The main idea of improving soil engineering properties is not a new one. Some of the rules and principles of soil improvement, such as compaction, sealing, and the use of additives, have been used for thousands of years. The use of wood, straw, and a mixture of straw and mud to improve and improve the condition of the soil in ancient times in Mesopotamia and ancient Egypt in pre-Christian times has been reported. The most common solution is to use a system such as deep piles with the aim of passing through problematic and undesirable soil layers and achieving suitable and desirable materials. However, this option can be expensive and time-consuming, and in practice, it can be difficult to reach the desired depth at great depths. Also, in some geotechnical projects, such as tunneling, it may not be possible to run a pile. For these reasons, when faced with adverse soil and problematic grounds, soil improvement is done with the aim of creating favorable soil engineering conditions using a cost-effective and environmentally friendly method. Common goals of improvement methods can be one or more of the following:

-increasing shear strength or soil density to improve the bearing capacity and/or to provide sufficient support in excavation or tunneling

-reducing compressibility to minimize uniform settlements or structural differences

-reducing permeability to minimize groundwater flow or sealing

-drainage in-depth as an auxiliary solution along with preloading and filling with soil

-preventing liquefaction or reducing lateral expansion under or near structures during an earthquake.

Effective factors choosing appropriate improvement technique

When dealing with a geotechnical problem and in order to achieve the best results for improvement, a number of variables should be considered to select the method or methods of improvement. The physical characteristics and soil conditions of the project site or construction site, as well as economic and social factors, are very important in determining a proposed design for selecting one or more improvement methods. These factors include soil type, area, depth and location of the site, desired characteristics and required specifications of the soil, material availability, level of equipment and experiences, environmental issues, and economic issues.

Overall, soil improvement techniques can be divided into four categories as follows:

- mechanical improvements

- hydrological improvements

- physical and chemical improvements

- improvement using soil reinforcing techniques