Geotechnical Maps for Angle of Internal Friction of An-Najaf Soil-Iraq Using GIS


The angle of internal friction value (φ) is used to describe the soil resistance to shear failure. It is estimated experimentally either from Direct Shear Test or Triaxial Stress Tests. Because of the high cost needed for conducting field tests, it has become essential to find alternative and practical methods to predict soil characteristics for non-spatial data areas. The objective of this study is to specify the best interpolation method to predict the angle of internal friction and use it to produce geotechnical maps for parts of An-Najaf province-Iraq; these parts are the city centre An-Najaf and Kufa city. Furthermore, the study describes the strength and type of soil strata. The results show that the Local Polynomial Interpolation (LPI) is the ultimate and the most significant method to interpolate the angle of internal friction. Moreover, the angle of internal friction φ values is ringing between (20-46) degrees, which represent medium to dense soil resistance to shear, while the mean values of φ ranged between 34.3 - 36.18 and represent good resistance to shear failure. This indicates that the Density of Sand is medium to dense, and N60 values range from 10-50. This kind of map would ease the engineers and decision-makers to decide the suitability of the construction site to carry loads, and the selection the foundation type. The benefits also extend to selecting urban expansion alternatives and for the delimitation of future trends for land-use-development processes in the metropolitan area of An-Najaf city, mainly at local and regional scales.