Performance of industrial fly ash based stabilized mine haul roads under seasonal moisture changes

Mine haul roads play an important role in the mining industry. They are often designed as unsealed roads, which are frequently damaged due to seasonal moisture variation, especially when the subgrade soil is expansive clay. In this study, the performance of mine haul roads built on expansive clay soil is investigated for seasonal moisture variation using experimental and numerical investigations. Shrinkage, swelling, soil water characteristics curve (SWCC) tests, and direct shear testing were first performed to assess the hydraulic and shear performance of the control and municipal solid waste incineration (MSWI) fly ash-treated soils. The swelling reduced from 1.95 to 1.02, while the shrinkage reduced from 3.4% to 1.84% after the addition of 20% MSWI fly ash. SWCC results showed that the MSWI fly ash addition reduces the void spaces and increases residual saturation. The consolidation settlement reduced by 50% after adding 20% MSWI fly ash. The cohesion of both soil and MSWI fly ash-treated samples exhibited a bell-shaped trend with moisture increase, in contrast to friction angles which decreased with increasing saturation levels. 3D numerical models were used to predict the performance of control soil and MSWI stabilized mining haul roads using the experimental test data. The control pavement experienced increased settlement and rutting as saturation levels increased. The behaviour of the stabilized pavement differed, with the model having a 20% degree of saturation showing the least deformation due to increased stiffness from high suction. Overall, this study highlights the benefits of MSWI fly ash-based soil stabilization in improving the performance of mine haul roads under seasonal moisture changes. The findings emphasize the importance of considering the degree of saturation and stabilization techniques in pavement design to mitigate settlement and enhance overall performance.