How StrataDrain™ Protects Foundations and Enhances Soil Stability

Bridges, as impressive structures as they are, can often face their toughest enemy: nature. These engineering wonders built near rivers are victims to soil erosion, scouring, water pressure, and other environmental issues that lead to foundation cracks. These cracks can lead to serious problems making the bridge unstable, disrupting traffic, and even putting people’s safety at risk. You may wonder –is this not already a known factor? How do we plan for it?

The answer lies in smart planning. New developments in soil engineering offer proven ways to lower these risks. One of these solutions, StrataDrain™, has been proven to protect bridge foundations. In this blog, we’ll take a close look at foundation cracks, and find how StrataDrain™ can make soil more stable and structures stronger.

Common causes of foundation cracks

Erosion of the soil: As river flow crashes along the shore it impacts the soil surrounding the foundation of the bridge. This wipes away the soil, gradually causing erosion. As the soil is eroded, the strength of the foundation weakens, and thus, the building undergoes settlement. The earth and the man-made part can settle at different rates, which as a result can cause the bridge to develop cracks in it.
Scouring: The water around the bridge piers excavates the soil, leading to scoured holes. The development of these holes causes a void in the foundation causing it to lose its grip on the soil. This ultimately leads to an unstable bridge foundation. StrataDrainTM helps alleviate this pressure by providing drainage pathways.
Hydrostatic pressure: The hydrostatic pressure in construction–refers to pressure exerted by water against a structure or material due to its weight and density–is one of the most undermined risks to the bridge’s foundation. Underground water causes hydrostatic pressure affecting bridge foundations. This force, as well as other causes such as soil being washed away and water scouring, can cause cracks to form in the foundation.
Soil liquefaction: Water-laden soil during seismic activity can act like a liquid in quake-prone regions. This phenomenon is called liquefaction which often occurs in saturated, loose sandy soils during seismic activity. The liquefaction of the soil causes the foundation to lose its grip and the load-bearing capacity, which in turn causes instability and possibly results in crack formation.
Thermal movements: Bridges, as well as other structures, undergo heat-induced deformation that makes them expand or contract depending on the temperature variations. With the ever changing effects of global climate change, today, structures are more vulnerable than ever. Most construction materials –especially concrete–absorb a lot of heat. Thus, the foundation also undergoes pressure as a result of this movement. The disruption of expansion and contraction is an additional factor here. The result of this is the formation of deep cracks.
Differential settlement: The two sides of the river bank are comprised of different soil properties and compositions. Differential settlement is often due to variations in load distribution, soil type, and moisture content. This distinction is the cause of the foundation being not perfectly positioned, as one side of the bridge is sinking at a different pace than the other side. This non-conformance of settlement is also one of the reasons for stress on bridge structure, leading to fissures.
Pier and abutment loading: Bridge weight, mainly supported by the piers and abutments, transmits pressure to the soil beneath. As time goes on, the earth becomes subjected to such pressure and starts to compress, which results in differential settlement, hence, the foundation cracks.

What are the mitigation techniques?

While many of these scenarios are known, and can be planned for, given the amount of maintenance needed for such structures, cost is often a consideration. While of course many engineers plan for the eventual degradation of structures, there are solutions today that reduce the overall maintenance cost while building strong structures.

1. Scour protection with geotextiles:

Scour, which is soil erosion around bridge piers, is one of the major factors threatening the stability of a bridge. Geotextiles are synthetic, permeable fabrics that will help diffuse this type of risk.

Reinforcement using StrataGlobal StrataTex HSR™ geotextiles

Filter layer: Geotextiles in StrataDrain act just like a filter layer around the piers. They provide the passage to water and hold the particles of soil together. In this regard, the flow of water does not wash away the soil; the geotextile saves the soil from being washed away, thereby protecting the foundation from scour.
Reinforcement: Geotextiles can act as a reinforced layer of the soil surrounding the pier, making the soil gain extra strength. Due to the use of geotextiles, it can resist the erosive force that the water holds.
Bioengineering: Sometimes, a composite of geotextiles with vegetation could be used to create a living armouring of the pier. Apart from the provision of additional bank stability, vegetation roots will further improve the reinforcement of soil.

2. Geotextile based soil improvement:

Geotextiles improve the soil properties, rendering it with more shear strength, and minimizing de-formation to support the foundation of the bridge.

StrataGlobal StrataDrain™ drainage composite to improve drainage.

Reinforcement: StrataDrain™ when incorporated with the soil, increases its strength. It also enhances the shear strength and load-bearing capacity of the soil, due to which it can resist the stress produced by the load of the bridge.
Drainage: Geotextiles like StrataDrain™ are good drainage materials. When they are installed in the soil, they act as a drainage path through which water can be evacuated; hence it reduces the hydrostatic pressure and prevents liquefaction.
Separation: Geotextiles will aid in separating dissimilar soils. This will prevent the blending of soils of differing properties, which may result in the reduction of load-bearing strength and deformation characteristics of the embankment and foundation system.

3. Deep foundations and geotextiles:

Geotextiles work wonders in enhancing the performance of deep foundations such as drilled piers and piles.

StrataTex HSR™ geotextiles used in foundation element for stability

Filter layer: The geotextiles can encase the foundation element like a filter layer. This prevents the penetration of soil materials into the concrete, thereby enhancing its strength and capacity.
Protection: The foundation element can be protected from damages during its installation and even from the external forces that occur after the construction.

4. Monitoring and maintenance with geonets

The geonets in StrataDrain™ are three-dimensional geosynthetic structures which are specifically designed to monitor soil movement and pave the way for maintenance.

Detection layer: Geonets can be laid in between the soils to create a detection layer. Any movement of the soil will result in the deforming of the geonet, which can be measured using different types of measurement methods.
Drainage: Like geotextiles, geonets also show excellent characteristics of drainage. They create a drainage path to avoid any water retention and potential damage caused by it. Thus reducing the hydrostatic pressure.
Accessibility: The open structure of geonets offers a high degree of accessibility to the underlying soil for investigation or repair work.

What are the other applications of geocomposites?

1. Riverbank stabilization

The riverbanks are continuously subjected to the eroding forces caused by water currents. This causes the bridge foundation to be undermined by the embankment that was eroded. StrataDrain™ plays an important role in riverbank stabilization.

Erosion control: Laying geotextiles on the riverbank strengthens the soil; it is not easily washed away by the current of the river.
Vegetation establishment: Geotextiles provide a very good medium in which vegetation can develop. The plant roots bind the soil and increase the soil stability near the bank.
Protection of bridge foundations: A stabilized riverbank will minimize the potential for scour at bridge piers and protect the foundation of the bridge.

2. Drainage systems

An effective drainage system is vital to prevent water accumulation that can lead to hydrostatic pressure and instability of the foundation. StrataDrain™ is an excellent material for developing drainage systems.

Water removal: Geonets, due to their open three-dimensional structure, easily allow for the quick drainage of water. They perform the function of a drainage layer within the soil and avoid the pooling of water.
Hydrostatic pressure reduction: With the effective removal of water, geonets significantly reduce the hydrostatic pressure on the bridge foundation which minimizes the risk of uplift and cracking.
Filter layer: The geonets may also act as a filter layer that avoids the clogging of soil particles within the drainage system.

3. Soil reinforcement

A weak or unstable soil will weaken the performance of a bridge foundation. In such scenarios, geotextiles can be used to enhance the properties of the soil.

Stabilization of shear strength: Geotextiles increase the shear strength of the soil, increasing its resistance to the forces acting on it.
Improved load-bearing capacity: By reinforcing the soil, geotextiles improve its ability to support loads applied by the bridge.
Reduced settlement: A reinforced soil foundation has less settlement, hence minimizing differential settlement and thereby cracks.

Cracks in the foundation can destroy even the oldest and the strongest structures. Bridges and connecting roads are most prone to cracked foundations due to their constant contact with water. Engineers can achieve a great deal of performance and durability in bridge construction by incorporating geocomposites like StrataDrain™ into every possible link, beginning from foundation protection to improvement in soil conditions and riverbank stabilization. Geotextiles and geonets are the most versatile and efficient materials. It is only through the proper blending of these innovative materials with sound engineering practices that bridges can be built, combining the advantages of visual appeal with resistance to all sorts of natural forces.

Case study

Client: Embalses EI Rizado

Location: Villena, Alicante, Spain

Strata Global demonstrated its expertise in innovative solutions for environmental integration with the Surface Sealing and Post-Closure maintenance project at Villena’s MSW treatment plant Landfill. The project involved design and delivery for both rainwater drainage systems and gas collection. Effectively closing the landfill while meeting the environmental consideration was the requirement of the client. An important challenge we faced during this project was the need to design anchor trenches within a confined space. Hence, we provided them with the best solution with our StrataDrain™ drainage composite and StrataGrid™geogrids. In contrast to the traditional approaches including gravel and common geotextiles, Strata’s solution offered high flow rate, enhanced design efficiency and a higher security factor. Characterised with high flow and low creep, StrataDrain™ are designed to withstand high compressive forces. Drainage composites provide a pathway for gas migration, preventing it from escaping the surface. By preventing the infiltration of the particles in drainage, it averts the clogging of the system.

Your projects deserve to stand strong for years to come. StrataDrainTM helps protect the very foundation of your structures, guarding them against the relentless forces of nature. By choosing StrataDrainTM, you’re investing in long-term stability and peace of mind, knowing that your bridges, roads, and buildings will remain safe and secure. Take the step to ensure your project’s future is built on a solid, dependable foundation. Contact us now!

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How StrataDrain™ Protects Foundations and Enhances Soil Stability

Common causes of foundation cracks