Instrumentation and monitoring of an engineered soil cover system for mine waste rock

1998 ◽  
Vol 35 (5) ◽  
pp. 828-846 ◽  
Author(s):  
M O'Kane ◽  
G W Wilson ◽  
S L Barbour
Keyword(s):  
Soil Cover ◽  
Mine Waste ◽  
Characteristic Curve ◽  
Matric Suction ◽  
Waste Rock ◽  
Degree Of Saturation ◽  
Gaseous Oxygen ◽  
Climate Conditions ◽  
Cover System ◽  
Waste Rock Piles

The ability of the soil cover system at the Equity Silver Mine to limit oxygen and water fluxes to underlying waste rock was evaluated using a detailed instrumentation program. Field instrumentation was installed to monitor temperature, gaseous oxygen, and gaseous carbon dioxide in the waste rock piles. Lysimeters were constructed at the base of the soil cover system to monitor infiltration across the soil cover. Sensors to measure matric suction, soil temperature, and water content were installed. An automated weather station was also installed to monitor climate conditions at the mine site. The field data indicates that the lower compacted layer maintained a high degree of saturation (i.e., 90% or higher) during 3 years of data collection (August 1992 to August 1995). This is a positive result, since the lower compacted layer was designed as an oxygen limiting barrier. The average measured infiltration from lysimeters placed at the base of the soil cover system was 5% of precipitation (from October 1992 to August 1993). The measured matric suction data indicates that the hydraulic gradient within the soil cover system is predominantly upward except for relatively short periods of heavy rainfall and snow melt in late fall and early spring.Key words: waste rock, soil cover, instrumentation, monitoring, unsaturated soil, soil-water characteristic curve.

Design of a composite soil cover for an experimental waste rock pile near Newcastle, New Brunswick, Canada

1993 ◽  
Vol 30 (4) ◽  
pp. 578-587 ◽  
Author(s):  
Ernest K. Yanful ◽  
Alan V. Bell ◽  
Mark R. Woyshner
Keyword(s):  
New Brunswick ◽  
Soil Cover ◽  
Acid Rock Drainage ◽  
Mine Waste ◽  
Gas Diffusion ◽  
Climatic Conditions ◽  
Waste Rock ◽  
Freezing And Thawing ◽  
Gaseous Oxygen ◽  
Acid Rock

The Heath Steele Waste Rock Project was initiated in 1989 under Canada's Mine Environment Neutral Drainage (MEND) Program to develop and test strategies for managing acid-generating waste rock. The multiphase project involved the identification and selection of a few waste rock piles for field evaluation at the Heath Steele mine site located at about 50 km northeast of Newcastle, New Brunswick. As part of the evaluation, a 0.25-ha acid-generating pile, pile 7/12, was relocated and reconstructed on an impermeable synthetic membrane by end dumping from the perimeter and pushing into the middle section. The pile, which contains about 14 000 t of mine waste rock, has been producing an acidic seepage characterized by high dissolved iron (3.5–13.5 g/L) and sulphate (12.7–43.4 g/L) concentrations. Following the definition of the baseline acid-generating characteristics of the pile and laboratory investigation of potential soil cover materials in the vicinity of the site, a three-layer cover design is proposed. The design calls for a 60 cm thick saturated impermeable cover sandwiched between a 30 cm thick sand base and a 30 cm thick, overlying granular layer. The principal objectives of the design are to obtain a low gas diffusion coefficient to minimize oxygen fluxes and, also, to attain a low hydraulic conductivity to reduce infiltration into the pile. Both objectives can be achieved by compacting the impermeable cover at a density of 95% of Modified Proctor or greater and a water content slightly higher than the optimum value. The design of the cover and the anticipated resulting low gaseous-oxygen fluxes are confirmed by one-dimensional diffusion modelling. The potential for the impermeable layer to remain nearly fully saturated, even under an evaporative flux, is demonstrated by flow modelling. It is noted that the assessment of the durability of the cover with respect to variable climatic conditions (drying, freezing, and thawing) is a critical component of the performance evaluation. Key words : acid rock drainage, soil cover, capillary barrier, oxygen flux, infiltration.

Variations in moisture content for a soil cover over a 10 year period

2005 ◽  
Vol 42 (6) ◽  
pp. 1615-1630 ◽  
Author(s):  
Björn Weeks ◽  
G Ward Wilson
Keyword(s):  
Moisture Content ◽  
Soil Cover ◽  
Acid Rock Drainage ◽  
Lower Layer ◽  
Mine Waste ◽  
Waste Rock ◽  
Weather Data ◽  
Moisture Profile ◽  
Acid Rock ◽  
Cover Design

The Equity Silver mine is located in north-central British Columbia and is the site of a large, well-instrumented soil cover. The soil-cover site was designed to prevent the generation of acid rock drainage from the acid-generating waste rock disposed of at this site. The cover was designed to act as an oxygen barrier by maintaining a layer of saturated soil above the waste rock. The cover consists of a compacted till placed over the waste rock and covered with a non-compacted layer of the same material. Neutron probes and thermal conductivity sensors were used to monitor the moisture content of the cover soil over a 10 year period. Weather data at the site were also collected. A review of the data collected has shown that saturation was maintained in the lower, 0.5 m thick compacted layer of the cover, as per the original cover design. The upper cover layer (0.3 m of noncompacted till) was subject to seasonal variations in moisture content, with drying in the summer months and wetting in the fall and spring. Variations in the moisture of the upper layer correlated well with the weather data collected at the site. Spatial variations were noted in the water contents measured over the cover, but a nearly saturated lower layer appears to have been maintained throughout the area monitored.Key words: soil cover, neutron probes, moisture profile, mine waste covers.

Unsaturated sloping layered soil cover system: Field investigation

2011 ◽  
Vol 91 (2) ◽  
pp. 161-168 ◽  
Author(s):  
L. K. Tallon ◽  
M. A. O'Kane ◽  
D. E. Chapman ◽  
M. A. Phillip ◽  
R. E. Shurniak ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Cover ◽  
Mine Waste ◽  
Field Performance ◽  
Field Investigation ◽  
Layered Soil ◽  
Slope Position ◽  
Cover System ◽  
Layering Effect ◽  
And Performance

Tallon, L. K., O'Kane, M. A., Chapman, D. E., Phillip, M. A., Shurniak, R. E. and Strunk, R. L. 2011. Unsaturated sloping layered soil cover system: Field investigation. Can. J. Soil Sci. 91: 161–168. Unsaturated soil cover systems are effective in minimizing the interaction of meteoric water with underlying mine waste. Studies detailing field-monitoring results of layered systems in sloping landscapes are scarce. The objective of this paper was to evaluate the field performance, defined as a reduction in percolation, of a sloping fine-over-coarse-layered cover system at a phosphate mine in the northwestern United States. Cover water content profiles were elevated in the underlying waste material during and after wet periods such as spring snow melt, suggesting that any layering effect of increasing storage capacity was lost. During dry periods, water content profiles suggested a slight benefit due to layering, as water contents were slightly elevated immediately above the cover/waste shale interface. Although there were incidental gains in performance due to layering, the majority of the infiltrating water was stored in the fine-textured layer. This layer was most responsible for limiting percolation into the underlying waste. There was little difference in performance due to slope position. The cover was sufficient in preventing net percolation into the underlying waste shale, and performance was at least partially improved by increased storage at layer interfaces.

Model for predicting tensile strength of unsaturated cohesionless soils

2018 ◽  
Vol 55 (9) ◽  
pp. 1313-1333 ◽  
Author(s):  
Penghai Yin ◽  
Sai K. Vanapalli
Keyword(s):  
Tensile Strength ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Friction Angle ◽  
Matric Suction ◽  
Degree Of Saturation ◽  
Engineering Practice ◽  
Cohesionless Soils ◽  
Proposed Model ◽  
Earth Structures

The influence of tensile strength on the behaviour of cohesionless soils is typically ignored in geotechnical engineering practice. However, the tensile cracking and subsequent failure characteristics of earth structures, such as dams, slopes and embankments, are significantly influenced by the tensile strength. For this reason, a semi-empirical model is proposed for predicting the variation of the tensile strength of unsaturated cohesionless soils with the degree of saturation, using the soil-water characteristic curve (SWCC) as a tool. The proposed model is capable of predicting the tensile strength arising from matric suction and surface tension, which are related to saturated pores and to the air–water interface associated with water bridges around interparticle contacts in unsaturated pores, respectively. Information about (i) the matric suction (ua– uw), the capillary degree of saturation (Sc), and the residual degree of saturation (Sr) derived from the SWCC; (ii) the mean particle size (d50) and the coefficient of uniformity (Cu) from the grain-size distribution curve; (iii) the void ratio (e); and (iv) the friction angle ([Formula: see text]) at low normal stress level is required to employ this model. The proposed model is validated by comparing the prediction results with measured tensile strength of 10 different unsaturated cohesionless soils (including five sandy soils and five silty soils). The proposed model is promising for use in engineering practice applications as it only requires conventional soil properties, alleviating the need for cumbersome experimental studies for the determination of tensile strength of unsaturated cohesionless soils.

Long Term Zinc Contamination and Transport at the Abandoned Ore Chimney Mine

2020 ◽  
Author(s):  
Colleen Harper ◽  
Carling Ruth Walsh ◽  
Carrie Fong ◽  
Paul Gammon ◽  
Richard T Amos
Keyword(s):  
Natural Attenuation ◽  
Mine Drainage ◽  
Mine Waste ◽  
Geochemical Modeling ◽  
Waste Rock ◽  
Ph Buffering ◽  
Mine Waste Rock ◽  
Site Water ◽  
Waste Rock Piles ◽  
Co Precipitation

Mine waste-rock piles can release low quality drainage that is harmful to the surrounding environment. Many studies have investigated recently placed waste rock, but fewer have examined geochemical processes within, and downgradient of, old waste rock, even though these processes may be expected to persist for many decades. The Ore Chimney property was the site of gold exploration activities that produced a small waste-rock pile; it was abandoned in 1934. Elevated concentrations of Zn are restricted to within 50 m of the waste rock, and pH remains neutral across the site. Water and sediment analyses and geochemical modeling indicate that several processes are involved in pH buffering and contaminant control. Water samples taken at the edge of the waste rock were not acidic, indicating that mechanisms within the waste rock, including carbonate buffering and preferential oxidation of sphalerite over pyrite, are preventing Acid Mine Drainage (AMD). Natural attenuation mechanisms are operating within wetlands at Ore Chimney with the most likely controls for Zn transport in ground and surface water being carbonate mineral precipitation, co-precipitation with Fe and Mn oxides and oxyhydroxide minerals and Al sulphate minerals, and adsorption onto calcite and organic matter. This investigation shows that, after long time frames, natural attenuation mechanisms may act to effectively immobilize metal contaminants.

Research on the Retention Capacity of Ruins Soil under Drying Condition

2014 ◽  
Vol 580-583 ◽  
pp. 705-710
Author(s):  
Ping Liu ◽  
Hu Yuan Zhang ◽  
Yi Chen ◽  
Xian Xian Shao ◽  
Xin Yuan Fu
Keyword(s):  
Water Content ◽  
Void Ratio ◽  
Characteristic Curve ◽  
Matric Suction ◽  
Soil Samples ◽  
Degree Of Saturation ◽  
Drying Process ◽  
Retention Capacity ◽  
Pore Water Pressures ◽  
The Relationship

The soil water characteristic curve (SWCC) has been tested during the drying process. In order to define the relationship between suction, degree of saturation and void ratio, fitting models of SWCC was established. Studies have shown that the shape of SWCC of three kinds of samples (taken from Jiaohe, Gaochang and Jiuzhoutai) was similar to the inverted “S”, the relationship between water content and matric suction was inversely proportional. Under the condition of the same moisture, the matric suction of the Jiaohe and Gaochang samples were greater than the Jiuzhoutai samples, and the changes of pore water pressures showed the same trend. The degree of saturation began to decrease when the water content reduced to the air entry value. When the degree of saturation was greater than 90%, the volume of soil samples contracted significantly, and when saturation is below 80%, volume shrinkage stopped.

Sign in / Sign up

Export Citation Format

Share Document