10th annual report on the international status of engineering geology—year 2004-2005; encompassing hydrogeology, environmental geology and the applied geosciences

The year was particularly eventful in terms of the recognition of improved technologies impinging on the duties of the Engineering Geologist. National economies were strained to the limit under the pressure of the new world terrorist attacks and burgeoning populations. much of which stemmed from escapes from oppressive national regimes to the free world. The impacts of terrorism range from increased danger and costs of field work, to special design considerations and postponed and delayed project work.On the positive side, continued progress has been made in the means of recognition and professional development of our practitioners and in the general call for their work. Competent engineering geologists are in consistent demand, but the working conditions are not improved. A general deterioration of university funding, aggravated by bureaucratic excesses among administrators, have tended to make life miserable for dedicated faculty and a general move is afoot to cut back on the number of funded geology departments in North America and Europe. This situation has also been worsened by the general withdrawal of the mineral industries and by retraction of the petroleum companies from all but their most favored campuses.     

Distributed fiber optic monitoring and stability analysis of a model slope under surcharge loading

In the discipline of geotechnical engineering, fiber optic sensor based distributed monitoring has played an increasingly important role over the past few decades. Compared with conventional sensors, fiber optic sensors have a variety of exclusive advantages, such as smaller size, higher precision, and better corrosion resistance. These innovative monitoring technologies have been successfully applied for performance monitoring of geo-structures and early warning of potential geo- hazards around the world. In order to investigate their ability to monitor slope stability problems, a medium-sized model of soil nailed slope has been constructed in laboratory. The fully distributed Brillouin optical time-domain analysis （BOTDA） sensing technology was employed to measure the horizontal strain distributions inside the model slope. During model construction, a specially designed strain sensing fiber was buried in the soil mass. Afterward, the surcharge loading was applied on the slope crest in stages using hydraulic jacks and a reaction frame. During testing, an NBX-6o5o BOTDA sensing interrogator was used to collect the fiber optic sensing data. The test results have been analyzed in detail, which shows that the fiber optic sensors can capture the progressive deformation and failure pattern of the model slope. The limit equilibrium analyses were also conducted to obtain the factors ofsafety of the slope under different surface loadings. It is found that the characteristic maximum strains can reflect the stability of the model slope and an empirical relationship was obtained, This study verified the effectiveness of the distributed BOTDA sensing technology in performance monitoring of slope.     

Distribution of the factor of safety,in geotechnical engineering,for independent piecewise linear capacity and demand density functions

In many geotechnical engineering cases, the factor of safety may be defined as the ratio of the capacity, of the geotechnical structure or its support elements, to the pertinent demand. By representing the capacity and the demand as independent piecewise linear random variables, an analytic solution is obtained for the probability density and cumulative distribution functions of the factor of safety. Thus, solutions for the calculation of the mean value, the standard deviation and the minimum and maximum values of the factor of safety, are provided. Application of the developed analytical solutions, to the probabilistic analysis of a published case of rock spalling in a deposition tunnel complex, follows. The methodology allows for the parametric evaluation of the effect of specific design variables to the distribution of the safety factor and to the probability of failure. The closed form solution may be programmed as a computer code that may run easily on a tablet or netbook or even on a smartphone. It proves useful for the probabilistic design of a variety of geotechnical applications, such as foundations, tunneling, mining, underground roof reinforcement, and earth retaining structures, and permits decisions to be taken in terms of risk and reliability.     

TGLW220×660型冲洗液离心机转鼓的强度分析

对自行研制应用于地质钻探的TGLW220×660型冲洗液离心机的转鼓建立了三维实体模型,利用有限元分析软件对其在正常工况下的整体结构进行了三维有限元分析与模拟仿真。分析结果表明,离心机转鼓在正常工况下的强度满足要求;传统理论强度校核进一步验证了转鼓设计的合理性和安全可靠性,为TGLW220×660型冲洗液离心机在现场安全使用提供了重要的理论依据。     

Influence of model type,bias and input parameter variability on reliability analysis for simple limit states in soil–structure interaction problems

ABSTRACT

A general closed-form solution for the true probability of failure of a simple limit state function with one load term and one resistance term is derived. The formulation considers contributions due to model type, uncertainty in method bias values, bias dependencies, uncertainty in estimates of nominal values for correlated and uncorrelated load and resistance terms, and average margin of safety expressed as the operational factor of safety. Example calculations are presented using different load and resistance models for the pullout internal stability limit state of steel strip reinforced soil walls together with matching bias data reported in the literature.     

Characterising soil property in an area with limited measurement: a Bayesian approach

The Bayesian approach has been proved useful to geotechnical engineering especially when project-specific data/measurements are very limited. In this paper, we introduced a new Bayesian algorithm to estimate soil properties at each location of a study area, with very limited project-specific data. In addition to the proposed methodology and algorithms, we also conducted a model application to estimate soil permeability for each of the 64 locations within a 4-by-4 m² area, based on very limited project-specific data, that is, one measurement from each location.     

膨胀土地基中隧道施工对群桩影响研究

在膨胀土地基中进行隧道对群桩影响的三维离心模型试验研究,目标地层损失比为2%,着重研究引起的地基沉降槽、桩的附加沉降、附加弯矩、轴力的变化规律。试验得出：隧道开挖沉降槽空间效应明显;隧道开挖从-0.75D至1.25D时,桩附加沉降呈线性增长,隧道开挖至1.25D以后,桩依然沉降明显。前桩与后桩沉降值不同,桩帽会出现倾斜;前桩上部出现负附加弯矩而下部出现正附加弯矩,而后桩仅在下部出现正附加弯矩;前桩附加弯矩最大值出现在隧道轴线附近,且比后桩附加弯矩大得多;前桩附加轴力随着隧道的开挖而增加,且每步最大值在隧道轴线附近。后桩的轴力也随隧道的开挖而增加,但每步最大值出现在桩顶附近。     

探地雷达在岩土工程勘察中的应用

探地雷达是利用超高频脉冲电磁波探测地下介质分布的一种地球物理勘探方法,由于其具有高效率、高分辨率、高准确率等特征,在浅层岩土工程勘察中应用越来越广泛。以国道G110改造工程勘察为例,介绍探地雷达在岩土工程勘察中的应用,对于确定断层的深部展布状况和花岗岩囊状风化界面起到了重要作用,给勘探孔之间地质体的推断解释提供了科学依据。     

深厚吹填砂港区堆场地基沉降预估方法

根据大面积深厚吹填砂工程的特点,分析太沙基一维固结理论在分层地基,分级加载等复杂工程条件下应用的可行性,提出了相应的简化计算模型,并编制一维固结计算程序。结合上海某围海成陆港区堆场工程,对其吹填砂层及软弱下卧层的固结沉降进行了计算分析,通过计算结果和离心机模型试验结果的对比分析,对计算模型进行修正,提出了大面积吹填砂工程地基沉降预估方法。