GeoTechSimulation

 The maximum considered earthquake geometric mean (MCEG) peak ground acceleration (PGAM) is commonly used in the USA to perform geotechnical evaluations including liquefaction, lateral spread, and pseudo-static slope stability analyses. However, to determine seismic earth pressures on basement and retaining walls, ASCE 7-10 and 7-16 Section 11.8.3 – item 1 allows using “Design” Earthquake PGA… Read More

 Unlike Deterministic Seismic Hazard Analysis (DSHA), Probabilistic Seismic Hazard Analysis (PSHA) allows uncertainties in the size, magnitude, location, site condition, and rate of recurrence of earthquakes to be considered in the evaluation of seismic hazards for a particular project site. This post uses the presentations of Professor Kevin Franke from Brigham Young University and Professor Jack… Read More

 Porous materials like soils have different design properties under drained and undrained conditions. As you all know in drained condition, the pore water can easily drain out from the soil matrix while in undrained condition the pore water is unable to drain out or the rate of loading is much quicker than the rate at which… 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

 Subgrade reaction modulus is the ratio of soil pressure to deflection. This modulus is widely used in structural design of mats and slabs. The structural design is completed by structural engineer of record (SEOR) where he/she utilizes the concept of Beam on Nonlinear Winkler Foundation in order to estimate the pressure of soil as well… Read More

 ASCE 7-10 – Section 20.3.1 requires performing site response analysis when site class is F and fundamental vibration period of structure is greater than 0.5 seconds. In this article we want to achieve a clear understanding of this important requirement of the Code. Building Codes of almost all countries, including ASCE 7-10, provide site amplification… Read More

 Structural engineers often ask geotechnical engineers if the insitu liquefiable soil (site class F) in a project site can be improved so that the foundation soil is classified as E or D. In order to answer this question, the geotechnical engineer should evaluate the soil condition and find a method to mitigate liquefaction. There are… Read More

 In the current state of practice, any soil settlement other than consolidation settlement is often called elastic settlement. It is also referred to as immediate settlement in some geotechnical reports. The question is: which one of these terminologies is more appropriate and better represents the nature of soil deformations. Unlike steel or aluminium, soil exhibits… Read More

 Geotechnical engineers use footing allowable bearing pressure as the input load for the estimation of consolidation settlement, a.k.a long-term settlement. It is to be noted that the allowable bearing pressure includes 100% of dead load (D) and 100% of live load (L) . However, ASCE 7-10 allows to use smaller loads for calculation of long-term… Read More