Clarence K. Chan

Bio: Clarence K. Chan is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Liquefaction & Soil liquefaction. The author has an hindex of 18, co-authored 31 publications receiving 1769 citations.

Effects of Sample Preparation on Sand Liquefaction

Abstract: The results of undrained stress controlled cyclic triaxial tests indicated that the dynamic strength of saturated sands, remolded to the same density by different compaction procedures, was significantly different. Variations in the dynamic strength of Monterey No.0 sand were found to be in the order of —100%; however, tests on other sands indicated that the magnitude of the effect of the method of preparation used may be a function of the type of sand. Fabric studies and electrical conductivity measurements indicated that the orientation and arrangement of the contacts between sand grains were probably the primary reasons for the observed differences in the dynamic strength of Monterey No.0 sand. Comparisons indicated that specimens prepared by moist tamping or moist vibratory compaction would exhibit dynamic strengths most similar to those of undisturbed samples; however, in most cases, the strength of undisturbed samples ranged from 0% to 45% higher than that of samples prepared by moist tamping.

Evaluation of Properties of Rockfill Materials

Abstract: A modeling technique has been used to determine the properties of rockfill materials. The results indicate that the mechanical properties of the field rockfill materials can be predicted with a high degree of accuracy by a series of tests with modeled rockfill materials in the laboratory. Modeling of the rockfill materials did not materially affect the isotropic consolidation characteristics of specimens. The angle of internal friction is affected to some extent by the size of the particles in the test specimen. The volume changes during drained triaxial compression tests were at least compressive for the small specimens. The strength and deformation characteristics for all of the rockfill materials were affected by the confining pressures used in tests. A comparison of the rockfill materials of various types supports Casagrande's conclusion that materials composed of well-graded and well-rounded particles are superior in their mechanical properties to uniformly-graded angular rockfill materials.

Structure and strength characteristics of compacted clays.

Abstract: The influence of soil structure on shrinkage, swelling, swell-pressures, stress-deformation characteristics, undrained strength, pore-water pressures and effective strength characteristics is described and examples of the relationships between composition and the 'as-compacted' strength of compacted clays are presented. The influence of shear strain on soil structure is demonstrated and used to explain the effect of various methods of compaction on soil strength characteristics.

Sand liquefaction in large-scale simple shear tests

Abstract: Samples used in the study were approx 90-in. long by 42-in. wide and 4-in. thick and they were subjected to uniform stress cycles at a frequency of 4 cps. Measurements of changes in pore-water pressure and shear strain development are presented for samples prepared at relative densities of 54%, 68%, 82%, and 90%, and the results are interpreted to determine the values of stress ratio causing initial liquefaction and different degrees of shear strain, giving appropriate consideration to the effects of system compliance. It is shown that a condition of initial liquefaction could be induced in all samples, but for samples with relative densities greater than about 45%, initial liquefaction was accompanied by limited shear strains, the limiting strain potential decreasing with the relative density. The test results are compared with data from other investigations and conclusions are drawn concerning the accuracy of tests on small-scale samples and shaking table investigations.

Settlement of sands under multidirectional shaking

Abstract: Tests on samples of dry sand subjected to shaking in one, two, and three dimensions show that the settlements caused by multidirectional shaking may be significantly greater than the settlements caused by shaking in one direction only. The settlements caused by combined horizontal motions are about equal to the sum of the settlements caused by the components if they act separately. Vertical motion superimposed on horizontal motion causes an increase in settlements. By using a simple correction factor based on these findings it is shown that the settlement computed from the results of cyclic simple shear tests and a one-dimensional response analysis agrees well with the observed settlement of a clayey sand fill in the San Fernando earthquake.

Soil Behaviour and Critical State Soil Mechanics

Abstract: Soils can rarely be described as ideally elastic or perfectly plastic and yet simple elastic and plastic models form the basis for the most traditional geotechnical engineering calculations. With the advent of cheap powerful computers the possibility of performing analyses based on more realistic models has become widely available. One of the aims of this book is to describe the basic ingredients of a family of simple elastic-plastic models of soil behaviour and to demonstrate how such models can be used in numerical analyses. Such numerical analyses are often regarded as mysterious black boxes but a proper appreciation of their worth requires an understanding of the numerical models on which they are based. Though the models on which this book concentrates are simple, understanding of these will indicate the ways in which more sophisticated models will perform.

Liquefaction and flow failure during earthquakes.

Abstract: Two aspects of seismically-induced liquefaction are discussed which are of vital engineering significance: the triggering condition and the consequences of liquefaction. The triggering condition is examined with respect to liquefaction analysis, note being taken of the onset condition which is governed by cyclic strength. Consequences of liquefaction are discussed with respect to post-seismic stability analysis, in which the residual strength plays a major role. Procedures used for liquefaction analysis based on the results of in situ sounding tests are introduced, and the applicability of this method for estimating associated ground settlements is discussed. The evaluation of residual strength requires a better understanding of undrained sand behaviour. Results of extensive laboratory rests on Japanese standard sand are examined and new index parameters are proposed to quantify undrained sand behaviour better. The results of laboratory tests on silty sands are examined in the same way. AH the results are...

Influence of SPT Procedures in Soil Liquefaction Resistance Evaluations

Abstract: The purpose of this paper is to clarify the meaning of the values of standard penetration resistance used in correlations of field observations of soil liquefaction with values of N1 measured in SPT tests. The field data are reinterpreted and plotted in terms of a newly recommended standard, (N1)60, determined in SPT tests where the driving energy in the drill rods is 60% of the theoretical free‐fall energy. Energies associated with different methods of performing SPT tests in different countries and with different equipment are summarized and can readily be used to convert any measured N‐value to the standard (N1)60 value. Liquefaction resistance curves for sands with different (N1)60 values and with different fines contents are proposed. It is believed that these curves are more reliable than previous curves expressed in terms of mean grain size. The results presented are in good accord with recommended practice in Japan and China and should, thus, provide a useful basis for liquefaction evaluations in ...

Evaluating cyclic liquefaction potential using the cone penetration test

Abstract: Soil liquefaction is a major concern for structures constructed with or on sandy soils. This paper describes the phenomena of soil liquefaction, reviews suitable definitions, and provides an update...

Crushing of Soil Particles

Abstract: In order to understand the physics of the strength and stress‐strain behavior of soils and to devise mathematical models that adequately represent such behavior, it is important to define the degree to which the particles of an element of soil are crushed or broken during loading. The amount of particle crushing in a soil element under stress depends on particle size distribution, particle shape, state of effective stress, effective stress path, void ratio, particle hardness, and the presence or absence of water. Data are analyzed for single mineral soils and rockfill‐like materials and equations are presented that can be used to estimate the total breakage expected for a given soil subjected to a specified loading.