Test Study On Influence Of Blast Effect On Stability Of Bedding Rock Slope Including A Weak Interlayer

The stability of rock slope mainly depends on the properties and the apacial distribution of geological structure in rock mass,and it also depends on the influence degree of blasting on the properties of geological structure during the excavation of rock cutting slope.Blasting in layered rock mass including a weak interlayer has remarkable influences on the slope stability and these often cause landslide in part or in whole.According to the blasting of cement mortar model experiment of the open-air rock bench including a weak interlayer, measured by acoustic waves test,blasting experiment and shear test,this paper studies the stability effect rule of the single hole blasting in the rock slope including a weak interlayer.Based on the practical slope, according to the theories of similarity blasting, the rock slope blasting model with a weak interlayer is designed and the geometric parameter of the blasting model is provided.according to the relationship between the blasting pressure similitude of the blasting hole and the material strength similitude, also to the theory of isoentropic adiabatic expansion, the decouple coefficient range of the blasting model's charging structure are put forward.According to single hole bench blasting of the rock slope with a weak interlayer,five balsting bedding cracks tests are done.Based on the principle that the blasting cavity radius and the compaction radius are determined by the acoustic waves test,according to the comparison analysis of the variation characteristics of every test's acoustic velocity before and after blasting in different directions and different distances from the explosion source, the bedding cracks ranges of the blasting model are determined, and the relative error is less than 14% between the results of the acoustic waves test and the results of the direct observation.Under the explosion action with one gram explosive(charge of a detonator), the average blasting cavity radius and the average compaction radius are about 12.7cm and 22.4cm by five model blasting tests, and the both parameters changed little along different direction.According to shear model test principle,the calculation methods of the weak interlayer's mechanical parameters( c,tanφ) are derived. Considering the coupling effect on slope stability by blasting vibration and bedding cracks, the calculation method of stability coefficient of bedding rock slope with a weak interlayer by blasting effect is put forward.In order to explore the influence law of blasting bedding crack effect by sand rate,water content and thickness of interlayer,twenty model blasting tests are designed and done. According to analyzing and calculating the shear strength test data of the weak interface before and after blasting, the stability factor of the model slope are obtained before blasting,when blasting and after blasting. The analysis shows that: in the range of the test parameter, the mechanical properties of the interlayer and the slope stability are greatly affected by the water content and sand rate, and nearly unaffected by the thickness of the weak interlayer. The decreasing rate of stability factor is nearly unaffected by the physical and mechanical properties of the weak interlayer, so the blasting effect is the main reason for reducing the slope stability. Caused by blasting vibration and bedding cracks when blasting, the decreasing range of stability factor is from 62% to 65%, it means that only the stability factor of slope is more than 2.85 before blasting, the stability factor of slope will be more than 1 and the slope is steady when blasting. after blasting, blast bedding cracks decreases the self-stability of slope,and the decreasing rang of stability factor is from 30% to 35%, it means that if the stability factor of slope is less than 1.54 before blasting,the stability factor of slope will be less than 1 and the slope will be unstable after blasting.