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The Dhaka Metropolitan Development Plan (DMDP) area in Bangladesh was considered in this investigation using 360 boreholes. This study was conducted to characterize and analyze the geotechnical properties of soil in the DMDP area to provide a better understanding of soil behavior. This research developed a database and zonation maps of the DMDP area based on the USCS soil classification, SPT-N value, bearing capacity of shallow foundation at 1.5 m and 3.0 m depth, and pile foundation at 20.0 m and 30.0 m depth. The database was created using Microsoft Excel, and ArcGIS 10.5 was used to develop geotechnical zonation maps.
The database was prepared in four steps: extraction of parameters (USCS soil Classification system, and SPT N value), standardization of SPT- N value, calculation of bearing capacity for shallow and pile foundations, and tabulation of data in Microsoft Excel.
The bearing capacity values for the shallow foundation were obtained using the Meyerhof (1974) and Bowels (1988) methods. Square footing with the size of 1.83 m X 1.83 m and depth of foundation 1.5 m and 3.0 m was used in this process. The ultimate pile capacity for cohesionless soil was calculated using Meyerhof's (1976) method. Hara et al. (1974) and Shioi & Fukui's (1982) empirical formula was used to determining the pile capacity for cohesive soil.
20 GIS-based USCS soil categorization and 20 GIS-based SPT-N_60 value zonation maps were created. The soil types from 10 places at 1.5 depth to 19.5 m depth collected from field measurements were compared with anticipated Soil classification values at the precise coordinates from the zonation maps to ascertain the correctness of the USCS classification zonation maps. 55.81% of the data matched the model-predicted USCS zonation maps. Out of 129 data, 72 matched the model-predicted soil classification. Fifteen nos. of data missed the USCS zonation map by a minimal margin. 7,200 SPT-N_60values were used to developSPT-N_60 zonation maps for 20 depth classes at 1.5m intervals reached to the depth of 30.0m from EGL. SPT-N_60 values from field measurements were compared with anticipated SPT-N_60 values at the precise coordinates from the zonation maps to assess the accuracy of the zonation maps. The root mean square error (RMSE) and coefficient of determination (R2) were 8.29 blows and 0.688, respectively. The comparison suggests a coefficient of correlation of 0.82.
Bearing capacity zonation maps of shallow foundation at 1.5 m and 3.0 m depth and pile foundation at 20.0 m and 30.0 m were created using this SPT-N_60 value. Following Meyerhof's (1974) approach, bearing capacity ranged from 1.0 ksf to 4.75 ksf at a depth of 1.5 m. 20% of the area had the bearing capacity of 1.0-2.0 ksf, 51% of the region had the bearing capacity of 2.0-3.0 ksf, 26% area had 3.0-4.0 ksf, and 3% territory had the bearing capacity of 4.0-4.75 ksf. Using Bowel's (1988) methodology, bearing capacity at a depth of 1.5 m ranged from 1.68 to 7.0 ksf. There was less than 1% of the area with a bearing capacity of 1.68 to 2.0 ksf, 20% of the region with 2.0 to 3.0 ksf, 35% of the area with 3.0 to 4.0 ksf, 27% of the territory with 4.0 to 5.0 ksf, 14% of the region with 5.0 to 6.0 ksf, and just 3% of the area with 6.0 to 7.0 ksf.At a depth of 3.0 meters, the bearing capacity ranged from 1.32 ksf to 5.65 ksf when using the methodology developed by Meyerhof (1974). 7% of the area had the bearing capacity of 1.32-2.0 ksf, 29% of the region had the bearing capacity of 2.0-3.0 ksf, 36% area had 3.0-4.0 ksf, 15% territory had the bearing capacity of 4.0-5.0 ksf and only 3% of the area with 5.0 to 5.65 ksf. According to the approach presented by Bowel (1988), the bearing capacity at a depth of 3.0 meters ranged from 2 to 8.5 ksf. 7% of the area with a bearing capacity of 2 to 3.0 ksf, 19% of the region with 3.0 to 4.0 ksf, 23% of the area with 4.0 to 5.0 ksf, 24% of the territory with 5.0 to 6.0 ksf, 21% of the region with 6.0 to 7.0 ksf, 6% of the area with 7.0 to 8.0 ksf and less than 1% of the region with 8.0 to 8.65 ksf.
In the pile capacity zonation map, at a depth of 20.0 m, pile capacity varied from 50 kip to 350 kip. Only 1.5% of the area had the pile capacity of 50-100 kip, 23% of the region had the capacity of 100-150 kip, 41% area had 150-200 kip, 23% territory had the pile capacity of 200-250 kip, 8% of the region with 250 to 300 kip, and 3.5% of the area with 300 to 350 kip.At a depth of 30 meters, the capacity of a pile ranged from 150 to 850 kip. 3.5% of the area had the pile capacity of 150-250 kip, 41% of the region had the capacity of 250-350 kip, 33% area had 350-450 kip, 11% territory had the pile capacity of 450-550 kip, 6% of the region with 550 to 650 kip, 4% region with 650-750 kip and only 1.5% of the area with 750 to 850 kip. |
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