Civil and Environmental Engineering

The Surface Water and Ocean Topography (SWOT) satellite mission will provide global, space-based estimates of water elevation, its temporal change, and its spatial slope in fl uvial environments, as well as across lakes, reservoirs, wetlands, and fl oodplains. This paper illustrates the utility of existing remote sensing measurements of water temporal changes and spatial slope to characterize two complex fl uvial environments. First, repeat-pass interferometric SAR measurements from the Japanese Earth Resources Satellite are used to compare and contrast fl oodplain processes in the Amazon and Congo River basins. Measurements of temporal water level changes over the two areas reveal clearly different hydraulic processes at work. The Amazon is highly interconnected by fl oodplain channels, resulting in complex fl ow patterns. In contrast, the Congo does not show similar fl oodplain channels and the fl ow patterns are not well defi ned and have diffuse boundaries. During inundation, the Amazon fl oodplain often shows sharp hydraulic changes across fl oodplain channels. The Congo, however, does not show similar sharp changes during either infi lling or evacuation. Second, Shuttle Radar Topography Mission measurements of water elevation are used to derive water slope over the braided Brahmaputra river system. In combination with in situ bathymetry measurements, water elevation and slope allow one to calculate discharge estimates within 2 . 3% accuracy. These two studies illustrate the utility of satellite-based measurements of water elevation for characterizing complex fl uvial environments, and highlight the potential of SWOT measurements for fl uvial hydrology.

We explored the application of satellite radar altimetry for the monitoring of small inland bodies of water and hydrologic studies using a water-detection algorithm, optimally retracked TOPEX/POSEIDON data at 10-Hz sampling, and investigated the use of radar backscatter to improve land cover classification. The procedure was demonstrated over Manitoba and south-western (SW) Ontario, and the Amazon River Basin study regions. Compared with an L-band synthetic aperture radar data generated water-land cover mask, the water-detection algorithm detected more water points over the Amazon basin. High correlation of 0.98 between the retracked 10-Hz altimetry and the gauge measurements in Manitoba confirmed that the retracked TOPEX data are more accurate than the nonretracked data, and with higher along-track spatial resolution by virtue of its higher sampling at 10 Hz.

a b s t r a c t Envisat 1-D hydrodynamic model HEC-RAS River flow Water level and SWOT mission Riverine deltas are hydrologically one of the most active terrestrial bodies supporting an intricate network of rivers, a highly unsteady flow regime, high agricultural productivity and large population centers. Understanding the complex hydrology of riverine deltas is challenging due to the paucity of conventional ground-based measurements on river water levels and flows that result in large spatial and temporal sampling gaps. One way to bridge this sampling issue is to employ hydrodynamic models in combination with remotely-sensed water level elevation data from satellite altimetry in a data assimilation framework. However, a good understanding of the performance of models and altimetry is required beforehand. Using Bangladesh as an example of a complex delta, an inter-comparison study was therefore performed for water level estimates derived from the two methods: 1) satellite altimetry and 2) hydrodynamic-hydrologic modeling framework. The Envisat mission was selected for satellite altimetry-based water level data. For the modeling framework, a calibrated 1-D hydrodynamic model, HEC-RAS, was set up for the major rivers of Bangladesh using in-situ river bathymetry, gaged stream flow and water level data. Envisat water level estimates were generally found to be exceeded by the model-based values by 0.20 m and 1.90 m for Monsoon and dry seasons, respectively. In general, the average RMSE between Envisat and modeled estimates is more than 2.0 m. The closest agreement with altimetry was observed during the high flow Monsoon season over the Brahmaputra river. Envisat estimates are found to disagree most with model-based estimates for small to medium-sized river basins that are mountainous and flashy. This inter-comparison study provides preliminary guidance on the relative weights to assign for each type of estimate when designing a data assimilation scheme for optimal water level prediction in ungaged basins.

The composition of the fracturing fluid is important to not only fracture the rocks but also provide for efficient transport and placement of proppant into fractured rocks to keep it opened to extract the oil and gas. In this study, the effect of 1% nano silica proppant on the rheological properties, fluid loss and electrical resistivity of the fracturing fluids and transport characteristics in the pre-cracked sandstone were investigated at various temperatures up to 85 o C and up to a pressure of 700 psi (splitting tensile strength of rock) respectively. Two different mixes of the fracturing fluids were developed and used in this study to investigate the effects of nano silica proppant. The amount of water in the fracturing fluid varied from 90% to 93% (by the total weight of the fracturing fluid) and the percentage of the fine sand used varied from 5% to 9% (by the weight of fluid) with 1% of guar gum. Additional of 1% of nano silica increased the electrical resistivity by 18% at room temperature. With increasing the temperature from 25 to 85 o C, the electrical resistivity of fracturing fluid with and without nano silica decreased from 4.56 to 3.11 Ω-m and from 3.75 to 2.78 Ω-m respectively.

In this study, the effect of calcium sulfate content on the index properties, compacted soil properties and compressive strength of a CL soil obtained from the field was investigated. The calcium sulfate concentration in the soil was varied up to 4% (40,000 ppm) and the soil samples were cured for seven days at 25°C and 100% humidity before testing. With 4% sulfate contamination the liquid limit (LL) and plasticity index (PI) of the soil increased by 44% and 80% respectively. Maximum dry density decreased by 7% with 4% of calcium sulfate and also the optimum moisture content increased by 24% with 4% of calcium sulfate. With 4% calcium sulfate contamination the compressive strengths of the compacted soils decreased by 25% and 34% respectively and with polymer treatment these properties were substantially improved. Based on literature review, the sulfate contaminated soil was treated with 6% lime. During this study over 100 tests were performed to characterize the sulfate contaminated CL soil. Stressstrain relationships, index properties and compaction properties of the sulfate soil with and without lime and polymer treatment have been quantified using two nonlinear constitutive models. Also the model predications of index properties and compaction properties were compared with other published data in the literature. The variation of the compacted compressive strength with calcium sulfate concentrations for treated soils was quantified and the parameters were related to sulfate content in the soil and polymer content.

Drilling muds are used in oil, gas, and geothermal well drilling, and fluid loss and filter cake formation are critical issues related to successful operations. Also, the filter cake formation and fluid loss are affected by high pressure and high temperature (HPHT) in the borehole. Rate and total fluid loss from drilling mud can affect the performance of the drilling mud and well safety. Hence, it is critical to quantify not only the rate of fluid loss process but also the changes in the filter cake formation during the fluid loss process. Past studies have assumed that the permeability and solid fraction in the filter cake remained unchanged during the formation of the cake and the fluid loss was directly propositional to the square-root of time (API Model).

The effects of additives on the flow characteristics of the drilling muds used in various drilling operations including oil and gas wells must be better quantified. In this study, acrylamide polymer was used to modify the water based bentonite mud to reduce the yield point and maximum shear stress produced by the mud during the drilling operation. The bentonite content in the drilling mud was varied up to 6% (by weight). Based on the X-ray diffraction (XRD) analyses the major constituents of the bentonite were montmorillonite (MMT, (Na,Ca) 0.33 (Al,Mg) 2 (Si 4 O 10 )(OH) 2 ·nH 2 O), feldspar (Albite, NaAlSi 3 O 8 ), kaolinite (Al 2 Si 2 O 5 (OH 4 )), Beidellite ((Na,Ca 0.5 ) 0.3 Al 2 ((Si,Al) 4 O 10 )(OH) 2 .nH 2 O) and quartz (SiO 2 ). The bentonite was modified using a water soluble polymer solution before using it in the drilling mud. The rheological properties of bentonite were characterized from very low strain rate to relatively high strain rate to determine the nonlinear behavior of the shear thinning drilling mud.

This work investigated the possibility of controlling water percolation into gypseous soils so as to control the collapse of soil due to wetting .Two footings (2mx1mx0.5m) were erected in the field on a treated gypseous soil blankets , 0.5 m thick each . The first footing rested on a gypseous soil blanket after treatment with 4% of used automobile oil .The second footing has rested on a gypseous soil blanket being treated with 4% of fuel oil. Both footings have experienced a loading of 87kPa applied in two equal increments .The first increment lasted for 45 days ,while a total loading time of 90 days was assured for the final load . Ponding the footing with water was assured throughout the testing period .It was possible for such soil treated blankets to restrict water percolation to be within (1-1.5)m over a period of 90 days , despite having the footing zone being flooded with water .The settlements recorded for these loaded footings after 90 days of flooding were found to be within reasonable limits (19-21)mm.. These results encourage the consideration of this measure to be efficient in controlling the behavior of light or moderate weight structures that are erected in gypseous soil zones, and avoiding expected problems .

In this study, the geotechnical behavior of used engine oil-contaminated soils, simulating oil spills was investigated. The testing program included Atterberg limit, compaction using (Harvard Miniature), unconfined compressive strength and total soil suction. Soil samples were artificially contaminated up to 7% used engine oil of the dry weight of soil, Also total suction in contaminated and uncontaminated soil samples by the filter paper and chilled-mirror hygrometer technique were measured. The results showed that the used engine oil contamination decreased the liquid limit and plastic limit of the CL soil. Also oil-contaminated soils indicated a lower maximum dry density and optimum water content compared to uncontaminated soil. The unconfined compressive strength; (q u ) was affected by the increase in oil content in contaminated soils. Soil suction decreased with increasing amount of oil.

In this study the effect of stabilizing an expansive CH soil using a polymer solution was investigated. Modified clay specimens were characterized based Atterberg limits, standard compaction, and unconfined compressive strength. Based on the limited experimental study the expansive CH clay soil behavior was modified.

In this study, the effect of calcium sulfate on the liquid limit, plasticity index and the compaction properties of a CL soil were investigated. The sulfate concentration was varied up to 4% (40,000 ppm). Analyses of the test results showed the natural clay soil properties were changed with sulfate content in the soil.

In this study, the changes in electrical resistivity of drilling mud with different percentage of bentonite up to 8% with and without calcium sulfate contamination at room temperature was investigated. Drilling muds were contaminated up to 3% of calcium sulfate (by total weight of drilling mud). The results showed that the calcium sulfate decreased the resistivity of the drilling mud. Also the yield stress (Y o ) of the drilling muds decreased with increased amount of calcium sulfate concentration. The effect of calcium sulfate contamination on the resistivity of drilling mud at room temperature was quantified.

In this study, the changes in electrical resistivity of drilling mud with different percentage of bentonite up to 8% with and without oil spill contamination was investigated. Also the effect of temperature up to 85 o C on contaminated and uncontaminated drilling mud was studied. Drilling muds were contaminated up to 12% of oil (by total weight of drilling mud). The resistivity of contaminated and uncontaminated samples using were measured using the resistivity meter and conductivity meter probe. The results showed that the oil increased the resistivity of the drilling mud. Also the resistivity of uncontaminated and contaminated drilling muds decreased with increasing the temperature. The effect of oilcontamination on the resistivity of drilling mud was quantified.

In this study, the effect of temperature on the transport of fracturing fluid through a sandstone up to a pressure of 700 psi (splitting tensile strength of rock) was investigated. The fracturing fluid used in this study had 90% water, 9% fine sand and 1% guar gum. The permeability of the rock almost doubled from 1.37 to 2.7 mD when the temperature was increased from 25 o C to 85 o C at a pumping pressure of 700 psi.