GEOTECHNICAL EVALUATION OF QUESTA MINE MATERIAL, NEW MEXICO, USA

In this research work, geotechnical properties of Questa rock piles and their natural analogs were investigated.Particle shape analysis, wet and dry sieving, and direct shear tests were conducted. In addition, the results of 12-inch direct shear tests and 4-inch diameter triaxial tests from published documents and Golder laboratory were studied. The particle shape analysis showed that rock fragments at the test locations of Questa mine are mainly subangular, subdiscoidal and subprismoidal.Wet sieving methods results in more fines than the dry sieving. The increase in fines is a result of the presence of water in wet sieving that dissolves the cementation and cohesion between particles and causes disintegration of clumps that act as solid rock fragments during dry sieving methods. The shear strength of Questa mine material is affected by the particle size and shape. In general, larger samples contain lesser amount of fines that result in higher friction angles. The peak friction angle of the materials from Questa rock piles and analogs reduces as the water content increases. 12-inch direct shear and 4-inch diameter triaxial tests show similar peak friction angles of 40° or above.