Theoretical Analysis of the Solidification of Aluminum Alloy Billet in Air-Slip DC Mold

Based on the heat transfer analysis of Air-Slip DC mold, a numerical model was presented to study the quantitative relationships between critical solidification layer and casting rate, pouring temperature and mold cooling ability etc. The analytical results show that the Air-Slip mold heat transfer condition plays important roles on choices of a casting rate and the pouring temperature, and that the product of billet diameter and casting rate is a certain constant under a certain condition of the mold.     

新建隧道下穿既有隧道减震孔减震效果试验研究

爆破振动作为隧道近接施工的主要危害之一,如何有效减小其带来的不利影响对施工来说尤为重要。因此,为新建隧道正式下穿既有运营隧道爆破施工提供理论及技术支撑,在新建隧道试验段上方进行仿真模拟试验,对拟采取“控制爆破”工法与“预设减震孔+控制爆破”工法进行6组代表性对比试验,对爆破振速和下穿段爆破影响开展分析研究。研究得出：减震孔减震效率与爆心距有关联影响,表现为减震效果随着爆源与试验井的距离的减小而逐渐增大;采用“控制爆破”工法的实测振速和偏差幅度总是要大于采用“预设减震孔+控制爆破”工法;“预设减震孔+控制爆破”工法相对于“控制爆破”所需工时较长;试验井收敛变形累计值和沉降变形累计值均在可控范围之内,通过试验研究为正下穿段施工提供了科学依据和技术支撑。