【作者】 王汉鹏；

【导师】 李术才；

【作者基本信息】 山东大学 ， 工程力学， 2007， 博士

【摘要】 由于地形条件的限制和减少工程造价的考虑，正在施工建设的沪蓉西高速公路八字岭隧道出口采用分岔式形式。分岔隧道由大拱段、连拱段、小净距段和分离段组成，设计、施工都比较复杂，本文分别采用理论分析、模型试验、数值计算的方法研究了分岔隧道设计施工中的关键技术。并采用现场监测数据进行了对比分析，证明了研究结果的正确性。建立了隧道中墙的承载模型，针对连拱隧道的混凝土中墙和小净距隧道的岩体中墙，分别给出了中墙的极限强度表达式，最后给出了中墙的失稳判据。研究了小净距隧道中间岩墙的支护措施，当中墙埋深一定时，可以通过加固措施提高中墙的C，φ值，采用预应力贯穿锚杆增加中墙的侧向力等加固措施增加中墙的强度。应用新型地质力学模型试验台和IBSCM相似材料对分岔隧道这种新型的隧道结构进行了研究。共做了2个模型，分别研究了分岔隧道大拱段—连拱段和连拱段—小净距段的施工全过程及其在施工过程中的受力、变形、破坏形态和模型2的超载安全度。试验结果表明，大拱段和连拱段开挖位移不大，拱顶只有4mm左右，连拱段和小间距段的最终位移为4.5-6mm之间，水平位移都较小。中墙内的压应力集中，约为6.5MPa。大拱段和连拱段过渡处最危险，连拱中墙承受较大的压力，且中墙上部产生拉应力。模型2的拱项、拱腰和中墙是隧道较易发生破坏的区域，靠近连拱段的小净距段较为危险。隧道超载安全度为3.5。采用损伤与弹塑性耦合的方法，根据不可逆热力学原理，推导出了损伤软化破坏理论，并用VISUAL FORTRAN6.5编制了大型三维损伤弹塑性有限元D-FEM程序。它能模拟岩土工程的开挖、回填等施工过程，且具有求解速度快、群组功能、材料模型多等特点。并采用FLAC3D进行了验证，结果表明考虑岩体损伤软化后的D-FEM有限元程序计算结果更加符合岩体破坏的真实特点。应用损伤弹塑性有限元D-FEM程序分别研究了分岔隧道连拱段直中墙、连拱段曲中墙和小净距段中墙的合理取值，研究了不同围岩类别、不同埋深对中墙宽度的影响，并对分岔隧道的施工工序进行了优化。通过分析得出如下结论：(1)直中墙隧道的稳定性比曲中墙隧道要好，连拱段隧道中墙形式易采用整体式直中墙形式。(2)八字岭分岔隧道采用左洞超前32m，左右洞同步开挖的施工工序比较合理。提出了分岔隧道整体线型优化设计的最优化模型。根据此模型，可以得出最经济的线型。分析了分岔隧道的支护措施，并针对八字岭分岔隧道原设计提出了建议。现场监测了分岔隧道大拱段、连拱段和小净距段等不同断面的位移、锚杆内力、钢结构内力、二次衬砌内力、中墙压力及围岩松动圈的大小。现场监测的结果与模型试验和数值计算的结果对比证明了模型试验和数值计算的正确性。更多还原

【Abstract】 Forked tunnel is selected to construct in Hurongxi highway Baziling tunnel because of landform condition limit and in order to reduce project cost. Forked tunnel is composed of large-arch tunnel, multi-arch tunnel, neighborhood tunnel and separated runnel, whose design and construction is complex also. In this paper, the key technology in design and construction of forked tunnel is researched by theory analysis, geo-mechanical model test and numerical simulation methods. In the end the research results are contrasted and validate by in-situ monitor results.Tunnel middle wall bearing weight model is set up, the middle wall limit intensity is proposed according to concrete middle wall of multi-arch tunnel and rock middle wall of neighborhood tunnel, and middle wall stability criterion is presented. The support measure of neighborhood tunnel middle wall is researched, when tunnel depth is constant, the neighborhood tunnel middle wall can be reinforced by enhancing its c,φvalue and increasing side force by pre-stress through bolts.Forked tunnel is researched by geo-mechanical model test using new type test-bed and new type analogy material IBSCM. Two models are researched, model 1 is from large-arch section tunnel to multi-arch section tunnel, model 2 is from multi-arch section tunnel to neighborhood section tunnel. Tunnel surrounding rock stress, displacement, failure are analyzed in construction process and overloading safety of model 2 is also studied. The model test results show that vault displacement of large-arch section and multi-arch section tunnel is 4mm, vault displacement of multi-arch section and neighborhood section tunnel is 4.5-6.0mm, horizontal displacement is small. Stress in middle wall is 6.5MPa. The transition of large-arch section and multi-arch section tunnel is not safe, model 2 shows that surrounding rock in vault, hance and middle wall is easy to damage, neighborhood section tunnel near multi-arch section tunnel is damaged worse. The tunnel overloading safety degree is 3.5.Using damage and elasto-plastic coupling method, according to irreversible thermodynamics principle, the damage softening failure theory is presented. The large 3-D damage elasto-plastic finite element code D-FEM is programmed using FORTRAN langue. D-FEM can simulate geotechnical construction process including excavation, backfill and it has quickly solving, group function and many material models. Comparing with FLAC^3D, D-FEM can simulate rock mass failure really considering damage strain softening. The reasonable width of multi-arch tunnel straight and bend middle wall and neighborhood tunnel middle wall are researched respectively by D-FEM. The influence of different surrounding rock type and different tunnel depth to middle wall is considered, construction sequence of forked tunnel is also optimized. The conclusion is drew as follows: （1） straight middle wall is more stable then bend middle wall, straight middle wall should be used in multi-arch tunnel. （2） The construction sequence of lift tunnel 32m ahead and lift and right tunnels excavation in-phase should be adopted in Baziling forked tunnel.Forked tunnel whole line type design optimization model is presented. We can get most economical line type according to this model. Support measure of forked tunnel is also presented, according to original design of Baziling forked tunnel, the rational advice is presented.In different sections including large-arch tunnel, multi-arch tunnel and neighborhood tunnel, displacement, bolts stress, steel structure stress, lining stress, middle wall pressure and released zone are measured. The model test and numerical result is correct by contrast with monitor result.更多还原