Before starting a construction project, it’s important to evaluate the liquefaction of soil to ensure ground stability and overall safety. This process helps with design and planning, ensures compliance with industry regulations, and mitigates risks early on. This assessment can also save you from expensive repairs and retrofitting after construction.
Consult with a geotechnical company that specializes in soil liquefaction evaluation to guarantee the safety and stability of your construction site.
What is Alluvial Soil?
Alluvial soils come from materials deposited by rivers, streams, and similar water systems. They’re mainly composed of alluvium, a mix of clay, silt, gravel, sand, and various sediments that running water carries. Over time, these sediments steadily accumulate on riverbeds, creating this type of soil.
Primary characteristics of alluvial soils include:
- Highly fertile. Alluvial soils are rich in nutrients that crops need to grow, making them suitable for agriculture.
- Layered structure. Alluvial soils are composed of multiple layers of materials deposited over time. Each layer contains different combinations of silt, sand, clay, gravel, and other materials.
- Loose and unstable. Alluvial soil particles are less densely packed than other soil types. This results in a looser and less stable soil structure, making it less suitable for construction.
- Prone to liquefaction. Because alluvial soils are made of loose, coarse material deposited by running water, they have a high water content.
The Los Angeles Basin is one of California’s most well-known regions with alluvial soil. It includes the LA coastal plain, the San Fernando Valley, and the Los Angeles River floodplains.
Factors Affecting the Liquefaction of Soil
Four primary factors influence the likelihood of liquefaction of soil during and after a seismic event: the type and composition of soil, the soil’s density and compaction, the water saturation level, and the intensity and duration of seismic activity.
- Soil type and composition. Soils with large quantities of loose or unconsolidated granular particles like fine sand or silt are more likely to liquefy than densely packed sand, clay, or gravel. Alluvial soils, commonly found in the Los Angeles area, are among the soil types most prone to liquefaction.
- Soil density and compaction. The more loosely packed the soil, the more susceptible it is to liquefaction. Alluvial soils are less densely packed than others, meaning they may liquefy more during a seismic event.
- Water saturation level. The higher the water content in the soil, the more likely they are to liquefy under seismic activity. Alluvial soils typically have a high water content, increasing the risk of liquefaction.
- Intensity of seismic activity. Longer and more intense seismic shifts, such as earthquakes, may induce a stronger liquefaction effect, regardless of soil type. Historic seismic activity can also affect the risk of liquefaction. For example, soils repeatedly affected by earthquakes may have settled and compacted over time or remained loose and unstable.
What Does a Soil Liquefaction Evaluation Process Involve?
AES Soil can conduct a soil liquefaction evaluation to check if your site is suitable for construction. Our assessment includes the following steps:
- Investigation and testing. We begin the evaluation process by researching historical information about an area’s geological data. We will then visit the site, conduct field testing, and take local soil samples.
- Soil analysis. We will process the soil samples by conducting laboratory testing. Our tests will analyze the soil’s composition, measure its water content, and calculate its density. We’ll also evaluate the soil’s plasticity, permeability, shear strength, and response to compression to determine whether the soil can be packed and prepared for a construction project.
- Seismic assessment. Our team will evaluate the potential seismic risks on-site, from consulting local seismic history readings to finding the closest faults and sources of seismic activity. We’ll use the information to determine the potential risks and magnitude if an earthquake occurs, including possible soil liquefaction rates.
- Risk mitigation strategies. After gathering all relevant information, we will propose strategies to mitigate the risks of soil liquefaction. Common geotechnical engineering solutions include soil improvement techniques like compaction or water drainage. We will also consider seismic-resistant building techniques and additions, such as deep foundations, flexible building materials, or seismic friction dampers.
- Post-process reporting. AES Soil will compile a complete report of the data and analyses conducted, providing a comprehensive outline of your site’s geological and seismic characteristics. We’ll also offer our interpretation of the data and provide guidance and recommendations to manage all identified risks and ensure the safety of your construction project.
Get Help From Qualified Geotech Engineers in the Los Angeles Area
Based in Glendale, California, Applied Earth Sciences (AES) has provided its geotechnical engineering services to Southern California for over 30 years. Our decades of expertise have allowed us to build an extensive library of soils, geology maps, and seismic information in the greater Los Angeles area.