Pitwall Stability Analysis-Case Studies*

The importance of pitwall stability in design and economy of open pits has been a subject of considerable research in rock mechanics for some time now. Imperceptible slow mass movement has been a secret agent in inducing major pitwall failure. The problem is location specific and is associated with stress development, shear strength, discontinuity orientations and groundwater regimes. This paper therefore sets out to present pitwwall stability analysis in some selected pits within the Birimian environment in Ghana. Several attitude measurements were taken particularly on the footwall and along the slope face of the oxide, transition and fresh (sulphide) rock materials from some selected pits. The geologic data was subjected to the Romana’s Slope Mass Rating (SMR) analytical procedure and the pitwalls monitored through installed prisms. The oxide/ transition zones gave an SMR quantitative value of 43.1 in the footwall and 44 within the hangingwall, indicating a partial stability at 50o. The fresh rock (sulphide) gave a value of 64 in the footwall showing stability at 55o. As usual, the fresh rock was less problematic as indicated by the SMR assessment compared to the oxide and the transition materials. Creep movement was observed to predominate, being nearly 250 mm/day within the oxidised zone but lesser in the transition and fresh rocks. Induced pitwall failure pattern within the Birimian was more of composite failure (ie.,planar and toppling) capable of destabilising several pits if unchecked

Multi Source Handphone Charging System For Communication During Emergencies

Emergency situations may arise due to natural disaster occurrences or when chance takes one to a remote location. In settings like this, communication requires that mobile devices are powered on in the expectation of access to relief and rescue services. However, in many cases the electricity supply will be broke down. Usually, alternative energy sources provide the needed power to mobile phones in such circumstances. These alternative energy sources exhibit peculiar limitations that affect availability. This work was aimed at merging various alternative sources into a unit that will provide potential to a mobile phone with an emphasis on enhancing the efficiency of a hand-cranked electric dynamo source. Three power sources are employed which are active human power in the electric dynamo, solar panels and a pair of rechargeable batteries. Preliminary tests and analysis were conducted for hardware selection and assembly. The completed system contains a manual switch for the energy sources, a dc-dc regulation, battery charging electronic layout and a torchlight for illumination. An improved efficiency of 87.5% was achieved for the dynamo with the system able to deliver an average 0.4 W during operation. An average of 21 minutes elapsed before a minimum charge was delivered to a basic phone. The charging times for a smartphone to a determined level was found to be 108 minutes, 86 minutes and 72 minutes for the solar source, dynamo source and battery source, respectively. The developed unit is useful to people to keep it as a tool that they can rely on to power up their mobile phone in order to send emergency rescue message

Establishing Ground Vibration Threshold Level for Open Pit Mining Environment - A Case Study

To assess the impact of blasting activities on building structures in open pit mining districts in Ghana a study was carried out in Prestea, a township very close to the perimeter of the Plant North pit of the Bogoso GoldLtd (now Golden Star Resources Bogoso/Prestea Mines), in the Western Region of Ghana. It was observed during the study that the quality of most 'residential building structures within the Prestea township and itsenvirons were generally sub-standard. Most of the houses were in a deplorable state of disrepair with their conditions already triggering failure. Again, it was noted that no records were available to ascertain the structural state of the buildings prior to the commencement of blasting activities at the pit, necessitating the need to carry out a baseline study of buildings in nearby Himan townships for comparative analysis. It was also observed that even though management had selected 12 mm/s as its threshold for its operations in the pits only 6% of the over 542 blasts monitored over a two and half year period had ground vibration values in excess of 1.5 mm/s, with a maximum recorded value of 8 mm/s.It is recommended that management should not adopt ground vibration levels in excess of 2 mm/s for their pit operations because of the poor infrastructure within the surrounding communities. Even though this level can increase drilling and blasting costs considerably, it is considered a better option than expensive lawsuits in the likely event of any further damages that may be caused to building structures in the township

Fluoride in groundwater and its implications in west Gonja District of Ghana

Fluoride levels in groundwater may cause either enamel fluorosis or dental caries depending on their concentrations when consumed. Research has shown that an estimated 60 % of the total intake of fluoride is through drinking water (Selwitz et al, 2007). Boreholes sunk in the West Gonja district had their groundwater analyzed for fluoride. Using World Health Organisation (WHO) standard of (0.5-1. 5 mg/l) as basis, result revealed that concentration deviates from standard set by WHO. Test boreholes drilled in the communities showed three broad categorisations of fluoride levels in the groundwater as

Statistical Evaluation of Geochemical Au Sample Quality

Exploration and mining activities are based on anomalous occurrence of minerals. The basic concept governing this high risk venture is ‘no ore, no mining’. Hence, the quality of anomalous sample or its accurate determination is of great concern to exploration and mining operations. Regarding erratic mineralisation such as gold (Au), anomalous pattern of no significance whatsoever may appear in geochemical sample data as a result of poor sampling, improper sample handling or error in analytical techniques among other causes. To prevent the frequency of these occurrences, quality control checks coupled with classical statistical probe can form an integral part of the checklist to eliminate these errors. Although duplicate results have often accompanied original Au assays in most analytical reports submitted by laboratories, it is not immediately known upon what b asis the results need to be accepted or rejected. Often, some geologists accept results upon quick sight comparison. A total of three hundred and ninety (390) geochemical soil samples from the Sefwi-Bibiani belt of Ghana together with some blanks and standards were subjected to statistical analysis after following rigorous quality control sampling protocols. The statistical models employed include outlier test, distribution and correlation analysis. The original and duplicate samples were then statistically compared using simple nested One –Way Analysis of Variance (ANOVA), the Chi Square Test and the Student’s t –Test.The ANOVA and the t–Tests revealed no significant analytical error. However, the other tests indicated multimodality of the populations as well as batch effect which culminates into significant procedural error. The investigation concludes that these systematic procedural errors if unchecked could mask true geochemical distribution

Comparison of Five Advanced Oxidation Processes for Degradation of Pesticide in Aqueous Solution

The study compared the technical efficiency and economic cost of five advanced oxidation processes (Fenton, UV photo-Fenton, solar photo-Fenton, UV/TiO2/H2O2 and FeGAC/H2O2) for degradation of the pesticides chlorpyrifos cypermethrin and chlorothalonil in aqueous solution. The highest degradation in terms of COD and TOC removals and improvement of the biodegradability (BOD5/COD ratio) index (BI) were observed to be (i) Fenton - 69.03% (COD), 55.61% (TOC), and 0.35 (BI); (ii) UV photo-Fenton -78.56% (COD), 63.76% (TOC) and 0.38 (BI);  (iii) solar photo-Fenton - 74.19% (COD), 58.32% (TOC) and 0.36 (BI); (iv) UV/TiO2/H2O2 - 53.62% (COD), 21.54% (TOC), and 0.26 (BI); and  (v) the most technical efficient and cost effective process was FeGAC/H2O2. At an optimum condition (FeGAC 5 g/L, H2O2 100 mg/L, and reaction time of 60 min at pH 3), the COD and TOC removal efficiency were 96.19 and 85.60%, respectively, and the biodegradation index was 0.40. The degradation rate constant and cost were 0.0246 min-1 and $0.74/kg TOC, respectively. The FeGAC/H2O2 process is the most technically efficient and cost effective for pretreatment of the pesticide wastewater before biological treatment.

Effect of Graded Oil Palm Kernel Shells on Compaction of Weak o Problematic Sub-Grade Soils

AbstractSub-grade is the ultimate load bearer of vehicular traffic load in a pavement structure. A weak sub-grade or problematic soils require some improvements like soil stabilisation, soil reinforcement and/or capping of the sub-grade layer. These sub-grade improvement methods increase the total project cost because non-local materials such as cement, geosynthetics and hydrated lime are commonly used. The use of graded oil palm kernel shells (OPKS) which are local, cheaper and readily available as a soil improvement material was assessed in this research. This assessment was done by mixing sub-grade material with 2.8 mm, 5 mm and 10 mm graded OPKS. 10 %, 20 % and 30 % of each graded OPKS was added separately to the soil to form nine composite materials. These composite materials including the natural soil were tested for their California Bearing Ratio (CBR) values. The investigation proved that the composite made of 20 % 2.8 mm graded OPKS yielded a soaked CBR of 23.5 % which is a 197.47 % increase in soaked CBR compared to that of the natural soil. The soaked CBR samples of the graded OPKS composite materials absorbed lesser amounts of water in comparison to that of the natural soil. This behaviour implies that some capillary force created at un-soaked condition in the composite materials was preserved; therefore, the composite materials generally have higher CBR values than the natural soil. Keywords: Oil Palm Kernel Shells (OPKS), Problematic Soils, Lightweight Aggregate (LWA

Perfecting Rural Land Title for Wealth Creation and Sustainable Development

AbstractPerfecting land title refers to the process of securing tenure on land. It refers to the assurance that the land one holds for an agreed period of time and purpose is certain. It requires a level of legitimacy. It is on record that agriculture, forestry and mining sectors constitute about 70% of Ghana’s gross domestic product. However, the lack of several large-scale plantations in Ghana can be partly attributed to the land tenure system. Land rights in rural communities are not secured in that the lands are not themselves well defined and rights are not documented. The study used modern survey methods to clearly map out farms in a systematic manner for farmers under a cooperative for rubber plantation development. The rights of tenant farmers and landholders are clearly and legally documented and registered into the formal land administration system. The spatial and attribute data are incorporated into a Geographic Information System (GIS) that serves as tool for data management on the farmers. The pilot study was successful in improving not only tenure security and data access, but also access to funding by participating farmers. Keywords: Land Tenure Security, Registration, Spatial Data, Attribute Dat

Product Marking and Conformity Assessment of Portland Cements on the Ghanaian Market

Cement bound concrete materials and complementary fittings are requisite ingredients for all civil engineering works. In all these, Portland cement, a basic binding ingredient for the concrete work is the dominant binder. In Ghana, there are various brands of cement on the market. Five major brand products currently in circulation include the Ghana Cement (GHACEM), Western DIAMOND Cement (DIAMOND), CIMAF Cement, DANGOTE Cement and SUPACEM Cement. Increased infrastructural development has placed high demand on cement consumption. Consequently, new products keep emerging in the market. Indeed, a standard measure to provide product marking and evaluations of conformity to standard Class thresholds are required for the desired specification, properties and the performance quality of the cement products. This research therefore sets to ascertain the strength quality of the five cement brands on the Ghanaian market by checking their conformity to C-30 and C-40 standard compressive tests, using their 32.5-R and 42.5-R flagship brands. To achieve this, concrete cubes were moulded with fixed mix ratio of 1:1⅟2:3 and 1:1:2 for C-30 and C-40 respectively. To achieve the desired strength conformity, the slump as well as the coarse and fine aggregate constituents were standardised. The results indicated that the cement brands despite parading same strength thresholds in the market, do not exhibit same strength build-up. There are significant variations in growth of compressive strength over time. It was observed also that conformance threshold within 28 days was not attained for a number of the brands. Indeed, not until 56 days or more some of the brands could not achieve their desired compressive strength thresholds

Comparison of Five Advanced Oxidation Processes for Degradation of Pesticide in Aqueous Solution

The study compared the technical efficiency and economic cost of five advanced oxidation processes (Fenton, UV photo-Fenton, solar photo-Fenton, UV/TiO2/H2O2 and FeGAC/H2O2) for degradation of the pesticides chlorpyrifos cypermethrin and chlorothalonil in aqueous solution. The highest degradation in terms of COD and TOC removals and improvement of the biodegradability (BOD5/COD ratio) index (BI) were observed to be (i) Fenton - 69.03% (COD), 55.61% (TOC), and 0.35 (BI); (ii) UV photo-Fenton -78.56% (COD), 63.76% (TOC) and 0.38 (BI);  (iii) solar photo-Fenton - 74.19% (COD), 58.32% (TOC) and 0.36 (BI); (iv) UV/TiO2/H2O2 - 53.62% (COD), 21.54% (TOC), and 0.26 (BI); and  (v) the most technical efficient and cost effective process was FeGAC/H2O2. At an optimum condition (FeGAC 5 g/L, H2O2 100 mg/L, and reaction time of 60 min at pH 3), the COD and TOC removal efficiency were 96.19 and 85.60%, respectively, and the biodegradation index was 0.40. The degradation rate constant and cost were 0.0246 min-1 and $0.74/kg TOC, respectively. The FeGAC/H2O2 process is the most technically efficient and cost effective for pretreatment of the pesticide wastewater before biological treatment. Copyright © 2018 BCREC Group. All rights reserved Received: 26th July 2017; Revised: 26nd September 2017; Accepted: 27th September 2017; Available online: 22nd January 2018; Published regularly: 2nd April 2018 How to Cite: Affam, A.C., Chaudhuri, M., Kutty, S.R.M. (2018). Comparison of Five Advanced Oxidation Processes for Degradation of Pesticide in Aqueous Solution. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (1): 179-186 (doi:10.9767/bcrec.13.1.1394.179-186