Sometimes the forces of nature — earthquakes, hurricanes, or even something as common as heavy rains — produce slope failures that cannot be predicted, much less prevented. But many slopes produce warning signs that the earth is about to move, with costly consequences.
Conducting a slope-stability analysis in response to these warnings can forestall litigation, keep traffic flowing on busy highways, and perhaps even save lives. Statistics from the U.S. government say landslides cost an average of $3.5 billion a year and cause 25-50 fatalities. Detecting clues to an impending landslide can be the first step toward preventing these kinds of tragedies.
5 common symptoms of slope instability
Many slopes are just one powerful rainstorm away from collapsing, which makes these common slope failure symptoms too important to ignore:
- Visible cracks. If a roadway or bridge surface has cracks large enough to be seen with the naked eye, there’s a strong possibility that the underlying structure has shifted.
- Leaning or curved trees, guardrails, and other structures. Trees normally grow vertically toward the sun, and light poles and guardrails normally appear level. If they are starting to lean, you could have a slope issue.
- Toe erosion. If you see signs of erosion at the natural bottom of a slope — fallen dirt, debris, rocks, and such — the slope could already be starting to give way.
- Hummocky slope surface. Hummocks are small mounds, so a hummocky surface of a slope means it has humps or bumps that aren’t natural features and may be telling you the underlying ground is moving.
- Moisture changes. Water is the chief culprit in most landslides, loosening soil structures and causing the combination of gravity and shear forces to trigger a slide. If water starts showing up in new places, or if places that used to be wet or hold standing water are suddenly dry, there’s a strong possibility that the local geology has shifted.
Many more symptoms will show up in a comprehensive slope stability analysis conducted by experienced geotechnical engineers who have studied these risks in depth.
What happens in a slope stability analysis
CTL has four decades of experience conducting slope-stability analyses from coast to coast. Here’s how we assess a slope:
- Visual evaluation. Our experts walk the site, examining the obvious evidence and scanning for more subtle clues that others miss. This helps determine the scope of the investigation so the client will know what to expect.
- Research. A study of the geology and history of the site includes a literature search to find out what previous assessments have found.
- Slope investigation. Soil testing characterizes the subsurface conditions and generates data that can be used to model the slope and determine the most probable reasons for failure.
- Repair recommendation. CTL engineers recommend a repair if it’s necessary (and possible). The repair will be designed in consultation with the client.
CTL engineers also can provide expert testimony on the analysis if litigation results from a slide.
Experience makes all the difference
CTL conducts about 50 slope stability analyses every year in sites throughout the continental U.S. We’re familiar with the peculiarities of soils in different regions of the country, and we’ve worked with municipalities and highway agencies dealing with a diverse range of slope challenges.
This unique combination of experience and skills have made us a top choice for slope-stability analysis in all phases of construction projects: Scouting sites before work starts, studying damaged sites, recommending optimum repairs, and testifying in court if the need arises.