横置椭圆形砂岩隧洞裂纹扩展特征与破坏征兆研究  

Crack Propagation Characteristics and Failure Symptom of Transverse Elliptical Sandstone Tunnel

作　　者：朝文文 徐培元 张黎明[2] 王建新 张素磊[2] 王在泉[2] 丛宇[2] CHAO Wenwen;XU Peiyuan;ZHANG Liming;WANG Jianxin;ZHANG Sulei;WANG Zaiquan;CONG Yu(School of Science,Qingdao University of Technology,Qingdao 266033,Shandong,China;School of Civil Engineering,Qingdao University of Technology,Qingdao 266033,Shandong,China;National Institute of Natural Hazards,Beijing 100085,China)

机构地区：[1]青岛理工大学理学院,山东青岛266033 [2]青岛理工大学土木工程学院,山东青岛266033 [3]应急管理部国家自然灾害防治研究院,北京100085

出　　处：《隧道建设（中英文）》2023年第8期1360-1368,共9页Tunnel Construction

基　　金：山东省自然科学基金(ZR2020ME099)。

摘　　要：为研究椭圆形隧洞破坏过程及演化预警问题,开展真实砂岩横置椭圆形隧洞双轴压缩试验,结合声发射、DIC实时采集系统分析横置椭圆形隧洞裂纹渐进扩展过程特征。结果表明:1)隧洞首先在拱顶和拱底出现张拉裂纹,随后在洞口两侧出现剪切裂纹和远场裂纹,在洞口右侧壁形成V形槽,最终远场裂纹与V形槽连通导致隧洞发生脆性破坏;2)隧洞表面应变集中区先于裂纹出现,能够预判裂纹出现的位置;3)裂纹稳定扩展阶段,分形维数逐渐增大,剪切裂纹起裂时分形维数增速率加快,峰值荷载前分形维数出现突增;4)隧洞破坏前会出现声发射平静期、b值突降、熵值突增、应变场方差突增、裂纹分形维数突增等预警信息,不同物理场监测数据的预警时间不同步,预警荷载为峰值荷载的87%~97%,b值突降出现最早,应变场方差突增出现最晚。A biaxial compression test is conducted on a real sandstone transverse elliptical tunnel;moreover,the characteristics of the progressive crack propagation process of the transverse elliptical tunnel are analyzed with acoustic emission and a digital image correlation real-time acquisition system to investigate the failure process and evolution warning of the elliptical tunnel.The results show the following:(1)Tensile cracks first appear in the tunnel′s crown and bottom;subsequently,shear and far-field cracks appear on both sides of the tunnel.Furthermore,a V-shaped groove is formed on the right sidewall of the tunnel,and the far-field cracks extend to the V-shaped groove,leading to the brittle failure of the tunnel.(2)The strain concentration area on the tunnel surface appears before the crack,and the crack′s location can be predicted.(3)The fractal dimension gradually increases from zero in the stable crack propagation stage.When the tunnel shear crack starts,the growth rate of the fractal dimension accelerates.The fractal dimension shows a sudden increase before reaching the peak tunnel load.(4)At a quiet period,the sudden drop of the b value,a sudden increase in the entropy value,a sudden increase in strain field variance,and a sudden increase in the crack fractal dimension can be used as early warning information before tunnel failure.The early warning time of different physical fields′monitoring data is not synchronized,and the early warning load is 87%to 97%of the peak load.The sudden drop of the b value is the earliest and the sudden strain field variance increase is the latest.

关 键 词：横置椭圆形隧洞 裂纹扩展 声发射 DIC 分形维数 破坏预警 

分 类 号：U45[建筑科学—桥梁与隧道工程]