Long-term measurement of matric suction using thermal conductivity sensors

2003 ◽  
Vol 40 (3) ◽  
pp. 587-597 ◽  
Author(s):  
Craig Nichol ◽  
Leslie Smith ◽  
Roger Beckie
Keyword(s):  
Thermal Conductivity ◽  
Ambient Temperature ◽  
Water Movement ◽  
Mine Waste ◽  
Matric Suction ◽  
Waste Rock ◽  
Sensor Data ◽  
Wetting Front ◽  
Conductivity Sensor

Thermal conductivity (TC) sensors, which provide estimates of matric suction, were used in a field experiment designed to characterize unsaturated water movement through coarse mine waste rock at a mine site in northern Saskatchewan. Two years of monitoring data were used to evaluate long-term TC sensor performance and accuracy. Thermal conductivity sensor output requires corrections of sensor hysteresis and changes in ambient temperature. A correction method for ambient temperature is derived. A comparison of the uncorrected field measurements with the values corrected for both hysteresis and ambient temperature indicates that the magnitude of these corrections can be similar. Corrected TC sensor measurements are compared to measurements of matric suction made using tensiometers. Thermal conductivity sensor response to the initial arrival of a wetting front lagged 1–3 days behind the tensiometer measurements. The TC sensor data tended to overestimate matric suction in the waste rock, when compared to the tensiometer data. Long-term drift in the TC sensors located at depths of 50 cm and below (where the sensors have been continuously exposed to matric suctions less than 20 kPa) has lead to data that are not interpretable using the calibration curves derived prior to sensor emplacement in the waste rock pile.Key words: matric suction, thermal conductivity sensor, hysteresis, temperature.

Numerical Simulation of Water Flow in Mine Waste Rock Pile

2015 ◽  
Vol 744-746 ◽  
pp. 1101-1108
Author(s):  
Meng Zhou Zhang ◽  
Zeng He Xu ◽  
Li Guo Jiang
Keyword(s):  
Unsaturated Flow ◽  
Water Movement ◽  
Mine Waste ◽  
Waste Rock ◽  
Rock Pile ◽  
Fine Material ◽  
Internal Structures ◽  
Waste Rock Pile ◽  
Mine Waste Rock

As a long-term source of contaminant solutes, the flow of water within a waste rock pile containing reactive sulfide minerals significantly contributes to the solutes transportation. In this paper, a waste rock pile with the internal structures and grain size distribution from a typical waste dump is introduced as the geometric configuration. A numerical model is then applied to simulate unsaturated flow within a waste rock pile constructed with two primary materials. The simulations results show that the water movement within heterogeneous pile mainly depended on the internal structures. The flow of water can be controlled by the fine material layers within the coarse materials. These fine material layers form a capillary barrier which preventing the water infiltrate towards the centre of the pile. They can retain more water than coarse materials and form a ponding effect and/or percolation points within the pile.

Installation procedure for thermal conductivity matric suction sensors and analysis of their long-term readings

2007 ◽  
Vol 44 (2) ◽  
pp. 113-125 ◽  
Author(s):  
Elsa Tan ◽  
Delwyn G Fredlund ◽  
Brent Marjerison
Keyword(s):  
Thermal Conductivity ◽  
Ambient Temperature ◽  
Membrane System ◽  
Matric Suction ◽  
Soil Suction ◽  
Correction Factors ◽  
Temperature Changes ◽  
Subgrade Soil ◽  
Long Term Measurement

Thermal conductivity matric suction sensors have enabled continuous and long-term measurement of matric suction and temperature, even in remote locations. Long-term temperature and matric suction readings were obtained from below two thin-membrane-system sites in Torquay and Bethune, Saskatchewan. The method used to install the sensors and the data acquisition system is presented. An understanding of the subgrade soil suction and temperature changes throughout the year was obtained from the data. The change in matric suction and temperature with depth and distance was also determined. Observation of the amplitude and frequency of the fluctuations in the temperature readings provided a better understanding of the changing trends. Environmental effects, such as hysteresis associated with drying and wetting of the sensors and the effect of the ambient temperature on the sensors, were found to influence the matric suction readings. Several correction factors have been proposed to eliminate the influence of the ambient temperature, and the correction methods are compared.Key words: thermal conductivity, matric suction, sensors.

Hydraulic Conductivity Testing and Destructive Sampling of Field-Scale Mine Waste Test Piles

2021 ◽  
Author(s):  
Mohammad R. H. Gorakhki ◽  
Christopher Bareither ◽  
Joseph Scalia
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Mine Waste ◽  
Average Density ◽  
Waste Rock ◽  
Dry Density ◽  
Wetting Front ◽  
Destructive Sampling ◽  
Double Ring ◽  
Test Pile

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 tall 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.

Use of thermal conductivity sensors to measure matric suction in the laboratory

1989 ◽  
Vol 26 (3) ◽  
pp. 491-498 ◽  
Author(s):  
Pamela Sattler ◽  
D. G. Fredlund
Keyword(s):  
Thermal Conductivity ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Test Procedure ◽  
Matric Suction ◽  
Engineering Practice ◽  
Equilibration Time ◽  
Overburden Pressure ◽  
Conductivity Sensor

The measurement of soil suction is pivotal to the application of soil mechanics principles in geotechnical engineering practice related to unsaturated soils. Volume change, shear strength, and seepage analyses all require an understanding of the matric suction in the soil. This note summarizes the use of thermal conductivity sensors to measure matric suction in the laboratory. The thermal conductivity sensor is described along with its mode of operation. A brief description is given of the procedure for calibrating thermal conductivity sensors using a pressure plate apparatus. The measurement of matric suction can be performed in the laboratory on Shelby tube samples. The laboratory measurements of matric suction can be adjusted for the effect of overburden pressure in the field. The required equilibration time for suction measurements is discussed along with details of the test procedure. The applications of the measured suction values to design are briefly discussed.Key words: matric suction, negative pore-water pressure, thermal conductivity sensor, laboratory, undisturbed samples.

An investigation of the ambient temperature field and thermal response of the Calgary Airport Trail Tunnel

2018 ◽  
Vol 45 (12) ◽  
pp. 1015-1026
Author(s):  
Lomere Mori ◽  
Mustafa Gül ◽  
Roger Cheng ◽  
Ved Sharma
Keyword(s):  
Ambient Temperature ◽  
Thermal Response ◽  
Sensor Data ◽  
Gradient Effect ◽  
Direct Design ◽  
Road Tunnels ◽  
Tunnel Design ◽  
Temperature Loads ◽  
Structural Code

Currently, there is a lack of direct design provisions in structural codes and literature that address design temperatures in tunnel structures and thus it is common practice for designers to resort to bridge codes. The main focus of this paper is the study of the temperature distribution in concrete road tunnels due to ambient temperature. In this context, the temperature distributions of the Airport Trail Tunnel in Calgary, Alberta is studied using numerical modelling and long-term temperature monitoring data collected from the tunnel. The overall aim is to evaluate findings from the numerical analysis and sensor data with current Canadian structural code provisions considered in tunnel design in regards to temperature loads. From the investigation, it is determined that the design temperature range was within CSA S6, however CSA S6 underestimates the temperature gradient effect in the walls and slabs of the tunnel under study.

scholarly journals Calibration of a thermal conductivity sensor for field measurement of matric suction

Géotechnique ◽  
2012 ◽  
Vol 62 (1) ◽  
pp. 81-85 ◽  
Author(s):  
E.C. LEONG ◽  
X.-H. ZHANG ◽  
H. RAHARDJO
Keyword(s):  
Thermal Conductivity ◽  
Field Measurement ◽  
Matric Suction ◽  
Conductivity Sensor

scholarly journals Mine Waste Rock: Insights for Sustainable Hydrogeochemical Management

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 728
Author(s):  
Bas Vriens ◽  
Benoît Plante ◽  
Nicolas Seigneur ◽  
Heather Jamieson
Keyword(s):  
Environmental Impacts ◽  
Reactive Transport ◽  
Large Scale ◽  
Mine Waste ◽  
Analytical Techniques ◽  
Waste Rock ◽  
Future Research ◽  
Testing Procedures ◽  
Mine Waste Rock

Mismanagement of mine waste rock can mobilize acidity, metal (loid)s, and other contaminants, and thereby negatively affect downstream environments. Hence, strategic long-term planning is required to prevent and mitigate deleterious environmental impacts. Technical frameworks to support waste-rock management have existed for decades and typically combine static and kinetic testing, field-scale experiments, and sometimes reactive-transport models. Yet, the design and implementation of robust long-term solutions remains challenging to date, due to site-specificity in the generated waste rock and local weathering conditions, physicochemical heterogeneity in large-scale systems, and the intricate coupling between chemical kinetics and mass- and heat-transfer processes. This work reviews recent advances in our understanding of the hydrogeochemical behavior of mine waste rock, including improved laboratory testing procedures, innovative analytical techniques, multi-scale field investigations, and reactive-transport modeling. Remaining knowledge-gaps pertaining to the processes involved in mine waste weathering and their parameterization are identified. Practical and sustainable waste-rock management decisions can to a large extent be informed by evidence-based simplification of complex waste-rock systems and through targeted quantification of a limited number of physicochemical parameters. Future research on the key (bio)geochemical processes and transport dynamics in waste-rock piles is essential to further optimize management and minimize potential negative environmental impacts.

Numerical Simulation of Water Movement in the Suction Equalization of a Thermal Conductivity Sensor

2003 ◽  
Vol 26 (2) ◽  
pp. 9916 ◽  
Author(s):  
L David Suits ◽  
TC Sheahan ◽  
F Shuai ◽  
DG Fredlund ◽  
L Samarasekera
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Water Movement ◽  
Conductivity Sensor

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.

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