Highway Research Record

GIS Based Subsurface Geotechnical Map of Delhi

Date of Start: March 2002
Central Road Research Institute, New Delhi (R)

Present Status and Progress
Out of around 500 reports collected, except DMRC reports, none have the locations of boreholes in terms of Longitude and Latitude or Easting and Northing which are prerequisite for GIS map. Most of the reports have the general locations. To find out the exact geographic coordinates of each of the boreholes a manual approach of locating the boreholes into the Topographic map of Delhi was applied. The borehole locations were then transferred into the GIS Map. Till the present time 1776 boreholes have been marked. The Longitude, Latitude and Easting, Northing as well as the elevation are extracted and updated into the linked tables with the GIS Map.

Subsurface Data analysis
The Rockworks Software was procured to do the subsurface analysis. The process of keeping the data into required format was started in the current year. Where as separate formats for primary borehole data such as project no., water table, latitude, longitude, ground level, investigation date etc. similarly, format for soil also made having almost all the possible engineering properties which could be considered by an engineer for construction of a foundation for building, flyovers, bridges, tunnels, Retaining structures etc. For rock properties also a separate format was designed including almost all the possible properties. Since, the software has its own format, the entire data is now being listed into the inbuilt format. The data is now fully reformatted to fit into new format and further analysis is in progress.

Findings / Conclusions
(i) First and foremost step will be to divide the whole Delhi area into four grids, to find out the density of data in each grid     (NSEW).
(ii) The density of data, as of now (out of 1776 boreholes marked in GIS Map) seems to be scarce in NW part of Delhi, and      less scarce in SW. However good density of Boreholes has been noticed in NE and SE part of Delhi. Master log      (representing the Lithology / Stratigraphy of all the boreholes) required for the subsurface analysis using the rockware      software has been completed for all boreholes and the following subsurface analysis is in progress.
(iii) Preparation of Master strip log for the entire 2000 borehole data.
(iv) Preparation of 2D strip logs for each of the borehole data.
(v) Preparation of Multistrip 2D logs.
(vi) Preparation of 2D Subsurface Geotechnical Map of Delhi.
(vii) Preparation of 3D Subsurface Geotechnical Block Map of Delhi.
(viii) Preparation of Fence diagram.
(ix) Preparation of Cross sections.

The study is based on the data collected from various agencies in Delhi. Therefore, there could be some fluctuations in accuracy of the data.