Triaxial Stress Path Research Articles

A mathematical model for soils

Two mathematical models developed previously by Lade for the stress, strain, and strength behaviour of soils are combined in this paper. The first model, which has only an open ended conical yield surface, is modified by adding a cap yield surface. With this addition, the predictions for soil behavior in laboratory experiments are improved along the stress paths remaining within the current conical yield surface. The capabilities of the present version of the model are evaluated by comparing the calculated and measured response of soil in proportional loading, isotropic compression, and reloading in a triaxial stress path. The differences between the two versions of the work hardening model with and without a cap are illustrated.

Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay

Abstract Soil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works. To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent in situ conditions before and during construction. The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.

Stress Path Tests on 100 mm Diameter Samples

Abstract The use of stress path tests is discussed in relation to geotechnical design, and a description is given of the triaxial test stress path apparatus developed at The City University. Test results are presented from a series of triaxial tests following stress paths commonly encountered in engineering design problems. These are compared with the results of conventional triaxial tests. The stress-strain behaviour and pore pressure response of soil are shown to be very much dependent on the stress path followed, and the advantages of using stress-controlled loading in triaxial tests is demonstrated.

Settlement of Spread Footings on Sand

Settlement measurements for a large number of footings supported on dune sand are compared to settlement predictions based on standard penetration tests, plate load tests, oedometer tests and triaxial stress path tests. The sand considered in this study has been preloaded by dunes or compacted by vibratory rollers. Good agreement between measurement and prediction is obtained using the procedure suggested by Meyerhof, a modification of the Terzaghi and Peck method, provided that the blow-count is corrected for overburden pressure. Good agreement is also obtained with oedometer and stress path test predictions. Predictions based on plate load tests underestimated measured settlements whereas the conventional correlations between settlement and standard penetration test resistance overestimated measured settlements.

Stress-Strain Relations For Clays: An Energy Theory

Synopsis A theory for the internal energy of clay/water systems is derived. In this theory the observed critical state property is central. Only when the relation between mean compressive stress and void ratio is the same as that in the critical state is there a balance between interparticle forces and external forces. This concept leads to a description of internal energy changes in triaxial tests; if this is combined with a description of plastic dissipation, an energy balance can be written. Comparison with experiments on kaolin shows a simple pattern in the behaviour of the parameter describing dissipation. A stress-strain relation for any triaxial stress path can now be derived. A final section of the Paper explores the consequences of linking this with the normality concept of plasticity theory. Une théorie est dérivée pour l'érgie interne des systémes argile/eau. Dans cette théorie la qualité de l'état critique observeé; est centrale. Seulement dans les cas où le rapport entre la contrainte de compression moyenne et l'indice de vide est le même que celui de l'état critique se trouve un e´quilibre entre les forces entre les particules et les forces extérieures. Ce concept méne à une description des changements d'énergie interne dans les essais triaxiaux; si ceci comporte aussi une description de dissipation plastique un equilibre d'é;nergie peut être posé. La comparaison avec des expériences sur le kaolin fait ressortir une forme simple dans le comportement du paramétre décrivant la dissipation. Un rapport contrainte-déformation pour toute trajectoire de contrainte triaxiale peut maintenant être déduit. Une section finale de l'exposeé examine les conséquences d'établir un lien entre ceci et le concept de l'état normal de la théorie de plasticité.