Investigation of Geotechnical Properties of TBM Spoil from the Follo Line Project

Abstract

In connection to the Follo line tunnel project this thesis investigate some of the existing experience on use of TBM spoil as a construction aggregate. Compaction control tests provided by Bane NOR for the deposit at Åsland are processed and presented. In order to investigate the deformation properties of the material large scale oedometer tests were conducted at the Norwegian University of Science and Technology (NTNU), Trondheim.

The TBM spoil is found to be a well graded, water sensitive material with a light frost susceptibility. The Troxler density gauge and the dry density from the excavation tests reveal that the achieved compaction is within 95\% of the standard Proctor maximum for field control. While only 22\% of plate load tests pass the requirements set for the specific project it is suspected that this might be caused by not using a layer of plaster to level the surface before conducting the test.

The permeability of the soil is roughly equivalent to that of a fine sand or a coarse silt. This corresponds well with the fines content revealed by the dry sieving of approximately 10\%.

The oedometer tests were conducted on material with 6 - 13\% water content. The water content affected the achieved compaction and strains of each test. The tests resulted in strains of 3.5 to 10\% with a maximum load of 500kPa. The oedometer modulus is between 5 - 20MPa and the achieved dry density at the end of the tests were 1.83 - 2.27 t/m3 For a possible load of 50kPa on terrain level, the results indicate a maximum settlement of approximately 0.33m for a 30m fill.