透水砂层泥水平衡盾构开挖面失稳破坏机理研究

发布时间：2018-01-04 03:28

本文关键词：透水砂层泥水平衡盾构开挖面失稳破坏机理研究　出处：《北京交通大学》2014年博士论文　论文类型：学位论文

【摘要】：近年来,中国地下工程进入建设高峰期,盾构法施工因其具有效率高,扰动小,在国内尤其是软土、砂土地区快速的被推广应用开来。然而,伴随着盾构法的快速发展,诸多技术问题也应运而生。其中,盾构开挖施工对周边环境影响问题就是目前困扰国内隧道工程领域专家和学者们的一项难题,尤其是大直径盾构施工,其开挖面稳定是影响周边环境的主要因素。如何确保大直径盾构施工开挖面稳定,避免施工扰动对周围环境的影响是解决城市隧道工程建设问题的关键,该问题的有效解决势必将推动未来城市隧道工程的发展。然而,关于上述问题,目前国内的研究技术水平和发展速度远逊于日本和欧美各国,尤其是透水砂层大型泥水平衡盾构开挖面失稳机理和评判计算方法的研究尚存诸多不足。本文依托于南京长江隧道工程,对高透水性砂质地层中泥水平衡盾构隧道开挖面稳定性问题展开研究,通过静三轴试验、室内模型试验、数值模拟及理论计算,系统研究了不同泥浆配比、覆土厚度、水头高度和土体性质等工况下开挖面失稳特性,对高透水性砂土地层开挖面失稳的判据进行重新界定,建立了适合于砂土地层的开挖面支护力计算公式。主要研究内容包括： (1)泥浆配比对开挖面土体强度的影响研究。泥水平衡盾构施工中,泥浆在开挖面形成的泥膜作为维持开挖面稳定的支护力传递介质,直接作用于开挖面土体,是影响开挖面稳定的关键因素之一。通过室内三轴试验,对比分析了不同围压下注浆前后土体性质和强度等变化特性。研究发现泥浆成膜过程中,会使砂土的粘聚力上升而内摩擦角降低,且随着围压升高,土体强度会有所增加； (2)开挖面主动破坏影响因素研究。通过室内模型试验,对不同泥浆配比、覆土厚度、水头高度和土体性质等工况下开挖面主动破坏的情况进行了对比研究。研究表明,覆土厚度和水头高度对开挖面的稳定性影响较大,随着覆土厚度增加,开挖面支护力逐渐增大；开挖过程中土中渗流和超孔隙水压力变化会降低开挖面稳定性；从初始开挖到失稳整个变化过程中,存在土拱效应现象,在干砂试验中这种现象越发显著。影响开挖面稳定的因素,除土拱效应作用外,更为关键的是内摩擦角、覆土厚度和水头高度； (3)泥水劈裂效应研究。在泥水盾构掘进施工过程中,泥水压力设定过高会引发泥水劈裂。从而导致泥水舱内压力急剧下降,开挖面失稳。通过室内模型试验,同样对不同泥浆配比、覆土厚度、水头高度和土体性质等工况下泥水劈裂现象进行了研究。研究表明,泥水劈裂压力与泥浆配比、水头高度和土体性质密切相关,②号泥浆的劈裂压力要明显高于①号泥浆；无水时发生劈裂需要提供的劈裂压力和时间要高于有水的情况,意味着在地层饱和时更容易发生劈裂；土体的级配、粘聚力和内摩擦角等性质直接影响泥水劈裂的效果,粉细砂的泥水劈裂压力要高于中粗砂； (4)开挖面稳定评判方法研究。传统意义上开挖面破坏主要指主被动滑动破坏。而室内模型试验研究表明,在砂土中,高泥水压力下泥水劈裂比被动滑动破坏更容易发生,因此建议开挖面被动破坏的支护力上限值应以泥浆劈裂压力为准。此外,通过理论计算,提出了适用于砂质土层开挖面失稳判断的修正稳定系数法； (5)支护力计算方法研究。通过理论计算,分析研究了目前常用的支护力计算公式,并通过实例验证了日本经验公式的适用性。此外,对透水砂层中泥水隧道掘进中开挖面支护力取值问题进行了参数分析,建立了透水砂层泥水盾构施工开挖面支护力经验计算公式,并给出了砂土地层中浅覆土隧道支护力比安全取值范围为1.38-2.14。
[Abstract]:In recent years, Chinese entered the underground engineering construction peak, shield construction due to the advantages of high efficiency, little disturbance, especially in the domestic soft soil, sandy soil area by rapid popularization and application of them. However, with the rapid development of shield technology, many problems have emerged. Among them, the shield excavation on the surrounding environment influence of construction problems is a problem plaguing the experts in the field of tunnel engineering and domestic scholars, especially the large diameter shield construction, the excavation face stability is the main factor affecting the surrounding environment. How to ensure that the large diameter shield excavation face stability, avoid the influence of construction disturbance to the surrounding environment is the key to solve the problems in the construction of city tunnel project, will to effectively solve the problem to promote future development potential of the city tunnel project. However, on these issues, the current research and the technical level of domestic development speed far less In Japan and Europe and the United States, especially the permeable sand large slurry balance shield excavation face stability calculation method and evaluation mechanism of loss exist many shortcomings. Based on the Nanjing Yangtze River tunnel project, the high permeable Sandy Stratum in slurry shield tunnel excavation face stability problem is studied through static triaxial test, three, indoor model test, numerical simulation and theoretical calculation, study different slurry ratio, soil thickness, water level and soil properties under the conditions of excavation face stability characteristics of high permeable sand soil layer excavation surface to define the failure criterion, suitable for sand soil layer excavation face support force calculation formula. The main research contents include the establishment:
(1) study on slurry ratio influence on soil strength. The excavation face of shield construction slurry, mud in the mud film excavation surface formed as maintain the stability of tunnel face supporting pressure transfer medium, directly on the soil of excavation face, is one of the key factors affecting the stability of excavation face. Through the three axis test, comparison analysis of the variation characteristics of soil properties and strength under different confining pressure before and after grouting. The study found that the mud film forming process, will make the sand cohesion and internal friction angle increases and decreases as the confining pressure increases, the strength of soil will increase;
(2) the excavation surface active damage factors. Through the indoor model test of different slurry ratio, soil thickness, the comparative study of excavation surface active destruction the head height and soil properties and other conditions. The research results show that the thickness of the overlying soil and water head height of excavation face stability is affected with soil thickness increase the excavation face support force increases gradually; during the process of excavation and seepage in pore water pressure changes will reduce the stability of the excavation face; from the initial excavation to the instability of the whole process of change, there are soil arching phenomenon, this phenomenon in the dry sand tests become more and more obvious. Influencing factors of excavation face stability, in addition to the soil arch effect, more important is the internal friction angle, soil thickness and height of water head;
(3) water splitting effect research. In the process of shield tunneling construction, slurry pressure is set too high will lead to slurry splitting. Resulting slurry cabin pressure dropped sharply, the instability of the excavated surface. Through indoor model test, the same for different slurry ratio, soil thickness, water head height and soil properties and other conditions under the water splitting phenomenon are studied. The results show that the splitting ratio of slurry pressure and mud, closely related to head height and soil properties, the number of mud fracturing pressure is significantly higher than the number of mud; splitting required fracturing pressure and time is higher than that of water occurs when water means in the formation of saturation more prone to splitting; soil gradation, cohesion and angle of internal friction properties directly affect the water splitting effect, fracturing pressure is higher than that in coarse sand slurry;
(4) study on face stability evaluation method of excavation face excavation. The traditional failure mainly refers to the active and passive sliding. The indoor model tests show that in the sand, splitting failure occurs more easily than passive sliding under the pressure of high mud slurry, therefore recommended excavation supporting upper surface passive failure stress value should be in the mud fracturing pressure shall prevail. In addition, through theoretical calculation, put forward suitable for sandy soil excavation face failure correction coefficient method to judge steady stability;
(5) supporting force calculation method. Through theoretical calculation, analysis of the current commonly used supporting force formula, and the applicability of the Japanese experience formula is verified by examples. In addition, the excavation in tunnel excavation of permeable sand bed slurry supporting force value of the parameter analysis, a shield the construction experience of excavation supporting force of slurry water branch of facial formula is given in sand soil layer shallow overburden tunnel supporting force is safer than the range of 1.38-2.14.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U455.43

【参考文献】