水工隧洞光面爆破超欠挖影响因素数值模拟分析

Numerical Simulation Analysis of Influencing Factors of Overbreak and Underbreak in Smooth Blasting of Hydraulic Tunnels

摘要: 针对引水隧洞光面爆破超欠挖控制问题，以引江补汉工程12-1#平洞IV级围岩段为背景，采用ANSYS/LS-DYNA建立隧洞周边孔爆破数值模型，以总超挖面积和最大超挖值为评价指标，研究周边孔间距和光爆层厚度对超欠挖的影响规律，在单因素数值模拟的基础上，开展3 × 3全因子数值试验，并采用极差分析比较周边孔间距和光爆层厚度对不同评价指标的影响程度。结果表明：增大周边孔间距和光爆层厚度总体有利于减小超挖，但两者均存在合理范围。周边孔间距增大可减弱相邻炮孔应力叠加，降低轮廓附近岩体损伤；间距过大时，孔间裂纹贯通不足，易引起欠挖和轮廓不平整。光爆层厚度增大可抑制自由面反射拉伸作用，缩小高损伤区；厚度过大则会削弱裂纹贯通能力，增加局部欠挖风险。总体上，周边孔间距对总超挖面积影响较明显，光爆层厚度对最大超挖值影响较明显。工程中应综合超欠挖控制和轮廓成形要求，合理匹配这两项参数，为类似水工隧洞光面爆破参数设计提供参考。

Abstract: Aiming at the control of overbreak and underbreak in smooth blasting of diversion tunnels, the Class IV surrounding rock section of the 12-1# adit of the Yangtze-to-Hanjiang Water Diversion Project is taken as the research background. ANSYS/LS-DYNA is used to establish a numerical model for blasting of tunnel perimeter holes. Taking the total overbreak area and maximum overbreak value as evaluation indices, the influence laws of perimeter hole spacing and the thickness of smooth blasting layer on overbreak and underbreak are investigated. On the basis of single-factor numerical simulation, 3 × 3 full-factor numerical tests are carried out, and range analysis is adopted to compare the influence degrees of perimeter hole spacing and smooth blasting layer thickness on different evaluation indices. The results show that increasing the perimeter hole spacing and smooth blasting layer thickness is generally beneficial for reducing overbreak, while both parameters have a reasonable range. Increasing perimeter hole spacing can weaken the stress superposition of adjacent blast holes and reduce rock mass damage near the tunnel contour. Excessively large spacing results in insufficient crack penetration between holes, which easily causes underbreak and uneven contour. Increasing the thickness of the smooth blasting layer can restrain the reflected tensile effect of the free surface and shrink the high damage zone. Nevertheless, excessive thickness weakens crack penetration capacity and increases the risk of local underbreak. In general, perimeter hole spacing has a prominent effect on the total overbreak area, and the thickness of the smooth blasting layer exerts a significant influence on the maximum overbreak value. In engineering practice, the two parameters should be reasonably matched with comprehensive consideration of the requirements of overbreak-underbreak control and contour formation. This study can provide references for the parameter design of smooth blasting of similar hydraulic tunnels.