Reliability analysis of roof wedges and rockbolt forces in tunnels

The ambiguous nature of the factor of safety is first discussed in the context of a symmetric roof wedge of a circular tunnel, where two different definitions of the factor of safety are shown to be reconcilable when using the reliability index computed with the first-order reliability method (FORM). The probabilities of failure based on the second-order reliability method (SORM) are also obtained for comparison with those of FORM and Monte Carlo simulations. The FORM and SORM analyses are then applied to a circular tunnel supported with elastic rockbolts in a homogeneous and isotropic elasto-plastic ground with the Coulomb failure criterion. The similarities and differences between the ratios of mean values to design-point values, on the one hand, and the partial factors of limit state design, on the other hand, are discussed. Finally, all this is used to show how a reliability-based design can be performed to obtain the length and spacing of rockbolts for a target reliability index.     

Numerical analysis to better understand the mechanism of the effects of ground supports and reinforcements on the stability of tunnels using the distinct element method

In order to understand the mechanism of the effects of ground supports and reinforcements on tunnel stability, numerical simulations are conducted using the distinct element method. Four cases of simulations are carried out in this paper for tunnels excavated in a sandy ground to investigate the effects of (1) dowels and a lining on a single tunnel, (2) dowels and a lining on two parallel tunnels, (3) forepoling and face bolts on a single tunnel face, and (4) forepoling and face bolts on two tunnels which face each other. It is found that the use of ground supports causes a discontinuous ground to behave as a continuous one. In addition, it is revealed that supports help to form ground arches in the sandy ground. Detailed discussions are given considering the stress paths and the stress distributions.     

江西洞天福地景观营建智慧

洞天福地是道教的理想修行地,也是人居环境的理想模型。依据历史影响力及现今建设现状,选取江西6处代表性洞天福地进行实地调研,分析江西洞天福地在选址、理景两方面所蕴含的独特景观营建智慧,得出:江西洞天福地一般位于盆地,并以江西形势派风水理论为指引;绝大部分洞天福地借鉴壶天仙境来营造仙界景观,整体空间布局模式为:山门——"壶口",道教建筑所在盆地——"壶腔",沿山势曲折上升的山道沟通内外,并呈现出"虚(水)实(山)结合"的特点;植物配置具有浓重的道教色彩,且以常绿乡土古木为基调,寓意万物共生;建筑营建深受"仙道意识"影响,仙境信仰影响了建筑营建思想,仙灵信仰影响了建筑装饰艺术。通过研究洞天福地所蕴含的道教哲学思想,总结出有益于现代社会健康发展的积极处世观、生态发展观、养生观及物种保护观。     

Rating of wall and roof sections—Thermal considerations

Several parameters are in vogue which provide the comparative thermal performance of wall and roof sections. They are either based on steady state heat conduction or do not respond to changing conditions of climate, design and usage. A criteria based on inside surface temperature and peak heat gain, for unconditioned and conditioned buildings respectively, of wall and roof sections has been suggested in this paper.

The parameter known as thermal performance index (TPI) provides the relative thermal rating of several combinations of different layers of building materials of varying thickness and thermophysical properties. For the selection of a particular combination for summer period the lower the value of TPI better shall be the thermal performance. The data has also been classified depending on the range of TPI and class B has been found the most acceptable range both from thermal as well as economic point of view.

The TPI values of prevalent combinations, single and multilayer, have been worked out for a representative climate. Some of data is presented in this paper. The data finds wide acceptability in field application and has been included in Indian Standard code of practice.     

体育场罩棚倾角及连接开缝对风荷载的影响

为了满足造型和功能需要,体育场的罩棚倾角常常根据具体条件而变化,罩棚上扬、下俯均有所应用.通常罩棚与看台顶部留有环通的空隙,有利于场内通风,但也有一些场馆未留空隙.特殊的体型将对罩棚的风荷载产生影响,本文针对罩棚倾角变化和连接开缝情况两种因素对罩棚表面风压分布的影响进行了CFD数值模拟,给出了风压系数的变化规律,并与风洞试验结果进行了比较.     

A methodology for studying the high wall displacement of large scale underground cavern complexes and it’s applications

A great number of numerical simulations of multiple schemes were conducted to investigate the stability of underground cavern complexes in three representative hydropower stations in China. The purpose was to study the displacement law of side walls of underground openings under different conditions. In the calculation, four major typical rocks, four overburden thicknesses, and five geo-stress conditions were taken into account. The best-fit formulae to predict the displacement of key points on the side walls of underground openings were obtained by using the dimensionless technique. The formulations can describe the effects of rock quality, overburden thickness, horizontal in situ stress, the height of the power house and the spacing between openings. The formulation/methodology was used to predict the side wall displacements of nine underground complexes in China. A comparison analysis showed that the predicted values were in close agreement with those obtained by field measurements and by back analysis.     

低矮建筑风致局部瞬毁诱发次生灾害机理研究

基于缩尺比为1∶40低矮建筑在不同地貌条件下的风洞试验,研究因易损区局部风致破坏进而诱发低矮建筑屋面整体风毁的风载特性,分析屋面瞬间开孔所致瞬态峰值内压过冲效应,研究稳态阶段的内压分布特征及净风压极值分布规律。结果表明：建筑上游风场湍流度越大,屋面局部瞬间破坏所致过冲效应越明显;地貌对屋面迎风角部瞬间破坏所致过冲较分布区域的影响显著;屋面不同的区域开孔所致内压分布均匀,但内压值随风场湍流度增大呈增大趋势。风致建筑破坏所致内压系数试验值比我国现行荷载规范中建议取值大;屋面局部瞬毁进而诱发再次破坏主要分布在已损孔洞边缘及山墙部分。     

深井复合顶板煤巷变形机理及控制对策

针对深部高应力条件下复合型顶板煤巷的大变形问题,以江西曲江煤矿为例进行了现场调查、理论分析和工业试验等研究。首先,经现场调查发现该矿表现出了典型“三高”矿井的特点,加上顶板锚索和两帮锚杆无法充分发挥作用,使整个巷道支护系统失去平衡而发生破坏。然后,研究了深部高应力工作面煤巷的力学作用,认为该力学作用是一个渐进过程,其变形动力主要来自于巷道顶板压力,底板变形大是直接导致整个巷道系统失效的重要标志;另外,根据深部高应力复合型顶板煤巷的受力特征,建议应将顶板的控制作为关键部位,尽力维护顶板的完整性,提高岩层自承能力,使支护结构与围岩能够协调地工作,并提出了以“预应力桁架锚索”为主体,以“锚杆+锚索+钢筋网等支护”为辅助的综合控制技术。实践证明：经以“预应力桁架锚索”为主体的综合控制技术支护后的巷道,其变形较原支护有明显好转;监测数据表明：经91 d后,巷道两帮的相对收敛速率小于1.7 mm/d,而且顶底板的相对收敛量大大减少,最大值为297 mm,变形速度小于1.4 mm/d,处于稳定状态。     

Soil erosion by rainfall and runoff—state of the art

The processes of soil detachment and sediment transport by rainfall and overland flow and resulting sediment transport are described. The results of past research on the role of raindrop impact in detaching soil, experimental studies of erosion, and erosion modelling are presented. Studies of soil loss from experimental field plots led to the development of the Universal Soil Loss Equation and to its subsequent modification for use in quantifying erosion by individual storms. Systems to produce rainfall for erosion studies in the laboratory are described. A system which is currently being calibrated and used for erosion control system testing at Drexel University's Geosynthetic Research Institute (GRI) is described. Preliminary spatial rainfall distributions and runoff measurements are presented. Experimental results obtained by others on the performance of natural and geosynthetic erosion control systems are discussed along with a proposed experimental program for the GRI system.     

引气剂稳泡机理及其改善混凝土冻融耐久性能的研究

利用膜天平对比了两种引气剂YQJ和改性松香R在空气-水界面的单分子膜的强度，考察了掺加这两种引气剂的新拌混凝土性能和硬化混凝土的冻融耐久性能。结果表明，引气剂在空气-水界面上的单分子膜的强度直接决定了引气剂的稳泡性能。稳泡性能优异的高性能引气剂，可显著提高混凝土的冻融耐久性能。     

西南某水电站地下厂房顶拱衬砌裂损机理探讨

通过对水电站地下厂房顶拱衬砌裂损进行分析探讨,揭示了衬砌裂损的机理,并指出开挖过程中,顺层岩体的顺层滑移产生偏压是主要原因,提出了初步的修复措施,以提高地下厂房围岩岩层的抗弯刚度及强度。     

Treatment of oil well “produced water” by waste stabilization ponds: Removal of heavy metals

Oil well produced water (PW) can serve as an alternative water resource for restricted halotolerant agricultural purposes if the main pollutants, hydrocarbons and heavy metals, can be removed to below the irrigation standards. In this work, the potential removal of cadmium(II), chromium(III) and nickel(II) from PW by chemical precipitation in biological treatment was evaluated. Precipitation as a sulphide salt was found to be a very effective mechanism, which together with biosorption, biological metal uptake, precipitation as hydroxides and carbonates could remove heavy metals down to below irrigation standards. The existence and capability of these various mechanisms was demonstrated in the performance of a continuous artificial pond followed by intermittent sand filter, achieving removals of around 95% for nickel(II) and even higher removal rates for cadmium(II), chromium(III) from artificial PW after the installation of an anaerobic stage. The treated effluent quality was higher than that required by current European standards.     

Effect of water and geological factors on the long-term stability of fracture zones in the Päijänne Tunnel, Finland: a case study

Potable water to the Helsinki metropolitan area in Finland is conveyed through Precambrian bedrock along the mostly unlined, rock-surfaced Päijänne Tunnel which has been in use since 1982. Two cave-ins in recent years and the damage observed during the inspection preceding the repair of the northern 64 km of the tunnel in 2001 demonstrates the active eroding processes. The extent of block falls inside the tunnel, interpreted from a recording made by a submersible robot, is compared with both measured and semi-quantitatively documented groundwater inflow and characteristics of fracture zones intersecting the tunnel that commonly appear as linear depressions in topography.Most of the damage observed in the tunnel is inferred to result from weathering, swelling clays, erosion and changes in groundwater or pressure conditions. The main factor in triggering these physical and chemical changes is water that flows both along the tunnel and in the fractures of the surrounding bedrock. Foliation sub-parallel to the tunnel orientation seems to be a factor making tunnel sections more prone to the occurrence of block falls.A high rate of groundwater inflow correlates to some degree with the level of original reinforcement. Even though groundwater inflow does not necessarily indicate support need, increased fracturing in bedrock generally provides more flow paths to water. Hydraulic properties of fracture zones are inferred to contribute to the deterioration in the tunnel but probably as a relatively minor factor compared with the rock support solutions and structural orientation sub-parallel to the tunnel. The orientation of fractures is inferred to play a role as variation is observed in inflow when linked with the strike of the fracture zone. The damage concentrates to zones of existing weakness and sections that have not been lined with shotcrete. Shotcrete prevents leaching of fracture fillings which can lead into loosening and falling of key-blocks. The application of steel-supported reinforcement in the fractured sections is a plausible explanation to why no consistent connection was observed between the occurrence of large block falls and fracture zone intersections. The impairment of the tunnel's condition, revealed during the repair inspection, is considered to have been influenced by the initially low level of reinforcement.     

Building disputes settled by litigation — Comparison of Australian and UK practice

In this second paper, the authors have obtained data from 60 building cases tried in the Supreme Courts of New South Wales and Victoria during 1990 and 1991 and from 60 cases heard in the Court system of the United Kingdom.     

谈屋顶绿化引发防水材料发展及愿景

针对国内外绿色建筑发展的迫切需求,以及现阶段大量屋顶绿化的出现,分析了屋顶绿化对于建筑屋面防水材料的性能要求、存在问题、现阶段的解决方式等,并结合抗裂硅质防水剂材料提出了相应的实施对策,同时对我国绿色屋顶建设和防水材料发展进行了展望,以推进屋顶绿化工程的快速发展。     

Mathematical analysis of the chemical system “cyanide-heavy metals” in water—determination of components and toxicity of the system—II. Solution by computer

An essentially new method of chemical analysis was developed and named “the non-experimental chemical analysis”. The subject of the method is the qualitative and quantitative analysis of chemical properties of the system of complex forming reagents and central atoms. The method is based on the application of the general system equation. An application of the general system equation for the toxic system “cyanide-heavy metals” in water solutions is advanced.     

Influence of faulting on a mine shaft—a case study: part I—Background and instrumentation

The impact of geological structures on the stability of underground infrastructures is well recognised. Moreover, the influence of major geological structures such as faults, becomes critical when the stability of underground infrastructures which are essential for mine production, are threatened. The X41 shaft is the man and supply shaft at the Copper Mine, at Mount Isa, Australia. Here, there has been observed evidence of degradation manifested by the development of cracks in the shaft concrete lining since the early nineties. In addition, the shaft steel structure is being deformed and needs regular and meticulous maintenance. The shaft degradation has been attributed to the presence of two major geological structures, the W41 and W42 faults, which intersect the shaft in two distinct locations.This paper presents a case study whereby the causes of shaft degradation were examined. The influence of faulting and mining sequence on the stability of the main mine shaft were investigated by means of field investigations and numerical modelling. This paper concentrates on the field investigation performed as part I of this project. It provides a review of work done prior to this study and exposes the past field monitoring practices and those that were implemented to characterise the observed displacement in the X41 shaft.     

A hybrid optimization mechanism for constructing a dynamic simulation system—An operational behavior analysis of a moving scaffolding system

Standardized production processes in the construction industry can reduce uncertainty, cost and time. The Movable Scaffolding System (MSS), a new bridge construction technique, facilitates automated operations at a high rate. In an MSS, highly repetitive mechanical operations make issues of supply and allocation of machinery and raw materials extremely important. We use Simprocess, a computer simulation software package, to construct hierarchically standardized models of MSS bridge engineering operations (MSSBEO), which encompass bridge superstructure and substructure production, procurement, storage and transmission of raw materials, and utilization of nonconsumable resources such as machines, tools and human resources. We also present a novel dynamic simulation model with a novel fuzzy inference-based optimization mechanism for multiobjective optimization that can identify the optimal resource-allocation strategy under dual goals of minimized time and cost in the MSSBEO model. We analyze the MSSBEO model using the proposed optimization system and use a case study to verify the accuracy and applicability of the proposed system. Through the human decision-making module, optimized resources allocation strategies can be quickly searched to meet actual conditions and enhance the academic value and application of the optimized resource combinations. The most suitable resource combination for an actual situation is generated by applying the proposed optimization module with the fuzzy inference mechanism. After model testing, the optimized resource combinations obtained using the proposed optimization module enhance the utilizations of each resource and reduce the overstocking of materials in the simulation to achieve the goals of reduced cost, efficient work schedules and enhanced productivity.     

Exploitation of developed coal mine pillars by shortwall mining—a case example

The shortwall mining technique is similar to longwall mining but with shorter face lengths, ranging between 40 and 90 m, with the aim of controlling the caving nature of the overlying upper strata, the load on support and the overall operation of the supports applied at the face. Field observations and three-dimensional numerical modelling studies have been conducted for the longwall panel extraction of the Passang seam at Balrampur Mine of SECL to understand the caving behavior of the overlying upper strata. A large area of the Passang seam adjacent to the longwall panels has already been developed via bord and pillar workings. In this paper, numerical modelling studies have been conducted to assess the cavability of the overlying strata of the Passang seam in the mine over developed bord and pillar workings along with the support requirement at the face and in the advance gallery. The caving nature of the overlying rocks characterized by the main fall is predicted for varying face lengths, strata condition and depths of cover. The support resistance required at the face, the load in the advance gallery and its optimal obliquity were estimated for faster exploitation of the developed pillars in the Balrampur mine by shortwall mining.     

Optimization — the basis of code-making and reliability verification

As early as 1971 Rosenblueth and Mendoza (Rosenblueth E, Mendoza E. Reliability optimization in isostatic structures. J Eng Mech Div, ASCE 1971;97(EM6):1625–42) published a paper on structural optimization the concepts of which have been refined later by Hasofer in 1974 (Hasofer AM. Design for infrequent overloads. Earthquake Eng and Struct Dynamics 1974;2(4):387–8) and Rosenblueth in 1976 (Rosenblueth E. Optimum design for infrequent disturbances. J Struct Div, ASCE 1976;102(ST9):1807–25) particularly in the context of earthquake resistant design. In essence, these authors proposed to distinguish between structures that can fail upon completion or never and structures which can fail under rare ‘disturbances’. Furthermore they distinguished between ‘single mission structures’ and structures which are systematically rebuilt after failure. The consequences of their findings for code making, especially for setting safety targets apparently have been overlooked since then. In fact, it is rather a yearly failure rate that has to be specified and verified and not a failure probability for an arbitrary reference time. The paper thoroughly reviews Rosenblueth's and Hasofer's developments and extends the concepts to failures including ultimate limit state failure under normal and extreme conditions, serviceability failure, fatigue and other deterioration and, finally, obsolescence. Some newly needed computational tools are addressed. Partial safety factors are derived for stationary failure processes and a new verification format for fatigue and other deterioration is proposed. Tools for optimization of structural components are presented.