Hydraulic Conductivity Tests Research Articles

MECHANICAL PROPERTIES OF RC BEAMS WITH AFRP SHEETS UNDER A SUSTAINED LOAD

In this research, an attempt was made to find the permeability of an RC beam with AFRP by making use of the hydraulic conductivity test and a double-ring infiltrometer. Based on the state-of-the-art methodology, three different AFRP samples, Kelvar 29, Kelvar 49 and Kelvar 149, were considered as the laminates to prevent the deflection of the beams. Accelerated corrosion was carried out using impressed current, and induced corrosion was calculated using the galvanostatic method. In this project, nine RCC beams were strengthened with aramid FRP sheets. Novel results were obtained using three different layers and three different patterns of AFRP sheets. Experimental investigation showed that the mechanical properties of the reinforced concrete beams were enhanced (by 10 %) with Kelvar 149. The durability and corrosion resistance of concrete were achieved due to the increased number of layers of the AFRP sheet. The entire research shows that three layers of Kelvar 149 allow better performance of the concrete specimens. No other results based on the abrasion resistance and hydraulic conductivity of beams with AFRP laminates are available in the literature.

Improving strength and hydraulic characteristics of regional clayey soils using biopolymers

This paper portrays a unique demonstration of sustainable low-cost ground improvement for regional soil deposits, by comparing locally sourced biopolymer soil stabilisation soil with imported biopolymer stabilisation. The conventional materials often utilized for soil and ground improvement come with major challenges of large carbon footprints and some negative environmental impacts. As a result, suitable eco-friendly and sustainable materials are necessary. In this study, the potential use of Rice Husk Powder (RHP), Cassava Peel Powder (CPP) and Carboxymethyl Cellulose (CMC), as biopolymer-based materials to improve the engineering properties of a regional clay was investigated using a gamut of geotechnical compaction, strength and hydraulic conductivity tests according to BS 1377, 1990. The results revealed that locally sourced CPP performed better than both imported CMC and local RHP in improving the engineering properties of the regional clay. The shear strength value of the natural clayey soil (43.5 kPa) increased twenty and ten times respectively when treated with CPP (893 kPa) and CMC (450 kPa). One percent content of CPP and CMC performed optimally among the (0.5, 1.0, 1.5, 2 and 2.5) percent studied in improving the engineering properties of the case study regional clay.

Multi-aspect engineering properties and sustainability impacts of geopolymer pervious concrete

This study aimed to comprehensively evaluate multi-aspect engineering properties and sustainability impacts of geopolymer pervious concrete. Geopolymer binder was prepared using metakaolin (MK) or fly ash (FA) with granulated blast furnace steel slag (GBFS) and used to fabricate pervious concrete; while conventional pervious concrete was made with Portland cement (PC). The strength and durability results show that the MK based pervious concrete exhibited superior performance in mechanical property (3200 psi compressive and 520 psi splitting tensile strength) and lowest mass loss (3%) after 70 cycles of freeze & thaw test. The FA based pervious concrete had about 10% higher splitting tensile strength and better raveling resistance than the PC based pervious concrete, but its freeze & thaw resistance was the lowest (8% mass loss after freeze & thaw test). The hydraulic conductivity test results show that the porosity was the major influence factor for permeability coefficient. The permeability coefficients increased from 3.5 to 12 mm/s with the increase of porosity from 13.5% to 24.5%. However, the binder type had no obvious effect on the permeability and clogging resistance. In addition, life-cycle assessment (LCA) was applied to quantify energy consumption and greenhouse gas (GHG) emission of pervious concrete with different raw materials. The FA based pervious concrete showed the lowest energy consumption, while the MK based pervious concrete had slightly greater energy consumption than conventional pervious concrete. Compared with PC based one, the GHG emissions of MK and FA based pervious concrete could be reduced by 33% and 53%, respectively.

Hydraulic Performance of Geosynthetic Clay Liners Comprising Anionic Polymer–Enhanced Bentonites

The hydraulic performance of geosynthetic clay liners (GCLs) comprising anionic polymer–enhanced bentonites (EBs), or EB-GCLs, based on permeation with 500 mM NaCl and 167 mM CaCl2 at an average effective stress of 27 kPa and hydraulic gradients of ∼300 was evaluated. The EBs included powdered sodium bentonite (NaB) enhanced with one of seven anionic polymers, including linear, noncrosslinked poly(acrylic acid) (PA) with low, medium, and high molecular weights, sodium carboxymethylcellulose (CMC) with either low viscosity or high viscosity, a covalently crosslinked sodium polyacrylate, and an in situ polymerized bentonite polymer composite. The NaB was enhanced with polymer at mass loadings of 5%, 8%, or 10% using dry-sprinkling, dry-mixing, and/or wet-mixing methods. Hydraulic conductivity tests at a low hydraulic gradient (∼35) also were conducted to determine the effect of seepage forces. Overall, the hydraulic performance of the EB-GCLs to the NaCl solution was better than that to the CaCl2 solution. Dry sprinkling (DS) with PA generally provided the best hydraulic performance, with hydraulic conductivity values based on permeation with 500 mM NaCl and 167 mM CaCl2 of 1.3×10−11 and 4.0×10−11 m/s, respectively, for the high-molecular-weight PA added at 5% via DS and 2.9×10−11 and 4.7×10−11 m/s, respectively, for the medium-molecular-weight PA added at 8% via DS. The CMC viscosity grade did not affect the hydraulic conductivity of the EB-GCLs. All EB-GCLs eluted polymer during permeation, regardless of mixing method or polymer type. Polymer elution was correlated with preferential interaggregate flow paths in multiple EB-GCL specimens, indicating the importance of polymer retention in maintaining low hydraulic conductivity of EB-GCLs. Because standard termination criteria for the measurement of the hydraulic conductivity of conventional unenhanced GCLs (e.g., as per current ASTM standards) do not address the potential impact of polymer elution from EB-GCLs, caution should be exercised when adapting these criteria to measure the hydraulic conductivity of EB-GCLs such as those evaluated in this study.

Hydraulic conductivity and X-ray diffraction tests of unsaturated bentonites with a multi-ring and their predictions by pores distributions

Following instantaneous profiling method, a new multi-ring was applied in wetting apparatus to ascertain water diffusivities of three bentonites (MX-80, Kunigel-V1, and Kunibon). Hydraulic conductivities of unsaturated bentonites were calculated combining water diffusivities and soil water retention curves (SWRC). Basal spacings were achieved by sending slices from the multi-ring to X-ray diffraction (XRD) tests. A dual pores system was proposed: 1) micro pore (inter-layer pores); and 2) macro pore (inter-particle pores and inter-aggregate pores). By discussing water flow mechanisms in bentonite, it was supposed that: moveable waters flow through macro pore. Porosity and tortuosity of saturated macro pore were used instead of porosity and tortuosity of saturated total pore in traditional Kozeny-Carmen (KC) equation, which was designated as modified KC eq. A new relative permeability was raised for predicting unsaturated bentonites hydraulic conductivities. Macroporosity and macrovolumetric water content were obtained from estimated basal spacing during saturation. Comprehensive comparisons between experimental database and predictions were conducted. Results revealed that the modified KC equation can predict both saturated and unsaturated hydraulic conductivities better.

Engineering Performance Evaluation of Recycled Red Mud Stabilized Loessial Silt as a Sustainable Subgrade Material.

Industrial solid waste red mud discharge has caused serious environmental problems. This study utilized red mud as an additive to loessial silt being used for roadway subgrade material. In this study, unconfined compressive test, direct shear test, electrical resistivity test, and hydraulic conductivity test were conducted on red mud stabilized loessial silt (RMLS) with different red mud dosage (DR) to investigate DR effect on mechanical-electrical-hydro properties. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were carried out to reveal the mechanism from micro perspective. The results showed addition of appropriate amount of red mud (30–42%) effectively improved unconfined compressive strength of treated loessial silt but reduced resistivity and hydraulic conductivity. Significant correlation between resistivity and strength performance of RMLS mixture was developed. Microscopic analysis indicates red mud addition will promote generation of hydration products such as calcium silicate hydrations (C-S-H), calcium silicate aluminates hydrations (C-A-S-H), and ettringite (Aft), which will tightly connect surrounding particles of loessial silt and hydrates. Red mud particles adhere to surface of soil particles and fill in pores between them improving a compact and stable structure. This study demonstrated the feasibility of using red mud as a stabilization material for roadway subgrade and proved that resistivity measurement is a nondestructive testing method to evaluate mechanical properties for RMLS mixture.

Sustainable Road Shoulders and Pavement Protection for Expansive Soil Zones

The design of sustainable infrastructure roads in semi-arid highly expansive soil is of concern to the geotechnical and pavement design engineers. The damage and distress caused to highways and roads in areas with high swell potential occur as a result of ingress and infiltration of water to the underside of light pavements. These pavements exert very low stresses on the ground. Protection of subgrade and shoulders against variation in moisture content as a result of seasonal weather fluctuation and floods can help in establishing a sustainable pavement for an extended lifetime. Predicting the response of a subgrade soil subjected to different rainfall intensity and frequencies is very challenging. The approach proposed in this study is to target a reduction of moisture exposure to prevent water from entering the systems. However, efficient protection is required when severe floods occur so as to remove water from the shoulders in a short time. The sloping shoulders are intended to guide floodwater away from the pavement. Clay-sand liners can be constructed as a dressing layer along the shoulders or within the body of the shoulder extending up to the toe of the slope or beyond. Assessment of a typical sand–clay liner was conducted. Suggested designs were based on characterization, compressibility, and hydraulic conductivity tests. It was found that stresses exerted on the liners do not pose a significant settlement hazard.

Fracture effect on the hydro-mechanical behaviour of Callovo-Oxfordian claystone

Excavation of the galleries for the geological disposal of radioactive waste can induce an excavation damaged zone (EDZ), which can have consequences on the long-term safety of the repository. In this study, intact Callovo-Oxfordian (COx) claystone taken from the Meuse/Haute-Marne Underground Research Laboratory in France was artificially fractured in different directions, and the hydro-mechanical behaviour was investigated by performing high pressure oedometer test and hydraulic conductivity test. Comparison between the fractured and intact COx samples allows identification of the effects of fracture in terms of swelling, compression, hydraulic conductivity and creep. It appears that the presence of fracture decreases the swelling strain and this phenomenon depends on the infiltration path and the orientation of fracture. In particular, the infiltration path affects the global swelling rate of fractured claystone. The self-sealing of fracture is mainly attributed to the swelling of COx claystone grains in the fracture zone. Lower compression coefficient a, higher compression index Cc* and higher secondary consolidation coefficient Cα are observed for the fractured claystone, indicating a higher compressibility and creep than the intact one. The compression and creep behaviours depend on both the orientation of fracture and the stress level. Comparison of hydraulic conductivities between fractured and intact claystone indicates that the hydraulic conductivity can be partially recovered due to the collapse of macro-pores in the filled fracture zone. This is also confirmed by analysing the evolution of consolidation coefficients cv with stress. Beyond a stress level about 16 MPa, the fracture effect can be neglected, but the compressibility increases further due to grain breakage. Interestingly, this stress is close to the in-situ stress before excavation.

Effect of water chemistry on the hydro-mechanical behaviour of compacted mixtures of claystone and Na/Ca-bentonites for deep geological repositories

In the French deep geological disposal for radioactive wastes, compacted bentonite/claystone mixtures have been considered as possible sealing materials. After emplacement in place, such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete. In this study, the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites (MX80 Na-bentonite and Sardinia Ca-bentonite) were investigated by carrying out a series of swelling pressure, hydraulic conductivity and mercury intrusion porosimetry (MIP) tests. It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution, the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges. For the Sardinia bentonite/claystone mixture, the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions, suggesting insignificant cation exchanges. Additionally, the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures. The large-pore volume increased consequently and enhanced water flow. In the cement solution, the hydroxide could also dissolve the montmorillonite, reducing the swelling pressure, and increase the large-pore volume, facilitating the water flow. Furthermore, the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.

ANALISIS PENINGKATAN NILAI CBR LEMPUNG PLASTISITAS TINGGI TERSTABILISASI SEMEN DAN ABU DASAR

Improvement of soft clay with cement, lime, asphalt, and other additives has been done for few decades. Utilization of waste materials i.e gypsum, marble, rubber; rice hush ash, cane hush ash, saw-dust ash etc. The industrial wasted usage from coal burning process as pozzolanic agent has been proven improving the physical and mechanical properties of soil. This study aims to determine effect of bottom ash combined with cement to improve strength and permeability of high plasticity clay. CBR and hydraulic conductivity tests in the laboratory were carried out to study the changes. Several variations fraction of bottom ash (5%/10%/15%) and cement (3%/5%) were determined in this study. curing processes for 7 days and 28 days was carried out before testing the CBR and permeability. The test results of CBR and permeability of clay were 0.78% and 6E-09 m/sec, respectively. The addition of 3% cement and 5% bottom ash does not qualify soil as aggregate of sub-grade because the CBR value is <12%. The best value was at fraction of 5% cement and 15% bottom ash, with CBR value of 38.60% and k=3.99E-08 m/s. The higher content of cement or bottom ash and curing time, soil properties are better. Composition of 5% cement and bottom ash on ranges of 10%-15% can be used as sub-grade. Keywords: bottom ash, curing, hydraulic conductivity, soaked, stabilization, CBR

Hydraulic and physicochemical properties of dense thin bentonite layers permeated with variably mixed alkaline solutions of KOH and CaCl2 at various temperatures (25–75 °C) for 3 years

Hydraulic conductivity tests were performed using mixed alkaline solutions of KOH and CaCl2 (pH ∼12) on thin Na-bentonite layers under various temperature conditions (25–75 °C) for 3 years. For dense thin Na-bentonite (dry density of 1.12 Mg/m3) in a mixed alkaline solution of 0.03 M KOH and 0.03 M CaCl2, the hydraulic conductivities at 50 °C and 75 °C were approximately 10 times higher than that at 25 °C. The bentonite samples permeated with the mixed solution at 50 °C and 75 °C achieved almost complete cation exchange of Na ions by Ca and K ions. However, only slight cation exchange occurred in the bentonite specimens permeated at 25 °C, regardless of the type of permeant. The free swell index of the reacted bentonite permeated with a mixed solution of 0.03 M KOH and 0.03 M CaCl2 significantly decreased at 50 °C and 75 °C compared with that at 25 °C. X-ray diffraction analysis revealed that the decreases in the relative intensities of the peaks of accessory minerals, such as opal-cristobalite/tridymite, quartz, and feldspar, were enhanced at 50 °C and 75 °C.

Comparative research on the application of slag as an alternative to cement in binder-bentonite cutoff wall backfills

Slag, as a kind of industrial by-product, is a recognized substitute for cement to reduce carbon emissions and costs in engineering construction. This paper compares the differences in the performance of sand-sodium silicate-activated slag-bentonite (S-SM-S-B) and sand-cement-bentonite (S-C-B) cutoff wall backfills to investigate the feasibility of S-SM-S-B backfills for practical application. Engineering properties are tested by the hydraulic conductivity (k) test and unconfined compressive strength (UCS) test. The results show that compared with S-C-B backfills, S-SM-S-B backfills with high binder content have the characteristics of higher strength, faster curing rate and better impermeability. The S-SM-S-B backfills are hence more cost-effective for the sites with complex in-situ stress conditions. The strength of S-SM-S-B backfills with less than 5% ground granulated blast-furnace slag (GGBS) dosage is below the commonly suggested limit (100 kPa) and should be avoided in applications. In addition, the damage extent for bentonite particles during hydration of binders was evaluated using the methylene blue value test. Methylene blue values of S-SM-S-B backfills are larger than that of S-C-B backfills, which means that bentonite is less affected in S-SM-S-B backfills. It is hence more conducive to perform the adsorption capacity of added bentonite. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) experiments were carried out to determine the reaction products and microscopic properties of the samples, and the results can verify the above conclusions. At last, the interaction process among raw materials and the control factors for backfill properties are explained based on the double layer theory and hydration reaction mechanism.

Soil physical properties and slope stability in Serra do Mar, southeastern Brazil

Soil physical properties play an important role in landslide rupture mechanisms, since changes in soil texture, structure, and porosity can affect slope permeability. This study characterized a granitic weathering profile and assessed the changes in the properties of the materials related to the main mechanisms that trigger landslides. The study identified three layers with distinctive particularities in macromorphological and micromorphological terms: mature residual soil (well-developed), young residual soil (saprolitic soil), and saprolite. Morphological characterization was carried out in addition to textural analysis, and soil porosity and saturated hydraulic conductivity (Ksat) tests. The weathering profile presented clear differences in morphology, pore size and soil texture, which could indicate distinct weathering grades. The results suggested that continuous heavy rainfall could contribute to the increase in pore-water pressure between mature residual soil and young residual soil, favoring the occurrence of slope failure.

Fresh and hardened properties of cemented paste backfill: Links to mixing time

Current technical knowledge is insufficient regarding the influence of mixing time on fresh and hardened properties of cemented paste backfill (CPB). This work focused on experimental studies to gain a deeper understanding of the influence of mixing time on the rheological properties (yield stress, viscosity), self-desiccation, permeability and mechanical properties or behavior (strength, deformation behavior) of CPB. A series of CPB specimens were prepared with various mixing times (1, 2, 4, 7, 10, and 15 min) and cured at different times (1, 2, 4, 7, 10 and 15 min) for rheological property testing. Unconfined compressive strength (UCS), hydraulic conductivity and microstructural tests were performed on CPBs that were made with various mixing times and cured for different times (up to 90 days). Monitoring experiments were also carried out on CPBs prepared with various mixing times. The results obtained indicate that the mixing time significantly affects the rheological, mechanical, hydraulic and microstructural properties of CPB. Moreover, the self-desiccation of CPB is a function of the mixing time. A longer mixing time increased the yield stress and decreased the viscosity. The longer mixing time promoted binder dissolution and hydration in the CPB, which increased the amount of hydration products and decreased the volumetric water. Longer mixing time intensified the CPB self-desiccation, which is beneficial for the early age mechanical strength of CPB. CPB specimens made with longer mixing time experienced a higher strength and elastic modulus due to the generation of more cement hydration products and the reduction of the volume of pores in CPB. A longer mixing time reduced the CPB hydraulic conductivity, due to the refinement of the CPB pore structure. This study provides relevant knowledge and technical information that will contribute to the design of more cost-effective and sustainable CPB structures.

Saturated hydraulic conductivity of boreal peat and its relationships with peat properties and sampling depth

AbstractThe boreal region is a significant peat‐forming area. With peat, there lie other natural resources, including mineral ores and fossil fuels needed by our economy. However, mining for mineral resources or any other activity that leads to large‐scale groundwater extraction in the near vicinity or underneath the mires can alter the water levels in the overlaying ecosystems and thus have a damaging effect on them, raising concerns about the mires' preservation. Peat itself may isolate surface vegetation from drainage caused by nearby mining when its hydraulic conductivity is sufficiently low. More is known about the hydraulic properties of the uppermost layers of the peat column, but there is very little data about deeper, generally more decomposed peat layers that may potentially act as drainage barriers. Carrying out in situ hydraulic conductivity tests in less conductive peat can be laborious and time‐consuming, and not always practical. This research aims to study and verify statistical relationships between easy‐to‐measure peat properties and hydraulic conductivity over the entire peat column, covering the knowledge deficit that is important in the context of indirect drainage effects related to mining or any other large‐scale groundwater extraction. For that, we sampled peat and conducted in situ saturated hydraulic conductivity tests in several mires in northeast Estonia to gather information about the hydraulic properties of boreal peat. Collected data were fitted with linear mixed‐effects models to link hydraulic conductivity with the degree of decomposition, dry bulk density, depth of measurement, and peatland growth phase. The results indicate that these parameters are strongly correlated with saturated hydraulic conductivity and can serve as predictors of this parameter. Constructed statistical models exhibit relatively high explanatory power and show potential usage for characterizing the hydraulic conductivity of peat. The findings of this study may be helpful in the efforts of mire conservation.

Predicting Hydraulic Conductivity for Flexible Wall Conditions Using Rigid Wall Permeameter

The hydraulic conductivity is known as the soil properties that mostly vary over an order of magnitude. There are many laboratory test methods to determine the hydraulic conductivity of the soil. Each test has its own merits, drawbacks and limitations. One of these methods is the measurement using a rigid wall permeameter (RWP), which is a common practice to obtain the fluid transmissibility characteristics of the soil matrix. This type of permeameter has the advantages of low cost, simplicity of test equipment, and adaptability to many different types of permeant liquids. Another method is the measurement through a flexible wall permeameter (FWP). The hydraulic conductivity measured using the FWP is conducted in a confined cylinder in which water flow is forced into one direction. The main disadvantage of this type is being relatively more expensive and needs more time to perform the test compared to the RWP. This study is aimed at comparing three testing conditions to obtain an adjustment factor for the hydraulic conductivity test normally carried out in practice in order to cut down the time needed to perform the test as well as its cost. Different mixtures of sand and expansive clay addition were considered to examine the effect of expansive clay content on the values of the hydraulic conductivity. Tests results revealed that the clay content had a significant effect on the swelling potential, which was attributed to structural changes in the mixtures. The hydraulic conductivity of mixtures decreases with the increase in clay content. The hydraulic conductivity of mixtures tested using FWP was observed to be lower than that of mixtures tested using RWP at similar clay contents. The tests conducted enabled establishing a correction factor to adjust the hydraulic conductivity normally obtained in practice using rigid wall cells.

Enhanced contaminant retardation by novel modified calcium bentonite backfill in slurry trench cutoff walls

This study aimed at assessing containment properties of slurry wall backfill containing sodium hexametaphosphate (SHMP) modified calcium bentonite to contaminated groundwater. Free swell index and flexible-wall hydraulic conductivity (k) tests were conducted to investigate swelling and hydraulic performances of this novel backfill. The relative concentration (RC) and cumulative mass ratio (CMR) methods were adopted to assess transport parameters including hydrodynamic dispersion coefficient (D) and the retardation factor (Rd) of calcium ion (Ca2+) through the backfills. The results showed negligible to moderate decrease in the swell index of the modified bentonite and the modified backfill when exposed to 5 mM and 1 M calcium chloride (CaCl2) solution. Permeation with CaCl2 solutions increased the short-term k of the backfill by a factor of 0.9 to 1.1 as compared to the tap water permeation. The D values varied from 1.44 × 10–10 m2/s to 2.89 × 10–10 m2/s regardless of the CaCl2 concentration, whereas Rd was vulnerable to CaCl2 concentration. The CMR method yielded a higher coefficient of determination than the RC method, but it showed no particular advantage in evaluating the transport parameters. The SHMP-modification delayed the breakthrough time of Ca2+ by a factor of 15 to 199 in a model slurry trench wall.

Hydraulic Conductivity and X-Ray Diffraction Tests of Unsaturated Bentonites with a Multi-Ring and Their Predictions by Pores Distributions

Hydraulic Conductivity and X-Ray Diffraction Tests of Unsaturated Bentonites with a Multi-Ring and Their Predictions by Pores Distributions

Effect of incineration ash leachates on the hydraulic conductivity of bentonite-polymer composite geosynthetic clay liners

A study was conducted to evaluate the hydraulic conductivity (k) of six bentonite-polymer composite (BPC) geosynthetic clay liners (GCLs) using five synthetic municipal solid waste incineration ash (IA) leachates with ionic strength (I) ranging from 174 to1978 mM. The BPC GCLs contained a dry blend of bentonite and proprietary polymers and had polymer loading ranging from 0.5 to 5.5%. The polymers used in the BPC GCLs were classified as linear polymer (LP) or crosslinked polymer (CP) based on the swelling characteristics of specimens extracted from the GCLs. Comparable hydraulic conductivity tests were also performed on two conventional bentonite (CB) GCLs as controls. The BPC GCLs had k of 2.6 – 6.7 × 10-11 m/s when permeated with IA leachate with I = 174 mM, whereas the CB GCLs had k > 5.0 × 10-8 m/s when permeated with the same leachate. However, k of the BPC GCLs ranged from the order of 10-10 to 10-7 m/s when permeated with IA leachates with I > 600 mM. BPC GCLs with high polymer loading generally had lower k compared to those with lower polymer loading when permeated with the same IA leachate, regardless of the polymer type. Polymer eluted from the BPC GCLs containing LP during permeation with DI water or IA leachate. Unlike CPs, LPs are water-soluble, therefore, they seem to easily migrate during permeation. There was no correlation between the percentage of polymer retained and the final hydraulic conductivity of the LPB GCLs used in this study.

Hydraulic conductivity testing and destructive sampling of field-scale mine waste test piles

A commingled waste rock and tailings test pile and a waste rock test pile were evaluated to determine saturated hydraulic conductivity and destructively sampled to measure dry density. The commingled test pile contained a mixture of filtered tailings and waste rock blended to isolate waste rock particles as inclusions within the tailings matrix. Test piles were constructed in the shape of truncated 5 m high pyramids with 25 m base sides and flat 5 m × 5 m top surfaces, and instrumented to monitor water content (and additional geochemical indicator parameters) within the test pile and seepage from the base of the pile. Piles were decommissioned after 26 months of operation. Saturated hydraulic conductivities were measured using sealed double-ring infiltrometers (2.4 m square outer ring and 1 m square inner ring). Tensiometers and embedded water content sensors were used to measure progression of the wetting front, and the final location of the wetting front in the commingled test pile was directly measured during decommissioning. Field-measured saturated hydraulic conductivities were compared to laboratory-measured results intended to simulate the test piles. Despite having a lower average density, the commingled waste rock and tailings had a hydraulic conductivity approximately 2.5 times lower than the waste rock.