Ground Improvement Techniques: Types and Characteristics

Ground Improvement Techniques

Hello, this is Kkoogongnam.

Today, I will discuss the types and characteristics of Ground Improvement Techniques.

When constructing high-rise buildings or factories, significant load-bearing capacity is required. If the soil is weak, various techniques are employed to improve it. Let’s outline these techniques as follows.

0. What is Weak Ground?

Weak ground is characterized by soil with low shear strength and high compressibility, making it incapable of supporting superstructures in its natural state.

Problems such as settlement, permeability, and liquefaction prevent the installation of structures on this type of ground.

1. Grouting

Grouting involves injecting a grout mixture (often a cement-based slurry) into the tiny voids within the soil to enhance the ground’s strength and reduce its permeability.

By physically binding soil particles and filling voids, grouting improves soil strength and controls settlement.

The strength and properties of the grout are crucial for determining the load-bearing capacity after ground improvement.

1-1 Types of Grouting

Cement Grouting: Commonly used for filling large voids.

Chemical Grouting: Utilizes chemical solutions to bond particles in fine soils.

Compaction Grouting: Injects a thick grout to displace and compact surrounding soil.

2. Soil Stabilization

Soil stabilization techniques aim to enhance the strength and durability of the soil. This can involve various methods:

2-1. Chemical Stabilization

Chemical Additives : Adding lime, cement, or other chemicals to soil to strengthen particle bonds and improve soil strength.

2-2. Physical Stabilization

Geosynthetic Reinforcement : Utilizing synthetic materials to stabilize the ground. Depending on the type, geosynthetics can be used for drainage or to reinforce load-bearing capacity, distributing stress and controlling settlement.

Pile Methods : The most well-known ground improvement method involves inserting piles (pipes or columns) into the ground to increase load-bearing capacity. Numerous piling techniques exist, but the core concept is to provide structural support through embedded piles.

<Types of Piles>

  • Driven Piles : Pounded into the ground using a pile driver.
  • Bored Piles : Installed by drilling and filling with concrete or other materials.
  • Micropiles : Small diameter piles used in constrained spaces.

3. Compaction

Compaction increases the soil density and strength by reducing the void spaces between soil particles using mechanical energy. Various techniques are used to achieve this:

Dynamic Compaction : Dropping heavy weights to compact soil.

Vibrocompaction : Using vibratory methods to densify sandy soils.

Roller Compaction : Applying smooth or rubber-tired rollers to compact soil layers.

The degree of soil compaction is evaluated using the dry unit weight. When water is added during compaction, the lubricating action of the water allows soil particles to rearrange more densely.

For an explanation of dry unit weight, please refer to the following post.

<Soil Characteristics and Properties(Engineering)>

4. Drainage

In cases where the ground contains a significant amount of water, **drainage methods** are employed to preemptively remove water to avoid changes in effective stress and volume.

4-1. Methods for Clayey Soils

Sand Drain : Installing sand-filled columns to enhance drainage.

Paper Drain : Utilizing prefabricated vertical drains to accelerate water removal.

Preloading : Applying an external load to consolidate soil and expel water.

4-2. Methods for Sandy Soils

Well Point System : Using shallow wells connected to a vacuum pump to lower groundwater levels.

Deep Well System : Employing deeper wells and submersible pumps for larger volumes of water.

5. Summary and Additional Method: Separation by Soil Type

5-0. Common


5-1. Clayey Soil Improvement

Drainage : Using sand drains, paper drains, or preloading to facilitate drainage and consolidation.

Replacement : Methods like excavation replacement to remove and replace weak soil with stronger material.

5-2. Sandy Soil Improvement

Drainage : Employing Well Point or Deep Well methods to physically remove water.

Compaction : Techniques such as Vibroflotation and electric shock methods to compact soil.

Injection Methods : Applying grout or other stabilizing solutions to bind and strengthen the soil.

This concludes the explanation of ground improvement methods.

Thank you!

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