Influence of Water Pressure on the Stress State in Stopes with Cohesionless Backfill

Abstract

The rapid increase of backfill use in underground mines requires a better understanding of the interaction between the fill material and the surrounding rock mass. This is a fairly complex issue as backfill materials are weak compared to the rock mass. This difference in the mechanical behavior induces a stress transfer along the contact area. Previous work conducted on backfilled trenches and mining stopes has shown that basic arching theory can be used to estimate earth pressures in narrow, vertical openings. In this regard, most existing solutions have been developed for dry backfills. However, in many cases, water is present in mine stopes, so its effect should be assessed. In this paper, the authors present a solution to evaluate the stress state in submerged or partially submerged backfilled stopes. The proposed analytical solution is validated against numerical modeling results.

Evaluation of the Stress State in Two Adjacent Backfilled Stopes Within an Elasto-Plastic Rock Mass

“…Following Li and Aubertin (2009a), the single stope is then excavated instantly and the backfill is placed in four layers after the rock region has reached stress-strain equilibrium. The stress distribution and wall convergence are monitored within the model during the excavation and filling of the second stope.…”

“…Various analytical solutions have been developed and applied to assess the stress state in single (isolated) backfilled stopes (Askew et al 1978;Hustrulid et al 1989;Aubertin et al 2003;Li et al 2003;Pirapakaran 2008). Additional studies include specific developments to analyse particular conditions such as threedimensional configurations (Winch 1999;Li et al 2005;Pirapakaran 2008), varying stresses across the stope width (Li and Aubertin 2008), and the effect of pore water pressures (Li and Aubertin 2009a). These solutions have been validated, at least in part, using numerical modelling (Li et al , 2007Pirapakaran and Sivakugan 2006;Singh et al 2011;El Mkadmi et al 2014) and experimental results (Li et al 2005;Li and Aubertin 2009b).…”

Stress Ratios in Entire Mine Stopes with Cohesionless Backfill: A Numerical Study

“…Near the center of a vertical backfilled mine stope, the K value has sometimes been associated with the at-rest earth pressure coefficient K 0 [23][24][25][26][27], whereas others have stated that the Rankine's active earth pressure coefficient K a is more representative [21,22,[28][29][30]. Recently, Yang [31] performed numerical simulations to help clarify this debated issue.…”

Stress Distribution in a Cohesionless Backfill Poured in a Silo

“…6079 succursale Centre-ville, Montreal, Quebec, H3C 3A7 Canada; Tel: 1-514-340-4711 #2408; Fax: 1-514-340-4477; E-mail: li.li@polymtl.ca conduits buried in trenches. Since then, the arching theory has been widely used in stress estimation within backfill placed in municipal trenches [6][7][8], in powder silos [2,[9][10][11], behind retaining walls [12][13][14], and in mining stope [15][16][17][18][19][20][21][22][23][24][25][26][27][28]. The occurrence of arching is also a well-known phenomenon in dam cores confined by granular soils [29], around piles driven in soft soils [30], in soft soils above a tunnel [31,32], and beneath a stockpile [33,34].…”

“…These include numerical modelling of arching effects [15,16,23] and analytical solution developments that take into account the third dimension [17][18][19]35], wall inclination [26,[36][37][38][39], pore water pressure [21,22], and non-uniform stress distribution [20,24]. Although these analytical and numerical solutions constitute useful tools in the design of civil infrastructure and mining backfill, their validity by experimental tests becomes a critical concern.…”