Mechanical Behaviour of the Interface Between Cemented Tailings Backfill and Retaining Structures Under Shear Loads

Abstract

Understanding the shear behaviour of the interface between cemented tailings backfill and retaining wall structures (barricades, bulkheads) is important for the optimal design of barricades or bulkheads, and for mine operators to balance strength and safety against cost. However, our understanding of the shear behaviour of the aforementioned interface is limited. This paper is aimed at investigating the interfacial behaviour and properties of cemented tailings backfill-retaining wall structures, including stress-strain behaviour, cohesion, friction angle and shear stiffness through direct shear tests. Two different types of barricade or bulkhead materials (brick and concrete) are used in this study. Interface shear tests are performed at various curing times of the cemented backfill. Valuable results are obtained with regards to the interface shear behaviour of backfillretaining structures. Based on these results, interfacial properties between cemented tailings backfill and barricades or bulkheads show a significant timedependent variation.

Use of Cemented Super-Fine Unclassified Tailings Backfill for Control of Subsidence

“…In general, the most widely used model is developed based on Mitchell et al [35] in 1982 using limit equilibrium analysis. However, this model has several limitations [30]: (a) it considered the cohesion of interfaces between backfill and side wall equal to that of backfill, which is contrary to experimental results obtained from Fall and Nasir [36]; (b) it neglected the shear strength along the interfaces between backfill and side/back wall; and (c) it did not consider the surface load such as miners and equipment. Considering the abovementioned disadvantages, Li and coworkers proposed a modified Mitchell model [29] and a generalized solution [30] for calculating the required strength of backfill with a vertical exposure.…”

A modified solution to assess the required strength of exposed backfill in mine stopes

“…It is quite possible that cohesion (developed after curing for a few weeks) provides a strength that is available at lower strain in cemented backfill, but it can be expected also that the activation of shear planes should nonetheless mobilize some frictional stresses at failure along the interfaces in backfilled stopes (after the initial pore-water pressures have dissipated, which may also take a few days to a few weeks, as shown by Grabinsky (2010) andEl Mkadmi et al (2011)). This combined contribution of cohesion and friction has been observed during experimental tests conducted under drained conditions on cemented soils (e.g., Camusso and Barla 2009;Sariosseiri and Muhunthan 2009;Baxter et al 2011;Sharma et al 2011), as well as on cemented backfill (Lun 1986;Benzaazoua et al 2000;Fall and Nasir 2010). For this reason, the contribution of friction to the shear strength will be considered below.…”

“…For instance, recent results from Fall and Nasir (2010), who conducted laboratory tests on interfaces between cemented paste backfill (CPB) and rough surfaces (brick and concrete materials) under various normal stresses, have shown that the cohesion (adherence) along this interface was fairly small compared with that of the CPB (i.e., r b << 1 in eq. [5]).…”

“…Laboratory test results, including those recently obtained by Fall and Nasir (2010), tend to indicate that c b can be much smaller than c. Mitchell et al (1982) further postulated that the friction angle along the interfaces (and in the backfill) is nil, i.e., f = 0, because "cement bound strength is developed in a fully cured cemented sand at very low strains, whereas much larger strains are required to develop frictional shearing resistance." This assumption was also based on some testing results (taken from their Fig.…”

Temperature dependence of the reactivity of cemented paste backfill

“…Most of the previous studies on CPB have focused on its mechanical properties and economic advantages (less binder consumption and cost optimization) (e.g., Ghirian and Fall 2014;Wu et al, 2012;Fall and Nasir, 2010;Kesimal et al, 2005;Fall et al, 2004a,b), whereas few studies have evaluated the environmental performance of CPB by investigating its geochemical reactivity (e.g. MEM, 2006;Hamberg et al, 2015).…”