(1. Key Laboratory of Ministry of Education of China for High-efficient Mining and Safety of Metal Mines，University of Science and Technology Beijing，Beijing 100083，China；2. School of Civil and Environmental Engineering，University of Science and
Technology Beijing，Beijing 100083，China)
Abstract：Paste made of tailings and waste rocks was used to backfill the subsidence caused by mining in a certain mine. The strength of paste is directly related to the effect of the disposal and safety production underground. The content and grain size of waste rocks are key factors influencing shear strength. In this regard，a test is performed on the test block of disposal body with the modified small direct shear apparatus so as to gain the influence law of the disposal body?s shear strength，cohesion and internal friction angle ，which are related to the waste rock?s content and grain size. Its strength mechanism is analyzed with the modified adhesion theory of friction. The test result shows that，as the content of waste rock increases，the value tends to decline and the value tends to increase；the shear strength may be divided into cohesive force control，combined control of cohesive and friction and friction control according to the waste rock content and its grain size；the shear strength tends to drop before increasing as the content of waste rocks increases，and reaches its minimum value when the content is between 20% and 30%；the shear strength increases with the grain size；the stress-strain curve shows strain softening in low stress zone and strain hardening in high stress zone. The contribution of friction strength to shear strength reaches 80%；and the macro shear strength depends on the shear strength between grains；the change of waste rock?s grain size and content actually changes the contact area between the grains of the disposal；so that it changes the friction strength between grains and thus changes the macro shear strength.
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2013, Vol. 32 
