Computational fluid dynamics-based modeling of liquefied soils

The residual shear strength of liquefied soil is a key parameter in evaluating liquefaction flow failures. Results from a series of dynamic centrifuge experiments where the shear strength of liquefied soil was inferred by measuring the force required to pull a thin metal plate (coupon) horizontally through the liquefied soil are assessed here using a computational fluid dynamics (CFD) based model. Viscosity is a key parameter for the Newtonian fluid constitutive model used in the simulations, and apparent viscosities of liquefied soil in the range of about 5,800 – 13,300 Pa·s were obtained when the CFD model was calibrated against coupons pulled through liquefied soil in dynamic centrifuge tests. These computational values agree reasonably with apparent viscosities of liquefied soil reported in the literature when the Reynold’s numbers exceeded 1.0. Importantly, the CFD simulations illustrated that in cases where Reynold’s numbers are \u3c 1.0, apparent viscosities of liquefied soil back-calculated using simplistic closed-form solutions commonly applied in geotechnical literature are several orders of magnitude too large; and therefore, such closed-form solutions should not be used for these cases

Incorporating systems thinking and sustainability within civil and environmental engineering curricula at UVM

As part of an NSF Department Level Reform (DLR) grant, the civil and environmental engineering programs at the University of Vermont (UVM) incorporated systems thinking and a systems approach to engineering problem solving within their programs. A systems thinking approach regards social, environmental and economic factors as necessary components of the problem solution. Because it is a whole systems approach it also encompasses sustainability. We have integrated systems thinking in the following ways; 1) new material has been included into key courses (e.g. the first-year introductory and senior design courses), 2) a sequence of three related environmental and transportation systems courses have been included within the curricula (i.e., Introduction to Systems, Decision Making, and Modeling), and 3) service-learning (S-L) projects have been integrated into key required courses as a way of practicing a systems approach. This culminates in the senior design course in which many of the projects specifically focus on sustainability. A variety of assessment methods have been implemented as part of our reform including student surveys, focus groups, faculty interviews, and assessment of student work. We specifically designed a survey tool that addressed sustainability understanding (both open ended and Likert scale). The survey was given to first-year first semester (FYFS) civil and environmental engineering students, FYFS environmental science students, and senior civil and environmental engineering students. Approximately 50% of the incoming civil and environmental engineering students could not define or give reasonable examples of what sustainability means, while their counterparts in environmental science showed that almost 100% could provide a good definition and provide reasonable examples of sustainability. However, by the end of the introductory course in engineering, the majority of the engineering students had a good working definition of sustainability and examples. Female students in both groups showed a statistically significantly higher interest in learning about sustainability than their male counterparts. © 2011 American Society for Engineering Education

Application of unmanned aircraft system (UAS) for monitoring bank erosion along river corridors

Excessive streambank erosion is a significant source of fine sediments and associated nutrients in many river systems as well as poses risk to infrastructure. Geomorphic change detection using high-resolution topographic data is a useful method for monitoring the extent of bank erosion along river corridors. Recent advances in an unmanned aircraft system (UAS) and structure from motion (SfM) photogrammetry techniques allow acquisition of high-resolution topographic data, which are the methods used in this study. To evaluate the effectiveness of UAS-based photogrammetry for monitoring bank erosion, a fixed-wing UAS was deployed to survey 20 km of river corridors in central Vermont, in the northeastern United States multiple times over a two-year period. Digital elevation models (DEMs) and DEMs of difference allowed quantification of volumetric changes along selected portions of the survey area where notable erosion occurred. Results showed that UAS was capable of collecting high-quality topographic data at fine resolutions even along vegetated river corridors provided that the surveys were conducted in early spring, after snowmelt but prior to summer vegetation growth. Longer term estimates of streambank movements using the UAS showed good comparison to previously collected airborne lidar surveys and allowed reliable quantification of significant geomorphic changes along rivers

A New Machine-Learning Approach for Classifying Hysteresis in Suspended-Sediment Discharge Relationships Using High-Frequency Monitoring Data

Studying the hysteretic relationships embedded in high-frequency suspended-sediment concentration and river discharge data over 600+ storm events provides insight into the drivers and sources of riverine sediment during storm events. However, the literature to date remains limited to a simple visual classification system (linear, clockwise, counter-clockwise, and figure-eight patterns) or the collapse of hysteresis patterns to an index. This study leverages 3 years of suspended-sediment and discharge data to show proof-of-concept for automating the classification and assessment of event sediment dynamics using machine learning. Across all catchment sites, 600+ storm events were captured and classified into 14 hysteresis patterns. Event classification was automated using a restricted Boltzmann machine (RBM), a type of artificial neural network, trained on 2-D images of the suspended-sediment discharge (hysteresis) plots. Expansion of the hysteresis patterns to 14 classes allowed for new insight into drivers of the sediment-discharge event dynamics including spatial scale, antecedent conditions, hydrology, and rainfall. The probabilistic RBM correctly classified hysteresis patterns (to the exact class or next most similar class) 70% of the time. With increased availability of high-frequency sensor data, this approach can be used to inform watershed management efforts to identify sediment sources and reduce fine sediment export

Dynamic Centrifuge Experiment on a Cantilever Retaining Wall

Seismic loads on a tall, cantilever retaining wall were studied using centrifuge modeling. An aluminum wall (55\u27 prototype) retaining dry, cohesionless backfill was subjected to two successive dynamic events. The backfill surface was horizontal and even with the top of the wall. The input motion was supplied via a servo-controlled, electro-hydraulic shake table. The input motion was roughly sinusoidal with peak horizontal accelerations of approximately 0.2g and 0.4g for the first and second dynamic events, respectively. The input motion frequency was 1 hz at prototype scale. Lateral earth pressures on the wall, wall displacement, and accelerations of the wall and backfill soil were measured. Pressure transducers were used to directly measure lateral earth pressures on the wall. The magnitudes of the lateral earth pressures were compared with values calculated using the Mononobe-Okabe method. Preliminary results indicate that calculated pressures are higher than the measured pressures

Surface permeability of natural and engineered porous building materials

Characterization of surface gas permeability measurements on a variety of natural and engineered building materials using two relatively new, non-destructive surface permeameters is presented. Surface gas permeability measurements were consistent for both laboratory and field applications and correlated well with bulk gas permeability measurements. This research indicates that surface permeability measurements could provide reliable estimates of bulk gas permeability; and due to the non-destructive nature and relative sampling ease of both surface gas permeability tools, it is possible to quantify the range of the spatial autocorrelation, heterogeneity, and anisotropy in porous building materials and their degree of degradation from weathering

Advances in Engineering Education Incorporating a Systems Approach into Civil and Environmental Engineering Curricula: Effect on Course Redesign, and Student and Faculty Attitudes

ABSTRACT This paper presents a brief overview of the changes made during our department level reform (DLR) process (Grant Title: A Systems Approach for Civil and Environmental Engineering Education: Integrating Systems Thinking, Inquiry-Based Learning and Catamount Community Service-Learning Projects) and some of the effects of these changes on our students and ourselves. The overall goal of the reform has been to have students learn and apply a systems approach to engineering problem solving such that when they become practicing engineers they will develop more sustainable engineering solutions. We have integrated systems thinking into our programs in the following ways; 1) new material has been included in key courses (e.g., the first-year introductory and senior design courses), 2) a sequence of three related environmental and transportation systems courses have been included within the curricula (i.e., Introduction to Systems, Decision Making, and Modeling), and 3) service-learning (SL) projects have been integrated into key required courses as a way of practicing a systems approach. A variety of assessment methods were implemented as part of the reform including student surveys, student focus groups, faculty interviews, and assessment of student work. Student work in five classes demonstrate that students are learning the systems approach, applying it to engineering problem solving, and that this approach helps SUMMER 2011 ADVANCES IN ENGINEERING EDUCATION Incorporating a Systems Approach into Civil and Environmental Engineering Curricula: Effect on Course Redesign, and Student and Faculty Attitudes meet ABET outcomes. Initial student resistance to changing the curriculum has decreased post implementation (e.g., graduating class 2010), and many students are able to define and apply the concept of sustainability in senior design project. Student self-assessments show support of SL projects and that the program is influencing student understanding of the roles and responsibilities of engineers in society