Influence of faulting on a mine shaft—a case study: part II—Numerical modelling

The X41 shaft is the man and supply shaft at Copper Mine, Mount Isa, Australia. 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.Since the X41 shaft gives a direct access to the Copper Mine, it has to remain operational for the mine life. An objective of this study was to gain a better understanding of the mechanisms inducing damage to the shaft. In order to assess the long-term integrity of the shaft, it was essential to evaluate the impact of its deformation, related to the late mining status of the Copper Mine and the presence of the two major faults. It was important to determine an estimate of the future rate of displacement, as well as the total displacement, for the rest of the mine life.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 numerical modelling performed as part II of this project. It presents exhaustively the methodology used to build the numerical model and presents the outcomes.     

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 case study on ground treatment for a rock tunnel with high groundwater ingression in Taiwan

This paper presents a case study on the collapse caused by sudden groundwater ingression in the Pinglin pilot tunnel, and the treatments developed for the adverse ground conditions encountered. The ideas for the ground treatment are to reduce groundwater pressure as well as to consolidate the fractured zone in rock formations. The paper highlights the importance of paying particular attention to the ground treatment process and grouting quality control. Ongoing adjustments of grouting mixture and pressure may be necessary with the changing ground conditions.     

Influence of geometry and material properties on the axial vibration of a rock bolt

A continuous dynamic model for the axial vibration of a rock bolt system is presented. The model comprises three sections: the fixed length, bonded into the rock, the free length, which is not coupled to the rock, and the protruding length, which extends beyond the rock. The head assembly is modelled as a discrete mass and a spring, and a further discrete mass is included, representing a testing device that can be attached to the protruding end. Each section is modelled as a continuous elastic rod governed by the wave equation, with suitable compatibility conditions applied between the sections and boundary conditions, which also account for the effect of the discrete components, applied at the ends. Solutions in non-dimensional form are substituted into the boundary conditions to allow the natural frequencies to be calculated, and it is shown that two possible solutions for the mode shapes can be used for the fixed length—an exponential solution or the classical sinusoidal solution—depending on the stiffness of the grout relative to that of the bar. The conditions for which the two solutions are valid are developed, and changes in the frequency ratio with changes in length ratio, and the stiffness ratios of the grout and the anchor head relative to the stiffness of the fixed length of the anchorage are examined. Generally, the state of a bolt after installation is unknown and this does not provide proper assurance of the safety of the structure for which the bolts are used. The model provides a viable tool for helping to assess the condition of the bolt by using the natural frequencies associated with areas of the bolt of particular interest, e.g. the free length. The results show how the changes in the stiffness and/or length ratios affect the dynamics associated with fixed length of the bolt and the quality of the bonding installation. A case study is presented showing how the model can be used effectively to interpret real data.     

Pillar design by combining finite element methods, neural networks and reliability: a case study of the Feng Huangshan copper mine, China

This paper presents a mine pillar design approach by combining finite element methods (FEMs), neural networks (NN) and reliability analysis. This practical approach is presented by examining an actual cylindrical mine pillar in a copper mine and taking into account uncertainties in ore pillar material parameters including modulus, Poisson's ratio, density and uniaxial compressive strength. The ore pillar had to be able to safely and effectively support a drilling room that occupied an open space of 3.8 m high and 55 m long and 20 m wide and at a depth of 360 m below ground surface. Three-dimensional FEM was used to simulate the mining operations and to estimate average pillar compressive stress at each operation step. A pillar performance function was established in implicit form taking into account pillar strength and pillar dimension. NN was incorporated in the FEM to substantially reduce the number of finite element calculations in establishment of the relationship between pillar compressive stress and basic random variables. Trained NN was then used to generate a database for the implicit performance function. The database was used to determine the reliability index and failure probability for each trial pillar diameter. Relationship between pillar reliability index and each of the coefficients of variation of the basic random variables was used for optimal design of pillar diameter. The optimal pillar design was used in the mining construction and functioned well.     

立井穿越采空区施工技术

结合和成煤矿主井穿越采空区工程实例，探讨了采空区岩石移动及压力显现规律，通过一系列计算得出采空区对井筒建设的影响，为井筒施工提供有效的数据，探讨了井筒压力测试及施工技术方案，对同类矿建工程有重要的指导意义。     

工程管理课程案例教学法研究

工程管理类课程的案例教学是指教师以实际工程项目案例为基础，在课程学习中帮助学习达到特定教学目的的一整套教学方法及技巧。为了避免工程管理类课程在案例教学过程中容易出现的案例与教学目标、教学内容脱节，案例教学与培养学生动手能力脱节的现象，本提出了在工程管理类专业课程中“以一个实际项目案例贯穿教学始终”的观点，将教学内容密切联系实际，将教师讲授与学生动手相结合，并辅以课堂讨论与案例讲评，以切实提高学生认识问题、分析问题与解决问题的能力。     

五凤煤矿高瓦斯井巷安全快速施工技术研究

总结了开拓方式整体布置、掘进工艺、施工组织、掘进设备等方面的施工要点,以提高煤岩巷道的连续掘进技术水平,改进生产工艺,优化劳动组织,实现煤岩巷道安全高效掘进。     

地面注浆加固井筒井壁产生裂纹的原因及防治

针对兖州矿区某煤矿注浆加固治理主井井筒过程中井壁产生新微细裂纹的问题，在进行调查和分析监测资料的基础上，详细阐述了裂纹产生的原因，指出地层在注浆过程中抬斗过快、不均造成了井筒受力不均，地层抬升产生的作用于井壁的竖向附加应力是导致井壁混凝土受拉应力过大从而产生裂纹的最根本啄因，同时提出了地面注浆加固井筒工程中防止类似问题出现应采取的措施。     

一种钻孔数据统计与找矿预测新方法——以辽宁白云金矿为例

钻孔资料中与矿体密切相关的信息提取对理解深部物质向上迁移是至关重要的,并且对金属矿产的勘查起到非常重要的作用。本文详细统计了白云地区的钻孔资料,提取侵入围岩地层中的所有岩脉、矿脉以及裂隙的厚度,并计算了每米钻孔中各地质体的垂向伸展程度(即垂向伸展率),绘制了平面分布图。通过对各地质体厚度和垂向伸展率平面分布图分析比较,认为岩脉厚度垂向伸展率与矿体厚度和垂向伸展率分布高度吻合,并且岩脉与裂隙厚度总和的垂向伸展率分布也与后者具有较高的吻合性,而且指示出潜在的北东向成矿潜力区。本文提出一种提取钻孔资料中的控矿因素与找矿预测新方法,希望在相同类型的矿床找矿预测工作中可以进行推广,更加精确地指导深部找矿预测工作。     

Effects of vent shaft location on the ventilation performance in a subway tunnel

A computational analysis of a ventilation system in a subway tunnel is carried out by solving 3D Reynolds-averaged Navier–Stokes equations for train-induced unsteady flow using the sharp interface method as the model for the moving boundary of an immersed solid. The ventilation performance is evaluated depending on the location of the vent shaft by analyzing the ventilating flow rate through the shaft and the feature of the flow field in the subway tunnel around the shaft. It is found that the optimum location of the vent shaft with respect to maximizing ventilation performance lies near the station.     

Evaluating the effect of soil structure on the ground response during shield tunnelling in Shanghai soft clay

When evaluating tunnel-induced ground response in Shanghai soft clay, the soil structure and its degradation behaviour of natural Shanghai soft clay during shield tunnelling should be properly considered. In this paper, a constitutive model that considers the initial soil structure and its destructuration is formulated within the framework of critical-state soil mechanics. The model is successfully calibrated and used to simulate the undrained behaviour of natural Shanghai soft clay. Based on the proposed model, finite-element analyses are conducted to simulate the short- and long-term ground responses induced by tunnelling at Shanghai metro line 2. The comparisons between numerical results and field measurements reported in literature indicate that the soil structure and the tunnel-induced destructuration significantly affects the magnitude and shape of the short-term surface settlement trough and horizontal displacement in Shanghai soft clay. The pore pressure variations around the tunnel are also affected by soil structure, which will significantly influence the long-term ground consolidation settlement in Shanghai soft clay.     

Selection of an ERP system for a construction firm in Taiwan: A case study

The primary functions of Enterprise Resource Planning (ERP) are to integrate the inter-departmental operation procedures and Management Information System (MIS) modules, and to reallocate the resources of a company. How to successfully implement an ERP system in an organization is always a hot research topic for researchers as well as a pending problem for an organization that wants to implement it. This research is a case study on the selection of system suppliers and contract negotiation during the ERP implementation of a local construction company in Taiwan. After reviewing the common key success factors discussed in the literature, this study discussed seven issues: coding system, working process reengineering, priority of ERP functionality implementation, customization, participant roles, consultant role and performance level of subcontractor, which also affected the implementation. Lessons learned from the case study in discussed seven issues are valuable for a construction company in deciding to implement an ERP system. This research suggests that additional case studies are necessary for the successful application of ERP systems in the construction industry.     

A study on the development and application of the E/V shaft cooling system to reduce stack effect in high-rise buildings

This study suggests the E/V(Elevator) shaft cooling system as a new approach to reduce the stack effect and the related problems in high-rise buildings. The basic characteristics on its application were analyzed with some simulations in this study. Moreover, the system was applied to an actual building and its performance was evaluated through the measurements.The system can reduce the stack effect itself and the related problems simultaneously and it can reduce the pressure and the air flow rate in each part of a building in the same ratio. These features were shown in the results of the simulations; for the examples, when all the E/V shafts were cooled from 22 °C to 12 °C, the stack effect and the pressure in each part of the modeled building were decreased by about 27%.In the field measurements, the wind velocity through the E/V door was decreased effectively in the whole building; its reduction ratio at the lobby floor was about 25% and at the upper floors (37F, 38F) about 10% respectively. But, the neutral pressure level at the E/V shaft was moved by the vertical temperature difference in the E/V shaft because of the inflow ducts concentrated in the lower part of the E/V shaft. This movement was also shown in another simulation on the same conditions as the measured ones. It is very important to minimize the vertical temperature difference in the E/V shaft to maximize the reduction effects on the problems.     

Influence of Benoto bored pile construction on nearby existing tunnel: A case study

The monitoring and analysis of lateral displacement for metro tunnels are very important because the metro systems are the lifeline of metropolises. This paper presents a case study of a site in Nanjing, China, where the Benoto bored piles were constructed nearby the existing tunnel. The construction technology, a combination of the Benoto bored piles construction and the conventional construction technology of circulating slurry, is illustrated in detail. The lateral displacement at six test sections were measured and discussed to assess the impact of piles installation on the stability and integrity of the existing tunnel. The measured results showed that during the construction period using the Benoto method, relatively large lateral displacement occurred at the depth with soft soil (Mucky silty clay), with characteristics including a large void ratio, high plasticity, poor permeability, high water content, low shear strength, and low modulus of deformation. During the construction period of the conventional Circulating-Slurry method, negative lateral displacement occurred below the tip of the casing due to the soil arching effect, indicating an inward movement towards the Benoto bored piles. The maximum lateral displacement decreased as the distance between piles and inclinometers increased, with a maximum difference of 45% at the end of the measurements. It was also observed that the measured maximum lateral displacement was less than the cumulative trigger value of 20 mm, indicating an effectiveness of Benoto bored piles constructed adjacent to existing tunnel. This case study may provide the means for a qualitative assessment for engineering constructions where the situation bears similarities.     

高阻尼橡胶隔震支座的力学性能及隔震效果分析研究

本文对新型高阻尼橡胶隔震支座的力学性能及此支座对桥梁的隔震性能进行了实验研究。通过正弦波实验研究其力学性能,实验结果表明新型高阻尼橡胶隔震支座是速度相关型支座,加载频率对其等效水平刚度有较大的影响,但对其等效阻尼系数影响不大。然而加载经历对新型高阻尼橡胶隔震支座对其等效水平刚度与等效阻尼系数均有较大的影响。同时通过数值分析精确的定量地验证了新型高阻尼橡胶支座对桥梁的减隔震效果。     

Influence of daily surface temperature fluctuations on rock slope stability: case study of the Rochers de Valabres slope (France)

The present paper describes a rockfall that has affected the Rochers de Valabres slope (France's Southern Alps region) and discusses one possible mechanism for the occurrence of this rockfall, along with the potential for future ones. In the absence of an obvious explanatory trigger factor, we set out to examine whether natural daily surface temperature changes could have played a role in this event. In particular, it is suspected that these slight, yet repeated, perturbations may be a preparatory factor for rockfalls, with a day-to-day cumulative effect. A numerical model strengthens this hypothesis by showing that thermally induced deformations can be sufficient to cause the gradual downward creep of a rock block located in an awkward position. To investigate this notion more thoroughly, a currently vulnerable part of the Rochers de Valabres slope has been instrumented with a high-precision geodetic monitoring system (total station). It is believed that this device is able to capture thermally induced movements if specific precautions are taken. The instrumented rock volume is used as a test site in the aim of better understanding the consequences of surface temperature changes on slope stability. Measured data (with a precision level never before achieved on rock slopes) are compared herein with numerical modelling results. The initial conclusions of the long-term study we are conducting indicate that surface temperature changes play an important, while not easily quantifiable, role in preparing rockfalls.     

Assessment the influence of ground stratification,tunnel and surface buildings specifications on shield tunnel lining loads (by FEM)

Urban development and rapid extension of cities have been accompanied by a considerable growth in mechanized shield tunnelling. Commonly precast concrete segments are used as tunnel lining which comprises relatively considerable part of tunnelling cost. The optimum design of lining needs to an accurate evaluation of loads acting on the lining.In this paper, the effects of ground stratification, surface buildings specifications and tunnel depth on lining loads were studied. For this purpose a 3D finite element model was used employing the ABAQUS software (Ver. 6.11). The geometry of tunnel, lining segments, injection grout and the surrounding soil properties were adopted from the under construction Tabriz urban railway line 2 project.The results show that the studied parameters have considerable effects on lining loads. For mentioned case study, surface buildings with 5 and more story have a considerable effect on lining loads, especially for shallow tunnels. The geometry of surface buildings influences the internal forces of the tunnel lining and increase of buildings width and length increases the lining loads. The building width is the most important parameter and with increase of that the influence of other parameters increases. Also by comparison of obtained results in this study with results of 2D analysis, reliability of 2D models was investigated. The comparisons show that 3D analysis is superior to 2D analysis, particularly in the cases of surface buildings presence. The difference between results increases with decrease of building length and increase of tunnel depth and building weight.     

A study of the hydrogeomechanical properties or rocks using experimental filtration tests and observations of ground water movement

Bulletin of Engineering Geology and the Environment - Complicated hydrogeomechanical processes take place within the layer during pumping tests and other kinds of aquifer tests; their physical and...     

隧道及地下工程岩体模型材料研究现状分析

归纳了当今国内外地质力学模型相似材料的研究现状,指出了常用相似材料的优缺点,并对测试相似材料力学特性的方法作了介绍,最终选取相似程度最好的模型材料,以更好的模拟实际条件。