Loading rate effect on uniaxial compressive strength behavior and acoustic emission properties of cemented tailings backfill Shuai Cao a,b,⇑ , Erol Yilmaz c,⇑ , Weidong Song a,b,⇑ , Elif Yilmaz d,⇑ , Gaili Xue a,b,⇑ a School of Civil and Resources Engineering, University of Science and Technology Beijing, Beijing 100083, China b State Key Laboratory of High-Efficient Mining and Safety of Metal Mines of Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China c First Quantum Minerals Ltd., Cayeli Bakir Isletmeleri A.S., PO Box 42, Madenli, Cayeli, Rize TR53200, Turkey d Department of Mining Engineering, Karadeniz Technical University (KTU), 61080 Trabzon, Turkey highlights  Loading rate effect on cemented tailings backfill (CTB) was studied.  CTB’s uniaxial compressive strength (UCS) increases as the loading rate increases.  A power function relation between UCS value and loading rate can be defined.  Numerical simulation is very similar to the laboratory result during the UCS test. article info Article history: Received 16 October 2018 Received in revised form 18 March 2019 Accepted 8 April 2019 Keywords: Cemented tailings backfill (CTB) Uniaxial compressive strength (UCS) Loading rate effect Acoustic emission Ring counts Failure modes abstract To understand the quality and behavior of cemented tailings backfill (CTB) subjected to dynamic loads, the influence of change in the rate of loading should be accurately determined for an efficient mine fill design. In this study, the compressive strength behavior and acoustic emission (AE) characteristics of 180-day cured CTB samples are investigated by using four different loading rates: 50 N/s, 100 N/s, 150 N/s, and 200 N/s. Samples were prepared with the classified tailings and cementitious material of a gold mine as raw materials and subjected to the uniaxial compressive test using mechanical testing machine (GAW-2000) and AE equipment (PCI-2). Experimental results indicate that: (1) the loading rate has a strengthening effect on long-term strength behavior of CTB samples, and there is a power function between peak compressive strength of CTB samples and loading rate. The stress state of the backfill mass is ‘‘stepped” growth before the peak compressive strength, and the whole process displays a multi-cycle of ‘‘surge-steady-surge-steady”; (2) during the loading process, the ring count distribution has a regular peak-spacing effect, and the cumulative ring counts are also ‘‘stepped” and inclined to be stable. (3) With the increase of loading rate, the failure mode of CTB is a transition from tensile and shear mixing (mainly shear stress) to X-type shear failure. Ultimately, the essential findings of this experimental work will pro- vide a scientific reference for studying the dynamic characteristics of CTB samples. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction With the continuous depletion of shallow mineral resources, both metal and non-metallic mines around the world have steadily been transitioned to deep mining [1]. However, it is well-known that deep ore mining faces a complex environment of high ground stress and large buried depth. Thus, most mines aim achieving safe and efficient mining of deep resources [2]. Large-scale mechanized filling mining is a major trend for the development of deep mining and has been usually used for reducing the ore dilution and the mining cycle, increasing the mine productivity [3,4]. Mining with backfill can control ground pressure to achieve safe production while realizing the efficient recycle of deep ore deposit [5]. Cemen- ted backfills must maintain self-standing in the primary stope for the secure extraction of a neighboring secondary stope in the open stope mining method [6]. Cemented tailings backfill (CTB) or cemented paste backfill (CPB) is an engineered mixture of dewatered mine tailings, hydrau- https://doi.org/10.1016/j.conbuildmat.2019.04.082 0950-0618/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors at: School of Civil and Resources Engineering, University of Science and Technology Beijing, Beijing 100083, China (S. Cao, W. Song and G. Xue). E-mail addresses: sandy_cao@ustb.edu.cn (S. Cao), yilmazer@fqml.com (E. Yilmaz), songwd@ustb.edu.cn (W. Song), elifkoc@ktu.edu.tr (E. Yilmaz), B20160033@xs.ustb.edu.cn (G. Xue). Construction and Building Materials 213 (2019) 313–324 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat