Raymond J. Krizek

Preparation and identification of clay samples with controlled fabric

Abstract Techniques have been developed to prepare reasonably homogeneous, reproducible bulk samples of a kaolinite clay (Hydrite 10) with predetermined microfabrics and to reliably identify these microfabrics both quantitatively and qualitatively. Eight samples with quite diverse histories were produced in the laboratory by controlling the chemistry of the clay-water system, the consolidation stress path (either isotropic or anisotropic), and the magnitude of the consolidation stresses. The fabrics of these samples are identified and quantified by the combined use of scanning electron microscopy, optical microscopy, and X-ray diffractometry, and reasonably comprehensive appraisals of particle associations and orientation are obtained. Anisotropic consolidation was found to induce a preferred particle orientation, whereas isotropic consolidation tended to provide basically random samples. The anisotropically consolidated samples from dispersed slurries exhibited somewhat greater particle orientation than those from flocculated slurries, and, although considerable particle orientation occurred at low values of the consolidation stress, increases in the major principal consolidation stress did accentuate the particle orientation. The presence of domains or small groups of particles is suggested in certain samples, especially in those consolidated isotropically.

LABORATORY TESTING OF CHEMICALLY GROUTED SAND

The effect of 14 parameters, associated with specimen preparation, handling, and testing, and with soil characteristics, was evaluated experimentally for laboratory prepared specimens of chemically grounted sands. Over 200 unconfined compression tests were conducted, and results are presented and comparisons are made in terms of unconfined compressive strength and tangent modulus at 50% of maximum stress. Curing environment, curing time, specimen size, grain size, and grain size distribution are the parameters that affect significantly the observed mechanical behavior of grouted sands. The results of this study were used in the development of ASTM Laboratory Preparation of Chemically Grouted Soil Specimens for Obtaining Design Strength Parameters (D 4320).

Compaction fabrics of pelites: experimental consolidation of kaolinite and implications for analysis of strain in slate

Abstract Compaction of clay and shale results in large reductions in volume as pore water is expelled. Preferred orientation of the platy minerals increases with compaction strain and loss of porosity according to the March-Owens model. This relationship has been studied quantitatively by experimentally consolidating kaolinite clay from slurries and analyzing the resulting fabrics with the X-ray pole figure goniometer and scanning electron microscope (SEM). ‘Initial’ porosity corresponds to the onset of the strain recorded by the preferred orientation; and the values of 0.78 for dispersed slurries and 0.76 for flocculated slurries reflect the electrostatic forces between the clay platelets. ‘Initial’ porosities of recently deposited fine silt and clay are in the range of 0.60-0.90 and are a function of grain size and mineralogy. Loss of this ‘initial’ porosity has a large effect on the subsequent development of slaty cleavage. Matrix methods were used to model deformation paths for slates in the Welsh slate belt. Preferred orientation of mica and ellipsoidal shapes of ‘reduction’ spots were simulated for one locality by loss of a 0.60 ‘initial’ porosity, a 6° tilt of the beds and horizontal shortening involving plane strain. Strain determinations for shales and slates should include the large reduction in volume.

A general procedure for simulating EPR spectra of partially oriented paramagnetic centers

Abstract A general procedure for simulating EPR spectra of partially oriented paramagnetic centers is presented. The procedure is applied to the systems of [Ni(maleonitriledithiolato) 2 ] − in oriented nematic N -(4′-methoxybenzylidene)4- n -butylaniline liquid crystal and to consolidated clays. The Ni(mnt) 2 − case is unusual in that the long, in-plane molecular axis tends to align with the liquid crystal, while for the clay, no g -tensor axis is colinear with the axis of orientation. With the present development, the degree of orientation in a wide range of partially ordered systems can now be quantitatively analyzed.

Effects of high prequalification requirements

When designing a set of prequalification requirements, the first objective is to select the basic factors that are deemed appropriate to scrutinize, and the second objective is to establish the threshold for each of these factors to evaluate the capability and capacity of the bidders on a given project; together, these factors and the limits imposed on each constitute the basis for qualifying or disqualifying each of the bidders. To obtain the desired prequalification results and the consequent quality delivery of a project, both selecting the factors and determining the limits for each factor are crucial and must be given careful attention with due consideration of the prevailing environment (including market conditions, deadlines, need for technology transfer, etc.). In this study it was found that an improper design of prequalification requirements seriously affected the progress and cost of projects, provided opportunities for collusion, and encouraged the obtaining of contracts through improper practices. Based on an analysis of data from 30 Taipei Mass Rapid Transit projects, together with information gleaned from numerous interviews with contractors, consultants, and clients, it is shown that a risk-taking attitude by the Government and the establishment of relatively low prequalification requirements would be more conducive to achieving a desirable balance among (a) satisfying the schedule and sequence of contracting, (b) obtaining lower prices by an increase in competition, (c) procuring the timely delivery of a quality project, and (d) fostering the growth of local contractors.

Resilient Properties and Fatigue Damage in Stabilized Recycled Aggregate Base Course Material

A stabilized fiber-reinforced base course material composed largely of recycled concrete aggregate with small amounts of portland cement and fly ash was subjected to repeated flexural loading to evaluate its resilient properties and progressive accumulation of fatigue damage. Cyclic load-deformation data were recorded continuously during the entire fatigue life until fracture to determine (a) the magnitude and variation of cumulative plastic strain and dynamic elastic modulus as a function of the number of loading cycles, (b) a range for the resilient modulus, and (c) the effect of fiber inclusions on the dynamic material properties and rate of damage accumulation. The extent of fatigue damage was calculated as a fatigue damage index, which is based on the cumulative energy dissipated (absorbed) during cyclic loading. All beam specimens used in this experimental program contained (by weight) 4 percent cement, 4 percent fly ash, and 92 percent recycled aggregate; the fiber-reinforced specimens contained an additional 4 percent (by weight) hooked-end steel fibers. Results show that the resilient modulus in flexure varies between about 2.75 GPa (400,000 lbf/in2.) and 10.4 GPa (1.5 million lbf/in.2) and the degradation of the dynamic elastic modulus does not exceed 25 percent of the initial modulus. Miner’s Rule of linear summation of damage is applicable to unreinforced material but not to fiber-reinforced material. In general, a modest amount of reinforcing fibers was very effective in retarding the rate of fatigue damage accumulation in this lean cementitious composite.

Effect of Non-Darcian Flow on Time Rate of Consolidation

Abstract 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.

Hydrodynamic dispersion in a single rock joint

This paper deals with the hydrodynamic dispersion of a contaminant in a single rock joint; the effects of molecular diffusion due to a concentration gradient are considered to be negligible relative to the hydrodynamic effects, and the surfaces of the rock joint are assumed to be geochemically stable. Both laminar and turbulent flow are treated, and the constitutive properties of the contaminant are assumed to be the same as those of the parent fluid. Within this framework and with a knowledge of the boundary condition at the origin, the time‐dependent average concentration at any point within the joint can be found by using either (a) a Taylor series expansion or a polynomial approximation for this boundary condition, or (b) an incremental approach based on the principle of superposition. Experimental data are given to substantiate the acceptability of the assumptions employed.

Effect of non-darcian behavior on the characteristics of transient flow

Abstract A modified form of the boundary value problem describing the one-dimensional transient flow in clay soils is formulated to include a non-Darcian flow law with a threshold gradient. The solution is obtained by matrix techniques, and calculated results are compared with results obtained from conventional one-dimensional theory.

COMPLEX VISCOSITY OF A KAOLIN CLAY

The complex viscosity of a material is a two-component quantity, comprising real and imaginary parts. The real part of the complex viscosity is often very useful because in many materials it approaches the ordinary steady-flow viscosity at low frequencies. Because many materials with high viscosities are very slow in reaching a steady-flow condition, the determination of the steady-flow viscosity may be very difficult; however, an approximation can often be obtained from low-frequency values of the real part of the complex viscosity. In this study, the complex viscosity of a Georgia kaolin has been determined by measurements made on specimens subjected to oscillatory simple shear, over three decades of frequency. Other independent variables in the study are the water content of the clay and the shear strain amplitude. Data were obtained from experimental measurements in the form of values of the magnitude, or absolute value, of the complex viscosity, and the phase angle between the imposed oscillatory strain and the stress response. Empirical functional relationships are developed to relate these quantities to the independent variables, and these are in turn used to obtain the real and imaginary parts of the complex viscosity as functions of the independent variables. The results of this study indicate that the complex viscosity is not linear, but decreases approximately as a power function of the strain amplitude; the relation between the complex viscosity and the water content is approximately an inverse logarithmic one, and changes very rapidly at water contents near the liquid limit; and the phase angle increases with increasing strain amplitude approximately as a power function.RésuméLa viscosité complexe d’une substance est une quantité à deux composants, comportant des parties réelles et imaginaires. La partie réelle de la viscosité complexe est souvent utile parce que dans le cas de beaucoup de substances elle approche de la viscosité normale à écoulement stable aux basses fréquences. Parce que de nombreuses substances ayant une viscosité élevée sont très lentes à atteindre un état d’écoulement stable, la détermination de la viscosité à écoulement stable est parfois difficile. Pourtant il est souvent possible d’obtenir une approximation à partir des valeurs à basse fréquence de la partie réelle de la viscosité complexe. Dans la présente étude, la viscosité complexe d’un kaolin de Georgia a été déterminée par des mesures de specimens soumis au cisaillement oscillatoire simple, pour trois décades de fréquence. D’autres paramètres variables et indépendants dans l’étude sont la teneur en eau de l’argile et l’amplitude de l’effort de cisaillement. On a obtenu des données à partir de mesures expérimentales sous forme de valeurs de la grandeur, ou valeur absolue, de la viscosité complexe, ainsi que l’angle de phase entre l’effort oscillatoire imposé et la réponse à l’effort. Des relations empiriques et fonctionnelles sont développées dans le but de l’association de ces quantités aux variables indépendants, et ceux-ci à leur tour sont utilisés en vue d’obtenir les parties réelles et imaginaries de la viscosité complexe en tant que fonctions des variables indépendants. Les résultats de cette étude indiquent que la viscosité complexe n’est pas linéaire mais diminue de manière approximative en tant que fonction de puissance de l’amplitude de l’effort; le rapport entre la viscosité complexe et la teneur en eau est de manière approximative un rapport inverse au rapport logarithmique, et change très rapidement pour des teneurs en eau près de la limite liquide. Enfin l’angle de phase augmente avec une amplitude croissante de l’effort, approximativement selon une fonction de puissance.KurzreferatDie Komplexviskosität eines Materials setzt sich aus zwei Bestandteilen, einem wirklichen und einem imaginären Teil, zusammen. Der wirkliche Teil der Komplexviskosität ist oft sehr brauchbar, da er bei niedrigen Frequenzen annähernd der gewöhnlichen Viskosität im stationären Strömungszustand entspricht. Da viele hochviskose Stoffe eine lange Zeit in Anspruch nehmen ehe sie den stationären Strömungszustand erreichen, kann die Bestimmung der Viskosität in diesem Zustand recht schwierig sein, jedoch kann ein Richtwert häufig aus Niederfrequenzwerten des wirklichen Teils der Komplexviskosität erhalten werden. In der vorliegenden Arbeit wurde die Komplexviskosität eines Georgia Kaolins durch Messungen an Proben, die einer oszillierenden, einfachen Schubspannung unterworfen waren, über drei Frequenzdekaden hinweg bestimmt. Weitere unabhängige Variable in der Untersuchung sind der Wassergehalt des Tones und die Amplitude der Schubspannung. Aus experimentellen Messungen werden Daten für die Grösse, d.h. für den Absolutwert, der Komplexviskosität und für den Phasenwinkel zwischen aufgegebener Schwingungsspannung und Formänderungsreaktion erhalten. Es werden empirische funktionelle Beziehungen entwickelt um diese Grössen in ein Verhältnis zu den unabhängigen Variablen zu bringen, und um dann die wirklichen und imaginären Bestandteile der Komplexviskosität als Funktionen der unabhängigen Variablen zu erhalten. Die Ergebnisse deuten darauf hin, dass die Komplexviskosität nicht linear ist, sondern annähernd als Potenzfunktion der Spannungsamplitude abnimmt; die Beziehung zwischen der Komplexviskosität und dem Wassergehalt ist beilaufig eine umgekehrte logarithmische, und ändert sich rapid bei Wassergehalten nabe der Flüssiggrenze. Der Phasenwinkel schliesslich, nimmt mit zunehmender Spannungsamplitude ungefähr als Potenzfunktion zu.РезюмеКомплексная вязкость материала это двухэлементная величина, содержащая истинные и мнимые части. Истинная часть комплексной вязкости часто очень пригодна, так как во многих материалах достигает она обычной вязкости стационарного поткоа при низких частотах. Ввиду того, что многие, обладающие высокой вязкостью материалы очень медленно достигают состояния стационарного потока, определение вязкости стационарного потока бывает очень трудным. Однако, можно часто получить аппроксимацию из низкочастотных значений истинной части комплексной вязкости. В настоящем исследовании, комплексная вязкость каолина штата Джорджия определяется измерениями на образцах, подвергаемых в течение трех декад частоты колебательному сгвигу. Другие независимые переменные в этом исследовании это водосодержание глины и амплитуда деформации сдвига. Данные получены были по экспериментальным измерениям в виде значений величины или как абсолютное значение комплексной вязкости иизмерениям угла сдвига фаз между наложенной колебатель¬ной деформацией и реакцией напряжения. Развивались эмпирические, функциональные соотношения, чтобы установить отношение этих величин к независимым переменным, а эти, в свою очередь, применяются для того, чтобы получить истинные и мнимые части комплексной вязкости, как функции независимых переменных. Результаты настоящего исследования означают, что комплексная вязкость не является линейной, но уменьшается приблизительно как функция мощности амплитуды деформации. Зависимость между компле-ксной вязкостью и водосодержанием приблизительно обратно логарифмическая и меняется очень быстро, когда водосодержание доходит до предела жидкости, а фазовый угол увеличивается при повышении амплитуды деформации, приблизительно как функция мошности.