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Geomechanics and Engineering Volume 13, Number 2, August 2017 , pages 333-352 DOI: https://doi.org/10.12989/gae.2017.13.2.333 |
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Comparative study on dynamic properties of argillaceous siltstone and its grouting-reinforced body |
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Ming Huang, Chao-Shui Xu, Jin-Wu Zhan and Jun-Bao Wang
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| Abstract | ||
| A comparison study is made between the dynamic properties of an argillaceous siltstone and its grouting-reinforced body. The purpose is to investigate how grout injection can help repair broken soft rocks. A slightly weathered argillaceous siltstone is selected, and part of the siltstone is mechanically crushed and cemented with Portland cement to simulate the grouting-reinforced body. Core specimens with the size of 50 mm × 38 mm are prepared from the original rock and the grouting-reinforced body. Impact tests on these samples are then carried out using a Split Hopkinson Pressure Bar (SHPB) apparatus. Failure patterns are analyzed and geotechnical parameters of the specimens are estimated. Based on the experimental results, for the grouting-reinforced body, its shock resistance is poorer than that of the original rock, and most cracks happen in the cementation boundaries between the cement mortar and the original rock particles. It was observed that the grouting-reinforced body ends up with more fragmented residues, most of them have larger fractal dimensions, and its dynamic strength is generally lower. The mass ratio of broken rocks to cement has a significant effect on its dynamic properties and there is an optimal ratio that the maximum dynamic peak strength can be achieved. The dynamic strain-softening behavior of the grouting-reinforced body is more significant compared with that of the original rock. Both the time dependent damage model and the modified overstress damage model are equally applicable to the original rock, but the former performs much better compared with the latter for the grouting-reinforced body. In addition, it was also shown that water content and impact velocity both have significant effect on dynamic properties of the original rock and its grouting-reinforced body. Higher water content leads to more small broken rock pieces, larger fractal dimensions, lower dynamic peak strength and smaller elastic modulus. However, the water content plays a minor role in fractal dimensions when the impact velocity is beyond a certain value. Higher impact loading rate leads to higher degree of fragmentation and larger fractal dimensions both in argillaceous siltstone and its grouting-reinforced body. These results provide a sound basis for the quantitative evaluation on how cement grouting can contribute to the repair of broken soft rocks. | ||
| Key Words | ||
| ground reinforcement; broken soft rock; Split Hopkinson Pressure Bar; cement grouting; grouting-reinforced body; dynamic mechanical-property; cement grouting | ||
| Address | ||
| (1) Ming Huang, Jin-Wu Zhan: College of Civil Engineering, Fuzhou University, Fuzhou 350108, China; (2) Ming Huang, Chao-Shui Xu: School of Civil, Environment and Mining Engineering, the University of Adelaide, Adelaide 5005, Australia; (3) Jun-Bao Wang: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China. | ||