This study is focused on the possibility of using coal mine wastes as a replacement for conventional road subgrades. Various laboratory tests carried out on fresh coal mine waste collected from Barapukuria Coal Mine (Located at Dinajpur, Bangladesh) showed that, it behaves like low strength soil with 0.71% CBR and 18.74% plasticity index which is unsuitable for engineering utilization. Later, fine sand and cement were added with the waste. Three different cement proportion were tested (5%, 8% and 10% of total weight) keeping a constant sand proportion (20% of total weight). The unconfined compression strength and CBR value were found to increase greatly. Analyzing the test results, waste mixed with 8% cement and 20% sand showing 27.44% CBR and 9.09% plasticity index was found to be effective for using as subgrade. Chemical analysis of waste detected the presence of lead as 0.026 ppm which may cause groundwater contamination.
Soft cohesive soils have low strength, high plasticity, and a large expansion ratio making them unsuitable as a road subgrade. This study aims to evaluate the potential of power plant waste (fly ash) from the Barapukuria Thermal Power Plant, Dinajpur, Bangladesh to improve the characteristics of such soft cohesive soil. X-ray fluorescence test conducted to classify the power plant fly ash and the type was identified as “Class F” according to “American Association of State Highway and Transportation Officials” and "American Society for Testing and Materials". Laboratory tests were conducted on clay soil obtained from Dinajpur region modified by the collected power plant waste. As the Class F fly ash has low cementing property, 3% cement was added with it. Cement mixed soil was modified with 5%, 10%, 15%, and 20% fly ash respectively. Specific Gravity, Atterberg limits, Modified Proctor Compaction, Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) tests were conducted. The study reveals that there is a decrease in specific gravity, dry density, and plasticity index with the addition of power plant waste. On the other hand, there is an increase in optimum moisture content, UCS, and CBR value. UCS and CBR values were found to be improved remarkably. Soaked CBR value of soil is found to be improved from 2.79% to 92.59% when treated with 5% fly ash and 3% cement. The UCS value of this modified soil was 560.36 kPa. The stabilized soil thus obtained meets the requirements for subgrade as specified by the Local Government Engineering Department (LGED)’s design manual (2005), Bangladesh. Since there is a possibility of leaching by dumping a large quantity of fly ash in the pond, the use of fly ash from the power plants to improve soft cohesive soils for road subgrade may be an environment-friendly alternative to its disposal in the ponds.
Bangladesh is one of the world's most disaster-prone areas. The northwest region of Bangladesh is the most seismically active region. Dinajpur is the district closest to the Himalayan frontal thrust, making it the most vulnerable to earthquake-related liquefaction. Therefore, the in-situ parameters are used to assess the liquefaction susceptibility of the subsurface geology for the Dinajpur district in terms of soil liquefaction safety factor (FS), the liquefaction potential index (LPI), and the liquefaction probability (PL). This study used deterministic and probabilistic techniques to estimate the liquefaction susceptibility of the area based on standard penetration test (SPT) N values. SPT data was collected at 160 different places within the study area. In an earthquake scenario with Mw = 6.5, liquefaction resistance is evaluated at each location using a 0.20g peak ground acceleration (PGA). The results of the SPT-based liquefaction assessment techniques were found to be considerably different. The soil strata prone to liquefaction in different zones of the city have been determined based on a common comparison. According to deterministic and probabilistic techniques, it has been found that, out of 160 locations, 36 and 50 sites are susceptible to liquefaction. Then, using geospatial techniques (IDW interpolation), hazard maps were created depending on the potential for liquefaction of particular locations. Finally, using an independent secondary dataset, the resulting hazard maps were validated to examine the developed approach. The obtained R2values for each regression analysis event were more than 0.79. Therefore, the produced hazard map may be utilized successfully for planning, management, and long-term development of the studied locations. Doi: 10.28991/CEJ-2022-08-07-010 Full Text: PDF
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