STRESS FLUCTUATIONS FOR CONTINUOUSLY SHEARED GRANULAR-MATERIALS

Experiments on continuously sheared granular materials (glass spheres) with diameters 1.0 less than or equal to d less than or equal to 5 mm show large fluctuations in the normal stress, sigma(t). Experiments a re carried out in an annular Couette geometry for rotation rates 0.003 < theta < 1 rad/s. Power spectra from sigma(t), P(omega), show rate i nvariance in the fluctuations: theta P(omega) is a function only of om ega/theta, independent of theta. theta P(omega) depends relatively wea kly on d, The distributions of stresses rho(sigma) are similar to rece nt predictions for static arrays, but the width of rho(sigma) varies o nly weakly with d, suggesting stronger spatial correlation effects tha n expected from theory.