ABSTRACT:

The triaxial compression tests under different confining pressures are conducted to sylvine samples with TAW-2000 triaxial compression testing machine. The strength and deformation characteristics of sylvine are studied. It is shown that under lower confining pressure, the failure mode of sylvine is shear failure; while if the confining pressure exceeds 10 MPa, sylvine shows obvious inflation phenomenon. It is an approximately proportional relationship between the peak strength and confining pressure. The change rule of elasticity modulus along with confining pressure is also analyzed. The results show that with the increase in confining pressure, elasticity modulus gradually increased. Mohr's envelope is drawn according to the results of triaxial compression test, and the shear strength parameters are obtained with regression analysis. The research results can be used as a reference for the design and study of sylvine mines.

1 INTRODUCTION

Rock strength and deformation characteristics are the foundation of theoretical calculation and design, which is one of the significant topics in rock mechanics and engineering. In underground mining, rock mass are always under three dimensional state of stress. Therefore, conducting a study on rock strength and deformation characteristics under the condition of triaxial compression has engineering practical significance on failure mechanism of rock. Former scholars carried on lots of triaxial test researches on marble, detrital sandstone, anhydrite, etc., and some useful conclusions are obtained (Jiang et al. 2004, Meng et al. 2003, Yang et al. 2005).

Sylvine is one of the 50 minerals in acute shortage in China, which needs to be explored and developed urgently. However, roof caving accidents frequently happen during the exploitation process in underground mines, which can cause loss of life and personal injury. There is a large difference between sylvine and other rocks in mechanical properties, which is reflected in the fact that its strength falls between hard rock and soft rock, and sylvine is prone to deliquescence when it meets water (Yang et al. 2008, Liu et al. 2004). Based on the characteristics of sylvine, both strength and deformation characteristics should be taken into consideration, thus it is of particular importance to conduct research on the mechanical properties of sylvine.

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