使用机械和化学过程和/或加强材料来增加土壤的抗剪强度。在土工和土木工程项目中，土的加固和加固的必要性要求使用新的材料和加固。近年来，虽然研究人员使用了新的化合物，但纳米颗粒还没有找到合适的位置。在本研究中，我们尝试使用不同的添加剂来增加土的抗剪强度参数。粘土矿物由于其工程特性而被认为是有问题的土壤。因此，有必要收回它们。本研究对低塑性粘土进行了研究。土体抗剪强度是任何与稳定性分析相关的重要因素，包括边坡稳定性分析。土坝和土沟边坡稳定性分析被广泛应用。在本研究中，我们尝试增加土的抗剪强度参数，即黏聚力系数(C)和内摩擦角(φ)。 Direct shear test has been used for obtaining shear strength parameters as well as Mohr-Coulomb theory has been utilized for calculating of them. Although direct shear machine has its defects and its accuracy is low in comparison with tri-axial machine, however in this study it has been selected due to its simplicity and cheapness. Since this investigation aims to compare various additives and all tests have been done at same condition by direct shear machine, its deficiencies have been neglected. Additives used in present research include: Nano-silica in various percentage, Micro-silica, cement, lime (Cao) and these materials’ combination with together. The reason to choose Nano-silica is that it is a very active super-pozzolanic additive. This additive increases strength of sample significantly through chemical actions. Using silica in soil stabilization depends on type and size of silica particles so that the more finely the more continuous gradation, so property of being finer leads to decrease pores among particles and results to increase strength while light gradation has been achieved. Silica is one of the most popular materials which play a significant role in cohesion and filling. Results of experiments have shown significant effect of these additives in increase of soil shear strength parameters. The lime leads to modify behavioral features of fine-grained soils containing clay (properties such as swelling, shear strength, water absorption ability and plasticity properties) but it should not be in vicinity of sulphate ions.Since, in this condition, presence of lime not only doesn’t play an effective role but also it results to decrease in strength as well as increase in swelling. With regard to this reason, Calcium sulfate (gypsum) was added to soils containing lime in order to study swelling of soils stabilized with lime and nano-silica. Nano-silica increases Soil shear strength parameters while it is efficient in increasing of soil swelling, too.