Posts Tagged ‘Landslides’

Causes for Building Damage

There are a host of potential causes of building damage, however, they can be broken up into three primary categories. Those primary causes are from: environmental conditions, material/structural defects, and ground movements.

The environmental causes can be broken into mainly two subcategories: climatic and seismic (earthquakes). Climatic conditions which can cause damage to the structure are primarily in the form of temperature, wind, and precipitation. More typical examples of building damage from climatic conditions consist of temperature straining, material freeze and thaw, wind damage, and catastrophic weather (e.g. hurricanes, tornadoes, flooding).

Environmental

The second category of material or structural defects consists of flawed constructed materials or elements which result in unintended damage. The two main subcategories of this cause of damage involve improper design and defective installation. Examples of damage from improper design could involve underestimating building loads, missed load or deformation concentrations, inappropriate building elements, poor run-off drainage, and selection of improper materials such as wrong concrete type. Defective construction could involve, for example, poor honeycomb or weak concrete, missing or faulty welds, missing reinforcing steel bars, curing cracks due to improperly poured concrete, etc.

Material Defects

(Photo Credit: Gopal Mishra)

https://theconstructor.org/practical-guide/honeycombs-in-concrete-and-remedies/6889/

(Photo Credit: Caitlin McCabe)

https://www.inquirer.com/news/water-damage-new-home-construction-regulation-bill-pennsylvania-suburbs-philadelphia-20190329.html

The other primary cause is related to ground movements. The different subcategories of ground movement which most typically result in building damage include: soil settlement, soil/rock heave, landsliding, land subsidence, and earthquake shaking and associated ground failure. Land subsidence damage mainly involves sinkholes and surface depressions in karst terrain, from underground mining, and settlement from soil collapse from water saturation. Although earthquake shaking alone can result in building damage, foundation failure can also result from ground failure in the form of settlement, soil liquefaction, and landsliding (including lateral spreading). Please refer to the following blogs for additional explanation: “Causes for Building Settlement”, “Landsliding: What to Do”, “What is Karst Subsidence”, “What is Mine Subsidence”, and “Causes for Building Uplift”.

Ground Movements

If confronted with building damage, it is important to contact the appropriate experienced forensic engineer. In most cases, a qualified structural engineer would be the most appropriate initial investigator to assess the nature of the damage and provide the proper direction to determine the cause.

If MEA can assist you with your building damage problems, please contact us at 314-833-3189

Landsliding: What To Do

When a site is experiencing landsliding, it is a good idea to have some basic understanding of what might have caused this ground movement in the first place. Landsliding in soil occurs when the slope is weakened or loaded. Weakening typically occurs when the soils weaken over time (i.e. weathering), and the slope’s vegetative root structure, which was anchoring the soil, is removed. Undercutting the slope either naturally (e.g. stream erosion) or by man weakened or reduced the slope’s resistance to sliding. Loading the slope can occur when temporary or permanent loads are added to or placed on the slope (such as storage containers or stock piles of materials at the top of the slope), or when the soil slope gets soaked by excessive precipitation or when previously submerged slope is now exposed. Based on the above, it stands to reason that stripping and steepening the slope during land development causes the greatest damage to the slope and should be carefully evaluated.

Given the various phenomena which can exist as discussed above, the rate of sliding can vary significantly from a slow creep to a rapid failure. When dealing with an abrupt/quick sliding event some actions that can be taken are the following:

  • Block off area to reduce hazard
  • Can easily progress upward (rarely expands sideways without some causation component) – consider this as part of the hazard area.
  • Cover/seal ground cracks from precipitation runoff

With slowly developing slope events, there will be signs of instability. These could include:

  • Settlement at the top of the slope resulting in downslope tilting and separations in adjacent structures and flatwork.
  • Cracking in the slope especially if roughly along the slope (e.g. not random network of cracking)
  • Fence posts, poles, etc. titled downslope, trees leaning down slope, or if very slow trees curving upwards to compensate for very slow slope movement.

The above is illustrated in Figure 1.

It is important to note that any point in time a slow-moving event can turn abrupt.

Of course, there are other phenomena and technical issues involved when there is a sliding event than is given above. To properly assess and understand the sliding conditions and any hazards and to know how to properly remediate the event, a geotechnical investigation should be performed. For information on how to select the appropriate geotechnical engineering companies see: What to look for When Selecting a Geotechnical Engineering Company. It is important to note that is not advertised that contractor be hired to provide the fix without adequate engineering.