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11.
A model of wave propagation in fluid-saturated porous media is developed where the principal fluid/solid interaction mode affecting the propagation of the acoustic wave results from the conjunction of the Biot and the Squirt flow mechanism. The difference between the original Biot/Squirt (BISQ) flow theory and the new theory, which we call the reformulated BISQ, is that the average fluid pressure term appearing in the dynamic equation for a two component solid/fluid continuum is independent of squirt flow length. P-velocity and attenuation relate to measurable rock physical parameters: the Biot's poroelastic constants, porosity, permeability, pore fluid compressibility and viscosity. Modelling shows that velocity and attenuation dispersion obtained using the reformulated BISQ theory are of the same order of magnitude as those obtained using the original BISQ theory. Investigation on permeability effect on velocity and attenuation dispersion indicate that the transition zone in velocity and attenuation peak, occurring both at the relaxation frequency, shifts toward high frequency when permeability decreases. This behaviour agrees with Biot's theory prediction. 相似文献
12.
A comprehensive literature review has been carried out on existing models that characterize soil response under the impact of blast shock waves. Various models in the literature are reviewed and discussed in terms of their equations of state that account for the effect of high pressure, failure models that control the yield behaviour, and strength models that represent the effect of high strain-rates, along with a comparison of their advantages and limitations. Then, the application of different soil models to blast-induced liquefaction is elucidated and compared. Consequently, this review provides a comprehensive understanding of the fundamental and unique aspects of modelling soil response subjected to such transient impulsive loading on the grounds of increasing global interest in blast response of soils. 相似文献
13.
Tailings backfill, which is a subsurface fill mass, has been extensively utilized worldwide in underground mines to fill mined-out cavities for the purposes of ground control and tailings disposal. Just after placement, very early-age backfill which commonly contains a large volume of water exhibits little or no interparticle bonding, and is subjected to the risk of liquefaction induced by routine mine blasting. In this study, a modified total-stress viscoplastic cap model is developed to investigate the blast-induced liquefaction susceptibility of very early-age fill mass under various practical backfilling and field conditions. The developed model well represents the strain-rate and fluid-compressibility dependence of nonlinear material behavior under such dynamic conditions, and also captures the development of excess pore pressure due to irrecoverable volume changes. The model is validated against a series of blast and impact tests on saturated natural soils (sand and silt) and tailings fill masses, and a good agreement is found between the experimental and simulated results. Subsequently, the model is applied to investigate the effects of drainage conditions, distance from detonation, stope size, location of retaining structure, and blast sequence on the liquefaction susceptibility of early-age fill mass after mine blasting. The results obtained from the study will provide practical insight into the blast liquefaction potential of backfill mass in field conditions. 相似文献
14.
Coupled Modeling of Temperature Distribution and Evolution in Cemented Tailings Backfill Structures that Contain Mineral Admixtures 总被引：1，自引：0，他引：1
Cemented paste backfill (CPB, a mixture of tailings, water and binder) is widely utilized to fill underground mine voids. To achieve a good, economical performance, one approach is to proportionally use mineral admixtures such as fly ash and slag as partial substitutes for Portland cement. Binder hydration is one of the most significant factors that can generate heat within hydrating CPB structures, which in turn, influences the mechanical and hydraulic properties of CPB, as well as the pore structure within CPB. However, the temperature evolution due to the hydration of Portland cement that contains fly ash or slag is different from that of hydration with solely Portland cement. Hence, in consideration of the heat generated by both binder hydration and transferred between CPB and its surrounding media, a numerical model is developed to predict and determine the temperature development within CPB that contains mineral admixtures. After that, data from field and laboratory studies are employed to validate the developed model. The validation results demonstrate a good consistency between the model and the field and laboratory studies. Consequently, the proposed model is applied to simulate and determine the temperature evolution with time via mineral admixtures, binder content, initial rock and CPB temperatures, stope geometry, backfilling rate, curing time and backfilling strategy. The obtained results will contribute to better designs and preparation of CPB mixtures, as well as predict the temperature distribution within CPB structures. 相似文献
15.
A coupled chemo‐viscoplastic cap model for simulating the behavior of hydrating cemented tailings backfill under blast loading 
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下载免费PDF全文 Although the use of blasting has become a routine in contemporary mine operations, there is a lack of knowledge on the response of cement tailings backfills subjected to sudden dynamic loading. To rationally describe such a phenomenon, a new coupled chemo‐viscoplastic cap model is proposed in the present study to describe the behavior of hydrating cemented tailings backfill under blast loading. A modified Perzyna type of visco‐plasticity model is adopted to represent the rate‐dependent behavior of the cemented tailings backfill under blast loading. A modified smooth surface cap model is consequently developed to characterize the yield of the material, which also facilitates hysteresis and full compaction as well as dilation control. Then, the viscoplastic formulation is further augmented with a variable bulk modulus derived from a Mie–Gruneisen equation of state, in order to capture the nonlinear hydrostatic response of cemented backfills subjected to high pressure. Subsequently, the material properties required in the viscoplastic cap model are coupled with a chemical model, which captures and quantifies the degree of cement hydration. Thus, the behavior of hydrating cemented backfills under the impact of blast loading can be evaluated under any curing time of interest. The validation results of the developed model show a good agreement between the experimental and the predicted results. The authors believe that the proposed model will contribute to a better understanding of the performance of cemented backfills under mine blasting and contribute to evaluating and managing the risk of failure of backfill structures under such a dynamic condition. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
16.
Modelling blue and green water availability under climate change in the Beninese Basin of the Niger River Basin,West Africa 下载免费PDF全文
下载免费PDF全文 Djigbo Félicien Badou Bernd Diekkrüger Evison Kapangaziwiri Mamadou L. Mbaye Yacouba Yira Emmanuel A. Lawin Ganiyu T. Oyerinde Abel Afouda 《水文研究》2018,32(16):2526-2542
The aim of this study was to quantify climate change impact on future blue water (BW) and green water (GW) resources as well as the associated uncertainties for 4 subbasins of the Beninese part of the Niger River Basin. The outputs of 3 regional climate models (HIRHAM5, RCSM, and RCA4) under 2 emission scenarios (RCP4.5 and RCP8.5) were downscaled for the historical period (1976–2005) and for the future (2021–2050) using the Statistical DownScaling Model (SDSM). Comparison of climate variables between these 2 periods suggests that rainfall will increase (1.7% to 23.4%) for HIRHAM5 and RCSM under both RCPs but shows mixed trends (?8.5% to 17.3%) for RCA4. Mean temperature will also increase up to 0.48 °C for HIRHAM5 and RCSM but decrease for RCA4 up to ?0.37 °C. Driven by the downscaled climate data, future BW and GW were evaluated with hydrological models validated with streamflow and soil moisture, respectively. The results indicate that GW will increase in all the 4 investigated subbasins, whereas BW will only increase in one subbasin. The overall uncertainty associated with the evaluation of the future BW and GW was quantified through the computation of the interquartile range of the total number of model realizations (combinations of regional climate models and selected hydrological models) for each subbasin. The results show larger uncertainty for the quantification of BW than GW. To cope with the projected decrease in BW that could adversely impact the livelihoods and food security of the local population, recommendations for the development of adequate adaptation strategies are briefly discussed. 相似文献
17.
Cemented paste backfill (CPB) is a mixture of dewatered tailings, hydraulic binders and water. In addition to contributing to the stability of mine workplaces, CPB greatly benefits the environment by minimizing surface tailings disposal. Hence, it has become one of the most commonly used ways in mine backfilling around the world. Temperature can significantly affect the mechanical properties of cemented backfill. A source of heat in CPB is produced by binder hydration. Hence, a FLAC based numerical model is developed to predict and analyse the heat developed by hydrating CPB structures. To validate the model, results of the developed model are compared with three case studies (mathematical, laboratory, and field investigations). The validation results show a good agreement between the developed model and these cases. The effects of stope geometry, thermal properties of both rock and CPB, filling rate, binder content and initial boundary conditions are also investigated. 相似文献
18.
Kristie L. Ebi Jonathan Padgham Mamadou Doumbia Alpha Kergna Joel Smith Tanveer Butt Bruce McCarl 《Climatic change》2011,108(3):423-436
This study was undertaken to assess the potential impacts of climate change on agriculture in the Sikasso region of southern
Mali, as part of an effort by the U.S. Agency for International Development (USAID) to integrate climate change adaptation
considerations into their development projects. The region is considered to be the breadbasket of Mali, providing a substantial
amount of the country’s food supplies as well as cotton for exchange earnings. The project had two components: modeling how
climate change could affect production of cereal and cash crops in southern Mali; and conducting a stakeholder-driven vulnerability
and adaptation assessment to identify potential options for addressing current and projected risks to agriculture from climate
change. Projected changes in crop yields were based on a previous analysis that was extended for the purposes of this study.
The projections suggested that the sensitivity of maize to changing weather conditions is relatively small (generally less
than 10% change) under both dry and wet scenarios in 2030 and 2060. White (Irish) potatoes, the primary cash crop, are the
most sensitive to changing weather conditions, with yields decreasing under both dry and wet conditions; yields could decrease
by about 25% by 2060. Stakeholder workshops, field interviews, and an expert analysis were used to assess current and future
climate-related vulnerability and to identify potential adaptation options. The main focus of the assessment was farmers in
a village of about 3,000 people in the Sikasso region that practiced a rice-potato rotation system typical to the region.
The farmers emphasized adaptation measures that require outside financial and technical assistance, for example installation
of a water gate that would retain more water in the inland valley and increase the water table to flood rice fields during
the rainy season and for furrow irrigation of potatoes during the dry season. Adaptations emphasized by both the farmers and
representatives of regional technical services were crop diversification and germplasm improvement; soil and water management;
access to equipment (plows, carts, oxen, and improved stoves); credit stockage villageois (CSV); and fertilizer. 相似文献
19.
Coupled Behavior of Cemented Paste Backfill at Early Ages 总被引：1，自引：1，他引：0
20.
Alainachi Imad Fall Mamadou Majeed Muslim 《Geotechnical and Geological Engineering》2022,40(9):4735-4759
Geotechnical and Geological Engineering - Cemented paste backfill (CPB), a man-made soil undergoing cementation, is extensively applied to support underground mine openings or spaces and provide... 相似文献