1000－7598－(2003)增1―0001―08

随着地下工程的发展,对于埋置较深和地质环境较为复杂的隧道工程,高地温问题已经成为一个重要的工程问题并引起了国内外学者的广泛关注。研究隧道的温度场分布问题对于解决寒区隧道冻融问题、高温隧道问题、隧道火灾灾害等是十分必要的。针对高地温环境中的圆形隧道,假定其具有一定长度且承受轴对称的温度荷载和地应力作用,建立两端简支的二维稳态的热传导方程和平衡方程。利用无量纲化和微分方程级数求解的方法,得到了包含温度场、位移场及应力场的热弹性理论解。依据上述研究结果,以某包含衬砌的圆形断面隧道为例进行了热弹性分析,并得到了由于隧道开挖而引起的围岩的温度变化范围。研究所得结论可为隧道施工及运营过程中隧道的保温隔热提供重要的理论依据。     

高地应力硬岩洞室开挖破坏区数值模拟方法探讨

随着深部地下洞室的大量兴建,深部开挖过程中开挖破坏区的形成及其预测成为国内外岩石力学研究的焦点。本文首先对硬岩破坏过程的力学特性进行了分析,在此基础上对当前岩石力学工程界惯常采用的连续介质模型和粘聚力弱化-摩擦强度强化（CWFS）模型进行了比较;利用岩土工程分析软件FLAC,采用理想弹塑性、弹脆塑性、应变软化及CWFS模型对加拿大Mine-by Experiment圆形试验洞室进行了数值分析,通过对围岩应力分布、关键点应力大小和塑性区分布的对比分析,发现CWFS模型计算得到的应力场更能准确反映破坏区产生后应力向围岩深部转移并集中的特征;这一应力分布特征与开挖破坏区不存在时的结果更接近;与其它模型相比,CWFS模型计算得到的破坏区范围和深度更大,与现场实测值更加吻合。最后采用CWFS模型对挪威Kobbskaret公路隧道破坏区大小进行了计算分析,再次验证了采用CWFS模型对硬岩开挖破坏区预测的合理性。     

岩溶隧道开挖对溶洞处治结构影响的数值模拟分析

结合清连高速公路白须公特大岩溶隧道施工过程,采用三维有限元软件(ANSYS)对白须公隧道的处治结构与隧道开挖的相互作用进行了数值模拟。以隧道开挖中处治结构和围岩稳定性为研究对象,从而分析处治结构在隧道开挖过程中的受力特性,以及隧道围岩在隧道开挖过程中的位移。通过计算结果,对处治结构在岩溶隧道中的支护效果进行了评价,采用桩-承台-单边支撑墙-联系梁的处治方式是安全可靠的。在隧道开挖过程中,开挖面附近的桩基应变、支撑墙压力都加速变大,随后逐渐稳定,说明处治结构承担了一部分围岩压力,在岩溶隧道施工开挖中发挥了重要作用。分析结果与工程实测数据比较吻合,可为隧道穿越大型溶洞提供设计和施工方面的借鉴和参考。     

叠落盾构隧道受力分析及管片配筋

在现代城市轨道交通建设中,上下叠落地铁盾构隧道越来越多,这类叠落盾构隧道相互影响,塌落拱多次叠加,传统解析法计算隧道围岩压力存在困难,目前缺乏相应的叠落隧道围岩应力计算方法。为了研究叠落盾构隧道受力分析及管片配筋,以北京地铁6号线南锣鼓巷站—东四站叠落盾构隧道为工程实例,根据弹塑性理论模拟隧道开挖过程计算塌落拱多次叠加,结合强度折减法计算叠落隧道塑性区,然后根据塑性区计算塌落拱高度和围岩压力;根据厚壁圆筒理论,计算盾构施工和列车运营对下方隧道附加应力;根据以上分析,计算叠落隧道的下方盾构隧道管片内力并配筋。     

Tunnel complex unloaded by a deep excavation

This paper examines the effect of a deep open excavation for an office block on the underlying tunnel complex in the centre of Prague, which was analysed using 2D FEM models. In order to get a proper reference state before excavation, the whole process of construction of the tunnels was modelled and deformation and stress changes induced by open excavation predicted. Bearing capacity, distortion and watertightness of underground structures were then evaluated and recommendations concerning the construction rate and monitoring program given. A good agreement between the pure prediction of tunnel distortion produced by FEM and the measurements undertaken during excavation of the pit and construction of the office block was obtained.     

Analytical Solutions for the Construction of Deeply Buried Circular Tunnels with Two Liners in Rheological Rock

The construction of underground tunnels is a time-dependent process. The states of stress and strain in the ground vary with time due to the construction process. Stress and strain variations are heavily dependent on the rheological behavior of the hosting rock mass. In this paper, analytical closed-form solutions are developed for the excavation of a circular tunnel supported by the construction of two elastic liners in a viscoelastic surrounding rock under a hydrostatic stress field. In the solutions, the stiffness and installation times of the liners are accounted for. To simulate realistically the process of tunnel excavation, a time-dependent excavation process is considered in the development of the solutions, assuming that the radius of the tunnel grows from zero until its final value according to a time-dependent function to be specified by the designers. The integral equations for the supporting pressures between rock and first liner are derived according to the boundary conditions for linear viscoelastic rocks (unified model). Then, explicit analytical expressions are obtained by considering either the Maxwell or the Boltzmann viscoelastic model for the rheology of the rock mass. Applications of the obtained solutions are illustrated using two examples, where the response in terms of displacements and stresses caused by various combinations of excavation rate, first and second liner installation times, and the rheological properties of the rock is illustrated.     

地下洞室开挖过程围岩应变能调整力学机制

深埋洞室岩体开挖过程中,围岩应变能的聚集和释放是洞室发生灾变破坏的重要诱因。针对圆形洞室开挖,分析和比较初始地应力准静态和动态两种不同卸载方式下围岩应变能的调整过程,基于能量角度判定了围岩损伤范围。研究表明：伴随地下洞室的开挖,岩体能量靠径向应力做功的方式在围岩中由远及近传递,并导致近区围岩应变能聚集;初始地应力动态卸载诱发围岩应变能先减小后增大,先对靠近开挖面的相邻岩体通过径向应力做功的方式释放自身的应变能,随着卸载应力波的继续向前传播,远离开挖面的相邻岩体又通过径向应力对其做功的方式促使其应变能聚集;相比初始地应力准静态卸载,动态卸载条件下高应变能聚集程度导致围岩损伤破坏范围更大。     

西部地应力测量与岩爆分析

通过对我国西部一些重点工程的地应力测量,大致得出西部工程的应力状态,并从实测地应力资料出发,采用现有的、普遍应用的岩爆判别准则,对这些工程在施工开挖期间的地下工程进行岩爆预测分析。     

Toppling and stabilization of the intake slope for the Fengtan Hydropower Station enlargement project, Mid-South China

The intake slope for the Fengtan Hydropower Station enlargement project is composed of thickly bedded sedimentary rock. During excavation of the intake slope and tunnels, toppling was observed in the rock masses of the intake slope. Research was conducted to study the engineering geological conditions and the deformation characteristics of the slope during excavation. The in situ monitoring data and possible causes for toppling were analyzed. A method for analyzing monitoring data was proposed, which can be used to calculate the depth and rotation angle of block toppling. The monitoring results showed that toppling occurred only at a shallow depth, and induced local instability of the slope. Deformation had been controlled and the slope tended to be stable after reinforcement. Through this case study, it can be seen that the stability of the slope and underground openings during and after excavation is variable, especially when the loading conditions and topography are changed. A proper construction sequence is essential, i.e., excavation from the inside toward the free slope surface; excavating the slope above the tunnel after the tunnel lining is in place. This is particularly important for the excavation of multiple tunnels at the slope toe.     

Reflection on the problems in mechanical response monitoring and testing design of deep tunnels

Nowadays the number of deep tunnels is greatly increased. Since there are lacking successful numerical methods and experiences from relevant engineering construction and design of deep tunnels, massive on-site monitoring and testing should be conducted to support the design and safety control. The present monitoring and testing design methods are proposed according to the characteristics of shallow underground engineering. However, when they are introduced into the deep tunnels, great challenges are encountered. In this study, the failure of surrounding rock mass in the field was presented and then the deformation and failure responses of surrounding rock mass were obtained during excavation by various advanced observation techniques. Based on the acquired information, this study analyzed the mechanical response characteristics of surrounding rock mass during excavation and lining at the operating period. Then we discussed the problems arising from the application of current modern monitoring methods. Six suggestions were put forward relating to the monitoring and testing design of the representative section in the deep tunnel. This study can provide helpful guidance to improve the design methods in similar projects.     

岩溶区隧道围岩--支护体系稳定性研究

岩溶是地下水地质作用的过程和结果，是隧道建设面临的不良地质现象之一。正在建设中的某高速公路隧道出口段岩溶地质作用强烈，溶隙、孔洞发育，且受构造变形及后期淋滤溶蚀作用强烈，力学强度低，岩性复杂。其角砾状粘土岩和水云母粘土岩多已泥化成粘土，遇水易膨胀。岩溶区隧道围岩——支护体系的稳定性是该隧道建设面临的主要问题。文章结合隧道施工过程中的围岩变形监控量测和三维弹塑性有限元数值仿真模拟对隧道围岩——支护体系的稳定性进行了研究。围岩水平收敛和拱顶下沉位移及速率变化特性表明，在监测时段内隧道围岩无趋于稳定的迹象。施工动态力学数值仿真模拟表明，在初期支护条件下，围岩出现了较大范围的塑性破坏区，两隧道之间(间距45．0m)围岩破坏接近度达到0．70，最大竖向位移达到3．0mm，表明隧道全断面施工时，两隧道相互作用影响程度较大。为确保隧道围岩——支护体系的稳定，选择合理的施工方法，制定切实可行的支护方案提供了信息。     

深埋隧洞力学响应监测与测试设计的思考

深埋隧洞工程越来越多,但相关工程经验积累不足,设计和计算方法远未成熟,深埋隧洞工程设计和施工安全控制需要大量现场监测和测试数据的支撑,而现有的监测和测试设计方法均针对浅埋工程的特点提出,在深埋隧洞施工过程中应用时遭遇到极大挑战。为此,首先依据现场揭露现象和多种先进观测技术获得的成果,分析了深埋硬岩隧洞施工期围岩的开挖力学响应特征和运行期衬砌的力学响应特征,剖析了现今主流观测方法存在的问题,提出了6条关于深埋隧洞典型断面监测和测试设计的建议,为促进此类工程相关设计方法的完善提供参考。     

金华山软岩铁路隧道施工过程围岩屈服接近度分析

隧道施工过程中围岩处于复杂应力状态下,隧道围岩屈服区演化特征的确定对于围岩稳定性分析和开挖支护方案优化具有重要的意义。采用屈服接近度指标衡量围岩破坏接近程度可以合理地描述复杂应力状态下围岩的应力危险性,对Mohr-Coulomb类岩体材料的屈服接近度函数进行了相应的推导,并在非线性有限元用户子程序上编程予以实现。介绍了赣州-龙岩铁路DKl33+095～DKl38+237段软弱围岩单线隧道正台阶步施工方案以及湿喷纤维混凝土支护方案。为了对该隧道施工过程中隧道围岩屈服区的演化特征进行合理评价,采用非线性有限元法对软弱围岩条件下的铁路隧道施工过程进行了数值模拟,分析了施工过程中隧道围岩屈服接近度分布特征,判定了隧道台阶步施工过程中隧道围岩的稳定性。分析结果表明:该隧道施工过程中围岩破坏区主要发生在下台阶步施工过程中;屈服接近度指标比传统的塑性区分布提供的信息更加丰富,有利于工程技术人员定量地评价隧道开挖支护方案。     

云南西北部铁路隧道地应力测试及工程应用

通过地应力测量,确定出工程区隧道围岩现今地壳应力状态,即原地应力的大小和方向.根据地应力分布特征,结合隧道围岩的力学参数,利用三维有限元对工程隧道区进行了应力场模拟.根据原地应力测量及三维计算结果进行综合分析,给出了工程区地应力的赋存规律和基本特征,并进一步分析了隧道开挖中发生岩爆等地质灾害的可能性,同时为隧道的衬砌设计、断面选择及轴线方位的确定提供可靠的科学依据.      

马坑山公路隧道岩爆预测研究

岩爆是高地应力条件下地下洞室开挖过程中经常遇到的一种动力失稳的地质灾害,直接威胁施工人员和设备的安全。论述了岩爆的定义、特征及发生机理,应用国内外相关岩爆判据判定和理论分析,提出对马坑山隧道开挖过程中是否会产生岩爆做出了最终判定。     

A Top Pilot Tunnel Preconditioning Method for the Prevention of Extremely Intense Rockbursts in Deep Tunnels Excavated by TBMs

The headrace tunnels at the Jinping II Hydropower Station cross the Jinping Mountain with a maximum overburden depth of 2,525 m, where 80% of the strata along the tunnels consist of marble. A number of extremely intense rockbursts occurred during the excavation of the auxiliary tunnels and the drainage tunnel. In particular, a tunnel boring machine (TBM) was destroyed by an extremely intense rockburst in a 7.2-m-diameter drainage tunnel. Two of the four subsequent 12.4-m-diameter headrace tunnels will be excavated with larger size TBMs, where a high risk of extremely intense rockbursts exists. Herein, a top pilot tunnel preconditioning method is proposed to minimize this risk, in which a drilling and blasting method is first recommended for the top pilot tunnel excavation and support, and then the TBM excavation of the main tunnel is conducted. In order to evaluate the mechanical effectiveness of this method, numerical simulation analyses using the failure approaching index, energy release rate, and excess shear stress indices are carried out. Its construction feasibility is discussed as well. Moreover, a microseismic monitoring technique is used in the experimental tunnel section for the real-time monitoring of the microseismic activities of the rock mass in TBM excavation and for assessing the effect of the top pilot tunnel excavation in reducing the risk of rockbursts. This method is applied to two tunnel sections prone to extremely intense rockbursts and leads to a reduction in the risk of rockbursts in TBM excavation.     

Temperature effect of rock burst for hard rock in deep-buried tunnel

Much research has been conducted on the influence of rock burst mechanisms and temperature on the mechanical properties of hard rock while research on the effect of temperature on rock bursts is scarce. Therefore, this paper focuses on Rock Burst Proneness Index tests and acoustic emission (AE) tests under the action of high temperature. It was found that the Rock Burst Proneness Index and the AE energy will rise as the temperature rises. It means that the degree of rock burst is increasing instead of decreasing with rising temperature. The research results revealed the temperature effect of rock burst in long deep tunnels under a certain thermal stress condition, which is helpful for explaining the rock burst disaster in tunnels at high ground temperature.     

Modeling and monitoring in a soft argillaceous shale tunnel

Taking advantage of measurements from an in situ monitoring program and an elastoplastic model using the finite-difference method, this paper simulates and evaluates the deformation and stability of a tunnel in soft argillaceous shale. The elastoplastic model is implemented in FLAC3D program to simulate the deformation and the stress of the soft argillaceous shale during construction. In situ tests performed in the soft argillaceous shale tunnel show that the results from numerical simulations are in good quantitative agreement with the measured in situ data. Results of the simulations also suggest that deformation rate is high during the initial phase of tunnel excavation, compared with the later phase, but the time to reach a steady state remains long. Entire primary support has been undergoing plastic deformation before construction of the secondary lining, which takes the form of so-called “shear yield” from the middle to the bottom of the arch. Some auxiliary measures, especially the anchor, should be applied to enhance stabilization because of the large compressive stress located at the arch springing of the tunnel. The methodology applied in this article can be used to investigate the effect of construction on the performance of tunnels in soft argillaceous shale.     

Study on the Influence of Close Distance Construction of Urban Tunnel on the Existing Station

In the construction of the tunnel passing through the existing structure at an ultra-close distance, the existing structure will produce obvious deformation. It is very important to understand the deformation characteristics of the existing upper structure at different positions, especially to ensure the safety of the upper structure and improve the effectiveness of tunnel construction. In this study, the double-line tunnels of Qingdao Metro Line 4 passing under the Cuobuling station were taken as the engineering background, and a detailed 3D numerical model was established. This study comprehensively considered the on-site construction process, including grouting hardening, stress release of the excavated rock mass, grouting pressure and so on. The influence of tunnel excavation on the ground settlement was compared with or without a station structure, and the result was fitted with an empirical formula. Finally, the deformation of the station structure due to the excavation of the double-line tunnels was analyzed. The results of the analysis were as follows: (1) In the presence of the station structure, the excavation of the tunnels had a significant impact on the surface settlement. (2) The settlement of the sidewall caused by the excavation of the left-line tunnel was greater than that of the right-line tunnel, and the settlement at the junction of the sidewall and the bottom plate was smaller than that at other positions of the sidewall. (3) Compared with the roof and middle slabs, the floor of the station was more susceptible to the influence of tunnel excavation. Overall, the research could provide guidance and reference for similar double-line tunnels through existing stations.

     

松散堆积体隧道围岩变形破坏细观特征研究

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。