A Spreadsheet for Estimating Soil Water Characteristic Curves (SWCC)

SWCC can be measured in the lab; however, due to the cost, time, and high variability in the results, empirical equations were developed using multiple regression approaches on databases consisting of a large number of measured SWCCs. The spreadsheet presented herein utilizes different methods that use basic soil properties, such as grain size distribution and Atterberg limits, to calculate the input parameters for van Genuchten and Fredlund and Xing equations. These parameters are required by numerical models, such as SEEP/W, to perform transient seepage analysis. The spreadsheet allows copying the generated curve data points as well as an input into the numerical model. The spreadsheet calculates the SWCCs using seven different methods for comparison. It also compares four closed form models, Gardner (1958), Brooks and Corey (1964), van Genuchten (1980), and Fredlund and Xing (1994), given the model parameters are known

Tuning of SVC Stabilizers over a Wide Range of Load Parameters Using Pole-Placement Technique

This paper investigates the effect of typical load model parameters on the static var compensator (SVC) stabilizers tuning. A proportional-Integral (PI) type stabilizer is considered and its gain-settings are tuned using the pole-placement technique to improve the damping of power systems. Tuning of SVC stabilizers (damping controllers) traditionally assumes that the system loads are voltage dependent with fixed parameters. However, the load parameters are generally uncertain. This uncertain behavior of the load parameters can de-tune the gains of the stabilizer; consequently the SVC stabilizer with fixed gain-settings can be adequate for some load parameters but contrarily can reduce system damping and contribute to system instability with loads having other parameters. The effect of typical load model parameters on the tuning gains of the SVC PI stabilizer is examined and it is found the load parameters have a considerable influence on the tuning gains. The time domain simulations performed on the system show that the SVC stabilizer tuned at fixed load parameters reduce the system damping under other load parameters and could lead system instability

Quantifying geogrid reinforcement mechanism in roadway performance using Cyclic Plate Load (CPL) test

For decades, geogrids have been used successfully to improve performance in both paved and unpaved roadway construction. Even though the current state of practice differentiates between the design methodology incorporating geogrids in paved and unpaved roadways, the true improvement contribution of geogrids is to the base layer, or to the layer that is placed directly on top of it. It has been established that the three reinforcement mechanisms by which geogrids enhance roadway performance are: lateral restraint, bearing capacity increase and membrane tension support. In order to quantify these mechanisms and their contribution to the roadway performance improvement, two Cyclic Plate Load (CPL) tests were carried out, one on a paved section with a hot mix asphalt (HMA) top layer, and the second on an unpaved section. The tests included control and reinforced sections. Each test was instrumented with Linear Variable Differential Transducers (LVDTs) at the surface and subgrade levels that measured the displacements at these levels while the cyclic loads were applied. The paper presents the results in terms of the Reinforcement Improvement Ratio (RIR) which is calculated as the ratio between the number of load cycles of the reinforced section divided by the number of cycles of the control section at the same level of displacement. It was found that RIR is almost identical for surface displacements for both paved and unpaved roadway sections indicating the similar lateral restraint effect of the used product. The bearing capacity increase and membrane tension support vary between paved and unpaved sections depending on the level of displacement at the base course and subgrade contact. The results of those two tests were used to put an emphasis on quantifying the mechanism by which the geogrid contributes to the roadway performance improvement regardless whether it is paved or unpaved. The results could be used empirically to modify the current state of practice for geogrid contribution in paved and unpaved roadways. It should be noted that the terms soil reinforcement and soil stabilization have been used interchangeably to indicate the above soil improvements using geogrids

Case Study: Unsaturated Embankment Failure on Soft Soils

This paper describes the application of unsaturated soil mechanics to an interstate connecting-ramp embankment that failed during construction. Specifically, matric suction is incorporated into the calculation of the tension crack (TC) depth induced by desiccation and strain incompatibility and the contribution of matric suction to embankment shear strength. The results are compared with field observations to assess the viability of unsaturated soil mechanics in modeling compacted embankments in stability analyses. Results from this study suggest that using unsaturated shear strength parameters while introducing a TC in the compacted fill yields a reasonable inverse analysis of this interstate embankment. This may be preferred in slope stability analyses to the current practice of using an undrained shear strength (i.e., cohesion) for the unsaturated compacted fill and including a TC to generate a reasonable factor of safety

Using Machine Learning in Estimating Changing Bed Shear over a Flume Test Box

A dam or levee breach caused by overflow erosion is difficult to evaluate during an overtopping event due to difficulty in accessibility and quickly changing conditions. However, for assessment of risk associated with breach time and ensuing downstream consequences, the erosion rate of embankment soils during this process needs to be evaluated. Soil erosion and water depth measurements were taken during flume tests using a Shallow Water Lidar (SWL) system scans. The tests were conducted in a 1-m-wide tilting flume on three cleans and gravel soil mixes with a median grain size D50of 2, 5,and 20 mm. The box measured 0.45-m-wide ×1.2-m-long ×0.25-m-deep. Due to the confined environment of the flow in the flume, the acting bed shear changes with hydrodynamics of the flow differently from under a uniform flow. The scour hole generated in the test box reaches equilibrium when the acting bed shear is equal to the critical shear. Standard machine learning techniques were used to image soil and water profiles from noisy Lidar data. First, the data are filtered using zonal-averaging and then based on the filtered data; the methodology selects the best profiles from a competing set based on the minimum error each profile produces on the data. Once the profiles are obtained, erosion rates and bed shear are computed, and a qualitative assessment is carried out to understand the relationship between temporal and spatial dependence of erosion rate on bed shear and soil particle size. Erosion rate and shear stress reached their maximum value within the first 60–70 seconds of the test and spatially within 0.3 m from the upstream end of the test box. The erosion rate decreased by about 4 times from 0.13 cm/s to 0.03 cm/s as D50increased from 2 mm to 20 mm at the same acting bed shear. The erosion rate for both mixes is reduced over time; however, the rate of reduction for D50of 20 mm is much higher over the same test duration. The erosion rate was shown to be strongly correlated to the acting bed shear nonlinearly. The results indicate that the calculated spatial variation of shear stress over the duration of the tests is consistent with the formation of maximum depth of scour hole

Integrating Field Monitoring and Numerical Modeling to 3 Evaluate Performance of a Levee under 4 Climatic and Tidal Variations

Several short-duration and extreme hydraulic loadings impose time-dependent variably saturated seepage conditions on earthen 7 slopes and embankments. Difficulty assigning appropriate input parameters and lack of full-scale validation are among the main factors 8 introducing uncertainty and lack of confidence when performing numerical transient seepage analysis. This case study demonstrates how 9 to effectively use field-monitoring data to improve the numerical analysis of a levee under climatic and tidal variations. The case study 10 includes a silty sand setback levee located near Seattle. An array of tensiometers and soil moisture sensors installed within the levee’s embank11 ment and foundation, along with a nearly real-time data acquisition system, were used to collect and process the in situ data for a period of 12 about 15 months. Climatic and weather data, including precipitation, temperature, humidity, and wind speed, were collected from a weather 13 station at the site, and tidal water fluctuations were monitored using a water level sensor. The field-measured matric suction and water content 14 were used along with a suction stress–based representation of effective stress to compute suction stress and effective stress profiles versus time. 15 A finite-element model of transient seepage under saturated-unsaturated conditions was developed. The numerical model was calibrated and 16 then validated using the measured pore-water pressures and the piezometric surface. The application of the numerical model was illustrated by 17 modeling the seepage and stability of the levee during a 100-year flood event. The results highlight the need to consider climatic variables and 18 soil–atmosphere interaction when performing transient seepage analysis. DOI: 10.1061/(ASCE)GT.1943-5606.0002134. © 2019 American 19 Society of Civil Engineers

PLEIOTROPIC ROLE OF SIMVASTATIN AND ALENDRONATE ON MESENCHYMAL STEM CELLS

Objectives: Previously, our research group has investigated the effect of alendronate (ALN) and simvastatin (SV) in their minimum inhibitory dose (IC50) on oral squamous cell carcinoma cell line where inhibition of angiogenesis has been demonstrated. In the present study, we further investigate the effect of the previously calculated IC50 of SV and ALN and their combination on two different types of stem cells to show that the same drug may have different effects on different cells.Methods: Stem cells were isolated from rat adipose tissue and oral mucosa. After passaging, cells were subjected to Aln, Sv separately as well as combined in their half maximal inhibitory concentration (IC50). 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay was performed to evaluate cytotoxicity. After seven days, osteogenic differentiation was evaluated using alizarin stain. Real time polymerase chain reaction was used to evaluate Osteopontin gene expression.Results: Our results demonstrated that the proposed combination of Aln and Sv in their IC50 enhanced the osteogenic differentiation of both types of stem cells.Conclusion: The combined effect of Aln and Sv may represent a novel pharmacological approach in treating bone metastasis and at the same time treating the cancer itself

Erosion Rate Equations for Coarse- Grained Materials Using a Small Flume Testing

Erosion rate of soils during a levee or dam overtopping event is a major component in risk assessment evaluation of breach time and consequently in determining the downstream consequences. There is uncertainty in estimation of the erosion rate especially for coarsegrained materials that comprise the outer shell layer of dams as well as homogenous levees that are constructed of such materials. In this paper, erosion rate results are presented on three soil mixes that share the same median grain size D50 of 2 mm, the fines content varies between zero and 20%, and the gravel content between zero and 30%. Each of the three mixes is compacted in the box at optimum or near optimum moisture content as determined from standard Proctor test. The box measures 0.3 m wide x 0.6 m long x 0.15 m deep. Each material is tested several times at varying hydraulic loading to determine the erosion rate after equal time intervals. The water depth, velocity are measured at each hydraulic loading and the acting bed shear is calculated. The validity of the excess shear stress equation is discussed as well as other bilinear and nonlinear models that could fit the erosion rate of such materials as it relates to the acting bed shear stress. The effect of fines content and level of acting shear stresses are presented in the paper

SEISMIC BASE ISOLATION FOR REDUCING SEISMIC RISK OF ARCHITECTURAL HERITAGE BUILDINGS

The paper analyses the applicability of seismic base isolation made of elastomeric bearings for the seismic mitigation of architectural heritage buildings. Due to the inestimable cultural and historical significance any remedial measures into such objects must be selected with care and are usually very limited. In an ideal situation only interventions with minimum visual impacts on the object and maximum potential for restoring its cultural values would be implemented. Historical structures were usually not designed accounting seismic hazard and might be seismically more vulnerable as modern buildings. The paper deals with seismic base isolation as a technique for increasing the seismic resistance of architectural heritage buildings made of unreinforced masonry. Typical base isolation devices represent special bearings that are usually installed bellow the foundations of the structure. If the isolation system is properly designed it can eliminate the need for using more invasive retrofit measures and techniques. The paper presents a relatively simple and computationally less demanding technique for the modelling and analysis of regular unreinforced masonry (URM) structures. This technique is based on the equivalent frame approach, while the complex seismic failure mechanism of masonry piers is expressed by a single failure mode interaction surface (an FMI surface ), taking into account the influence of variation in the pier’s vertical loading, and it’s bending moment distribution. A single failure mode interaction plastic hinge (an FMI hinge ) for each masonry frame element is introduced by combining specific failure modes, taking into account their minimum envelope. In the final part of the work a case study of using base isolation for the seismic retrofitting of an existing three-story masonry building has been conducted. Some results obtained by the N2 method comparing the damage in fixed based and base isolated variant of the test building demonstrate the potential of used techniques for the seismic protection of masonry heritage buildings

Investigation into the determinants of outward cross-border mergers and acquisitions by GCC countries: A macroeconomic perspective.

With increasing levels of foreign investments, the majority of studies have focused on the role of the host country towards attracting inflows of foreign direct investment (FDI) within the context of the developed world. This thesis examines to what extent do home country macroeconomic factors affect outward cross border M&A by the Gulf Cooperation Council (GCC) countries from the period of 1995-2015. In order to investigate into this topic, different quantitative regression models were used: Pooled Ordinary Least Squares (POLS), Random effects model (REM), Fixed effects model (FEM) and negative binomial regression. The results indicate that home country macroeconomic variables including GDP, trade openness, inflation, interest rates and liquidity are significant determinants of outward international M&A deals by the GCC economies. Finally, the limitations and suggested future research lines are presented