This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Abrasivity is an important property of soil which it is often overlooked due to its less than critical impact in many applications, including construction projects. With the increased use of soft ground tunneling, the issue of tool wear and life has become very crucial since in many cases tool inspection, maintenance, and replacement is performed under pressurized conditions or so called ?hyperbaric interventions?. This is a time consuming and costly step in tunneling, and working in tunnel face under such conditions is very dangerous and risky. There is no test or index that can provide a quantitative measurement of soil abrasivity, especially as it may pertain to wear on the excavation tools. The available measures of soil abrasivity are limited to the evaluation of the Moh?s hardness of the constituent grains and minerals. In recent years, there has been some interest in this field and a few preliminary research programs for testing soil abrasiveness have commenced. These programs primarily involve application of existing rock abrasivity measurement systems such as Norwegian Abrasivity Value AV or French LCPC test to soil. There are inherent shortcomings of these test system for application in soil. They change the grain distribution of the soil, they are performed on dry samples, cannot simulate the operational conditions of the excavation face such as moisture content and stress levels, and can not include the soil conditioners and their impact on the tool wear.
We will study the parameters involved in soil abrasion and its impact on cutting tools. This will include study of the actual conditions at the face of the soft ground excavation systems to be able to closely simulate the field conditions in the testing system. Simultaneously, a study of the special grades of steel and tungsten carbide commonly used in excavation tools will be performed to develop an understanding of their surface characteristics as related to wear mechanism in soil excavation. This will include specialized tribology tests to see the interaction of these materials and various soil types and constituent minerals and grains.
Based on the result of these studies, an appropriate soil abrasivity testing machine will be developed. This system will go through a critical review by team members and detailed shop drawings will be produced. The device will be fabricated and will be used to perform parametric studies on various factors influencing the soil and tool interaction and wear of the cutting tool. This will include the testing of the material properties used in the device to represent the cutting tools, various speeds for propellers and peddles, different angles in the propellers to mimic the stress levels between the cutting tool and soil, testing soils in dry, wet, saturated, and at higher water pressures, and the impact of various soil types and compositions. The results will be the selection of a set of operating parameters for the testing to yield consistent, repeatable, and meaningful results to be used as soil abrasivity index.
Broader Impacts: Once the testing system is established, a standard method for measurement of soil abrasivity will be introduced to complement the existing soil mechanics testing. The applications will be to predict tool life more accurately, improve tool design and material, and to objectively evaluate the impact of soil conditioning agents. There will be a multitude of additional developments linked to this index once it becomes a standard means of measuring soil abrasiveness for application in civil, mining, and petroleum as well as manufacturing sectors serving these industries. The test could also be used in development of new materials and cutting tools used on various excavation machines.
