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Abstract In order to study the inherent relation between the mechanical behavior and the microstructure of the tailings used for building dams，we have developed an observation apparatus of micromechanics and deformation of tailings. It is composed of load device，compression chamber and appurtenances，local stress monitoring system，microscopic observation system. This apparatus has following advantages：(1) Tests performed on this apparatus can show the comprehensive influence of local stress，pore water and porous water pressure，drainage conditions in tailings dams on microstructure and particles motion. (2) The tests by this apparatus can be loaded under the modes of static load，static load and unload，dynamic load，dynamic cyclic load. (3) The compression chamber，which uses the structure of stainless steel cylinder with an inlaid glass fibre reinforced plastic cylinder，can offer the load pressure of 2.5 MPa. (4) When pore water is flowing in tailings，we can observer the movement of pore water and particles，microstructure and its deformation under load，also can monitor the pore water pressure by this apparatus. (5) The local stress can be real-time monitored through installing several pressure transducers inside tailings. (6) The self-made dynamic microscopic observation apparatus，which we have chosen，can be easily adjusted and track the movement of the point. The microscopic observation experiments of tailings are carried out by this apparatus under the loads of 0.3，0.6，0.9 MPa，and the result showes that：with the increasing of the load and the time，the amount and the size of macropores reduce，particles have been bound to clump by weak bound water which is transformed from strong bound water. With the increasing of the load，the displacement increases nonlinearly，and the increment of the displacement become smaller. With the effect of the load，the stress and the microstructure deformation show that：the lower of the specimen lags the upper of specimen，the local stress increases wavily；and the value of peak of local stress changes very heavily；the displacement has a stepped increment，and finally becomes a stable level.
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Received: 23 December 2010
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2011, Vol. 30 
