【作者】 周松；

【导师】 黄醒春；

【作者基本信息】 上海交通大学 ， 岩土工程， 2009， 博士

【摘要】 盾构法隧道历经180余年的发展,迄今世界各国建造了数以千计的各种类型、各种直径的盾构,我国上海、北京、广州、深圳等地成功建设了各种大型盾构,盾构施工技术水平不断提高。当随着国内外地铁等地下管网建设的迅速发展、城市地下空间开发利用模的不断扩大,盾构法施工在不断普及和高速发展的同时不断向大深度、急曲线、长距离、大直径的趋势发展。同时,近距离穿越已建地下结构情况日益增多。尤其新建隧道将不可避免面临近距离穿越运营地铁等复杂技术难题和施工风险的挑战。本研究围绕大型泥水盾构隧道近距离穿越运营地铁的关键技术与理论问题,通过室内试验、数值模拟、现场试验、原位监测及理论分析,系统研究了同步注浆浆液的物理力学性质及其对盾构施工扰动位移的影响、近距离穿越施工过程土体位移特性及施工因素的影响作用、地铁运营时列车动载条件下振动位移增量场的数值解法、近距离施工扰动状态下已建地铁隧道稳定性等。取得了相应有创新意义和工程实用价值的研究成果:(1)通过室内试验,系统研究水泥品种、水玻璃模数及其配比对盾构同步注浆浆液物理力学特性的影响。研究显示:i)高标号水泥双液浆强度和弹性模量随水玻璃模数及其配比的提高而增大;而低标号水泥双液浆强度和弹性模量对应于水玻璃配比存在一个“最佳值”;ii)低标号水泥、模数2.8水玻璃材料配制的双液浆渗透性强且固化时间长,对及时充填盾构外部空隙、减少土体损失以及减少注浆量不利。成果对盾构施工同步注浆浆液用水泥标号、水玻璃模数、材料配比等参数选择有实用指导意义。(2)考虑盾构管片结构特点及其加工精度的影响,采用接触力学理论建立了隧道结构实际有效厚度的计算方法。结果表明:管片实际有效承载厚度与极限加工误差成负指数关系;隧道结构实际总体刚度减少将对土体位移场、结构变形等产生不利影响。(3)通过合理控制盾构切口水压、同步注浆压力等施工参数可达到控制土体损失率从而有效控制在建隧道及已建隧道的变形及位移目的:i)对近邻隧道结构位移而言,土体损失率存在“最佳值”,当土体损失率大于该值时,隧道结构产生沉降,且竖向位移逐渐增大;当土体损失率小于该临界值,隧道结构将产生“上浮”。合理控制施工参数,将土体损失率控制在“最佳值”左右一定范围内即可有效控制周边隧道结构竖向位移,满足管线保护的要求。ii)隧道下行穿越施工过程中,无论土体损失率大小,上部已建隧道顶板沉降峰值均大于其底板沉降峰值,即施工扰动区域内已建隧道断面不同程度上呈“椭圆化”。iii)穿越施工过程中,上部隧道管环结构将不同程度承受拉应力,容易到成管环接缝渗漏或局部破坏。(4)针对隧道近距离穿越运营地铁时列车振动荷载与穿越施工相互影响的复杂性及其求解难度,在充分考虑系统结构特点的基础上依据力学作用效果等效原则,建立了适用于工程实际的耦合动力分析模型及分段求解方法,采用自主研发的车桥耦合数值分析软件结合ANSYS通用软件分析系统相结合方法,研究已有地铁线路运行的振动对于近距离隧道施工的动态影响。结果表明:当上部隧道正常运行状态下进行隧道下行穿越施工时,由于地铁列车振动荷载作用下穿隧道及运营地铁隧道都将产生较大的竖向振动响应位移增量。成果为西藏南路隧道施工现场采用,有效地避免了工程技术风险、确保了工程安全。(5)通过数值模拟与现场试验进一步系统深化了开挖卸载(初始土体损失率)、孔隙水压、工作面切口压力、同步注浆压力等综合因素对盾构隧道开挖扰动位移场的影响。总结出:i)同步注浆压力(注浆量)直接影响土体分层沉降(靠近盾构注浆孔区域尤为显著)及径向水平位移,而对土体轴向水平位移的影响甚微。ii)盾构工作面前方土体位移主要受切口压力支配,当切口压力小于土体压力时,工作面前方土体处于主动土压力状态从而产生向切口方向的卸载位移,土体产生与盾构推进方向相反的位移;当切口压力等于土体压力时,工作面前方土体处于静止土压力状态从而产生轻微的“顶推”位移;切口压力大于土体压力时,工作面前方土体位移进一步增大,位移方向与盾构推进方向相同。总体上,工作面前方土体位移表现出对切口压力的高度敏感性及依存性。进一步完善了该方面的理论成果。(6)进一步明确了竖平面内位移场呈非对称分布规律。即:无论同步注浆压力大小,隧道底板土体均不同程度地显示出“上浮”位移模式,即隧道底板位移具有不可逆的“上浮”特性;而隧道顶板土体的隆沉则与同步注浆压力紧密相关:当同步注浆压力P≤Ps时,顶板土体产生沉降位移;当同步注浆压力P≥Ps时,顶板土体将产生“上浮”位移。成果进一步充实了盾构施工扰动位移场理论。综上所述,本研究进一步深化与完善了大型泥水盾构近距离穿越运营地铁相关技术及理论体系。部分成果被上海世博配套工程西藏南路隧道建设工程应用,取得了良好技术经济效益和社会效益。更多还原

【Abstract】 Shield tunneling method has a history of more than 180 years and there are thousands of kinds of shields with different diameters in the world at present. In China, a variety of large-scale shields have been produced in Shanghai, Beijing, Guangzhou and Shenzhen and the technical level of shield construction improving constantly. Along with the quick development of underground pipe network construction and the expansion of city underground space, shield method is prevailing and developing at top speed, trend of which is towards high depth, sharp curve, long distance and big diameter. At the same time, more and more short-distance crossing in underground structure projects appears. Especially new tunnel construction will inevitably face the challenge of short-distance crossing of the subway tunnel which is operatingThis research focus on the key technology and theory problems of large-scale slurry shield short-distance crossing operating subway, by the means of laboratory experiment, numerical simulation, field experiment, in situ monitoring and theory analysis, systematically researched the physical and mechanical properties of synchronized grouting slurry and its influence on disturbed displacement, short-distance crossing soil displacement and effect of construction parameter, numerical solution of dynamic displacement increment field of operating subway train, stability of existed subway tunnel under short-distance crossing. Gained the innovative and engineering practical results:[1] By the means of laboratory experiment, systematically researched the influence of the type of cement, sodium silicate modulus and their mixture ratio on the physical and mechanical properties of synchronized grouting slurry. The research shows: i) the strength and elastic modulus of C-S grout with high labeling cement increased with the increase of the modulus and ratio of sodium silicate; the strength and elastic modulus of C-S grout with low labeling cement have a“best value”with the ratio of sodium silicate; ii) C-S grout with low labeling cement and 2.8 sodium silicate has high permeability and long curing time, is harmful on filling the shield void, decrease the soil loss and decrease the grouting amount. The result is instructive to the choose of the cement labeling, modulus of sodium silicate and mixture ratio.[2] Considering the influence of the character of shield segment and its producing accuracy, established the calculation method of effective thickness of tunnel structure by contact mechanics. The result showed: segment effective thickness has negative exponent relationship with ultimate machining error; the decrease of structure general rigidity do harm on the soil displacement field and structure deformation.[3] The deformation and displacement of tunnel under-construction and in-built could be effectively controlled by reasonable control on the parameter of shield cut water pressure and the synchronized grouting slurry pressure: i) to the neighboring tunnel structure, the soil loss existed a“best value”, when soil loss is above the critical value, settlement of tunnel structure occurred, and the vertical displacement increased gradually; when soil loss is under the critical value, uplift of tunnel structure occurred. Surrounding structure vertical displacement could be effectively controlled by controlling the parameter to make the soil loss at the“best value”. ii) During the construction of downline tunnel, no matter the value of soil loss, the roof settlement of upper existed tunnel is always big than floor settlement, which means the existed tunnel section turned“elliptical change”. iii) During the crossing, upper tunnel segment beared tensile stress in different degree, which could cause leak of seam and local failure.[4] Aim at the complex and solution difficulty of coupling of crossing construction and operating subway train vibration during short-distance crossing, seriously considered the system structure character, based on the equivalent principle of mechanism, established a proper coupling dynamic model and segmentation solution method, adopted independently developed vehicle-bridge coupling numerical analysis software and ANSYS, researched dynamic influence of operating subway vibration on the short-distance tunnel construction. Result showed: During the lower tunnel crossing construction when upper tunnel was normal operating, because of the subway train vibration, the tunnel under construction and in-built both had large vertical vibration responding displacement increment. The result is adopted in the South Xizang Road tunnel construction, effectively avoided engineering risk, made sure the engineering safety.[5] By means of numerical simulation and field experiment, further systematically deepen the influence of excavation unloading (initial soil loss), pore water pressure, work face cut pressure and synchronized grouting pressure on the disturbed displacement field of shield tunnel excavation. Giving the summary: I) Synchronized grouting pressure (grouting amount) directly affected the soil layered settlement (especially the zone near grouting hole) and radial horizontal displacement, and had little influence on the soil axial horizontal displacement. II) The soil displacement before the working face was mainly affected by cut pressure, when cut pressure was smaller than the earth pressure, the soil before the working face was under active earth pressure, so occurred unloading displacement towards the working face, soil had opposite direction displacement with shield advancing; when cut pressure was equal to the earth pressure, the soil before working face was under earth pressure at rest, so occurred slight“push”displacement; when cut pressure was bigger than the earth pressure, the soil displacement before the working face increased further, direction was the same with the shield advancing. As a whole, soil displacement before working face showed out highly sensitivity and dependency on cut pressure. Further perfected theory results on this field. [6] Further clarified unsymmetry of vertical displacement field. That is: no matter the magnitude of synchronized grouting pressure, tunnel floor soil all showed“uplift”, which means tunnel floor had irreversible“uplift”character; and the uplift or settlement of the proof was closely related to the grouting pressure: when synchronized grouting pressure P≤Ps, proof soil showed settlement; when synchronized grouting pressure P≥Ps, proof soil showed“uplift”. The result further fulfilled the disturbed displacement filed of shield construction.In summary, this research further deepened and perfected related technology and theory of large-scale slurry shield short-distance crossing operating subway. Part of the achievements was adopted in 2010 Shanghai Expo matching project South Xizang Road tunnel, acquired fine technology economy benefit and social benefit.更多还原