Evaluation of soil characteristics for determination of bearing capacity of shallow foundation based on CPT

Abstract

ABSTRACT

The purpose of this research is to estimate the bearing capacity of shallow foundation of selected areas of Kishorgonj in Bangladesh based on Cone Penetration Test (CPT) as well as Standard Penetration Test (SPT). In CPT methods, no samples can be retrieved from the site but the test is free from any human error. On the other hand, in SPT, samples both disturbed and undisturbed samples may be retrieved from the sites but SPT data is subject to human error. In this study CPT data (tip resistance, side friction and pore pressure) and SPT data (SPT N value and disturbed samples) have been collected from three locations of Kishoganj. The locations are Algapara, Austogram and Noapara. Bearing capacities for the above mentioned three locations have been estimated using CPT and SPT. In these bearing capacity estimations, three widths such as 1.5 m, 3.0m and 4.5 m have been used. Similarly, for bearing capacity estimations, three depths such as 1.5 m, 3.0m and 4.5 m have been used. Using CPT data, it has been observed that generally bearing capacity of shallow foundation increases with depths and widths. For Algapara site, the bearing capacity increases with depth until 3.0m but remains almost constant with depth below 3.0m for all widths. For Austrogram site, the bearing capacity increases with increasing depth for all widths. For Noapara site, the bearing capacity also increases with increasing depth for all widths.

Using SPT data, it has been observed that bearing capacity of shallow foundation sometimes increases and sometimes remains constant with depths and widths. For Algapara site, the bearing capacity increases with depth. For Austrogram site, the bearing capacity increases up to a depth of 3.0m and then decreases from 3.0 to 4.5m. For Noapara site, the bearing capacity remains constant with increasing depth for all widths.

For the three sites, the bearing capacity obtained from CPT is always higher than bearing capacity obtained from SPT. The ratio between bearing capacity from CPT to bearing capacity from SPT varies between 2 and 5.