Figure Ex. 17.8 shows a drilled pier penetrating an IGM: clay-shale to a depth of 8 m. Joints exists within the IGM stratum. The following data are available: L_{s}=8 m \left(=z_{c}\right), d=1.5 m , q_{u}(\text { rock })=3 \times10^{3} kN / m ^{2}, E_{i}(\text { rock })=600 \times 10^{3} kN / m ^{2} concrete slump = 175 mm, unit weight of concrete \gamma_{c}=24 kN / m ^{3}, E_{c} \text { (concrete) }=435 \times 10^{6} kN / m ^{2}, \text { and } RQD =70 \text { percent, } q_{u} \text { (concrete) }=435 \times 10^{6} kN / m ^{2}. Determine the ultimate frictional load Q_{f}(\max ).