1、英文原文：Numerical modeling of thawing in frozen rocks of underground mines caused by backfillingS.A. Ghoreishi-Madiseha, F. Hassanib, A. Mohammadianc, F. Abbasyba Mechanical Engineering Department, McGill University, Rm 125, Adams Bldg, 3450 University St., Montreal, QC, Canada H3A 2A7b Mining Engineer
2、ing Department, McGill University, Montreal, QC, Canada H3A 2A7c Civil Engineering Department, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5AbstractThe thawing effect due to backfilling in permafrost mining rocks is investigated. The heat transfer equation in rock and backfill is obtained by
3、 considering the effect of phase change, heat generation due to cement hydration and temperature dependent material properties. The governing equations are solved using a finite volume numerical method and the phase change phenomenon is modeled based on the manipulation of specific heat, thermal con
4、ductivity and density of rock and backfill. The harmonic mean method was employed to handle the change of thermal properties. The effects of different influential parameters such as cement content of backfill, water content of rock and backfill, thermal conductivity of rock and filling material, and
5、 the number of adjacent stopes are investigated. Eventually, using the resulting temperature and phase field, a new parameter regarded as the radius of thawing, is introduced.Keywords: Backfill; permafrost; Thaw; Finite volume; Harmonic mean method1. IntroductionMine backfilling has become an integr
6、al part of mining operations used for local or overall support for stability of mine openings or as a platform for mining activities. As a result, the physical and mechanical properties such as strength and other characteristics of Mine Filling Material (MFM) have been under keen theoretical and exp
7、erimental studies for the past three decades 1. More and more mining facilities are opening in cold regions and are subjected to extreme thermal conditions including mining in frozen environments. As the mining process goes on, extraction of material from the ground results in evacuated underground
8、spaces which are called stopes. Various sequences of stope excavations are proposed for mining entire ore bodies 1,2. As in modern bulk mining, 100% ore extraction is aimed; these stopes cannot be left empty and must be filled so the adjacent stopes can be mined eventually.During the filling operati
9、on, a huge amount of backfill material is poured into these stopes. Due to the temperature difference between the fill material and the underground cold rocks, heat is transferred from the fill to the rock causing potential thawing of the rock. In fact, the thawing decreases the mechanical strength
10、of the surrounding or adjacent rocks and it may cause the rocks to fail under in situ stresses resulting in major instability. In addition to the fill-rock temperature difference, cement hydration is another important factor which can also cause thawing. MFM is a blend of tailings, or sand, together
11、 with water and binders (small amount of cement which is usually mixed with slag to strengthen the blend).This leads to cement hydration inside MFM with heat generation occurring due to hydration. The resulting hydration heat magnifies thawing and increases the risk of damage. In order to prevent da
12、mages caused by thawing, appropriate support systems such as rock bolts are designed and implemented to strengthen the rock mass and prevent its failure. Safe design of mining excavations requires precise information about the extent of the rock mass affected by thawing, but only few studies have be
13、en devoted so far to this subject. Kaminski and Moolin3studied the effect of freezing conditions and material composition on the strength of the filling material. Hromadka and Guymon 4 compared the main approaches to the latter subject by trying to categorize various methods of modeling phase change
14、 in freezing soils. Thomas and Tart 5 performed a series of studies on freezing and thawing of soils by using a two dimensional finite element analysis. In their studies, they considered a temperature-dependent heat capacity of material which brought in the opportunity of adjusting the thermal prope
15、rties of material in accordance with experimental observations. However, due to the special characteristics of MFM such as cement hydration heat and thawing, these studies cannot precisely describe the thermal behavior of MFM. One of the few works devoted to the problem of permafrost reaction when i
16、n contact with MFM was done by Khokholov and Kurilko 6. They investigated the heat exchange occurring between the fill mass and Kimberlite stones assuming that the latent heat energy of phase change could be related to a change in specific heat capacity of the material during the phase change process. They implemented a 2D finite difference model to determine temperature field in the fill and rock masses. Also, in their approach, the convective heat transfe
