Jacek Mierczyński

Apparent Creep of Saturated Sand Caused by Intrinsic Cyclic Loading

AbstractAn interesting phenomenon, designated as an apparent creep of saturated sand, is described on the basis of experimental data obtained from triaxial quasi-drained-controlled tests. In such tests, external stresses were kept constant while the pore pressure was cyclically changed (intrinsic cyclic loading). It is a kind of cyclic loading that takes place in seabeds, where the pore pressure changes cyclically because of the action of water waves. During the experiment, both vertical and horizontal strains were recorded. It is shown that these strains gradually increase as functions of the number of loading cycles in such a way that the volume of the specimen is constant, and only the deviatoric strain increases. The experimental curve resembles the creep curve for solid materials, in which real time is replaced by the number of loading cycles. The experiments are described and discussed, and a simple model of the phenomenon observed is proposed.

Structure and Calibration of Constitutive Equations for Granular Soils

Abstract The form of incremental constitutive equations for granular soils is discussed for the triaxial configuration. The classical elasto-plastic approach and the semi-empirical model are discussed on the basis of constitutive relations determined directly from experimental data. First, the general structure of elasto-plastic constitutive equations is presented. Then, the structure of semiempirical constitutive equations is described, and a method of calibrating the model is presented. This calibration method is based on a single experiment, performed in the triaxial apparatus, which also involves a partial verification of the model, on an atypical stress path. The model is shown to give reasonable predictions. An important feature of the semi-empirical incremental model is the definition of loading and unloading, which is different from that assumed in elasto-plasticity. This definition distinguishes between spherical and deviatoric loading/unloading. The definition of deviatoric loading/unloading has been subject to some criticism. It was therefore discussed and clarified in this paper on the basis of the experiment presented.

Response of Partially Saturated Non-cohesive Soils

Abstract This paper analyses and discusses experimental results of undrained triaxial tests. The tests were performed on non-cohesive partially saturated soil samples subjected to monotonic and cyclic loading. The tests were aimed at determining the influence of saturation degree on soil’s undrained response (shear strength, excess pore pressure generation). The saturation of samples was monitored by checking Skempton’s parameter B. Additionally, seismic P-wave velocity measurements were carried out on samples characterized by various degrees of saturation. The tests clearly showed that liquefaction may also take place in non-cohesive soils that are not fully saturated and that the liquefaction potential of such soils strongly depends on the B parameter.

Mechanical Properties of Granular Soils: Triaxial versus Plane Strain Investigations

Abstract The paper compares the pre-failure behavior of granular soils investigated in the classical triaxial apparatus and in the true triaxial apparatus, under plane strain conditions. Both experiments are described within the framework of an incremental model of the pre-failure behavior of sands. The methods of tensor algebra are used to compare theoretical predictions with experimental results. The analysis presented deals with the pre-failure deformations of fully drained sand, as well as with its undrained behavior, including static liquefaction and the specific behavior of an initially dilative soil. Some key questions of soil mechanics are discussed, for instance, whether soil parameters determined from one configuration, such as triaxial conditions, can be applied in other cases.

Theoretical analysis of model seabed behavior under water wave excitation

Abstract Theoretical analysis of the behavior of a model seabed subjected to water wave excitation is presented. The experiments were performed in the wave flume at the Danish Technological University in Lyngby. Such experiments are unique in engineering sciences and therefore provide unique empirical data for testing various models of the seabed. A controversial explanation of the experiments is presented in the literature. The goal of this research was to study pore pressure changes caused by water waves and the subsequent liquefaction of the seabed. The authors of the present contribution offer their own theoretical explanation of the wave flume experiments and discuss errors found in the literature cited. The analysis is based on the classical soil mechanics, including the Biot type approach

Liquefaction Resistance of a Granular Soil Containing Some Admixtures of Fines

Abstract The paper deals with the mechanics of sand with some admixtures of fines. The basic question is whether such admixtures are liquefiable or not. Experimental results show that admixtures of fines do not essentially influence the liquefaction susceptibility of granular soils. The original experimental investigations support this conclusion.

Compaction/Liquefaction Properties of Some Model Sands

Abstract The compaction/liquefaction characteristics of two model sands are determined experimentally. One sand (Istanbul) is used in shaking table investigations, and the other (Dundee) in geotechnical centrifuge experiments. Both types of these highly sophisticated experiments are planned to be applied to test theories of seabed liquefaction. The first step of these experiments is to determine the parameters of model soils, which is the main goal of this paper.