A new article co-authored by Siavash Zamiran has been published by Journal of Rock Mechanics and Geotechnical Engineering. The article discusses a wellbore stability model using a chemo-thermo-poroelastic approach. For reading the full please visit ScienceDirect website or get access to a pre-proof version from Researchgate.
Drilling through chemically-active shale formations is of special importance due to time-dependent drilling fluid-shale interactions. The physical models presented so far include sophisticated input parameters, requiring advanced experimental facilities, which are costly and in most cases unavailable. In this paper, sufficiently-accurate, yet highly practical, models are presented containing parameters easily-derived from well-known data sources. For ion diffusivity coefficient, the chemical potential was formulated based on the functionality of water activity to solute concentration for common solute species in field. The reflection coefficient and solute diffusion coefficient within shale membrane were predicted and compared with experimental measurements. For thermally-induced fluid flow, a model was utilized to predict thermo-osmosis coefficient based on the energy of hydrogen-bond that attained a reasonably-accurate estimation from petrophysical data, e.g. porosity, specific surface area (SSA), and cation exchange capacity (CEC). The coupled chemo-thermo-poroelastic governing equations were developed and solved using an implicit finite difference scheme. Mogi-Coulomb failure criterion was adopted for mud weight required to avoid compressive shear failure and a tensile cut-off failure index for mud weight required to prevent tensile fracturing. Results showed a close agreement between the suggested model and experimental data from pressure transmission tests. Results from a numerical example for a vertical wellbore indicated that failure in shale formations was time-dependent and a failure at wellbore wall after 85 min of mud-shale interactions was predicted. It was concluded that instability might not firstly occur at wellbore wall as most of the conventional elastic models predict; perhaps it occurs at other points inside the formation. The effect of the temperature gradient between wellbore and formation on limits of mud window confirmed that the upper limit was more sensitive to the temperature gradient than the lower limit.
Next Step; Interview with ASCE Civil Engineering Magazine, December 2019
IT WOULD BE EASY TO ASSUME that Siavash Zamiran, Ph.D., P.E., M.ASCE, doesn’t get much sleep. Zamiran, who was presented with the ASCE Edmund Friedman Young Engineer Award in 2019, works full time as a geotechnical engineer for St. Louis-based Marino Engineering Associates Inc. (MEA), teaches geotechnical engineering on an adjunct basis at Missouri University of Science and Technology (Missouri S&T), and serves as the chair of the Sustainability Committee for the St. Louis Section. But he says his enthusiasm, optimism, organizational skills, and devotion to self-improvement keep him going. By continuing to teach in the subjects in which he practices, he maintains up-to-date knowledge and skills. And by reading, networking, and listening to podcasts, he has learned how to manage his time and tasks to achieve a rewarding balance of work, school, and life.
- You have just been promoted from project engineer to senior project engineer at mea and taken on a new adjunct professorship. How are you managing all the responsibilities of both?
What helps is that the courses I teach are in the areas in which I work. There is a saying that if you want to learn something perfectly, teach it. When I had the opportunity to teach geotechnical engineering, I took it so that I could better learn and understand all the rules, formulas, and principles. On a daily basis, I use those same principles in my consulting, analysis, and design.
- How did the opportunity at Missouri S&T present itself?
I am very involved in civil engineering organizations, especially ASCE. My ASCE experiences have helped me to increase my network and connect to other professionals in my area. Also, being in contact with my coworkers who practice in other specialties and with professors in other areas of academics helped.
- How does your job as a senior project engineer differ from that of a project engineer?
When I was a project engineer, I was involved almost entirely in the technical parts of the work—the design and analysis. Now that I am a senior project engineer, I have more responsibilities for project management, relationships with clients, and supervising staff.
The good thing about working for a small-sized company, which mea is, is that it gives me the opportunity to be involved not just in my own work but also other disciplines and areas, including business development, marketing, and client relationships.
- What are the chief skills and abilities that you developed in your previous positions that help you in these new positions?
Being in a more senior position and managing projects and relationships require lots of ‘softer’ skills in parallel with the technical skills. And you really don’t learn those softer skills in school. So I try to increase those skills myself. I read and study about project management, time management, selforganization, and other nontechnical topics. This is useful not only for my work but also for other parts of my life.
Also, when I was working on my dissertation, I had to start something from scratch, come up with the idea, do the research, collect the information, conduct the analysis, develop a procedure, and create an output of my study. Finally, I had to put all that together into a two-hundred-page dissertation and defend it in front of committee members. I worked on it for two years, and it taught me how to handle a long-term, multiple-part project from start to finish. That was a very helpful, practical experience.
- What personal traits or characteristics do you believe help you in these new positions?
I am generally enthusiastic and optimistic about things. And I am consistent about what I want and pursuing it. There is a compound-effect rule that says if you want to reach a goal, you have to be consistent in doing small steps each day, and those steps will compound and accumulate until you reach that result. So, you might not see big results in the short term, but in the long term, you will. It’s all about persistence.
I also try not to fear rejection. That gives me the ability to take risks and seek opportunities and adventures; fear can be a barrier to all that. So, for example, when I wanted to apply for a research position to pursue my ph.d., I got rejected a couple of times, but that didn’t discourage me. If you interview with one professor, you have a low probability of success. But if you interview with one hundred, you can get rejected ninety-nine times and still succeed that one time.
- What technical skills helped you achieve these positions?
The skills I gained from courses in the principles of geotechnical engineering, like soil mechanics, foundations, and the strengths of materials. I have a fair understanding of them, and as I said, when I teach them, that improves my own knowledge.
I am also developing my skills in specific computer programs related to my area. Those programs and computational skills are not taught in traditional school curricula, so I have learned about those programs and how to do specialized analyses on my own.
- How have nontechnical skills helped you in your achievements?
The softer skills sound easy because they are not technical, but it’s hard to learn them and use them in practice. And once you learn them, it’s very easy to use them just for a short period of time and then forget them. But when I keep myself updated and read about them on a day-to-day basis, that improves my learning curve and keeps me motivated.
I have a list of books and articles to read, and of course magazine articles are more motivating because you can read and finish them quicker. There is also something called a mastermind group—a small group of peers who get together to talk about these skills. I have a group of friends, something like a mastermind group, that I keep in contact with. I get more motivated when chatting with them.
- What role did mentors, advisers, or your network play in your achievement?
Being surrounded by friends who are skilled is very motivating. Again, working in a small company gives me an advantage. I can work directly with officers, such as the president of the company. And I also work with faculty at the school where I teach, and they always try to be the top in their fields. That motivates me to follow their path.
- What do you hope to accomplish in these new positions?
I’d really like to learn more about my area of expertise; I read technical materials to increase my knowledge and stay updated. When I do that, I have more confidence about what I am doing.
And right now, I want to learn more about the growing areas of programming, data science, and machine learning. I also want to learn more about automation and statistics and incorporate them into the areas of my interest.
- What types of positions do you see yourself moving toward over the next few years?
I’d like to remain working in the industry and being involved in academics. I’d like to go toward more managerial positions like project manager, where I’d be working more independently on projects from the start and then developing and finalizing them.
- What advice would you give to other young engineers who would seek positions similar to yours?
Continuing your learning is important; when you finish school, that shouldn’t be the last time you open a textbook or read technical material.
Also, keep your life–work balance by being more organized and by learning personal development skills. People might think working full time and teaching would be overwhelming, but learning those personal skills teaches you how to balance everything in your life: work, education, health, and relationships. —LAURIE A. SHUSTER
Read Full Article
The article "Seismic motion response and fragility analyses of cantilever retaining walls with cohesive backfill" has been published in Journal of Soils and Foundations in February 2018. In this article, the seismic motion response of a cantilever retaining wall with cohesive and cohesionless backfill materials was evaluated using fully dynamic analysis based on finite difference method. The dynamic analysis was validated based on experimental test results and then compared to analytical and empirical correlations based on Newmark sliding block method. Seven different earthquake events and the backfills with low to high levels of cohesion were considered. Nonlinear regression analyses were carried out to provide correlations between free-field peak ground acceleration (PGA) and maximum relative displacement of the retaining wall. These results were compared to results from empirical and analytical methods. Furthermore, fragility analyses were conducted to determine the probability of damage to the retaining wall for different free-field PGAs and backfill cohesions. It is demonstrated to what extent a small amount of cohesion in backfill material can influence displacement of the retaining wall and probability of damage in seismic conditions.
For reading the full article please visit here.
Siavash Zamiran was interviewed by The Riverfront Times, a weekly magazine in St. Louis Metro area. The following is the article by Ms. Katie Hayes, The Riverfront Times journalist.
Link of the article
"While most people associate earthquakes with the West Coast — a price residents pay for sunny beaches and L.A. glamour — here's a sobering fact: Missouri is also at risk for a major earthquake.
"Although the earthquakes in the Midwest are less frequent, their effects are wider," says Siavash Zamiran, a civil/geotechnical engineer at Marino Engineering Associates in St. Louis. "There is a lot of probability of another earthquake happening, but not much public awareness of that."
In the next 50 years, there is a 25 to 40 percent chance of an earthquake magnitude six or higher hitting the region. There is a 7 to 10 percent chance of a magnitude seven or higher, as found by the United States Geological Survey.
How big is that? The Loma Prieta earthquake, which famously interrupted the 1989 World Series in San Francisco, crumpling the upper level of the Bay Bridge, collapsing a freeway and causing 67 deaths, reached a magnitude of 6.9.
In other words: It's big.
The cause for concern stems from the New Madrid Seismic Zone — a major seismic zone between the Missouri Bootheel and Memphis, Tennessee.
But that doesn't mean you need to start packing for a safe space. Not yet.
Greg Hempen is a geophysicist who retired from the United States Army Corps of Engineers and now serves as a consultant for the Missouri Seismic Safety Commission. The commission is part of the Missouri State Emergency Management Agency, or SEMA.
"The greatest hazard is from the New Madrid in our area, but that doesn't mean every place in St. Louis will be equally devastated," Hempen says. "The principle threat to structures and residences is in the floodplains. Most people in the uplands should not be too adversely affected."
More than 200 years ago, New Madrid suffered through an earthquake from this seismic zone. The New Madrid Historical Museum, located in the Missouri Bootheel, has testimonies from people who experienced a series of three magnitude 7 earthquakes between 1811 and 1812.
One testimony is a letter sent by William Leigh Pierce to the editor of the New York Evening Post in 1811. It reads, "At New Madrid, 70 miles from the confluence of the Ohio, and on the right hand, the utmost consternation prevailed among the inhabitants; confusion, terror and uproar presided; those in the town were seen running for refuge to the country, whilst those in the country fled with like purpose towards the town. I am happy, however, to observe, that no material injury has been sustained."
Should another earthquake of that magnitude hit, however, the damage would be considerably worse than it was 200 years ago.
"People in 1811 and 1812 were mostly self-sufficient," Hempen says. "They built their own structures. If the structure was only damaged a little, they could repair it. If it was damaged a lot, they could stay with a neighbor until the community repaired it." Today, of course, our lives are more complicated — and our edifices more elaborate.
Masonry buildings, those made with brick and mortar, are the most susceptible to earthquake damage.
"We have some specific issues in St. Louis," Zamiran says. "One is that our buildings are more masonry buildings. So they are built with bricks, without any structural frames, without steel or concrete. They are very vulnerable."
Hempen, however, notes that he lives in a masonry structure that was built in the 1950s and has accepted the risk. While earthquakes are a concern in the region, Hempen says they are not the only hazard people should prepare for.
"I think there is a variety of things people should do short of preparing structures and preparing renovations," Hempen says. "There are many programs for all hazards. I think people should consider a variety of things. One is, do they have a hazard plan, an emergency disaster plan? If there is an evacuation, do they have an emergency list of what they should have?"
Two of the programs Hempen discusses are the Great Central U.S. ShakeOut and Map Your Neighborhood — both meant to educate people in the region about disaster preparedness.
Eight states would be directly affected by an earthquake from the New Madrid Seismic Zone. James Wilkinson, executive director of Central U.S. Earthquake Consortium, brings together emergency managers from each of those states. He says Missouri and the eight states he represents are fully engaged in earthquake emergency update with FEMA.
"Folks need to understand the earthquake is not a West Coast thing exclusively," Wilkinson says. "We have active faults, manmade and naturally occurring. It's important people take time to do research about where they live and the susceptibility they have to earthquakes. Just because there is a threat doesn't mean it has to be all encompassing.""
Current seismic design criteria for retaining wall structures suggested by different organizations are based on estimating seismic earth pressure of the wall using analytical solutions (e.g. AASHTO 2012; Campos 2008). Different guidelines including AASHTO and Caltrans consider pseudo-static analytical solutions to identify seismic earth pressure (AASHTO 2012; Campos 2008). The first analytical attempt as a pseudo-static method to evaluate seismic earth pressure of retaining walls was suggested by Okabe (1926) and the method was verified in retaining walls with unsaturated and cohesionless soil material by Mononobe and Matsuo (1929) using shake table test results. The method developed by these investigators is known as Mononobe-Okabe (MO) method and is still widely used to determine seismic earth pressure of retaining walls. MO procedure is an extension of Coulomb theory and is based on limit equilibrium method and assumes an occurrence of a failure wedge in the backfill. MO method considers the earthquake acceleration is uniform in the backfill and is applied to the center of gravity of the failure wedge.
There are also many studies that evaluated the total seismic earth thrust (Pae) experimentally (Agusti and Sitar 2013; Al-Homoud and Whitman 1999; Atik and Sitar 2009; Nazarian and Hadjian 1979; Prakash 1981; Seed and Whitman 1970) and numerically (Atik and Sitar 2009; Bui et al. 2014; Elgamal and Alampalli 1992; Green et al. 2008; Green and Ebeling 2003; Psarropoulos et al. 2005; Scotto di Santolo and Evangelista 2011; Wilson and Elgamal 2010; Woodward and Griffiths 1996). Specifically, Seed and Whitman (1970), hereafter abbreviated as S&W, conducted different centrifuge tests on retaining walls with cohesionless backfill materials and provided a simple equation for determining Pae, which linearly correlates with horizontal earthquake peak ground acceleration (PGA). Their experimental-based estimation has been used in design guidelines for evaluating Pae, e.g., US Army Corps of Engineers (Whitman and Liao 1985). It is worth mentioning that the earthquake acceleration intensities for the mentioned numerical and experimental studies were limited to PGA ground motions of 0.2g to 0.4g. In most of these studies, the cohesion factor of backfills and hysteretic behavior of soil were also neglected.
Guidelines by AASHTO and state Departments of Transportations require the use of granular materials as backfill for retaining wall constructions as backfills with fine and cohesive material are sensitive to swell, shrinkage, and degree of saturation (AASHTO 2012; Campos 2008; Murinko 2010). However, according to field observations in several cases, backfill materials have a various amount of cohesion (Kapuskar 2005). Kapuskar (2005) conducted field observations of more than 100 retaining wall and abutment backfills used in 20 different bridge sites in the State of California. It was concluded that out of 20 bridge sites, 15 of them had sandy backfills with low plasticity fines that had cohesion up to 95 kPa.
Seismic response of retaining walls considering backfill cohesion has been taken into account analytically (Das and Puri 1996; Prakash and Saran 1966; Shukla et al. 2009; Shukla and Bathurst 2012; Vahedifard et al. 2014). Most of these approaches were developed based on an extension of MO method with consideration of backfill cohesion, wall adhesion, and tension cracks in cohesive backfill materials. The MO-based methods have restrictions to be used for backfills with different soil layers and complex geometries. Therefore, analytical methods based on trial wedge procedure has been proposed for backfills with various layers of soil or complex geometries (Anderson et al. 2008).
In addition to analytical solutions, some experimental and numerical investigations have also been conducted to evaluate the effects of backfill cohesion on seismic response of retaining walls there are some limited experimental and numerical studies are available that assessed the effect of cohesion on seismic response of retaining walls (Agusti and Sitar 2013; Mikola et al. 2014; Wilson and Elgamal 2010, 2015, Zamiran and Osouli 2014, 2015). The limitations of these studies are: 1) the wall response with a variation of backfill cohesion was not considered; 2) the Pae, its point of action, and induced moment under full seismic analyses were not considered; 3) the representative hysteretic damping and shear reduction of the backfill materials have not been considered. Also, these studies focused on the effect of either single soil cohesion parameter or single PGA.
In this study, seismic response of retaining walls is evaluated for cantilever walls with cohesive sandy backfill materials via fully dynamic analysis (FDA). A constitutive model accounting the hysteretic behavior of soil during dynamic loading excitation is utilized. A validated numerical approach based on centrifuge test results is used to conduct the FDA. The effect of three earthquake ground motions and backfill with various cohesions on seismic earth pressures, total seismic earth thrust coefficient (Kae), incremental seismic earth thrust coefficient (ΔKae), the location point of action of Pae, and wall moment variations during the shaking event are studied. The results of FDA are compared to estimations based on current analytical solutions. Finally, recommendations are provided for considering the effects of backfill cohesion in seismic response of cantilever retaining walls.