III. GEOTECHNICAL ENGINEERING

B. ON GOING PROJECTS
1. GIS Based Subsurface Geotechnical Map of Delhi
Date of Start

March 2002
(i) Central Road Research Institute, New Delhi (R)
(ii) Department of Science & Technology (S)

 

Present Status and Progress
(i) 2000 borehole data pertaining to various aspects of geotechnical properties of soil & rock was collected from various agencies

(ii) 1776 borehole data has been finalized for further analysis

(iii) The map of Delhi was divided in to five zones for easy understanding of the data as well as avoiding the gaps between the data links etc

(iv) Each zone is represented with the borehole data falling within their category and each borehole is attached with the database

(v) The data got programmed in such a way that different ranges of N values are highlighted based on their depths. GIS based N value maps of each zone at different depth were prepared

(vi) GIS based soil type map at different depth were prepared

(vii) The short listed data has been provided to IMD (collaborative partner). IMD has prepared liquefaction potential map of Delhi using the CRRI & other data

(viii) The database was also used for preparation of first microzonation map of Delhi. CRRI’s contribution has been acknowledged by DST
 
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 into the required format and further analysis is in progress.

 
Findings/ Conclusions
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).

• 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 prog

• Preparation of Master strip log for the entire 2000 borehole data.

• Preparation of 2D strip logs for each of the borehole data.

• Preparation of Multistrip 2D logs.

• Preparation of 2D Subsurface Geotechnical Map of Delhi.

• Preparation of 3D Subsurface Geotechnical Block Map of Delhi.

• Preparation of Fence diagram.

• Preparation of Cross sections.
 
Limitations

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