【作者】 岳健；

【导师】 冷伍明；

【作者基本信息】 中南大学 ， 交通运输工程， 2012， 博士

【摘要】 穿越城市江河的水下隧道若采用“浅埋+小净距”的形式,既易于满足坡度设置的要求,又便于连接两岸的既有道路和节约用地,有着广阔的应用前景,但目前我国用浅埋暗挖法修建的水下小净距交通隧道还很少。本文以长沙市浏阳河公路隧道为工程背景,通过现场测试、室内试验、解析计算和数值模拟,研究浅埋暗挖法修建水下小净距软岩隧道的力学行为和关键技术。主要工作和成果如下：(1)在施工现场详细记录了工作面的推进情况、掌子面的围岩状况和隧道的渗水情况,获取了丰富的第一手资料以利于阐述问题和验证研究结果。(2)开展了深入细致的现场测试与分析：自制了土压力盒安装器,给出了详细的测试元件埋设方法和保护措施；分析了河道水位、地表沉降、初衬的拱顶沉降和水平收敛、初衬背后的水压力、围岩与初衬间的接触压力、锚杆轴力、型钢拱架应力、二衬混凝土应力等测试指标的变化特点；分析了开挖下台阶、全环封闭初衬、挖掉仰拱初衬上的临时填土、灌注仰拱二衬混凝土、灌注拱墙二衬混凝土、移走二衬台车等施工环节对衬护力学性态的影响；分析了地下水渗流路径在施工过程中的变化情况；总结了水下双洞并行施工相互影响力学行为的特点。根据现场测试结果,认为可以采用“折减系数法”计算施作二衬以前的初衬背后水压力,提出了折减系数的确定方法。(3)针对浏阳河隧道采用台阶法施工,在下台阶开挖后未必能及时施作初期支护的情况,推导出了“上半断面存在支护力、下半断面无支护力”、河水水位上升情况下的水下浅埋隧道围岩附加应力的计算表达式。(4)通过建立考虑渗流的数值模型,计算分析了水下浅埋暗挖小净距并行双洞的河床沉降、初衬拱顶沉降、初衬主应力和水压力等,分析了河水水位变化对双洞初衬拱顶沉降的影响。对比分析了数值模拟结果和现场测试结果。(5)研究了水下浅埋暗挖强风化砾岩隧道超前加固技术及相关理论问题：介绍了联合超前支护技术方案,讨论了止浆岩柱和孔口管存在的问题；对比分析了TSP超前地质探测结果和施作联合超前支护后开挖揭露的实际围岩状况；分析了注浆浆液在强风化砾岩中的作用机制,分析了联合超前支护作用下围岩横向承载拱的形成机制；通过室内试验,对比分析了三种浆液和强风化砾岩的力学性质、施作联合超前支护前后的岩样波速；给出了联合超前支护作用下的上台阶爆破技术方案；通过现场测试和数值模拟,分析了拱部锚杆在应用联合超前支护后的功效；考虑渗流的影响,对比分析了无任何超前支护措施、只有全断面超前预注浆、联合超前支护三种情况下初衬的受力变形,并结合现场测试结果,分析了联合超前支护对初衬受力性状的影响；研究了应用联合超前支护后拱墙二衬的合理施作时机。(6)研究了水下浅埋暗挖小净距隧道贯通技术及相关理论问题：针对浏阳河隧道相向施工、双线四洞将在河底两两贯通的情况,建立考虑渗流影响的三维数值模型,计算分析贯通处两侧初衬的拱顶沉降、先到达贯通处的初衬的应力、先到达贯通处的洞室的掌子面纵向位移、贯通处岩柱的应力、贯通区域的河床沉降和中夹岩的竖向应力等,揭示了围岩和初衬在贯通过程中的力学特征,给出相应的贯通技术措施,现场观察和现场实测均表明贯通效果较好,证明了计算结果的参考价值。(7)研究了水下浅埋暗挖隧道二衬防水技术及相关理论问题：通过在施工期间和运营期间的长期现场调查,分析了仰拱防水板的作用机制和“全包全封闭”二衬防水技术的应用效果；计算了防水型二衬在隧道长期运营后所受的水压力和土压力；通过计算对比,揭示了施工期间不处理隧底虚渣对长期运营后防水型二衬受力性状的恶化效应,并提出了相应的工程措施。更多还原

【Abstract】 The shallow embedded underwater traffic tunnels with small spacing have wide application prospect in crossing the river in the city, because they can accord with the setting slope easily, link the existing roads on the banks conveniently and save land significantly, but they are seldom built by the shallow mining method in our country. Taking the Liuyanghe highway tunnel in Changsha as project background, the construction mechanical behaviors and key technologies of the underwater soft rock tunnels with small spacing by the shallow mining method were researched by field test, indoor test, analytical calculation and numerical simulation. Following are research process and main achievements:(1)At the construction site, the real-time positions of the working faces, the surrounding rock condition of the driving faces and the situation of water leakage were recorded in detail as the firsthand informations, which was helpful to describe the problems and verify the research results.(2)The instrument for fixing the earth pressure cell was designed. The installing methods and the protection measures of the testing elements were given in detail. The changing characteristics of the testing indexes were analysed, including water level, ground surface settlement, crown settlement, convergence, water pressure behind initial lining, contact pressure between surrounding rock and initial lining, axial force of anchor, stress of section steel frame and secondary lining. The construction links effects on the lining mechanics character were studied, including excavating the lower bench, closing the initial lining layer, digging out the temporary fill on the initial lining, moving the lining trolley, constructing the invert secondary lining and the arch wall secondary lining. The change of the ground water seepage path during the period of construction was analysed. The mechanics characteristics of the constructing interaction of the underwater twin caves were studied. According to the result of the field test, before constructing the secondary lining, the water pressure behind the initial lining could be calculated by the discount coefficient method, and the determination method of the discount coefficient was put forward. (3)The bench cut method was used in the Liuyanghe tunnel, when the primary support constructing was delayed after excavating the lower bench, the supporting force existed only on the upper semi-section, and unluckily, the river water level was increased at the same time. According to this situation, the calculation expression of the surrounding rock additional stress of the shallow underwater tunnel was obtained by the formula derivation.(4)By using the seepage numerical model of the underwater twin caves with small spacing by the shallow mining method, riverbed settlement, water pressure, crown settlement and principal stress of initial lining were calculated and analysed, the effect of the change of the water level on crown settlement of initial lining was studied also. The comparative analysis was carried out between the numerical simulation results and the field test results.(5)The combined advanced support technology scheme was given and applied in the strong weathering conglomerate underwater tunnel by the shallow mining method. The problems about the preventing-grout wall and the borehole orifice-pipe were discussed. The surrounding rock conditions obtained by TSP advanced geological exploration and observing after constructing the combined advanced support and excavating were compared to each other. The action mechanism of the slurry into the strong weathering conglomerate was analysed, and the forming mechanism of the surrounding rock lateral load-bearing arch under the action of the combined advanced support was studied. By the indoor test, the comparative analysis on the mechanical property was carried out among the three kinds of the slurries and the strong weathering conglomerate, and the rock sample velocity under the action of the combined advanced support was studied. The technical scheme of the blasting excavation of the upper bench was determined considering the action of the combined advanced support. By the field test and the numerical simulation, the efficacy of the arch anchor bolt under the action of the combined advanced support was studied and the related design scheme was optimized. Considering the effect of seepage, the comparative analysis on the mechanics character of the initial lining was carried out among no applying the advanced support, applying the full-sectional grouting only and the combined advanced support, the effect of the combined advanced support on the mechanics character of the initial lining was studied also by the field test. The proper construction time of the arch wall secondary lining was determined considering the action of the combined advanced support.(6)The Liuyanghe tunnel included two lines and four caves, they would transfix respectively under the river. According to the condition, the three-dimensional numerical model considering seepage was established. By analysing crown settlement and principal stress of initial lining, longitudinal displacement and principal stress of surrounding rock, riverbed settlement and vertical stress of interlaid rock in the transfixion zone, the mechanics characters of the surrounding rock and the initial lining during transfixion were revealed, and the corresponding transfixion scheme and measures were put forward and applied in practice. The field survey and test showed that the transfixion effect was good, which proved that the numerical simulation results had reference value.(7)By the longtime field investigation during the period of construction and operation, the action mechanism of the invert waterproof board and the application effect of the whole enwraped and closed waterproof technology were analysed. The water pressure and the earth pressure of the waterproof secondary lining after the longtime operation were calculated. The integral invert secondary lining was applied in the soft rock underwater tunnel by the shallow mining method, sometimes the bottom residue was not treated during the period of construction, which would bring a harmful effect on the mechanical performance of the waterproof secondary lining after the longtime operation, the harmful effect was revealed by the comparative calculation, and the corresponding measures were put forward.更多还原