Effect of permeation grouting with nano-materials on shear strength of sandy soil: An experimental study

Nano-materials have been widely accepted for many purposes as improvement materials for several engineering projects. In this research, an attempt was made to study the effect of using two types of Nano-materials, namely: Nano-SiO2 and Nano-clay, to investigate the mechanical properties of soil improved with the aid of permeation grouting technique. Three different ratios of Nano-materials/ water (1/30, 1/50, and 1/100) were grouted at low pressure in the form of gel-like solid into soil sample, for this, a sample of sandy soil size (60x60x20) mm were treated and tested using a standard direct shear apparatus. The results indicated that the gel-like solid of Nano-materials increased the shear strength parameters due to the gel probably strong the interfacial bond between sandy soil. From the results, the angle of internal friction increased from 30.5° to 33.50° and 38.29° after 48 hrs. of curing time compared with the untreated soil and treated sand soil with Nano/water percent of 1/30 and 1/50 for Nano-Clay and Nano-SiO2, separately. ). From the results, the viscous gel of Nano-SiO2 occupies the voids between the sandy soils, contributing to the increase in the angle of internal friction of the soil. In this regard, the increase in the strength of the composite is related to the friction created between soil particles. In contrast, the same ratio will increase the cohesion from 0 to 21 kPa and 15 kPa at the same instance with Nano-materials. Although Nan-clay cause to increase interlocking of intra-particle and the angle of soil friction, this change is low, and shear strength increase in added sand soil to Nano Clay occurs as a result of cohesion enhance. The study also involved the scanning electron microscope (SEM) and X-Ray analyses as base knowledge for comparing the distribution of Nano materials and investigating the microstructural alterations. Finally, using Nano-materials will improve the mechanical properties of sand soil associated with no environmental problem and low price to similar materials in some geotechnical aspects such as an improvement of existing foundation or pile susceptibility liquefaction.