基于变渗透系数的深基坑单井抽水沉降研究

地下水抽采是造成地表沉降的重要原因。基于弹性多孔隙介质Konzeny-Carman渗透模型,考虑地层在抽水过程中变形导致土层内部物理力学性质的改变,建立了基于土体应变的变渗透系数模型,并引入了渗透影响系数概念。运用有限元多物理场耦合软件COMSOL建立模型,采用Darcy渗流模式与弹性多孔隙介质完全耦合方法,研究了抽水过程中地层沉降量与渗透影响系数以及渗透系数的变化规律,并与实测沉降值进行对比。研究表明,采用考虑土体变形的变渗透系数模型所计算的沉降量与实测沉降变形较好地吻合,该模型能更好地反映抽水过程中沉降动态过程。     

钉螺流场实验模拟及其应用

血吸虫病是长江流域最严重的寄生虫病之一。钉螺是其唯一的中间寄主,钉螺的扩散将导致血吸虫病的蔓延。控制钉螺随水流扩散就能从根本上控制血吸虫病在灌区或居民点流行。本文介绍一种新的无螺取水方法,该方法已在实验室研究中取得了成功。这种无螺取水新方法是根据钉螺的生态水力学特性的系列试验研究和流场的计算水动力学数值模拟结果得到的。     

烟台雨岱山渔人码头工程潮位和波浪分析计算

为满足烟台雨岱山渔人码头工程建设的需要,对工程区附近气象和海洋动力等海洋环境进行调查计算分析,提供了工程区准确可靠的海洋环境参数,以便工程设计和建设使用。     

高速铁路轨道中长波平顺性参数计算方法

高速铁路轨道中长波平顺性参数的计算方法是高速铁路轨道精测与精调的核心技术,现有的中长波平顺性参数计算多采用以轨道点法向偏移量代替矢距差(即设计矢距与实测矢距之差)的近似计算方法。由于该算法忽略实测弦线端点偏差的影响,导致轨道实测轨向(高低)计算结果与严密算法计算结果存在一定的偏差。鉴于现有近似算法存在准确度低的缺点,文中在现有近似算法的基础上提出一种改进算法,并通过对轨道实测坐标数据的计算和对比,验证改进算法的可行性和准确性,并提高高铁轨道中长波平顺性参数计算结果的准确度,可为高速铁路轨道精测与精调提供参考。     

线性矩法的特点评析和应用问题

介绍了线性矩法的无偏估计与直接计算的关系，讨论了在概率权重矩计算过程中各系列之间的高度相关性及其对结果的影响，建立了直接计算线性矩法的Cv和Cs近似公式，叙述了适线问题和相应的经验频率公式。文中认为，水文频率计算时，由于资料的随机性和处理方法上的概化性，故用任何计算方法得到的结果，具有不同程度的不确定性，只能作为估计的初值，需通过时空上综合平衡，再经合理性分析和调整后，才能取用。     

相似流域选择的模糊集模型与方法

提出水文计算中相似流域选择的模糊集模型与方法,以改进水文计算中选择相似流域的经验性方法.原则上模型也可用于其他水文相似问题.     

Comparison of geotechnical uncertainties linked to different soil characterization methods

One of the essential inputs in settlement prediction models is the soil modulus, which may be obtained from laboratory tests or estimated from in situ measurements. The total uncertainty in predicting the confined modulus of a sandy soil is quantified with data from side-by-side in situ testing using the standard penetration test, the static cone penetration test, the light dynamic probing and the laboratory oedometer test. To estimate transformation errors, correlations are proposed between in situ and laboratory data. The results indicate that similar magnitudes of total uncertainties are associated with the in situ methods, which are approximately twice as high as those from the direct oedometer method. The quantified uncertainties are an important input for reliability-based designs of foundations under similar soil conditions.     

A method for the analysis of large vertically loaded pile groups

An iterative method is described for the analysis of vertically loaded pile groups with a large number of vertical piles. The individual pile response is modelled using load-transfer (t–z) curves while pile–soil–pile interaction is determined using Mindlin's solution. The present method not only keeps all the advantages of the so-called ‘hybrid method’, but also makes it possible for practising engineers to solve problems of large non-uniformly arranged pile groups in a time-saving way using a personal computer. Good agreement between the present method of analysis and the direct method is observed. A case history is analysed and the computed response of a large pile group compares favourably with the field measurement. Copyright © 1999 John Wiley & Sons, Ltd.     

Employing a variable permeability model in numerical simulation of saturated sand behavior under earthquake loading

Despite advances in the numerical analysis of saturated sand behavior under earthquake loading, accurate prediction of liquefaction-related phenomena by numerical simulation remains a challenge. Variation of the coefficient of permeability is a key issue which has not obtained due attention in most previous modeling. In this study, a revised form of a recently proposed variable permeability function was implemented in a fully coupled dynamic model adopting modern two-surface plasticity constitutive law to evaluate the effects of permeability variations on the results of numerical modeling. The variable permeability model is comprised of a simple function relating the permeability coefficient of soil mass to the excess pore water ratio. In this study, the constants of the variable permeability function were attained based mainly on theoretical evidence and experimental observation. Well-documented centrifuge experiments were examined to evaluate how well the proposed model captures the main features of soil response to earthquake loading. The results indicate that the proposed function greatly enhanced the capability of numerical modeling to predict the behavior of saturated sand under cyclic loading. Particularly, the variable permeability model with proposed constants significantly improved the amount of liquefaction-induced settlement predicted by numerical modeling.     

时间滑动相关方法在SST可预报性及可信计算时间研究中的应用

将时间滑动相关方法 STC(sliding temporal correlation)用于研究混沌系统和海洋环流模式的可信计算时间RCT(reliable computation time),Lorenz混沌系统的数值试验表明用STC求得的可预报时间和可信计算时间,与使用传统误差限方法所得结果一致,证明了其有效性。对海洋环流模式LICOM和NEMO的研究发现:1.当海洋模式以非耦合的方式运行时,试验的结果表明其海表温度SST的可信计算时间较长,平均达到6个月以上,这主要是由于海洋模式的运行过程中,采用恢复性边界条件使模拟结果不会太过偏离观测值。对于强迫场从1月开始的试验,LICOM模式的SST可信计算时间在赤道东太平洋和西北太平洋地区存在RCT低值区,其数值不超过2个月。而NEMO模式在赤道太平洋地区全是RCT高值区,NEMO模式的RCT低值区域出现在赤道外的太平洋和大西洋中纬度地区,强迫场从7月开始的试验,RCT纬向平均分布与1月有相反的形式。2.海洋模式以耦合方式运行时,由于去掉了恢复边界条件作用,海洋模式预报的SST可信计算时间明显减小,年平均RCT为1个月左右。按季节平均得到的RCT变化不大,在30~40天之间,RCT的大值区春季位于南半球,而秋季位于北半球,可达2个月以上。耦合模式中所模拟的500 h Pa高度场的RCT与单独运行的大气模式所得结果相差不大,仍在2周以内。3.无论是按季节平均还是按海区平均所得到的RCT分布,都在30~60天左右,只有极少数区域在特定季节可以达到80天以上,这说明在海气耦合模式中,由于计算不确定造成的可预报上限一般不超过2~3个月,这比使用资料分析得到可预报期限短很多,因此根据木桶原理,RCT可能是制约海气耦合模式SST预报能力的一个重要因素。