Mutaz Elamin, Dafalla Muawia, Al-Mahbashi Ahmed M, Serati Mehdi
School of Civil Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
Department of Civil Engineering, King Saud University, Riyadh 11362, Saudi Arabia.
Materials (Basel). 2024 Mar 25;17(7):1486. doi: 10.3390/ma17071486.
Solving the challenges facing the mining industry is crucial for shaping the global attitude towards clean energy technologies associated with critical minerals extracted from depth. One of these challenges is the well-known explosion-like fractures (rockbursts) or spalling failures associated with the initiation of internal cracks. To prevent such catastrophic failure, shotcrete, as a cement grout, is widely used in tunnel support applications. In areas where the tunnels are constructed within the limestone strata using tunnel boring machines (TBM), drilling, and/or blasting, millions of cubic meters of crushed limestone (CL) in powder form are extracted and landfilled as waste. Given the fact that natural sand consumption as a raw material in the construction industry exceeds previous records, recycling of such excavation material is now becoming increasingly needed. From this perspective, this study aims to utilize crushed limestone as a potentially sustainable alternative to natural sand in shotcrete applications in deep tunnels. Accordingly, several strength characterization and crack initiation determinations through various stress-strain-based models were carried out on cylindrical samples containing different proportions of crushed limestone. By increasing the crushed limestone content in the shotcrete mix, the crack initiation stress (as a measure of the in situ spalling strength) increased as well. The results suggest that the crushed limestone has good potential to replace the natural sand in the shotcrete mixture used in tunnel support applications.
解决采矿业面临的挑战对于塑造全球对与从深部开采的关键矿物相关的清洁能源技术的态度至关重要。其中一个挑战是众所周知的与内部裂缝产生相关的类似爆炸的断裂（岩爆）或剥落破坏。为防止此类灾难性破坏，喷射混凝土作为一种水泥浆，被广泛用于隧道支护应用中。在使用隧道掘进机（TBM）、钻孔和/或爆破在石灰岩地层内修建隧道的地区，数百万立方米粉末状的碎石灰石（CL）被开采出来并作为废物填埋。鉴于建筑行业作为原材料的天然砂消耗量超过以往记录，现在越来越需要对这种挖掘材料进行回收利用。从这个角度来看，本研究旨在将碎石灰石用作深部隧道喷射混凝土应用中天然砂的潜在可持续替代品。因此，对含有不同比例碎石灰石的圆柱形样品进行了基于各种应力应变模型的强度表征和裂缝起裂测定。通过增加喷射混凝土混合料中的碎石灰石含量，裂缝起裂应力（作为原位剥落强度的一种度量）也增加了。结果表明，碎石灰石在替代隧道支护应用中喷射混凝土混合料中的天然砂方面具有良好潜力。
