The Class 1933 Cyclic Soils Laboratory

The cyclic soils laboratory has conducted significant research for more than 15 years in the areas of earthquake engineering and soil dynamics. It is directed by Dr. Thomas F. Zimmie.

A closed loop servo-hydrulic axial-torsional loading system with a 5,500lb. axial acuator and a 1,000 in.-lb. torsional actuator, can perform tests in both axial and torsional modes, alone or combined, in phase or at an arbirary phase angle. The soil specimens are placed inside specially desinged triaxial cells. Either mode can be applied to the soil monotonically or cyclically, in stress or strain control. Also, in either mode the load or displacement can be held constant while the loading is varied in the other mode. Modern, dedicated computerized data acquisition and control capablities are used.

The system has been applied to study the cyclic undrained behavior of saturated sand, liquefaction and flow failure during earthquakes, and constitutive relations for cohesionless soil. Recent projects have included the re-evaluation of the flow slide in one of the slopes of the Lower San Fernando Dam in California during the 1971 earthquake, the development of a new method to predict permanent ground deformations due to earthquakes, and a study of yield surfaces in dry sand during cyclic loading. In the geoEnivironmental area, the centrifuge has been used to simulate the long term behavior of landfill liners and covers and to measure dynamic interface friction angles of geosynthetics used in landfills.

A Norwegian Geotechnical Institute direct simple shear device has been modified by integrating it with the servo-hydraulic closed loop system mentioned above. This allows it to perform stress or strain controlled cyclic tests in a variety of wave forms. It has been used to study the response of marine clays and silts during earthquake and sea wave loading.

Recent additons to the laboratory include the geotechnical centrifuge (described below); a resonant column device for measurement of wave velocity/modulus and internal damping of the soil; a number of personal computers, computer terminal, workstations, and peripherals located in a newly renovated computer room; and in situ shaking equipment.

The in situ equipment is used to measure the vibration characteristics of full scale soil and soil-structure systems in the field, such as earth and reinforced-earth walls, dams, bridges, etc. This is used to evaluate the response of those civil engineering facilities when subjected to earthquake loading. Nondestructive tests are conducted using either impact with a specially calibrated hammer, or steady-state vibration with a 5,000lb.force harmonic exciter recently designed and constructed at Rensselaer. Eight channels of high-speed data acquisition are availble.