Stanford Geothermal Program

Soil Stress Measurement: Part I. Transducer in a Uniform Stress Field

“…Only the stress normal to the vertical face is shown for the vertical transducer, whereas the stresses normal to all three faces of the stress state transducer are shown. The stresses normal to the vertical and lateral faces are predicted directly by the finite element program; the stress normal to the inclined face was calculated using Eqn (2). On the vertical faces, both transducers show predicted vertical stresses greater than the applied value.…”

“…5c). Figure 5c also shows the applied stresses calculated using the theoretical procedure described by Kirby 20 for an elasto-plastic soil and using Eqn (2) to calculate the applied stress in the inclined direction from the theoretical vertical and horizontal stresses. The over-and underestimates of stress with changing stiffness of the disturbed zone were less than in the linear elastic case (compare Figs 5c and 5a).…”

“…The theoretical lines in Fig. 6 show the applied stresses calculated using the theoretical procedure described by Kirby 20 for an elasto-plastic soil and using Eqn (2) to calculate the applied stress in the inclined direction. reduction in the lateral stresses and a slight reduction in the inclined stresses (Fig.…”

“…Once again, the theoretical lines in Fig. 7 show the applied stresses calculated using the theoretical procedure described by Kirby 20 for an elasto-plastic soil and using Eqn (2) to calculate the applied stress in the inclined direction. The increase in vertical stresses arose because a soil of greater shear strength can support greater shear stresses and thus there was less smearing out of stress concentrations.…”

“…Blunden et al, 1 Horn et al 2 and Kirby et al 3 report vertical stresses measured with small, disk-shaped transducers. These stress transducers are typically about 20 mm in diameter and 10 mm thick, with the measuring face on the flat, upper side.…”