The building codes have been developed by almost all developed countries of the world, these include guide line specifications for design / construction, building regulations etc; Some have even prepared their geotechnical zonation to be used by engineers and geologists. In Pakistan, however, there is not a single map available showing geotechnical variation, starting from hilly area of Gilgit passing through rolling area (of Jhelum, Rawalpindi etc.) and the lower plain areas upto the sea.
In this study Pakistan has been divided into different zones. Subsequently, ten zones between river Chenab and Sutlej were selected for detailed study. Detailed stratigraphies of the study area have been prepared for the first time in order to develop geotechnical zonation maps. This was followed by the preparation of summary sheets and geotechnical evaluation sheets and the preparation of base map and geotechnical map of Pakistan at (1 m) 3 ft depth. The geotechnical zonation maps from surface down to (12.20 m) 40 ft depth were prepared in order to present a clear picture of strata encountered, or likely to be encountered, at different levels. Sub-soil profiles / stratigraphies were prepared along cross sections from the study. area upto sea and longitudinal sections covering all zones and showing the elevation and type of soil according to the Unified Soil Classification System at different depths. Change of fluvial facies with depth is evident from the stratigraphic sheets and depth maps. Some geological and geotechnical correlations were developed between Standard Penetration Test (Number of blows per foot depth), SPT N-values and depth. The study area was contoured for SPT N-values at (0.91, 1.83, 2.74 and 3.66 m) 3, 6, 9 and 12 ft depth. The study area was also contoured for bearing capacity in ton per square foot (kilogram per square centimetre) at (0.91, 1.83, 2.74 and 3.66 m) 3, 6, 9 and 12 ft depth for breadth of footing (0.61,0.91 and 1.22 m) 2,3 and 4 ft.
The most important conclusion drawn is that the SPT N-values increase with an increase in the depth of soil. However it may be noted that in general with increase in depth the amount of clay and silt decreases while sand increases. SPT N-values increase in kankar horizons which develop in mature soils specially in bar uplands. SPT N-values also increase in soils which are over compacted or are otherwise weakly cemented by carbonates and ferruginous material. SPT N-values and other' parameters, bearing capacities for various footing breadths at different depths could be computed with varying levels of confidence. In limited areas, the relationship between engineering properties and fluvial facies could be established in a general way. But this could not be generalized for the entire study area.
The geotechnical zonation maps will facilitate the designer / geotechnical engineer / geologist for preliminary design of foundations, feasibility study, planning of detailed-investigation programmes for major projects and for the preparation of rough cost estimates for projects in Pakistan.