Mining Topic: Horizontal Stress

What is the health and safety problem?

High Horizontal Stress

High horizontal stresses produce extensive and sudden rock failures. The U.S., Australian, and United Kingdom coal and the Canadian hard rock industries have long recognized the significance of high horizontal stresses as a factor affecting the stability of roof and rib conditions in underground mines.

What is the extent of the problem?

High horizontal stress is most prevalent in the Eastern and Midwestern coal beds but does occur in other locations.

How is OMSHR addressing this problem?

The Office of Mine Safety and Health Research (OMSHR) has been conducting research to develop a better fundamental understanding of ground control strategies through field and laboratory studies. The consequences of widening rooms, changing geology and horizontal stress, and different roof support systems have been addressed. Such specialized techniques as the "advance and relieve" plan have been studied. In this plan, horizontal stresses are relieved by removing a pillar on one side of a panel as the panel advances, creating a cave that relieves horizontal stress across the panel.

What are the significant findings?

OMSHR has developed best practices for mines encountering high horizontal stress. A software program, Analysis of Horizontal Stress Effects in Mining (AHSM), was developed to give mine designers the optimal orientation for entries.

What are the next steps?

OMSHR is monitoring the industry to determine if there is an upswing in potentially related hazards.

Noteworthy Publications & Products

• Advance and Relieve Mining: A Method to Mitigate the Effects of High Horizontal Stress on the Mine Roof (2012-08)
  Evaluation of the "Advance and Relieve" mining method is described to determine effectiveness for conditions where high horizontal stresses caused long running roof falls resulting in hazardous conditions and the premature abandonment of panels.
• AHSM - Analysis of Horizontal Stress Effects in Mining (2012-10)
  A software program to help improve mine layouts for control of horizontal stress.
• Case History of the Response of a Longwall Entry Subjected to Concentrated Horizontal Stress (2012-08)
  A study of ground behavior, reinforcement performance and stress redistribution looked at a longwall tailgate under severe horizontal stress. Comparison to field results showed that a FLAC-2D model captured the significant roof and support behavior.
• Controlling Roof Beam Failures From High Horizontal Stresses in Underground Stone Mines (2008-09)
  A design technique is presented which provides stone miners with a method for making stability assessments. The consequences of widening rooms, changing geology and horizontal stresses, and different rock bolts on roof beam failure are discussed.
• High Stress Mining Under Shallow Overburden in Underground U.S. Stone Mines (2012-08)
  This study of the Chestnut Ridge Anticline found that high levels of horizontal stress are to be expected and that local geologic and topographic structures can alter the magnitude and possibly the orientation of the horizontal stress field.
• Horizontal Stress and Longwall Headgate Ground Control (2012-08)
  Horizontal stresses are caused by global plate-tectonic forces. This paper presents six case histories of mines that encountered roof falls or difficult ground conditions at the headgate caused by horizontal-stress concentrations.
• Performance of Roof Support Under High Stress in a U.S. Coal Mine (2010-08)
  The primary goal of this project was to obtain detailed data on the interaction between the mine roof and the support elements for use in modeling studies.  The study site was a longwall tailgate subjected to high horizontal stress.
• Rock Mechanics Study of Lateral Destressing for the Advance-and-Relieve Mining Method (2012-08)
  The advance-and-relieve method benefits from lateral destressing. Numerical modeling proved useful in studying the basic mechanics of lateral relief while investigating the sensitivity of results to different parameters using controlled experiments.
• Safer Mine Layouts for Underground Stone Mines Subjected to Excessive Levels of Horizontal Stress (2012-08)
  At an underground stone mine, a modified stress-control mine layout is reducing hazardous conditions associated with excessive horizontal stress. Findings show that the layout provides more stable conditions, resulting in a safer working environment.
• Utilizing the 'Advance and Relieve' Method to Reduce Horizontal Stress Affects on the Mine Roof, A Case Study (2012-08)
  The practical application of the "advance and relieve" method is discussed. A trial of the method was conducted for a room and pillar coal operation that was experiencing roof cutters and long running roof falls caused by high horizontal stresses.
• Variation of Horizontal Stresses and Strains in Mines in Bedded Deposits in the Eastern and Midwestern United States (2012-08)
  This paper describes a study where the variations of the magnitude of the horizon stresses in sedimentary deposits in the eastern and Midwestern U.S. are examined with respect to two factors, the elastic modulus of the rock and the site depth.