Using Traditional and Advanced Soil Improvement Techniques for Swelling Soil Heave Mitigation

Swelling soil is one of the most common problematic soils. The swelling phenomenon can cause severe damage to the overlying lightly loaded structures. Many alternatives have been proposed to mitigate the effects of expansive soil on civil foundations such as pre-wetting, sub-drainage, hydraulic barriers, chemical stabilization, and mechanical treatments. Sand replacement is considered to be one of the most effective and practical techniques that can be utilized for the construction of safe foundations. The sand cushion is used in this study as a traditional solution to reduce the heave of the expansive soil. On the other hand, the sand cushion reinforced with triaxial geogrid is used as an advanced solution. An experimental study using a large-scale box model is used to investigate the effect of sand cushion on reduces the heave of the expansive soil. Besides, a parametric study was performed to assess the effect of sand cushion thickness and lateral extension on the heave of the footing. Also, the effect of reinforcing sand cushion with triaxial geogrid was taken into consideration and studied the importance of using it in reducing of the swelling soil heave. The results demonstrated that the use of sand cushion reduces the heave of the footing by increasing the thickness of the sand cushion. Moreover, the reduction rate of heave decreases for sand cushion thickness greater than two-thirds of the footing width. Thus, the optimum thickness of the sand cushion is 2/3 footing width. The footing heave decreases with increasing the lateral extension, Le, of sand cushion, and the rate of reduction of heave becomes negligible when using lateral extension greater than twice thickness of sand cushion. Furthermore, it was concluded that using triaxial geogrid with sand cushion as a reinforcement element leads to reduce heave of the swelling soil due to the tension developed in geogrid. In addition, The maximum reduction percentage of the footing heave is equal to 53.77% when using sand cushion thickness is equal to the width of footing but, the minimum reduction percentage of heave is equal to 35.39% when using sand cushion thickness of 1/3B.