干砂和饱和砂性土中盾构开挖面稳定数值和离心试验研究

发布时间：2018-04-27 08:25

本文选题：盾构隧道 + 开挖面稳定　；参考：《浙江大学》2014年博士论文

【摘要】：为有效解决城市交通拥堵问题,越来越多的城市开始大规模兴建轨道交通。城市轨道交通的区间隧道大多采用盾构法施工,由于施工中时常遇到工程地质和水文地质状况多变、建(构)筑物及地下管线分布密集等诸多复杂条件,盾构开挖面稳定性问题日益突出。基于实际工程需求,本文对干砂地层、稳态渗流下饱和砂性土地层(如饱和砂质粉土)这两种典型复杂条件下盾构开挖面稳定性问题进行了系统深入地研究。主要工作和研究成果如下： (1)采用离散元法较为深入研究了干砂地层盾构开挖面稳定性问题。发现失稳过程中开挖面支护力随位移增大存在“先减小至极限值而后逐渐增大并趋于残余值”的现象；获得了当隧道埋深比C/D1时极限支护力受埋深比影响较小的重要结论；揭示了典型埋深下(即C/D=2)开挖面渐进失稳模式；发现了极限状态时,盾构拱顶以上失稳区内存在显著的“土拱”效应,失稳区内土体出现“松动”现象。 (2)研制了适用于模拟单相土层(如干砂)开挖面失稳的离心模型试验装置,基于该装置开展了密实干砂地层开挖面失稳离心模型试验。离心试验证实了离散元研究获得的开挖面支护力—位移变化关系的可靠性,发现了极限支护力随埋深比增大先增加而后基本保持不变的规律,借助PIV技术揭示了极限状态时开挖面前方呈现“楔形体—棱柱体”的失稳模式,获得了失稳“棱柱体”高度与隧道埋深有关的重要结论。 (3)研制了国内外首套适用于模拟稳态渗流下盾构开挖面失稳的离心模型试验装置,基于该装置开展了国内外首个稳态渗流下饱和砂质粉土地层盾构开挖面失稳离心模型试验。研究发现：稳态渗流下,开挖面失稳过程中有效支护力随位移增大存在“先减小至极限值而后线性增大”的现象；稳态渗流下开挖面极限有效支护力随密封舱与远场水头差增大而线性增大；极限状态时,开挖面前方呈现“楔形体—棱柱体”失稳模式,此时失稳“棱柱体”已经发展到地表,其高度不受隧道埋深比的影响；孔压沿开挖面向远场逐渐增大,当距开挖面水平距离大于0.75D后,孔压几乎保持不变。 (4)在本文离散元数值研究及离心模型试验的相关成果基础上,围绕失稳模式和“土拱”效应两方面对经典“楔形体—棱柱体”极限平衡模型(AnagnostouKovari1996)进行了修正,建立了适用于计算单相无粘性土层(如干砂)、单相粘性-摩擦型土层、稳态渗流时两相粘性-摩擦型土层等复杂条件下开挖面极限支护力(或极限有效支护力)的修正“楔形体—棱柱体”极限平衡模型。本文修正“楔形体—棱柱体”理论模型的准确性得到了笔者开展的离心模型试验的验证,成功应用于杭州地铁1号线九堡东站—下沙西站区间盾构工程。本文研究有助于提升行业内对复杂条件下开挖面稳定问题的认识,为实际工程中控制盾构开挖面稳定性提供参考。
[Abstract]:In order to effectively solve the problem of urban traffic congestion, more and more cities have begun to build mass transit in a large scale. Most of the interval tunnels in urban rail transit are constructed by shield method. Because of the complex engineering geology and hydrogeological conditions in the construction, many complex conditions such as construction (construction) and the dense distribution of underground pipelines are often encountered, and the shield excavation is excavated. The problem of surface stability is becoming more and more prominent. Based on the actual engineering requirements, this paper has carried out a systematic and thorough study on the stability of the shield excavation face under two typical complex conditions of dry sand stratum, saturated sandy soil layer (such as saturated sand silt) under steady state seepage.
(1) the problem of stability of shield excavation face in dry sand stratum is studied by the discrete element method. It is found that the support force of the excavation face is reduced to the limit value first and then to the residual value with the increase of the displacement in the process of instability, and the weight of the depth ratio of the limit support force is smaller when the depth ratio of the tunnel depth is C/D1. In order to find out the progressive failure mode of the excavation surface under the typical buried depth (C/D=2), there is a remarkable "soil arch" effect in the instability zone above the shield vault, and the "loosening" phenomenon occurs in the unstable zone.
(2) a centrifugal model test device is developed to simulate the instability of the excavation surface of a single phase soil (such as dry sand). Based on this device, the centrifuge model test of the excavation surface instability in dense dry sand stratum is carried out. The centrifugal test confirms the reliability of the supporting force displacement relation of the excavation face supported by the discrete element method, and finds the limit support force with the depth of the buried depth. According to the law of increasing first and then keeping the same basically, the instability mode of "wedge body prism" in front of the excavation face is revealed with the help of PIV technology, and the important conclusion that the height of unstable "prism" is related to the buried depth of tunnel is obtained.
(3) the first set of centrifuge model test device is developed to simulate the instability of the shield surface under the simulated steady state seepage. Based on this device, the centrifuge model test of the shield excavation surface of the saturated sand powder soil layer under the first steady state seepage is carried out. There is a phenomenon that the displacement increases first to the limit value and then linearly increases, and the ultimate effective support of the excavation face increases linearly with the increase of the gap between the seal and the far field, and the "wedge body" instability model is presented in front of the excavation face, and the unstable "prism" has been developed to the surface at this time. Its height is not affected by the ratio of tunnel depth to depth, and pore pressure increases gradually along the excavation face to the far field. When the horizontal distance from the excavation face is greater than 0.75D, the pore pressure almost remains unchanged.
(4) on the basis of the results of the discrete element numerical study and the centrifugal model test, the classic "wedge prism" limit equilibrium model (AnagnostouKovari1996) is modified around the instability mode and the "soil arch" effect, and a single phase cohesionless soil layer (such as dry sand) and the single phase viscous friction type are established. Under the complicated condition of steady seepage, the limit balance model of the ultimate support force (or the ultimate effective supporting force) is corrected under the complex condition of two phase viscous friction soil layer. The accuracy of this paper is verified by the centrifugal model test carried out by the pen. It is used for shield engineering of Hangzhou Metro Line 1, East Kowloon East Station and Xiasha west station.
This study is helpful to enhance the understanding of the stability of excavation face under complex conditions, and provide reference for controlling the stability of shield excavation face in practical engineering.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U455.43

【参考文献】