Interface parameters for earth-structure interaction during mining-induced subsidence

Mining-induced subsidence under existing structures is capable of causing extensive structural damage. As a result, mitigation techniques, such as reducing friction at the soil-structure interface, have been developed to minimize damage. This investigation examines the technique of placing various materials under foundations to reduce friction. A hyperbolic model, in order to allow future numerical analyses, is presented to characterize this type of interface behavior.

A series of direct shear tests were performed on various interface combinations of soil and construction materials such as; clay-plastic sheet, clay-smooth concrete, clay-rough concrete, sand-plastic sheet, sand-smooth concrete, and sand-rough concrete. The interfaces were tested over a range of normal stresses which includes the typical stresses to which a residential or light commercial facility foundation might be subjected. For each interface combination, shear strength, shear stiffness, and hyperbolic model parameters were determined.

For the typical stresses in residential foundations, the mitigation technique of placing plastic on sand appears to be effective in reducing friction. However, laboratory data indicates that soil overlain with plastic should prove to be a better choice in reducing the amount of stress transfer to the footing. With the aid of numerical analysis techniques using interface parameters determined from this investigation, the effectiveness of these techniques can now be thoroughly examined.