摘要
为了揭示卸荷过程中岩体力学参数的弱化特性,研究在卸荷弱化效应下不同管棚参数对特大断面隧道超前支护的影响效果。依托重庆火凤山隧道,通过三轴加、卸荷试验得出岩石变形模量和抗剪强度卸荷弱化规律,采用FLAC^(3D)有限元软件建立了考虑围岩卸荷弱化效应的岩体力学参数动态计算模型并验证了计算模型的准确性,在此基础上通过模型试验和数值模拟,就不同管棚布设范围、间距和注浆厚度对特大断面隧道围岩变形及支护结构内力的影响开展系列研究。研究结果表明:1)岩石试样的变形模量和抗剪强度随卸荷量增大而发生不同程度的衰减,试样破坏后残余变形模量仅为峰值的8%,残余黏聚力仅为峰值的23%~32%。2)相比于摩尔库伦模型,动态弱化模型能够更准确地描述岩石破坏特性和围岩卸荷损伤发展过程。3)超前管棚支护能够显著降低围岩变形,改善支护结构内力,使拱顶沉降降低38%,围岩压力降低20%,拱顶和拱肩初支弯矩降低60%~80%。4)围岩变形和结构内力对不同管棚支护参数敏感性不同,管棚布设范围对隧道拱顶沉降影响较小,管棚间距大于40 cm,注浆厚度小于70 cm时,拱顶沉降明显增大;管棚支护能够显著降低支护结构弯矩但对轴力改善效果不明显。研究结果可为隧道围岩在开挖卸荷过程中的参数弱化及特大断面隧道超前支护提供参考。
To elucidate the weakening characteristics of rock mechanical parameters during unloading and to investigate the impacts of different pipe roof parameters on advanced support in extremely large-section tunnels under unloading weakening effects,a study was conducted based on the Huofengshan Tunnel in Chongqing.Through triaxial loading and unloading tests,the unloading weakening laws of rock deformation modulus and shear strength were established.By using the FLAC^(3D^(R))finite element software,a dynamic calculation model for rock mechanical parameters considering the unloading weakening effect of surrounding rock was developed and validated.Based on this model,a series of model tests and numerical simulations were conducted to analyze the effects of different pipe roof layout ranges,spacings,and grouting thicknesses on surrounding rock deformation and internal forces of support structures in extremely large-section tunnels.The findings reveal that:1)the deformation modulus and shear strength of rock samples undergo varying degrees of attenuation with increasing unloading.The residual deformation modulus after failure is only 8%of the peak value,and the residual cohesion is 23%to 32%of the peak;2)compared with the Mohr-Coulomb model,the dynamic weakening model provides more accurate description of rock failure characteristics and the unloading damage progression of surrounding rock;3)advanced pipe roof support significantly reduces surrounding rock deformation and improves internal forces in support structures,leading to a 38%decrease in vault settlement,a 20%reduction in surrounding rock pressure,and a 60%to 80%reduction in initial support bending moments at the vault and arch shoulders;and 4)the sensitivity of surrounding rock deformation and structural internal forces to different pipe roof support parameters varies.The pipe roof layout range has a relatively minor impact on vault settlement.When the pipe roof spacing exceeds 40 cm and the grouting thickness is less than 70 cm,vault settlement increases significantly.Pipe roof support effectively reduces bending moments in support structures but has limited improvement on axial forces.The research findings provide valuable insights into the parameter weakening of tunnel surrounding rock during excavation unloading and offer guidance for advanced support in extremely large-section tunnels.
作者
郑科
杨文波
曾文浩
方勇
姚超凡
浣宇翔
ZHENG Ke;YANG Wenbo;ZENG Wenhao;FANG Yong;YAO Chaofan;HUAN Yuxiang(Key Laboratory of Transportation Tunnel Engineering of Ministry of Education,Southwest Jiaotong University,Chengdu 610031,China)
出处
《铁道科学与工程学报》
北大核心
2025年第4期1710-1722,共13页
Journal of Railway Science and Engineering
基金
四川省杰出青年科技人才项目(2022JDJQ0018)
国家自然科学基金资助项目(52378414)。
关键词
特大断面隧道
卸荷试验
围岩参数弱化
超前支护
模型试验
super large section tunnel
unloading test
weakening of surrounding rock parameters
advanced support
model test
