广甘高速公路在建隧道余震动力响应规律研究

Research on Aftershock Dynamic Response Properties of Tunnels under Construction of Guangyuan-Gansu Expressway

以广甘高速公路施工期隧道塌方调研为依托,利用快速有限差分法对强震区软岩隧道支护及围岩的余震动力响应规律进行分析。分析结果显示:余震作用下,塌方发生次数最多、塌方量最大的位置为隧道拱肩部位,围岩主应力极值分布由静力作用下的"十"字型变为"X"型分布,隧道拱肩至拱顶位置处岩体易发生破损;隧道初支内外侧承受拉压交替作用,拱肩位置出现内力极值;当初支背后存在空洞时,围岩主应力极值分布于空洞周围,围岩塑性区显著增大,空洞位置处的初支内力急剧增大,极易发生破坏。时程分析法结果所揭示的规律与现场统计情况一致,研究结果对认识强震区软岩隧道施工中坍塌破坏机理有一定的借鉴意义。

Relying on the investigation of tunnel collapse cases happened in the under-construction GuangyuanGansu expressway and fast finite difference method,the aftershock dynamic response properties of soft rock tunnel in meizoseismal area are studied. The investigation and calculation shows that： the maximum collapse times and maximum collapse volume both appear at the position near tunnel crown,the extreme values’ distribution of ground principal stresses are changed from‘cross’ shape to‘X’shape,and the ground rock at the position near tunnel crown is shattered violently because of the dual function of static and aftershocks dynamic loads; both sides of preliminary support are under alternative action of compression and tension,the peak force of preliminary support is located at the position near tunnel crown; the cavity behind preliminary support makes the extreme values of principal stresses concentrated around the cavity and enlarges the area of plasticity remarkably and also enlarges the peak moment of support near the cavity. The research results are useful to discover the collapse mechanism of tunneling engineering construction in soft rock of meizoseismal area.