既有裂缝、空洞病害隧道爆破振动安全控制标准

爆破荷载作用下，既有隧道衬砌的振动安全振速控制标准制定，大多以既有隧道完好为前提条件，不考虑病害因子对结构动力响应的影响，与实际不相符。为此，以既有新岭隧道旁拟建新隧道为工程背景，基于既有隧道衬砌裂缝和背后空洞的实际分布特征与规律，建立带裂缝与空洞的二维、三维结构模型，分析裂缝、空洞对衬砌动力响应的影响，提出以振速为指标的标准管理体系。结果表明：裂缝的最不利分布位置为迎爆侧边墙处，裂缝的存在增强了既有衬砌对S₁应力(拉应力)的响应，振速控制标准的制定应以S₁应力和裂缝径向深度为控制指标；当裂缝径向深度为(0～1/8)h、(1/8～1/2)h和＞(1/2)h（h为衬砌厚度）时，控制标准分别为12、10和8 cm/s。空洞的最不利分布位置为拱顶，空洞的存在增强了既有衬砌对S₁应力和振速的双重响应，以增强振速响应为主，振速控制标准的制定应以振速、空洞面积及纵向长度为控制指标，空洞工况下，控制标准为12 cm/s；空洞沿隧道纵向长度小于7 m时，监控范围为3～4倍纵长；空洞沿隧道纵向长度大于7 m时，监控范围为1～1.5倍纵长；纵向长度小时，倍数取大值。

Safety control standard of blasting vibration for tunnels with existing cracks and cavities

Most of safety control standard studies for existing tunnels under blasting vibrations are based on the premise that the existing tunnels are intact, and the effects of existing defects under the dynamic response are not considered. Therefore, based on the proposed new tunnel next to the Xinling tunnel as the engineering background, according to the actual distribution characteristics of tunnel defects (cracks and back-cavities), the two-dimensional and three-dimensional numerical models were established to analyze the influence of defects under structural dynamic response. Moreover, the standard management system was established. The results show that the most unfavorable distribution position of cracks is the side wall of explosion-proof which mainly increases the response of the lining structure to stress S1 (tensile stress). The control standard should take the stress S1 and the propagation depth of crack as the quantitative indicators. When the propagation depth is (0−1/8)h, (1/8−1/2)h, and ＞(1/2)h (h represents the thickness of the lining structure), the corresponding vibration velocity limit value is 12, 10, and 8 cm/s, respectively. The most unfavorable distribution position of back-cavities is at the arch crown, which increases the dual response of the lining structure to the stress S1 and the vibration velocity, and the vibration velocity response is the main one. The control standard should take the vibration velocity, plane size and longitudinal length of the cavity as the quantitative indicators. The vibration velocity limit value is 12 cm/s. When the longitudinal length of the cavity is less than 7 m, the monitoring range is 3−4 times of the longitudinal length; when the longitudinal length of the cavity is greater than 7 m, the monitoring range is 1−1.5 times of the longitudinal length; when the longitudinal length of the cavity is small, the multiple takes a large value.