Refractor Velocity Constraint

The other major constraint will be the refractor velocity, V2=4187 m/s determined from reverse profiles on line 1. This constraint is necessary since reverse profiles were not possible for line 3. As can be seen on Figure 34, the hammer blows fired broadside into line 3. The location for the source was not arbitrary, but chosen to be far enough away from all the geophone stations on line 3 (beyond the cross-over distance for the refraction). The bedrock refractor was granite, the overburden was silty sand with gravel (Unified classification SM). Soil testing indicated an internal angle of friction of $31.5^{o}$ . Given that the topographic slope was about $30^{o}$ , the in place overburden was judged to be at the angle of repose.