Geotechnical Engineering 101 and more…

Building firm foundations

Landslides – Causes

Posted by Kshitija Nadgouda on May 30, 2006

A landslide is defined as the rapid movement of landmass over a slope. When a natural slope or man-made slope becomes unstable, a landslide results. The main causes of landslides are:

  1. gravity
  2. groundwater table changes
  3. earthquakes or other vibrations
  4. construction on top of slope, etc.

Vancouver slide
(Courtesy Huge Landslide)

The resistance to a landslide is offered by the type of soil and the geometry of the slope. Preventive and remedial measures include modifying the geometry of the slope, controlling the groundwater, constructing tie backs, spreading rock nets, etc.

Although landslides may not be preventable, their devastating effect on humans and their property is avoidable and can be mitigated.

For this post, let us discuss landslide causes in detail.
The basic cause of a slope failure is when the driving forces (forces causing the downward movement) exceed the resisting forces. When heavy rains occur, the rain water infiltrates into the soil and groundwater table is raised. The pressure exerted by the water thus increases, causing the driving force to exceed the resisting force, hence resulting in a landslide. In an extreme case, the soil may become so saturated with water, that it behaves as a fluid and flows downwards. This is called a mudslide.

Mudslide
(Courtesy Daily Bruin)

Earthquakes cause vibrations and ground shaking, which induce landslides. Other man-made vibrations such as movement of traffic, opertions of heavy machinery, pile driving and other construction-related vibrations may also cause landslides. Particularly, if these man-made vibrations occur on top of the slope, a landslide could be triggered.

Kobe slide
(Courtesy Landslide at Kobe)

Technorati tags: ,
, , , , ,

Copyright Kshitija Nadgouda.

Advertisements

5 Responses to “Landslides – Causes”

  1. […] In my earlier post, we discussed the causes of landslides. So logically the preventive measures can be deduced directly from the causes. […]

  2. Shlomo Ben Josef said

    I am a air-photo-interpreter conducting research of earthquake damages as seen from ground, air and satelite images. I would like to know if you can give me permission to use images from your report on One Response to “Landslides – Causes” in either
    of the following ways:
    1) Show the images to classes of emergency and aid organizations (fire squads, police, paramedicals) to teach the quick response techniques and coordinate the recovery efforts.
    2) Including your images in instruction manual which will not be available to the public but only for inner and selfuse of the above mentioned emergence forces.
    Of course I will include proper credit, as you specify.

    Yours sincerely,

    Shlomo Ben Josef

    Kfar Sava, Israel
    Tel: (972) 744-3826
    Fax: (972) 744-2640

  3. I have obtained all the images on my blog after a search in Google – they are not my own. I have hence credited the location and source of the images I have obtained. I will be glad if you link to my blog, but you can give all credit to the original websites.

    I am also very interested in your research work, please write to me more about it if possible.
    Thank you.

  4. local_yokel said

    Hi,

    Would it be right to count deforestation as a major factor too, considering that loss of vegetation on slopes can seriously affect their integrity.

    Closer to “home” there are reports from meghalaya of an increasing number of landslides ( no figures only “reports” but credible) due to the loss of forest cover , and more importantly grass cover.

  5. luis diaz said

    Could the vibration produced by the machinery at a detergent factory which operates 6 days a week 24 hours a day cause a landslide? The factory is located on the north side mountains that shape Guatemala City`s valley. About 3 weeks ago cracks on the ground started forming around the factory. The cracks are about 30 to 50 cm. wide and who knows how deep (12 mts. long poles have been introduced in the cracks to try to reach the bottom to no avail). Cracks have appeared both up-hill and down-hill from the factory at distances ranging from 300 to 1000 mts from the vibrations source (industrial machinery). Preliminary speculations point to soil saturation but our rainy season ended 3 months ago and we haven`t seen much rain since. The factory was established about 75 years ago as a small family business. About 10 years ago the factory was purchased by a multinational and has expanded greatly. Noise and vibrations have been on the rise over the last 3 years.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: