Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
Records 1-5 (of 5 Records) |
Query Trace: Batchler T [original query] |
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Large-scale laboratory investigation of pillar-support interaction
Chaurasia A , Walton G , Sinha S , Batchler TJ , Moore K , Vlachopoulos N , Forbes B . J Rock Mech Geotech Eng 2024 [Epub ahead of print] Underground mine pillars provide natural stability to the mine area, allowing safe operations for workers and machinery. Extensive prior research has been conducted to understand pillar failure mechanics and design safe pillar layouts. However, limited studies (mostly based on empirical field observation and small-scale laboratory tests) have considered pillar-support interactions under monotonic loading conditions for the design of pillar-support systems. This study used a series of large-scale laboratory compression tests on porous limestone blocks to analyze rock and support behavior at a sufficiently large scale (specimens with edge length of 0.5m) for incorporation of actual support elements, with consideration of different w/h ratios. Both unsupported and supported (grouted rebar rockbolt and wire mesh) tests were conducted, and the surface deformations of the specimens were monitored using three-dimensional (3D) digital image correlation (DIC). Rockbolts instrumented with distributed fiber optic strain sensors were used to study rockbolt strain distribution, load mobilization, and localized deformation at different w/h ratios. Both axial and bending strains were observed in the rockbolts, which became more prominent in the post-peak region of the stress-strain curve. |
Full-scale demonstration and performance evaluation of a hybrid geopolymer/biopolymer cementitious material developed for pumpable roof supports in underground mines
Nikvar-Hassani A , Batchler T , Zhang L . Min Metall Explor 2024 Recently, a new hybrid geopolymer/biopolymer (GP/BP) cementitious material was developed for improving the performance of pumpable roof supports in underground mines. This study demonstrates the application of the hybrid GP/BP cementitious material and validates its effectiveness in full-scale. In this regard, eight (8) full-size (0.61 m diameter and 1.52 m height) cribs were produced in collaboration with Minova International Ltd and tested at the National Institute for Occupational Safety and Health (NIOSH) Mine Roof Simulator (MRS) Laboratory. These full-size cribs were produced with different material configurations to evaluate the effect of water to solid (W/S) ratio, Portland cement (PC) content, and BP dosage. The results demonstrated and validated the effectiveness of the hybrid GP/BP cementitious material in increasing the peak and residual bearing capacities of pumpable cribs and eliminating the issue of deterioration when exposed to air compared with the conventional Portland cement/fly ash (PC/FA) cementitious material currently used in practice. On average, the peak uniaxial compressive strength (UCS) and the highest residual UCS after peak of the full-size cribs produced from the hybrid GP/BP cementitious material are 1.90 and 1.33 times of those of the PC/FA-based full-size cribs by one company and 2.32 and 1.66 times of those of the PC/FA based full-size cribs by the other company, respectively. © Society for Mining, Metallurgy & Exploration Inc. 2024. |
Evaluating size effects for a porous, weak, homogeneous limestone
Sinha S , Walton G , Chaurasia A , Diederichs M , Batchler T . Rock Mech Rock Eng 2022 [Epub ahead of print] In rock engineering, size effects have been a topic of extensive research since the early 1960s, and despite many advances over the years, our understanding of size effect remains incomplete, especially for weak, porous, homogeneous rocks. Indeed, the vast majority of studies related to size effect have specifically considered low porosity rocks (generally crystalline). To bridge this gap in knowledge, we conducted unconfined compression tests on cubic limestone blocks ranging in size from 0.1 to 0.9 m. Texas Cream Limestone, which is a porous, homogeneous, weak rock, was chosen for this study. As this rock has not previously been studied in the literature, conventional compression tests and indirect tensile strength tests on cylindrical specimens were completed prior to testing the cube specimens. For the largest specimens, 3D digital image correlation (3D-DIC) was employed to track the surficial displacements as a function of the applied load. The tests revealed a lack of size effect for the entire range of block sizes considered. To evaluate size effects more broadly, data from prior studies on sedimentary rocks were compiled, and a tendency for the magnitude of the size effect on strength to decline with increasing porosity was noted. Some hypotheses regarding this trend are presented and evaluated based on strain-field heterogeneity metrics obtained from the 3D-DIC analysis. |
Analysis of steel prop supports subjected to vertical and lateral loading
Mohamed K , Batchler T . Min Metall Explor 2022 39 (5) 2001-2010 Standing supports have been used in coal mines for decades to enhance roof support capability. Sometimes standing supports are used as a tool to resist the lateral movement of spalled ribs. Researchers from the National Institute for Occupational Safety and Health (NIOSH) are conducting a testing program for different types of standing supports (steel and timber) to investigate the effect of lateral loading on their vertical loading capacities and the factors affecting their lateral loading capacities. In this paper, the mine roof simulator (MRS), at the NIOSH Pittsburgh research facility, was used to determine the response of steel props to vertical and horizontal loadings. Finite element models (FEMs) were developed and verified using the tested steel props. To justify the testing program for testing standing supports with end-conditions of rock-like materials, the verified prop models were used to study the effect of a wide range of roof and floor materials (gray shale, shale, and claystone) on the critical buckling loads of the steel props. Also, several lateral loading scenarios were evaluated in which the steel props were laterally loaded at different heights. The critical buckling load for steel props setting up against a claystone roof and floor was found to be one-half of that shown by the MRS test where roof and floor platens are made of steel. Minimum prop performance was observed when the lateral load was applied at the mid-height of the steel prop, especially at small lateral displacement (less than 2 in). 2022, This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply. |
Analysis of the design and performance characteristics of pumpable roof supports
Batchler T . Int J Min Sci Technol 2016 27 (1) 91-99 Pumpable roof supports are currently being used to provide a safe working environment for longwall mining. Because different pumpable supports are visually similar and installed fundamentally in the same manner as other supports, there is a tendency to believe they all perform the same way. However, there are several design parameters that can affect their performance, including the cementitious material properties and the bag construction practices that influence the degree of confinement provided. A full understanding of the impact of these design parameters is necessary to optimize the support application and to provide a foundation for making further improvements in the support performance. This paper evaluates the impact of various support design parameters by examining full-scale performance tests conducted using the National Institute for Occupational Safety and Health (NIOSH) Mine Roof Simulator (MRS) as part of manufacturers' developmental and quality control testing. These tests were analyzed to identify correlations between the support design parameters and the resulting performance. Based on more than 160 tests over 7. years, quantifiable patterns were examined to assess the correlation between the support dimensions, cementitious material type, wire pitch, and single-wall vs. dual-walled bag designs to the support capacity, stiffness, load shedding events, and yield characteristics. |
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