---
title: "Kinematic tests for failures"
subject: "Engineering Geology II"
chapter: 6
key: "semester_4/engineering_geology_ii:kinematic-tests-failure"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/kinematic-tests-failure
site: BCT Engineering
---

# Kinematic tests for failures

Engineering Geology II · Chapter 6: Measurement, analysis and interpretation of structural geological data

- Asked in: 2068 Magh, 2 marks
- Video: [Geology: Kinematics of Rock slope](https://www.youtube.com/watch?v=TnH3_S0z-aA) — Dr. Mohit Kumar Puniya
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/kinematic-tests-failure
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-6

## Question

What are the kinematic tests for failures?

## Short answer

Kinematic tests check if discontinuities permit block movement. Plane failure needs dip direction within ±20° of the slope and friction angle<plunge<face dip. Wedge failure requires the intersection plunging out with its plunge between friction angle and face dip. Oppling needs planes dipping steeply into the slope with dip≥90°–face dip+friction angle.

## Answer

**Kinematic analysis** checks whether the geometry of the discontinuities permits a block to move out of a rock slope, without considering forces. It is done on a stereonet for each failure mode (Markland test and others).

| Failure | Test (kinematic condition) |
|---|---|
| **Plane** | Dip direction of plane within $\pm 20^\circ$ of slope dip direction; $\phi < \psi_p < \psi_f$ (pole inside the daylight envelope, outside the friction circle) |
| **Wedge** | Line of intersection plunges out of the face; $\phi < \psi_i < \psi_f$ (intersection point between the slope great circle and the friction circle) |
| **Toppling** | Planes dip into the slope (dip direction about $180^\circ$ from the slope's, within $10^\circ$ to $30^\circ$); $\psi_p \geq 90^\circ - \psi_f + \phi$ |

If a mode passes its test, the slope is kinematically unstable for that mode and a stability calculation (factor of safety) is then required. If none passes, the slope is kinematically stable.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does kinematic analysis check?
   A. Forces on blocks
   B. Factor of safety
   C. Whether discontinuity geometry permits movement, ignoring forces
   D. Rock strength
   Answer: C. It checks geometry only; stability calculation follows. (Key point: Meaning)

2. Which is the plane failure test?
   A. Dip direction within 20° of slope and phi < psi_p < psi_f
   B. Dip into the slope
   C. Line plunge between phi and psi_f
   D. psi_p > psi_f
   Answer: A. Plane must daylight and exceed friction. (Key point: Plane test)

3. What if a mode passes its test?
   A. Slope is safe
   B. Nothing
   C. A stability calculation (factor of safety) is required
   D. Slope is flattened
   Answer: C. Kinematically unstable slopes need FS check. (Key point: Next step)