多失效模式下基于区间非概率的岩质隧道稳定可靠度分析

对于岩质隧道工程的稳定可靠度分析,一方面由于岩体参数的统计数据获取困难使得概率可靠度方法难以适用,另一方面其工程稳定与多种失效模式密切相关,须考虑隧道结构体系的可靠度问题。首先,基于区间理论,通过区间变量形式表征不确定性参数;然后,针对岩质隧道工程中多种失效模式并存的情况,引入结构体系可靠度理念,建立基于区间非概率的岩质隧道结构体系可靠度指标计算及其稳定性评价方法;在此基础上,通过工程实例验证了该方法的合理性;最后,定义不确定性参数的波动幅度,进一步分析各失效模式中不同参数对相应可靠度指标以及结构体系可靠度指标的影响。分析结果表明,各失效模式相应的非概率可靠度指标均随区间变量范围的增大而降低,且同一参数在不同失效模式中表现出不同的影响;另外,不确定性参数的变化还将导致影响岩质隧道结构体系稳定的主要失效模式发生相应的变化。     

工程地质信息化设计及其在交通工程中的应用

工程地质信息化设计是工程地质应用领域的延拓。它对于工程设计的优化具有十分重要的作用。根据理论研究和工程实践，对工程地质信息化设计中的基本问题进行了归纳总结。论述了工程地质信息化设计的基本理论与方法，提出了信息化设计的工作思路，归纳分析了信息化设计中的数值模拟方法、岩体结构面网络模拟技术、GIS集成技术及其关键技术问题与解决途径。以京珠高速公路湖北大悟段为例，说明了工程地质信息化设计的工作过程和一条龙体制的优越性。     

Incorporating Parameter Variability in Rock Mechanics Analyses: Fuzzy Mathematics Applied to Underground Rock Spalling

Although fuzzy analysis has been widely developed, its use in rock mechanics and rock engineering is limited. Here, it has been used to evaluate the potential for underground rock spalling at the boundary of a circular excavation in terms of rock strength and in situ rock stress, given the uncertainty in both of these input parameters. Using standard techniques from fuzzy mathematics, we develop an expression for the fuzzy factor of safety, and extend this to form the crisp parameters Safety Certainty Value and its complement, the Failure Certainty Value. Plots of the Failure Certainty Value in terms of the in situ stress ratio and rock strength/stress ratio show the effect of uncertainty on the assessment of stability. From these plots, we illustrate how the relative importance of uncertainty in the input parameters can be assessed, with the associated ramifications for site investigation and subsequent engineering design.     

Application of Fuzzy Set Theory to Rock Engineering Classification Systems: An Illustration of the Rock Mass Excavability Index

The characterization of rock masses is one of the integral aspects of rock engineering. Over the years, many classification systems have been developed for characterization and design purposes in mining and civil engineering practices. However, the strength and weak points of such rating-based classifications have always been questionable. Such classification systems assign quantifiable values to predefined classified geotechnical parameters of rock mass. This results in subjective uncertainties, leading to the misuse of such classifications in practical applications. Fuzzy set theory is an effective tool to overcome such uncertainties by using membership functions and an inference system. This study illustrates the potential application of fuzzy set theory in assisting engineers in the rock engineering decision processes for which subjectivity plays an important role. So, the basic principles of fuzzy set theory are described and then it was applied to rock mass excavability (RME) classification to verify the applicability of fuzzy rock engineering classifications. It was concluded that fuzzy set theory has an acceptable reliability to be employed for all rock engineering classification systems.     

基于岩体结构特征和未确知测度评价模型的岩质开挖边坡稳定性研究

综合黔西地区层状岩质开挖边坡研究成果发现:岩体结构特征是分析评价层状边坡变形失稳模式、机制和稳定性的重要基础。因此,结合该地区层状边坡地质条件的差异性,针对性地划分岩体结构类型对边坡的分析评价尤为重要。考虑地层岩性组合、地质构造、软弱夹层（结构面）因素,系统地将边坡岩体结构类型分为4个大类（近水平-缓倾边坡岩体,倾斜层状边坡岩体,陡倾、直立、倒转层状岩体,地质构造作用强烈或含有溶蚀洞穴、沟壑的边坡岩体）和10个亚类,并针对相应类型的边坡进行工程地质综合评价,分别阐述了失稳模式和机制。以边坡岩体结构类型为基础,甄选影响开挖边坡稳定性的6个定性指标和6个定量指标;对指标组合赋权,用未确知测度理论对边坡进行稳定性预测评价,建立了“岩体结构-指标组合赋权-未确知测度理论”的新评价体系。实例预测结果表明预测结果与实际情况具有较好的一致性,说明该方法是一种可靠性高、科学合理的稳定性预测新方法,可在相关工程领域中应用推广。     

柱下独立基础稳健性设计与分析

岩土工程随机参数统计特征的不确定性,使得岩土工程可靠度设计存在一定风险。岩土工程稳健性设计能够充分考虑随机参数的不确定性结合结构安全性、稳健性和经济性实现最优设计。针对随机参数统计特征的不确定性对柱下独立基础设计的影响,基于可靠度理论和岩土工程稳健性设计方法,考虑岩土参数、混凝土和钢筋材料力学参数统计特征不确定性的影响,以独立基础几何尺寸作为可控设计参数进行设计分析。将独立基础地基承载力、地基变形、基础结构冲切破坏和基础弯曲破坏4种失效模式视为串联系统,进行多失效模式下的结构体系稳健性设计,分析了多失效模式下结构几何参数与结构体系可靠度的关系。结合稳健性和经济性,进行了独立基础多目标优化设计,确定柱下独立基础设计的最优解。     

Planning and design considerations in karst terrain

This article discusses the various steps that the authors feel are necessary to the successful progression of an engineered project sited in karst terrain. The procedures require a multidisciplined approach with liaison and cooperation among the various parties to the project. Initially, the prospective owner must have sufficient understanding of the potential engineering problems to incorporate the engineering geologist into the early stages of any planned acquisition. The first step in an investigation should include a review of the available geologic information, aerial photo interpretation, consultation with the State Geological Survey, and a geologic reconnaissance of the prospective site and surrounding area. A go-no-go decision as to purchase can often been made at an early time. Although, in some instances, more study is needed for a particularly intriguing property. The second stage should consider the various planning alternatives that are feasible based upon the limited available information. At this stage planning/purchase decisions can be made as to purchasing options, value of the property, design constraints, and the possible economic penalties that could be associated with the potential site construction. Various planning and construction alternatives should be considered in this phase of the work. The third stage should include a site investigation program of moderate size, consisting of test pits and/or exploratory borings. The borings should be drilled using water as the drilling fluid, with an experienced crew and qualified technical inspection. The authors find the use of geophysical techniques can be extremely misleading unless used in conjunction with exploratory drilling. Successful evaluations using geophysical procedures occur only under ideal conditions. The geotechnical viability of the plan and preliminary design should be investigated in the fourth phase. Additionally, the physical parameters required for the design of structures founded atop cavities can be obtained at this time. Several support schemes which incorporate cavity roof thickness, rock strength, and cavity space are discussed. Possible construction procedures include excavation and dental concrete, grouting, piers or piles to sound rock, or moving to another area. The relative economies of these procedures are discussed in relation to the size and depth of the soil or rock cavity, possible future cavity formation, magnitude of loading and acceptable safety factors.     

基于突变理论的地下工程洞室围岩失稳判据研究

地下工程围岩体系是高度非线性的复杂大系统,其稳定判据至今没有一个统一的认识。突变理论注重研究系统状态发生突变时外界的控制条件,主要阐述非线性系统如何从连续渐变状态走向系统性质的突变。应用突变理论对围岩体失稳的突变过程进行探索,旨在从理论上弄清其突变条件。能量突变判据和熵突变判据从物理学的观点考虑了围岩系统失稳的可能性,位移模突变判据、洞周屈服区面积突变判据和广义黏塑性剪应变突变判据则主要是根据数值计算中直观判别条件（关键点位移、洞周屈服区面积和广义黏塑性剪应变）考虑围岩失稳的可能性。将以上5种判据应用于某地下洞室断面,对围岩系统的稳定性进行分析,根据系统突变条件从不同的方面判别其发生失稳的可能性,可为工程的设计施工提供一定参考。     

山岭隧道工程综合地质勘察方法探讨

山岭隧道工程具有隐蔽性、施工复杂性、地层条件和周围环境不确定性等特点,采用科学的勘察方法,是查明隧道岩土体工程地质条件的有效手段。本文以海淀区西山隧道为依托,针对隧道工程勘察中的关键地质问题,运用工程地质测绘、钻探、工程物探、水文地质勘查等综合勘察方法,有效地查明隧址区的地质构造、岩土体结构和地下水分布特征,全面、客观地评价隧道进出口段边坡及仰坡稳定性、隧道围岩质量与稳定性、隧道涌水量、地应力及有害气体等工程地质问题,并针对不良地质现象提出防治对策,以期为工期紧张、地形困难且日趋增多的山岭隧道工程地质勘察,提供可以借鉴的模式和方法。     

白鹤滩河谷演化模拟及P2β3玄武岩级别评估

详细分析了白鹤滩坝址河谷边坡柱状节理玄武岩岩体地质条件和特征,建立了合适河谷边坡演化离散元的计算模型,考虑坝址关键地层P2?3可能的岩体质量范围进行了多种工况河谷演化模拟计算。在此基础上深入研究了各工况河谷现今阶段边坡应力分布、变形情况、屈服区及稳定系数等基本规律,并与目前河谷实际的地质条件及现状进行了全面对比。最后采用拟似度信息量评分法对P2?3岩层工程级别进行了初步评定,认为白鹤滩水电站可行性研究阶段坝址P2?3岩层按III1类质量岩体来评估其工程性状和确定相应岩体力学参数较适合。同时,坝址河谷边坡岩体的工程特性可参考相应工况的模拟结果评价。     

红石岩震损高陡边坡工程岩体质量评价

高陡岩质边坡在经历强震过后,其浅部岩体受地震动力瞬时循环载荷作用而导致岩体质量下降,即所谓震损边坡。震损边坡的工程岩体质量对施工措施的制定和边坡安全评价至关重要。针对震损边坡岩体的实际特点,以工程岩体质量评价的BQ分级体系为基础,应用三维激光扫描技术来识别岩体结构面和节理裂隙,并结合岩块单轴抗压强度试验,建立了震损边坡工程岩体质量评价方法。应用提出的方法对云南鲁甸红石岩震损边坡Ⅱ区进行工程岩体质量评价,分析结果表明:震损边坡Ⅱ区浅部岩体较为破碎、受长期卸荷和地震扰动影响,节理裂隙发育,运用三维激光扫描技术识别、统计岩体结构面情况,再结合常规的岩体质量分类方法,最终确定岩体分级为Ⅳ类,结果较符合实际情况。该方法能够远程非接触式地识别统计岩体的结构面信息,尤其适合岩体破碎或坡面高陡而技术人员无法到达的危险边坡的岩体质量评价,可为其他类似工程提供参考。     

岩土工程风险分析及应用综述

系统分析了岩土工程不确定性的根源及其分析方法,总结了降低不确定性的途径。系统评述了岩土参数随机场估计、随机变量描述方法以及模型不确定性研究。对几类典型岩土工程问题的风险分析方法、研究现状及其工程应用进行了总结。对目前岩土工程风险理论及其应用的前沿问题进行了研究和展望。研究指出岩土工程风险分析待研问题主要有：系统的风险源辨识方法包括风险源辨识的可视化研究,不确定性因子的合理描述研究,极限状态包括失效模式的仿真研究,不确定性计算包括应用信息融合技术数据挖掘技术研究,目标可靠度研究,风险转嫁风险交换的量化及风险跟踪的实施研究,风险的反分析研究等。展望岩土工程风险分析与应用：风险分析反映了对工程设计的综合性要求,表现了安全与经济的统一;定量风险分析作为决策工具或传统设计的补充,可给决策者提供更多的辅助评价信息,提高了结果的置信程度;但现在能描述的还只是“随机性的确定性模式”,工程师们只有使用“保守的”选择,以适应和弥补不完全的认识与有限的资料的条件。     

山区道路泥石流减灾问题与对策

文章通过分析我国山区道路泥石流防治的特点与需求,认为山区道路潜在泥石流的判识与预测、泥石流对线路展布的制约、泥石流对道路工程设计的影响等是山区道路建设的关键技术问题。在山区建设中应研究潜在泥石流的判识方法、发展山区道路选线理论、认识道路工程与环境相互作用机制、创建与环境协调的道路工程反馈设计理论、构建山区道路泥石流减灾技术体系、开发道路环境灾害信息系统等工作。系统分析了道路勘察选线、个体工程设计、施工、运营阶段应注意的泥石流防治问题,根据不同阶段的灾害危害方式与特征,提出道路建设不同阶段的泥石流防治对策。     

岩体工程地质力学在水电水利工程勘察中的应用

应用谷德振先生的岩体工程地质力学理论,重视区域地质构造体系、重视收集地质基础资料、重视岩体结构的研究。在此基础上开展高拱坝、高重力坝、深埋长隧洞、地下厂房、抽水蓄电站的工程地质勘察和编制相应的地质勘察规范。     

工程地质综合性与岩体结构动态控制观的提出

当前我国一系列大型地质工程建设中地质灾害预报和动态设计、信息化施工的需求,使工程地质学面临综合理论创新发展的历史性机遇和挑战.有关学者提出大成综合理论,从源头上综合了专家的多源知识,从理论上凝炼了工程地质学高度综合的特点.以大成综合理论为基础,作者提出将众多因素相互作用进行观察、判断和测试,建立关系矩阵并加以权重分析和活跃强度等运算,提出了表征工程地质多因素作用关系简便可行途径.其研究难点在于综合认识地质条件的原生、次生和工程作用下的变化.总结复杂地质条件下国内外地质工程实践经验,提出了自然演化和工程扰动下岩体结构动态控制观(DDC).结合工程场地规划和比选,以工程地质分区(EZI)、综合适宜性(CSI)、加固需求度(DRD)等可操作的量化指标,发展工程施工乃至运行扰动作用下的岩体结构控制论,更好地服务于地质工程与环境和谐的高层次决策目标.复杂地质条件下工程实践说明了DDC提出的科学合理性,以及解决复杂性问题的实用性.     

Updating the models and uncertainty of mechanical parameters for rock tunnels using Bayesian inference

Rock mechanical parameters and their uncertainties are critical to rock stability analysis, engineering design, and safe construction in rock mechanics and engineering. The back analysis is widely adopted in rock engineering to determine the mechanical parameters of the surrounding rock mass, but this does not consider the uncertainty. This problem is addressed here by the proposed approach by developing a system of Bayesian inferences for updating mechanical parameters and their statistical properties using monitored field data, then integrating the monitored data, prior knowledge of geotechnical parameters,and a mechanical model of a rock tunnel using Markov chain Monte Carlo(MCMC) simulation. The proposed approach is illustrated by a circular tunnel with an analytical solution, which was then applied to an experimental tunnel in Goupitan Hydropower Station, China. The mechanical properties and strength parameters of the surrounding rock mass were modeled as random variables. The displacement was predicted with the aid of the parameters updated by Bayesian inferences and agreed closely with monitored displacements. It indicates that Bayesian inferences combined the monitored data into the tunnel model to update its parameters dynamically. Further study indicated that the performance of Bayesian inferences is improved greatly by regularly supplementing field monitoring data. Bayesian inference is a significant and new approach for determining the mechanical parameters of the surrounding rock mass in a tunnel model and contributes to safe construction in rock engineering.     

Value of information analysis in rock engineering: a case study of a tunnel project in Äspö Hard Rock Laboratory

Geoengineering prognoses are often based on data from a limited number of investigations of soil and rock mass. There is generally a desire to reduce the uncertainty in the prognoses while minimising the investigation costs. Value of Information Analysis (VOIA) is a support for decisions regarding investigation strategies and the aim of this paper is to present methodology for VOIA that takes into account four decision alternatives where the input data could be provided by experts. The methodology will be applied in a case study where the value of information related to an investigation borehole will be calculated. The results indicate that the value of information of the borehole is low compared with the realisation costs of the investigation. It was found that models for VOIA in underground construction projects are complex but that the analysis can be simplified with extensive use of expert knowledge and calculations of the value of perfect information as a benchmark for investigation strategies.