Repeat Prob. 3–86 for 0.4-m-wide concrete blocks.

Data from Problem 86

A retaining wall against a mud slide is to be constructed by placing 1.2-m-high and 0.25-m-wide rectangular concrete blocks (ρ = 2700 kg/m³) side by side, as shown in Fig. P3–86. The friction coefficient between the ground and the concrete blocks is f = 0.4, and the density of the mud is about 1400 kg/m³. There is concern that the concrete blocks may slide or tip over the lower left edge as the mud level rises. Determine the mud height at which 

The blocks will overcome friction and start sliding

The blocks will tip over.

FIGURE P3–86

1.2 m 0.25 m Mud Pm h