考虑时间效应的围岩特征曲线

 应用非线性粘弹性模型, 对围岩特征曲线随时间的变化进行了有限元计算分析, 并对 初始模量、强度围压比的影响, 以及岩石破坏后特征、强度载荷速度效应与围岩特征曲线之 间的相互关联进行了讨论。另外, 针对弹性支护的情况, 通过支护反力曲线的计算, 对围岩 特征曲线与支护反力曲线之间的相互关系进行了讨论和分析。本文所用的非线性粘弹性模 型, 能够较好地再现岩石的应力2应变曲线。应用能够描述应变软化(屈服和破坏) 和非线性粘 弹性特征的本构方程式来计算和分析围岩特征曲线, 则是本研究的特色和创新所在。     

锚杆加固作用下圆形隧道复合岩体围岩特征曲线解析方法研究

传统收敛约束法中通常将锚杆作为支护结构求解独立的支护特征曲线,但是锚杆无法构成单独的支护体系,需和围岩共同作用形成承载体系。基于隧道开挖弹塑性力学解析解,考虑锚杆对围岩的加固效应,通过均匀化方法,推导了锚杆加固作用下的圆形隧道复合岩体围岩特征曲线解析解。将所推导的解析解与数值计算结果进行对比,结果表明:推导的锚杆加固作用下复合岩体围岩特征曲线解析解与FLAC~(3D)计算结果吻合较好,说明将锚杆与围岩作为复合承载体系是合理的,同时说明该方法的准确性。通过对比有无锚杆支护状态下的围岩特征曲线,说明了锚杆对围岩变形具有较好的控制作用。该解析解考虑锚杆的预应力和支护时机,为锚杆加固作用下的隧道稳定性分析提供了相对简单快速的计算方法。     

围岩–支护作用机制评述及其流变变形机制 概念模型的建立与分析

 岩石地下工程支护理论的核心问题是围岩–支护相互作用机制。首先,分析卡斯特纳方程和围岩–支护作用机制存在的缺陷和错误,包括：(1) 模型对支护反力的产生及其支护时机、加载路径等力学处理不具有工程实际意义。(2) 由卡氏方程和弹塑性公式推导的围岩特性曲线在工程实际中不存在,因此也不存在与支护结构的支护特性曲线相交的可能性。(3) 将围岩特性曲线和支护特性曲线相交求解围岩–支护相互作用的平衡点存在概念及逻辑上的错误。然后,建立基于流变变形的围岩–支护相互作用机制的概念模型。最后,应用流变机制概念模型对工程实例进行计算,推演围岩与支护的相互作用过程,从理论上证实混凝土结构在一定条件下支护软岩巷道是可以的。提出的流变机制概念模型,既可以对围岩–支护相互作用给出定性解释,也可以应用于岩石地下工程的设计,理论基础可靠,能够应用于工程实践。     

基于Duncan–Fama收敛曲线的隧道结构安全系数计算

首先基于Duncan–Fama收敛函数及锚杆、喷射混凝土与金属网等支护单元特征函数,建立圆形巷道围岩收敛–约束关系曲线,同时建议非圆形断面巷道转化为圆形断面的适用方法,并剖析收敛–约束曲线所涵盖的围岩与支护体系间的动态发展关系。然后引入隧道洞壁径向位移沿隧道径向的开挖间隔的变化规律曲线,与收敛–约束曲线相结合从而共同形成岩体的开挖、支护与信息反馈的动态发展关联过程。最后,建议了隧道围岩稳定安全系数计算表达式,探讨了相关支护时机确定方法,并分析隧道开挖后其支护起始位置对围岩约束力的影响。基于上述成果,探讨了现有的根据岩体分级类比的地下结构支护设计方法不能定量评价其安全程度的缺陷。通过两个工程实例,详细说明所构建方法的操作和运行过程,并初步验证了其有效性。     

基于收敛-约束原理的地下结构稳定性分析

基于Hoek-Brown岩体失效准则,根据开挖空间围岩变形压力与收敛的关系,导出了圆形隧道围岩荷载计算公式,然后利用隧道非规则断面等价圆算法,将其拓展成任意断面隧道围岩荷载确定方法。在分别建立起锚杆、喷射混凝土及钢拱架等支护单元特征函数的基础上,基于并联模型导出了锚喷组合支护结构刚度、抗力计算公式。根据开挖面的空间效应建议了支护特征曲线起点确定方法。利用上述成果,结合收敛-约束原理构建了支护结构稳定性系数计算方法,克服了基于岩体分级类比的地下结构支护设计方法不能定量评价其安全程度的缺陷。通过案例分析,示范了所构建方法的操作和运行过程,并初步验证了其有效性。     

Analysis of structural interaction in tunnels using the covergence–confinement approach

The rock-support interaction in tunnels is studied through the use of the convergence–confinement method. The equations that characterize the behaviour of the most important support types are given together with a set of conceptual interaction schemes. As far as the behaviour of the support is concerned, reference is made to the ultimate limit state concept, which is widely used in civil engineering. This approach is linked to the classical convergence–confinement method. The interaction between the temporary support system and the final lining is dealt with, and the noteworthy case of presupport ahead of the face, followed by a further internal support (usually steel sets and shotcrete) is also included. Finally, the ‘ground reaction curve of the reinforced tunnel’, which allows one to analyse the interaction between the reinforcement around the tunnel and supports, is introduced.     

膨胀性黄土隧道钢拱架–格栅联合支护力学特性研究

为了研究膨胀性黄土隧道围岩与支护结构作用机制,解决膨胀力作用下的隧道支护难题,利用弹性薄壳理论建立了联合支护的力学分析模型,引入等效截面法和膨胀力参数得到了改进的围岩–支护特征曲线。基于上述模型和方法,对该黄土隧道初期支护的力学特性进行分析,提出适用于膨胀性黄土隧道的"格栅拱架+钢拱架+喷射混凝土"联合支护方式。结果表明:所建立的模型和方法对膨胀围岩条件下初期支护的力学特性分析具有较好的适用性,从理论角度解释该隧道原始初期支护发生破坏的原因;与"钢拱架+喷射混凝土"和"格栅+喷射混凝土"支护方式相比,提出的联合支护方式在膨胀性黄土隧道中更具优势,充分发挥了不同材料的承载特性,保证了隧道的稳定性。     

Analytical computation of support characteristic curve for circumferential yielding lining in tunnel design

Circumferential yielding lining is able to tolerate controlled displacements without failure,which has been proven to be an effective solution to large deformation problem in squeezing tunnels.However,up to now,there has not been a well-established design method for it.This paper aims to present a detailed analytical computation of support characteristic curve(SCC)for circumferential yielding lining,which is a significant aspect of the implementation of convergence-confinement method(CCM)in tunnel support design.Circumferential yielding lining consists of segmental shotcrete linings and highly deformable elements,and its superior performance mainly depends on the mechanical characteristic of highly deformable element.The deformation behavior of highly deformable element is firstly investigated.Its whole deforming process can be divided into three stages including elastic,yielding and compaction stages.Especially in the compaction stage of highly deformable element,a nonlinear stress-strain relationship can be observed.For mathematical convenience,the stress-strain curve in this period is processed as several linear sub-curves.Then,the reasons for closure of circumferential yielding lining in different stages are explained,and the corresponding accurate equations required for constructing the SCC are provided.Furthermore,this paper carries out two case studies illustrating the application of all equations needed to construct the SCC for circumferential yielding lining,where the reliability and feasibility of theoretical derivation are also well verified.Finally,this paper discusses the sensitivity of sub-division in element compaction stage and the influence of element length on SCC.The outcome of this paper could be used in the design of proper circumferential yielding lining.     

曲线连续桥梁设计要点浅议

指出曲线连续桥梁目前已被广泛应用于城市互通立交以及高等级公路互通立交中,由于各种因素的限制,使得这类桥梁表现出弯、斜、异形等特点,文中将重点介绍曲线连续弯桥的受力特点以及设计过程中应注意的一些问题,并提出一些相应的解决措施。     

Effects of characteristic parameters of isolation system on seismic response of isolated nuclear power plants

Seismic isolation is increasingly being used in both traditional and industrial structures for its ability to reduce structural responses while effectively protecting systems and components, such as machinery. After applying isolation, the standardize design can be achieved during seismic design of nuclear power plant. However, the seismic response of nuclear structure with different isolation characteristic parameters under different ground motions has not been fully studied. In this paper, a new generation passive nuclear power plant model was simulated with finite element method. The acceleration response, deformation, seismic mitigation efficiency, and response discreteness of nuclear structures with different isolation characteristic parameters were analyzed. The effect degree of isolation characteristic parameters on seismic response of nuclear structures was investigated. Performance spaces are introduced as an alternate method for evaluating responses of nuclear structures. The results show that isolation systems largely reduce both the mean value and discreteness of seismic response of nuclear structures.     

On the hydraulic behavior of unsaturated nonwoven geotextiles

Geotextiles have been widely used in soil structures for separation, filtration, reinforcing, and drainage. They are often used to provide reinforcement and drainage for retaining walls and embankments. It has been reported, however, that geotextiles may not drain water as effectively as was initially expected. In this study, published data on the hydraulic properties of unsaturated geotextiles are compiled and analyzed in order to highlight the hydraulic characteristics of unsaturated geotextiles.

The application of the van Genuchten equations originally developed for the water characteristic curve and the hydraulic conductivity curve of unsaturated soil to unsaturated geotextiles is then examined and discussed. Finally, the drainage from a one-dimensional sand column having a horizontal geotextile layer was analyzed using the finite element method and the van Genuchten equations to assess the utility of this procedure for further study of unsaturated/saturated water flow within the soil–geotextile system.     

Ground reaction curves for tunnels excavated in different quality rock masses showing several types of post-failure behaviour

Rock mass behaviour model selection and, in particular, rock mass post-failure behaviour are key issues in analysing tunnel stability, in particular in terms of the correct application of design techniques such as the convergence–confinement method and also numerical modelling. Three different quality rock masses (good, average and poor) were defined in which simulated standard tunnels were excavated. Different behaviours – including elastic perfectly plastic, elastic brittle and three strain softening behaviours – were modelled for each type of rock mass and increasingly realistic parameters were calculated, along with the corresponding ground reaction curves. The results obtained demonstrate the importance of adequate post-failure behaviour model selection for tunnel analysis. Also assessed are the effects of the standard support and reinforcement.     

压实高岭土干燥收缩特性试验

为研究初始干密度和初始含水率对高岭土干燥收缩行为的影响,探究其干燥收缩机理,采用数字图像相关法来测量环刀试样的径向变形,在设计的干燥收缩试验平台进行了一系列干缩试验,结合试验得到的收缩曲线和相应的土水特征曲线获得吸应力固结曲线。结果表明:饱和高岭土大部分收缩变形发生在进气点之前的饱和状态;试样在干缩过程中以径向变形为主,表现出比较明显的各向异性,这种各向异性的变形特性随初始饱和度的增加而减弱;随着初始干密度增大,试样干燥收缩稳定所需要的时间逐渐减小,稳定时的体积变形也相应减小,然而试样的初始干密度和饱和度对收缩变形稳定时的含水率几乎没有影响;吸应力固结曲线与饱和土的等向固结曲线近似重合的曲线形态表明吸应力和净平均应力对土收缩变形的作用效果是一致的;在等向应力条件下,有效应力是影响土体干缩变形的决定性应力;提出的结合干燥收缩试验和等向固结试验曲线的间接测量土水特征曲线的方法是相对可靠的。     

Ground behaviour analysis,support system design and construction strategies in deep hard rock mining-Justified in Western Australian's mines

Development of deep underground mining projects is crucial for optimum extraction of mineral deposits.The main challenges at great depth are high rock stress levels,seismic events,large-scale deformation,sudden failures and high temperatures that may cause abrupt and unpredictable instability and collapse over a large scale.In this paper,a ground control and management strategy was presented corresponding to the three stages of projects:strategic design,tactical design and operational design.Strategic design is results in preparing a broad plan and primary design for mining excavations.The tactical design is to provide detail design such as stabilisation methods.Operational design stage is related to monitoring and updating design parameters.The most effective ground control strategies in this stage are maintenance,rehabilitation,monitoring and contingency plan.Additionally,a new procedure for design of ground support systems for deep and hard rock was proposed.The main principles are:static and/or dynamic loading types,determination of loading sources,characterisation of geological conditions and the effects of orientation of major structures with openings,estimation of ground loading factor,identification of potential primary and secondary failures,utilisation of appropriate design analysis methods,estimation of depth failure,calculation of the static and/or dynamic demand ground support capacity,and selection of surface and reinforcement elements.Gravitational force is the dominant loading force in low-level stresses.In high stress level failure mechanism becomes more complex in rock mass structures.In this condition,a variety of factors such as release of stored energy due to seismic events,stress concentration,and major structures influence on ground behaviour and judgement are very complicated.The key rock engineering schemes to minimise the risk of failures in high-stress levels at great depth involve depressurisation and quality control of materials.Microseismic and blast monitoring throughout the mining operations are required to control sudden failures.Proper excavation sequences in underground stopes based on top-down,bottom-up,centre-out and abutment-centre were discussed.Also,the performance of a ground support system was examined by field observation monitoring systems for controlling and modifying ground support elements.The important outcome of the research is that the proposed procedure of selecting ground support systems for static and dynamic situations was applied in several deep underground mines in Western Australia.Ground behaviour modes and failure mechanism were identified and assessed.Ground demand for static and dynamic conditions was estimated and an appropriate ground support system was selected and evaluated in site-specific conditions according to proposed method for ground support design at great depth.The stability of rock masses was confirmed,and the reliability of the design methodology for great depth and hard rock conditions was also justified.     

软弱围岩隧道钢纤维混凝土衬砌承载特性模型试验研究

为满足软弱围岩隧道开挖后尽快封闭岩面、适应一定变形及提供足够支护力的要求,通过素混凝土、钢筋混凝土及钢纤维混凝土衬砌力学行为室内模型试验,对钢纤维混凝土衬砌的承载特性进行研究。研究结果表明:钢纤维混凝土衬砌初裂荷载提高了20%,极限荷载得到较大提高;掺入钢纤维后衬砌结构韧性增强,初裂后仍能抵抗一定变形并较大降低变形速率,与素混凝土、钢筋混凝土相比可承受更大的变形;钢纤维混凝土衬砌初裂后承载特性曲线缓慢上升,至2倍初裂荷载时仍无收敛迹象,素混凝土快速收敛,钢筋混凝土在一定缓慢上升后快速趋于收敛,软弱围岩条件下,钢纤维混凝土初支在一定变形后可与围岩特征曲线相交,达到围岩–结构稳定状态,是一种力学性能良好的快速支护材料。研究成果对软弱围岩隧道的设计与施工都具有重要的意义。     

剪切刚度层模型恢复力特性骨架线的简化计算法

本文提出了确定剪切刚度层模型恢复力特性骨架线的简化计算法。以北京国贸中心高层钢结构为例，用简化法和弹塑性荷载增量法计算了层恢复力特性骨架线，用这两种骨架线进行了弹塑性时程分析，两者的结果比较接近。简化法确定的骨架线适用于高层建筑钢结构在大震作用下的安全验算。     

管网叠压供水系统的水泵适用性分析

从离心水泵性能分析入手，根据管网叠压供水系统中水泵工况点的分布情况，提出了管网叠压供水系统中水泵的适用性问题，并给出了水泵高效运行的技术参数范围及其确定方法。系统最不利工况点相对于特性曲线的位置对水泵的适用性有着重大影响，愈靠近高效段的右端点，水泵适用的流量范围愈大而扬程范围愈小；愈靠近高效段的左端点，适用的流量范围愈小而扬程范围愈大。在水泵选型和运行调度都合理时，管网叠压供水系统才可取得预期的节能效果，小流量条件下需辅以气压给水技术或其他措施以达到节能目的。     

Determining the principles of tunnel support based on the engineering geological behaviour types: example of a tunnel in tectonically disturbed heterogeneous rock in Serbia

A methodology for designing a tunnel support system according to the actual ground conditions and the critical behaviour types is analysed in this paper. The methodology is justified with the principles of the New Austrian Tunnelling Method that incorporates the top heading and bench method. The role of the geological material and its implication in tunnel design, reinforced with advances in site investigation methods, cannot be based solely on the development of the geotechnical classification systems and the consequent quantification of the rock masses. Support requirements for rock masses with equal classification ratings can be different. The procedure presented in this study cannot bypass the geological and/or in situ characteristics dictating or influencing the tunnel behaviour compared with a standardised classification that could miss the specifics and particularities of and around a tunnel section. The step-by-step procedure is applied in a tunnel excavated in tectonically disturbed heterogeneous flysch sediments in Serbia. The complex structure of these materials, resulting from their depositional and tectonic history that includes severe faulting and folding, presents a challenge to geologists and engineers. The possible ground types are evaluated, and then, combined with the factors of the tunnel geometry, the primary stress condition, and the water conditions, several behaviour types are considered. These classified behaviour types, followed by the suitable mechanical properties that are required for effective tunnel engineering design, are the basis for the numerical design of the appropriate primary support measures to achieve stable tunnel conditions. The twin-tube, two-lane highway tunnel was successfully constructed without significant problems.

     

钢筋混凝土柱弯矩-转角骨架线特征点及性能点转角研究

基于不同抗震等级钢筋混凝土（RC）柱拟静力试验研究,建议了RC柱四折线弯矩 转角(M-θ)骨架线。采用规范公式计算得到的RC柱的正截面承载力作为M-θ骨架线的峰值弯矩M_p,0.8M_p作为M-θ骨架线名义屈服点弯矩,下降至0.8M_p及0.75M_p（不考虑P-Δ效应）分别作为M-θ骨架线极限点的弯矩及失效点的弯矩,根据继续使用性能点IO及生命安全性能LS的转角表达式,分别确定其弯矩为0.9M_p及下降至0.925M_p。基于由OpenSEES数值计算得到的按规范最小配箍特征值配置箍筋的22根RC柱的水平荷载 位移（F-Δ）滞回曲线得到的M-θ骨架线,确定了RC柱四折线M-θ骨架线特征点及性能点的转角,确定的转角与试验值符合较好;对于生命安全性能点LS、避免倒塌性能点CP及失效点的转角,当轴压比为0.5时,其与美国标准的规定基本一致,当轴压比为0.9时,其大于美国标准的规定。提出了RC柱的损坏程度与其M-θ骨架线特征点及性能点转角的关系,可用于判别地震作用下RC框架柱的损坏程度以及是否达到其预定的抗震性能目标。     

基于中国规范的近断层区抗震设计谱研究

采用211条脉冲型地震动计算得到了保证率分别为50%(平均谱)和84%(平均谱+1倍标准差谱)的近断层地震动反应谱,将得到的反应谱与GB 50011—2010《建筑抗震设计规范》中推荐的近断层区设计谱进行了比较。结果表明,我国抗震规范中针对近断层区给出的设计谱幅值调整方法不能保证近断层区的结构具有足够的安全性,表现为调整后的设计谱值在某些周期段上仍小于实际的近断层地震动反应谱值。根据比较结果,提出了基于我国抗震规范设计谱形式的近断层区抗震设计谱修正方法,通过提高设计谱幅值和限制特征周期最小值来实现修正,将我国抗震规范中的设计谱幅值增大1.5倍、特征周期下限取0.75s(多遇地震)和0.80s(罕遇地震),所提的近断层区抗震设计谱,保证率可达到84%。所提出的抗震设计谱及变形验算的设计建议简单且易于在工程中使用,研究结果可为近断层区的结构抗震设计提供参考。