Stress Related Fracturing in Dimension Stone Quarries

In Missouri, the horizontal stresses (pressures) in the near surface rock are uncommonly high. While the vertical stresses in rock are simply a function of the weight of the overlying rock, near surface stresses can be many times higher. The near surface horizontal stresses can be in excess of 5 times greater than the vertical stresses. In this research, Flatjack method was used to measure horizontal stress in Red Granite Quarry in Missouri. The flat jack method is an approved method of measuring ground stresses. A saw cut is used to relax the stress in the ground by allowing the rock to deform inwards the cut. A hydraulic flat jack is used to inflate the slot; to push the rock back to its stressed position, as measured by a strain gauge on either side of the slot. The pressure in the jack, when the rock is exactly back to its original position, is equal to the ground stress before the saw cut was made. According to the results, present production direction for each pit is not good because the maximum stress direction is perpendicular with production direction. This case causes unintentional breakage results in the loss rock. The results show that production direction should be changed

Finite element method simulation for the prediction of mechanical properties of three-dimensional periodic bioactive glass scaffolds

The desired mechanical properties of porous tissue engineering scaffolds may differ depending on the clinical applications. Therefore, it is crucial to be able to control these properties for specific cases. In the current study, cube shape, porous, silicate-based (13-93) bioactive glass scaffolds were fabricated by robotic deposition method. Scaffolds were prepared layer by layer to form constructs with a grid-like microstructure. After binder burnout, the constructs were sintered for 1 h at 700 degrees C to produce scaffolds consisting of dense bioactive glass struts (similar to 280 +/- 20 aem in diameter) at different pore widths (300 +/- 50, 600 +/- 25, and 900 +/- 50 aem). The mechanical response of the scaffolds in compression was measured experimentally. The stress analysis of the complete scaffolds with varying pore width and layer spacing parameters has been performed by finite element method (FEM) under compression to investigate the state of stress fields created within the scaffolds. Such an analysis can be used to vary several geometrical parameters and to choose the most suitable ones for the replacement of natural tissues. The compressive strengths predicted by the FEM simulations were successfully validated by comparison with experimental uniaxial compression test data, justifying the suitability of the present approach for the optimization purposes

ASSESSMENT OF COAL MINING SUBSIDENCE DAMAGE IN SOMA-TURKEY COALFIELD USING FEM MODELLING

Soma has mine subsidence problems associated with production. Therefore, property and infrastructure damage will be related with coal-mine subsidence in Soma. In this study, depending on the underground coal mine production method, damage of subsidence on energy line was determined in Soma-Turkey coalfield. Subsidence may still occur in these areas. Therefore, determining subsidence is very important. Finite element methods (FEM) and field measurements were used for determining the parameters of mechanisms. The software, Phase(2), used for the numerical modeling was developed by Rockscience Inc. The results obtained from modeling have been found to be compatible with previous studies and have been compared with actual field observation

Cerchar abrasivity index (CAI) and its relation to strength and abrasion test methods for marble stones

The Cerchar abrasivity index (CAI) is the most widely known test method for identification of rock abrasivity. The CAI value is related directly to cutter life in the field. On account of this, it is significant for building and constructions materials especially for the dimension stones. This paper presents strength tests, which are uniaxial compressive (UCS) and direct shear (DSS) influencing the CAI value. Additionally, the relationship between CAI and abrasion test methods that are Bohme abrasion (BA) and Wide-Wheel (WW) values are investigated. In the study tests were performed on 15 different marbles stone specimens. Results show that a strong correlation exists between CAI value, strength and abrasion test values. Based on this information, two converter charts were developed using multi regression analysis method. (C) 2011 Elsevier Ltd. All rights reserved