Development of soil abrasivity testing for soft ground tunneling using shield machines

Primary and secondary wear in soft ground tunneling using various types of shields has a major impact on machine operation, utilization, and tunneling costs. Wear occurs due to interaction between abrasive soils and cutters, as well as other components of the machine which come to contact with the muck. However, lack of a standard or universally accepted test for soil abrasivity in the geotechnical investigations has made the prediction of tool wear a difficult task. This paper introduces a new test device, designed to measure soil abrasion and the result of initial testing at the Pennsylvania State University. The testing system is configured to simulate the working condition of the cutting tools in excavation chamber of pressurized face shields. This includes the high contact stresses between the tool and the soil, maintaining the original soil size distribution, field moisture conditions, and possibility of applying high ambient pressures as well as soil conditioners. The preliminary results of testing on several soil types, moisture conditions, and various tool hardness is presented. The test set up is discussed to provide more detailed information on the testing conditions and potential implications in practical applications.

► New testing system for tool wear of soft ground shield TBMs has been introduced.
► The procedure for performing the Penn state soil abrasion test has been introduced.
► The initial results related to this testing device have been reported.