When using TCP information, consider both skin friction and point bearing for drilled shaft capacity. Calculate total allowable skin friction by multiplying the perimeter of the shaft by the unit value for allowable skin friction derived from Figure A1-2, Figure A1-4, or laboratory data. For drilled shafts, apply a reduction factor of 0.7 to allowable skin friction values derived from Figure A1-2 or from laboratory testing to account for disturbance of the soil during drilling. Do not apply the reduction factor to allowable skin friction values obtained from Figure A1-4. Accumulate skin friction along the length of the shaft beginning at the previously defined disregard depth and continuing down to the tip of the shaft. Calculate total allowable point bearing by multiplying the area of the drilled shaft times the unit value for allowable point bearing derived from Figure A1-3, Figure A1-5, or laboratory data. If softer layers exist within two shaft diameters of the proposed tip, use allowable point bearing values for the softer layers. If drilled shafts are to be tipped in very hard material that is overlain by soft strata, the skin friction contribution of the softer strata may be disregarded in design. However, do not ignore the contribution of significant amounts of competent material to tip in rock. In many areas of the state, rock is overlain by thick layers of material that can support considerable loads.