Table 1: Critical length .

h(m) = 120 m
= 500 m

0.19.264.54
0.218.539.08
0.327.8013.62
0.437.0618.16
0.546.3322.7
0.655.6027.23
0.764.8631.77
0.874.1236.31
0.983.3940.85
192.6545.39