Advanced Slope Monitoring System Todevelop Trigger Action Response Plan (Tarp) in Opencast Coal Mines Using Internet of Things (Iot)

Abstract

In India, coal is the main energy source used to generate electricity and for other industrial purposes. Since coal-based thermal power plants account for a sizable share of India's electricity generation, the demand for coal rises drastically. India currently imports coal from other nations to meet its domestic needs. In India more than 96% coal is produced from opencast mines. Opencast (OC) mines are progressively becoming deeper to meet the increasing demand of coal. Lager and deeper opencast mines result in unstable slopes, leading to slope failures, which pose a major challenge. Slope stability and its monitoring is a serious issue in OC mines. In current scenario, conventional methods are being used for slope monitoring in opencast mine. Such monitoring typically requires a person to be physically present at the site and can only be carried out during the day. On the other hand, Slope Stability Radar (SSR) and Light Detection and Ranging (LiDAR) can monitor slope movements effectively but these are expensive, works on day time only and physical presence of persons required. In order to address this ambiguity, an advanced slope monitoring system is essential. This system should utilize low-cost sensors to monitor parameters affecting slope stability and provide early alerts by analyzing sensor data in real-time. Based on a comprehensive literature review identified, moisture content, vibrations, and displacement are the key factors contributing to slope instability. So, in this study, a slope monitoring system was designed using soil moisture, vibration and displacement sensors to detect and monitor these parameters. This system incorporates Wireless Sensor Networks (WSN) and Cloud Computing Technologies (CCT), enabling early warning alerts via email and SMS when pre-set threshold values are exceeded. The system was developed and implemented in three case study opencast mines. Additionally, a Trigger Action Response Plane (TARP) was formulated based on the rate of displacement and total displacement by the means of Wireless Sensor Networks, existing total station monitoring system, numerical modelling parametric study, that provides guidelines for actions to be taken at various levels of slope stability based on alerts from the monitoring system aided to develop a i user-friendly Advanced Slope Monitoring System (ASMS) software. This system was evaluated for its functions and performance through a laboratory experimentation on a physical slope model after the sensors were calibrated using reliable instruments. Based on the laboratory experiments, soil moisture sensors recorded a maximum of 82% and minimum of 25%. For vibration sensor, a maximum of 80 Hz and minimum of 0 Hz was detected, and 0.25 mm and 5.3 mm displacement is recorded without load and with load condition respectively. While evaluating the effect of soil moisture and vibration on slope displacement, it is identified that the moisture content in the slope has more impact on slope displacement than vibration. Laboratory investigations gave encouraging results on reliability and effectiveness of the developed system to perform field investigations in three different mines. From the field investigations, Kakatiya Khani Opencast-2 Project case study recorded the highest average rate of displacement of 2.12 mm/day, 75% moisture content and 36 Hz vibration. Khairagura Opencast Project recorded 3.27 mm/day rate of displacement, soil moisture content 78% and 28 Hz vibration, at Srirampur Opencast 2 Project rate of displacement is 3.57 mm/day with moisture 82% and 30 Hz vibration. Data collected from the mines of existing total station monitoring system and previous slope failure cases revealed the following observations, upto 50 mm displacement slopes are stable, between 50 mm to 100 mm cracks are generated and from 100 mm to 150 mm indicates potential failures are observed and above 150 mm failures observed. Later, Slope displacement obtained from Wireless Sensor Networks system of case study mines were compared with the displacement readings from the total station and numerical model of the slope that was being monitored. Results obtained at case study-1 mine for displacement through Wireless Sensor Networks system is 25.50 mm (minimum) and 46.80 mm (maximum), through total station monitoring system is 27 mm (minimum) and 49.30 mm (maximum). Similarly, the minimum and maximum displacement through numerical modeling are 29.77 mm and 46.26 mm ii respectively. The percentage of error while comparing with Wireless Sensor Networks and Total Station is below 11.47%, and WSN and NMM methods is not more than 16.75%. Hence, Wireless Sensor Networks based slope monitoring system data is very reliable. Parametric study conducted using numerical modelling studies with varying rock properties and slope geometry. A regression equation is developed for displacement and Factor of Safety (FoS). Advanced Slope Monitoring System (ASMS) software is developed based on the derived equations to track the behavior of slopes in opencast mines. Trigger Action Response Plan (TARP) has been developed based on the field investigations of case study mines. Level 1 indicates, for displacement rates below 0.3 mm/day and total slope movement under 10 mm, recommends a weekly monitoring. Level 2 indicates, rate of displacement between 0.3 mm/day to 10 mm/day and total displacement between 10 mm to 50 mm suggests weekly monitoring and slope indicates no cracks, Level 3 indicates, rates between 10 mm/day to 50 mm/day, and 50 mm to 100 mm total displacement, suggests monitoring every two days and slope indicates with crack. Level 4, rate of displacement between 50 mm/day to 100 mm/day, and total displacement between 100 mm to 150 mm recommends daily monitoring indicating potential failure. Level 5 for rate of displacement exceeding 100 mm/day and total displacement exceeding 150 mm failure takes place and suggesting clearing the area.