Friday, 14 May 2010

Rotational Slip.

Hello everyone,
Just lately I've been intrigued by large slips of earth and mud at the sides of motorways and roads. Having a Mining & Civil Engineering background I can't help but notice things like this.
So I thought it may be a good thing to blog about and try to put across a few leadership principles across at the same time.
First a definition:
Rotational Slip;

Form of mass movement where material moves suddenly along a curvilinear plane. Also called a slump.

The Principle being; Rainsplash is a microscale process that can be quite effective in moving material on slopes. The impact of rain droplets on the soil surface often detaches individual grains of soil moving them some distance from their source. On flat surfaces, the effect of rain drop impact is to redistribute the material without any net transport in a particular direction. However, on a slope the influence of gravity and slope encourage more material to be redistributed downslope rather than upslope. When slopes become 25 degrees or greater, almost all the redistribution occurs in a downslope direction.

Don't worry the car or the people inside the car were not harmed in any way during the making of this blog.

A variety of processes exist by which materials can be moved through the hillslope system. These processes are generically known as mass movement or mass wasting. The operation of mass movement processes relies upon the development of instability in the hillslope system. Under these conditions, failure of the slope material can occur on a range of time scales. Some types of mass movement involve rather rapid, spontaneous events. Sudden failures tend to occur when the stresses exerted on the slope materials greatly exceed their strength for short periods of time. In many cases, type of mass movement is produced by the operation of short term trigger mechanisms. Mass movement can also be a less continuous process that occurs over long periods of time. Slow failures often occur when the applied stresses only just exceed the internal strength of the hillslope system.

What are the sources of the stresses and strength acting within hillslope materials? As we have noted, a major source of stress is the gravitational force. The magnitude of this force is related to the angle of the slope and the weight of hillslope sediments and rock. The following equation models this relationship:

F = W sin Ø

where F is gravitational force, W is the weight of the material occurring at some point on the slope, and Ø is the angle of the slope.

The Cyclist just manged to escape the slip but strained his left thigh as he peddled quickly away.

I appreciate that most of you who usually follow my blog will by now be wondering what I am going to say, hopefully you are still reading this.

Well a few comments;

  • When all looks well and a new project has just been finished a few drops of rain can test the stability of what you have accomplished.

  • Gravity is a great leveller.

  • Understand the materials (people) you are working with.

  • Mass movement often causes great holes somewhere.

  • Sudden failure happens when we put too much stress on a certain area of the organisation.

  • Be careful about the hill (project) you may be ascending, make sure you know what lies beneath.

  • The Magnitude of the slip is related to the slope and angle you are working at, take care its not to steep.

  • Regular inspection of your working environment is required.

The following pictures where taken along the newly built B6474. the slip occurred as a result of the prolonged rain spell we had a few months ago.


  1. Thank you Andrew, I enjoyed reading your analogies between this environmental occurrence and leadership. Very astute.

  2. Some interesting thoughts there, Andy, which I will try to absorb!