Geotechnical investigation, in hilly areas, for high-rise projects, becomes a problematic issue and costly process due to difficulties in mobilization and assembling the drilling equipment on mountainous terrains. The objective of this study is to map soil properties of study areas, especially at inaccessible sites, for reconnaissance. Digital soil maps for Tehsil Murree, Pakistan, have been developed using the emerging Geographical Information System (GIS). The research work involved the creation of an exhaustive database, by collecting and rectifying geotechnical data, followed by the digitization of the acquired data through integration with GIS, in an attempt to visualize, analyze and interpret the collected geotechnical information spatially. The soil data of 205 explanatory holes were collected from the available geotechnical investigation (GI) reports. The collection depth of soil samples, which were initially used for the design of deep and shallow foundations by different soil consultancies in the Murree area, was approximately 50 ft. below ground level. Appropriate spatial interpolation methods (i.e., the Kriging) were applied for the preparation of smooth surface maps of soil standard penetration tester number values, soil type and plasticity index. The accuracy of developed SPT N value and plasticity maps were then evaluated using the linear regression method, in which the predicted values of soil characteristics from developed maps and actual values were compared. SPT N value maps were developed up to a depth of 9.14 m below ground level and at every 1.52 m interval. The depth of refusal was considered in the developed maps. Soil type and plasticity maps were generated up to 15.24 m depth, again at every 1.52 m intervals, using color contours, considering the maximum predicted foundation depth for high-rise projects. The study has implications for academics and practitioners to map the soil properties for inaccessible sites using GIS, as the resulting maps have high accuracy.
The location of Pakistan is in a collision zone among the Eurasian and Indian plate boundaries. The geological framework of the Northwest Himalaya makes Northern Pakistan susceptible to frequent moderate to major earthquakes. The devastating earthquake of October 8, 2005 caused 87,000 deaths, 2.8 million displacements and financial loss of 200 Billion USD equivalent to 6% GDP of Pakistan. Islamabad is in seismically active region, the studies conducted for this region addresses the poor soil conditions, nonengineering construction practices and high level of seismic shaking. However, none of these studies provided readily available ground maps (top 30m time average shear wave velocity Vs30, average soil shear wave velocity Vsz & depth to bed rock Dbed rock) based on site specific geotechnical database. Vs30, Vsz & Dbed rock are important parameters for the evaluation of dynamic site characteristics of shallow bed rock sites. In Pakistan, Uniform Building Code (UBC-1997) is currently practiced, and the site classification are defined using site specific Vs30. In this study, geotechnical borehole database of 57 sites of Islamabad was collected to develop GIS based Vs30, Vsz & Dbed rock maps using Standard Penetration Test value (SPT-N). The borehole database includes, SPT-N, soil description and unit weight of soil for the Islamabad sites. In order to develop shear wave velocity (Vs) profiles, the available Vs-SPT empirical correlations were evaluated where both SPT-N & Vs measured data is available. The average of selected bounding correlations was applied to SPT-N database to develop representative Vs profiles. Using these Vs profiles, Vs30, Vsz & Dbed rock GIS based maps were developed by applying Kriging interpolation in open source QGIS software. The proposed GIS maps can be used in preliminary earthquake design for seismic resilient earthquake design in Islamabad, Pakistan.
The location of Pakistan is in a collision zone among the Eurasian and Indian plate boundaries. The geological framework of the Northwest Himalaya makes Northern Pakistan susceptible to frequent moderate to major earthquakes. The devastating earthquake of October 8, 2005 caused 87,000 deaths, 2.8 million displacements and financial loss of 200 Billion USD equivalent to 6% GDP of Pakistan. Islamabad is in seismically active region, the studies conducted for this region addresses the poor soil conditions, nonengineering construction practices and high level of seismic shaking. However, none of these studies provided readily available ground maps (top 30m time average shear wave velocity Vs30, average soil shear wave velocity Vsz & depth to bed rock Dbed rock) based on site specific geotechnical database. Vs30, Vsz & Dbed rock are important parameters for the evaluation of dynamic site characteristics of shallow bed rock sites. In Pakistan, Uniform Building Code (UBC-1997) is currently practiced, and the site classification are defined using site specific Vs30. In this study, geotechnical borehole database of 57 sites of Islamabad was collected to develop GIS based Vs30, Vsz & Dbed rock maps using Standard Penetration Test value (SPT-N). The borehole database includes, SPT-N, soil description and unit weight of soil for the Islamabad sites. In order to develop shear wave velocity (Vs) profiles, the available Vs-SPT empirical correlations were evaluated where both SPT-N & Vs measured data is available. The average of selected bounding correlations was applied to SPT-N database to develop representative Vs profiles. Using these Vs profiles, Vs30, Vsz & Dbed rock GIS based maps were developed by applying Kriging interpolation in open source QGIS software. The proposed GIS maps can be used in preliminary earthquake design for seismic resilient earthquake design in Islamabad, Pakistan.
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