Not available / text

No description available.

No description available.

No description available.

No description available.

Analytical and numerical modelling studies were conducted to assess the performance of thermal conductive heating (TCH) systems for the purpose of contaminated site remediation. Modelling was conducted in a fractured bedrock environment containing a system of parallel, equally-spaced horizontal fractures. A semi-analytical solution to the two-dimensional heat conduction equation was developed and used to study temperature distributions between two thermal wells. A sensitivity analysis was conducted to assess the relative importance of hydrogeological parameters (hydraulic gradient, fracture aperture, fracture spacing) and rock material properties (density, thermal conductivity, heat capacity). Hydrogeological parameters were far more important than rock material properties in determining treatment zone temperature distributions. Knowledge of the bulk groundwater influx may be sufficient to predict the temperature within the treatment zone for low to moderate values of influx. To further the analysis, numerical modelling was employed. A three-dimensional domain was constructed, representing a symmetrical portion of a heater well cluster. Simulations were run for different combinations of bulk permeability, fracture spacing, matrix permeability, and matrix porosity. Flow concentration in fractures had a significant effect on treatment zone temperature distributions when bulk permeability was high. For low values of bulk permeability, the minimum treatment zone temperature changed by less then 7% when modelling the fractured medium as an equivalent homogeneous porous medium. Fracture spacing significantly influenced the time needed reach complete steam saturation, even in cases where it did not affect temperature distributions. A pressure rise may occur in the matrix as water expands thermally, elevating the boiling point of water. The magnitude of the pressure rise is affected by the distance to the nearest fracture, as well as the matrix permeability and porosity. For a given bulk permeability, the time needed to reach complete steam saturation will be lengthened by an increase in fracture spacing, an increase in matrix porosity, or a decrease in matrix permeability. Of these parameters, the matrix permeability is the most significant. The time needed to reach complete steam saturation in the matrix cannot be predicted if the fracture spacing, matrix permeability, and porosity are not known. Further, a clear temperature plateau is not observed during boiling in the matrix, posing a difficulty in monitoring thermal treatment, where temperature measurements may be the only information available. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-04-25 15:22:38.719 / 1. U.S. Department of Defense Environmental Security Technology Certification Program (Project ER-0715) 2. NSERC (Discovery Grant)

The objective of this study was to examine the effect of heat on the growth of a biofilm in a parallel glass plate fracture table. Groundwater was collected from a limestone aquifer and amended with a nutrient mixture to stimulate the indigenous microbial population. The amended water was heated to approximately 30oC in an upgradient reservoir attached to the fracture table and recirculated through the 2-m long, 0.6-m wide, parallel glass plate fracture having an approximate fracture aperture of 2000 μm. The fracture was maintained at approximately 10oC to simulate natural in situ groundwater temperature and the upgradient reservoir maintained at 30oC. Geochemical parameters and bacterial counts were measured regularly throughout the biostimulation to monitor biofilm growth in the fracture. Hydraulic tests and tracer experiments completed before and after the biostimulation were used as the primary indicators of the successful bioclogging of the fracture. Geochemical parameters measured throughout the trial revealed an increasingly reducing environment capable of supporting the development of a diverse biofilm. Direct and indirect bacterial counts revealed the dominant bacteria within the system included common groundwater bacteria pseudonomads, enteric, and slime-forming bacteria. Heterotrophic bacteria were also present in significant concentrations. Visible clusters of biofilm were observed on Day 2 of the trial with a fully-connected biofilm observed by Day 7. The biofilm impacted the groundwater flow through the fracture resulting in an approximately 2.75-hour delay in the tracer’s breakthrough during the tracer experiment completed on Day 13 of the trial compared to an experiment conducted during the initial stages of biofilm development. Based on the results of the tracer experiment, the biofilm growth reduced the velocity of the groundwater by 9.8%, the fracture aperture by 37.8%, and increased the bulk dispersivity to 50mm. Recommendations for future work include the application of heated biostimulation at the field scale in a well-characterized, isolated fracture. / Thesis (Master, Civil Engineering) -- Queen's University, 2011-08-01 12:33:25.286

An analytical model is presented for the interpretation of pumping tests conducted in a fractured rock aquifer. The solution accommodates multiple horizontal fractures intersecting pumping and observation wells with interconnecting vertical fracture features. The uppermost horizontal fracture is connected via this fracture network to a free surface boundary. Wellbore storage is included at the pumping and observation wells using an approximate superposition technique and the solution is derived using the Laplace transform method. Evaluation is performed by numerical inversion using the Talbot algorithm. Sensitivity of the model to the governing hydraulic parameters for both pumping and observation well data is presented for a realistic range of values for fractured rock. A field example is given to demonstrate the application of the model and to explore the uniqueness of the interpreted values. Based on the results obtained using the present analytical model, estimation of unique values of the vertical hydraulic parameters in a sedimentary rock setting may not be possible using pumping test results. Subsequently, measuring aquifer properties from various testing methods was investigated to explore the significance of fracture heterogeneities relative to tested volumes and to determine which testing methods were capable of producing reliable parameter estimates. The hydrogeological study was performed in a fractured sedimentary rock aquifer using four different field testing methods: constant head tests, pulse interference tests, 12-hour isolated interval pumping tests and 48-hour open-hole pumping tests. Particular emphasis was placed on the reliable estimation of vertical hydraulic parameters in this setting. The evaluation of the pumping test data was performed using the analytical model derived earlier to determine whether the new pumping test model could produce confident estimates of vertical hydraulic parameters. While estimates of horizontal hydraulic conductivity measurements were not affected by test method, open-well pumping tests do not appear able to predict values of vertical hydraulic conductivity and specific yield. Alternatively, pulse interference tests may be a less time-intensive option to constant head injection tests for determining vertical parameters in a sedimentary rock setting. / Thesis (Master, Civil Engineering) -- Queen's University, 2012-09-14 11:28:14.466

Geophysical, hydrochemical and hydrogeological investigations were undenaken to evaluate the groundwater prospects in the study area. The factors which affect/determine the spatial development of ground water in the area was also examined. The results show that the essential conditions for groundwater availability in hard rock terrains are satisfied. The average weathering depth is 34 m, rainfall is high and seasonal and the geological evolutionary sequence included tectonic phases during which suitable geological structures are expected to have been developed. Analysis of borehole drilling records revealed that each borehole encountered at least one water strike. The clay mineral stable in the prevailing physico-chemical conditions is kaolinite, an evidence that weathering sites are being flushed presumably by flowing groundwater. Available results of isotope analysis also show that the stable isotope concentration in the groundwater is similar to that of current meteoric water. It is therefore concluded that the ground water is receiving current recharge. Infact water balance calculations and results of baseflow analysis indicate that this recharge is substantial. The yields of the boreholes varied greatly spatially ranging between 0.7 and 10.9 I/s. This may be low compared with values quoted for sedimentary rock terrains, but in view of the present low level of water supply in the area, it is considered that exploitation of this resource would represent a significant improvement on the present situation. A physical catchment hydrogeological model is presented to explain the observed spatial variation in yields. In this model, a threshold elevation is considered to exist in each catchment. At elevations below this threshold, borehole yield is sustained entirely by fracture flow. At elevations above this threshold, borehole yield is sustained by storage in the weathered rocks. Pumping tests on large diameter wells show that groundwater abstration using these wells would be greatly improved by repeated pumping after every 60 - 80 minutes recovery. An equation is presented for calculating the number of times a well can be repeatedly pumped in an operating day. The drawdown of the boreholes contained a large well loss component. This well loss was incurred during the early stages of pumping when water had to be withdrawn from well storage to supplement the aquifer flow in order to meet the pumping capacity. Field results presented indicated that the drawdown can be minimised by stepping the discharge rather than imposing it all at once at the onset of pumping. Field results indicate that the use of well water levels for mapping the water table may not be valid in weathered hard rocks.

No description available.