One of the main problems in the construction of structures is foundation strengthening strategies and soil improvement under the foundation. By increasing the population and the observation of damage caused by earthquakes and other natural factors, and the human need to create strong and durable structures and strengthen and improve old structures has expanded more and more. For example, embankments on soft soils (sensitive clays), river retaining walls built on very loose sand, or marine structures built on loose sediments located on continental faults. Lack of knowledge of liquefied or sensitive soils may threaten the integrity of the structures located on them.

One of the most important issues in this field is soil improvement, which is the controlled reconstruction of soil in situ for reuse in a new geotechnical structure or improvement of the current structure. In this section, an overview of new land improvement methods and their applications will be given. The ultimate goal of all of them, is to improve soil geotechnical parameters, reduce costs, shorten the implementation time and increase the life of service. They are done to change soil properties and ultimately reduce structure subsidence, improve the shear strength of the soil, eliminate a lot of empty space in the texture of soil materials and thus increase its bearing capacity, the reliability against slip of embankments slop and earth dams, reduce compaction characteristics and soil swelling.

The most practical methods of soil improvement are the following:


Micropile is one of the common methods of soil improvement. Micropile is added as a load-bearing element and while adding soil strength, it modifies the mechanical properties of the soil by injecting cement slurry. Micropiles are piles with a diameter of less than 30 cm that after drilling a bore or instaling the casing, steel reinforcement is placed in it and injected in situ and has advantages such as preventing soil subsidence, increasing bearing capacity and soil hardness, creating compaction, high speed execution of work, and low costs.

Injection of cement into the soil is another way to increase soil bearing capacity and prevent water leakage in the structure. Injection by filling the pores of the soil, in addition to the above, is also used to stabilize the slopes and prevent swelling. Soil injection is performed in different types such as compression grouting, permeation, jet, and hydraulic failure.

Piling in the soil

Soil improvement by injection method

Dynamic compaction

One of the methods of deep soil compaction is dynamic soil compaction. The benefits of compaction include increased soil load, reduced unwanted subsidence, and slope stability. During the foundation reinforcement process, by falling a hammer from a height of 20 meters, we reach a speed of 720 kilometers per hour, which occurs in the strongest earthquakes.