Research And Application Of Smooth Blasting Technology In Huanglian Mountain Tunnel Of Shanghai - Kunming High - Speed Railway

The smooth blasting is an control blasting technology, which is drilled some Small spacing of smooth blasting holes around the excavation contour line in the rock, then is initiated the smooth blasting holes with charge structure which there is a air layer between explosive and rock, at last the rock between the nearly two surround holes is got though and form a smooth surface.Huang-lian mountains tunnel is a shallow buried and large cross section tunnel of the high-speed double line railway, whose geological conditions of surrounding rock is complex, stability is poor and quality requirement is high. If we slect the normal blasting method, It is easy to appear the phenomenon of falingl out of surrounding rock, roof caving or hoard of collapse,which brings great difficulties and the safe trouble for tunneling.First,the author have a visit to construction site to survey the the basic situation such as geological conditions, blasting environment and engineering requirement and so on.Then treat the hole spacing, smooth blasting layer thickness and explosive payload as the main factors of influencing smooth blasting, and select three parameters for each factor in the reasonable range. Combining of nine orthogonal experiment scheme with orthogonal experiment method,then having a test for every scheme, collecting and having a comprehensive evaluation for every scheme, treating half hole rate, quantity of over-break and residual depth of the hole as the evaluation index, using the Multi-objective grey situation decision method to select the most reasonable scheme from the nine smooth blasting scheme, whose around the hole spacing is50cm, smooth blasting layer thickness is60cm and explosive payload is0.27kg per meter.Finally, having a numerical modeling for the smooth blasting scheme with ANSYS/LS-DYNA finite element software. Choosing two around holes from the light bursting layer to make the model and having numerical calculation, analyzing the propagation process of equivalent stress, having a equivalent stress analysis for the specific unit of adjacent two peripheral holes on mid-perpendicular. The results of numerical simulation is similar with the field test results. Smooth blasting scheme has been put into engineering application, and have achieved satisfactory blasting effect. According to the Blasting effect data of the quality inspection department, the average quantity of overbreak is from6-10cm, the largest quantity of overbreak is within15cm, half hole rate is about75%, hole utilization is about95%, vault subsidence and arch wall level convergence is stability.The scheme can guarantee the engineering quality of Huang lian mountains tunnel, provide a safe environment for the workor of the tunnel construction.