Study Of Soft Rock Tunnel Smooth Blasting Quality Evaluation Based On The Hoek-Brown Failure Criterion

Soft rock is the most widely distributed a rock. It is often encountered soft rock,such as highway and railway along the slope, the hole room, tunnel and dam foundation, well, oil drilling and mining engineering and so on.and soft rock also is a complex technical problem. Traces of the tunnel blasting excavation in soft rock, especially in heterogeneous rock and tectonic development of rock, smooth blasting, on the surface, the effect is disappointing, and sometimes even the barrel of a gun could not see. Gun marks rate and other parameters evaluation of smooth blasting in soft rock tunnel, it is difficult to determine the smooth blasting is to reduce the damage to the tunnel wall rock to reduce the over and under the dig as well as to avoid cave-work. Not reasonable theoretical support for the soft rock tunnel smooth blasting quality evaluation. Therefore, soft rock tunnel smooth blasting quality evaluation study has important theoretical significance and practical significance.Hoek-Brown failure criterion based on the existing parameters of the evaluation of soft rock tunnel smooth blasting effect limitations, and to consider blasting disturbance by a large number of experimental data fitting out of practicality. In this paper, theoretical analysis, engineering applications and numerical simulations to derive the verification blasting disturbance coefficient D to evaluate the quality of soft rock tunnel smooth blasting, the main conclusions are as follows:(1) based on The Hoek-Brown failure criterion edition, presents the design stage the Geological Strength Index GSIdesign and construction stage the Geological Strength Index GSIconstruction two basic concepts, to use the design stage the Geological Strength Index and construction stage the Geological Strength Index to quantify the formula of the disturbance factor D, and put forward the GSIconstruction express Hoek-Brown rock mass strength criterion quantitative parameters formula of m、 s. When the design stage the Geological Strength Index than50index, the ordinary blasting excavation, tunnel may appear large deformation, roof caving, morphology and disasters. Along with the value reduced, along with the change of the disturbance coefficient D more and more quickly, it shows that with the geological conditions worse and worse, and surrounding rock blasting disturbance to more and more sensitive.(2) use of rock mass parameters the disturbance factor D, m and construction stage geologic intensity index to the sensitivity of the size relations were analyzed.(3) based on frequency and the joints joints surface SCR level, the paper puts forward the Geological Strength Index (GSI) classification of surrounding rock.(4) with the finite difference method, the double tablet soft rock tunnel for large-span shallow buried on the steps of smooth blasting excavation and were used respectively to routine excavation blasting the numerical model of simulation, the simulation results show that in the soft rock tunnel excavation process using smooth blasting can effectively reduce the collapsing, roof caving and large deformation occurs.