Figure 1.—Severe cutter roof caused by horizontal stress.

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health TRAPED

MENT OF HEALTH & HUMAN SERVICES . USA

NIOSH Releases New AHSEM and ARBS Software Programs

To Improve Ground Control 

Analysis of Horizontal Stress Effects in Mining

(AHSEM)

It is now widely accepted that horizontal stress is present nearly

everywhere underground. Often it is more severe than the vertical

stress. It is a major cause of roof control problems in underground

mines.

The AHSEM computer program contains two modules to improve

mine layouts for control of horizontal stress. For development, the

user specifies the orientations of the maximum horizontal stress, the

entries, and the crosscuts. Angled crosscuts may be used, and the

angles may be different for the right- and left-hand crosscuts.

AHSEM then shows the user how the stress condition would vary as

the entry and crosscut orientations are changed.

The second module is for longwall mining. Severe stress

concentrations can make headgate conditions hazardous when the

entries are improperly oriented. AHSEM shows whether a particular

longwall orientation and extraction sequence places the headgate

corner in a stress concentration or in stress relief. It also estimates

the magnitude of the stress concentration.

Analysis of Roof Bolt Systems (ARBS)

Selecting the proper roof bolt system from the great variety of

available bolt types and patterns can be confusing. ARBS is

designed to help. The input parameters required by the program are

simple and easy to obtain. They are the most important factors that

determine the roof bolt performance, including the roof quality, the

depth of cover, and the intersection span. Using this information,

ARBS suggests preliminary design values for the—

• Intersection span;

• Bolt length;

• Bolt capacity; and

• Bolt pattern.

Using ARBS, a mine planner can rapidly assess the effect of changes

to any of these on the overall performance of the roof bolt system.

ARBS is based on a NIOSH statistical study of roof falls throughout

the United States. Case histories were collected from 37 mines with a

variety of roof bolt types and patterns in a wide range of geologic

environments. Roof bolt performance was measured in terms of the

number of roof falls that occurred per 10,000 ft of drivage. The study

found that roof falls are rare when the roof is strong and the stress is

low, even with light roof bolting patterns. ARBS addresses the more

difficult conditions, where the roof is weaker and/or the stress is higher.

In addition to helping to select primary support patterns, ARBS can

also show where supplemental support may be needed.

Both AHSEM and ARBS are simple to install and easy to use.

They contain extensive Help files that provide more background on

the research upon which they are based.

Technology News

Milestones in Mining Safety and Health Technology

SAFER HEALTHIER PEOPLE

No. 504 April 2003
Figure 2.—Stress design diagram used in AHSEM.

Figure 3.—Installing a roof bolt in an underground coal mine.

For More Information

To obtain free copies of AHSEM and ARBS, along with other

NIOSH ground control software, contact Donna Opfer at

(412) 386-6564, e-mail: dopfer@cdc.gov. Or you may complete the

order form below, detach, and mail to: Donna Opfer, NIOSH Pittsburgh

Research Laboratory, Cochrans Mill Rd., P.O. Box 18070, Pittsburgh,

PA 15236-0070, or fax to (412) 386-6891.

The software packages are also available at the NIOSH Mining

Website at http://www.cdc.gov/niosh/mining/software.html.

To receive more information about occupational safety and health

problems, call 1-800-35-NIOSH (1-800-356-4674), or visit the

NIOSH Web site 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.

G Please send me free copies of AHSEM and ARBS, along with other NIOSH ground control software.

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