While geosynthetics do offer a lot of benefits for large grading and earth moving projects, they’re not always required by every design. Knowing when to not use geosynthetics can reduce the costs of some projects so that extra funding is freed up for soil conditions that require reinforcement. In fact, adding a geomembrane or geogrid where it’s not needed could weaken the soil rather than strengthening it. Only an engineer can determine exactly when and where geosynthetics are needed, but there are some common warning signs a project will likely need at least one of these materials.
Erosion
Existing or potential erosion issues are generally a clear sign some kind of stabilization and separation will be needed. Geosynthetics are generally the best option for erosion control besides vegetation. Many steep slopes are simply not good candidates for vegetation since even deeply and widely rooted grasses can fail when there’s too much water rushing over a steep surface. Geogrids and nets go a long way in keep soil from moving and preventing the formation of ruts and undercuts that can weaken a large mass of soil. Proper erosion control is essential to protect waterways and to prevent landslides that cause property damage or wipe out your planned construction entirely.
Wet Soil
Wet soil that holds a lot of rainwater, or has a high underground water table, also needs stabilization. Building on top of wet soil creates a compression situation that squeezes moisture out, causing uneven settling that can crack even the most reinforced foundations. Roads built over wet soils develop ruts and dips that quickly turn into potholes and require constant filling as they reform. By covering a layer of wet or unstable soil with a sturdy geomembrane, the separate effect stabilizes the ground. Upper layers of gravel and soil stay dry and drain better after a heavy rainfall event. Only soil testing can reveal if the current average level is high enough to require the use of a geosynthetic.
Sensitive Groundwater
While there was once plenty of space for building wastewater treatment plants and manufacturing facilities far from anyone’s home, these new systems no tend to squeeze in on developed areas. Building close to homes and businesses, that rely on well water from underground supplies, requires more care than construction completed far from other structures. If you’re going to be handling or storing dangerous chemicals and hazardous materials, you’ll definitely want geomembranes under the soil to prevent contamination issues. Even small amounts of many common chemicals reaching groundwater supplies can lead to long-term or permanent damage to nearby wells. To avoid the expensive fines that comes with this kind of event, start the project out right with containment products from BTL Liners.
Soil Characteristics
Heavy clay soils tend to cling together better, while light and sandy soils are very prone to movement when pushed by water or wind. The exact composition and characteristics of the soil you’re working with play the largest role in determining whether geomembranes and other geosynthetics are needed or not. A high level of grit or gravel could mean that the soil is prone to delamination in sheets, or it could mean that the soil is holding together well. Proper soil testing allows you to use accurate engineering charts to determine the proper slope and grade for each angle of groundwork. If your charts show the soil can’t possibly hold at the angle and slope you need, geosynthetics help you bridge the gap in its natural characteristics.
Steep Grades
The steeper the slope, the more likely it will need some kind of geosynthetic stabilization. For many areas with average soils, natural slope repose tops out at around 30 degrees. This isn’t a very steep surface at all, requiring dozens to hundreds of feet to cover a large rise in height. For 45-degree angle slopes and sharper, you’ll definitely need geocells and nets to keep the surface soil from moving as water runs over it. You may also need multiple layers of buried geosynthetics to separate and tie the layers together, so they don’t get carried away by water. Nearly vertical slopes require retaining walls for reliable support, and geosynthetics are still required to reinforce and protect these structures as well.
Soil Movement Risk
On top of the likelihood of the soil moving due to its slope or characteristics, consider the amount of risk posed by the movement of any soil in the project. Some slopes may pose little to no risk if they collapse, while others are situated over a home, business, or roadway. Even a landslide or soil collapse that doesn’t ruin a building will generate thousands of dollars in clean-up costs and upset your neighboring property owners. Landslides that block roadways can generate fees from the local municipality and state. Weigh the risks of losing soil to erosion or a sudden slide before determining if you can go without geosynthetics in a specific area first.
Still not sure if your project is likely to need geosynthetics or not? Try checking out case studies and research papers about related works. If you notice that the majority of roadways or construction projects similar to yours are making good use of these materials, you’ll likely need them as well. We can also help with advice and answers here at BTL Liners.
