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Soil stabilization is the method of improving soil properties by adding suitable stabilizers to it. It is very important to achieve the required strength for the soil, especially in road construction projects where an unstable base can lead to the complete erosion of road.

There are some difficulties one may have to face while stabilizing the soil for pavement construction and the main aspects behind these difficulties are explained in this article.

Difficulties in Soil Stabilization

Three main fronts on which difficulties in soil stabilization commonly arise are :

  1. Selection of suitable stabilization technique
  2. Mix design of Soil stabilization mix
  3. Thickness of stabilized soil layer

1. Selection of Suitable Stabilization Technique

Proper stabilization method should be selected to achieve good soil properties. But the selection of a suitable technique is not an easy job to do. It depends upon various factors such as :

  • Type of soil to be stabilized
  • Availability of stabilizing materials
  • Availability of construction equipment
  • Environmental conditions of that area
  • Structure of pavement
  • Volume and distribution of traffic
  • Period of project
  • Budget of project

Each and every factor listed above should be checked and then the final choice of stabilization technique is decided.

Soil Lime Stabilization
Fig 1: Soil Stabilization using Lime

2. Mix Design of Soil Stabilization Mix

The mix design for soil stabilization should be done in such a way that it should meet the stability and durability requirements of pavement layers. To achieve these requirements some additives need to be added to the mix. But here, the difficulty arises when those additives or stabilizing materials are not available or increases the overall economy of the project.

In the other case, the method of mix design will also play an important role to attain the required strength to the soil mix. Standardized design procedure should be prepared for each stabilized mix by allotting appropriate strength values to each mix. The values may be in the form of CBR value, the compressive strength of mix etc. These strength values can also be used in the design for the thickness of the stabilized soil layer.

Soil Cement Stabilization
Fig 2: Soil Cement Stabilization

3. Thickness of Stabilized Soil Layer

The design of thickness of the stabilized soil layer is another important aspect which is often given less significance in stabilization projects. In general, the thickness of a stabilized soil layer is decided either as equal to the thickness of base-course provided or by using some modification factor for gravel equivalency. The thickness of the stabilized soil layer is kept equivalent to granular base-course considering the following factors :

  • Mix properties
  • Environmental conditions
  • Type of traffic
  • Design period of pavement

Considering stability and durability, the above-mentioned considerations will not pose any difficulties. But if the stabilized mix is weaker than the requisite value, it is not recommended to follow the above-mentioned considerations and the design for thickness should be done separately.  

However, there is no separate method to design the thickness of such poor stabilizing mixes. So, the mixes such as soil-cement, pozzolanic concrete etc. are designed as semi-rigid pavements.

Thickness of Soil Layers Under Pavement
Fig 3: Thickness of Soil Layers Under Pavement

About Sadanandam AnupojuVerified

Sadananda is a Civil Engineer and is an Author, Editor and Partner of The Constructor since 2016.