The field SPT N-value of 10 and energy efficiency (in percentage) of 50 are from field measurement at 5-m depth in a silty sand layer. The groundwater table is at the ground surface. The saturated soil unit weight (gsat) is 19 kN/m3 and the unit weight of water, w, can be taken as 10 kN/m3. Determine the corresponding shear strength using '= [15.4(N1)60]0.5+20 (Degrees). Need to consider stress correction