Experimental Study on Direct Tensile Properties of Cemented Paste Backfill

Lijie Guo,Yue Zhao,Guoxing Tang,Guangsheng Liu,Andrew Pan,Xiaopeng Peng

doi:10.3389/fmats.2022.864264

Abstract

Cemented paste backfill (CPB) has been increasingly utilized in mines for efficient mineral obtaining and regional ground support. To guarantee the work performance, the mechanical properties of CPB have long been a topic of study among researchers. But the research progress on the tensile strength of CPB is limited, mainly because of the lack of an appropriate test method due to the low tensile strength of CPB. Therefore, instead of the conventional splitting indirect tensile strength test method, a new direct tension test method, which utilizes the specifically designed compression to tension load converter (CTLC) and dog-bone-shaped specimen, has been applied to study the direct tensile properties of CPB. In this study, the direct tensile strength (DTS) of 47 CPB mix designs were measured using CTLC, and the unconfined compressive strength (UCS) of the corresponding mix design was also tested. The experimental results showed that the increase in the binder content, solid mass content, and curing period led to higher CPB direct tensile strength, and the DTS of CPB was most sensitive to the binder content. Furthermore, the influence of the slurry mass solid content on the tensile strength of CPB was not linear. The influence of the binder content became increasingly notable with the increase in the solid content, especially if the binder content exceeded 75%. The effect of the curing period was found to be rather marginal due to the decreasing amount of un-hydrated cementitious materials left with the increase of the curing period. Overall, the DTS generated using dog-bone specimens and the CTLC apparatus are valid for better mine backfill designs. Finally, a linear correlative between UCS and DTS with a formula in the form of σDT (DTS) = 0.171 σc (UCS) was obtained, and the correlation was sufficient for further calculation of DTS using measured UCS.

Highlights

Mining with backfill, which utilizes solid mine wastes to manage and backfill mined-out stopes, has become a well-accepted method for efficient mineral obtaining and regional ground support (Grice, 1998; Belem and Benzaazoua, 2004; Jahanbakhshzadeh et al, 2017)
The tensile strength may only account for 20–30% of compressive strength (Komurlu et al, 2007; Fall et al, 2010), in many cases, such as in cut and fill mining or the large exposure of primary cemented paste backfill (CPB) during the ore mining of a secondary stope, the tensile strength is the key factor resulting in the failure of a cemented body (Yu, 1992)
The average value of three successful tests will be used as the direct tensile strength of each mix design

Summary

Introduction

Mining with backfill, which utilizes solid mine wastes to manage and backfill mined-out stopes, has become a well-accepted method for efficient mineral obtaining and regional ground support (Grice, 1998; Belem and Benzaazoua, 2004; Jahanbakhshzadeh et al, 2017). The cemented paste backfill (CPB), a kind of the backfill method, has been increasingly utilized in mines across the world (Benzaazoua et al, 2008; Thompson et al, 2012). After days of binder hydration, the Direct Tensile Properties of CPB cemented backfill body can acquire adequate strength and provide a stable platform for mining the stage (le Roux, et al, 2005; Rankine and Sivakugan, 2007). The tensile strength may only account for 20–30% of compressive strength (Komurlu et al, 2007; Fall et al, 2010), in many cases, such as in cut and fill mining or the large exposure of primary CPB during the ore mining of a secondary stope, the tensile strength is the key factor resulting in the failure of a cemented body (Yu, 1992). It is necessary to precisely measure and analyze the tensile strength of CPB

Objectives

Methods

Results

Conclusion