Study On The Stratification Cracking Effect Of The Layered Rock Slope Caused By Blasting And Its Influence On The Stability Of Layered Slope

With the rapid development of our national economy, the infrastructure industry, such as highway, railway, airport, and water conservancy and hydropower engineering have gotten into an unprecedented high-speed development opportunity. These projects always meet all kinds of complicated environment and geology. So the slope stability problem becomes more outstanding and stern. The stability of rock slope mainly depends on the properties and the distribution in space of geological structure in rock mass, especially on the influence of blasting on the properties of geological structure during the excavation of rock cutting slope. It is the precondition of correctly analyzing the stability of slope caused by blasting dynamic to direct the related slope design and safe use. The blasting in layered rock mass with a weak intercalation has remarkable influences on the slope stability. So, how to analyze the stability of layered rock slope with weak intercalation becomes an important problem to be resolved with urgency.When the charge hole drill through weak intercalation of layered rock slope, with the erosion, impulse, and compaction of weak intercalation caused by explosion gases and blasting shock waves, the blasting cavity comes into being. In the area of blasting cavity the cohesive force and the internal friction angle have decreased to zero, and meanwhile, the cohesive force in the compact zone of weak intercalation decreases sharply, even loses completely, which is very harmful to the slope stability. On formation process of blasting cavity, with the explosion gases wedging into the interface between weak intercalation and rock mass, the rock formation on the top of the weak intercalation is bended upwards caused by explosion gases, which leads to the rock separates from the weak intercalation, that is to say, stratification cracking occurs. In the stratification cracking range, the cohesive force decreases to zero and the internal friction angle also decreases, which leads to the self-stability of rock mass reducing and the sliding resistance of slope decreasing. It is every easy to cause layered landslide, and even to lead the formed slope to landslide or collapse. So, it is essential for the analyses of the stability of layered rock slope with weak intercalation that the stress states of the slope rock during the blasting must be made certain and the corresponding mathematical mechanical model of blasting is to be established, based on which the reasonable calculation method of the dynamic stability of slope can be provided.Aimed at the stability analysis of layered rock slope effected by the erosion, impulse, and compaction of the weak intercalation caused by blasting, and applied on the theory that blasting gas is isoentropy adiabatic expansion in the lamination cracks and charge hole, the quasi-static mechanical model for the lamination of weak intercalation in layered rock slope was established during the deep-hole blasting. The explicit expressions of the quasi-static pressure in the blasting cavum and the critical lamination length of the weak intercalation were deduced. Through the study on the raise effect of the rock mass caused by the blasting gas wedging into the weak intercalation, the quantitative relationship between the stability factor of the latency slip and the parameters of charge, the mechanics parameters of the rock and the geometry size of the slope was obtained. A new approach for analyzing the dynamic stability of layered slope was opened.Applied on the theory of detonation fluid dynamics and two-phase flow theory of gas liquid, the mechanism of the compaction of the weak intercalation caused by explosive gases during the blasting was studied, and the motion mechanical model of weak intercalation was established. The quantitative relationship between the velocity of the weak intercalation, the final radius and the expansion time of blasting cavity and the parameters of charge, the mechanics parameters of the weak intercalation were obtained.The velocity of the weak intercalation caused by explosive gases was measured with the aid of a high-speed digital camera, and its variations was analysed. The shape and the size of blasting cavity in weak intercalation were gained, besides.The acoustic velocities of the models before and after blasting were measured with the acoustic detection technique. The variations and the cause of acoustic velocities in different measuring points were analysed. And based on the variations in different measuring points before and after blasting, a new approach to determining the radius of blasting cavity and the compact zone was come up.The characters of weak intercalation in other work conditions have been investigated through LS-DYNA3D program, and the thickness and the obliquity of weak intercalation, and the mass, the diameter and the ratio of length to diameter of the charge effect on the blasting cavities radius have been analyzed.At last, the blasting dynamic stability of the two typical layered rock slopes was analyzed using the quasi-static mechanical model presented and the result indicated that it was agreed with the engineering practice.