The general and congruent effects of structure in natural soils and weak rocks
TL;DR: In this article, the engineering properties of naturally occurring sedimentary and residual deposits which are usually treated in geotechnical engineering as ‘soils’ are reviewed, and it is shown that usually they have characteristics due to bonded structure which are similar to those of porous weak rock.
Abstract: The engineering properties of naturally occurring sedimentary and residual deposits which are usually treated in geotechnical engineering as ‘soils’ are reviewed, and it is shown that usually they have characteristics due to bonded structure which are similar to those of porous weak rock. While this structure can arise from many causes, its effects follow a simple general pattern that involves stiff behaviour followed by yield. This yield can be described in a similar way to that occurring due to overconsolidation, although it is a separate phenomenon. The effects of structure are as important in determining engineering behaviour as are the effects of initial porosity and stress-history, which are the basic concepts of soil mechanics. As it can be described in a general way, it is concluded that structure and its effects should be treated as a further basic concept of equal importance. L'article passe en revue les proprietes des depots sedimentaires et residuels naturels qui sont nor-malement traites comm...
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TL;DR: In this paper, the relationship between the microstructure and engineering properties of cement-treated marine clay was examined using x-ray diffraction, scanning electron microscopy, pH measurement, mercury intrusion porosimetry, and laser diffractometric measurement of the particle size distribution.
Abstract: This paper examines the relationship between the microstructure and engineering properties of cement-treated marine clay. The microstructure was investigated using x-ray diffraction, scanning electron microscopy, pH measurement, mercury intrusion porosimetry, and laser diffractometric measurement of the particle size distribution. The engineering properties that were measured include the water content, void ratio, Atterberg limit, permeability, and unconfined compressive strength. The results indicate that the multitude of changes in the properties and behavior of cement-treated marine clay can be explained by interaction of four underlying microstructural mechanisms. These mechanisms are the production of hydrated lime by the hydration reaction which causes flocculation of the illite clay particles, preferential attack of the calcium ions on kaolinite rather than on illite in the pozzolanic reaction, surface deposition and shallow infilling by cementitious products on clay clusters, as well as the presence of water trapped within the clay clusters.
451 citations
TL;DR: In this article, an anisotropic elastoplastic model for soft clays is presented, based on multistage drained triaxial stress path tests on Otaniemi clay from Finland provided support for the proposed shape of the yield curve and for the relationship describing the change of yield curve inclination with plastic straining.
Abstract: An anisotropic elastoplastic model for soft clays is presented. Experimental data from multistage drained triaxial stress path tests on Otaniemi clay from Finland provide support for the proposed shape of the yield curve and for the proposed relationship describing the change of yield curve inclination with plastic straining. Procedures are proposed for determining the initial inclination of the yield curve and the values of the two additional soil constants within the model. Comparisons of model simulations with experimental data demonstrate significant improvements in the performance of the new model over the Modified Cam Clay model. The remaining discrepancies are mainly attributable to the important role of destructuration in the sensitive Otaniemi clay
401 citations
TL;DR: In this article, the authors review the state of knowledge in this domain, examining the basic aspects of soil mechanics that are relevant to the context of slopes, the importance of water on slope behaviour, and then the different stages of slope movements: pre-failure, failure, postfailure and reactivation.
Abstract: Movements and failure of cuts and natural slopes constitute an important geotechnical problem that involves a variety of geomaterials in a variety of geological and climatic contexts, and which has a major socio-economic impact in many countries. The paper reviews the state of knowledge in this domain, examining the basic aspects of soil mechanics that are relevant to the context of slopes, the importance of water on slope behaviour, and then the different stages of slope movements: pre-failure, failure, post-failure and reactivation. Finally it is shown how the geotechnical characterisation of slope movements can be used, in particular for assessing risk associated with such movements. Emphasis is put on for the brittleness of soils and its practical implications for the progressive failure developing at the pre-failure stage and on the characteristics of post-failure movements. The influence of other factors such as creep, fatigue, destructuration, partial saturation and infiltration is also considered.
359 citations
TL;DR: In this paper, the effect of randomly distributed fiber reinforcement and cement inclusion on the response of a sandy soil to load was evaluated and it was shown that the fiber reinforcement increases both he peak and residual triaxial strength, decreases stiffness, and changes the cemented soils brittle behavior to a more ductile one.
Abstract: Triaxial compression tests were carried out to evaluate the effect of randomly distributed fiber reinforcement and cement inclusion on the response of a sandy soil to load. Cemented specimens were prepared with cement contents of 0% and 1% by weight of dry soil and cured for seven days. Fiber length was of 12.8 mm, in the contents of 0% and 3% by weight of dry soil-cement mixture. Test results indicated that the addition of cement to soil increases stiffness, brittleness, and peak strength. The fiber reinforcement increases both he peak and residual triaxial strength, decreases stiffness, and changes the cemented soils’ brittle behavior to a more ductile one. The triaxial peak strength increase due to fiber inclusion is more effective for uncemented soil. However, the increase in residual strength is more efficacious when fiber is added to cemented soil. Peak strength envelopes indicate that the friction angle is increased from 35° to 46° as a result of fiber inclusion. The cohesion intercept is affected slightly by fiber addition, being basically a function of cementation.
351 citations
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TL;DR: In this paper, Hvorslev's equation for the shear strength of clay is shown to define a surface in a space of three variables σ, e and τ. The progressive yielding of a sample defines a loading path in this space, and the paths taken by samples in differing tests can be correlated if a boundary energy correction is applied.
Abstract: Synopsis Hvorslev's equation for the shear strength of clay is shown to define a surface in a space of three variables σ′, e and τ. The progressive yielding of a sample defines a loading path in this space, and the paths taken by samples in differing tests can be correlated if a boundary energy correction is applied. The final portions of all paths then lie in a unique surface, and the paths end at a unique critical voids ratio line. At the critical voids ratio state unlimited deformation can take place while σ′, e and τ remain constant. The two concepts of the existence of such a surface and such a critical voids ratio line are verified by an analysis of results of triaxial tests on a clay. Similar tests on silt and sand also confirm the concepts, although some inaccuracy is inherent in these tests. Finally results of tests on granular media in a simple shear apparatus are presented which confirm closely the applicability of both concepts to the yielding of granular media. On montre que l'equation de Hvo...
1,240 citations
TL;DR: In this paper, four types of oedometer tests (constant rate of strain tests, controlled gradient tests, multiple-stage loading tests and creep tests) were carried out on a variety of Champlain sea clays.
Abstract: Four types of oedometer tests (constant rate of strain tests, controlled gradient tests, multiple-stage loading tests and creep tests) were carried out on a variety of Champlain sea clays. Results obtained on five sites are used to demonstrate that the rheological behaviour of these clays is controlled by a unique stress-strain-strain rate relationship. This relationship can be simply described by two curves (σ-p′-ɛv and (σ′/σp′)-ɛv). The significance, the practical implications and the limitations of the model are also discussed. Quatre types d'essais oedometriques (a vitesse constante de deformation, a gradient controle, a chargement en plusieurs etapes et avec fluage) ont ete effectues sur diverses argiles marines Champlain. Les resultats obtenus sur cinq sites sont utilises pour demontrer que le comportement rheologique de ces argiles est regi par une relation unique contrainte-deformation/vitesse de deformation. Cette relation peut etre decrite de facon tres simple par deux courbes (σp-ɛv et (σv′/σp′...
493 citations
TL;DR: In this paper, a test program was undertaken to define the nature of the cementation and its effect on behavior of the soils, and a total of 137 laboratory compression and tension load tests were performed on undisturbed samples of naturally and artificially prepared cemented sands.
Abstract: Cemented sands are found in many areas of the world; one of their distinguishing characteristics is their ability to stand in steep natural slopes. Large deposits are located along the California coast, and in a number of areas intense urban development has occurred near the crest of high, steep slopes. Because of the hazards posed by slope failures in the cemented sands, a test program was undertaken to define the nature of the cementation and its effect on behavior of the soils. A total of 137 laboratory compression and tension load tests were performed on undisturbed samples of naturally cemented sands and artificially prepared cemented sands. The materials exhibited friction angles similar to uncemented sands, but had a cementation strength intercept and a tensile strength. The primary cementing agents of the sands tested were silicates and iron oxides. The strength of the cemented sands were found to be a function of density, amount of cementing agent, grain shape and grain arrangement.
441 citations
TL;DR: In this paper, the authors show how field measurements of displacement around foundations and excavations combined with numerical analysis and recent developments in laboratory techniques can be used to estimate the displacement of foundations.
Abstract: The purpose of this lecture is to show how field measurements of displacement around foundations and excavations combined with numerical analysis and recent developments in laboratory techniques ha...
423 citations