挡土墙黏性分层填土土压力及开裂深度的计算

挡土墙后分层填土过程中,土压力的生成与分布情况直接影响挡土墙的设计。利用Mohr-Coulomb屈服面非相关联的Drucker-Prager准则作为塑性势面,对墙后黏性分层填土过程中作用墙背上的土压力进行了有限元计算。将数值计算结果与广义土压力的计算结果进行比较,结果显示:有限元计算的土压力分布比广义土压力公式计算的更加合理;由广义库伦土压力公式计算出来的零压力区与塑性理论计算的开裂深度相吻合,进一步证实了分层填土使用塑性理论和有限元进行计算结果的可靠性。建议挡土墙后填土尽量考虑低塑性土进行分层填筑,降低填土的开裂深度。     

2D and 3D stability analysis of slurry trench in frictional/cohesive soil

A 2D and 3D kinematically admissible rotational failure mechanism is presented for homogeneous slurry trenches in frictional/cohesive soils.Analytical approaches are derived to obtain the upper bounds on slurry trench stability in the strict framework of limit analysis.It is shown that the factor of safety from a 3D analysis will be greater than that from a 2D analysis.Compared with the limit equilibrium method,the limit analysis method yields an unconservative estimate on the safety factors.A set of examples are presented in a wide range of parameters for 2D and 3D homogeneous slurry trenches.The factor of safety increases with increasing slurry and soil bulk density ratio,cohesion,friction angle,and with decreasing slurry level depth and trench depth ratio,trench width and depth ratio.It is convenient to assess the safety for the homogeneous slurry trenches in practical applications.     

论非单调推理在日常思维中的应用

知识是人类理性思维不断作用于客观世界的结果。在我们的日常思维中,离不开两种基本的推理:必然性的推理和或然性的推理。在前一种推理中,数学和形式逻辑起主要作用。而后一种推理在日常生活中运用的可能更普遍,而且更广泛地使用非形式推理。非单调推理就是一种非必然性的推理,它的不确定性、语境依赖性和容错性等特征,是人们日常思维的重要工具。     

The development of cutoff scores on a WISC-R in the multidimensional assessment of gifted children

The summed scores of the WISC-R dyad, Vocabulary and Block Design, were cross-tabulated with full scale WISC-R scores for 249 children referred to a gifted program. The initial results indicated that the Vocabulary-Block Design dyad could be a useful tool in predicting full scale IQ for some children and thus leave time available for other types of assessment of students.     

桥梁基础工程中基于CPTu的粘性土不排水抗剪强度确定方法

为了给南京长江四桥基础工程设计与分析提供可靠的长江漫滩粘性土不排水抗剪强度Su参数,采用国外引进的孔压静力触探(CPTu)测试系统进行了现场原位试验,并以高质量土样的室内试验作为参考,对几种基于CPTu的Su确定方法进行了对比与评价,同时对所提出的圆锥系数Nk值进行了验证.试验结果表明:圆锥系数Nkt,Nke,N△u的...     

泥浆粗粒材料对泥水盾构泥膜闭气时间的影响

通过自制仪器,对添加有不同含量粗粒材料的泥浆进行成膜闭气试验,分析泥浆中粗粒含量对泥膜闭气时间的影响,以揭示含粗粒材料泥膜的闭气机理并根据不同含量粗粒材料泥浆成膜效果和闭气性能的差异分析;研究粗粒材料、地层和泥浆颗粒形成的网架结构对泥膜闭气性的影响,以确定提高泥膜闭气性能的粗粒材料合理添加量。结果表明,添加的轻质砂能有效加快泥膜形成及增强泥膜的闭气性能,当泥浆中轻质砂添加量大于1.8g/L时,泥膜的闭气时间有较大的提升,但当添加量达到3g/L时,增加轻质砂添加量对泥膜闭气时间提升效果下降。     

Convexity-preserving interpolation of trigonometric polynomial curves with a shape parameter

In computer aided geometric design(CAGD) ,it is often needed to produce a convexity-preserving interpolating curve according to the given planar data points. However,most existing pertinent methods cannot generate convexity-preserving in-terpolating transcendental curves;even constructing convexity-preserving interpolating polynomial curves,it is required to solve a system of equations or recur to a complicated iterative process. The method developed in this paper overcomes the above draw-backs. The basic idea is:first to construct a kind of trigonometric polynomial curves with a shape parameter,and interpolating trigonometric polynomial parametric curves with C2(or G1) continuity can be automatically generated without having to solve any system of equations or do any iterative computation. Then,the convexity of the constructed curves can be guaranteed by the appropriate value of the shape parameter. Performing the method is easy and fast,and the curvature distribution of the resulting interpolating curves is always well-proportioned. Several numerical examples are shown to substantiate that our algorithm is not only correct but also usable.     

具有高阶耗散项指数的Cauchy问题

利用初值扰动法,讨论了Cauchy问题中的一类具有高阶耗散项指数对严格双曲型方程组解的影响,并得到发生爆破时生命跨度的范围.     

圆锥曲线定义在解题中的应用

现行高中教材中的圆锥曲线既是教材的重要的基本内容,也是解决许多问题的一种方法。本文通过实例,从求解离心率、最值和轨迹等问题方面,讨论了圆锥曲线定义在解题中的重要性以及它的广泛应用。     

Construction of an ultra-deep diaphragm wall: a case study

This paper presents a case study on an ultra-deep diaphragm wall with a depth of 110 m constructed in Ningbo City. The in-situ application shows that using Bauer BC40 cutter machine in conjunction with cutter wheels specified for different strata would be qualified for constructing the 110 m diaphragm wall with high efficiency and precision given that the quality of slurry and poured concrete can be guaranteed. The ground settlement can be effectively controlled by using the overlapping construction method. Sliding failure as a whole characterized by pronounced lateral deformation is likely to occur in the upper muddy clay layer due to its high compressibility and sensitivity. In contrast, local collapse of trench walls tends to happen in the sandy silt strata. Furthermore, careful attention should be paid to sandy silt during the entire construction period as the vertical displacement of the sandy silt continues to develop even after concrete pouring     

改性水玻璃浆液在粉细砂地层中注浆加固的应用

在合肥轨道交通2号线土建T J04标段的东一环路站到铜陵路站区间采用盾构接收施工的背景下,对复杂环境下采用改性水玻璃来注浆加固端头土体的关键技术进行阐释,准确分析盾构机在粉细砂层迸洞和出洞的注意事项和关键要点,这有利于施工人员针对性的施工,确保盾构机顺利进出洞.同时,这还能有效控制其对周边土质的影响,不致影响周边建筑的...     

Resuspension of wall deposits in spray dryers

Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.     

Cognitive characteristics of children with mathematics learning disability (MLD) vary as a function of the cutoff criterion used to define MLD

Researchers of mathematics learning disability (MLD) commonly use cutoff scores to determine which participants have MLD. Some researchers apply more restrictive cutoffs than others (e.g., performance below the 10th vs. below the 35th percentile). Different cutoffs may lead to groups of children that differ in their profile of math and related skills, including reading, visual-spatial, and working memory skills. The present study assesses the characteristics of children with MLD based on varying MLD definitions of math performance either below the 10th percentile (n = 22) or between the 11th and 25th percentile (n = 42) on the Test of Early Math Ability, second edition (TEMA-2). Initial starting levels and growth rates for math and related skills were examined in these two MLD groups relative to a comparison group (n = 146) whose TEMA-2 performance exceeded the 25th percentile. Between kindergarten and third grade, differences emerged in the starting level and growth rate, suggesting qualitative differences among the three groups. Despite some similarities, qualitative group differences were also observed in the profiles of math-related skills across groups. These results highlight differences in student characteristics based on the definition of MLD and illustrate the value of examining skill areas associated with math performance in addition to math performance itself.     

On the dissipation of negative excess porewater pressure induced by excavation in soft soil

INTRODUCTION Since Terzaghi founded his one-dimensionalconsolidation theory, the studies on consolidation ofsoft soil have been made by many researchers (Gray,1945; Gibson et al., 1967; 1981; Schiffman and Stein,1970; Xie, 1994; Xie et al., 2002a). However, al-though as we all know, negative excess porewaterpressure will be induced by unloading in excavation,the dissipation of the negative pressure and its effectsare rarely studied because of their complexity (Chenand Wen, 1999; …     

Electrostatic force on the rectangular shield wall of a strip transmission line

For a strip transmission line shielded by rectangular walls,the Green‘s function is helpful to construct the variation expression of the electrostatic energy.Thomson theorem is employed to determine the charge distribution on the strip.The electrostatic force on each side of the rectangular shield wall is achieved by using the principle of virtual work.The results is easy to be obtained by computerized calculation.     

A refinement of scaling laws in wall turbulence

As a universal conclusion of turbulent scale, scaling laws are important to the research on statistic turbulence. We measured two-dimensional instantaneous velocity field in turbulent boundary layers of flat plate with the momentum thickness Reynolds number Reθ=2 167. Scaling laws have different forms in different wall distance and scale. We proposed an expected scaling law and compared it with the She-Leveque （SL） scaling law based on the wavelet analysis and traditional statistical methods. Results show that the closer to the wall, the more the expected scaling law approached to the SL scaling law.     

旋转变径圆管内螺旋流的LDV流速测量

针对旋转变径圆管内螺旋流场激光多普勒测速(laser Doppler velocimetry,LDV)存在的窗口振动、光束难聚焦与旋转多普勒效应等问题,设计了同轴双带驱动LDV实验装置。采用折射率匹配和光路计算相结合的方法,实现了其速度场的二维LDV测量,得到了不同壁面旋转率下变径圆管内螺旋流的切向、轴向速度分布。实验结果表明:旋转与螺旋流同向时,切向速度明显增加,最大切向速度随旋转率的增加率约为10%/N,最大切向速度点向边壁移动;当旋转率与螺旋流自身旋转率接近时,外涡流区几乎消失;旋转与螺旋流反向时,切向速度随之减小,最大切向速度随旋转率的减小率约为8%/N,最大切向速度点向轴心移动;不论壁面正反旋转,近壁区轴向速度都产生了层流化的趋势。     

Prediction of wall deposition behaviour in a pilot-scale spray dryer using deposition correlations for pipe flows

INTRODUCTION Abbott (1990) reported that wall deposition inspray dryers may pose a potential fire risk and com-promise hygiene requirements, and reduce productquality and yield. Spray dryer hazards include igni-tion of explosible dust clouds, dust deposits, bulkpowder deposits and flammable vapour. Kieviet(1997) noted that wall deposition affected the resi-dence time distribution of particles, and particularlythat an important factor in determining residencetimes with high wall deposition…     

Primary splenic carcinosarcoma with local invasion of chest wall: a rare case

We herein present a case of carcinosarcoma arising as a primary lesion in the spleen with the presence of local invasion of chest wall prior to widespread metastasis all over the body of a female aged 64 years. The detailed information of therapy and imaging evidences of morphology, histology, and immunohistochemistry are fully provided. To the best of our knowledge, this is the fifth reported case of a primary splenic carcinosarcoma and even the first case to be described with local invasion in the mongoloid. Carcinosarcoma that develops in the spleen with local invasion is extremely rare.