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Stress relief by hydraulic fracturing - dream or reality?
394A 926422 Stress relief by hydraulic fracturing - dream or reality? Roegiers, J C; BenNaceur, K Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P257-263. Publ Rotterdam." A A Balkema, 1990
years after partial extraction of a regional stability pillar indicated some pillars had failed by a stable crushing mechanism, some by an explosive mechanism. Failure mode was examined in relation to pillar geometry, stope closure, and geology. It was seen that pillars in moderately to heavily jointed areas tended to fail in a controlled manner, with a degree of punching into the footwall.
The idea of using hydraulic fracturing for stress relief is not new: it has been suggested for applications in tectonic fault lubrication for burst prone mines. The potential energy release and its extent have been examined for various stimulation schemes using a newly developed numerical simulator based on LEFM principles. Influence of job size, pumping rate, fluid viscosity, and proppant density are examined and effects of frictional interfaces and rock inhomogeneity studied. Practical recommendations for field application of hydraulic fracturing stress relief are presented.
926426 Probabilistie evaluation of ore pass stability and support Stacey, T R; Bartlett, P J Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P309-315. Publ Rotterdam: A A Balkema, 1990
926423 Cyclic process of fracture and failure around deep-level Iongwall stopes Roest, J P A; Gramberg, J Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P265-272. Publ Rotterdam: A A Balkema, 1990 Gradual closure of a stope of a longwall gold reef operation has been examined, using a combination of accurate field observations, fracture mechanics principles, and fracture and fracture plane analysis. Five different stress regimes have been recognised, and three different cycles on mini, macro, and mega scales established. Interaction between the three cycles is related to face progression. 926424 Collapse of a section in a highway tunnel - a case study Sofianos, A I Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P?97-302. Publ Rotterdam." A A Balkema, 1990 A transalpine tunnel failed during construction over a length of about 58m, roughly divisible into three regions, the first of relatively recent siltstone, the second clay schist, the third clay schist and serpentinite with heavy shearing and water. In region I, the shotcrete lining settled when earth was excavated from beneath primary support in order to cast the final lining. This caused damage to the lining in regions II and III. Squeezing conditions in regions II and III further led to buckling of the support and lining. Remedial measures are described. Prevention by increased density of bolts in region I and drainage to reduce water pressure in regions II and III is specified retrospectively. 926425 Observed crush pillar failure between two regional stability pillars at Impala Mines Spencer, D A; Kotze, T J Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P303-307. Publ Rotterdam: A A Balkema, 1990 Impala workings are supported by a system of dip oriented barrier pillars plus small pillars to provide regional stability. Acoustic monitoring of a worked-out stope at depth 550m two
Ore passes at the Premier Mine are in norite rock, fairly close to the kimberlite pipe. Construction is by raise boring then enlargement by blasting. Failures have occurred at both construction stages. Total lining in the generally competent tough rock was considered excessive. Joint characteristics of the norite were mapped and a probabilistic assessment of stability undertaken to identify potentially unstable blocks and allow optimisation of spacing of support elements.
926427 Difficulties in deep foundation of underground sewer in granodiorite massif of Brno Smid, J Proe 6th International Congress International Association of Engineering Geology, Amsterdam, 6-10 August 1990 V4, P2527-2532. Publ Rotterdam." A A Balkema, 1990 Construction of a 3km long tunnel in extremely complex geology is described. The bedrock profile is extremely irregular, and in several places Neogene sands and clays are met at tunnel depth. There are many vertical faults. Initial problems with water and sand inrush were overcome by using suitable construction methods. After about 2000m had been driven, massive collapse of sand and water into the tunnel led to a large cavern developing, whose roof failed and fnally daylighted leaving a large crater. This has been filled and the project completed, but rerouting around the failure zone was necessary as no acceptable ground treatment method was found.
926428 Stability analysis of the Hoorensberg room and pillar mine, Southern Limburg, using separate shape factors for intact and cracked pillars Bekendam, R F; Dirks, W G Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6-10 August 1990 V4, P2627-2635. Publ Rotterdam: A A Balkema, 1990 The abandoned Hoorensberg mine, excavated in Upper Cretaceous calcarenite,is affected by intensive pillar fracturing. To prevent large scale collapse and consequent surface subsidence, a support program was developed, based on Goodman's tributary area method. Shape factors for intact and fractured pillars were determined on the basis of laboratory compression tests. The analysis results largely reflect the observed state of the mine. Remedial support of masonry pillars will be installed.
it') 1992 Pergamon Press Ltd. Reproduction not permitted
years after partial extraction of a regional stability pillar indicated some pillars had failed by a stable crushing mechanism, some by an explosive mechanism. Failure mode was examined in relation to pillar geometry, stope closure, and geology. It was seen that pillars in moderately to heavily jointed areas tended to fail in a controlled manner, with a degree of punching into the footwall.
The idea of using hydraulic fracturing for stress relief is not new: it has been suggested for applications in tectonic fault lubrication for burst prone mines. The potential energy release and its extent have been examined for various stimulation schemes using a newly developed numerical simulator based on LEFM principles. Influence of job size, pumping rate, fluid viscosity, and proppant density are examined and effects of frictional interfaces and rock inhomogeneity studied. Practical recommendations for field application of hydraulic fracturing stress relief are presented.
926426 Probabilistie evaluation of ore pass stability and support Stacey, T R; Bartlett, P J Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P309-315. Publ Rotterdam: A A Balkema, 1990
926423 Cyclic process of fracture and failure around deep-level Iongwall stopes Roest, J P A; Gramberg, J Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P265-272. Publ Rotterdam: A A Balkema, 1990 Gradual closure of a stope of a longwall gold reef operation has been examined, using a combination of accurate field observations, fracture mechanics principles, and fracture and fracture plane analysis. Five different stress regimes have been recognised, and three different cycles on mini, macro, and mega scales established. Interaction between the three cycles is related to face progression. 926424 Collapse of a section in a highway tunnel - a case study Sofianos, A I Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P?97-302. Publ Rotterdam." A A Balkema, 1990 A transalpine tunnel failed during construction over a length of about 58m, roughly divisible into three regions, the first of relatively recent siltstone, the second clay schist, the third clay schist and serpentinite with heavy shearing and water. In region I, the shotcrete lining settled when earth was excavated from beneath primary support in order to cast the final lining. This caused damage to the lining in regions II and III. Squeezing conditions in regions II and III further led to buckling of the support and lining. Remedial measures are described. Prevention by increased density of bolts in region I and drainage to reduce water pressure in regions II and III is specified retrospectively. 926425 Observed crush pillar failure between two regional stability pillars at Impala Mines Spencer, D A; Kotze, T J Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P303-307. Publ Rotterdam: A A Balkema, 1990 Impala workings are supported by a system of dip oriented barrier pillars plus small pillars to provide regional stability. Acoustic monitoring of a worked-out stope at depth 550m two
Ore passes at the Premier Mine are in norite rock, fairly close to the kimberlite pipe. Construction is by raise boring then enlargement by blasting. Failures have occurred at both construction stages. Total lining in the generally competent tough rock was considered excessive. Joint characteristics of the norite were mapped and a probabilistic assessment of stability undertaken to identify potentially unstable blocks and allow optimisation of spacing of support elements.
926427 Difficulties in deep foundation of underground sewer in granodiorite massif of Brno Smid, J Proe 6th International Congress International Association of Engineering Geology, Amsterdam, 6-10 August 1990 V4, P2527-2532. Publ Rotterdam." A A Balkema, 1990 Construction of a 3km long tunnel in extremely complex geology is described. The bedrock profile is extremely irregular, and in several places Neogene sands and clays are met at tunnel depth. There are many vertical faults. Initial problems with water and sand inrush were overcome by using suitable construction methods. After about 2000m had been driven, massive collapse of sand and water into the tunnel led to a large cavern developing, whose roof failed and fnally daylighted leaving a large crater. This has been filled and the project completed, but rerouting around the failure zone was necessary as no acceptable ground treatment method was found.
926428 Stability analysis of the Hoorensberg room and pillar mine, Southern Limburg, using separate shape factors for intact and cracked pillars Bekendam, R F; Dirks, W G Proc 6th International Congress International Association of Engineering Geology, Amsterdam, 6-10 August 1990 V4, P2627-2635. Publ Rotterdam: A A Balkema, 1990 The abandoned Hoorensberg mine, excavated in Upper Cretaceous calcarenite,is affected by intensive pillar fracturing. To prevent large scale collapse and consequent surface subsidence, a support program was developed, based on Goodman's tributary area method. Shape factors for intact and fractured pillars were determined on the basis of laboratory compression tests. The analysis results largely reflect the observed state of the mine. Remedial support of masonry pillars will be installed.
it') 1992 Pergamon Press Ltd. Reproduction not permitted