The Zonation Mapping of Soil Allowable Bearing Capacity for Kabul City Urban Area Using Standard Penetration Test In GIS Environment

Abstract

In this study, it was aimed to map the corrected Standard Penetration Test (SPT) values and soil allowable bearing capacity in Kabul city area. For reach to this subject, borehole test results obtained from 90 boreholes were used to model the spatial variation of N55 values and allowable bearing capacity in an area of 365 (km2). Corrections were made on reported N[1]values for depth, hammer energy, rod length, sampler and borehole diameter, to the data in hand. The zonation maps were prepared by Inverse Distance Weighted (IDW) geostatistical approach using power value (2) for depth 1.5 to 3m. This research considers the Bowles (1996) equation to evaluate the allowable bearing capacity of soil from the corrected SPT N[1]value and considering to 25mm allowable foundation settlement. The results revealed that the corrected SPT N-value (N55) ranged between 3 and 34. Based on SPT N-value zonation map, Zone-2 is the predominant at the study area comprised of silt and clay soils with N55 ranged between 7 and 14. According to allowable bearing capacity zonation map, soil allowable bearing capacity ranged between 69 and 784 (kPa) and Zone 4 with moderate allowable bearing capacity is the predominant zone and covers around half of the study area generally at the central part and the east of Pole Charkhi. With comparison between soil type distribution and allowable bearing capacity zonation map, it is concluded that variation of allowable bearing capacity at the study area highly conforms to the soil type and shallow soil conditions.