Strata Global

How is soil reinforcement done using geogrids?

The emergence of geosynthetic materials has brought about a noticeable change in civil engineering as they address the industry’s technical and economic challenges. Geogrids are the backbone of this industry. These materials serve not only as a protective shield but also reinforce weak soils for stability and increase load-bearing capacity.

In this blog post, we will discuss geogrid soil reinforcement, examine how geogrids can be used to strengthen the soil, as well as explain the working principle of geogrid-reinforced soils – and finally highlight some points that should be observed in the design and installation of geogrids to reinforced soils.

What is geogrid soil reinforcement?

Geogrid soil reinforcement is an innovative engineering practice to improve soil strength and stability using different types of geogrids. This revolutionary approach has transformed the construction industry by offering several benefits compared to traditional methods. A geogrid is a grid-like polymeric structure available in uniaxial and biaxial forms made from high-density polyethylene [HDPE] or polypropylene to ensure its durability and resistance against different environmental factors. When installed in layers in the bulk of soil, the geogrid becomes intertwined with soil particles, creating a composite material with significantly enhanced properties. The main purpose for using geogrid-reinforced soil is during the construction of retaining walls.

Traditional retaining walls normally require deep excavation combined with concrete or masonry, which could be expensive and time-consuming. Thus, geogrid can be used to reinforce soil out of locally available soils, leading to reduced material costs and environmental footprint. The geogrid acts as a vital reinforcement that stops the soil from caving in, thereby enabling steeper and higher walls.

Geogrid-reinforced soils are also employed in other areas apart from retaining walls, namely roads, construction, embankments, or stabilisation of slopes. The load-bearing capacity of the soil can be enhanced by using this innovative solution.

What is the interaction between soil and geogrid?

The interaction between soil and geogrid is the basis of the reinforced soil structure arrangements. Many parameters influence this multifaceted interaction and play an important role in the overall performance of the constructed system. When a geogrid is embedded in the soil, the frictional resistance between the soil particles and the geogrid’s surface prevents the reinforcement from being pulled out. Following factors influence this frictional force:

  • Granular soil is made of particles like sand and gravel, which makes it a bit rough. When the interaction between the soil particles and the geogrid is enhanced, greater friction is produced. This is why granular soils are more effective in supporting geogrids overall.
  • Clays and silts, which are sub categorised under cohesive soils, are characterised by their binding nature to one another. Consequently, the contact area of the soil and the geogrid becomes less due to the reduction of the resistance to indentation.
  • A rougher geogrid surface means that this material has a larger area to touch the soil, which in turn enhances shear resistance through extra friction.
  • The rigidity of a geogrid is the capability to withstand deformation under loads, maintaining the soil contact and enhancing the frictional resistance.
  • The size of the openings in the geogrid greatly impacts how soil particles interact with it. In the given situation, balance is the major element: if the holes are too large, the soil particles will successfully pass through them due to reduced friction; if the holes are too narrow, there will be no interaction possible.
  • This is the force applied by the soil against the geogrid. An increase in pressure leads to an increase in the shaft due to the frictional force between the soils and the geogrid. Deeper soils provide the best support to the geogrid because they weigh more and thus have more friction acting upon them.
  • A geogrid embedded deep in the ground allows it to have a larger contact area with the soil mass. This increased contact area contributes to higher frictional resistance encoding.

How does geogrid soil reinforcement work?

Geogrid soil reinforcement is a method used for decades. It uses a hard, flexible plastic mesh to make soil stronger. To simplify, the soil provides compressive strength, and the geogrid gives the structure tensile strength to produce a compound material. First, the geogrid is embedded into the soil, allowing the soil to connect with the grid’s holes. This binding process is produced by joining the two main elements and creating a unit that cannot be broken into parts.

When the geogrid is under a load, it distributes stress evenly on a larger area, making this way of preventing local failure and ensuring not only local but also general stability. This magnified stability makes it a game-changer in many fields, such as road construction. A geogrid reinforcement is one of the most notable methods used in soil treatment, and one of the advantages is that less soil is needed. The technique of mixing sand, cement, gravel, and water with polyethylene geogrids is a brilliant one to lessen the number of soil layers, materials added, and project duration.

Geogrid has a unique performance that depends on different variables such as properties of the soil. The aperture size of geogrids used in this process is a very important consideration here. Due to the design and material of the geogrids, they provide high tensile strength which is their typical behaviour. The right solution and proper installation are the two factors in each geogrid design; these are the main requirements to gain the desired reinforcement properties.

Technical drawing showing geogrid placements for soil reinforcement

What are the guidelines to consider while installing geogrid for soil reinforcement?

Geogrid soil reinforcement is a critical part of many civil engineering projects designed to enhance soil’s stabilisation and capacity.

The careful consideration of the installation process is necessary to ensure the optimal performance.

Pre- installation considerations

Design review:

The understanding of the project design is fundamental. These involve the geogrid type, dimensions, placement locations, and overlaps.

Soil properties:

Geogrids are affected by the soil’s attributes, such as its type, strength, and moisture content. These properties are the main considerations that can affect the selection and installation of the geogrid.

Site preparation:

The base of any land should be clean, even. If there is any existing vegetation or unsuitable formations, it should be removed.

Equipment and personnel:

The equipment required must be checked first for rollers, excavators, and spreading machines. Employees who are involved in the installation process need to be well informed.

Installation process

Geogrid placement

It is important to make sure that the geogrid is installed smoothly and uniformly, without any wrinkles or creases. Geogrid sheets normally have overlaps. The overlap length should stick to the design of the sheet.

Soil compaction:

The installation should be carried out in the units of layers, which are the design structures of the individual sections. Each layer of the project is required to undergo the process of being fully compacted to achieve sufficient density.

Geogrid protection:

There are times wherein a geogrid may not acquire protection through geometries and overlays from locations prone to construction damages. In circumstances such as this, geogrid protection necessitates a systemic approach that shields the aggregate surface from environmental action.

Draining:

Proper drainage is vital for uncontrolled runoff that may lead to water collection and then to a decrease in the geogrid performance.

Geogrids laid for ground soil stabilisation and improving load bearing capacity

Quality Control

Inspection of geogrid:

Perform regular checks on the geogrid to identify rips, folds, or the outright wrong alignment.

Test for soil compaction:

Carry out the resultant performance of the in-situ densitometer and density strength of the soil during a verification test.

Documentation:

Keep accurate records of the process of installation, such as the amount of materials used, the machinery used, and the names of the personnel who were a part of it.

Case study of soil reinforcement using StrataGrid™

Client: Department of Transportation, South Carolina

Location:

South Carolina, USA

Product used: StrataGridTM

Application: Construction of a steep soil slope

Construction of steep soil slope by Strata Global at South Carolina

About the project:

The South Carolina Department of Transportation (SCDOT) needed a new road next to a CSX railroad track. Strata’s engineering experts proposed the StrataSlopeTM system.

The StrataSlopeTM system suggested by Strata’s engineering specialists is the product that utilises StrataGridTM 200 geogrid for geosynthetic reinforcement and a special slope covering.

Determined to shield the slope while the concrete covering was barely maintained, a temporary erosion barrier was used. Immediately after the concrete was installed, grass was sown on the farthest part of the slope, kept with another layer of reinforcement and a protective material. By doing so, we made sure the slope remained stable and resisted floods even after construction. Strata’s solution astutely met the demand for a steep, stable slope. The design provided for both the concrete protection and the grass to grow together.

To conclude, geogrid soil reinforcement has indeed brought about a major change in the construction industry by presenting a strong and effective solution to soil reinforcement and load-bearing capacity problems. By tightly binding the soil’s compressive strength to the geogrids’ tensile strength, this method has become a leading technology in different areas, which include retaining walls, roads, and embankments and is nothing but a top-quality invention. It is the responsibility of soil-geogrid interaction to make sure that the operation will end up with the project’s completion, yet not always.

Contact Strata Global for reliable geogrid reinforcement solutions that improve soil stability and load-bearing capacity. Our expert team is ready to assist you with your construction projects, ensuring effective results and quality materials. Reach out today to discuss your project needs!

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