I've been tasked with estimating the remaining time to required repairs for a tubular corrugated steel structure with a potash/mining muck backfill and traffic over the backfill. The tube was placed in a mining drift and the perpendicular drift above has the traffic.
The side of the tubes are tending to displace laterally (inward) creating a vertical ellipsoidal cross-sectional shape in the tube. The tube wall's lateral displacement is not accelerating, but it is steady as identified using scan data gathered over the years. In my experience, tubular structures like this in non-mining applications tend to displace vertically down through time into a horizontally-orientated ellipsoid. My initial take is that the tube wall's lateral displacement is likely occurring as a result of the drift tending to collapse (i.e., rock mechanics stuff).
My primary interest of respondents is to provide recommendations for FEA material constitutive models for the potash/much backfill. I'm intending to prepare an FEA model with a rolling axle load over the tubular structure with the backfill in place to try to identify any backfill or steel plasticity as a result of the rolling load. I have only basic FEA software at my disposal, so I'm hoping to use an elastic-perfectly plastic material model for the steel and backfill if I identify any yielding potential in a elastic model. My theory is that if there's no plasticity as a result of the rolling load then we can safely blame the closing drift for the observed defects and extrapolate when the drift will close the tube too far to be serviceable. We may try to model the closing drift as well by displacing the boundaries using an elastic/plastic model.
Any advice will be welcome.
The side of the tubes are tending to displace laterally (inward) creating a vertical ellipsoidal cross-sectional shape in the tube. The tube wall's lateral displacement is not accelerating, but it is steady as identified using scan data gathered over the years. In my experience, tubular structures like this in non-mining applications tend to displace vertically down through time into a horizontally-orientated ellipsoid. My initial take is that the tube wall's lateral displacement is likely occurring as a result of the drift tending to collapse (i.e., rock mechanics stuff).
My primary interest of respondents is to provide recommendations for FEA material constitutive models for the potash/much backfill. I'm intending to prepare an FEA model with a rolling axle load over the tubular structure with the backfill in place to try to identify any backfill or steel plasticity as a result of the rolling load. I have only basic FEA software at my disposal, so I'm hoping to use an elastic-perfectly plastic material model for the steel and backfill if I identify any yielding potential in a elastic model. My theory is that if there's no plasticity as a result of the rolling load then we can safely blame the closing drift for the observed defects and extrapolate when the drift will close the tube too far to be serviceable. We may try to model the closing drift as well by displacing the boundaries using an elastic/plastic model.
Any advice will be welcome.
