Peak states

Figure 10.1 shows the states of soil samples at the same effective stress σ′ but at different voids ratios and overconsolidation ratios: at N the soil is normally consolidated, at W it is lightly overconsolidated or loose and the state is on the wet side of the critical state, and D₁ and D₂ are two states on the dry side where the soil is heavily overconsolidated or dense. For samples W and N on the wet side of critical the state parameter S _v (see Sec. 9.9) is positive and for samples D₁ and D₂ the state parameter is negative. Figure 10.2 shows the behaviour of these samples during drained shear tests and is similar to Fig. 9.1. At the critical states at C the samples have the same shear stress τ f ′ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315273549/cf413bf8-a32c-487e-8cc8-78a85381f509/content/inequ10_1.tif"/> , the same normal stress σ f ′ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315273549/cf413bf8-a32c-487e-8cc8-78a85381f509/content/inequ10_2.tif"/> and the same voids ratio e _f, but at the peak states the shear stresses and voids ratios are different. The idealized behaviour described in this chapter is based on experimental data given by Atkinson and Bransby (1978) and by Muir Wood (1991).