工程数值法教学改革研究——以“地质工程数值法”为例

以"地质工程数值法"教学为例,针对工程数值方法的课程特点和目前教学中存在的典型问题,分析了教学改革的必要性,提出了教学改革的教学思想与教学理念,探讨了教学改革的实施方案,包括教学内容改革、学生能力培养和具体教学方法设计。最后分析了教学改革的成果,指出了其优点和注意事项。     

Slope stability prediction using ensemble learning techniques: A case study in Yunyang County,Chongqing, China

Slope stability prediction plays a significant role in landslide disaster prevention and mitigation. This study develops an ensemble learning-based method to predict the slope stability by introducing the random forest(RF) and extreme gradient boosting(XGBoost). As an illustration, the proposed approach is applied to the stability prediction of 786 landslide cases in Yunyang County, Chongqing, China. For comparison, the predictive performance of RF, XGBoost, support vector machine(SVM), and logi...     

An embodied carbon and energy analysis of modern methods of construction in housing: A case study using a lifecycle assessment framework

There is a growing interest in comparing the energy and consequential carbon embodied in buildings using different methods of construction and alternative materials. This paper compares the embodied carbon in a low energy, affordable house constructed using a novel offsite panellised modular timber frame system, in Norfolk UK with two traditional alternative scenarios. A lifecycle assessment (LCA) framework is used to conduct a partial LCA, from cradle to site, of the construction. An inventory of the materials and fossil fuel energy utilised in the construction was used to calculate the primary energy consumed and the associated embodied carbon. The embodied carbon was found to be 34.6 tonnes CO₂ for a 3 bedroom semi-detached house, 405 kgCO₂ per m² of useable floor area. When compared with traditional methods of construction the modern methods of construction (MMC) house resulted in a 34% reduction in embodied carbon. Despite timber being the predominant structural and cladding material, concrete is the most significant material (by proportion) in embodied carbon terms, responsible for 36% of materials related embodied carbon.     

边坡稳定分析的非连续面拓扑优化技术

土工结构稳定性的极限分析方法研究一直是热点问题。提出的非连续面拓扑优化技术(DTO)的主要特征之处在于稳定性问题的极限分析根据节点及其连线而不是单元或实体来进行构造。替代的近似过程主要采用适量的栅格节点来离散问题几何域,临界破坏机构则由节点间的连线集构造而成。基于Mohr–Coulomb屈服准则构造目标函数,并通过优化来确定极限荷载系数。结合离散构造特征,引入孔隙水压力和安全系数,DTO可拓展处理涉及地下水的边坡稳定问题。DTO是建立临界破坏模式和确定相应安全系数的有效工具,而无需考虑滑移面的入口/出口限界或点的约束与假设。本研究以复杂条件下的边坡稳定性为例,深入分析DTO和其他各种方法所得结果的一致性和差异性。相关比较表明,对于材料特性要求高、几何边界和荷载作用条件复杂的边坡稳定分析而言,DTO技术是一种可靠的替代分析手段。     

基于模糊集理论的边坡稳定性分析

岩土工程中的各种信息都存在模糊性,通过对边坡稳定性分析中模糊因素的研究,提出了一种工程边坡模糊稳定性分析的新方法,建立了边坡稳定性分析的模糊数学模型,并给出了相应的求解方法。该模型可以考虑分析中所涉及到的计算力学参数的模糊性。在分析岩土力学参数试验资料的基础上,结合专家经验提出了岩土力学参数的隶属函数构造方法,利用统计资料构造了边坡稳定性评价的隶属函数,并提出了边坡稳定性评价的具体分类指标和模糊安全系数隶属度的计算方法。实例研究表明边坡稳定性模糊分析方法是一种更为合理的研究边坡稳定性的新方法。     

Evaluation of ground settlement in response to shield penetration using numerical and statistical methods: a metro tunnel construction case

Shield tunnelling can cause ground settlement, which poses significant risks to adjacent structures or facilities. To understand complex soil behaviour in response to shield penetration, a model that can establish the shield–ground relationship and accurately predict tunnelling-induced ground settlement is necessary. The aim of this paper is to combine numerical methods and statistical methods for settlement prediction in the Wuhan (China) metro project. During the pre-construction stage, due to the lack of instrumentation data, the numerical method was applied to simulate the tunnelling process. The relevant factors influencing ground settlements were identified by examining the model’s sensitivity to each parameter. After the shield launch, data of the relevant factors and field measurements were collected. Using these data, a statistical model based on an adaptive relevance vector machine (aRVM) was trained for real-time prediction of the ground settlement development. The simulation results show that a number of factors, including geometrical, geological and shield operational parameters, contribute to ground settlement, and the aRVM model can accurately and effectively predict settlement development. The example application demonstrates that the method is a practical tool for settlement prediction and can be widely used in metro projects.     

Application of rock mass classification systems to rock slope stability assessment: A case study

The stability of rock slopes is considered crucial to public safety in highways passing through rock cuts, as well as to personnel and equipment safety in open pit mines. Slope instability and failures occur due to many factors such as adverse slope geometries, geological discontinuities, weak or weathered slope materials as well as severe weather conditions. External loads like heavy precipitation and seismicity could play a significant role in slope failure. In this paper, several rock mass classification systems developed for rock slope stability assessment are evaluated against known rock slope conditions in a region of Saudi Arabia, where slopes located in rugged terrains with complex geometry serve as highway road cuts. Selected empirical methods have been applied to 22 rock cuts that are selected based on their failure mechanisms and slope materials. The stability conditions are identified, and the results of each rock slope classification system are compared. The paper also highlights the limitations of the empirical classification methods used in the study and proposes future research directions.     

Analysis of thermal comfort in a residential room with insect proof screen: A case study by numerical simulation methods

The present paper aims to investigate the characteristics of airflow inside the room with insect proof screens by employing computation fluid dynamics (CFD) technique. Insect proof screens attached to the window openings were simulated by porous media approach. The simulated pressure drop across the insect proof screen was compared with the experimental result and is having a good agreement with a maximum error of 8.77% for the air velocity of 0.15 m/s. The insect proof screen significantly reduces the airflow rate and increases the indoor air temperature by 3°C. The effect of different window sizes and porosity of the insect proof screen is included for the study of thermal comfort index, predicted mean vote (PMV). From the PMV contours, center portion of the room and portions nearer to the windows are identified as comfort zones.     

Stability assessment of a slope under a transformer substation using numerical modelling

This paper presents an analysis of the deformation mechanism and stability assessment of a slope in Yunnan Province, China. Field investigations indicated that the deformation of the slope was caused by the combined effects of the unfavorable topographical, geological and hydrogeological conditions and the placement of man-made fill. The stability of the slope was assessed by 3D numerical modeling which showed that the factor of safety of the slope was 1.1 in the natural state but reduced to 1.03 after fill was placed. Pile reinforcement was undertaken, which raised the factor of safety to 1.27.     

Slope stability assessment of an open pit using lattice-spring-based synthetic rock mass (LS-SRM) modeling approach

Discontinuity waviness is one of the most important properties that influence shear strength of jointed rock masses, and it should be incorporated into numerical models for slope stability assessment. However, in most existing numerical modeling tools, discontinuities are often simplified into planar surfaces. Discrete fracture network modeling tools such as MoFrac allow the simulation of non-planar discontinuities which can be incorporated into lattice-spring-based geomechanical software such as Slope Model for slope stability assessment. In this study, the slope failure of the south wall at Cadia Hill open pit mine is simulated using the lattice-spring-based synthetic rock mass (LS-SRM) modeling approach. First, the slope model is calibrated using field displacement monitoring data, and then the influence of different discontinuity configurations on the stability of the slope is investigated. The modeling results show that the slope with non-planar discontinuities is comparatively more stable than the ones with planar discontinuities. In addition, the slope becomes increasingly unstable with the increases of discontinuity intensity and size. At greater pit depth with higher in situ stress, both the slope models with planar and non-planar discontinuities experience localized failures due to very high stress concentrations, and the slope model with planar discontinuities is more deformable and less stable than that with non-planar discontinuities.     

某建筑用花岗岩矿边坡稳定性分析及最优边坡角研究

本文以某建筑用花岗岩矿边坡为研究对象,根据矿山开采现状、工程地质条件选取边坡稳定性计算剖面,通过三轴压缩强度试验获取岩体的物理力学参数,采用M-P法和Bishop在自重+地下水+爆破震动荷载工况计算现状边坡及设计边坡的稳定性系数,最终边坡角以向下取1°和2°进行优化。计算结果显示：该矿现状边坡局部稳定性系数为不满足要求,该矿采场边坡整体边坡角可从47°优化成47.5°,优化后稳定性系数满足要求。     

Bayesian assessment of an existing bridge: a case study

This article presents a case study involving the assessment of an existing bridge, starting with simple methods and ending with a probabilistic analysis, the latter emphasising Bayesian methods. When assessing an existing bridge, it is common practice to collect information from the bridge in the form of samples. These samples are in general of small size, raising the question of how the corresponding statistical uncertainty can be taken into account on reliability estimates. The case study illustrates how Bayesian methods are especially suitable to deal with that source of uncertainty. Another strong point of the Bayesian methods is their ability to combine the information contained in the samples collected from the bridge with prior information, if any. This aspect will also be illustrated through the case study.     

Evaluation of combined sewer overflow assessment methods: case study of Cork City,Ireland

Discharges of untreated wastewater from combined sewer overflows (CSOs) present a potential threat to human health and the chemical and ecological status of receiving waters. Sewer monitoring coupled with hydraulic models are frequently applied to estimate CSO impacts and to test alternative improvement strategies, but their cost can be prohibitive. Therefore, municipal authorities must apply subjective assessment criteria to identify problematic CSOs which require immediate monitoring. In this paper, subjective assessment criteria for CSOs were reviewed and applied using a case study from Cork City, Ireland. Whilst the subjective criteria were robust in identifying nuisance CSOs (those giving rise to public complaint), the assessment of impacts on chemical and ecological status were confounded by other pollutant sources in the catchment and a lack of CSO monitoring data. A methodology was developed, using a geographical information systems (GIS) model, to prioritise monitoring of problematic CSOs on a national basis.     

基于ADINA的巷道支护稳定与数值分析研究

利用ADINA软件对高家梁煤矿2号煤层软岩巷道支护稳定和变形过程进行了动态仿真模拟,根据模拟结果分析了高家梁煤矿目前采用的“锚网喷带”联合支护的稳定性与合理性,并结合现场监测数据确定出最佳的二次支护时间,修正了以往根据经验和距迎头距离确定二次支护时间的僵化模式。     

Design of anchorage and assessment of the stability of openings in silty, sandy limestone: a case study in Turkey

This study presents a procedure for the design of anchorage and for the assessment of the stability of openings in silty, sandy limestone through investigating the geotechnical problems of the Hasankeyf historical settlement area in southeastern Turkey, of which a good portion will stay below the reservoir of the proposed Ilısu dam. Rock mass characterization was performed. The RMR and GSI methods were utilized for rock mass classification. The RocLab software was used to determine the shear strength parameters and the geomechanical properties of the rock mass according to the GSI method. The cohesion and angle of internal friction of the rock mass was determined as 257 kPa and 52°, respectively. A back analysis was applied to a structurally controlled planar failure block supporting one of the prominent historical structures in the area to determine the shear strength parameter pairs that satisfy limit equilibrium along the sliding surface of the planar block. A sensitivity analysis of the most likely shear strength pairs satisfying limit equilibrium was performed as a function of reservoir water condition (i.e., rapid drawdown, dry and wet reservoir condition) and the expected earthquake generated peak horizontal ground acceleration coefficient. The results of the back analysis led to a cohesion of 161 kPa and an angle of internal friction of 40° along the failure surface of the planar block. A limit equilibrium sensitivity analysis of the unstable rock block was performed as a function of the water condition of the reservoir, expected earthquake generated peak horizontal ground acceleration coefficient and rock anchor inclination angle. The minimum anchor force required for the stabilization of the planar block was calculated for a rapid drawdown condition as 4000 kN/m. A total of fifty six (56) rock anchors, each with a service load capacity of 1000 kN and spaced at 1 m are recommended for stability. Finite element analysis was utilized to analyze the collapse of some of the roofs of the adjacent man-made cave dwellings carved in rock due to insufficient pillar thicknesses and to determine the minimum pillar thickness required between adjacent caves in the region for stability. Nine different pillar thicknesses ranging from 0.1 to 0.93 m were analyzed. The stages included in the finite element analysis of the caves were: (a) gravity loading due to the thickness of the overburden followed by applying the far field horizontal stresses and inserting the planar block fracture; (b) excavating the caves in stressed rock assuming full face excavation and (c) applying a uniform traction load. The results of the finite element analysis led to a recommendation to apply a steel arch support to one of the adjacent caves located at Hasankeyf in case the wall thickness was less than or equal to 0.5 m.     

On an empirical relationship between SO2 concentration and distance from a highway using passive samplers: a case study in Shanghai, China

In this paper, field measurements were performed to determine SO(2) concentration gradients from a highway in Shanghai using passive samplers. It was demonstrated that passive sampling method is a cost-effective and convenient way to monitor specific gaseous pollutants at small scales over long sampling periods in air quality studies. Using function fit analysis for the measured results, a shifted power-law relationship had been found between SO(2) concentration and the distance from a highway. Accordingly, an empirical shifted power-law model was developed for describing and predicting the SO(2) gradients near a highway, in which k is the only parameter and named as diffusion attenuation coefficient. There was a surprisingly significant negative correlation between known SO(2) concentration at reference point (C(0)) and diffusion attenuation coefficient (k). By the correlation equation of C(0) and k, appropriate value of k could be calculated with measured C(0). Therefore, the empirical shifted power-law model developed in this study could be practically and conveniently applied for predicting the SO(2) distributions near a highway with known C(0).     

某深水基坑支护稳定性数值模拟研究

为研究深水基坑施工稳定性,以某桥梁深水基坑施工为例,通过运用有限元软件ADINA进行数值模拟,分析了水平位移、内支撑位移及受力情况,并与现场实际监测数据进行了对比研究,得出了一些有益的结论。     

某高速公路边坡稳定性分析及治理方案

针对西部工程建设中需要大量开挖边坡的现状,以其中典型边坡为例,进行了稳定性分析计算,并提出相应的治理措施以及建议,以确保不会对周围的居民生活造成影响以及河水污染。