软黏土的结构性及压缩特性研究

对天然土以及重塑土进行了压缩试验,分析了原状土和重塑土的压缩特征。结果表明,天然沉积软黏土具有明显的结构性特征,结构屈服应力与先期固结压力的比值σk/pc可以用来表征天然软黏土的结构性强弱程度;软黏土孔隙的组构特点是其压缩曲线不同于非结构性土的重要原因;淤泥土的结构性明显,黏质粉土结构性很弱;土体的宏观变形过程可以通过对微观结构的分析来描述,利用宏观与微观相结合的研究方法来论证土的基本特性;软黏土结构性的地域性很强,埋深较浅且处于不透水层的天然软黏土的先期固结压力较低,先期固结压力的作用使得软黏土形成结构强度,结构强度的大小是同类软黏土结构性程度强弱的重要体现;原状土和重塑土侧限压缩时的应力应变关系曲线呈上凹形,压缩模量随着荷载的增大而增长,对于成层分布的地基土而言,欲准确地计算地基沉降,应合理地选择使用随外荷载变化的压缩模量,使压缩模量随着深度的增加而增加,以符合地基土的压缩特性。得到的结论对软黏土结构性的研究和地基基础沉降计算具有一定的指导意义和工程实用价值。     

粉土压缩变形特性试验研究

通过粉土的固结试验,研究了其应变、时间、荷载之间的关系。试验结果表明,原状粉土的压缩变形主要与其作用荷载及本身含水量、孔隙比有关。通过粉土变形与时间的关系曲线,得出此粉土变形与时间符合双曲线函数,土体变形主要表现为瞬时变形,主固结时间较短,次固结较小。     

Laponite RD透明土模拟软黏土的适用性分析

评估Laponite RD透明土作为岩土实验材料的适用性。首先,以透射率作为评估透明度的指标,基于透明土透射率的测量结果,给出了Laponite RD透明土适用的实验厚度范围。其次,制备不同强度的透明土试样,进行了渗透试验、固结试验、直接剪切试验和固结不排水三轴压缩试验,将透明土的物理力学指标与天然软黏土的物理力学指标进行了对比分析。试验结果表明,Laponite RD透明土的渗透性能和天然软黏土相当,固结系数却远小于多数天然软黏土,黏聚力较多数天然软黏土略小,而内摩擦角大致处于天然软黏土的分布范围内。基于试验结果分析可知,Laponite RD透明土可较好地模拟天然软黏土的渗透性能,其次是模拟强度特性,而用于模拟压缩等变形特性时则可能与实际软黏性土相距较大。     

非饱和土等效固结特性的验证

本文基于非饱和重塑黄土的一维固结与压缩试验结果,通过将复杂多相的非饱和土视为由等效骨架相和等效流体相组成的系统,首先对非饱和土整个变形阶段的等效两相应力随时间发展变化的规律展开分析,其次考虑到其受荷瞬间气相的高压缩性,将瞬时变形从固结变形中分离出来,分析了等效骨架相的瞬时压缩变形特性,并应用等效固结变形分析方法,确定了非饱和土的等效固结系数,实现了对非饱和土等效固结特性的验证,对解决相关的实际工程问题具有一定的借鉴意义。     

考虑应力历史影响的饱和土一维非线性固结分析

引入e—lgσ＇和e—lgkv关系研究单层地基非线性固结问题,并考虑地基应力历史的影响,通过半解析法确定地基固结过程中正常同结与超固结的分界面。采用Fortran语言编制相应的计算程序ODNCAOS,并利用该程序对考虑应力历史影响的饱和土一维非线性固结的特性进行了分析。     

土体三轴试验固结过程解析

三轴试验是一种非常重要的室内试验手段,主要用于测定土体的强度和应力变形特性,具体需要借助压力室、轴向加荷系统、施加周围压力系统以及孔隙水压力量测系统等。一般来说,在三轴试验中最为重要的两个要素为排水固结阶段试样的孔压消散以及固结完成的情况,其不仅是后续剪切试验的重要依据,也是工作人员推导土体三轴剪切试验排水固结过程相关数据的依据。基于此,本文以土体三轴试验的原理和固结过程的原理为基础,重点分析了土体三轴试验的固结过程,以希冀给予广大试验研究人员一些帮助和建议,进而有效促进该领域的进步。     

水压式与敞口式薄壁取土器的对比

本文通过工程实例,对水压式与敞口式薄壁取土器采取的77组海相黏性土对比样的26项试验指标进行了统计与对比,对比结果:(1)天然状态土的物理指标与界限含水率、压缩试验等12项常规试验指标,以及固结系数、三轴固结不排水试验等6项试验指标基本一致;(2)快剪指标增大50%;固结快剪黏聚力减小10%,内摩擦角增大20%;(3)先期固结压力增大20%;无侧限抗压强度增大30%;(4)渗透系数降低60%。     

高速旋转压片机片剂压缩机理

本文分析了高速旋转压片机压片过程中压力对相对体积的影响和片剂压缩机理;分析了压缩成型中压力与片剂比表面积的关系、压力与相对体积的关系、片剂的弹性复原及裂片原因;归纳了颗粒压缩而固结成型的机制。     

土水特征曲线在非饱和土一维固结理论中的应用

采用Bishop有效应力原理,将Fredlund土水特征曲线模型应用在固结方程中,提出了非饱和土一维固结理论。假定土体固结分为两个阶段。第一阶段为不排水、不排气阶段,土体的变形只是因为气体的被压密而引起的。第二阶段为排水、排气阶段,土体的变形是因为孔隙水和孔隙气的排出而引起的,在此过程的基础上,建立了非饱和土一维固结方程,并进行了数值求解。     

控压钻井非线性模型预测控制器设计

本文提出了一种基于非线性模型预测控制器(NMPC),用于计算井涌控制过程中的环空井底压力。利用离散时间非线性系统优化方法,考虑钻头的流速,储层流入流速和储层压力的影响因素,建立控压钻井非线性模型预测控制器的模型。将所建立的NMPC模型与现场应用的比例积分导数控(PID)控制器的控制性能进行比较,结果证明NMPC对干扰的响应比PID控制器更快。     

Effect of Non-Darcian Flow on Time Rate of Consolidation

The effect of non-Darcian flow on the consolidation behavior of clay soils is studied, and its role in the extrapolation of laboratory test results to field problems is evaluated. This is accomplished by postulating a reasonably general four-parameter velocity-gradient relationship which, by proper choice of parameters, is capable of characterizing much of the published experimental data; then, this relationship is combined with the standard assumptions of classical consolidation theory to develop a nonlinear parabolic partial differential equation, which is solved by use of a finite difference technique. The stability and convergence criteria for related linear and quasi-linear equations are empirically extended to the associated nonlinear equations, and a comparison is made between various explicit and implicit finite difference schemes, with the result that a sufficiently accurate and more economical numerical solution is obtained by use of an explicit scheme. Typical solutions for various specific cases confirm and offer an explanation for the well-known phenomenon wherein the time rate of consolidation is found to decrease as the load increment decreases; also, the thickness of the consolidating layer is shown to affect the dimensionless time rate of consolidation. These conditions indicate that laboratory consolidation test results can be applied to a field situation only if appropriate stress and thickness corrections are made.     

成层地基固结性状中不同定义平均固结度研究分析

一维地基固结理论从传统的太沙基一维固结理论到成层地基一维固结理论中。由于实际地基大多由性质不一的成状土组成,成层地基固结度计算一直为人们所关注。固结度有按沉降(压缩量)定义的地基总平均固结度和按作用的平均有效应力(或所消散的平均孔压)定义(简称按平均孔压定义)的地基总平均固结度。但对实际工程对它们的大小比较讨论甚少,对实际的选取应用没有理论上的支持。本文从一般均质地基的固结度定义入手,在相对比较理想的土体条件假设下,系统的比较了它们的大小区别,并在单面排水条件下结论Us>Up是一定成立的,并且根据以有的半理论解编制了相应的计算程序来说明本文的正确性。     

欧美期刊同行评议模式发展趋势分析

[目的/意义]旨在为国内学术期刊改进同行评议及国内同行评议理论研究提供参考.[方法/过程]以Richard-Pascal-Wang[2017]同行评议模式分类模型精简版框架为分析工具,使用多维可视化方法,梳理欧美期刊13种同行评议模式,分析同行评议模式现状以及未来发展趋势.[结果/结论]欧美期刊同行评议模式呈现出参与度...     

Information technology adoption behavior life cycle: Toward a Technology Continuance Theory (TCT)

For over a decade, researchers have devoted much effort to construct theoretical models, such as the Technology Acceptance Model (TAM) and the Expectation Confirmation Model (ECM) for explaining and predicting user behavior in IS acceptance and continuance. Another model, the Cognitive Model (COG), was proposed for continuance behavior; it combines some of the variables used in both TAM and ECM. This study applied the technique of structured equation modeling with multiple group analysis to compare the TAM, ECM, and COG models. Results indicate that TAM, ECM, and COG have quite different assumptions about the underlying constructs that dictate user behavior and thus have different explanatory powers. The six constructs in the three models were synthesized to propose a new Technology Continuance Theory (TCT). A major contribution of TCT is that it combines two central constructs: attitude and satisfaction into one continuance model, and has applicability for users at different stages of the adoption life cycle, i.e., initial, short-term and long-term users. The TCT represents a substantial improvement over the TAM, ECM and COG models in terms of both breadth of applicability and explanatory power.     

横观各向同性土体二维固结孔压影响范围分析

在先假定孔压分布边界条件为一待定常数的基础上,求解了条形荷载作用下二维横观各向同性固结微分方程,得出了孔压为平面坐标和时间函数的表达式,再通过假定该待定常数为一系列具体数值时得出的固结解的结果,用反分析的方法得出孔压沿水平向消散为零的范围。得到的结论对工程实践和进一步的理论分析都具有一定的意义。     

基于集合理论的信息检索模型

本文围绕信息检索模型的数学表示，详细讨论了基于集合理论的三种模型；对简单布尔模型的基本原理及其优缺点进行了评价，并采用矢量的方法对扩展布尔检索模型进行探讨；最后重点介绍了以模糊集合理论为基础的模糊集合模型。     

The strength of composite materials loaded in uniaxial tension under pressure

This paper presents a method for the evaluation of the tensile strength of composite materials made of a soft matrix with hard inclusions. The tensile strength is calculated as the force per unit area required for the onset of plastic flow in the material. In addition to the tensile strength, the severity of the core deformation and the rate of void formation are also estimated. The results are based on an upper-bound analysis with a two parameter family of velocity fields which accounts for both non-homogeneity of deformation and void formation.The model of the composite and the family of the velocity field used here have already appeared in published articles. Moreover, the application of the present method to estimate the tensile strength in cases when ductile deformation prevails (i.e. when there is no void formation) would lead to the same results as in the previous studies based on the same model and velocity fields.New here is the completeness of the analysis. All possible flow patterns, including for the first time void forming flows, were considered. This made it possible to show that the conditions required to ensure that one or another flow pattern prevails (i.e. those conditions found here and in other articles based on the same model) are not only necessary but also sufficient, at least from a theoretical point of view.The results of this paper have not yet been confirmed experimentally. Although the general trends are in the expected direction, so far no attempt has been made to find the degree of correlation between the theory and the behavior of real materials.     

初始孔压均布的饱和土一维热固结解析解

基于热弹性力学和饱和土固结理论,通过热固结方程的建立和求解,研究了饱和土的一维热固结问题.利用有限Fourier变换及其逆变换,得到土层内部超静孔压、温度增量的解析解,并依此求出地基沉降、平均固结度的表达式.根据所得解编制了计算程序,分析了饱和土的一维热固结性状,并与Terzaghi解进行了比较.结果表明,超静孔压随时间延长最终消散为零,但在热同结过程中可能会产生负孔压;地基沉降受温度影响而减小;平均固结度按变形定义和按孔压定义是不同的:热扩散系数与同结系数的比值的大小对热同结性状有重要影响.     

The graph-theoretic field model— II. application of multi-terminal representations to field problems

This paper is a sequel to a paper entitled “The Graph-Theoretic Field Model—I: Modelling and Formulations” (1). Herein, the Theory of Multi-Terminal Representations is applied to the Graph-Theoretic Field Model to provide mathematical models of finite elements. The element models are obtained solely from the algebraic building blocks of the Graph-Theoretic Field Model, without recourse to any functional mathematics. The theory of Multi-Terminal Representations is developed for both linear and non-linear problems. Examples of the application of the theory to one- and two-dimensional field problems are presented from heat conduction and electrostatics.     

基于PSR模型的可持续发展研究

PSR是OECD(经合组织)提出的用于系统的压力、状态、响应分析的模型。本文在对社会、经济、自然环境复合系统协调发展过程中的各种因素进行深入分析的基础上,构建一类PSR复合模型,运用系统动力学的理论与方法,对社会、经济、环境系统的可持续发展进行研究,以期为政府制定未来发展规划时提供参考。