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1.
软弱围岩隧道洞口段失稳机制分析与处置技术 总被引：1，自引：0，他引：1
隧道洞口围岩大多为软弱围岩,加之浅埋、偏压等不良地质地形因素的影响,洞口施工过程中易发生边仰坡的滑塌。厦蓉高速公路水都线的瑞坡隧道在进洞后不久就发生围岩失稳,致使仰坡开裂滑塌和洞内支护变形很大。利用FLAC3D软件模拟了隧道施工全过程,从围岩塑性区分布以及位移情况结合现场实际状况分析了隧道仰坡坍塌和支护变形发生的原因,并通过数值模拟优化了CRD法的开挖工序。最后参考数值分析结果结合工程实际提出了有效的治理措施,得到的结论可供今后类似工程参考与借鉴。 相似文献
2.
Q2饱和黄土隧洞围岩变形特征研究 总被引：1，自引：0，他引：1
Q2饱和黄土含水率高,强度低、变形大。饱和黄土隧洞围岩变形破坏一直是工程界关心和亟待解决的问题。利用隧洞围岩收敛变形、二次应力场监控量测与数值分析,获取隧洞围岩动态综合信息,研究在一次支护条件下,隧洞围岩的收敛变形和应力变化特征。结果显示,隧洞围岩收敛变形和应力在最初的10~15天呈线性快速增长趋势。后期,收敛变形随时间呈非线性增加,受一次衬砌的限制,其变形在隧洞开挖30~40天后渐趋于稳定,但应力持续增加,反映Q2饱和黄土隧洞围岩具有显著的时效特性。为避免隧洞围岩压力过大,造成隧洞围岩及支护破坏,建议在开挖后30~40天施作二次衬砌。 相似文献
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4.
松散堆积体隧道围岩变形破坏细观特征研究 总被引：1，自引：0，他引：1
隧道穿越复杂松散堆积体地层时,如何确保隧道施工过程的安全是工程人员普遍关心的课题。依托云南省罗打拉隧道,基于Monte Carlo随机原理,结合数字图像处理技术,建立了考虑接触面单元及抗拉强度的堆积体地层隧道开挖细观结构模型,并探讨了隧道开挖引起的堆积体围岩变形、破坏过程以及失稳机制,并在现场进行应用验证。研究结果表明,构建的堆积体地层隧道开挖细观结构模型可有效反映隧道开挖过程中围岩的破坏过程,围岩位移等值线呈波动性与非对称性分布;围岩破坏以剪切破坏为主,局部存在拉裂?剪切复合破坏,且破坏区由边缘块石尖端向深层逐步扩展,形成包裹块石的剪切楔形区及拉剪松动圈,在施工扰动下易发生局部失稳。针对堆积体地层破坏特征,提出了围岩注浆加固措施,地层加固后土石颗粒间胶结良好,开挖轮廓周边形成有效的注浆加固圈,开挖支护过程围岩变形可控,支护结构稳定,效果良好,可为后续类似松散堆积体地层隧道的设计、施工提供新思路。 相似文献
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关角隧道是西（宁）格（尔木）二线的控制性工程,在隧道入口处存在长约450 m的砂层,施工难度较大。由于在3台阶施工中出现了冒顶事故,故提出了4台阶施工的设想,并利用三维数值计算模拟了4台阶开挖支护过程,揭示了隧道的空间变形、地表沉降和初支受力特征。通过与3台阶施工模拟结果对比证实了4台阶方案的优越性;现场施工和变形量测结果表明,采用大拱脚断面形式和超短四台阶施工方案,施作长大水平超前管棚、设置临时钢横撑、缩短仰拱封闭距离等是保证大断面浅埋砂层隧道安全施工的有效方法,对其他类似工程施工提供了宝贵的工程经验。 相似文献
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Mehmet Ozcelik 《Geotechnical and Geological Engineering》2018,36(6):3437-3449
Mechanized tunnelling is a well-established tunnel construction method which allows constructing tunnels in various conditions including mixed ground conditions as well as tunnels in vulnerable urban areas. The selection of the excavator suitable for the geological structure is important in terms of realizing an efficient tunnel excavation. Tunnel excavation studies of Istanbul Kabatas–Mecidiyeköy Metro tunnels are implemented as a double tube. Geology in this section is composed of sandstone, siltstone, mudstone interbedded or as separate units along with dyke intrusions. Calcareous clay, clayey limestone, clayey sand are also rarely observed. Between the Kabatas–Mecidiyekoy tunnels includes two types of mechanical excavation methods namely tunnel boring machine (TBM) and new Austrian tunnelling method (NATM). Main purpose of this study is mixed ground and their impacts on mechanized tunnelling. At the end, some issues have been presented which seems to be important for the success of TBM and NATM in the mixed grounds. As the tunnel excavation studies continued, the problem of collapse on the ground surface of Barbaros Boulevard in Besiktas station increased the importance of tunnel excavation under mixed ground conditions. 相似文献
7.
浅埋偏压隧道洞口坍方数值分析与处治 总被引：2，自引：0，他引：2
某公路隧道在进洞时出现坍方。针对该隧道工程的实际情况,建立数值分析模型,采用ANSYS程序模拟隧道施工力学行为,从围岩塑性区分布、位移以及锚杆和混凝土衬砌内力分布情况分析隧道变形和坍塌发生的原因。结果表明：隧道浅埋偏压、围岩力学性质差及施工支护不当导致坍方。结合工程实际提出洞内加固、地表注浆加固及开挖控制的综合处治方法,取得了理想的效果,为日后类似工程提供借鉴与参考。 相似文献
8.
“引大济湟”调水总干渠输水隧洞埋深大,地应力较高,其中穿越的洞段Ⅳ、Ⅴ类围岩占有较大的比例,在高地应力作用下围岩开挖卸荷后极可能出现大变形失稳、垮塌等,这些都极大地影响着TBM的掘进效率及施工进度。根据洞室开挖过程中实际揭示的围岩地质条件及变形特征,采用三维黏弹塑性数值方法,对围岩的流变特性与时效变形进行研究;在对实测地应力场进行分析基础上,结合围岩现场变形规律,对围岩蠕变力学参数进行了反演,进而对隧洞开挖区域的软弱围岩进行黏弹塑性数值分析,获得了规律性认识,为动态调整设计提供科学依据。 相似文献
9.
Attewell, P.B. and Farmer, I.W., 1974. Ground disturbance caused by shield tunnelling in a stiff, overconsolidated clay. Eng. Geol., 8: 361–381.
Some of the factors affecting ground deformation around shield tunnelling excavations in stiff clays are considered. There is particular reference throughout the paper to an analysis and interpretation of measured ground deformation around a 4.146-m diameter, hand-excavated, shield-driven tunnel at a nominal axis depth of 29.3 m in the overconsolidated London Clay. The maximum surface settlement was found, by precise levelling, to be 6.1 mm but the shape of the transverse surface settlement profile conformed to a normal probability curve only up to the time of shield passage. Of the contributory ground losses at the tunnel, yield of the clay at the tunnel face appears to dominate to the extent of generating up to 50% of the eventual surface settlement. Measurement evidence suggests a rate of yield at the face that is 2 to 3 times the radial yield over the shield and implies that up to about one-fifth of the surface settlement could be attributed to radial yield into the grouted sections of the erected tunnel lining. 相似文献
10.
Claudio di Prisco Luca Flessati Gabriele Frigerio Riccardo Castellanza Marco Caruso Andrea Galli Pietro Lunardi 《Acta Geotechnica》2018,13(3):651-670
In spite of the increasing diffusion of tunnel boring machines, conventional tunnelling is still preferred for economic reasons in case of short tunnels, unconventional cross sections or irregular tunnel trajectories. In conventional tunnelling, the mechanical response of the tunnel front is a main concern and, when tunnels are excavated in cohesive soils, this is dominated by the time factor, related to geometry, to the mean excavation rate and to the hydro-mechanical properties of the materials involved. This is particularly evident during excavation standstill: front displacements progressively increase with time and, in many cases, the system response under long-term conditions becomes unstable. In conventional tunnelling, a common technique employed to improve the system response (under both short- and long-term conditions) is the installation of fibreglass tubes within the advance core. In this paper, the mechanical response of both unreinforced and reinforced deep tunnel fronts in cohesive soils is experimentally analysed. In particular, the results of a series of 1 g small-scale tests, taking into account both the influence of the excavation rate (the unloading time) on the system response and the evolution with time of the tunnel face displacements, induced by a rapid reduction in the horizontal stress applied on the tunnel face, are reported. 相似文献
11.
错动带具有“历史上多次剪切错动、延伸范围广、遇水易软化、力学强度低”的软弱特性,致使其在开挖卸荷作用下极易诱发不同程度的变形和破坏,进而严重影响地下洞室的稳定性。针对白鹤滩水电站右岸9#母线洞（地下交叉洞室）发生的错动带岩体塌方破坏,借助高精度、实时微震监测系统,系统地研究了塌方孕育过程中的微震活动性,包括微震事件时空演化规律、震级和视应力分布特征。采用矩张量理论,反演塌方孕育过程中的微震事件破裂机制（张拉、剪切或混合）,归纳、总结其演化过程为：表层围岩卸荷张拉破裂→裂纹渐进向围岩深部扩展→破裂沿错动带方向萌生、扩展（张拉破裂为主,伴随剪切或混合破裂）→裂缝与错动带交汇,切割出不稳定楔形体→爆破振动或重力作用下,错动带岩体塌方。该研究结果可为高应力地下交叉洞室错动带岩体的开挖、支护提供参考,同时对类似工程的施工具有重要借鉴意义。 相似文献
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Summary ¶Rock zones containing a high fracture density and/or soft, low cohesion materials can be highly problematic when encountered during tunnel excavation. For example in the eastern Aar massif of central Switzerland, experiences during the construction of the Gotthard highway tunnel showed that heavily fractured areas within shear zones were responsible for overbreaks in the form of chimneys several metres in height. To understand and estimate the impact of the shear zones on rock mass behaviour, knowledge concerning the rock mass strength and deformation characteristics is fundamental. A series of laboratory triaxial tests, performed on samples from granite- and gneiss-hosted shear zones revealed that with increasing degree of tectonic overprint, sample strength decreases and rock behaviour shows a transition from brittle to ductile deformation. These trends may be explained by increasing fracture densities, increasing foliation intensity, increasing thickness of fine-grained, low cohesion fracture infill, and increasing mica content associated with the increasing degree of tectonic overprint. As fracture density increases and the influence of discrete, persistent discontinuities on rock mass strength decreases, behaviour of the test samples becomes more and more representative of rock mass behaviour, i.e. that of a densely fractured continuum. For the purpose of numerical modeling calculations, the shear zones may be subdivided with respect to an increasing fracture density, foliation intensity and mica content into a strongly foliated zone, a fractured zone and a cohesionless zone, which in turn exhibit brittle, brittle-ductile and ductile rock mass constitutive behaviour, respectively.Received December 17, 2001; accepted January 9, 2003
Published online April 29, 2003 相似文献
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Summary The deformational behaviour of tunnels, which underwent large deformations, socalled squeezing, have been recently receiving great attention in the field of rock mechanics and tunnelling. Contrary to rockbursting phenomenon in which the deformation of the medium takes place instantaneously, the deformation of the surrounding rock in squeezing phenomenon takes place slowly and gradually when the resulting stress state following the excavation exceeds the strength of the surrounding medium. Although there are some proposals for the definition of squeezing rocks and prediction of their squeezing potential and deformations of tunnels in literature, it is difficult to say that they are concise and appropriate.In the first half of this paper, the squeezing phenomenon of rock about tunnels and its mechanism and associated factors are clarified by studying carefully observed failures in-situ and laboratory model tests. Then, an extensive survey of tunnels in squeezing rocks in Japan is presented and the results of this survey are summarised. In the second half of the paper, a new method is proposed to predict the squeezing potential and deformations of tunnels in squeezing rock. Then, the method is applied to actual tunnelling projects, where squeezing problems have been encountered, to check its validity and applicability. As a concrete example, an application of the method to predict the squeezing potential and deformations of the rock along a 300 m long section of an actual tunnel was made. 相似文献
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合理进尺的选取是影响隧道开挖施工安全和效率的关键问题之一。以杨家坪隧道现场监测数据为根据,通过ABAQUS软件开展数值试算确定了最接近实际隧道围岩的剪胀角,建立了考虑剪胀角影响的Mohr-Coulomb模型的隧道开挖数值模型,并按1.5、2.0、2.5、3.0、3.5 m开挖进尺开展了计算,对开挖过程中隧道围岩的变形和力学响应规律进行了对比研究。结果显示,考虑剪胀角影响的数值模型计算结果的总体规律与实测结果一致性较好;有锚杆支护的情况下开挖进尺选择为3.0 m能较好地兼顾施工安全与效率,应注意控制距开挖面5.0 m范围内的拱顶变形。 相似文献
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基于对现场地质条件和开挖响应的直观认识和对岩石室内试验所得物理力学特性的深刻揭示,建立了深埋条件下软弱围岩大变形挤压程度分级方法及相对应的安全系数计算方法。该方法考虑到隧洞原岩集聚的能量过大是造成开挖后围岩失稳的根本原因,将隧洞原岩能量和围岩的总变形与弹性变形之比相结合,分析了隧洞的围岩稳定性状况,并在此基础上通过增减隧洞原岩能量得到了其安全系数。通过实际工程应用及与传统经验评价方法的对比,验证了该方法的合理性与适用性。该方法考虑了围岩的地质情况、断面形状、尺寸、开挖方式等多种因素,弥补了传统经验评价方法无法适应复杂多变的现场工程施工情况的不足,更加贴近实际。可为大变形隧洞的安全预测、开挖方案、支护设计等提供重要参考依据。 相似文献
16.
A case history of Tunnel Boring Machine jamming in an inter-layer shear zone at the Yellow River Diversion Project in China 总被引：4，自引：0，他引：4
This is a case study of a Tunnel Boring Machine (TBM) jamming in a section of the Connection Works No. 7 tunnel of the Yellow River Diversion Project (YRDP) in China. Analysis of tunnel lithology, rock convergence by shearing, rock strength and ground stress, indicates that a high rate of convergence within an inter-layer shear zone in the lower part of an anticline was a dominant factor in the jamming. In addition, the shield encountered unfavorable tunnelling conditions in the form of wet clay, groundwater inflow, and cavities, coincident with tensile stresses in the lower part of an adjacent syncline. Based on these diagnoses, economical and quick measures were adopted, including additional excavation outside of the shield leaving free space to release the TBM. After 9 days of being jammed, the TBM was totally released and resumed normal excavation. This example highlights lessons learned from folding and inter-layer shear zone in TBM tunnelling. 相似文献
17.
隧道掘进机（TBM）近年来在世界范围内得到了广泛应用,通常通过完全充满压力仓的泥土或泥浆来支护开挖面。但在较差的地层和水力条件下,开挖面失稳时有发生。事实上,TBM开挖面的支护压力的大小直接决定了施工安全及地表变形。基于所建立的开挖面支护压力计算模型,并考虑复合地层下土体分层带来的影响,通过计算机编程方法,建立了界面友好、使用便捷的开挖面支护压力可视化计算平台(TBM Studio);并结合阿拉斯加隧道、钱江隧道工程实例进行了不同模型结果的验证分析,给出了各模型计算结果的差异性;讨论了软土复合地层条件下,土体自稳性对开挖面稳定的影响,认为软土地层中定量确定有效支护压力和水头高度至关重要,研究为正确评价TBM开挖面稳定性提供了相应的计算模型。 相似文献
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Summary. Tunnel face and wall collapse are common during excavations performed by tunnel boring machines (TBMs) due to the difficulty
of correctly identifying the properties of the excavated rock. This identification, however, can be simplified by using the
cutting force to estimate rock strength, a method that has already proved quite successful in Japanese tunnel excavations.
This paper summarizes knowledge relating to the cutting force obtained through tunnel excavation experience, and the relationship
between rock strength and TBM operation is discussed. Although TBM operators rely on intuition to set the cutter head speed
appropriately, this decision process represents a logical method of operation that takes advantage of the variable speed capability
of the cutter head. Selection of appropriate support methods for the excavated face is also a critical issue in tunnel excavation.
This selection process is based on the condition of the rock, which is difficult to determine quickly and accurately during
tunnel excavation. The present paper uses the excavation of two tunnels to demonstrate that it is possible to assign rock
mass classifications accurately based on rock strength when boring a uniform rock type. It is also shown that the rock mass
can be classified from the rock strength normalized by the uniaxial compressive strength when boring through mixed rock types. 相似文献
20.
This paper presents a novel approach to the simulation of NATM tunnel construction using the Boundary Element Method (BEM) as principal numerical method. This new approach has the advantage that only the excavation surface, the possible plastic zones and the tunnel lining have to be discretised. The whole rock mass is represented by the BEM whereas the Finite Element Method (FEM) is used to represent the tunnel lining only. Thus, a general coupling strategy for coupling three-dimensional boundary elements with shell finite elements (shotcrete) and beam finite elements (steel arches) is presented. To achieve realistic results the effect of hydration of the shotcrete and yielding of the steel arches is considered in the excavation process. Furthermore, the nonlinear rock behaviour is modelled more realistically by using a powerful hierarchical constitutive model which considers a large range of rock materials. The combination of these ideas results in higher user-friendliness and efficiency. Some verification tests and practical applications in tunnelling are presented. 相似文献