Centrifuge liquefaction tests in a laminar box

The difficulties associated with instrumenting earthquake sites in order to record pore pressure changes in a future event led to the use of scaled model tests performed in a centrifuge. Both dry and saturated sands were employed, contained in a box constructed of aluminium laminae designed to move freely on each other. This would result in shearing distortions developing in the soil unimpeded by the container. Accelerometers, displacement transducers and pore pressure sensors were attached to the box and embedded in the soil at various elevations so as to record the response of the soil to an earthquake-like excitation supplied to the base of the container. A special apparatus was constructed to imitate earthquake motion. In some tests on saturated sand, the soil profile was liquefied. Test results of accelerations, lateral and vertical displacements and pore pressures against time for typical earthquake inputs are given. The data, obtained under controlled conditions, can be compared with the various calculation methods for dynamically generated pore pressures

Analysis and Testing of the FBA-11 Force [Balance] Accelerometer

The FBA-11 is a feedback-controlled accelerometer widely used to measure and record accelerations arising from earthquakes. It has found application both for structural response and for ground motion studies. The design intent of the FBA-11 was to provide electronic control of the natural frequency, damping, and output voltage. Included in this paper are (1) a circuit analysis yielding the complete closed-loop transfer function, and (2) the corroborative test results from shake table evaluations. The transfer function can be used to correct recorded accelerations for instrument response

Identification of the dynamic properties of the OII landfill

The performance of landfills during strong earthquake shaking is a matter of considerable concern that deserves to be studied more extensively than it has been. The dynamic properties of the Operating Industries Inc. (OII) landfill materials have been investigated using strong-motion recordings, available field measurements, and simplified physical models. Although the earthquakes recorded at the OII landfill generated shear strains as large as 0.08%, the landfill material behaved essentially as a linear viscoelastic material with a negligible reduction in shear modulus with shear strain amplitude. The damping responsible for energy dissipation was found to depend on frequencies between 0.1 and 10 Hz. This frequency-dependent damping is presumed to result from scattering of waves on heterogeneities within the landfill and diffusion of interstitial fluids. The results of this study are useful for analyzing the dynamic response of landfills and cap systems during low-to-moderate sized earthquakes. The analysis is simplified because there were only two recording instruments on the OII landfill. It is recommended that more field instruments be deployed on this and other landfills to document their dynamic response during future earthquakes, and to develop large-scale laboratory tests to determine landfill material properties under large dynamic strains