A few unexpected results for GWL changes 1

[Anand478]

Hi everyone,

I have carried out a study to find the effect of raised GWL on various slopes and angles, and as expected the higher the slope(in terms of height and angle) the lower the critical GWL(FOS of 1).

For all cases of increasing the angle the crit GWL decreased.

The GWL also decreased for most case in terms of increasing the height but keeping the angle constant, BUT for a angles (28,30,32,34) the crit GWL stayed constant even thought the height was being increased?

I can conclude that the steepness of an angle has more effect that an increase of height, but I am unsure why the Crit GWL level is constant in some cases?

Kind regards,

Anand

 

[killswitchengage]

well depends on the material you used first . in any case , i think that water acts more to provide a critical failure line and that its level can be irrelevant in respect to instability and yes for clays steepness and height are the major factors

 

[Anand478]

Hi Killswitchengage,
Im not sure you understood my findings, the crit GWL was the same for many cases where I kept the slope angle the same but increased the height(by increasing X axis), and I would have expected the crit GWL to become lower each time the height was increased, but this was not the case...

However when I increased the angle only, the crit GWL lowered on every occasion

Hope that clears it up

Kind regards,

Anand

 

[BigH]

I can't remember the article but way back, the shape of the groundwater level compared to a cut slope was looked into - with no other measures the groundwater will break out about 1/3 the height from the bottom of the slope in the equilibrium condition. If you have a flat slope, the change will be much more gradual than for a steeper slope. In stability situations, Chuck Brawner of University of British Columbia advised that positively treating the groundwater conditions can increase the stability by 30% compared to 10% by changes (not super drastic ones) in geometry (Rule of thumb).