Research Paper Multiphysics modeling of arching effects in fill mass Liang Cui a , Mamadou Fall b,⇑ a Department of Civil Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, ON K1N 6N5, Canada b Department of Civil Engineering, University of Ottawa, 161 Colonel By, Ottawa, ON K1N 6N5, Canada article info Article history: Received 9 June 2016 Received in revised form 12 October 2016 Accepted 27 October 2016 Keywords: Mine Cemented paste backfill Tailings Interface Multiphysics Arching abstract A numerical modeling study is conducted to assess and gain a better understanding of the arching effects of field cemented tailings backfill (CTB). An integrated multiphysics model is developed that can illustrate and capture the changes in the material properties of CTB, consolidation behavior of CTB mass, and the shear behavior at the CTB/Rockwall interface. The predictive capability of the model has been successfully verified with comparisons of the predicted results with monitoring data taken from a series of field stud- ies. The model is then used to simulate a series of applications that are relevant to CTB in practice. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Soil arching, a phenomenon commonly encountered in geotech- nical engineering, was described by Terzaghi [1] as ‘‘one of the most universal phenomena encountered in soils both in the field and in the laboratory”. He defined the arching effect as the transfer of pressure from a yielding mass of soil onto the adjoining station- ary parts [1]. Soil arching, which involves load transfer and stress redistribution, should be and has been taken into account in the analysis of many geotechnical issues [2], such as earth pressure on retaining walls [e.g., [3,4]], vertical stress and support require- ments above tunnels and other underground situations [e.g., [2,5]], and mine tailings backfilling [e.g., [6,7]]. Assessing the arching effects of mine cemented tailings fill or backfill (CTB) is a complex task due mainly to the changing properties of the CTB medium and the complex coupled thermal (T; e.g., temperature, heat transfer), hydraulic (H; e.g., pore water pressure (PWP), suction, fluid flow), mechanical (M; e.g., stress, deformation, strength) and chemical (C; e.g.; binder chemical reac- tion) processes that occur in CTB and their effect on its geotechni- cal behavior [8,9]. CTB is essentially made of tailings (human-made soils; that is, materials that remain after minerals of value are removed), binder (e.g., Portland cement, blast furnace slag, fly ash), and water. After preparation and placement, the hardening CTB must satisfy certain requirements of mechanical stability to ensure a safe working environment for underground mining per- sonnel. To assess the in-situ mechanical performance of CTB under static loading condition, the uniaxial compressive strength (UCS) of hardened CTB is often adopted in practice [8]. Based on previous studies on CTB [10,11], it has been found that the curing stress (mechanical factor), temperature (thermal factor), suction associ- ated with moisture content (hydraulic factor) and binder type and chemistry (chemical factor) (i.e., the coupled THMC processes) largely govern the UCS development. Moreover, to prevent the CTB from flowing into the active mining zone, retaining structures (called barricades or bulkheads) are commonly constructed in the drawpoints (access points at the base of the stopes). It is critical that the horizontal pressure or stress developed by the CTB is not greater than the resistance of the retaining structure because its failure can have drastic work safety consequences and significant financial ramifications [8,12]. Therefore, an understanding of the stress development and distribution in CTB structures is critically important for the optimal geotechnical design of CTB structures and barricades. Field investigations [e.g., [13,14]] have previously confirmed that the vertical stress in the CTB is significantly less than the overburden stress due to the arching effect, which primarily results from the consolidation process of the CTB, and the improvement of CTB/rockmass interface properties with binder hydration. The consolidation of the CTB results in the development of settlement and effective (horizontal) stresses, thus enabling shear stresses to develop at the CTB-rock interface [6]. As a result, the stress in the CTB will be redistributed and the vertical stress http://dx.doi.org/10.1016/j.compgeo.2016.10.021 0266-352X/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: mfall@uottawa.ca (M. Fall). Computers and Geotechnics 83 (2017) 114–131 Contents lists available at ScienceDirect Computers and Geotechnics journal homepage: www.elsevier.com/locate/compgeo