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Basic Principles of Scrap Tire Earth Retaining Structures

D. Allen Hughes, P.E.


Course Outline

I. Introduction
1.2 Significance of Used Tire Problem
1.4 Current Applications of Scrap Tires
1.4.1Energy Recovery
1.4.2 Scrap Tires in Civil Engineering Applications
1.4.3 Wet Poured Layers
1.4.5 Rubber Modified Asphalt (RMA)
1.4.6 Marine Reefs and Shoreline Protection
1.4.7 Earth Retaining and Erosion
II. Control Structures
2.2 Tire Retaining Walls: Case Studies 
2.2.1 Retaining Wall at the Plumas National Forest
2.2 3 Public Works Department's Slope Stabilization Project
2.3 Concrete Boxes Filled with Compacted Tires in the Construction of Retaining Walls
2.4 Tire Bales in the Construction of Retaining Walls
2.4.1 New Mexico Project.
2.5 Facing Materials for Tire Retaining Walls
2.5.1. Shotcrete
2.5.2. Stucco
2.5.3. Vegetative Covering
2.5.4. Geofabric
2.5.5. Concrete Blocks
2.5.6 Combinations
III. Stability Analysis and Design Of Retaining Wall
3.2 Mechanically Stabilized Earth Tire Retaining Walls
3.2.1 Modes of Failure
3.2.1.1 External Stability
3.2.1.2 Internal Stability
3.2.2 Stability Analysis and Design of Retaining Wall
3.3 Gravity Retaining Walls
3.3.1 Modes of Failure
3.3.2 Stability Analysis
IV. Conclusions and Recommendations
4.1 Overview
4.2 Conclusions
4.2.1 Costs
5.2.2 Constructability
4.2.3 High Volume Application
4.3 Recommendations
4.3.1 Test Wall
5.3.2 Economic Analysis
5.3.3 Environmental Impact

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will have learned or been exposed to the following:

Intended Audience

This course is intended for use by engineers, planners, regulators, and landscape architects.

Benefit to Attendees

Students will gain an understanding from this course of the benefits of possible new uses for scrap tires. The course content may also be useful as part of a guide for developing a tire reduction or reuse plan.

Course Introduction

This course is based on the publication, “Use of Whole Tires In Earth Retaining Structures” by the Texas DOT, US DOT, FHWA and The Center For Multidisciplinary Research In Transportation at Texas Tech University. The techniques and methodologies described in this course document are evolving rapidly.

According to the Rubber Tire Manufacturers Association, in 2010, 270 million tires were generated in the United States. Approximately 66 percent of these scrap tires were productively used or recycled. Another 12 percent were placed in landfill or monofill. Estimates also indicate that the current stockpile of scrap tires in the US is around 700 to 800 million. Scrap tires create unique problems in landfill disposal, not only because of their large numbers but also because of the nature and properties of their chief component, rubber. Rubber tires are difficult to compact in landfills because they tend to rise and even pop through the groundcover as other waste materials compact around them. Their buoyancy causes them to rise to the surface after rainfall leaving behind empty spaces that damages the landfill's stable, carefully layered composition. In addition, the hollow shape of the tires fills with decomposition gases creating a serious fire hazard. Large tire fires can burn for weeks causing the rubber to decompose into oil, which may pollute ground and surface water, as well as gas and carbon black. Moreover, the tire rubber is a dense, durable and elastic material that does not undergo natural decomposition in landfill environment easily. Rainwater accumulates in tire piles creating an ideal environment for mosquitoes. For these reasons, many landfills do not accept large quantities of discarded tires, while others charge a high tipping fee for their disposal. Consequently, scrap tires are frequently placed in dedicated stockpiles or in illegal tire dumps.

Course Content

This course is based on the publication, “Use of Whole Tires In Earth Retaining Structures” by the Texas DOT, US DOT, FHWA and The Center For Multidisciplinary Research In Transportation at Texas Tech University.

Use of Whole Tires In Earth Retaining Structures

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Course Summary

With the increasing number of scrap tires in the US and Canada, the problem of scrap tire disposal will only grow. Regulated stockpiles and illegal dumps pose major environmental and safety problems, such as combustibility and possible toxins in the leachate. They also provide habitat for insects such as mosquitoes. Mechanically stabilized earth and gravity walls can be a good way to reuse large quantities of tires. They appear to be economically competitive and no harder to construct than conventional walls. While the exact costs of all types of scrap tire earth retaining walls is unknown, the assumption can easily made that the scrap tire walls will be cheaper.

As a significant percentage of scrap tires from developed countries end up in stockpiles and undeveloped countries, the demand for constructive uses of scrap tires in undeveloped areas can increase with the higher cost and scarcity of conventional materials, the relatively lower cost of labor, and the abundant supply of cheap or free tires. The further development of properly engineered uses for scrap tire retaining walls can help reduce the amount of stockpiled tires in developed and undeveloped countries.

Throughout the US and Canada, millions of waste tires are being generated each year. Many of those tires could be used as cheap and readily available construction materials for earth retaining structures and other civil engineering projects.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.