Characteristic Values Of Geotechnical Data And Bearing Capacity Mapping For Soils In Nasiriyah
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2022-03-13
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Abstract
Establishing geotechnical maps for Nasiriyah is essential for the preliminary design of soil foundations for any structure, especially with the increase in investment projects. They permit fast access to the engineering properties of soil, define the problematic soil, suggest suitable methods of improvement, detect the water table, and propose the type of foundation. In addition, offering prior knowledge and correlations for the soil parameters that greatly aid in reliability analysis and design of the geotechnical structures.
In this study, a robust database of soil properties in Nasiriyah was considered based on data collected from 423 boreholes from several projects in the governorate. The data was analyzed using a geostatistics analyzer, represented by two methods: the Inverse Distance Weighted (IDW) and Kriging approaches. The results of the two methods were compared in terms of accuracy to create geotechnical maps by matching field results that were isolated for comparison and were not included in the calculations. The allowable bearing capacity qall of Nasiriyah soil was calculated according to the average results to computed by six methods, Terzaghi (1943), Skempton (1951), Hansen (1970), Vesic (1973), Meyerhof (1963), Eurocode7 (1996) and for three types of foundations (square, circular and strip). The correlations were made for different soil a property which helps in modern design. Relationships, graphs, maps, and equations were then linked to guide the geotechnical engineers when designing projects in Nasiriyah. On the other hand, the design characteristics of the strength variables of soil in Nasiriyah were determined, utilizing Eurocode 7 equations and Bayesian statistics. Various methods of determination for laboratory and field tests were expressed through probability distribution models and the reduction of spatial variance.
The geotechnical maps, that were produced by applying Arc GIS (10.7.1) on an extensive database and based on two statistical methods: Kriging and
IDW, demonstrated a good agreement with the results obtained using Python programs. The Kriging method yielded a 1% error rate, while the IDW method yielded a 7% error rate. With respect to the bearing capacity of soil, the lowest bearing capacity of soil in the region south of Nasiriyah was (57-94) kN/m2, and the highest a bearing capacity the eastern region of Nasiriyah was (290) kN/m2, while in the northern region was (94-124) kN/m2. For the correlations between soil parameters, the correlation between c and φ° is positive and medium. This relationship was based on 75 test boreholes at an Al-Gharf oil-producing facility. However, the value of the angle of friction in most other Nasiriyah projects approaches zero and is occasionally ignored.
To create a reliable design, the average values of soil parameters are not enough, and the number of data and the variance of the site must be taken into account. In a Bayesian analysis of typical soil parameters, the ordinary, normal distribution (OND) method produced results similar to those of the bivariate normal (BV) method, with a marginal difference due to covariance. The maximum posterior density (MPD) technique presupposes that the bivariate posterior probability distribution is expected in approach Bayesian, the process of MPD outcomes are comparable to those of the analytic solution. The kriging method produces more precise results, forecasting data in the preliminary design and making prior data. It's used in a Bayesian approach to provide the final design within an accurate, dependable, and economically distinct value.