Etude Expérimentale du comportement à la liquéfaction du Sol de Chlef

Abstract

The work performed in this thesis is related to a laboratory parametric study on the behaviour of a soil under monotonic loading. It includes four parts:

The first part includes a bibliographical analysis of the work dealing with the rheology of sands and the influence of the parameters on the liquefaction resistance of soils. We present the influence of the principal parameters on the resistance to liquefaction such as the grain size distribution, the stress history, the relative density, the presence of fines, saturation, the overconsolidation and the sample preparation methods.

The second part presents the equipment used, the procedure and the material used. The tests of repeatability were carried out to check the good performance of the equipment and the good control of the procedure.

The third part presents the results of the monotonic tests and discusses the influence of some parameters on the behaviour of the studied soils. The tests show that the increase in the initial confining pressure increases the resistance and the contractancy of the soil; the increase in the fines content affects significantly the volume change, and results initially in an amplification of the phase of contractancy. The tests show that the increase in the coefficient of Skempton B induces a reduction in the initial stiffness of the soil and the resistance (maximum deviator); and the phase of contractancy increases. The increase in the overconsolidation ratio OCR leads to an increase in the initial stiffness of the sand and its resistance (maximum deviator), and consequently a decrease in the pore water pressure.

The fourth chapter discusses the influence of the sample preparation method on the liquefaction resistance of the soil of Chlef. The tests prepared with the wet deposition method has a low resistance than those prepared with the dry deposition method. The residual strength of the samples prepared by the method of dry deposition increases in a linear way with the increase of the effective confining pressure and with the initial relative density. The residual strength for the samples prepared by the method of wet deposition increases when confining pressure increases from 100 to 200 kPa; for The confining pressure of 50 kPa and 200 kPa in the case of loose samples, the residual strength is almost zero.