Effect of suction on the mechanical behaviour of iron ore rock

Abstract

The effect of suction on the behaviour of iron ore has been studied from both physical and mechanical points of view. The porosity and the suction phenomena have been analysed using different experimental techniques. Uniaxial compressive tests on partially saturated samples have shown that the suction is responsible for strength and cohesion improvement. Considering the theory of partially saturated porous soils of Coussy and Dangla (Me´canique des sols non sature´s (2002 edn). Herme`s Science: 2002; 390), we have proposed a constitutive law for partially saturated iron ore. The real increase in the apparent cohesion due to the capillary attraction forces is overestimated if the yield function is written in terms of effective stresses. The effect of the capillary cohesion has been modelled with a function in the expression of the apparent cohesion of the yield function. The effect of suction on the mechanical behaviour has been represented in the effective stresses space and in the total stresses space like the Alonso model (Ge´otechnique 1990; 40:405-430).

Water effects on rock strength and stiffness degradation

“…The results show that the water content of the rocks stored in the humidity room is much less than that in those immersed in water even after a long period of time. An explanation of this phenomenon was given by Grgic et al [24]. As suggested in the above review, although water content may be expressed unambiguously as ''mass of water per unit mass of rock'' [27], different researchers may have determined the dry mass and wet mass by different methods and under different conditions.…”

Creep of a porous rock and associated acoustic emission under different hydrous conditions

“…However there is a lack of studies on time‐dependent behavior of rocks under partially saturated conditions in which water vapor pressure is well controlled. For iron ore, a very porous silicate rock, its short‐term mechanical behavior has been characterized under saturated [ Grgic et al , 2003] and partially saturated [ Grgic et al , 2005] conditions, and its time‐dependent deformation behavior has been studied under saturated conditions [ Grgic et al , 2003]. In this paper, we focus on the time‐dependent behavior of iron ore in the partially saturated domain and on the consequences of immersion in water during creep tests.…”

Modelling of the drying and flooding of underground iron mines in Lorraine (France)

“…The full discussion is given in a companion paper [9]. In this paper, we have also discussed the validity of the effective stress principle in a failure criterion and proposed a constitutive model for partially saturated iron ore that takes into account the effect of the capillary pressure on the strength of iron ore.…”

“…Indeed, the hydro-mechanical equilibrium can only be reached after a very long delay because of the propagation kinetic of the initial desaturation governed by the diffusion Eqs. (9)(10)(11).…”

“…Grgic et al [9] have justified the use of this expression of the effective stress for partially saturated porous media, rather than that of Gray and Schrefler [10], which is based on the Bishop formulation [11].…”