Infrastructures

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25 pages, 31244 KiB

Open AccessArticle

Effects of Hydropower Dam Operation on Riverbank Stability

by Soonkie Nam, Marte Gutierrez, Panayiotis Diplas and John Petrie

Infrastructures 2021, 6(9), 127; https://doi.org/10.3390/infrastructures6090127 - 3 Sep 2021

Cited by 1 | Viewed by 2088

The increasing number of extreme climate events has impacted the operation of reservoirs, resulting in drastic changes in flow releases from reservoirs. Consequently, downstream riverbanks have experienced more rapid and frequent changes of the river water surface elevation (WSE). These changes in the [...] Read more.

The increasing number of extreme climate events has impacted the operation of reservoirs, resulting in drastic changes in flow releases from reservoirs. Consequently, downstream riverbanks have experienced more rapid and frequent changes of the river water surface elevation (WSE). These changes in the WSE affect pore water pressures in riverbanks, directly influencing slope stability. This study presents an analysis of seepage and slope stability for riverbanks under the influence of steady-state, drawdown, and peaking operations of the Roanoke Rapids Hydropower dam on the lower Roanoke River, North Carolina, USA. Although the riverbanks were found to be stable under all the discharge conditions considered, which indicates that normal operations of the reservoir have no adverse effects on riverbank stability, the factor of safety decreases as the WSE decreases. When the role of fluvial erosion is considered, riverbank stability is found to reduce. Drawdown and fluctuation also decrease the safety factor, though the rate of the decrease depends more on the hydraulic conductivity of the soils rather than the discharge pattern. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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16 pages, 3588 KiB

Open AccessArticle

Use of Machine Learning Algorithms to Predict Subgrade Resilient Modulus

by Steve Pahno, Jidong J. Yang and S. Sonny Kim

Infrastructures 2021, 6(6), 78; https://doi.org/10.3390/infrastructures6060078 - 21 May 2021

Cited by 8 | Viewed by 2517

Abstract

Modern machine learning methods, such as tree ensembles, have recently become extremely popular due to their versatility and scalability in handling heterogeneous data and have been successfully applied across a wide range of domains. In this study, two widely applied tree ensemble methods, [...] Read more.

Modern machine learning methods, such as tree ensembles, have recently become extremely popular due to their versatility and scalability in handling heterogeneous data and have been successfully applied across a wide range of domains. In this study, two widely applied tree ensemble methods, i.e., random forest (parallel ensemble) and gradient boosting (sequential ensemble), were investigated to predict resilient modulus, using routinely collected soil properties. Laboratory test data on sandy soils from nine borrow pits in Georgia were used for model training and testing. For comparison purposes, the two tree ensemble methods were evaluated against a regression tree model and a multiple linear regression model, demonstrating their superior performance. The results revealed that a single tree model generally suffers from high variance, while providing a similar performance to the traditional multiple linear regression model. By leveraging a collection of trees, both tree ensemble methods, Random Forest and eXtreme Gradient Boosting, significantly reduced variance and improved prediction accuracy, with the eXtreme Gradient Boosting being the best model, with an R² of 0.95 on the test dataset. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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22 pages, 2722 KiB

Open AccessArticle

Risk Management of Bored Piling Construction on Sandy Soils with Real-Time Cost Control

by Pedro Mata, Paula F. Silva and Fernando F. S. Pinho

Infrastructures 2021, 6(5), 77; https://doi.org/10.3390/infrastructures6050077 - 20 May 2021

Cited by 4 | Viewed by 6150

Abstract

In a global society, in which geotechnical projects are increasingly designed in a country other than the one where construction takes place, geotechnical risk management must be extended to cover infrastructure works, which are smaller than dams and tunnels, for example, since there [...] Read more.

In a global society, in which geotechnical projects are increasingly designed in a country other than the one where construction takes place, geotechnical risk management must be extended to cover infrastructure works, which are smaller than dams and tunnels, for example, since there is a significant impact on works budget imponderables. Therefore, a risk management methodology based on the likelihood of the occurrence of certain events and their economic consequences is proposed, which is applicable to bored piles (Kelly drilled) in coarse soils, easy to use, and simple to implement since the initial stage of construction. Of 12 case studies of construction works involving bored piles (Kelly drilled) carried out in Luanda (Angola), two selected examples involving the proposed risk methodology on sandy soil layers with interbedded clays are discussed. Subsequently, whether the overall foundation contract budget is affected by assessed risk is determined, and what influence it has on the budget in the light of mitigating factors and associated real costs. This method intended to encourage the adaptation of sustainable risk management in bored piles construction by the site project managers, involving risk analysis concurrently with budgetary review. Though the level of assessed technical risk may be acceptable, overall costs associated with the contract in question may not be acceptable. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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13 pages, 2785 KiB

Open AccessArticle

Use of Random Forest Model to Identify the Relationships among Vegetative Species, Salt Marsh Soil Properties, and Interstitial Water along the Atlantic Coast of Georgia

by Iman Salehi Hikouei, Jason Christian, S. Sonny Kim, Lori A. Sutter, Stephan A. Durham, Jidong J. Yang and Charles Gray Vickery

Infrastructures 2021, 6(5), 70; https://doi.org/10.3390/infrastructures6050070 - 3 May 2021

Cited by 6 | Viewed by 2594

Abstract

Saltmarshes, known to be ecologically sensitive areas, face disturbances such as vegetation dieback due to anthropogenic activities such as construction. The current construction specifications recommended by state highway agencies do not specifically require documenting or restoring any prior saltmarsh soil/interstitial water properties, nor [...] Read more.

Saltmarshes, known to be ecologically sensitive areas, face disturbances such as vegetation dieback due to anthropogenic activities such as construction. The current construction specifications recommended by state highway agencies do not specifically require documenting or restoring any prior saltmarsh soil/interstitial water properties, nor do they require re-establishing saltmarsh vegetation; restoring the abiotic properties and appropriate vegetation would enhance the long-term functionality and ecology of a disturbed area. In order to have a successful restoration of disturbed saltmarshes with healthy vegetation, the relationship between vegetative species and the properties of saltmarsh soils and interstitial water must be fully understood. In this study, field and laboratory tests were conducted for the soil samples from eight different saltmarsh sites in the Southeastern US Atlantic coastal region, followed by the development of a random forest model; the aim is to identify correlation among saltmarsh predominant vegetation types, redox potential, and salinity. The results reveal that moisture content and sand content are two main drivers for the bulk density of saltmarsh soils, which directly affect plant growth and likely root development. Moreover, it is concluded that deploying modern machine learning algorithms, such as random forest, can help to identify desirable saltmarsh soil/water properties for re-establishing vegetative cover with the reduced time after construction activities. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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19 pages, 3331 KiB

Open AccessArticle

Layer Composition of Continuously Reinforced Concrete Pavement Optimized Using a Regression Analysis Method

by Byoung Hooi Cho, Moon Won and Boo Hyun Nam

Infrastructures 2021, 6(4), 56; https://doi.org/10.3390/infrastructures6040056 - 6 Apr 2021

Cited by 2 | Viewed by 2372

Abstract

A procedure for determining the optimized composition of layer properties for a continuously reinforced concrete pavement (CRCP) system was constructed using field tests, finite element (FE) analysis, and regression analysis methods. The field support characteristics of a rigid pavement system were investigated using [...] Read more.

A procedure for determining the optimized composition of layer properties for a continuously reinforced concrete pavement (CRCP) system was constructed using field tests, finite element (FE) analysis, and regression analysis methods. The field support characteristics of a rigid pavement system were investigated using a falling weight deflectometer (FWD), dynamic cone penetrometer (DCP), and a static plate load test. The subgrade layer exhibited a more uniform condition than the aggregate base, and the modulus of the subgrade reaction of the aggregate base and subgrade combination (effective k-value) was improved by about 1.5 times by introducing a 2 inch (50.8 mm) asphalt stabilized base (ASB) layer. Thereafter, FE support models describing the actual field conditions were studied. The effects of the thickness of the stabilized base layer, the elastic modulus of the stabilized base material, and the effective k-value on the composite k-value of the support system were identified using a regression analysis method, and the results showed that the variables had a similar effect when determining the composite k-value. Afterward, a procedure for selecting the layer properties for producing a suitable composite k-value was constructed, and we identified that the maximum stress in the concrete slab was induced at different levels, even with identical composite k-values. Lastly, regression relationships were derived to estimate the maximum stress in the concrete slab by considering both the support layer properties and the concrete slab. Subsequently, an algorithm for selecting an optimized layer composition of the CRCP structure was construction considering the economical aspect. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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13 pages, 7654 KiB

Open AccessArticle

In Situ Characterization of Municipal Solid Waste Using Membrane Interface Probe (MIP) and Hydraulic Profiling Tool (HPT) in an Active and Closed Landfill

by M. Sina Mousavi, Yuan Feng, Josh McCann and Jongwan Eun

Infrastructures 2021, 6(3), 33; https://doi.org/10.3390/infrastructures6030033 - 1 Mar 2021

Cited by 4 | Viewed by 2373

Abstract

Municipal solid waste (MSW) landfills near a metropolitan area are renewable energy resources to produce heat and methane that can generate electricity. However, it is difficult to use those sources productively because disposed MSW in landfills are spatially and temporally heterogeneous. Regarding the [...] Read more.

Municipal solid waste (MSW) landfills near a metropolitan area are renewable energy resources to produce heat and methane that can generate electricity. However, it is difficult to use those sources productively because disposed MSW in landfills are spatially and temporally heterogeneous. Regarding the prediction of the sources, the analysis of in situ MSW properties is an alternative way to reduce the uncertainty and to understand complex processes undergoing in the landfill effectively. A hydraulic profiling tool (HPT) and membrane interface probe (MIP) test measures the continuous profile of MSW properties with depth, including hydraulic pressure, temperature, electrical conductivity (EC), and the relative concentration of methane at the field. In this study, we conducted a series of the tests to investigate the MSW characteristics of active and closed landfills. MIP results showed that the methane existed closer to right below the top cover in the active landfill and several peak concentrations at different layers of the closed landfill. As the depth and age of the waste increased, the hydraulic pressure increased for both landfills. The average EC results showed that the electrical conductivity decreased with the landfill age. The results of hydraulic properties, temperature, and EC obtained from active and closed sites could be used to estimate the waste age and help designing energy recovery systems. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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13 pages, 2532 KiB

Open AccessArticle

Estimating Hydraulic Conductivity of Overconsolidated Soils Based on Piezocone Penetration Test (PCPT)

by Binyam M. Bekele, Chung R. Song, Gyunam Jin and Mark Lindemann

Infrastructures 2021, 6(3), 32; https://doi.org/10.3390/infrastructures6030032 - 28 Feb 2021

Cited by 1 | Viewed by 2099

Abstract

Overconsolidated (OC) soils may develop a low or negative pore pressure during PCPT. Thus, it is challenging to develop an “on-the-fly” estimation of hydraulic conductivity from PCPT results. This study presents a method to estimate the hydraulic conductivity of OC soils from PCPT [...] Read more.

Overconsolidated (OC) soils may develop a low or negative pore pressure during PCPT. Thus, it is challenging to develop an “on-the-fly” estimation of hydraulic conductivity from PCPT results. This study presents a method to estimate the hydraulic conductivity of OC soils from PCPT results based on a previously developed method for normally consolidated (NC) soils. To apply the existing method, PCPT pore pressure in OC soils is adjusted by using a correction factor. An equation for the correction factor is derived based on the concepts of critical state soil mechanics, cavity expansion, and consolidation theories. Then, it was reformulated so that traditional cone indices could be used as input parameters. It is shown that the correction factor is mainly influenced by the cone tip resistance, pore pressure, and the rigidity index. The comparison of predicted, which is based on corrected pore pressure and measured hydraulic conductivity showed a good match for four well documented data sets. With the findings of the study, it is expected that an “on-the-fly” estimation of hydraulic conductivity of overconsolidated soils is possible. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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25 pages, 11015 KiB

Open AccessArticle

Experimental and Numerical Studies on Thermally-Induced Slip Ratcheting on a Slope

by Sihyun Kim, Seunghee Kim, Jingtao Zhang, Ethan Druszkowski and Abdallah Sweidan

Infrastructures 2021, 6(1), 5; https://doi.org/10.3390/infrastructures6010005 - 31 Dec 2020

Viewed by 1709

Abstract

Mild temperature fluctuation of a material sitting on a slope may only cause a small slip, but a large number of the repeated temperature changes can amplify the magnitude of the overall slip and eventually bring an issue of structural instability. The slip [...] Read more.

Mild temperature fluctuation of a material sitting on a slope may only cause a small slip, but a large number of the repeated temperature changes can amplify the magnitude of the overall slip and eventually bring an issue of structural instability. The slip accumulation starts from the minor magnitude and reaches the extensive level called “slip ratcheting”. Experimental evidence for such thermally-induced slip ratcheting is first provided in this work. It is implemented with an acryl sheet placed on an inclined wood with a mild angle; it is found that the temperature fluctuation of the acryl sheet causes the sheet to slide down gradually without any additional loading. The numerical model is then attempted to emulate the major findings of the experiments. From the simulation work, the location of a neutral point is found when the acryl plate is heated, and another neutral point is observed when cooled down. The shift of the neutral point appears to be a major reason for the unrecovered slip after a temperature increase and decrease cycle. Finally, a parametric study using the numerical model is carried out to examine which parameters play a major role in the development of residual slips. Full article

(This article belongs to the Special Issue Urban Geotechnical Engineering)

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