Marek Kulczykowski

Estimation of Stresses in a Dry Sand Layer Tested on Shaking Table

Abstract Theoretical analysis of shaking table experiments, simulating earthquake response of a dry sand layer, is presented. The aim of such experiments is to study seismic-induced compaction of soil and resulting settlements. In order to determine the soil compaction, the cyclic stresses and strains should be calculated first. These stresses are caused by the cyclic horizontal acceleration at the base of soil layer, so it is important to determine the stress field as function of the base acceleration. It is particularly important for a proper interpretation of shaking table tests, where the base acceleration is controlled but the stresses are hard to measure, and they can only be deduced. Preliminary experiments have shown that small accelerations do not lead to essential settlements, whilst large accelerations cause some phenomena typical for limit states, including a visible appearance of slip lines. All these problems should be well understood for rational planning of experiments. The analysis of these problems is presented in this paper. First, some heuristic considerations about the dynamics of experimental system are presented. Then, the analysis of boundary conditions, expressed as resultants of respective stresses is shown. A particular form of boundary conditions has been chosen, which satisfies the macroscopic boundary conditions and the equilibrium equations. Then, some considerations are presented in order to obtain statically admissible stress field, which does not exceed the Coulomb-Mohr yield conditions. Such an approach leads to determination of the limit base accelerations, which do not cause the plastic state in soil. It was shown that larger accelerations lead to increase of the lateral stresses, and the respective method, which may replace complex plasticity analyses, is proposed. It is shown that it is the lateral stress coefficient K0 that controls the statically admissible stress field during the shaking table experiments.

Pre-failure behaviour of reinforced soil

Abstract This paper deals with the elastic-plastic analysis of fibre-reinforced soil that is treated as a macroscopically homogeneous composite material. First, the theory of such a material is briefly described. The theory allows for straightforward determination of the initial yield surface of reinforced soil. The initial yield surface is defined as a surface, in the macrostress space, on which either the soil or the reinforcement first becomes plastic the second constituent being in an elastic state. Further loading of the composite causes the regrouping of microstresses in both constituents up to the stage at which the second constituent becomes plastic. The points corresponding to such states form, in the macrostress space, the global yield surface for reinforced soil. The global yield surface can be determined analytically only in special cases. In a general case it can be determined by numerical integration of incremental equations describing an elasto-plastic range of the composites behabiour. The global yield surface is determined for various sets of initial data. The results are compared with the limit surface defined by the rigid-plastic model of reinforced soil. Conclusions of practical importance are drawn.

The Pull-out Capacity of Suction Caissons in Model Investigations

Abstract A small-scale model experiment on the pull-out resistance of suction caissons is described. The pull-out force and suction developed within the caisson in the extraction process were recorded during the experiment. A simple breakout model, together with an elementary static formulae, is applied to predict the results obtained experimentally. There is a reasonably good agreement between the experimental results and predictions. An extensive discussion of the approach applied is included. The analysis presented in this paper is original, as it differs from other approaches mentioned in this paper, and leads to acceptable predictions. At the end, the results are also compared with another approach for predicting the capacity of suction caissons.

The Shaking Frequency Effect in the Dynamics of a Model Sandy Layer

Experimental results showing the frequency-dependent behavior of both dry and saturated sandy layers subjected to a horizontal excitation on a shaking table are presented. The largest settlements of a dry layer correspond to two specific frequencies. In the case of a saturated layer, there is a single peak frequency corresponding to the largest depth of sinking of a measuring plate in liquefied subsoil. The first peak of settlements coincides with the single peak of sinking in liquefied soil. The eigenfrequencies of the layer were estimated. A modification of the compaction law was proposed for low shaking frequencies.

In Situ Pullout Resistance of Dynamically Driven Nails

AbstractExperimental results concerning the in situ pullout resistance of dynamically driven nails are presented. These results show that the actual pullout resistance is much higher than that predicted by the classical approach. A dimensional analysis approach is proposed to find a formula describing the actual performance of such nails.

Discussion of “Analysis of Extensible Reinforcement Subject to Oblique Pull” by J. T. Shahu and S. Hayashi

Shahu and Hayashi study the problem of failure of reinforced earth RE structures, including the mechanism of reinforcement’s pullout. They focus attention on a single strip/sheet that is pulled out from the mass of soil by the oblique force. Finally, the obtained results are applied to predict the critical height of RE walls. The approach presented by the authors leads to a few important questions.