Stabilization of Gob-Side Entry with an Artificial Side for Sustaining Mining Work
A concrete artificial side (AS) is introduced to stabilize a gob-side entry (GSE). To evaluate the stability of the AS, a uniaxial compression failure experiment was conducted with large and small-scale specimens. The distribution characteristics of the shear stress were obtained from a numerical simulation. Based on the failure characteristics and the variation of the shear stress, a failure criterion was determined and implemented in the strengthening method for the artificial side. In an experimental test, the distribution pattern of the maximum shear stress showed an X shape, which contributed to the failure shape of the specimen. The shear stress distribution and failure shape are induced by a combination of two sets of shear stresses, which implies that failure of the AS follows the twin shear strength theory. The use of anchor bolts, bolts, and anchor bars enhances the shear strength of the artificial side. When this side is stable, the components can constrain the lateral deformation as well as improve the internal friction angle and cohesion. When the AS is damaged, the components prevent the sliding of broken blocks along the shear failure plane and improve the residual strength of the artificial side. When reinforced with an anchor bar, the AS is still stable even after mining operations for three years.
Development of a New Gob-Side Entry-Retaining Approach and Its Application
Gob-side entry retaining plays an important role in the sustainable exploitation of coal resources and has been widely used in coal mining. However; some disadvantages, such as high labour intensity and low efficiency of wall construction, have gravely restricted the application of this technique. To solve this issue, this paper developed a new gob-side entry retaining approach including a lightweight and high-strength foam concrete and a mortise-and-tenon structure hollow-block wall. The experiment results show that the preparation of foam concrete with a density of 1200 kg/m3; with uniaxial compressive strength greater than 15 MPa, can be realized by the chemical-foaming method. The method is performed by adding silica fume, slag and fly ash to a system of “cement and sand” structure collocation and by optimizing the proportioning of the materials. The density of foam concrete is reduced by 50% relative to that of common concrete which can greatly reduce the weight of the blocks. Compared with the conventional gob-side entry-retaining wall the new wall structure has many advantages. For example, it can improve stability by increasing the width-to-height ratio of the wall and save 44.44% of the material, and at the same time; it can save manpower and improve labour efficiency. Finally, the new approach was tested in the 3203 gob-side entry-retaining working face in a Chinese coal mine and the application effect proves that the new approach is well suited for entry retaining. The wall structure and parameters are reasonable. This work can contribute to the sustainable and efficient exploitation of underground coal resources.
An Optimization Approach to Occupant Safety and Fuel Economy in Vehicle Design
1. Abstract A major challenge in automotive design is the creation of safe vehicles with minimal environmental impact. This study presents a modeling framework for evaluating and optimizing body designs for improved occupant safety and fuel efficiency. Vehicle body mass is considered as the main link between safety and sustainability. The modeling framework includes frontal crash energy absorption, restraint system design and fuel economy. Preliminary results indicate a Pareto-optimal curve between safety and sustainability may exist when other factors are not taken into account. A more complete modeling framework that includes more sophisticated sustainability and safety metrics, cost and other market considerations, is suggested in order to support better design and regulatory decisions. 2. Keywords: Automotive body structures, fuel economy, occupant safety, optimal vehicle design, restraint systems