Search

Plate load tests were carried out on un-reinforced sand and sand reinforced with fibres, compacted at relative densities (DR) of 30%, 50% and 90%. For the reinforced sand, 24 mm long polypropylene fibres were added, a concentration of 0.5% by dry weight. The analysis of the results indicates that the soil load-settlement behaviour is significantly influenced by the fibre inclusion, changing the kinematics of failure. The best performance was obtained for the densest (DR = 90%) fibre-sand mixture, where a significant change in the load-settlement behaviour was observed at very small (almost zero) displacements. However, for the loose to medium dense sand (DR = 30% and 50%), significant settlements (50 mm and 30 mm respectively) were required for the differences in the load-settlement responses to appear. The settlement required for this divergence to occur could best be represented using a logarithmic relationship between settlement and relative density. The overall behaviour seems to support the argument that inclusion of fibres increases strength of sandy soil by a mechanism that involves the partial suppression of dilation (and hence produces an increase in effective confining pressure, and a consequent increase in shear strength). [ABSTRACT FROM AUTHOR]

An effort is being carried out to develop dosage methodologies for improved soils based on a rational criterion, as in concrete technology, where the water/ cement ratio plays a fundamental role in target strength assessment. This study aims to assess the strength-controlling parameters of a sandy lean clay treated with lime or cement, and to show that the void/cementitious material content ratio plays a fundamental role in target strength assessment. The controlling parameters evaluated were the amount of cementitious material, the porosity, the moisture content, and the void/ cementitious material ratio. A number of unconfined compression tests and suction measurements were carried out in the present work. The results show that the unconfined compressive strength (UCS) increased linearly (with a reduced strength gain rate) with lime content for soil-lime mixtures. A power function fits the UCS-cement relationship better for soil-cement mixtures. The UCS increased linearly with the reduction in porosity for soil-lime mixtures and exponentially for soil-cement mixtures. Finally, the porosity/volumetric cementitious material content is shown to be a good parameter in the evaluation of the unconfined compressive strength of the soil studied. [ABSTRACT FROM AUTHOR]

The article presents an experimental investigation of the behaviour of artificially cemented soil cured under stress. It is indicated that the specimens cured at confining pressures of 50 kPa have larger normalised yield and state boundary surfaces. With regards to samples cured on the isotropic intrinsic compression line, a single state boundary surface is determined, independently of the shearing confining pressure. The effect of volume can be normalised when curing on the normal compression line. The extra strength imparted to the soil may attribute to the lower curing void ratio. The data indicate that the unloading events in the samples cured at higher stresses do not affect the subsequent behaviour.

A mathematical model is proposed to simulate isotropic compression test results obtained for specimens of silty sand mixed with different cement contents and cured at different void ratios. The ability of the model to represent the isotropic test results of specimens with different cement contents cured at high and low void ratios under high confining stresses was successfully checked. The physical meanings of the parameters established by the model were also evaluated. Finally, the applicability of the model to other artificially cemented soils was demonstrated. [ABSTRACT FROM AUTHOR]

The aim of this research was to study the behaviour of polypropylene-fibre-reinforced sand under large shear strains. The experimental study consisted of ring shear tests on a sand, with and without randomly distributed fibrous reinforcement. The behaviour of the fibre-reinforced sand mixtures was investigated at large distortional strains, examining the effects of fibre length, fibre content, effective normal stress, and relative density. The effects of reinforcement were found to be more pronounced for longer fibres, higher fibre contents and denser fibre-reinforced sand composites. The results showed the great potential of this kind of fibre reinforcement, because the increase of strength does not deteriorate even at very large strains. The fibres were exhumed after testing and it was found that they had both extended and broken at all normal stresses and for all initial fibre lengths studied, and that the fibre performance depended on the shear displacement that had occurred. [ABSTRACT FROM AUTHOR]

The article talks about the relationship of yielding, compressibility and strength in artificially cemented soil cured under stress. The experimental program is enumerated step-by-step, including the materials and testing procedures. More information on the subject matter is given and discussed in the article.

Saturated drained triaxial compression tests with local strain measurement were carried out to evaluate the effects of using three different randomly distributed fibres (polyester, polypropylene and glass fibres) and rapid hardening Portland cement to improve the engineering behaviour of a uniform fine sand. In addition to the nature of the fibres, also analysed have been the separate and combined effect of fibre content (up to 0.5% by weight), fibre length (up to 36 mm), cement content (from 0% to 7% by weight) and initial mean effective stress (20, 60 and 100 kN/m²) on the deformation and strength characteristics of the soil. The present work searches for the establishment of a relation between the properties of the fibres and the mechanical behaviour of the composite material, originated from their combination with soil and cement. The cementation itself notably increased modulus, peak cohesive intercept, peak friction angle and brittleness of the sand. Inclusion of polyester and glass fibres (both relatively stiff) slightly reduced the stiffness and increased the peak friction angle of both the cemented and uncemented sand, and also slightly reduced the peak cohesive intercept and brittleness of the cemented composite. On the other hand, relatively flexible polypropylene fibre reinforcement dramatically reduced the brittleness (changing the mode of failure of the cemented sand from brittle to ductile for longer fibres) and stiffness, while increasing the ultimate strength of the cemented composite. [ABSTRACT FROM AUTHOR]

The work simulates, in the laboratory, the formation of a cemented sedimentary deposit in which cement bonding occurs after burial and under geostatic stresses. Isotropic compression tests were carried out on artificially cemented specimens made with variable cement contents. After consolidating the samples to the uncemented normal compression line, the specimens were allowed to cure for 48 h before testing. The curing confining stresses ranged from 50 to 2000 kPa, and were intended to represent soil elements at different depths in the fictitious sedimentary deposit when the cementing occurred. The contribution of the cement bonds to soil compression and the changes in the isotropic yield stress as a function of void ratio and cement content were analysed. The results showed the importance of the void ratio during the formation of cement bonds and also of the degree of cementation for the compressive behaviour of the cemented soil, and demonstrated that the variation in yield stress with void ratio and cement content is dependent on the curing stress and independent of the stress history. [ABSTRACT FROM AUTHOR]

The article offers information on a study that the influence of lime content and porosity on the Mohr-Coulomb failure envelopes of lime-treated soils. Topics discussed includes pozzolanic reactions, application of methodology to a soil with different characteristics and shear resistance angle obtained by the triaxial tests.

This paper provides a theoretical derivation for the unconfined compression strength of artificially cemented granular soils. The proposed developments are based on the concept of superposition of failure strength contributions of the soil and cement phases. The granular matrix obeys the critical state soil mechanics concept, whereas the strength of the cemented phase can be described using the Drucker-Prager failure criterion. In the process, the analytical relation is suitably adjusted to parallel a recently proposed empirical relationship that links unconfined compression strength of artificially cemented granular soils to an adjusted porosity/cement ratio parameter. Although the proposed analytical relation fits the experimental data for different granular soils and cement curing time well, further parametric analysis offers the possibility of exploring the effect of some material parameters on the unconfined compression strength of artificially cemented granular soils. [ABSTRACT FROM AUTHOR]