Computer aided analysis of allowable bearing pressure of shallow foundations in layered soil using Scilab

Sukumar Baishya, MD Zeeshan, Sabyasachi De
TXT e-solution

Computation of Bearing Capacity (BC) and Allowable Bearing Pressure (ABP) is one of the important and essential tasks of foundation design. Allowable bearing pressure of a site depends on the shear strength parameters and settlement characteristics of the site, and, the foundation type and shape.

On many occasions detailed Geotechnical Characterisation of a site may not be possible due to difficult ground conditions and limited time and resources. Under such situation, some of the salient soil parameters needs to be estimated from other available geotechnical data, which calls for considerable geotechnical expertise. It also becomes imperative to carry out sensitivity analysis, where study is made as to how the targeted design output, viz. BC or ABP is affected by the variation of input geotechnical parameters, including the estimated ones. Computer aided sensitivity analysis decreases cost and increases the productivity in selecting final engineering design.
In this work, an efficient SCILAB program is developed which i) takes input of various geotechnical data gathered during site exploration, ii) uses the appropriate geotechnical parameters, if available from site exploration, for direct computation of BC and ABP, iii) estimates geotechnical parameters necessary for calculation BC and ABP from other available geotechnical data using well established empirical relations. iv) can handle layered site, v) computes BC and ABP for shallow foundations of various shapes and vi) generate appropriate geotechnical report. The program can determine the significant depth of shear failure or zone of settlement and uses the properties of various layers within these significant depth. Another highly useful feature of the program is that the user can choose to carry out the computation using either i) the user defined values of geotechnical parameters (recommended by geotechnical expert), ii) the arithmetic average of the parameters or iii) the weighted average of these parameters within the significant depth. Modular program design paradigm is used for efficient data hiding. Use is made of SCILAB features like ‘struct’, ‘mlist’ etc. for efficient data management. The results obtained from this program are found to be correct and thus the program is useful for geotechnical engineering practice.