Prediction of Bench Blasting Vibration on Slope and Safety Threshold of Blasting Vibration Velocity to Undercrossing Tunnel

The reconstruction and expansion project of oil reserve base often faces the excavation and blasting of the slope and undercrossing tunnel at the same time. Due to the flammable and explosive liquid storage nearby, the tight construction period, and the high requirements of collaborative construction, once the blasting accident occurs, the consequences are unimaginable. To facilitate safe and timely cooperative blasting construction of the slope and undercrossing tunnel, a vibration monitoring test of the slope and tunnel surrounding rock is conducted. The vibration response characteristics of the rock surrounding the slope and tunnel are analyzed, and a mathematical prediction model for the peak particle velocity (PPV) with consideration of the influence of the relative slope gradient (H/D) is established based on dimension analysis theory, which improves the prediction accuracy of PPV at the slope surface. ANSYS/LS-DYNA is used to establish a 3D finite element model for the slope and tunnel, and the dynamic response of the tunnel surrounding rock under blasting load is verified through field monitoring data. A linear statistical relationship between PPV and effective tensile stress (ETS) of the tunnel surrounding rock is established. The PPV safety criterion of the tunnel surrounding rock under blasting load is proposed to be 10 cm/s according to the first strength theory, and hence, the minimum safety distance from the tunnel working face to the slope surface is calculated to be 36 m. Finally, the excavation timing arrangement of the slope and tunnel is proposed, which has been successfully applied to the expansion project, and the construction period has been effectively shortened by 45 days while ensuring construction safety. The research results have great guiding significance to similar cooperative blasting excavation engineering for high slope and adjacent tunnel with safety and efficiency.

Experimental and numerical investigation on destructive effect of gas pipeline buried in silty clay under surface explosion

Identifying the damage effects of buried multiple-operating-pressure gas pipelines subjected to various magnitude blasting load is a prerequisite for pipeline safety assessment. In this study, the dynamic response and damage effect are assessed by a combination of both field experiments and numerical simulation. It is indicated that the error between the numerical calculation and the field measured data is small and the reliability of the model is high. The dangerous section of the whole pipeline lies directly below the explosion source. The peak particle velocity (PPV) and the peak particle effective stress (PES) on the explosion-prone side of the section are the largest. Moreover, the PPV and PES increase with the increase of the working pressure of the pipeline. Results show that the empty pipe with no working pressure is the safest state among various pipe working state. There is a certain functional relationship among the explosive charge on the ground surface, working pressure, and PES of the pipeline.