Use of elastic stability analysis to explain the stress-dependent nature of soil strength

Abstract

The peak and critical state strengths of sands are linearly related to the stress level, just as the frictional resistance to sliding along an interface is related to the normal force. The analogy with frictional sliding has led to the use of a ‘friction angle’ to describe the relationship between strength and stress for soils. The term ‘friction angle’ implies that the underlying mechanism is frictional resistance at the particle contacts. However, experiments and discrete element simulations indicate that the material friction angle is not simply related to the friction angle at the particle contacts. Experiments and particle-scale simulations of model sands have also revealed the presence of strong force chains, aligned with the major principal stress. Buckling of these strong force chains has been proposed as an alternative to the frictional-sliding failure mechanism. Here, using an idealized abstraction of a strong force chain, the resistance is shown to be linearly proportional to the magnitude of the lateral forces supporting the force chain. Considering a triaxial stress state, and drawing an analogy between the lateral forces and the confining pressure in a triaxial test, a linear relationship between stress level and strength is seen to emerge from the failure-by-buckling hypothesis.

Silt türü bir Zeminin Gerilme Rahatlaması üzerine Deneysel bir Çalışma

“…Gerilme rahatlamasının özellikle ilk başladığı zamanlarda çok hızlı olduğu, gerilme değerlerindeki düşüşün önemli bir kısmın ilk dakika içerisinde gerçekleştiği ve tamamlanması için 40 dakikalık bir sürenin yeterli olduğu belirlenmiştir. Bu çalışmaya paralel olarak literatürdeki diğer ilgili çalışmalardan elde edilen bulgular da gerilme değerlerindeki düşüş hızının zaman ile azaldığı yönündedir (Bagheri et al, 2019;Augustesen et al, 2004;Tong and Yin, 2013 (Dijkstra et al, 2019;Komurlu and Kesimal, 2015;Hanley et al, 2015).…”

Stress Fluctuations in Triaxial Testing Of Angular Grains

“…There are some strong force chains as well as the weak ones. The alignment of the strong force chains are approximately parallel to the major principal stress direction, whereas the weaker chains are generally diagonal or orthogonal [2]. While the strong force chains dominate the mechanical behaviour of granular medium, the weak force chains usually contribute to the stability of strong ones [3].…”