Deep geological repository (DGR) is one of the most preferred options for the long-term disposal of low, intermediate, and high-level radioactive wastes in many countries. DGR safety depends mainly on the multi-barrier system of both natural and engineered barriers. Bentonite-based materials have been suggested as engineering barrier in DGR, due to their low permeability, high swelling pressure, and retention of radionuclides. Swelling characteristics of bentonite-based materials is a crucial factor in assessing the long-term permeability, hence the safety of DGR. Numerous laboratory tests have been conducted to determine the swelling properties of bentonite-based sealing materials. In this study, laboratory tests on swelling pressure will be performed using different standard methods such as free swelling and constant volume method. In addition to that, a numerical simulation of swelling tests will be conducted to predict the swelling characteristics of various mixture of bentonite -sand, and calibration will be done using laboratory data.

With the increase in extreme rainfall events and rapid urbanization, the risk of flooding has increased substantially. Low Impact Developments (LIDs) can assist in decreasing this risk within certain areas. The soil is generally considered to be completely saturated when designing for the LIDs. However, this may not always be an accurate or realistic approach, as the soil could be variably unsaturated leading to inaccurate designs. To analyze the flow under variably unsaturated conditions, Richards’ equation can be used. In order to solve the Richards’ equation, two nonlinear hydraulic properties namely, soil water characteristic curve (SWCC) and the unsaturated hydraulic conductivity function are required. Laboratory and field measurements of unsaturated hydraulic properties are cumbersome, expensive and time-consuming. An alternative approach is to estimate unsaturated hydraulic properties using pedotransfer functions. Pedotransfer functions estimate soil hydraulic properties using routinely measured soil properties, such as soil texture, grain size distribution, bulk density, or porosity. This research presents a comparison between the direct measurement obtained through experimental procedures and the use of pedotransfer functions to estimate soil hydraulic properties for two green roof and three bioretention soil medias. Design implications are also part of this research effort.

Oil exploration, production and use may cause oil leakage, which can contaminate surrounding soil. Biosurfactants are biologically produced surfactants, which are produced by yeast or bacteria from various substrates like sugars, oils, alkanes, and wastes. Biosurfactants have been used in some remediation technologies for removal of metals and hydrocarbons from contaminated soils. In addition, some nanoparticles have already shown their effective treatment of petroleum-contaminated soil. This research will study the application of various biosurfactants and nanoparticles for treatment of oil-contaminated soil from China. The specific objectives of this work include investigation of the removal of oil from contaminated soil by experimental columns containing some selected biosurfactants and nanoparticles in the lab, evaluation of the effect of some factors, such as pH, temperature, biosurfactant concentration on the removal efficiency, and determination of the range and sustainability of the developed process. Some preliminary results including the synthesis and characterization of nanoparticles, characterization of soil, and removal of oil-contaminated soil by column tests are also included.

Information on the long-term performances of the stabilization/solidification (S/S) technique under real field conditions remains sparse. In this study, a modified triaxial cell was developed to evaluate the physical properties of silica sand solidified with cement. The modified triaxial cell was required to study the influence of loading and carbonation under a confining stress simulating field conditions. The permeability and compressive strength were measured at different stages of four main scenarios involving carbonation only, axial loading only, carbonation first then loading, and loading first then carbonation. The influence of external loading and carbonation on the physical properties of solidified sand is complex. It involves creating new voids (fractures) that increase the permeability, lower the shear strength, and channel the water flow. It also involves calcite precipitation that fills the pore space with opposite effects on the mechanical and hydrodynamic properties of the solidified sand. Results indicate that the mechanical loading accelerated the damage to the S/S samples and increased their permeability. Deterioration owing to loading decreased in the presence of carbon dioxide. The results of this ongoing study will help to understand the long-term performances of the S/S technique.

The performance of earth embankments is essential in sustainable transportation infrastructure. The consequence of embankment instability can have significant safety impacts on the traveling public and financial impacts on moving goods and services on our highways and roadways.
The stability of earth embankments is susceptible to water infiltration as a result of intense rainfall events. Climate change is predicted to continue over this century increasing the likelihood of extreme participation events that can create embankment failures.
The objective of this research is to develop fragility curves for earth embankments under extreme rainfall events in several different locations across Ontario. For this purpose, a series of reliability analyses were carried out to consider the effects of soil parameter uncertainties on the stability of the embankment slopes under various extreme rainfall events. Variably saturated flow modeling and limit equilibrium assessments were primary inputs for the reliability analyses.
The results were compiled to develop fragility curves that present the conditional probability of slope failure for different rainfall return periods and durations. These curves were developed for embankments constructed with sand and silt materials. The developed fragility curves for sand embankments show a decreasing trend in the probability of failure with an increase in return period and rainfall duration. Contrary to sand embankments, the developed fragility curves for silt embankment generally show an increasing trend in the probability of failure with increasing rainfall return period. It can also be observed that the probability of failure for silt embankment is higher for future conditions in comparison to historical conditions. Furthermore, wetter initial conditions cause a considerable increase in the probability of failure for silt embankments, which is in contrast to the results for the sand embankment.