央达隧道掌子面前方边坡地表开裂研究

Study on ground fracturing of the slope in front of heading face of Yangda tunnel

隧道开挖引起掌子面前方边坡离掌子面水平距离超过5倍隧道断面尺寸的地方地表开裂问题是急需解决的课题。将广西央达隧道开挖引起掌子面前方边坡开裂问题作为工程实例,采用地质勘察和边坡监测手段开展研究,并建议了一个基于有限差分软件FLAC^(3D)遍布节理模型的分析模型进行分析,该分析模型利用有限差分软件FLAC^(3D)遍布节理模型和反演技术分析考虑优势节理影响的隧道开挖的边坡响应,重点分析塑性屈服区分布特征。工程勘察研究结果表明优势节理J1倾向与滑动条带主滑方向基本一致;边坡监测研究结果给出了主滑段最大埋深大约为15~18 m和采取边坡加固措施后的边坡滑移范围;数值模拟结果主滑段埋深与监测结果的估计深度接近,边坡后缘裂缝两端点直线段长度为63 m,与裂纹实际长度接近,裂缝端点与隧道掌子面之间距离为99 m,与实际距离90 m接近。分析结果表明,本研究建议的分析模型合理可行,且对类似工程具有借鉴意义。

The ground fracturing of slope in front of the tunnel face,whose horizontal distance exceeds 5 times of the tunnel section size from the tunnel face,has become an urgent issue.To address this issue,the ground fracturing of slope in front of heading face of Yangda tunnel in Guangxi caused by the tunnel excavation was studied by means of geological exploration and slope monitoring as a project example,and the following simulation model of the finite difference software FLAC^(3D)based on ubiquitous-joint model was suggested to simulate the ground fracturing.The response of the slope caused by tunnel excavation considering the influence of dominant joints was calculated with the finite difference software FLAC^(3D)based on ubiquitous-joint model and the inverse technique,and the distribution characteristics of plastic zone was laid special stress on.The results from geological exploration showed that the dip direction of the dominant joint J1 was almost the same as the slip direction of main sliding body.The results from slope monitoring showed that the maximum buried depth of main sliding body was from 15 m to 18 m and the slope sliding area after slope reinforcement was given.The results from numerical simulation showed that the maximum buried depth of main sliding body was close to that from slope monitoring results,the 63 m linear length between the two ends of the top fracture of the slope was close to that of the actual fracture,and the distance from one of the ends of the top fracture to one of the heading faces,99 m,was close to the actual distance 90 m.The results indicate that the suggested simulation model is feasible and available and it can be referred for similar engineering.