Question

Determining the value of bearing capacity factor Nq from field studies is not easily accomplished. Why?

Need explanation and step by step solution and without plagrism

Answer 1

The value of bearing capacity factor Nq from field studies is not easily accomplished because-

The uncertainties and quality of bearing capacity factor Nq for shallow foundation is difficult to analyse.

The models analysis with different modelling approaches such as the analytical model, semi-empirical model, empirical model, finite difference model, upper bound limit model and lower bound with finite element model etc. can be applied for analysis of bearing capacity factor Nq.

The uncertainty in the estimation of input parameters studies is performed forst using multivariate information through multiple correlation, in order to determine the parameters that contribute to the uncertainties of the model prediction.

The uncertainties of the bearingcapacity factor prediction for all models are compared and reveal significant differences.

The consideration of parameter and model uncertainties, a measure for the total variation of the model response is achieved finally.

The results show that more inaccurate the input parameters are,the more uncertain the estimated model quality prediction becomes.

With increasing model uncertainty, the quality of the model also decreases and it affects results also.

It is observed that the model quality decreases with an increases in the friction angle.

The model and parameter uncertainties are important properties that have to be considered while choosing a reliable and safe model application.

The possible sources of uncertainties includes inherent variabilities, measurement errors and modeling or transformation uncertainties.

More economical geotechnical designs can be obtained by estimating uncertainties through site investigation by estimating uncertainties in soil shear strength.

Buismann and Terzaghi adopted the solution for metal punching proposed by Prandtl and applied it to the foundation bearing capacity problem.

They defined three term bearing capacity equation by superposition of the effects of soil cohesion, soil surcharge and the weight of soil, respectively.

The quality of the prediction and reliability of the field analysis, is mainly dependent on the choice of the appropriate models and their coupling.

The decision regarding which model is suitable for a specific application is often based on the experience of the engineer or is made on the basis of experimental data.

The cost of performing experiments is high and also the direct measurement of the bearing capacity factor cannot be obtained experimentally always it is due to the limitations of the test procedures.

A method for quantifying the model quality is generally not available for obtaining bearing facors without measurement.

The calculation is based on total uncertainty of the estimated bearing capacity of the soil.

The total uncertainty is consist of parameter and model uncertainty. The uncertainty analysis considers the complexity of the models and the influence of uncertain input parameters on the model output .

A reference model is generslly used in order to evaluate the deterministic differences in the prognosis to determine the epistemic uncertainty.

The experimental data can be used for this purpose, but there is usually a lack of specific experimental data for the field study.