Paul H. Simms

Paul H. Simms
Carleton University · Department of Civil and Environmental Engineering

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90
Publications
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Publications

Publications (90)
Article
A modified Couette rheometer is used to simulate mixing of polymer into clayey tailings, and to study the effects of shearing due to pipeline transport. It is found that a normalized torque correlates very strongly with performance indicators measured at the end of mixing and /or shearing, such as CST, oscillatory rheometry, and floc size distribut...
Conference Paper
Full-text available
In-line polymer mixing of fine tailings followed by air drying is being trialed at pilot and operational scales by several oil sands operators as a technology to help achieve Directive 074 regulations. While polymer dose and mixing regime has been optimized for short term dewatering, the influence of polymer dose on other mechanisms that may contri...
Conference Paper
"Ageing" here refers to increase in strength and pre-consolidation pressure independent of density. This phenomenon can induce significant changes in mechanical properties of reconstituted soft soils, or freshly deposited sediments, or clayey oil sands tailings. Ageing increases the peak strength and post-peak strength, while reducing the compressi...
Conference Paper
The ageing phenomenon can induce significant changes in mechanical properties of reconstituted soft soils or freshly deposited sediments such as an increase in peak strength and a decrease in the compressibility. This may be very important for the deep deposits of re-deposited soft soils of low hydraulic conductivity where slow consolidation over a...
Article
Full-text available
Desiccation (water loss by drying or freeze-thaw sufficient to generate matric suction), can influence the performance of a tailings deposit both positively and negatively. The significance of desiccation is largest in tailings that have been dewatered prior to deposition, by thickening or filtration. Such tailings can be “stacked” or deposited wit...
Article
Full-text available
Oil sands fluid fine tailings deposits are challenging to reclaim due to their inherently high natural water content, low permeability, and low strength. Combinations of polymers and/or coagulants are used by operators to improve the dewatering and strength properties of the tailings. However, considerably more work has been done to evaluate polyme...
Article
The cost of sourcing material for cover material is often a barrier to implementation of multilayer covers to reclaim mined waste or other disturbed land. This study investigated the use of municipal biosolids blended with stabilizing materials as a low-permeability material in covers with capillary barrier effects (CCBEs) for reactive mine tailing...
Article
The measurement or estimation of the permeability of soft sediments remains a difficult albeit necessary task for several geotechnical applications, such as land reclamation and tailings management. This note presents a new method for determining the two parameters (the multiplier and power) of the power permeability function for high water content...
Conference Paper
Full-text available
Fluid Fine Tailings (FFTs) are clayey type of tailings produced during bitumen extraction from oil-sands ore. FFTs are often treated with synthetic polymer for transforming their dispersed structure into flocculated structure such that their dewatering and settling tendency is improved. The flocculation quality, however, is influenced by the severa...
Conference Paper
Full-text available
Dewatering fluid fine tailings (FFT) in centrifuges has recorded large scale success, making it one of the technologies available to operators for tailings processing and improving deposits for reclamation in the oil sands industry. Further densification of tailings in these deposits occur through the natural process of consolidation which will tak...
Article
The slow settlement of fine clay particles in oil sands tailings, the by-product from the process of bitumen extraction from the oil sands ores takes many years, leading to the build-up of an enormous volume of fluid fine tailings in tailings ponds over time, which also gives rise to the biggest challenge in tailings management – poor dewatering ra...
Conference Paper
Full-text available
This study evaluated the effects of pipeline transport on the dewatering and settling behaviors of polymer-amended Fluid Fine Tailings (FFT). An advanced Couette rheometer was utilized to simulate the in-pipe shear rates and shear durations that flocculated FFT could experience when transported in different pipe diameters and for different travel d...
Conference Paper
Full-text available
Operators in Alberta’s oil sands industry are required to improve the density and strength of existing tailings deposits to facilitate permanent reclamation to pre-existing boreal forest conditions. Several types of tailings deposits are envisaged and are either being attempted at commercial or pilot scales. One of these, deep deposits of fluid fin...
Article
New approaches are proposed for robustly determining the compressibility and permeability functions for large strain consolidation (LSC), using limited measurements from one-dimensional tests, such as column or centrifuge experiments. These new methods are developed by incorporating several new findings reported in this paper, including i) new anal...
Article
Slurried soils or tailings are often deposited in layers that undergo complex stress paths in terms of desiccation and loading, as a given layer may undergo variable degrees of desiccation before burial by subsequent layers, which has implications for geotechnical stability and geo-environmental performance. Proper analysis therefore requires not o...
Conference Paper
Full-text available
Understanding long-term dewatering behaviour of oil sands tailings is significant to the success and optimization of tailings reclamation plans. Long term dewatering, of tailings is somewhat complex due to mechanical creep and or structuration driven by electrochemical forces, between clay particles. To modernize conceptual models of tailings dewat...
Conference Paper
Full-text available
The cumulative pore-size distribution (PSD) as measured by mercury intrusion can be thought as a potential SWRC, valid only if volume change was someone stopped at the state of measurement. However, it appears that in many constitutive models the purported formulations for the SWRC are in truth analogous to formulations of the cumulative PSD, in th...
Conference Paper
Full-text available
Self-weight consolidation properties of polymer-flocculated fluid fine tailings (FFT) have been investigated in a laboratory using a meso-scale column apparatus with dimensions of 300 mm (dia.) by 1.8 m (height). Four meso-scale columns were used to carry out self-weight consolidation of flocculated FFT with flocculant dosages 650 gm/liter (one col...
Conference Paper
Full-text available
Models that compute dewatering using accurate coupling of evaporation, unsaturated flow and large strain consolidation may have utility in providing guidance to optimise deposition of thickened tailings. A recently developed research model, UNSATCON, is used to analyse some typical field deposition profiles for both hard rock and oil sands fine tai...
Article
The authors (Lloret-Cabot et al. in Acta Geotech 1–23, 2017) applied the glasgow coupled model (GCM), originally proposed by Wheeler et al. (Géotechnique 53(1):41–54, 2003), to the simulation of several experimental tests that involve transition between saturated and unsaturated states. The authors show qualitatively, but not quantitatively, predic...
Conference Paper
Full-text available
Soft soil/tailings deposits exhibit thixotropic/creep behaviour during both initial settling stage and long time after initial settling in large-strain consolidation processes. This behaviour have important influence on the dewatering, consolidation and strength gain of tailings deposits, and therefore should be considered in large strain consolida...
Article
Full-text available
Mineral slurries may be dewatered to the point that they manifest non-Newtonian behavior. Many such slurries exhibit both thixotropic and hysteric behavior in their rheology, which has important implications for managing their deposition in tailings impoundments. This paper characterizes the rheology of a mineral slurry with relatively high clay co...
Article
Tailings are a slurry of silt-sized residual material derived from the milling of rock. High density (HD) tailings are tailings that have been sufficiently dewatered to a point where they exhibit a yield stress upon deposition. They form gently sloped stacks on the surface when deposited; this eliminates or minimizes the need for dams or embankment...
Article
Evaporation is a phenomenon useful in assisting in the dewatering and stabilisation of various mineral wastes. This paper summarises findings on the influence of cracking and salinity on evaporation in mesoscale (1·0 m by 0·7 m in plan) deposition experiments on three different mineral slurries: thickened gold tailings, thickened oil sands tailings...
Article
A mass-conservative formulation of one-dimensional (1D) coupled large-strain consolidation and unsaturated flow using a piecewise-linear formulation is developed. The volume and water-content changes in the unsaturated zone are described using three-dimensional (3D) constitutive surfaces of void ratio and gravimetric water content as functions of n...
Article
A piecewise-linear formulation for simulating coupled large-strain consolidation and unsaturated flow using a mass-conservative and noniterative solution was developed in a companion paper and implemented in a proposed program called UNSAT-CON. The formulation is tested in this paper using numerical cases as well as laboratory and field data. First...
Article
Unsaturated flow in hydrating porous media is pertinent to several engineering applications, including underground and surface use of cemented tailings. Proper description and modelling of flow is complicated by changes in material properties due to hydration as well as by the generation of suction by the net consumption of water volume by hydratio...
Article
The breaching of containment of conventionally deposited mine tailings impoundments, and the consequent release of tailings flows with long run-outs, unfortunately remains not uncommon and often has devastating ecological and economic consequences, occasionally including the loss of human life. Rather than the breaching of containment itself, which...
Article
Mine tailings may be sufficiently dewatered prior to deposition such that they exhibit a yield stress and therefore they will form gently sloped deposits, which result in a number of advantages from an engineering perspective. Predicting the slope and the shape of these deposits at the field scale remains challenging, and is probably the key techni...
Conference Paper
Recent research has shown that desiccation can impart positive stress history effects to thickened hard rock tailings. This paper presents results from consolidation and monotonic simple shear tests conducted on a thickened gold tailings with varying degrees of desiccation history. These results are explained in the context of volume and shear hard...
Conference Paper
UNSAT-CON implements a formulation for simulating coupled large strain consolidation and unsaturated flow using a mass conservative solution developed from piecewise-linear consolidation theory. Recent publications have verified the capacity of this formulation to make predictions for monotonic dewatering. The capacity to accurately model multilaye...
Article
The slow settling of fine clays in oil sands residuals results in the generation of very large amounts of fine tailings that must be stored in dammed impoundments. Dewaterability and settling of oil sands residuals can be greatly improved by adding synthetic polymers, which would help to minimize the volume of tailings. Adding polymers at the optim...
Article
Tailings may undergo desiccation stress history under varied climatic and depositional parameters. While tailings substantially dewatered prior to deposition may experience desiccation under the greatest range of climatic variation, even conventionally deposited tailings may desiccate in arid climates at lower rates of rise. Bench-scale research ha...
Article
Various forms of thickened or high-density tailings, characterized by exhibition of a yield stress that facilitates deposition in gently sloped stacks, are increasingly used for a variety of mining operations. Although this technology reduces reliance on containment by dams and the associated risk of catastrophic failure, regulators are concerned w...
Article
Consideration of non-Newtonian flow behavior has been important in the management of mineral resource wastes for some time, chiefly in regards to dewatering and pumping of concentrated suspensions of mill tailings. These dewatered tailings, often referred to as “thickened” or “high-density” tailings, may be deposited on surface, and if they are suf...
Article
A simple-shear apparatus (Norwegian Geotechnical Institute (NGI) type) has been used to investigate the mechanical behaviour of gold tailings under monotonic, cyclic, and post-cyclic loading. Specimens were prepared either by reconstituting the tailings at different water contents or by employing a “dry–wet” preparation technique. The latter techni...
Article
The soil-water characteristic curve (SWCC) of fine-grained soils is usually determined experimentally. In many applications, such as design of mine waste covers and landfill liners, the unsaturated permeability function, k(h), is often derived theoretically from the measured SWCC. Implicit in these derivations is the transformation of the SWCC to a...
Article
The presence of salts is detrimental to plant growth in soils and also impedes consolidation in disposed mine tailings. The current study conducted small-scale column drying tests on "clean" soil prepared to homogenous initial pore-water concentrations using a model wax column technique. This study characterized the coupling of 1D solute mass trans...
Article
Full-text available
Both the geotechnical and geoenvironmental performances of surface deposited "paste" mine tailings are strongly influenced by desiccation, rewetting after precipitation, as well as interlayer flow. All these processes strongly depend on unsaturated flow within the tailings. Modeling of small (0.15 m in diameter)- and large (1.7 m x 1.7 m in plan)-s...
Article
Dewatering tailings prior to deposition is an attractive alternative to conventional practice, as it minimizes the use of embankments and therefore reduces the risk of catastrophic failure associated with dammed slurry impoundments. One of the potential detriments is the absence of a water cover and the consequent increase in oxygen ingress and gen...
Article
A new principle for matric suction measurement is proposed, based upon strain measurement of a contiguous porous material of high air-entry value (AEV). In theory, this allows for the measurement of matric suction without the associated errors due to cavitation or hysteresis for suctions below the AEV. Results from testing a prototype sensor made f...
Article
Surface deposition of paste or thickened tailings is increasing contemplated as an alternative to conventional slurry deposition. One important challenge in managing paste is to predict the evolving geometry of the tailings stack during deposition. This study dynamically images multilayer deposition of paste in flows in flume and axisymmetric flows...
Article
Hydration occurring in cemented paste backfill (CPB) is shown to generate matric suction through self-desiccation. This complicates determination of the water-retention curve and mechanical properties during curing, which are important in stope design, and renders problematic the use of axis-translation testing procedure to control suctions in stre...
Article
Full-text available
The deposition of paste tailings on surface certainly offers many potential advantages to conventional deposition, such as reduced reliance of dams, increased water recycling within an operation, reduction in volume of tailings, and lower rates of seepage. The disadvantages include increased risk of acid generation, the challenges of managing the e...
Article
Full-text available
With the advent of modern microstructural testing techniques and microstructure based constitutive models the microstructural characterisation of soils is gaining prominence. This paper reviews the history of microstructure investigation in unsaturated soils and discusses the engineering significance of this research to date. After a brief overview...
Conference Paper
The deposition of paste tailings on surface certainly offers many potential advantages to conventional deposition, such as reduce reliance of dams, increased water recycling with in an operation, reduction in volume of tailings, and lower rates of seepage. The disadvantages include increased risk of acid generation, the challenges of managing the e...
Chapter
With the advent of modern microstructural testing techniques and microstructure based constitutive models the microstructural characterisation of soils is gaining prominence. This paper reviews the history of microstructure investigation in unsaturated soils and discusses the engineering significance of this research to date. After a brief overview...
Article
Accurate predictions of drying rates are desirable to optimize surface deposition of thickened or paste tailings. A series of laboratory and field trials were implemented to study evaporation from tailings at the Bulyanhulu gold mine and were compared with numerical simulations using the unsaturated flow model SoilCover. The laboratory tests includ...
Article
The behaviour of deformable unsaturated soils is difficult to characterize with simple relationships. Unsaturated hydraulic properties, namely the soil-water characteristic curve and the hydraulic conductivity function, are dependent on both volume change and degree of saturation, whereas volume change itself often cannot be related to a single str...
Article
The soil-water characteristic curve (SWCC) of fine-grained Soils is usually determined experimentally. In the design of mine waste covers and landfill liners, the unsaturated hydraulic conductivity function, k(h), is often derived theoretically from the measured SWCC. Implicit in these derivations is the transformation of the SWCC to a pore-size di...
Article
Estimation of hydraulic conductivity by appropriately using indirect methods was discussed. The indirect methods involve the use of two complimentary functions, one for the soil-water characteristic curve (SWCC) and another for the unsaturated hydraulic conductivity function. To determine the unsaturated hydraulic conductivity, the formula for the...
Article
The unsaturated hydraulic conductivity function, k, is often predicted from the soil-water characteristic curve (SWCC). Most methods implicity or explicitly derive a pore-size distribution (PSD) from the SWCC, which is then used to calculate k at any suction. Two important factors ignored by most methods are the change in the PSD during the SWCC te...
Article
Full-text available
An experimental soil cover constructed near London, Ontario, 23.2 m × 15.2 m in plan area, has been monitored for 2 years for percolation and water-content data. The cover was a multilayer system consisting of a compacted till barrier soil placed between evaporation and drainage barriers of sandy gravel. Half of the cover was capped with coarse sto...
Article
A problem in implementing water covers over existing tailingimpoundments is the dissolution of minerals produced throughoxidation and the subsequent flux of metals into the water cover.One possible solution is to place a protective layer of non-reactive soil at the tailings/water interface to inhibit metaltransport. A laboratory evaluation of diffe...
Article
The soil-water characteristic curve (SWCC) of fine-grained soils is usually determined experimentally. In many applications, such as design of mine waste covers and landfill liners, the unsaturated permeability function, k(h), is often derived theoretically from the measured SWCC. Implicit in these derivations is the transformation of the SWCC to a...
Article
A potential problem in implementing water covers over preoxidized tailings impoundments is the dissolution of oxidation products following flooding, which may result in high concentrations of metals in both tailings pore water and the water cover. To examine metal release phenomena under controlled conditions, a laboratory study consisting of four...
Article
To evaluate the effectiveness of soil covers, column experiments were conducted on tailings protected by a three-layer soil cover and tailings directly exposed in the open laboratory for a period of 760 days. Periodic rain application was performed to simulate field conditions, and at four times during the experiments the pore water was completely...
Article
An experimental soil cover was constructed near London, Ontario and monitored for more than a year for percolation and water content data. The cover was a multi-layer system consisting of compacted till barrier soil placed between gravel layers, and a final topsoil cap in one half and a coarse stone cap in the other half. The lower gravel layer was...