Abstract

In this paper, we report on the monitoring and QA methods introduced during construction of the final liners of the shafts of BHP’s Jansen mine. The potash resources of Saskatchewan have been extracted for decades using ever-improving, if traditional, mining methods. The deposits are located at depths between 900 and 1000 m, below a water-bearing formation. The Blairmore formation is a sand-shale-clay-siltstone layer and is the main source of water-threatening mining operations. The long-term operation of these mines is therefore challenging, as they are always at risk of flooding. Since the 1960s, at least 5 shafts have been lost to water ingress, so currently operated shafts are all carefully managed and monitored. The construction method of the waterproof liner combines a fully-welded steel liner covered with a specially formulated concrete liner to guarantee long-term structural stability. The monitoring system introduced in this project measures concrete temperatures in real-time during curing and transmits temperature readings back to the surface. In a ground-surface facility, concrete samples were cured in water baths following the exact same temperature curve as the concrete in the shaft, in real-time, as opposed to a more commonly used fixed curing temperature. This method integrates LoRa-based radios that relay real-time temperatures to programmable logic controllers (PLCs), which then manage the concrete samples temperatures. This automatic control design was enhanced by an online visual tool that allowed real-time computation of maturity curves and temperature gradients. The suite of tools generated alerts and notifications if any of the sensors or loggers stopped responding or returned out-of-range values. The control system scales to monitor and manage up to 24 concrete pours concurrently, offering months-long quality assurance of key lifts. The LoRa architecture was expanded to add remote monitoring of structural health instruments such as strain gauges and jointmeters. This reviewed system has been used to monitor these instruments successfully for the past three years.