充填黏土型岩溶隧道大变形换拱衬砌受力研究

Research on the stress of large deformation arch-exchanging lining of filled clay-type karst tunnel

为了研究溶腔充填黏土的岩溶隧道大变形换拱后衬砌的受力特性,根据三江至柳州高速公路大塘隧道施工过程中左线(JK139+489~JK139+555)段围岩大变形换拱处置方案,采用现场测试与数值模拟的研究手段,分析了该类隧道围岩大变形情况下注浆换拱前后隧道初期支护及二衬的受力情况。结果表明:该类隧道发生大变形时拱顶部位变形最大,受力最大,拱脚处次之且局部受拉,拱腰最小,换拱后拱顶部位依然是受力最大点,拱脚受力减小;发生大变形后围岩注浆与支护时机是换拱处置方案有效性的主要影响因素,该类隧道处置应着重考虑提升围岩自身稳定性;注浆换拱后系统锚杆可起到加固围岩作用,同时隧道二衬作为主要受力结构与初期支护共同作用可减少支护结构约66%的变形,是保证隧道长久稳定的主要因素。

In order to study the mechanical characteristics of the lining of the karst tunnel filled with clay after large deformation and arch exchange,according to the disposal scheme of large deformation of surrounding rock in the(JK139+489~JK139+555)section of the left line during the construction of the Datang Tunnel of the Sanjiang-Liuzhou Expressway,based on the research methods of field test and numerical simulation,the stress of the initial support and secondary lining of the tunnel before and after grouting and arch exchanging under the large deformation of the surrounding rock of this type of tunnel was analyzed.According to the results,when the large deformation of this type of tunnel occurs,the stress and deformation at the top of the arch were the largest,followed by the foot of the arch,and local tension was applied.The force and deformation of the arch waist was minimal.After the arch was exchanged,the top of the arch still bear the greatest force,and the force of the arch foot decreased.There was large deformation,the timing of surrounding rock grouting and support became the essential factors affecting the effectiveness of the arch replacement disposal plan,and improving the stability of the surrounding rock itself should be taken into consideration when disposing of this type of tunnel.After grouting and arch change,the system bolts could reinforce the surrounding rock.Simultaneously,under the combined action of the secondary lining of the tunnel as the major stress structure and the initial support,about 66%of the deformation of the support structure could be reduced,which was the principal factor to ensure the long-term stability of the tunnel.