This research introduces a new effective approach, including a weak vertical wall (WVW) and a strong inclined wall (SIW) under a shallow foundation, to reduce the rotations caused by a fault rupture. A series of centrifuge tests, followed by numerical modeling and verified by the test results, were conducted to explore the most suitable characteristics of an inclined wall. It is shown that a WVW is, in some cases, ineffective when it is not in the fault rupture path. Furthermore, uncertainties related to determining the exact location of the fault outcrop make it essential to construct a SIW beneath a foundation to protect the foundation that has already been improved by the WVW. The results proved that the application of the proposed approach could reduce the damage potential to the surface and embedded foundations located at various positions relative to reverse faults with various dip angles.

The improvement of geotechnical properties of weak soils is of interest through the resources shortage. Therefore, this study focused on the effect of silica fume as industrial waste products and nano-silica on geotechnical characteristics and micro-structural properties of kaolinite clay as a soft soil with poor strength properties. Silica fume was added to the kaolinite clay to enhance the strength with 5, 10 and 15%. Moreover stabilized soil with nano-silica were fabricated with 1, 2 and 3% by dry weight of the soil. Then, Atterberg limits, standard proctor, unconfined compressive strength, and California bearing ratio tests were conducted. In addition, the micro-structural changes of soil samples through the stabilization were examined using scanning electron microscope. The results indicated that silica fume and nano-silica increase the optimum water content and decrease the maximum dry density of the stabilized soils. Addition of 15% silica fume and 3% nano-silica to kaolinite clay improved the unconfined compressive strength at curing age of 28 days by up to 70% and 55%, respectively. Also, the results of soaked California bearing ratio test after 7 days of curing demonstrated that 15% of silica fume and 3% nano-silica increased the California bearing ratio values about two times more than the raw soil. Scanning electron microscope (SEM) images were then utilized to evaluate the effects of additives on the kaolinite clay soil. It was concluded that silica fume and nano-silica filled pore space between clay particles and a dense matrix were formed. This textural event caused an improvement in compressive strength of stabilized soils.