Date of Award

12-2015

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil and Environmental Engineering

First Advisor

James A. Bay

Second Advisor

Marc Maguire

Third Advisor

John D. Rice

Abstract

Mechanically Stabilized Earth (MSE) walls restrain hillslopes to unnatural gradients using reinforced soil. Traditional MSE walls are constructed of large reinforced concrete panels bolted to steel strips for soil reinforcement. Segmented Retaining Walls (SRWs) are a form of MSE walls composed of precast concrete modular blocks that incorporate geosynthetic soil reinforcement. In comparison, traditional MSE walls have faster construction times and are typically stronger, but SRWs have increased in popularity because they are much cheaper to build.

There are many precast companies that produce different SRW block designs, these blocks have facing areas that range from 1 to 13.75 sq. ft. and can weigh approximately 90 to 2,000 lbs. There are advantages to both block types that must be addressed during design. Typically construction costs are lower for small blocks because they can be placed by hand rather than using equipment. Large blocks require less construction time but are usually more expensive to fabricate.

Oldcastle is a precast company that has several modular block designs. The newest model called the Mega Wall block is 5.5 feet wide, 2.5 feet tall and weighs approximately 2,000 lbs. The block is designed to accommodate both welded wire mesh and geosynthetics soil reinforcement. Prior to being released to the market design strengths must be determined through laboratory testing.

This report presents the results of the Mega Wall block welded wire mesh connection capacity. Three tests were performed by pulling the welded wire mesh to failure under simulated overburden pressures. Results of the testing show that welds in the wire mesh failed well below the yield strength of the steel. As the wires were pulled, the mesh applied stress concentrations to edges of the concrete grooves. Conical concrete failures were observed in the concrete after each test. After the concrete failed, the mesh was allowed to bend considerably, which began to apply a bending to the welds already experiencing shear stress. This excessive bending deformation caused premature failure in the welds during testing.

In order to achieve higher connection capacities, several modifications to the Mega Wall block design were presented to Oldcastle. These suggestions were acknowledged but not implemented. Oldcastle was not interested in testing modifications to the block and testing was terminated. It is assumed that the Mega Wall block design will not be modified and that Oldcastle will not recommend using the welded wire mesh connection.

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