Abstract:
Capturing the in-situ state of mine tailings is important in determining its behaviour under
loading for evaluating the risk of failure of tailings dams. Obtaining a high-quality undisturbed sample
through tube sampling is thus of great value to the responsible engineer. However, the sampling process
itself disturbs the soil and changes its state. Since soil behaviour is driven by effective stress, one method to
evaluate the disturbance induced during tube sampling is to monitor the soil’s positive and negative pore
water pressure response during the process. A laboratory study was conducted where tailings samples were
prepared at a controlled void ratio and subsequently saturated with water. Tube samplers of different
diameters were driven into the material and extracted by means of an electric actuator during which internal
sample pore pressures were monitored using tensiometers. The material experienced significant
instantaneous contractive and dilative tendencies during insertion. Instantaneous negative responses during
extraction of the tube samplers were also measured. It was found that the largest tube sampler (100mm
diameter) performed best in the study.
