As part of an open pit mine design a haulage road with 8 segments must be designed and constructed to link operating faces with crusher site. In order to achieve production targets and minimize haulage interruptions, a two-lane haul road must be constructed with allowances for a drainage ditch and other safety features. The largest truck on the proposed haul road is the CAT 785C. The tire pressure of the CAT 785C is 105 psi with a spherical contact area on the haul road surface. Load distribution ratio is 33:67 front: rear. The maximum speed of the CAT785C truck when travelling throughhorizontal curvesis20 mph.Assume that thefront overhang = rear overhang = 5 ft.

3. Estimate the contact pressures at a depth of 15 for limit of bearing pressure angles of:

a) 35

b) 60