Nanotechnology is extensively used in engineering to improve systems, characteristics and standards. Various techniques can be used for soil improvement in road embankment and geotechnical engineering. The present study examined the effect of nano calcium carbonate (nano-CaCO₃) on clayey sand soil using uniaxial and consolidation tests on specimens containing 10%, 20% and 30% kaolinite and bentonite, and 0.3%, 0.7%, 1.1% and 1.5% nano-CaCO₃ at curing times of 7, 14 and 28 days. The results showed that mixtures containing 10% and 20% clay plus 0.7% nano-CaCO₃, and specimens with 30% clay and 1.1% nano-CaCO₃, exhibited optimal UCS and consolidation properties. XRD patterns indicated an increase in the intensity of the phases (calcium silicate hydrate, kaolin, calcite, etc) after the addition of nano-CaCO₃ to the soil. SEM micrographs showed better filling of voids after the addition of nano-CaCO₃ to both clay types. The amounts of these products were higher in the bentonite specimens .

The effect of nano-CaCO₃ on the geotechnical properties of clayey sand (SC) soil was investigated. SC soil containing 10%, 20% and 30% clay and 0.3%, 0.7%, 1.1% and 1.5% nano-CaCO₃ were cured for 7, 14 and 28 days and then subjected to uniaxial compression testing. The experimental results were analyzed numerically by the group method of data handling using an artificial neural network. Crystalline phases were analyzed by x-ray diffraction (XRD) to study the microstructure of soil specimens improved with nano-CaCO₃. The addition of nano-CaCO₃ to SC specimens, especially those with lower clay contents, increased their uniaxial compressive strength and the compressive strength increased over time. An optimum nano-CaCO₃ level of 0.7% was determined for soil containing 10% and 20% clay and 1.1% for soil containing 30% clay. The results indicated a decrease in deformation and increase in stiffness of the soil with the addition of nano-CaCO₃. The effect of nano-CaCO₃ on the ultimate compressive strength of the soil in the XRD patterns indicated an increase in the recrystallization of the particles. Numerical analysis of the experimental results found a correlation for predicting the uniaxial compressive strength of the improved SC soil with a mean error of 4%.

A new installation method for micropile is introduced, called driven grouted micropiles (DGMs), in which closed-end perforated steel pipes are driven to the refusal depth using a light hammer and grout is injected incrementally into the pipe using pneumatic packers. The increased bearing capacity and ease of construction of these micropiles recommend them over conventional micropiles. A total of 102 full-scale static loading tests were analyzed to evaluate the geotechnical performance of the DGMs in both sandy and clayey soil. The load–deformation curves were analyzed, and the ultimate bearing capacity of the DGMs was extracted using micropile failure criteria. The results show that, although existing micropile design manuals do not recommend consideration of the tip resistance of micropiles, the proposed DGM method recommends consideration of end bearing. The contribution of end bearing to the bearing capacity of the DGM is approximately 30%. In order to design a DGM that meets FHWA formulas for conventional micropiles, an incremental coefficient (λ = 1.3) is proposed to apply to the theoretical micropile diameter. Another incremental coefficient (η = 1.25) is proposed to apply to FHWA recommendations for bond strength that relate to the soil type.