Date of Graduation


Document Type

Problem/Project Report

Degree Type



Statler College of Engineering and Mineral Resources


Civil and Environmental Engineering

Committee Chair

Hota GangaRao

Committee Co-Chair

Udaya Halabe

Committee Member

Udaya Halabe

Committee Member

Mark Skidmore


Retaining walls are used as an alternative to installing drainage and soil reinforcement, depending on site conditions. This report discusses the design of a retaining wall with steel soldier piles and lagging elements for rocky slopes. The design consists of six different options, three options with a span of eight feet and three options with a span of ten feet between soldier piles. The three options for both spans are the same concept but designed for different load conditions. These options include: timber with glass fiber reinforced polymers (GFRP) wraps, reinforced concrete with GFRP wraps, and an FRP Prodeck system resisting horizontal thrust as a beam supported by soldier piles. The two options with a GFRP wrap shell are recommended to be constructed using the resin infusion manufacturing process to achieve a better quality lagging element.

Resin infusion is an FRP manufacturing method in which an object is first wrapped with a dry fabric, placed in a bag and all air is removed from the bag with a vacuum pump. Once the object has reached the atmospheric vacuum pressure, resin is infused into the sample and cured while the plastic sheet provides a compressive force on the FRP which creates a better quality bond. The resin is then cured at room temperature.

A bending test is performed on seven railroad ties in this report. One control tie, three ties wrapped with GFRP using the hand lay-up method, and three resin infused ties with GFRP. The railroad ties were used in the field prior to testing. Along with performing a bending test on all seven railroad ties, a digital tap hammer was used to determine the bond quality on one railroad tie wrapped using the hand lay-up method and one tie wrapped with resin infusion. The results for this test suggest that resin infusion produces a higher peak bending stress, better bond quality, and a more consistent bond. The composite modulus of elasticity wasn’t able to be differentiated between the samples due to the inconsistency with the railroad ties used.

The data herein proves that resin infusion produces a higher peak bending stress and better bond quality compared to hand lay-up. Resin infusion is a more expensive manufacturing process and it may create some complications such as resin not traveling through the entire specimen or the specimen not curing properly. Proper materials and experienced personnel must be present, but when used properly it is a more effective FRP reinforcing method.