Mohr/Coulomb Failure Calculations
| Table of Calculations | Equation(y= mx + b) | Normal force 400 pascals | Friction angle (degrees) |
| Material A | y=0.696x +59.054 | 2843.1 | 34.8 |
| Material B | y=0.7171x +3947.8 | 6819.1 | 35.6 |
The cohesive material is material B due to its higher cohesion value of 3947.8 compared to the cohesive value of 59.054 for material A. The cohesion value is equal to the y-intercept. The friction angle is equal to the arctan of the equation slope for each material.
Riverside Ave Slide Failure
| Slab thickness (m) | Failure plane angle(degrees) | Cohesion (pascals) | Saturation depth (m) | |
| Variable | 2-20 | 30-50 | 5000-12000 | 0.5-3 |
| Dry Density (kg/m3) | Wet Density (kg/m3) | Gravity (m s-2) | Phi angle (degrees) | |
| Fixed | 1800 | 2200 | 9.8 | 30 |
Decreasing the slab thickness, increasing the failure plane angle, decreasing the cohesion, and increasing the saturation depth all helped to lower the Factor of Safety below 1. With holding the other parameters fixed, increasing failure plane angle above 35, decreasing the cohesion below 7500, increasing the saturation depth above 1, and decreasing the slab thickness below 5 all lead to a factor of safety value of less than 1 leading to a slope failure.
These model results are consistent with the landscape changes overtime resultant from impacts of dumping, deforestation, increased impervious surfaces, and increased runoff. The unconsolidated fill material with low cohesion, and a high failure plane angle would also be a factor in the slope failure. Changing the variable parameters from values expected from natural conditions with high cohesion, high vegetation, low impervious surfaces and runoff, and a lack of dumping and deforestation to values expected from current conditions did increase the potential for slope failure. The slab thickness and failure plane angle are independent. variables in the sense that it’s hard for human disturbances to impact these variables to the same extent as some of the other variables such as cohesion and saturation depth.