This page has only limited features, please log in for full access.

Dr. Mohammed Hefni
King Abdulaziz University

Basic Info


Research Keywords & Expertise

0 Cement
0 Mine Closure
0 Mining
0 Tailings
0 Backfill Mechanics

Fingerprints

Mining
Cement
mine backfill
Tailings

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Journal article
Published: 31 May 2021 in Sustainability
Reads 0
Downloads 0

The Kingdom of Saudi Arabia covers an area of approximately 2 million km2 and is rich in natural resources that are necessary for industrial development. The estimated mineral wealth beneath the Kingdom’s soil is approximately USD 1.33 trillion, as reported by the Ministry of Industry and Mineral Resources. The Kingdom’s vision for 2030 is to develop the mining sector to become the third pillar of the domestic economy. Therefore, exploration and mining activities are expected to accelerate over the next decade, which will lead to increased waste production. New executive regulations issued in January 2021 contain several sustainable elements related to the environment, social responsibility, and occupational health and safety. Therefore, this study aims to promote an example of sustainable mining activities in the Kingdom that could be adapted to meet the regulatory requirements. Cemented paste backfill samples of varying composition were made with waste materials from a Saudi copper mine for re-injection into underground mining cavities to minimize waste exposure to the environment. The samples were tested for unconfined compressive strength (UCS) after 7, 14, 28, 56, and 90 days of curing. Results from a statistically designed experiment technique show that the samples developed sufficient strength to be used in mine backfilling applications. Strong negative relationships were detected between the UCS and the water-to-binder ratio. There is strong potential for mine backfill technology to be applied to a wide range of Saudi Arabian mines to enhance the sustainability of the mining sector.

ACS Style

Mohammed Hefni; Hussin Ahmed; Ebaa Omar; Maaz Ali. The Potential Re-Use of Saudi Mine Tailings in Mine Backfill: A Path towards Sustainable Mining in Saudi Arabia. Sustainability 2021, 13, 6204 .

AMA Style

Mohammed Hefni, Hussin Ahmed, Ebaa Omar, Maaz Ali. The Potential Re-Use of Saudi Mine Tailings in Mine Backfill: A Path towards Sustainable Mining in Saudi Arabia. Sustainability. 2021; 13 (11):6204.

Chicago/Turabian Style

Mohammed Hefni; Hussin Ahmed; Ebaa Omar; Maaz Ali. 2021. "The Potential Re-Use of Saudi Mine Tailings in Mine Backfill: A Path towards Sustainable Mining in Saudi Arabia." Sustainability 13, no. 11: 6204.

Research article
Published: 06 March 2021 in Advances in Civil Engineering
Reads 0
Downloads 0

The effectiveness of mine backfilling depends on the properties of its constituents. The high cost of cement, which is commonly used as a binder in mine backfill, has led researchers to seek alternatives to partially replace it with other binders. This study investigated the potential to use nano-calcium carbonate (NCC) and natural pozzolans (zeolite and pumice) along with Portland cement (PC) in mine backfill. Two types of experimental samples were prepared: (1) gold tailings and silica sand to investigate the effect of NCC and (2) nickel tailings to investigate the effect of natural pozzolans. The unconfined compressive strength (UCS) was measured for samples cured for up to 56 days. Moreover, selected samples were subject to mercury intrusion porosimetry to investigate microstructural properties. Results show that addition of NCC did not improve the UCS of backfill prepared with gold tailings and cured for 28 days, whereas a dosage of 1% NCC in backfill samples prepared with silica sand improved UCS by 20%, suggesting that the gold tailings negatively affected strength development. Natural pozzolans, in particular, 20% zeolite, had 24% higher UCS after 56 days of curing compared to samples prepared with PC and thus have the potential to partially replace cement in mine backfill.

ACS Style

Mohammed Hefni; Maaz A. Ali. The Potential to Replace Cement with Nano-Calcium Carbonate and Natural Pozzolans in Cemented Mine Backfill. Advances in Civil Engineering 2021, 2021, 1 -10.

AMA Style

Mohammed Hefni, Maaz A. Ali. The Potential to Replace Cement with Nano-Calcium Carbonate and Natural Pozzolans in Cemented Mine Backfill. Advances in Civil Engineering. 2021; 2021 ():1-10.

Chicago/Turabian Style

Mohammed Hefni; Maaz A. Ali. 2021. "The Potential to Replace Cement with Nano-Calcium Carbonate and Natural Pozzolans in Cemented Mine Backfill." Advances in Civil Engineering 2021, no. : 1-10.

Journal article
Published: 15 January 2021 in Minerals
Reads 0
Downloads 0

As part of an extensive research program exploring the potential benefits of using air-entraining admixtures in mine backfill, the experimental study presented in this paper investigates the effect of cement and entrained air dosages on mine backfill unconfined compressive strength (UCS), fresh density, and dry density. Backfill specimens were prepared using silica sand, normal Portland cement, water, and an entrained air admixture. An experimental design with response surface methodology was adopted to develop predictive mathematical models and analyze the results. The results demonstrated that an entrained air dosage of 3.5% could improve the UCS of the mine backfill owing to better dispersion of cement particles. However, a further increase in the dosage reduced the UCS as well as the fresh and dry densities by approximately 200 and 120 kg/m3, respectively. Study results imply that using air-entraining admixtures can potentially enhance mine backfill flowability and reduce the density, thus providing safer and more sustainable working conditions in an underground mining environment.

ACS Style

Mohammed Hefni; Ferri Hassani. Effect of Air Entrainment on Cemented Mine Backfill Properties: Analysis Based on Response Surface Methodology. Minerals 2021, 11, 81 .

AMA Style

Mohammed Hefni, Ferri Hassani. Effect of Air Entrainment on Cemented Mine Backfill Properties: Analysis Based on Response Surface Methodology. Minerals. 2021; 11 (1):81.

Chicago/Turabian Style

Mohammed Hefni; Ferri Hassani. 2021. "Effect of Air Entrainment on Cemented Mine Backfill Properties: Analysis Based on Response Surface Methodology." Minerals 11, no. 1: 81.

Research article
Published: 17 December 2020 in Experimental Results
Reads 0
Downloads 0

The use of natural pozzolans in concrete applications is gaining more attention because of the associated environmental, economic, and technical benefits. In this study, reference cemented mine backfill samples were prepared using Portland cement, and experimental samples were prepared by partially replacing Portland cement with 10 or 20 wt.% fly ash as a byproduct (artificial) pozzolan or pumice as a natural pozzolan. Samples were cured for 7, 14, and 28 days to investigate uniaxial compressive strength development. Backfill samples containing 10 wt.% pumice had almost a similar compressive strength as reference samples. There is strong potential for pumice to be used in cemented backfill to minimize costs, improve backfill properties, and promote the sustainability of the mining industry.

ACS Style

Mohammed A. Hefni. The potential use of pumice in mine backfill. Experimental Results 2020, 1, 1 .

AMA Style

Mohammed A. Hefni. The potential use of pumice in mine backfill. Experimental Results. 2020; 1 ():1.

Chicago/Turabian Style

Mohammed A. Hefni. 2020. "The potential use of pumice in mine backfill." Experimental Results 1, no. : 1.

Journal article
Published: 23 June 2020 in Minerals
Reads 0
Downloads 0

This study aims to develop a novel mine backfill material called foam mine fill (FMF). A cellular structure is achieved by incorporating a premade foam into the backfill mixture using an air-entraining agent. FMF samples were prepared with copper-nickel mine tailings and normal Portland cement. Experiments were designed to investigate the effect of binder dosage, volume of entrained air, and foam mixing time on FMF unconfined compressive strength (UCS) and dry density. Moreover, a qualitative microscopic assessment investigated the effect of foam mixing time on air bubble structure. The pore size distribution and porosity of selected samples were investigated through mercury intrusion porosimetry. Relative to reference samples without entrained air, the UCS of FMF samples was 20–50% lower. However, the concomitant lower dry density (by up to 360 kg/m3) could enhance the safety of the underground working environment, especially in underhand cut-and-fill mining where miners and machinery work beneath the backfilled stope, and lower-density fill material would minimize the adverse effects of potential backfill failure. Prolonged foam mixing time led to a significant loss in UCS and total collapse of the air bubble structure. Other potential applications for FMF are areas where there are tailings shortages and as an alternative to hydraulic fill.

ACS Style

Mohammed Hefni; Ferri Hassani. Experimental Development of a Novel Mine Backfill Material: Foam Mine Fill. Minerals 2020, 10, 564 .

AMA Style

Mohammed Hefni, Ferri Hassani. Experimental Development of a Novel Mine Backfill Material: Foam Mine Fill. Minerals. 2020; 10 (6):564.

Chicago/Turabian Style

Mohammed Hefni; Ferri Hassani. 2020. "Experimental Development of a Novel Mine Backfill Material: Foam Mine Fill." Minerals 10, no. 6: 564.

Original paper
Published: 02 March 2020 in Geotechnical and Geological Engineering
Reads 0
Downloads 0

Unplanned ore dilution negatively affects overall mine profitability by increasing operating costs (e.g., mucking, haulage, crushing, hoisting, milling, waste treatment, and low-grade ore upgrading). Eliminating ore dilution requires identifying and controlling the major causal factors, which are related to in-situ stress regimes, depth of stope undercut, ore dip/orientation, stope geometry, and quality of the host rock mass. In-situ stress regimes and depth of stope undercut were examined in a previous publication (see Part I). The results showed that the stability of the stope hanging wall significantly deteriorates when in situ stress regimes and depth of stope undercutting of the access drift increase. Conversely, the extent of plastic zones increases with such an increase. Also, the depth of stope undercutting has no impact on the deformation development of the rock mass. The objective of this paper is to assess stope hanging wall (HW) stability and ore dilution with respect to ore inclination and stope geometry in sublevel, open stoping, narrow-vein mines. A series of two-dimensional elasto-plastic numerical models was built to examine the effect of ore dip angle and stope geometry (height and width) on stope HW stability and ore dilution in a highly stressed environment (in-situ stress ratio = 2.5). The results are presented, discussed, and compared in terms of depth of relaxation zones, extent of plastic failure zones, and total displacement with respect to four stope dip angles (45°, 60°, 75°, and 85°), three stope widths (5, 7.5, and 10 m), and three stope heights (20, 30, and 40 m). Results show that stope HW stability improves when ore dip angle increases (i.e., steeply dipping ore deposits) because the depth of relaxation zones and extent of failure zones decreases. Dip angle had a negligible effect on HW deformation. Less dilution occurred at very steep (85°) inclination angles. At different ore dip angles, stope HW stability greatly deteriorated with increasing stope width and improved with decreasing stope height.

ACS Style

Mohammed Hefni; Wael R. Elrawy Abdellah; Haitham M. Ahmed. Factors Influencing Stope Hanging Wall Stability and Ore Dilution in Narrow-Vein Deposits: Part II. Geotechnical and Geological Engineering 2020, 38, 3795 -3813.

AMA Style

Mohammed Hefni, Wael R. Elrawy Abdellah, Haitham M. Ahmed. Factors Influencing Stope Hanging Wall Stability and Ore Dilution in Narrow-Vein Deposits: Part II. Geotechnical and Geological Engineering. 2020; 38 (4):3795-3813.

Chicago/Turabian Style

Mohammed Hefni; Wael R. Elrawy Abdellah; Haitham M. Ahmed. 2020. "Factors Influencing Stope Hanging Wall Stability and Ore Dilution in Narrow-Vein Deposits: Part II." Geotechnical and Geological Engineering 38, no. 4: 3795-3813.

Original paper
Published: 18 October 2019 in Geotechnical and Geological Engineering
Reads 0
Downloads 0

The sublevel open stope method is widely practiced in many Canadian mines when extracting thin tabular orebodies. This method is used as an alternative to sublevel caving when ore dilution (contamination of ore by waste rock) is an issue and where fairly competent rock exists. Dilution and instability at the stope hanging wall (HW) can significantly increase mining operation costs. Dilution reduces the ore grade and increases the amount of material that needs to be extracted and transported to the mill. Stope instability among the many factors that strongly affect ore dilution and stope stability, this paper examines in-stress regimes and depth of stope undercutting of the access drift using the Mohr–Coulomb elastoplastic failure evaluation criterion and RS2D software. Stope HW stability was assessed in terms of depth of the relaxation zones at the center of the stope HW, the extent of yield or failure zones, and deformation contours. Results reveal that the stability of the stope HW significantly deteriorates when in situ stress regimes and depth of stope undercutting increase. Conversely, the depth of relaxation zones and the extent of yield regions increase when the in situ stress and depth of stope undercutting increase. However, the depth of stope undercutting does not influence deformation developments (e.g., deformations only affected by the change in the in situ stress ratio).

ACS Style

Wael R. Elrawy Abdellah; Mohammed Hefni; Haitham M. Ahmed. Factors Influencing Stope Hanging Wall Stability and Ore Dilution in Narrow-Vein Deposits: Part 1. Geotechnical and Geological Engineering 2019, 38, 1451 -1470.

AMA Style

Wael R. Elrawy Abdellah, Mohammed Hefni, Haitham M. Ahmed. Factors Influencing Stope Hanging Wall Stability and Ore Dilution in Narrow-Vein Deposits: Part 1. Geotechnical and Geological Engineering. 2019; 38 (2):1451-1470.

Chicago/Turabian Style

Wael R. Elrawy Abdellah; Mohammed Hefni; Haitham M. Ahmed. 2019. "Factors Influencing Stope Hanging Wall Stability and Ore Dilution in Narrow-Vein Deposits: Part 1." Geotechnical and Geological Engineering 38, no. 2: 1451-1470.

Articles
Published: 13 August 2018 in Geomechanics and Geoengineering
Reads 0
Downloads 0

Stope stability is a key factor for the success of a mining operation. To optimise ore productivity while maintaining stope stability, the mining block/stope must be extracted in stages. Ore dilution will occur if the stope is not properly excavated/blasted. This study examines stope stability during mining in three stages, where the height of each stage stope is 10 m. The paper also presents simulation analysis of a typical steeply dipping tabular orebody at 1200 m depth below the surface, which is common in many Canadian underground hard rock mines. Numerical modelling analysis was conducted using the finite element program, RS2D, where the non-linear elasto-plastic Mohr-Coulomb failure criterion was adopted. The rock reinforcement system (i.e. cable bolts) was modelled/installed in the stope footwall after each mining stage to strengthen access drifts and stabilise the rock mass around the stope that was disturbed by mining activity. Results are discussed in terms of depth of failure zones, total deformation and axial forces in cable bolts with respect to mining stage.

ACS Style

Wael R. Abdellah; Haitham M. Ahmed; Mohammed Hefni. Numerical modelling of staged stope extraction in a tabular steeply dipping deposit. Geomechanics and Geoengineering 2018, 14, 41 -51.

AMA Style

Wael R. Abdellah, Haitham M. Ahmed, Mohammed Hefni. Numerical modelling of staged stope extraction in a tabular steeply dipping deposit. Geomechanics and Geoengineering. 2018; 14 (1):41-51.

Chicago/Turabian Style

Wael R. Abdellah; Haitham M. Ahmed; Mohammed Hefni. 2018. "Numerical modelling of staged stope extraction in a tabular steeply dipping deposit." Geomechanics and Geoengineering 14, no. 1: 41-51.

Journal article
Published: 01 March 2018 in Materials Science Forum
Reads 0
Downloads 0

This study is part of large and ongoing investigation into the potential use of calcium carbonate nanoparticles (NCaCO3) to improve the mechanical and physical properties of mine backfill. The investigation was conducted in two phases. In phase I, gold tailings were used to prepare backfill sample using Portland cement (PC) as the binding agent under various NCaCO3 and superplasticizer (SP) dosages. In phase II, fine silica sand was used to minimize the reactive nature of tailings, which can adversely affect uniaxial compressive strength (UCS). Samples in this phase were prepared under various NCaCO3 dosages using slag:PC weight ratios of 80:20 as the binding agent. Select samples from phase II were subjected to Mercury Intrusion Porosimetry (MIP) to compare microstructural properties before and after addition of NCaCO3. Phase I results showed that the UCS of samples containing NCaCO3 was low, even when SP was used to improve particle dispersion. Phase II samples exhibited up to 9.5% higher UCS after 28 days of curing at a NCaCO3 dosage of 6% by weight of binder. MIP results showed that samples containing NCaCO3 were less porous than the corresponding controlled silica sand backfill samples, which in turn influenced the UCS results.

ACS Style

Mohammed A. Hefni; Ferri Hassani; Mehrdad F. Kermani. An Investigation into the Potential Use of Calcium Carbonate Nanoparticles in Mine Backfill. Materials Science Forum 2018, 916, 184 -189.

AMA Style

Mohammed A. Hefni, Ferri Hassani, Mehrdad F. Kermani. An Investigation into the Potential Use of Calcium Carbonate Nanoparticles in Mine Backfill. Materials Science Forum. 2018; 916 ():184-189.

Chicago/Turabian Style

Mohammed A. Hefni; Ferri Hassani; Mehrdad F. Kermani. 2018. "An Investigation into the Potential Use of Calcium Carbonate Nanoparticles in Mine Backfill." Materials Science Forum 916, no. : 184-189.

Conference paper
Published: 01 January 2014 in Proceedings of the Eleventh International Symposium on Mining with Backfill
Reads 0
Downloads 0

This study is part of large and an ongoing investigation into the development of a light-weight and highly fluid mine fill for various applications in mining and civil operations. Foam mine fill (FMF) is the new material proposed for backfilling mines, and is fabricated by mixing stable foam into a mixture of tailings, binders, and water. This paper presents the results of a preliminary experimental study, in which FMF samples were prepared under different binder dosages, pulp densities, and amount of air entrained. FMF samples were prepared using tailings from a copper mine as the inert material, Normal Portland Cement as the main binding agent, and a foaming agent with a foam generator. Samples were cured for 28 days and subjected to unconfined compressive strength (UCS) testing. Select samples were subjected to mercury intrusion porosimetry to study the microstructural properties. An empirical model was developed using a response surface methodology to determine the optimal settings for the factors investigated, and to produce the first reference sample with a 28 day UCS value of 1 MPa.

ACS Style

Mohammed Hefni; Feramarz Hassani; Michelle Nokken; Mehrdad Kermani; Dan Vatne. Investigation into the development of foam mine fill. Proceedings of the Eleventh International Symposium on Mining with Backfill 2014, 49 -59.

AMA Style

Mohammed Hefni, Feramarz Hassani, Michelle Nokken, Mehrdad Kermani, Dan Vatne. Investigation into the development of foam mine fill. Proceedings of the Eleventh International Symposium on Mining with Backfill. 2014; ():49-59.

Chicago/Turabian Style

Mohammed Hefni; Feramarz Hassani; Michelle Nokken; Mehrdad Kermani; Dan Vatne. 2014. "Investigation into the development of foam mine fill." Proceedings of the Eleventh International Symposium on Mining with Backfill , no. : 49-59.