Abstract:
Islamabad, the capital of Pakistan, is a planned city constructed since about 1960 at the foot of the Margalla Hills just north of the old city of Rawalpindi. Rapid growth of both Islamabad and Rawalpindi to a combined population near 1.3 million has made ever-increasing demands of shelter for residence and other purposes a major business involving expert engineering. The present research focuses on the geotechnical investigations outcome carried out by GEOENGINEERS, Islamabad for the construction of the proposed Chaudhry Tahir Plaza Lehtrar Road Islamabad. The fieldwork started on 30th October, 2008 and was completed on 3rd November, 2008. During field operation five boreholes were drilled for subsurface strata exploration along with the collection of disturbed samples (DS) and undisturbed samples (UDS) for their index & engineering properties. Besides, Standard Penetration Test (SPT) were carried out at regular intervals and/or any change in lithology to evaluate foundation bearing capacity. Selected samples were sent to the geotechnical laboratory, for testing the results have been compiled. The Standard Penetration Test reveals that N-values ranging between a minimum of 6 at shallow depths to a maximum of 16 at depth. Sandy silty clay/lean clay, which is part of the Potwar Clay lithology unit, extends upto varying depths of 30 to 60 feet inside the boreholes. The soil encountered is classified as CL-ML/CL. per unified soil classification system. The bearing capacity calculated from our field and lab investigations is 0.7 tonnes per square feet for simple footing and 1.0 tonnes per square feet for the suggested raft footing. Geotechnical laboratory analyses for the representative soil samples collected during the drilling of boreholes have also been discussed.
