黄土抗剪强度参数的反演分析及其空间变化规律

根据已有研究将黄土高原按地貌及土的性质分为8个区,在各区现场识别出极限状态边坡,共测得510个极限状态黄土边坡断面,分区建立坡高与坡宽的拟合方程。取极限状态边坡的稳定系数Fs=1.0,基于拟合方程给出的坡高和坡度,用Morgenstern-Price法逐级反演获得各区20~120 m坡高的综合c、φ值。结果表明,随着边坡高度增加,c值线性增高,φ值非线性减小,并基于三轴试验结果揭示了该现象的本质是强度参数随应力变化的体现。不同高度边坡的反演结果都表明,黄土高原自西向东,自北而南,c值增大,φ值减小,这一变化规律与其成分及物理性质反映的特点一致。     

考虑流变效应的高地应力软岩隧道断面形态优化研究

高地应力软岩隧道围岩流变效应明显,形变压力导致的仰拱和边墙连接处的应力集中是导致隧道底鼓破坏的重要原因,合理的隧道断面形态有利于减小应力集中,保证隧道长期安全运营。在考虑软岩流变效应的情况下,以有限元软件ABAQUS为平台,通过Python编程实现隧道断面参数化设计和有限元计算,基于结合罚函数的Nelder-Mead函数建立隧道断面优化算法,并以隧道开挖面积,隧道最大仰拱隆起,围岩蠕变损伤区面积,衬砌最大轴力和衬砌最大弯矩为优化目标,对宜-巴（宜昌至巴东）高速峡口隧道断面形态进行优化,为高地应力软岩隧道断面设计提供科学指导。     

八里扁隧道围岩变形监测与位移反分析

为了判定八里扁隧道在掘进过程中断面处围岩及其支护体系的稳定状态,揭示隧道围岩变形、破坏及稳定的机理,根据隧道断面ZK77+835处围岩变形的监测数据,建立指数函数回归模型,进行精度判定和监测数据分析,同时进行BP神经网络位移反分析与数值模拟,结果表明：采用指数函数模型对断面ZK77+835处围岩变形值进行回归分析的精确度较高;围岩变形存在3个发展时期,从位移值和位移速率两方面可以判定,在监测15d后,该断面处围岩基本处于稳定状态,可以进行二次衬砌施工;利用BP神经网络位移反分析法反演的参数比较准确,将其带入FLAC3D数值模型中,模拟结果与现场监测数据相差不大。     

标准U形断面渠槽水面线的计算模型

用常规的分段求和法完成标准U形断面渠槽水面线计算不但存在误差累积而且计算工作量大、效率低。依据优化拟合理论,以标准剩余差最小为目标函数,在工程适用参数范围内,经拟合计算获得了由一个简化通用算式替代原积分中的分段且不可积函数,并通过积分获得了该种断面水面线的解析计算模型,且由于正、负拟合误差的相互抵消,使最终计算成果的精度进一步提高。利用该模型完成标准U形断面水面线计算可使求解过程大大简化,工作效率明显提高,具有实用推广意义。     

武汉地铁隧道开挖引起地表沉降的数值模拟研究

城市地铁隧道开挖引起过大的地表沉降会对隧道工程本身及地表建筑物造成危害。有效预计并合理控制隧道开挖引起的地表沉降具有重要的实践意义。以武汉地铁虎名区间隧道开挖工程为背景,运用有限元数值模拟软件MIDAS/GTS建立隧道断面开挖的数值模型,计算隧道开挖引起的地表沉降量,与实测沉降量进行拟合; 根据隧道开挖过程中对应地表及临近建筑物的实际情况,优化开挖断面围岩预处理方案,建立优化后的断面开挖模型。模拟结果表明,优化后地表沉降仍在安全范围内,可以为类似工程沉降控制提供参考。     

深埋软弱围岩隧道锚杆参数优化数值模拟

基于乌鞘岭隧道几种典型断面优化的结果,运用有限差分程序FLAC3D,对支护结构的锚杆参数进一步进行优化,包括锚杆的最优长度、横向间距和纵向间距等.研究表明,隧道的拱顶下沉量随锚杆长度的增加而逐渐减小.隧道的拱顶下沉量和墙腰收敛值随锚杆横向间距或者纵向间距的增加而增大,而且当锚杆横向间距超过0.8 m或者纵向间距超过1 m后,锚杆的作用就不明显了.     

基于ARMA模型的隧道位移时间序列分析

在新奥法隧道施工中,隧道位移监测对于评价围岩稳定性和支护结构合理性起重要作用。目前大都采用AR模型对隧道位移进行时间序列分析,避开了非线性估计,致使拟合精度和模型实用性较差。为此,介绍了具有较高预测精度和较好适用条件的ARMA模型及其常用参数估计方法,基于其参数非线性估计带来的不便性,提出一种ARMA模型参数估计近似线性方法,把残差用Taylor级数一阶展开,将非线性估计线性化,用线性最小二乘法估计参数最终值。用该方法对重庆市大足县南环二路南山隧道位移监测数据进行时间序列建模分析,预测与实测值吻合较好,证明了该方法的实用性。     

土工参数粗差处理

本文对工程测试数据的常用异常值判别方法作简要的论述，分析了其优缺点；根据土性参数的特点，说明判别方法在处理土性参数粗差方面的局限性，并作了改进；提出利用极值对方差的影响来确定异常值。     

平面P波入射下浅埋平行双洞隧道注浆加固减震机制

地震动作用下小净距隧道双洞之间存在动力放大效应,依托某强震区小净距盾构隧道工程,基于傅里叶贝塞尔级数展开法,给出了平面P波垂直入射下地下半空间弹性介质中圆形双洞复合式衬砌洞室动应力解析解,深入研究了洞室间距、隧道全环注浆加固参数对衬砌动应力集中的影响。研究表明：洞室间距对衬砌的动应力有显著影响,随着洞室之间距离减小,左右洞室衬砌动应力明显放大;2.5倍洞径可以作为双洞洞室动力临界净距,当洞室间距小于2.5倍洞径时,应进行抗减震设计;注浆全环加固隧道周边土体,可以明显降低衬砌动应力,随着注浆加固区土体刚度增加,衬砌动应力幅值减小;结合工程实际,建议注浆加固区厚度取0.5倍的洞室半径值,加固区岩体和围岩剪切波速度之比取1.2。     

不同断面混合工法小净距隧道施工影响分析

厦门市轨道交通1号线某地铁车站站后设置停车线,依据工程图纸,左线隧道和停车线采用双线单洞大断面暗挖法施工（CRD工法）,隧道直径11.53m,右线隧道采用盾构法施工,隧道直径6.2m,两隧道净距3.85m。本文应用三维动态数值模拟的方法,对不同断面、混合工法、小净距双线隧道的施工顺序进行了研究,并分析了两隧道净距对先行隧道的影响。研究结果表明：1）采用先小后大的施工顺序（即先采用盾构法施工右线隧道,后采用大断面暗挖法施工停车线）可有效减小地表沉降、邻近建筑物变形及隧道结构体系变形。2）当两隧道净距大于1.5D（D为大断面隧道直径）时,后行隧道施工对先行隧道影响较小,附加变形小于3mm。3）大断面暗挖隧道中隔墙拆除阶段对地表沉降量及邻近建筑物变形影响较大,对于此时的变化速率应加以重视。研究结果对相关工程的设计和施工具有一定的借鉴意义。     

Average properties of ellipsoidal fabrics: Implications for two- and three-dimensional methods of strain analysis

Many rocks contain ellipsoidal objects (such as pebbles or reduction zones) which display a variety of shapes and orientations. In deformed rocks such objects may be used for strain analysis by using the concept of an average ellipsoid (here called the “fabric ellipsoid”). Two fabric ellipsoids are defined which are the results of two different algebraic averaging processes. During deformation of ellipsoidal distributions, the fabric ellipsoids change as if they were themselves material ellipsoids and are therefore of fundamental importance in strain analysis.In most studies to date, such 3-D fabric ellipsoids have been obtained from 2-D average ellipses determined on section planes cut through the rock sample. Previous work has assumed that the average ellipses will approximate to section through a single fabric ellipsoid. I show here that this is not the case as sectioning introduces a systematic bias into the section ellipse data. This bias is distinct from the statistical errors (due to finite sample size and measurement errors) discussed in other work and must be considered in any method of strain analysis using section planes.     

双向八车道连拱隧道围岩力学参数反演分析

在采用双侧壁导坑法施工的双向八车道特大断面连拱隧道中,施工步繁多,临时支护设置的时间长,隧道全断面的变形量测只能在临时支护拆除后进行。由于全断面变形数据获取得较晚,故较难将其用于围岩力学参数的反演。将有限元计算和BP神经网络技术相结合,并在有限元计算过程中考虑实际的施工步,建立起所有临时支护拆除之前这一施工状态下导坑的变形量与围岩力学参数之间的非线性映射关系,并通过对应状态下实测的导坑变形值反演了围岩的力学参数。将反演的结果用于正分析验算,验证了该方法是可行的。     

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.

     

Geotechnical parameter estimation in tunnelling using relative convergence measurement

Accurate estimation of geotechnical parameters is an important and difficult task in tunnel design and construction. Optimum evaluation of the geotechnical parameters have been carried out by the back‐analysis method based on estimated absolute convergence data. In this study, a back‐analysis technique using measured relative convergence in tunnelling is proposed. The extended Bayesian method (EBM), which combines the prior information with the field measurement data, is adopted and combined with the 3‐dimensional finite element analysis to predict ground motion. By directly using the relative convergence as observation data in the EBM, we can exclude errors that arise in the estimation of absolute displacement from measured convergence, and can evaluate the geotechnical parameters with sufficient reliability. The proposed back‐analysis technique is applied and validated by using the measured data from two tunnel sites in Korea. Copyright © 2005 John Wiley & Sons, Ltd.     

岩溶地区盾构隧道施工地表沉降规律研究

隧道建设过程中,地下岩溶是诱发地面塌陷事故的主要原因之一。针对盾构隧道周围土层含有隐伏溶洞的情况,通过GTS/NX有限元数值分析软件,研究了相同断面面积下不同形状、不同位置、不同水平长度的岩溶对地表沉降的影响程度。研究结果表明：横向椭圆形溶洞是最不利的溶洞形状;水平位置中,溶洞位于隧道一侧特别是在隧道40°～50°方向上,地表沉降显著增大;竖向位置上存在一个\     

Anchoring Parameters Optimization of Tunnel Surrounding Rock Based on Particle Swarm Optimization

In the highway tunnel project, due to the uncertainty and complexity of geotechnical parameters, it is difficult to design and optimize the anchorage parameters. In order to solve this problem, based on the Zhenfengling tunnel project as the research object, 3D tunnel model was established by ANSYS software, the model was imported into FLAC^3D software for numerical analysis and calculation for the displacement and stress of surrounding rock during construction, using orthogonal experiment methods to analyze factors affecting the stability of surrounding rock. The influence of anchor length, anchor spacing, anchor diameter, the thickness and elastic modulus of spray layer on the displacement of arch waist, arch crown and arch bottom of the tunnel was obtained by using range and variance analysis. The regression model of the relationship between arch surrounding rock displacements and anchorage parameters was determined by fitting regression. The particle swarm optimization algorithm was used to optimize the anchorage parameters in combination with the tunnel section cost formula, and the parameters were compared with those not optimized. Finally, the anchor length is designed as 3 m, the anchor spacing is designed as 1.4 m, the anchor diameter is designed as 21 mm, the thickness of spray layer is designed as 24 cm, and the elastic modulus of spray layer is designed as 24 GPa. The stability requirements can be met, and the economic efficiency is also greatly improved. The cost of support with optimized parameters is 19.4% lower than that of the original design parameters.

     

Application of Convergence–Confinement Method in Analysis of Shallow Non-circular Tunnels

Stress reduction factor, λ, is a dimensionless coefficient in two-dimensional (2D) analysis based on convergence confinement method (CCM) of tunnel which represents stress relaxation in the tunnel walls at different excavation steps. The aim of this paper is to look into the influencing factors on parameter λ around the tunnel walls using finite difference code in order to improve the accuracy of the CCM. For this purpose, four different ground types with various tunnel radii, depths and cross section shapes are considered. Finally, the 2D analysis using uniform and variable stress reduction factors determined in this paper is compared with the 3D analysis of the tunnel. The results of this study enhance our understanding of the role of geometrical and soil material parameters of tunnel on stress relaxation around tunnel walls. The tunnel depth, soil type and tunnel shape have great influence on λ. Variable stress reduction factor enables the convergence–confinement method to predict the realistic behavior of third dimension of the tunnel and can also be used as the best alternative to 3D models.     

基于围岩力学参数快速测定的隧道全断面开挖判定研究

为研究复杂地质条件下隧道全断面开挖条件,以成兰铁路平安隧道为研究对象,建立基于施工现场调查及试验的隧道围岩岩体物理力学参数快速评价体系,综合强度折减法及快速拉格朗日元,进行隧道全断面开挖判定,并进行监测论证。研究表明：基于综合岩体强度快速测试、结构面强度参数测试、结构面安息角测试以及GSI综合岩体强度参数测试,获取的试验结果具有快速、准确、可靠的特点;在采用全断面开挖的前提下,本文所述掌子面围岩的安全系数均大于IⅤ级围岩情况下的围岩的参考安全系数,围岩能够满足全断面开挖隧洞自稳要求,计算结果与监控量测结果具有较强一致性;通过隧道开挖进尺进行优化计算,平安隧道单循环进尺应该控制在2.5m范围以内;在类似于本文所述掌子面岩体物理力学参数的情况下,平安隧道进行全断面开挖施工是完全可行的。     

软弱围岩隧道洞口段失稳机制分析与处置技术

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。     

监控量测在横龙山喇叭口隧道施工中的应用

福龙路横龙山隧道采用新奥法施工,介绍了横龙山隧道超大断面喇叭口段施工监测对围岩位移及受力变化的监控量测技术,介绍了该项目根据监控量测分析处理结果及时调整隧道预应力锚杆等支护系统设计参数。实施结果表明,周密的施工监控量测及分析工作对于确保隧道的施工安全、支护的经济合理,以及获得可靠的设计参数起到关键作用。