In Egypt, a huge quantity of natural and synthetic wastes are eliminated every year. Hence, the process of recycling them by mixing with soil is one of the cheapest and most effective ways to dispose those wastes and protect the environment. Also, Interest in the construction of modern road networks has become one of the first priorities in Egypt. This paper presents an experimental and numerical study about the effects of mixing rice straw (RS) and tyre chips (TC) with two types of sand on the properties of the mixtures using the experimental triaxial test. Then, study numerically the effect of earthquakes on the previous soil types. This paper discusses mainly two types of natural and synthetic wastes and two Egyptian types of sandy soils, namely Gamasa sand (S1) and Yellow sand (S5). These types of sandy soils are the most common soils used in road foundations in Egypt. This research presents innovative manner which has not been studied before with Egyptian soils. Six types of mixtures and two control specimens have been tested to determine the basic soil and shear strength characteristics for each of them. Wady El-Natroon / Al-Alameen road foundation is selected as a study case. Numerical analysis using Geostudio- Quake/w were conducted to study the effect of earthquakes on it to select the best mixture to use in it from these mixtures under the dynamic condition. Finally, the clear and strong advantage of using this wastes is the safe and economic disposal of the mentioned natural and synthetic waste materials. Also, the improved soil, which always used in road foundations under earthquake conditions will save time and money in the specific works. This study recommended using the proposed mixture of (S8) which has the best enhanced soil shear characteristics comparing with the other mixtures.