Analytical Solution for Stress Distribution in Cementitious Backfills Considering Stope Inclinations

Öz

To enhance stope stability and decrease surface waste disposal, fill is used in underground mines. Moreover, the cementitious fill is used as a structural support element for maximizing the extraction ratio of run-of-mine ore in irregularly shaped orebodies. Assessing the stress distribution within the fill and neighboring rock mass is of great importance to the design of backfilled stopes. Inappropriate design of these stopes can cause the backfill failures, thus resulting in the devastation of stope walls, production delays and even losses in ore dilution form, and security matters. Great effort has been made to acquire the stresses within vertical voids analytically, and there is a clear need for works which states the stress developed in inclined backfilled stopes. In this study, an analytical model is presented to explain the non-uniform distribution of stress in backfill on stope cross-section when the friction force between the footwall and hanging wall are not equal. Considering the force balance of the arc differential element, the stress distribution within mine fill is obtained. This model was compared with the existing model. It has been demonstrated analytically that the existing model underestimates the fill stress when the stope inclination becomes larger. Besides, when the surrounding mass produces a large deformation and squeezes backfill, the primary principle stress arch happens. Consequently, the outcomes of the present study will offer the knowledge needed to develop a cost-effective backfill structure in underground mines that are environmentally friendly, safe and durable.

Anahtar Kelimeler

• Cementitious Backfill
• Arching
• Minor and Major Principal Stress Arch
• Analytical Model

Stope Eğimlerini Dikkate Alan Çimentolu Dolgularda Gerilme Dağılımı İçin Analitik Çözüm

Öz

To enhance stope stability and decrease surface waste disposal, fill is used in underground mines. Moreover, the cementitious fill is used as a structural support element for maximizing the extraction ratio of run-of-mine ore in irregularly shaped orebodies. Assessing the stress distribution within the fill and neighboring rock mass is of great importance to the design of backfilled stopes. Inappropriate design of these stopes can cause the backfill failures, thus resulting in the devastation of stope walls, production delays and even losses in ore dilution form, and security matters. Great effort has been made to acquire the stresses within vertical voids analytically, and there is a clear need for works which states the stress developed in inclined backfilled stopes. In this study, an analytical model is presented to explain the non-uniform distribution of stress in backfill on stope cross-section when the friction force between the footwall and hanging wall are not equal. Considering the force balance of the arc differential element, the stress distribution within mine fill is obtained. This model was compared with the existing model. It has been demonstrated analytically that the existing model underestimates the fill stress when the stope inclination becomes larger. Besides, when the surrounding mass produces a large deformation and squeezes backfill, the primary principle stress arch happens. Consequently, the outcomes of the present study will offer the knowledge needed to develop a cost-effective backfill structure in underground mines that are environmentally friendly, safe and durable.

Anahtar Kelimeler

• Çimentolu Dolgu
• Kemerlenme
• Küçük ve Büyük Ana Stres Arkı
• Analitik Model

Kaynakça

1. Aubertin, M., Li, L., Arnoldi, S., Belem, T., Bussière, B., Benzaazoua, M., Simon, R. (2003). Interaction between backfill and rock mass in narrow stopes. Soil and Rock America, 1(2), 1157-1164.
2. Belem, T., Benzaazoua, M. (2008). Design and application of underground mine paste backfill technology. Geotechnical and Geological Engineering, 26(2), 147-174.
3. Brachman, R., Krushelnitzky, R. (2005). Response of a landfill drainage pipe buried in a trench. Canadian Geotechnical Journal, 42(3), 752-762.
4. Cao, S., Xue, G., Yilmaz, E., Yin, Z., Yan, F. (2020). Utilizing concrete pillars as an environmental mining practice in underground mines. Journal of Cleaner Production, 276, 123433.
5. El Mkadmi, N., Aubertin, M., Li, L. (2014). Effect of drainage and sequential filling on the behavior of backfill in mine stope. Canadian Geotechnical Journal, 51(1), 1-15.
6. Fall, M., Nasir, O. (2010). Mechanical behaviour of the interface between cemented tailings backfill and retaining structures under shear loadings. Geotechnical and Geological Engineering, 28(6), 779-790.
7. Falaknaz, N., Aubertin, M., Li, L. (2015). A numerical investigation of the geomechanical response of adjacent backfilled stopes. Canadian Geotechnical Journal, 52(10), 1507-1525.
8. Helinski, M., Fahey, M., Fourie, A. (2007). Nume-rical modelling of cemented paste fill deposition. Journal of Geotechnical and Geoenvironmental Engineering, 13(10), 1308-1319.

9. Jahanbakhshzadeh, A., Aubertin, M., Li, L. (2017). A new analytical solution for the stress state in inclined backfilled mine stopes. Geotechnical and Geological Engineering, 35(3), 1151-1167.
10. Jiang, H., Fall, M., Yilmaz, E., Yang, L., Ren, L. (2020). Effect of mineral admixtures on flow properties of fresh cemented paste backfill: Assessment of time dependency and thixotropy. Powder Technology, 372, 258-266.
11. Koohestani, B., Darban, A.K., Mokhtari, P., Darezereshki, E., Yilmaz, E., Yilmaz, E. (2020). Influence of hydrofluoric acid leaching and roasting on mineralogical phase transformation of pyrite in sulfidic tailings. Minerals, 10(6), 513.
12. Li, L., Aubertin, M. (2010). An analytical solution for the nonlinear distribution of effective and total stresses in backfilled stopes. Geotechnical and Geological Engineering, 5(4), 237-245.
13. Li, L., Aubertin, M., Belem, T. (2005). Formulation of a three-dimensional analytical solution to evaluate stresses in backfilled vertical narrow opening. Canadian Geotechnical Journal, 42(6), 1705-1717.
14. Li, L., Aubertin, M., Shirazi, A. (2010). Imple-mentation and application of a new elastoplastic model based on a multiaxial criterion to assess the stress state near underground openings. International Journal of Geomechanics, 10(1), 13-21.
15. Pirapakaran, K., Sivakugan, N. (2007). Arching within hydraulic fill stopes. Geotechnical and Geological Engineering, 25(1), 25-35.
16. Singh, S., Shukla, S., Sivakugan, N. (2011). Arching in inclined and vertical mine stope. Geotechnical and Geological Engineering, 29(5), 685-693.
17. Sivakugan, N., Widisinghe, S., Wang, Z.V. (2014). Vertical stress determination within backfilled stopes. International Journal of Geomechanics, 14(5), 1-6.
18. Sobhi, M.A., Li, L., Aubertin, M. (2017). Numerical investigation of earth pressure coefficient along central line of backfilled stopes. Canadian Geotechnical Journal, 54(1), 138-145.
19. Thompson, B.D., Bawden, W.F., Grabinsky, M.W. (2012). In situ measurements of cemented paste backfill at the Cayeli Mine. Canadian Geotechnical Journal, 49(7), 755-772.
20. Ting, C., Shukla, S., Sivakugan, N. (2011) Arching in soils applied to inclined stopes. International Journal of Geomechanics, 11(1), 29-35.
21. Ting, C.H., Sivakugan, N., Shukla, S.K. (2012). Laboratory simulation of the stresses within inclined stopes. Geotechnical Testing Journal, 35(2), 280-294.
22. Ting, C.H., Sivakugan, N., Read, W., Shukla, S.K. (2014). Analytical expression for vertical stress within an inclined mine stope with non-parallel wall. Geotechnical and Geological Engineering, 32(6), 577-586.
23. Widisinghe, S., Sivakugan, N. (2016). Vertical stress isobars for silos and square backfilled mine stopes. International Journal of Geomechanics, 16(2), 1-10.
24. Xue, G., Yilmaz, E., Song, W., Cao, S. (2019). Analysis of internal structure behavior of fiber reinforced cement-tailings matrix composites through X-ray computed tomography. Composites Part B: Engineering, 175, 107090.
25. Yan, B., Zhu, W., Hou, C., Yilmaz, E., Saadat, M. (2020). Characterization of early age behavior of cemented paste backfill through the magnitude and frequency spectrum of ultrasonic P-wave. Construction &Building Materials, 249, 118733.
26. Yang, L., Xu, W., Yilmaz, E., Wang, Q., Qiu, J. (2020). A combined experimental and numerical study on the triaxial and dynamic compression behavior of cemented tailings backfill. Engineering Structures, 219, 110957.
27. Yilmaz, E., Belem, T., Benzaazoua, M. (2013). Study of physico-chemical and mechanical cha-racteristics of consolidated and unconsolidated cemented paste backfills. Mineral Resources Management, 29(1), 81-100.
28. Yilmaz, E. (2018). Stope depth effect on field behaviour and performance of cemented paste backfills. International Journal of Mining, Reclamation, and Environment, 32(4), 273-296.