Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the ... more Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the world. This work has found that it is not only challenging but it also has the composition for some interesting rock mechanics and ground control conditions. The paper highlights the extreme mining and rock mass behavior conditions encountered when mining coal at 900 m below surface. It was found that the ground control environment associated with geological weakness, low coal material strength and stiffness, was reasonably well controlled; however, the chain pillar geometry and design did not take these geological weaknesses into consideration. Some of the chain pillars employed were quite large, which resulted in floor punching and secondary floor heave, which causes extreme difficulty for production. No barrier pillar has been employed except for the center 164-m-wide main headings pillar with a w/h ratio in excess of 40. After assessing the location and geometry of a 200-m-thick dole...
Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the ... more Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the world. This work has found that it is not only challenging but it also has the composition for some interesting rock mechanics and ground control conditions. The paper highlights the extreme mining and rock mass behavior conditions encountered when mining coal at 900 m below surface. It was found that the ground control environment associated with geological weakness, low coal material strength and stiffness, was reasonably well controlled; however, the chain pillar geometry and design did not take these geological weaknesses into consideration. Some of the chain pillars employed were quite large, which resulted in floor punching and secondary floor heave, which causes extreme difficulty for production. No barrier pillar has been employed except for the center 164-m-wide main headings pillar with a w/h ratio in excess of 40.
This paper outlines the history of the developments over the last 30 years in understanding the p... more This paper outlines the history of the developments over the last 30 years in understanding the performance of rock reinforcement elements under shear loading through laboratory testing and where the research stands today. Shear testing of rockbolts was fi rst conducted at the Swedish Rock Mechanics Research Foundation in 1974 in hard rock reinforced by rockbolts and was followed by a series of other research attempts around the world over the last 30 years. The factors looked into included the size (length and diameter) and number of bolts, the inclination of the bolts, the relative displacements in joints, joint roughness, the effect of compression, relative strength of rock and grout and elastic modulus of rock and grout. Analytical and numerical solutions were also proposed based on these experiments. The paper takes the reader through these developments and critically analyses their achievements and shortcomings. It highlights the current understanding and its shortcomings, and...
This paper describes the design, construction and commissioning testing program for a laboratory ... more This paper describes the design, construction and commissioning testing program for a laboratory facility at the School of Mining Engineering, UNSW, Australia, aimed at evaluating reinforcement tendon performance when subjected to shear loading. The project has been financially supported through the coal industry ACARP research initiative. The single failure plane design adopted in the test rig has been successful in allowing shear loading to be directly applied to fully installed (and where relevant, pre-tensioned) rock bolts. Initial results are extremely encouraging, and illustrate a significant axial component of load development as shearing takes place – particular in lower strength, softer material types. The paper also outlines future plans for use of this facility
Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the ... more Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the world. This work has found that it is not only challenging but it also has the composition for some interesting rock mechanics and ground control conditions. The paper highlights the extreme mining and rock mass behavior conditions encountered when mining coal at 900 m below surface. It was found that the ground control environment associated with geological weakness, low coal material strength and stiffness, was reasonably well controlled; however, the chain pillar geometry and design did not take these geological weaknesses into consideration. Some of the chain pillars employed were quite large, which resulted in floor punching and secondary floor heave, which causes extreme difficulty for production. No barrier pillar has been employed except for the center 164-m-wide main headings pillar with a w/h ratio in excess of 40. After assessing the location and geometry of a 200-m-thick dole...
Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the ... more Xuandong Coal Mine is mining coal in one of the most challenging underground environments in the world. This work has found that it is not only challenging but it also has the composition for some interesting rock mechanics and ground control conditions. The paper highlights the extreme mining and rock mass behavior conditions encountered when mining coal at 900 m below surface. It was found that the ground control environment associated with geological weakness, low coal material strength and stiffness, was reasonably well controlled; however, the chain pillar geometry and design did not take these geological weaknesses into consideration. Some of the chain pillars employed were quite large, which resulted in floor punching and secondary floor heave, which causes extreme difficulty for production. No barrier pillar has been employed except for the center 164-m-wide main headings pillar with a w/h ratio in excess of 40.
This paper outlines the history of the developments over the last 30 years in understanding the p... more This paper outlines the history of the developments over the last 30 years in understanding the performance of rock reinforcement elements under shear loading through laboratory testing and where the research stands today. Shear testing of rockbolts was fi rst conducted at the Swedish Rock Mechanics Research Foundation in 1974 in hard rock reinforced by rockbolts and was followed by a series of other research attempts around the world over the last 30 years. The factors looked into included the size (length and diameter) and number of bolts, the inclination of the bolts, the relative displacements in joints, joint roughness, the effect of compression, relative strength of rock and grout and elastic modulus of rock and grout. Analytical and numerical solutions were also proposed based on these experiments. The paper takes the reader through these developments and critically analyses their achievements and shortcomings. It highlights the current understanding and its shortcomings, and...
This paper describes the design, construction and commissioning testing program for a laboratory ... more This paper describes the design, construction and commissioning testing program for a laboratory facility at the School of Mining Engineering, UNSW, Australia, aimed at evaluating reinforcement tendon performance when subjected to shear loading. The project has been financially supported through the coal industry ACARP research initiative. The single failure plane design adopted in the test rig has been successful in allowing shear loading to be directly applied to fully installed (and where relevant, pre-tensioned) rock bolts. Initial results are extremely encouraging, and illustrate a significant axial component of load development as shearing takes place – particular in lower strength, softer material types. The paper also outlines future plans for use of this facility
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Papers by Wouter Hartman