深埋隧道锚杆支护作用的数值模拟与模型试验研究

以重庆至长沙公路共和隧道为研究对象,研制出环氧-硅橡胶的相似模型材料,在大型真三轴模型试验机上进行了隧道在毛洞和锚杆支护条件下的超载试验,采用应变测量技术对隧道关键部位的应变值和锚杆的应变值进行了测量,据此分析了围岩体在锚杆支护后的应力变化规律和锚杆的轴力变化规律。采用与模型试验相同的边界条件进行了隧道在锚杆支护条件下的数值模拟工作,对围岩体的塑性区、应力场和锚杆轴力随荷载的变化过程进行了研究。结果表明,两种手段反映的围岩体应力变化规律和锚杆轴力随荷载的变化规律是一致的     

深埋隧道围岩松动圈探测技术研究与数值模拟分析

围岩松动圈支护理论已被工程界广泛认同和接受,如何准确快速地探测松动圈深度更好的为工程服务,成为大家所关注的问题。以新建兰新铁路大梁隧道现场试验为依托,对测试断面围岩松动圈深度采用单孔声波测试法、地质雷达法进行探测,结合现场地应力及岩体物理力学参数实测结果进行数值模拟分析可知,以单孔声波测试法结果为基准,地质雷达测试结果与声波法测试结果基本一致,在围岩含水区域测试结果存在一定偏差,地质雷达发出的电磁波对含水区域比较敏感,发射和接收干扰较大,但地质雷达作为一种快速、无损的检测方法应该得到大力推广应用。由于数值计算时没有考虑爆破对围岩松动圈的影响,其计算结果与声波法探测结果相比偏小,但是两者的变化趋势基本上是一致的。数值计算应以现场地应力及岩体物理力学参数测试结果为依据,使计算结果更加真实,更好地为工程决策服务。     

基于RHT本构的隧道爆破参数优化与振动损伤数值研究

为了解决爆破参数优化问题以及考虑炮孔间相互作用对围岩损伤空间分布的影响,先利用数值试算与冲击试验相对照的方法,标定出大理岩Riedel-Hiermaier-Thoma本构模型参数。接着,对隧道全断面爆破开挖开展模拟计算,考察了多炮孔间相互作用下围岩爆破损伤演化过程。最后,基于起爆顺序、径向不耦合系数和分段间隔装药3种方法来优化爆破参数,并对质点振动和围岩损伤进行了深入分析。结果表明：标定所得的本构参数可准确描述大理岩动态应力-应变响应,且模拟结果能很好地揭示爆破损伤演化规律;岩石损伤从爆心处向外发展,随后在炮孔连线上连接贯通;相比于上述其他2种方法,当径向不耦合系数k小于1.33时,在保证爆破效果前提下改变k值能有效地降低围岩的爆破损伤;隧道竖向平均振动速度要大于水平向的对应值,且竖向拱顶和底板中部对爆破振动呈现较高的敏感性。研究结果为工程实践中爆破参数优化选取和围岩损伤精确评估等可提供参考。     

预应力锚索支护参数优化研究在金川二矿区的应用

针对金金川二矿区深部高应力采场巷道支护面临的困难,采用以预应力锚索为主要支护手段的综合控制技术,并在1 178 m分段巷道进行了现场试验研究.首先,基于工程经验,确定了长锚索支护的初步设计参数;然后,采用了数值分析方法,进行了正交数值试验和支护参数的优化设计,由此表明,对于Ⅲ类偏上的围岩(RMR=40)和受中等采动影响(β=1.20),预应力锚索长度应为6.5 m;对于受剧烈采动影响的1 178 m分段巷道,采用6.5 m长锚索支护,其稳定安全系数达到1.28,故5.5～6.5 m长的锚索可满足分段道的稳定要求.     

浅埋偏压软岩隧道数值模拟及方案比选

围岩的应力应变是分析隧道开挖中围岩稳定性的重要依据。目前比较成熟的隧道施工力学方法主要是对隧道开挖过程进行数值模拟。通过大型有限元软件ANSYS,计算了不同埋深、不同坡度角、不同覆盖层厚度条件下,马鞍形浅埋偏压软岩隧道围岩的应力应变,分析其规律并进行方案比选,确定了此类隧道比较合理的设计方案。分析结果表明：以2倍洞径的埋深作为偏压隧道深埋或浅埋的判断依据是合理的;在保证围岩稳定不发生片帮冒顶的前提下,减小埋深和覆盖层厚度是比较合理的;隧道内壁各点的应力应变规律可以为隧道开挖中支护结构参数的选取提供参考。     

基于可拓学理论的围岩分级方法在变质软岩隧道中的应用

对可拓学中物元、可拓集合的概念进行了阐述,并以火车岭隧道为例,结合影响变质软岩区隧道稳定性的岩性、结构面、地下水等主要因素,选取钻孔岩芯质量、隧道埋深、地下水流量、饱和单轴抗压强度、结构面间距作为评价指标,同时选择3个典型岩段,建立相应的待评物元模型;对各评价指标及各围岩级别的关联度指标进行了计算,据此对3个岩段进行分级的结果表明,绿泥钠长石英片岩岩段为Ⅲ级,与原设计相符;绢云母石英片岩岩段为Ⅱ级,比原设计低一级;白云钠长石英片岩岩段为Ⅳ级,比原设计高一级.该分级方法与RMR法、Q法及公路隧道规范分级方法的对比结果表明,传统方法与现场条件存在较大误差,证明基于可拓学理论的围岩分级方法能较好地满足该围岩条件的要求,同时分析了传统围岩分级方法在该地质条件下应用的缺陷.     

深埋断层节理段导流隧洞围岩稳定性分析

西南某水电站导流隧洞K1+350～400桩号发育F13断层等多条节理,埋深大,地应力较高,地质条件复杂。运用三维离散单元软件3DEC对其进行数值模拟,并结合现场监测数据对其围岩稳定性进行分析。结果表明,该段围岩稳定性主要受结构面控制,F13断层下盘右拱肩掉块较多,位移较大,支护后导流隧洞围岩稳定性得到加强,支护效果较好。     

Optimization Methods of Blasting Parameters of Large Cross-Section Tunnel in Horizontal Layered Rock Mass

For large cross-section tunnel in horizontal layered rock mass, blasting excavation often causes serious overbreak and underbreak. In this study, blasting excavation tests of tunnel upper face were conducted, blast-induced excavation damage and the influence mechanisms of weak beddings and joints were analyzed based on the Panlongshan tunnel. In order to achieve fine excavation, the cut mode of “center holes and four-wedge cutting holes”, the blasthole pattern of “empty holes, long holes, short holes and additional relief holes”, the maximum single-hole charge and the air-deck charge structure were proposed. Compared with the damage characteristics, overbreak and underbreak, and deformations of surrounding rock before and after optimization, the latter was better in tunnel contour formation and surrounding rock stability. The results show that after optimization, the large-area separation of vault rock mass is solved, the step-like overbreak of spandrel rock mass is reduced and the large-size rock block and underbreak are avoided. The maximum linear overbreak of vault, spandrel, and haunch surrounding rock is decreased by 42.3%, 53.7% and 45.1%, respectively. The underbreak at the bottom of the upper face is reduced from ??111.5 to ??16.5 cm. The average overbreak area is decreased by 61.1%. The surrounding rock displacement after optimization finally converges to the smaller value. The arch crown settlement and the horizontal convergence of haunch are reduced by about 21.6% and 18.3%, respectively. Furthermore, from the completion of blasting excavation to the stabilization of surrounding rock, it takes less time by using the optimized blasting scheme.

     

软岩巷道围岩流变大变形有限元计算方法

本文针对软岩工程中围岩流变大变形问题，以有限变形力学理论为依据，采用更新拖带坐标法编制非线性大变形有限元计算程序，对软岩巷道流变大变形问题进行了数值模拟计算。在计算中，选用了适合描述软岩流变大变形的物性方程，并考虑了锚杆和拱两种支护方式。结合表明，本文采用的理论和计算方法合理，计算程序具有精度高、收敛速度快等优点，展示了良好的应用前景。     

Structure Optimization for the Support System in Soft Rock Tunnel Based on Numerical Analysis and Field Monitoring

Optimization of the support used when constructing tunnels in soft surrounding rock has long been a hotspot in engineering. To control the deformation of soft rock and ensure construction safety, this paper proposes a support scheme involving weakening the anchor bolts while enhancing the rigidity and strength of the primary supports. This was realized by combining the large deformations that often occurred during the construction of the Youfangping tunnel of the Gucheng-Zhuxi expressway. Moreover, the scheme was analyzed and compared with the original scheme and one involving weakening the anchor bolts. In addition, the displacement deformations, force conditions on the anchor bolts, development of plastic zones, stress on the shotcrete, and force conditions on the secondary lining structure were analyzed via numerical simulation for the different support schemes. Concomitantly, three groups of experimental sections were selected on-site to monitor and measure the deformations and force conditions of the surrounding rock for these three support schemes. The numerical simulations and field-monitoring results show that weakening the anchor bolts has a small effect on the overall support provided by the support system. However, it can simply the process and reduce engineering costs. Moreover, increasing the rigidity and strength of the initial supports can effectively control the large deformations in the surrounding rock. Therefore, a support scheme in which anchor bolts are weakened while the rigidity and strength of the initial supports are enhanced, as presented in this paper, proves to be feasible method of support optimization. It also provides a useful reference for optimizing other similar tunnels along the expressway.     

三江造山带玉峰寺深埋隧道岩爆危险性综合评价

深埋隧道的岩爆机理和岩爆预报预测一直是工程地质和岩石力学的热点和难点问题,已成为困扰地下工程发展的瓶颈之一。以滇藏铁路穿越三江造山带玉龙雪山南段的玉峰寺深埋隧道方案为例,在野外工程地质调查的基础上,对影响隧道岩爆的相关因素进行了系统分析。根据岩石力学试验、地应力分析和数值模拟计算结果,采用多种判据对玉峰寺隧道岩爆危险性进行了分析预测和综合评价。研究结果对于地质构造复杂区深埋隧道规划设计和岩爆灾害防治具有一定指导意义。     

Numerical Modelling of the Behavior of Tunnel in Soft Surrounding Rock: A Case Study of Djebel El-Ouahch Tunnel,Algeria

The response of a massif to stresses generated by tunnel excavation depends essentially on the geological conditions, the geometry of the tunnel and its underground position. The major problem related to the construction of these structures is to ensure the stability of the whole tunnel-ground, by controlling the various deformation generated during the construction. In this context, the present paper examines the effect of these conditions on the behavior of tunnels and the surrounding soil. The study is applied to a real tunnel, in this case the tunnel of Djebel El Ouahch, Algeria was taken as a reference model. The research includes a parametric study to evaluate the effect of several parameters on the behavior of the tunnel and surrounding soil such as the tunnel anchoring depth, the tunnel-soil interface rate, and the shape of the tunnel cross section. The analysis is performed using the PLAXIS 3D TUNNEL calculation code with an elastoplastic Mohr–coulomb model for the soil behavior. The results show that the strongest and most stable position is the mid-deep tunnel with a circular section, with a non-slip interface between the tunnel and the ground. These outcomes can help to understand the effects of various influences parameters which control the stability of the tunnel in a soil with bad characteristics.

     

Influence of Rock Mass Parameters on the Performance of a TBM in a Gneissic Formation (Varzo Tunnel)

Summary The paper analyses the influence of rock mass quality on the performance of a double shield TBM in the excavation of a tunnel in a gneiss formation which is characterized by high strength and low fracture intensity.As full observation of the rock conditions was prevented by the use of segmental lining, a geomechanical survey of the face was performed during maintenance downtime and the observed conditions were correlated with the machine performance parameters for that same day. A statistical analysis of the data shows that penetration rate correlates well with a slightly modified RMR index (in which the influence of the water conditions and joint orientation were discounted), but the most important factor is by far the partial rating of the RMR classification related to joint spacing only. However in tunnels characterized by greater variability in rock strength and joint conditions, it could be worthwhile using the complete RMR index.Given the toughness of the rock, failure of the cutter bearings and supports were a frequent occurrence during excavation. Owing to this factor the influence of rock quality on the rate of advance was found to be weak and the correlation more scattered.The results obtained for the Varzo tunnel were compared with those relative to other tunnels in granitic rocks and found to be in good agreement. However the relationships obtained should be considered valid only for this type of rock; machine behaviour could be found to be markedly different in other rock types, even where rock material strength and joint frequency are the same.