Determination of blast-induced dynamic soil response using axisymmetric boundary elements.

摘要

An engineering investigation into the effects of construction blasting and its response on both surface and in situ structures is presented. Specifically, the effects of construction blasting are examined as they pertain to surface wave (i.e., Rayleigh wave) propagation. Due to the nature of typical construction-type blasts routinely encountered within the civil engineering discipline, Rayleigh wave production is the dominant factor affecting surface structures (e.g., houses, bridges, etc.), as well as subterranean structures such as pipelines and tunnels.; A detailed field survey of a roller-compacted concrete dam site was undertaken to quantify the blast response characteristics in both the time and frequency domains. The results of actual excavating blasts were examined with respect to overall charge weight, delay ratios, measurement distance, and relative degree of confinement for the purposes of determining the degree of surface (Rayleigh) wave production. Field measurements performed for a variety of source-receiver points were examined for their variation in Rayleigh wave levels and frequency content, and were compared (where possible) to earlier published results for predicted ground vibration levels.; Given the background field data obtained, a computationally efficient solution strategy for the prediction of blast-induced ground motion was developed using the Boundary Element Method. The computational model developed was compared to classical approaches utilized in the construction industry for the prediction of blast-induced ground motion (and subsequent damage prediction). The clear advantages of this new approach are in its ability to capture the actual physics of the problem as well as providing an insight into the effects of blast-frequency on the actual observed response. The developed boundary element provides the necessary nexus between the classical theory and the empirical response characteristics.; This new analytical approach updates the older, simpler prediction methods currently employed, thus enabling practicing engineers and blasters to more accurately predict the ground motion profile and the effects on structures with a higher level of confidence. It is anticipated that these methods will ultimately be adopted by the blasting industry and standardized as a first-line prediction method by the practicing field engineer.