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doi:10.2204/iodp.proc.308.210.2009

Experimental results

All specimen locations, depths, and corresponding triaxial experiments are provided in Table T1. Table T2 summarizes the consolidation phase of each experiment, and Table T3 provides information on the shear phase of each experiment. Complete experimental data are provided in “Supplementary material.”

Consolidation results

We describe the initial conditions and consolidation parameters for each specimen (Table T2). The specimen data define the initial conditions of the specimen including w_n, total density (ρ_t), e_i, and S_i. Specimen water contents ranged from 28% to 50%, and initial void ratios ranged from 0.84 to 1.4. G_s was assumed to be 2.78. Initial consolidation conditions define the specimen and cell conditions prior to the start of K_o consolidation. σ_i′ is the initial vertical effective stress applied to the specimen and ε_a is the axial strain after this initial stress is applied. u_b is the backpressure applied to the specimen. ε_vol is the total volume strain to the specimen during backpressure saturation. B is the pore pressure parameter (B = Δu/Δσ_r).

The consolidation results portion of the table describes the parameters of the K_o consolidation. The strain rate (ε_a/h) defines the constant rate of axial strain maintained during consolidation. Strain rates for each experiment were constant but varied from 0.05%/h to 0.23%/h between experiments (Table T2). The specimen conditions at maximum stress define the conditions at the end of primary K_o consolidation. These include ε_a, ε_vol, maximum effective vertical stress (σ_vm′), and lateral stress ratio (K_c) at σ_vm′. The time allowed for secondary compression after reaching σ_vm′ is t_s. The final parameters define the conditions at the end of secondary compression including σ_vc′ and overconsolidation ratio (OCR). All experiments were controlled to have an OCR = 1 such that σ_vc′ was the greatest effective stress to which the specimen was exposed. Prior to initial shearing, the consolidation stress ratio (K_c) for the specimens ranged from 0.50 to 0.73 (Fig. F2).

Standard results from the K_o-consolidation phase include the stress-strain behavior, total work done to the specimen, and the lateral stress ratio (Fig. F3). From the stress-strain data, basin model inputs can be constrained and compression behavior can be defined as is done for constant-rate-of-strain consolidation experiments (e.g., Long et al.). The total work data can be used to infer preconsolidation stress for each specimen (Long et al.; Becker et al., 1987). Work is calculated as

.

Example K_o-consolidation phase data are provided in Table T5. Complete K_o-consolidation phase data are provided as plots and tables in the CONSOL folder in “Supplementary material.”

Strength results

The shear phase conditions and results are provided in Table T3. The specimen data are identical to those in the consolidation phase (Table T2). The shear phase conditions provided in Table T3 define the strain rate for shearing (ε_a/h) and the stress conditions (K_c, σ_vc′, and OCR) prior to shearing. The next section of the table provides the strength results at maximum shear and obliquity (Table T3). Obliquity refers to the ratio of the normalized shear stress (q) to the normalized mean effective stress (p′). The normalized undrained strength ranges from 0.21 to 0.36, whereas the friction angle ranges from 17° to 29° at maximum shear (Fig. F2; Table T3). Both properties show a relation to the vertical consolidation stress prior to shearing.

Example data from the shear phase are shown in Figure F4 and Table T6. The summary plots include normalized shear stress (q/σ_vc′) versus ε_a, internal friction angle (ϕ) versus ε_a, normalized excess pore pressure (Δu_e/σ_vc′) and normalized shear-induced pore pressure (Δu_s/σ_vc′) versus ε_a, and normalized stress path (q/σ_vc′ versus p′/σ_vc′) for each test. The following equations define p′, q, ϕ, secant modulus (E), and pore pressure parameter (A), which are key parameters in the shear-phase results. All variables are defined in Table T4.

Complete data from the undrained shearing portions of the triaxial tests are in the SHEAR folder in “Supplementary material.”

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