application of gis in geotechnical engineering

application of gis in geotechnical engineering ppt

Abstract
This paper presents the results of a subsurface site investigation that was performed to characterize different soil and rock formations along Sheikh Zayed canal with particular emphasis on the swelling characteristics of the clays in that area. Site-specific empirical correlations were developed to predict the clay swelling potential and pressure from simple and economic laboratory test results. The data were input into a Geographic Information System (GIS) framework to provide interactive maps that show the spatial distribution of the variables and identify their characteristics. These maps are then used to easily identify the values of swelling pressure/potential at various locations. This research provides a tool that is based on simple index tests that can be used to provide data that otherwise would require elaborate and costly investigations; the GIS framework allows storing, retrieving and updating these data easily to assist taking supported decisions dynamically.

Introduction

Expansive clay beds are widespread all over Egypt. They are considered problematic soils due to their volumetric changes upon moisture content fluctuations .The main factors governing the swelling potential as well as the swelling pressure of expansive soil, are the mineralogical composition and clay size fraction .Direct and indirect techniques have been developed for better classification of the degree of volume change. The parameters used to estimate the swelling potential and swelling pressure include Atterberg limits, colloidal content and clay activity .The oedometer test is a successful tool to measure swell potential and swell pressure .Other methods that successfully estimate the percent of swelling includes chemical and mineralogical analyses.Due to the difficulty of extracting “undisturbed” soil specimens for testing, great attention is given to empirical investigations of the swelling behavior of the natural soils that are based on testing “disturbed samples”. As a result of these investigations, several empirical correlations have been proposed that relate the swelling behavior to certain physical properties of soils such as consistency limits and clay content; all of which are easily obtained from testing disturbed samples. These empirical equations are easy to apply and give satisfactory results.This research was thus put onto track, in order to develop empirical relationships between swelling potential, swelling pressure, plasticity index and clay content for clay from Toshka region in Upper Egypt. The empirical relations are derived from experimental investigations carried out on a large number of soil samples representing a wide variation of clay contents and consistency limits, from El-Sheikh Zayed canal. The steps of the present investigation are presented in this paper.The literature was first reviewed to be aware of the available formula in the field of interest. A study area was chosen and described. The study area was visited and field measurements so as sampling were undertaken. Laboratory examinations were carried out in order to analyze the obtained samples. Based on the examination results, empirical formulae were established.These empirical relations are used as a tool for identifying the soil activity in the region and mapping the study area. The large volume of data concerning the bore holes properties needs to be stored, managed and visualized and this is best done by a Geographic Information System (GIS) in an integrated geographic framework.

Moreover, a customized GIS program can provide detailed maps for the different variables used in defining the swelling pressure as well as any other parameters of choice.A geo-database is designed to store the location, Atterberg limits, soil formation, free swelling and the calculated swelling pressure for each collected sample studied in this research. This analysis approach was adopted recently to the soil in Harran plain located in the South East of Turkey. where the swelling behavior of clayey soils was studied by using Geographical Information System (GIS) including liquid limit (LL) and plasticity index (PI) contour maps. Moreover, the values of swelling percentages determined for soil located in this area are used to obtain the swelling potential hazard map by means of a customized GIS program. It is expected that this map will be a useful tool for planners and engineers in their efforts to achieve better land-use planning and decide necessary remedial measures. Similarly, this research introduces the most valuable property of GIS, ability to provide an interactive map, to the Toshka region. This map can be used in future work in the region and provide decision makers with a reliable and convenient tool to evaluate the soil properties and help them take decisions on the feasibility of executing new national projects in Toshka region, with due consideration to the actual soil properties; this also applies to any future modifications of existing structures or any possible future field variations.