Triaxial Cyclic Loading Research Articles

Hysteretic behavior of soft clays weakened in the process of dynamic loading

The authors derived a new weakening relationship for more accurate description of the deformation behavior of water-saturated soft clays with triaxial cyclic loading, which includes three weakening indices. This article gives some applications of the derived relationship.

Behaviour of clayey sands under undrained cyclic triaxial loading

Behaviour of clayey sands under undrained cyclic triaxial loading

Behaviour of clayey sands under undrained cyclic triaxial loading

The response of two clayey sands to undrained cyclic triaxial loading is described. Both the stress history and the cyclic stress level have been varied. The behaviour is compared with that observed for the clayey sands tested under monotonic loading. Effective stress paths for the normally consolidated soils loaded monotonically in triaxial compression and extension are shown to form a hounding envelope which determines the pattern of behaviour under cyclic loading. A threshold strain is identified, below which cyclic straining results in stable behaviour. Above the threshold strain, pore pressures and strains accumulate under cyclic loading at a rate that increases as the effective stress state approaches the bounding envelope. On reaching the bounding envelope in triaxial compression, the clayey sands strain-soften. On reaching the bounding envelope in triaxial extension, there is liquefaction. L'article décrit la réponse de deux sables argileux au chargement triaxial cyclique non-drainé On a fait varié I'histoire des contraintes et le niveau de contrainte cyclique. Le comportement des sables fut cornparé avec celui observb dans le cas de sables argileux testés sous chargement monotone. On démontre que les chemins de contraintes effectives pour les sols nomalement consolidés et chargés de façon monotone en compression et en extension triaxiales forment une enveloppe limite qui determine le type de comportement sous chargement cyclique. Une contrainte de seuil fut identifike au-dessous de laquelle le comportement stable malgré les contraintes cycliques. Au-dessus de la contrainte de seuil les pressions interstitielles et les contraintes s'accumulent sous chargement cyclique à une vitesse qui s'augmente au fur et à mesure que l'état de contrainte effective s'approche de l'enveloppe limite. Lorsqu’ils atteignent I'enveloppe limite en compression triaxiale les sables argileux se ramollisent. La liqukfaction a lieu lorsque I'enveloppe limite est atteinte en extension triaxiale.

Residual Strains in Calcareous Sand due to Irregular Cyclic Loading

This paper describes a procedure for predicting the residual strains developed in calcareous sand under irregular cyclic triaxial loading conditions. The rates of accumulation of volumetric and shear strains are treated separately, with the volumetric strain response being used as the basis for characterizing the effects of cyclic loading. The residual volumetric strain developed as a result of repeated loading is related to the mean and the amplitude of the cyclic deviator stress. Thus, by using empirical correlations between the applied deviator stresses, the number of cycles, and the measured residual strains, the effect of cyclic loading under one set of cyclic loading conditions can be expressed in terms of an equivalent number of cycles under a different set of cyclic loading conditions. By using this equivalent number of cycles for the cyclic loading stresses, the residual strains developed as a result of further loading are then determined, so that the residual strains developed at any stage during irregular cyclic loading can be evaluated.

Jointing at rock contacts in cyclic loading

Joint often play a critical role in localizing economic deposits of petroleum and groundwater. A knowledge of reservoir fracturing can optimize resource development and increase fluid recovery. Such reservoir units are frequently found in regions with nearly flat-lying, unfaulted strata. In these areas the ability to predict vertically extensive joint sets using surface mapping can provide the competitive edge in exploration and production. It is commonly assumed that surface joints are related to joints at depth, yet until now there has been no widely accepted mechanism explaining when and how joints propagate vertically. Cyclic loading resulting from earth tides or recurring seismic shocks may provide that mechanism. The objective of this work is to determine the effect of a pre-existing joint on initiation and propagation of cracks across lithologic contacts in cyclic loading. Pikes Peak granite and Dakota sandstone were tested in uniaxial tension and compression, triaxial compression, and triaxial cyclic compression-tension. Both monolithologic and sanstone-granite composite samples were tested. Composite samples were meant to simulate the basement-sediment contact in underformed rock. Two basic configurations were examined: that representing lateral (horizontal) loading, and that representing vertical loading. The granite was saw cut to approximate pre-existing joints. Uniaxial tests provided information on elastic properties of the two rock types and the relative strength of various configurations. Triaxial tests were used to simulate lateral and vertical loading conditions under 308m (1000 ft) of overburden. Triaxial cyclic fatigue tests were used to examine the geometry of joints induced under lateral and vertical cyclic loading, the amount of weakening possible, the relative importance of compression vs tension in cyclic loading, and the relation of induced fractures to pre-existing joints. The results of these tests were compared to observations made at outcrops of basement-sandstone contacts. Given the opportunity, rock will fall in tension before it fails in compression. Rock fails by alternting lateral and axial extension in cyclic triaxial loading. Extension failure occured at as little 24% of the triaxial compressive strength during about 80 cycles. Most outcrop joints do not cross contacts, indicating that the discontinuity is a barrier to the passage of stress concentrations. The most probable cause of near-vertical joints that do cross contacts without displacement is lateral extension. Pre-existing cracks concentrate tensile stress at the contact and initiate growth of a joint from that point.

Dynamic properties of cohesionless soils under cyclic triaxial loading conditions : Vinson, T S; Czajkowski, R L; Li, J C Michigan State Univ, Division of Engineering Research report MSU-CE-77-1, Jan 1977, 281P

Dynamic properties of cohesionless soils under cyclic triaxial loading conditions : Vinson, T S; Czajkowski, R L; Li, J C Michigan State Univ, Division of Engineering Research report MSU-CE-77-1, Jan 1977, 281P

Dynamic properties of ice and frozen clay under cyclic triaxial loading conditions : Vinson, T S; Chaichanavong, T Michigan State Univ, Division of Engineering Research report MSU-CE-76-4, Oct 1976, 288P

Dynamic properties of ice and frozen clay under cyclic triaxial loading conditions : Vinson, T S; Chaichanavong, T Michigan State Univ, Division of Engineering Research report MSU-CE-76-4, Oct 1976, 288P

Dynamic properties of ice and frozen clay under cyclic triaxial loading conditions : Chaichanavong, T Ph D thesis, Michigan State Univ, 1976

Dynamic properties of ice and frozen clay under cyclic triaxial loading conditions : Chaichanavong, T Ph D thesis, Michigan State Univ, 1976