Design Guidelines for Test Level 3 (TL-3) Through Test Level 5 (TL-5) Roadside Barrier Systems Placed on Mechanically Stabilized Earth (MSE) Retaining Wall

The use of Mechanically Stabilized Earth (MSE) wall structures has increased dramatically in recent years. Traffic barriers are frequently placed on top of the MSE wall to resist vehicular impact loads. The barrier systems are anchored to the concrete in case of rigid pavement. Nevertheless, in case of flexible pavement, the barriers are constructed in an L shape so that the impact load on the vertical part of the L can be resisted by the inertia force required to uplift the horizontal part of the L. The barrier must be designed to resist the full dynamic load but the size of the horizontal part of the L (moment slab) is determined using an equivalent static load.

Current design practice of barriers mounted on top of MSE retaining wall is well defined for passenger cars and light trucks. However, the information of this impact level is extrapolated to heavy vehicle impact. Therefore, the bases of this research is to develop design procedure and to help understand the dynamic behavior of a barrier-moment slab system on top of an MSE wall when subjected to heavy vehicle impact loads.

In a first part, numerical analyses were conducted to better understand the behavior of the barrier-moment slab system when subjected to heavy vehicle impact loads. The full-scale impact simulations were used to develop the recommendation for designing and sizing the barrier-moment slab system.

In a second part, the barrier-moment slab systems defined to contain heavy vehicle impact loads were placed on top of an MSE wall model to study the kinematic behavior of the system. Loads in the soil reinforcing strips and displacements on the barriers and wall components are evaluated to define recommendation for design of strip reinforcements against pullout and yielding.

In a third part, a full-scale crash test on a barrier-moment slab system on top of an instrumented 9.8 ft. (3 m) high MSE wall is described and analyzed. The MSE wall and barrier system were adequate to contain and redirected the vehicle and, therefore, it served as verification of the proposed recommendation.

Finally, conclusions are drawn on the basis of the information presented herein.