Probabilistic analysis of responses of cantilever wall-supported excavations in sands considering vertical spatial variability

The influence of vertical spatial variability of sands on the excavation-induced lateral wall deflection and bending moment of excavations supported by cantilever retaining walls is investigated in this paper. Herein, the random finite element method (RFEM) is adopted to explicitly study the effect of one-dimensional spatial variability of internal friction angle of sands on the predicted wall and ground responses. The RFEM analysis consists of three components: (1) finite element method for analyzing lateral wall deflection and bending moment, (2) random field theory implemented with Monte Carlo simulation (MCS), and (3) statistical interpretation of MCS results through confidence intervals. This study reveals the importance of random field modeling in coping with the spatial variability of sands in the problem of supported excavations: (1) neglecting spatial variability of soil property will cause an overestimation of the variation in the predicted wall deflection and bending moment; (2) the estimated probability of failure based on a well-established serviceability limit state may be overestimated or underestimated depending on the chosen limiting lateral wall deflection. This study further investigates the effect of the number of MCS on the confidence intervals of the predicted statistics of the maximum lateral wall deflection and the maximum bending moment. The results also demonstrate that the confidence interval analysis of the predicted statistics of the maximum lateral wall deflection and the maximum bending moment provides a rational tool for interpreting the statistical data from RFEM.     

水文井钻探施工中几种钻进方法的比较

结合施工过的水井实例，介绍了水文水井钻探施工中常用的钻探工作类型：回转钻进．冲击钻进及冲击回转钻进。其中回转钻进适合于砾石粒度小于80-100mm的地层，冲击钻进要求小于200mm的砾石总量不能超过50％．且地层均匀，而冲击回转钻进适合于含大漂石地层。在钻探施工中应根据具体工程地质条件．选用水井配套设备，并对施工中常见的钻进事故，提出了相应的解决办法。     

(Re)thinking the dynamics between healthcare and place: therapeutic geographies in treatment and care practices

Although the concept of therapeutic landscapes has assisted health geographers to explore the intimate connections between well-being and place, arguably, after a decade of applications, the common interpretations and assumptions of commentators should be reviewed. Based on theoretical insights from psychoanalytic geographies and geographies of nursing, this paper makes two observations. First, that landscape has been almost exclusively interpreted in a physical sense with co-presence being a necessary condition. In turn, this assumption has led to the neglect of non-physical (imagined) places. Second, that therapeutic effects have been interpreted as experiences attained outside of clinical practices. Hence, healthcare workers and their direct treatments and care have also been neglected. To explore these omissions together, an interview survey of complementary therapists investigates the many ways in which imagined places are constructed and manipulated in therapy sessions. Arguably, beyond this example, extending the therapeutic landscape concept to both physical and non-physical features of treatments could provide fresh insights into the dynamics between healthcare and place. In disciplinary terms, the benefits are twofold. Whilst it could help develop a critical tradition in health geography, perhaps ironically, it could also provide a stronger disciplinary connection between qualitative health geography, various forms of medicine and their research traditions.     

Active faults and magnitudes of left-lateral displacement along the northern margin of the Tibetan Plateau

The northern margin of the Tibetan Plateau (NMTP) is a major intracontinental Cenozoic transpressional zone that comprises a series of active strike-slip faults and thrust faults. It is important to document cumulative horizontal displacements along the NMTP in order to understand quantitatively strain partitioning in East Asia since the India–Eurasia collision. Based on an analysis of horizontal slip along major active faults, the total amount of horizontal displacements is estimated up to 700 km between the Tibetan Plateau and the Tarim Basin since the convergence of India and Eurasia. Along the western and middle segment of the Altyn Tagh fault to the northern margin of the Qaidam Basin, there are abundant evidence that show that the net displacement is 400 km since 40–35 Ma, and along the Shulenan Shan and southeast of middle Qilian Shan since 25–17 Ma, the amount of offset is 150 km. The largest horizontal slip in Qilian Shan–Hexi Corridor to the northeast of the Altyn Tagh fault is also 150 km since late Oligocene to early Miocene. It decreases to only 60 km along the Haiyuan fault (since late Miocene) and to 25 km along the Zhongwei–Tongxin fault since the Pliocene (about 5.3–3.4 Ma), at the northeast margin of the Tibetan Plateau. This clearly implies northeastward diminishing of the total horizontal displacement and temporal getting younger of the fault slip along the NMTP. However, this tendency is very complicated at different times and different segments as a result of the uplift, growth and rotation of different segments of the NMTP at different stages during the convergence of India and Eurasia.     

求梁位移的比拟梁法

有多种方法求梁的位移，如积分法、叠加法、初参数方程法、其轭梁法、有限差分法、奇异函数法和莫尔“面积-力矩”法等等，其大都具有或计算复杂或依赖各种不同的图表等特点。提出比拟梁法，试图开辟一个新的路径，即以记忆少量系数迭到计算同样问题而过程又相对较简单之目的。由挠曲线连续性出发，从平面几何角度观察了欲求挠度和转角的关系，发现其可表示成谓之为比拟梁法的自由端挠度的函数。建立的公式表明，其优点是在无法查表情况下便当算出梁位移。当多个荷载同时作用时，则此法优势明显。     

高斯积分在地球重力场数值计算中的应用

高程异常、垂线偏差及空中扰动引力矢量是大地测量和空间技术最常用的一组重力场参数,本文在分析了以上三种参数的计算误差源以后,详细论证了计算这些参数对积分面积元的不同要求。在此基础上,本文尝试将高斯积分应用于地球重力场数值计算中,试验结果表明,这样做不仅提高了计算速度和精度,而且能够在一定程度上克服重力场元数值积分的奇异性。     

通过测斜数据预判测斜管失效的分析方法研究

岩土测斜仪已广泛应用于现场土体和结构物的变形监测,其工作原理是通过测量测斜管的变形以反映监测对象的变形,用于工程的稳定性和安全分析。当工程的稳定和安全受到威胁的时候,往往伴有局部过大的变形现象发生,这可能造成测斜探头不能放入测斜管内,使测斜管失效、关键数据缺失。为预判测斜管失效的可能性,提出5种方法确定测斜管局部变形曲线的曲率或折角,并与测斜管失效时的极限曲率或极限折角进行对比,分析失效的可能性。通过某基坑开挖工程1根测斜管失效的实例分析,对比所提出方法的适用性,从中推荐五型值点单点约束拟合双圆弧法,用于判别测斜管失效。     

基于变形加固理论的岩土边坡稳定和加固分析

传统的刚体极限平衡法和强度折减法在分析边坡稳定和加固时存在一定的局限性。基于变形加固理论,建立了基于弹塑性有限元分析的边坡稳定和加固分析方法。以余能范数作为边坡整体稳定评价的指标,通过强度参数降低过程中的余能范数的变化来确定边坡的整体稳定安全系数。加固的关键部位和加固力的大小通过边坡中不平衡力的分布来确定。滑动面则由方向相反的、成对的不平衡力的分界面来确定。针对3个经典边坡算例,分析了强度参数逐渐降低过程中的余能范数的变化和不平衡力的分布,确定了边坡的稳定安全系数以及相应的加固关键部位和加固力的大小。结果表明,变形加固理论基于岩土的三维非线性有限元分析,以此来进行边坡的稳定和加固分析是非常有效的,强度参数降低过程中不平衡力的发展演化过程反映的是边坡的破坏过程     

西北干旱和半干旱地区地表蒸发计算方法评估应用

针对我国西北地区干旱和半干旱的气候特征,以及相对简单的地表覆盖特点,论证了互补相关模型计算西北地区蒸发量的可行性。通过中国科学院山东禹城试验站农田观测资料,分析了植被多样性分布对互补相关模型的影响。得出植被的多样性以及植被物候变化的非同步变化是造成互补相关模型中关键参数——大尺度平流参数季节变化的重要原因。并利用遥感反演参数和气象台站观测数据计算了覆盖类型相对单一的西北地区蒸发。结果表明,蒸发与地表覆盖类型的空间分布一致,与气象台站20 cm蒸发皿观测数据呈现空间互补特征,其季节变化与区域降水、温度和植被物候变化相吻合。