Due to the complexity of finite element programs, performing a finite element analysis may seem unattractive for some geotechnical engineers. Interestingly, they may prefer to alternatively use simple traditional semi-empirical methods which are generally formulated based on some assumptions that may not be even applicable for the problem in hand. Nonetheless, the engineers rather use… Read More
The enclosed spreadsheet uses a macro that is capable of estimating secant Young’s modulus at 50% of ultimate shear strength (), friction angle (), and undrained shear strength () of a soil layer based on typical borehole data such as SPT blow count and unit weight. This spreadsheet can be very handy when no CPT… Read More
This article intends to shed light on application of Rayleigh and numerical damping in finite element and finite difference analyses. As you all know, there are two types of damping in a system subjected to dynamic loads; (1) material damping, and (2) radiation damping. Material damping is the dissipated energy due to the yielding of… Read More
This article outlines the common design procedures used to evaluate the performance of geotechnical systems that are proposed for mitigation of lateral spreading. The design of any type of retaining structure generally includes; (i) global stability analysis, and (ii) internal stability analysis. In the former, general mass movement of a retaining structure as well the… Read More
Long-term consolidation, seismic dry sand and liquefaction-induced settlements of a soil deposit can impart significant amount of downward load to piles. This load, called downdrag or negative skin friction, is caused by the friction between the pile and the downward moving soil. The magnitude of this force can be estimated by using neutral plane method… Read More
As you all know one of the substantial advantages of Cone Penetration Test (CPT) is that the test provides a continuous profile of soil response. This is why CPT methods generally give superior predictions of axial pile capacity compared to most conventional methods (Robertson, 2015). Bustamante and Gianeselli (1982) proposed a CPT-based analysis procedure based on… Read More
Long-term consolidation, seismic dry sand and liquefaction-induced settlements of a soil deposit can impart significant amount of downward load to piles. This load, called downdrag or negative skin friction, is caused by the friction between the pile and the downward moving soil. In my previous post (click here), I explained how to calculate downdrag load… Read More
Long-term consolidation, seismic dry sand and liquefaction-induced settlements of a soil deposit can impart significant amount of downward load to piles. This load, called downdrag or negative skin friction, is caused by the friction between the pile and the downward moving soil. Per AASHTO LRFD Bridge Design guidelines, downdrag force should be determined as follows:… Read More
Common simplified approaches to calculate seismic active pressure are described below: 1. Semi-empirical Mononobe-Okabe Method The simplest method to approximate seismic active pressure is to use the approach of Mononobe-Okabe (M-O) which is originally based on Coulomb’s theory of static earth pressures. The method incorporates the following assumptions (Geraili and Sitar, 2013): The backfill soil… Read More
Current state of practice in North America to evaluate the performance of slopes during earthquake loading is to use one of the following approaches: 1. Limit Equilibrium Approach This approach uses horizontal and vertical seismic coefficients ( and ) to estimate seismic loads and performs a traditional limit equilibrium analysis to evaluate factor of safety… Read More