音频大地电磁法(AMT)在贵州省余遵高速公路路基勘察方面的应用

余庆至遵义高速公路位于贵州省东北部,地形切割大、地质结构复杂,利用常规方法进行定测勘察,费时费力、成本高、工期长、效果一般,后选用音频大地电磁法(AMT)和钻探相结合的方法,物探结果和钻孔岩性相互对比,相互验证,以点带线,提高了工作效率,降低了勘察成本,并且物探成果可以指导钻探施工,为隧道掘进提供超前预报。该方法在该区取得了较好的效果,通过总结方法的优缺点,可以将该方法在相似区域进行推广应用。     

隧道施工断面快速测量方法

在隧道施工断面测量过程中,在最小投入的前提下,采用极坐标法能够及时为施工提供可靠的测量数据,准确地指导断面施工。而三维坐标段落法,只需测量任意点的三维坐标即可计算其偏差,全面地反映整个段落任意桩号各个点的超欠挖情况。     

南京长江隧道三维测控系统设计

越江隧道精准化、信息化施工的基础是必须建立一套高可靠度、高精度的三维测控系统以及与之配套的科学观测程序。长江越江隧道三维测控系统如何构建是测绘界极有挑战性的一个课题,以南京长江越江隧道为例,介绍了长江越江隧道三维测控系统设计的基本方法,以及与之配套的科学观测程序。     

The deformation of overburden soil induced by thrust faulting and its impact on underground tunnels

Overburden soil beds situated above a fault are often deformed by propagation of bedrock thrusting from the fault during large earthquake. The deformed beds formed a triangular shear zone. This coseismic faulting often causes damage to underground tunnels located in the shear zone. The present research studies the deformation behavior of the overburden soil beds and the tunnel, the associated mechanism and the impact on the safety of tunnel linings induced by a large blind thrust slip. Based on sandbox experimental and numerical studies, it is found that results from numerical analysis are in agreement with the sandbox model tests with regard to growths of the shear zones within the soil beds, location of the tunnel in this shear zone and deformations of the tunnel. The potential major shear zone may be bent or bifurcated into two sub-shear zones owing to existence of a tunnel inside the shear zone. Furthermore, the occurrence of back-thrust faulting will threaten the safety of nearby structures. It was also identified that stiffness of the soil and the fault dip angles are among the major factors controlling the configuration of shear zones, the stresses within the soil, and the loads on tunnel linings. Based on the identified mechanisms, the strategies for hazard prevention are accordingly suggested and discussed.     

Dynamic response of a piecewise circular tunnel embedded in a poroelastic medium

Recently, considerable efforts have been devoted to evaluation of seismic dynamic response of a circular tunnel. Conventional approaches have considered integral liners embedded in an elastic medium. In this study, we re-examine the problem with piecewise liners embedded in a porous medium. Surrounding saturated porous medium of tunnels is described by Biot's poroelastic theory, while the liner pieces and the connecting joints are treated as curved beams and characterized by curved beam theories. The scattered wave field in the porous medium is obtained by the wave function expansion method. The differential equations governing the vibration of a curved beam is discretized by the General Differential Quadrature (GDQ) method. The domain decomposition method is used to establish the global discrete dynamic equations for the piecewise tunnel. The surrounding soil and the tunnel are coupled together via the stress and the displacement continuation conditions which are implemented by the boundary collocation method. Numerical results demonstrate that the stiffness difference between the liner piece and the connecting joints has a considerable influence on the internal forces of the liner piece.     

二郎山公路隧道泥石流地质灾害及防治

1997年7月3日及8月15日暴雨期间，川藏公路二郎山隧道东口龙胆溪、西口和平沟暴发2次灾害性泥石流，造成隧道施工设施被毁、人员伤亡。泥石流形成机制、活动规律、演化趋势及相应防治措施的研究，对确保隧道施工及安全运行具有重要意义。论文以和平沟泥石流为例，在研究泥石流形成条件、活动特征基础上，分析了泥石流的形成机制及其造成巨大危害的原因，预测了泥石流的发展趋势，据此提出以排导工程为主，排导与拦挡工程相结合，工程措施与生物措施相结合的综合防治对策。研究表明，在山区公路隧道建设中泥石流的防治，必须建立在对地质灾害发育、分布、活动规律、形成演化机制及其危害性认识的基础上，这样才能在隧道选址、施工设计时，制订相宜、合理的防治对策。     

隧道下穿既有结构物引起的地表沉降控制标准研究

解决好隧道下穿既有结构物引起的地表沉降问题,对城市地下交通和高速铁路的建设具有重要的意义.在调研国内大量隧道下穿开挖引起的地表沉降控制标准和方法的基础上,根据隧道下穿公路、铁路、隧道和建筑物时引起的地表沉降的不同特点,结合隧道的施工、开挖面积、埋深和工程地质条件等因素,对隧道下穿不同的结构物提出不同的控制沉降措施和建议...     

Euler-Euler two-phase flow simulation of tunnel erosion beneath marine pipelines

In this study an Euler-Euler two-phase model was developed to investigate the tunnel erosion beneath a submarine pipeline exposed to unidirectional flow. Both of the fluid and sediment phases were described via the Navier-Stokes equations, i.e. the model was implemented using time-averaged continuity and momentum equations for the fluid and sediment phases and a modified k−ε turbulence closure for the fluid phase. The fluid and sediment phases were coupled by considering the drag and lift interaction forces. The model was employed to simulate the tunnel erosion around the pipeline laid on an erodible bed. Comparison between the numerical result and experimental measurement confirms that the numerical model successfully predicts the bed profile and velocity field during the tunnel erosion. It is evident that the sediments are transported as the sheet-flow mode in the tunnel erosion stage. Also the transport rate under the pipe increases rapidly at the early stage and then reduces gradually at the end of the tunnel erosion beneath pipelines.     

城市盾构隧道水平冻结地层加固的数值分析

冻结地层加固法是一种环境影响小、加固效果好的地层加固方法,人工冻结壁的形成是一个复杂的热-力耦合问题。依托实际盾构隧道始发施工中冻结加固工程,采用有限差分软件Flac3D建立数值模型分析了地铁隧道水平冻结施工中温度场随时间的发展和分布特征,同时采用准热-力耦合的方法,分析了冻结施工中地表冻胀隆起变形规律。分析结果表明：冻结壁模拟交圈时间和设计交圈时间基本一致;冻结壁交圈前,地表冻胀隆起位移速率快,冻结壁交圈之后,地表冻胀变形逐渐趋近稳定。计算结论可供设计和施工参考,提供了一种简便的人工冻结加固施工的数值模拟方法。     

Analysis of fracture propagation in a rock mass surrounding a tunnel under high internal pressure by the element-free Galerkin method

Fractures developed around high pressurized gas or air storage tunnels can progressively extend to the ground surface, eventually leading to an uplift failure. A tool reasonably reproducing the failure patterns is necessary for stability assessment. In this study, a numerical method based on the element-free Galerkin (EFG) method with a cohesive crack model is developed to simulate fracture propagation patterns in the rock mass around a tunnel under high internal pressure. A series of physical model tests was also conducted to validate the reliability of the developed method. A qualitative agreement between physical model tests and numerical results can be obtained. The in situ stress ratio, k, has a strong influence on both the position of crack initiation and the propagation direction. The numerical analyses were extended to full-scale problems. Numerical tests were performed to investigate the prime influencing factors on the failure patterns of a high pressurized gas circular tunnel with varying parameters. The results suggest that initial in situ stress conditions with a high k (larger than 1) is favorable for construction of pressurized gas or air storage tunnels.