Slopes

On October 31st, 2019 a landslide occurred on Riverside avenue. As seen on my page "Riverside Avenue Topography" a landslide is not all that uncommon on Riverside avenue. But what are the mechanics of the slope malfunction, and what slope characteristics will cause the next slide?

Slope Mechanics oF riverside Avenue

Below is the calculation and values I determined where the best for the 2019 Riverside slide. The first thing determined was that the slope material was composed primarily of sand with larger chunks in it composed of cement, metal and other trash (i.e metal bars and cars) which has been dumped over the edge of the slope. By determining that the material was most lily sand we could determine the angle of 30˚which is at the lower end of the range given for sand for friction angles. For the density of the dry and wet material I used 1000 and 1900 kg/m^3. Gravity as always will be a constant 9.8m/s^2.

The thickness of material and the ratio of saturated to unsaturated soil was the key for what caused the slide. On a dry day with all the conditions set above the slope side would be considered safe, with an f value of 1.14. But as soon as the rain is introduced the slope quickly deteriorates into an unsafe landslide with an f value of 0.94.

This is consistent with land use change over time as the fill used to replace the original materials of the slope has made it much weaker and more prone to slides. With the countless changes such as deforestation , dumping and fill the slope strength has been reduced dramatically causing it to be prone to slides. To add to the onslaught of problems paving of the road above and driveways has only increased runoff to the slopes causing them to be more saturated then they would have been sans paving, in turn making the slopes more unstable when rain falls.

Photos taken by Kate Silvia