Pillar Strength and Design Methodology for Stone Mines

Underground stone mines in the United States make use of the room-and-pillar method of mining. A prerequisite for a safe working environment is that the pillars should adequately support the overburden and the pillar ribs and rooms should remain stable during mining. At present pillar dimensions are either based on experience at neighboring mines or on strength equations that were developed for metal or non-metal mines. This paper presents a pillar design methodology that was developed from a study of pillar performance in operating stone mines. Data were collected that describe the rock mass quality, pillar conditions, mining dimensions and intact rock strength. The results showed that current mining practices have resulted in generally stable pillar layouts with no recent cases of extensive pillar collapses. However, a small number of single failed or failing pillars were observed in otherwise stable layouts. Numerical analyses were used to supplement the observations and develop a pillar strength equation that describes the stable and small number of failed pillars observed. The developed strength equation can be used to design stable pillar layouts provided the factor of safety is greater than 1.8 and the width-to-height ratio of the pillars is greater than 0.8. The paper concludes with guidelines for applying the developed equation and selecting appropriate input parameters.

[1]  J. Cogan.  Support of Underground Excavations in Hard Rock , 1996 .

[2]  D. Tolfree,et al.  Using Confinement As a Means to Estimate Pillar Strength In a Room And Pillar Mine , 2007 .

[3]  A. H. Salamon,et al.  A study of the strength of coal pillars , 1967 .

[4]  A. T. Iannacchione,et al.  Safer mine layouts for underground stone mines subjected to excessive levels of horizontal stress , 2003 .

[5]  Dennis R. Dolinar,et al.  Pillar Stability Issues Based On A Survey Of Pillar Performance In Underground Limestone Mines , 1900 .

[6]  W. A. Hustrulid.  A review of coal pillar strength formulas , 1976 .

[7]  Ismet Canbulat,et al.  Seam-Specific Pillar Strength Formulae for South African Collieries , 2006 .

[8]  G. Esterhuizen.  An Evaluation Of The Strength Of Slender Pillars , 1900 .

[9]  Diederichs,et al.  Underground Works In Hard Rock Tunnelling And Mining , 2000 .

[10]  M.D.G. Salamon,et al.  Stability, instability and design of pillar workings , 1970 .

[11]  Dennis R. Dolinar,et al.  Evaluation of the Effects of Length on Strength of Slender Pillars in Limestone Mines Using Numerical Modeling , 2007 .

[12]  Winton J. Gale,et al.  EXPERIENCE OF FIELD MEASUREMENT AND COMPUTER SIMULATION METHODS FOR PILLAR DESIGN By , 2008 .

[13]  A. T. Iannacchione,et al.  Analysis Of Pillar Design Practices And Techniques For U.S. Limestone Mines , 1900 .

[14]  P J Lunder,et al.  Determination of the strength of hard-rock mine pillars , 1997 .

[15]  E. T. Brown,et al.  Rock Mechanics: For Underground Mining , 1985 .

[16]  W. L. Lane,et al.  Pillar extraction and rock mechanics at the Doe Run Company in Missouri 1991 to 1999 , 1999 .

[17]  Dennis R. Dolinar,et al.  Roof Stability Issues in Underground Limestone Mines in the United States , 2007 .

[18]  Dennis R. Dolinar,et al.  Assessment of stable and failed pillars in underground limestone mines , 2008 .

[19]  Per John Lunder.  Hard rock pillar strength estimation an applied empirical approach , 1994 .

[20]  C. D. Martin,et al.  The strength of hard-rock pillars , 2000 .

[21]  R. Karl Zipf,et al.  Design Methods to Control Violent Pillar Failures in Room-And-Pillar Mines , 1900 .

[22]  Gabriel S. Esterhuizen,et al.  Effects Of Weak Bands On Pillar Stability In Stone Mines: Field Observations And Numerical Model Assessment , 1900 .