Question

The schematic stereographic projection below shows dip amount and dip direction of three sets of joints (J1, J2 and J3) on a hillslope. If the internal friction angle of the hillslope material is 30°, the strike of the potential failure joint plane (in azimuthal convention following right hand rule) is _____degrees. (In integer)

Answer 1

Correct Answer: 355

To determine the strike of the potential failure joint plane, we analyze the given joint sets and the friction angle of the hillslope material.

The potential failure plane is typically parallel to the hillslope and has a dip direction close to the direction of maximum slope.

Given:
1. Hillslope dip: 50°, dip direction: 090°
2. Internal friction angle: 30°

The critical condition for sliding, or the potential failure plane, occurs when the dip direction of the joint plane matches the dip direction of the hillslope.

Among the given joints:
J1: Dip 40°, Dip direction 085°
J2: Dip 15°, Dip direction 095°
J3: Dip 45°, Dip direction 300°

The joint plane closest to the hillslope's dip direction of 090° is J1 with a dip direction of 085°.

Since the direction is close, and accounting for the internal friction angle, J1 is thus the potential failure plane.

In azimuthal convention (right-hand rule), J1's dip direction is 085°, meaning the strike is 085 - 90 = -5, converted to positive as 355°.

This solution fits within the given range (355,355).

Answer: 355°