Fuzzy prediction of soil strength based on water content and composition

Sixteen samples representing various paddy field soils of the main rice-planting regions in South China, with their characteristic values, are listed, by which means the soil strength of any other paddy field soil can be fuzzily predicted when its water content, sand content and clay content are given. Illustrative examples show that the result of prediction seems to be acceptable in engineering practice.     

Relationship between bearing capacity and depth of soft layer of paddy fields in South China

The bearing capacity of paddy field in South China was measured with a kind of penetrometer. A straight line relationship is valuable in summarizing the dependence of bearing capacity on depth of soft soil layer.     

Prediction of paddy soil normal adhesion to steel surfaces by fuzzy logic

Numerous data concerning paddy soil composition, water content and soil-steel normal adhesion were collected in South China during 1974-1983. The fuzzy logic relation of adhesion with clay content and water content was derived, by which paddy soil adhesion to steel surfaces was predicted if soil composition and water content were known.     

Correlation dimension of paddy soil strength in China

Embedding phase space R^m is reconstructed from the spatial series g(x) of cone indices measured in two paddy fields near Nanjing, China. The correlation dimension D₂^m for each field is derived from the correlation integral C^m(r) and the neighbours distance r in log–log scale. Results show D₂^m increases as m, and tends to 5.0, which expresses the estimate of correlation dimension for each soil strength profile measured.     

Slip-line field solution for ultimate bearing capacity of a pipeline on clay soils

A slip-line field solution is presented for the ultimate bearing capacity of the pipeline on a purely-cohesive clay soil, taking into account of circular configuration of the pipe, the pipe embedment, and the pipe-soil interfacial cohesion. The derived bearing capacity factors for a smooth rigid pipe may degenerate into those for the conventional rectangular-shaped strip footing while the pipe embedment approaches zero. Parametric studies indicate that, the pipe-soil interfacial properties have much influence on the bearing capacity for the pipe foundation on clayedy soils.     

The general rheological model of paddy soils in south China

Analyses and experiments show that the Burgers model can be accepted as a general rheological model of paddy soils in South China, among which most are clays. Orthogonal tests and variance analyses show that the effect of soil conditions (mechanical composition, water content, bulk density) on rheological parameters is particularly significant, while that of loading conditions (shape and size of bearing surface, load) is practically not significant.     

Propagation of elastic waves in water-saturated soils

A brief review of the literatures on the titled subject is given. A set of wave equations, taking the inertial coupling effect between soil skeleton and pore water into account, are established for saturated soils. The preliminary analysis shows that the nature of wave propagation is mainly influenced by permeability coefficient,k. There are three types of waves, two (P-and S-wave) propagating through soil skeleton and one(P-wave) through pore water. For a soil with large value ofk, compression wave velocity through pore water will be greater than that through single-phased water, and ask→∞, the former could be times as great as the latter. For a soil with extremely low permeability, the compression wave velocity could be either less or greater than that through single-phased water, depending on the rigidity of the soil passing through. Some phenomena observed from tests presented in the literature may be reasonably explained by the proposed theory herein, and thus more reliable parameters of soil could be obtained from wave velocity measurements. Further studies on this subject are still needed. This paper is a part of the dissertation of the first author for the Ph.D. degree, the second author is his advisor.     

Determination of in situ parameters of sandy soils for off-road vehicle mobility

This study focuses on the development of a methodology for the determination of some in situ parameters for off-road vehicle mobility on sandy soils. The stress field in the vicinity of and at the interface between a wedge and soil was determined by solving the stress equations using the method of characteristics. The governing equations were solved numerically by using backward finite difference method. The proposed method allows the prediction of any two of the in situ soil parameters δ, φ, and γ (respectively, the interfacial friction angle between the material of a wedge penetrometer and the soil, the internal friction angle, and the unit weight of the soil), given the value of any one of them and the results of penetration tests of two different apex angle wedges. The predictions and the measured values are in agreement.     

Dispersion and clustering of bidisperse particles in isotropic turbulence

A statistical kinetic model describing the dispersion and clustering of particles with different inertia in homogeneous turbulence is presented. The model developed is used for calculating the relative velocity, the radial distribution function, and the particle collision kernel in a stationary bidisperse suspension. The results obtained are compared with the data of a direct numerical simulation.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, 2005, pp. 94–107. Original Russian Text Copyright © 2005 by Alipchenkov and Zaichik.     

Effect of particle clustering on the gravitational settling velocity in homogeneous turbulence

Astatistical model of the gravitational settling velocity of clusters in homogeneous isotropic turbulence is developed. The effects of particle hydrodynamic interaction, inertia, size, and volume fraction on the particle settling velocity component attributable to particle clustering are analyzed.     

Fluidization in combined acoustic-magnetic field for mixtures of ultrafine particles

Four kinds of SiO2 （5-10 nm）＋ Fe3O4 （44.8 μm） particle were fluidized in a sole acoustic field, a sole magnetic field and a combined acousticmagnetic field. Introduction of a single field, 100 dB/40-60 Hz acoustic or 10 mT magnetic, could suppress plugging and channeling and reduce the superficial minimum fluidization gas velocities, Umf. Combination of both acoustic and magnetic fields demonstrated even more promising results, especially more significant reduction of Umf.     

Improvement of a power tiller cage wheel for use in swampy peat soils

This study was aimed at investigating traction performance of a cage wheel for use in swampy peat soils in Indonesia. The tests were conducted in a soil bin filled with peat soil taken from the swampy areas. A set up was developed to measure tractive performance of a single cage wheel. Deep sinkage and high wheel slip were identified as the major problems of using the existing cage wheel design in swampy peat soils. The results revealed that increasing the lug angle from 15 to 35° and the length of lug improved the tractive performance of the cage wheel significantly, while increasing the number of lugs from 14 to 18 and width of lug did not improve the tractive performance significantly. A cage wheel with lug size 325×80 mm, 35° lug angle, 14 lugs (26° lug spacing), with 2 circumferential flat rings installed on the inner side of the lugs, out performed the other settings for use with power tillers in swampy peat soils.     

The application of Moire interferometry in the measurement of displacement field and strain field at notch-tip and crack-tip

This paper presents the application of Moire interferometry in measuring the displacement and strain field at notch-tip and crack-tip before and after crack propagation. The experiment is carried out using a three point bending beam with a notch. TheN _x andN _y fringe patterns representing displacement field, and the ΔN _x/Δx and ΔN _γ/Δγ fringe patterns representing the strain field are obtained. The sensitivity of the measured displacement is 0.417 μm per fringe order. The displacement and strain distribution along the sectionx=0 have been worked out according toN _x andN _γ fringe patterns. The project supported by Chinese Academy of Sciences and National Natural Science Foundation of China     

Phase field modeling of damage in glassy polymers

Failure mechanisms in amorphous polymers are usually separated into two types, shear yielding and crazing due to the differences in the yield surface. Experiments show that the yield surface follows a pressure modified von Mises relation for shear yielding but this relation does not hold during crazing failure. In the past different yield conditions were used to represent each type of failure. Here, we show that the same damage model can be used to study failure under shear yielding and crazing conditions. The simulations show that different yield surfaces are obtained for craze and shear yielding if the microstructure is included explicitly in the simulations. In particular the breakdown of the pressure modified von Mises relation during crazing can be related to the presence of voids and other defects in the sample.     

地磁场在导航定位系统中的应用

阐述了地磁匹配导航的基本原理及相关地磁场理论,介绍了国内外应用地磁导航的动向及发展现状,提出了地磁导航系统中三个方面的关键技术:一是导航区域地磁数据库的建立;二是载体上磁力仪的实时测量;三是地磁匹配算法。同时,结合有关地磁建模方法、地磁测量补偿算法及地磁匹配导航定位算法,分析了地磁导航存在的主要问题,指出了发展地磁导航应采取的必要措施,为下一步地磁导航的深入研究明确了方向。     

深部地下工程岩爆预测的筛选蚁群聚类算法

为了提高仿生聚类算法的计算效率,对传统的蚁群聚类算法进行改进,采用数据合并机制提出了一种筛选蚁群聚类算法。采用筛选蚁群聚类算法,在岩爆工程实例资料分析的基础上,基于工程类比的思想判断岩爆的发生状态,提出了一种深部地下工程岩爆预测的新方法。通过多个煤矿深部地下工程岩爆实例的应用研究证明,和传统的蚁群聚类算法相比,在不显著增加计算难度和复杂度的情况下,新算法对工程实例的判断准确率更高,其准确率达92%,计算效果更好;而且,计算速度有较大幅度的提高,其计算时间缩短近40%,说明新算法的计算效率更高。因此,筛选蚁群聚类算法是一种比较实用的岩爆预测新方法,值得在深部地下工程岩爆研究领域推广应用。     

Generation of linear and nonlinear waves in numerical wave tank using clustering technique-volume of fluid method

A two-dimensional(2D) numerical model is developed for the wave simulation and propagation in a wave flume.The fluid flow is assumed to be viscous and incompressible,and the Navier-Stokes and continuity equations are used as the governing equations.The standard k-ε model is used to model the turbulent flow.The NavierStokes equations are discretized using the staggered grid finite difference method and solved by the simplified marker and cell(SMAC) method.Waves are generated and propagated using a piston type wave maker.An open boundary condition is used at the end of the numerical flume.Some standard tests,such as the lid-driven cavity,the constant unidirectional velocity field,the shearing flow,and the dam-break on the dry bed,are performed to valid the model.To demonstrate the capability and accuracy of the present method,the results of generated waves are compared with available wave theories.Finally,the clustering technique(CT) is used for the mesh generation,and the best condition is suggested.     

Spatial distribution of soil forces on moldboard plough and draft requirement operated in silty-clay paddy field soil

Spatial distribution of soil forces on the surface of plough is an important aspect that can help engineers for improving efficiency of tillage implement. It was analyzed at eleven different points of the moldboard plough with the help of sensors accompanied with the virtual instrument developed in LabView software with the aid of other supporting instruments. It was observed that soil forces increased with an increase in speed and depth. Depth changed soil forces more at upper parts than lower parts whereas speed affected rear parts more than the front part of the plough. Draft forces followed almost similar trend and least value of 308.17 N experimental draft force was found at 1 m/s speed and 5 cm depth under 33% moisture content. Cumulative soil forces found too smaller than the draft as they represented the force spatial distribution of specific parts of plough. It was observed that sensor technology provided real time picture of force variation during tillage process that could save time and effort.     

水下磁异常定位中两种矢量磁力仪配置方式的比较

在简述水下磁异常定位原理的基础上,提出了八单轴和十单轴两种矢量磁力仪配置方式,推导了两种配置方式下磁场大小及梯度的量测方程,对磁场大小及梯度的解算精度进行了比较分析。数值仿真了磁场大小及梯度、载体相对位置误差与测量基线长△X之间的变化关系,结果表明这些误差都随△X加大而增长。相比于八单轴磁力仪配置,十单轴磁力仪配置方式中磁场大小和梯度计算精确,定位误差很小,在水下磁定位实验中应选用十单轴磁力仪配置方式。     

正交异性材料平面裂纹尖端应力场

根据正交各向异性材料力学性能确定出了用应力函数表示的弹性力学基本方程,利用坐标变换和复变函数方法求解了正交异性材料平面裂纹体的应力边值问题。借鉴一般断裂力学解法构造了I型和II型裂纹问题的应力函数,推导出了正交各向异性板裂纹尖端区的奇异应力场。通过数值计算说明了裂纹尖端应力表达式的正确性,验证了裂尖前沿应力变化规律,即σx与材料特征参数h2成正比,而σy和τxy不随材料特性变化。