lateral Displacement

18. Reduction of System Stiffness
The impact of the abutment stiffness has a greater impact on the shorter walls.
30-in half-wall height
60-in half-wall height
45-in half-wall height

19. Impact of Preload on Boundary Stiffness
As preload increases, reductions from boundary stiffness to transverse pressure are diminished.

20. Conclusions
A new test protocol was used to evaluate several blocks currently used for stoppings.
Compressive strength of the block, wall height, and block thickness have significant impact on the transverse load capacity.
Boundary conditions and convergence greatly affect the transverse load capacity.

21. Any Questions
Ice Block - 12 feet tall - 10 feet wide - weighs 20 tons

22. Any Questions