StrataDrain™: Foundation protection & soil stability
The 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. 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.
- 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, 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.
- 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 structural challenges, such as soil movement, water accumulation, and material degradation, are well known and can be planned for, the amount of maintenance required for such structures often makes cost a major consideration. While many engineers do plan for the eventual degradation of structures, there are solutions available today that help reduce overall maintenance costs while still ensuring strong and reliable 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.
- Filter layer: The geocomposite in StrataDrain acts 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: Geocomposite can act as a reinforced layer of the soil surrounding the pier, making the soil gain extra strength. Due to the use of geocomposite, 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. Geocomposite based soil improvement:
Geocomposite improve the soil properties, rendering it with more shear strength, and minimizing de-formation to support the foundation of the bridge.
Reinforcement: StrataDrain when incorporated with the soil, increases its strength. It also improves 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: Geocomposite 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: Geocomposite 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:
- 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 specifically designed to facilitate efficient drainage and reduce water buildup, helping maintain soil stability over time.
- 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 geocomposite , 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.
- Erosion control: Laying geocomposite on the riverbank strengthens the soil; it is not easily washed away by the current of the river.
- Vegetation establishment: Geocomposite 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.
- Water removal: Geonets, due to their open, planar structure, allow for the quick drainage of water. They act as a drainage layer within the soil and prevent the pooling 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, geocomposite can be used to improve the properties of the soil.
- Stabilization of shear strength: Geocomposite increase the shear strength of the soil, increasing its resistance to the forces acting on it.
- Improved load-bearing capacity: By reinforcing the soil, geocomposite 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.
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.
Case study
Client: Embalses EI Rizado
Location: Villena, Alicante, Spain
Strata Geosystems 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 geogrid. 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. Characterized 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. Take the step to ensure your project’s future is built on a solid, dependable foundation. Contact us now.