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91 ramp effect of the berm. This could be a problem when berms contain a considerable amount of rock and very little soil. In such cases using material with a specific grade (size) mix may be necessary. This may be accomplished by maintaining a full load in the vehicle during the rite sinkage tests and by removing the surface layer of the berm, which may cause erro- neous strength values. QUALIFYING A BERM Tire sinkage values obtained during the field tests were found to be repre- sentative of the berm strength and can be used for quantifying the berm size recommendations. The tine sinkage val- ues are, however, somewhat subject to the surface condition of the berm. Therefore, care must be taken to assure that the surface effects are negligible. A field technique for qualifying a berm for its capability in restraining a haul- age vehicle is to drive a fully loaded vehicle forward up a berm at a 45° angle to a height equal to the axle height of the vehicle and then record the tare sinkage value (fig. 3). The value may then be checked against the size-strength curves of figure 2 to see if the berm is acceptable. GUARDRAILS Generally, berms constructed from available mine waste material will be less expensive than a guardrail installa- tion. However, there are cases where a guardrail may be needed, For example, placing a guardrail along a haulage road that is too narrow to construct an ade- quate sized berm on may be less costly than widening the road. The Barrier VII computer program6 was used to evaluate various guardrail Tire sinkage I configurations. This program predicts the response characteristics of the vehi- cle, the deformation of the restraining structure, and the damage generated by the impact of the haulage vehicle. The result of a properly designed guardrail is the redirection of the errant vehicle. Powell, C. H. Barrier VII: A Comput- er Program for Evaluation of Automobile Barrier Systems. Univ. CA, Berkeley, CA, Report UC SESM 70-17, Aug. 1970, 210 pp. \;~ \~`- \t Axle height) FIGURE 3. - Berm qualification test at a 45° vehicle approach angle.