应力释放率对超大断面小净距浅埋隧道的开挖影响研究

Effects of stress release rate on the excavation of large sections of small spacing shallow tunnel

依托某高速公路隧道工程,基于空间反向荷载法和CRD施工工法,分析了不同应力释放率下浅埋隧道围岩变形及地表沉降规律。得出以下结论:(1)随着应力释放率的增大,浅埋隧道洞周竖向位移及地表沉降明显增大,围岩塑性区范围也明显增大;(2)在小净距浅埋隧道变形计算中,应力释放率越小,左、右幅隧道开挖引起地表相对干扰越大。当应力释放率取50%时,左洞隧道开挖引起的右洞地表隆起值大于其自身开挖引起的位移值,右洞上部地表隆起,最终导致隧道上方公路可能出现拉裂现象。

To study the effects of stress releasing rate on the excavation of large sections of small spacing shallow tunnel, based on the spatial reverse load method and CRD construction method, the deformation of surrounding rock and the surface settlement of shallow tunnel are analyzed under different stress releasing rates for the project of Dali-Binchuan Austin tunnel. The results show that with the increase of the stress releasing rate, the vertical displacement and the surface settlement of the shallow tunnel sharply increase. And the plastic zone of surrounding rock also increases significantly. The smaller the stress releasing rate is, the bigger the disturbances between left and right are. When the rate is 50%, the uplift values of right surface from the excavation of left tunnel are bigger than the settlement result from excavation itself, the surface of right tunnel has been uplifted. Finally, cracking phenomenon may occur along the road above the tunnel.