Hello. If you are referring to the circular failure charts for example, [from Chapter 8: Circular Failure in Rock Slope Engineering - Civil and Mining - 4th Edition by Duncan C. Wyllie and Christopher W. Mah, 2004] the conditions under which circular failure will ocular is when the individual particles in a soil or rock mass are very small compared with the size of the slope. These charts have been developed by running many thousands of circular analyses from which a number of dimensionless parameters were derived that relate the factor of safety to the material unit weight, friction angle and cohesion, and the slope height and face angle. There are examples using this method for hundreds of meters and others for tens of meters (or smaller). For other charts, consider the height range permitted and in all cases try to find the source of these charts and any limitations (data range) to ensure you are working within the data range the chart was developed for.
@@itascasoftware Thank you for the response. I was actually asking about slope heights vs slope angle on emperical design charts. But this was addressed later in the video.
