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Direct simple shear (DSS) testing, despite its limitations, is one of the most common laboratory element tests in geotechnical engineering practice. The development and validation of a 300-mm diameter DSS device as well as test data generated for two materials with oversized particles, specifically pea gravel and municipal solid waste, are presented. The device has the capability to execute shear wave velocity measurements using both bender elements and accelerometers, as well as monotonic and cyclic testing under constant load or constant volume conditions. Validation testing using Ottawa sand C109 confirmed that the monotonic and cyclic constant volume response of the sand using the large-diameter device was similar to the results presented using conventional-sized DSS test devices. The shear wave velocity measurements using bender elements and accelerometers were found to be practically identical for the tested sand and pea gravel and were also consistent with data reported in the literature. The importance of axial (or vertical) displacement control during constant volume shearing is emphasized. It was found that tests that meet the ASTM D6528-07, Standard Test Method for Consolidated Undrained Direct Simple Shear Testing of Cohesive Soils, threshold of 0.05 % maximum axial strain during shearing may still result in different constant volume response, and it is recommended that (a) the threshold is changed to a maximum of 0.025 % and (b) the evolution of axial strain during constant volume shearing is always reported.

This paper describes a new type of torsional resonant column device that has a quasi-fixed base and free top. In this device, a relatively rigid torque transducer is placed between the bottom platen and the fixed chamber base. A large capacity torque motor excites the top platen. The primary measurements during the test are the rotation of the top platen, the torque at the specimen base and excitation frequency. An equilibrium equation for the bottom platen relates the torque transducer output to the torque applied by the specimen to the bottom platen. Using equivalent linear viscoelastic theory, a stiffness matrix is generated that relates the torque and rotation at each end of the specimen to specimen properties. A hybrid magnification factor is defined as the ratio of motion at the top of the specimen to that at the base. These two measurements provide the data needed to determine the shear modulus and damping ratio in the specimen for each frequency. The benefit of this approach is that the modulus and damping ratio of the soil are determined independent of the torque applied by the torque motor to the top platen. This removes the problems of torque motor characteristics, bearing friction, back EMF, and eddy current damping that occur with torque motors, which in turn allow more precise and repeatable determination of shear modulus and damping ratio over a wide range of shear strain and frequency. The paper outlines the theory, describes the apparatus and calibration procedures, and provides sample test data.

Recent advances in sensor and smart material technology can be used to provide real-time data for structural health monitoring of bridges. This paper describes a substructure instrumentation system that was installed at a selected pier of the new I-10 Twin Span Bridge over Lake Pontchartrain in Louisiana. The system was designed for both short-term and long-term health monitoring of the bridge. The monitoring system includes instrumenting eight piles with inclinometers and strain gages, and instrumenting the pile cap with corrosion meters, water pressure cells, tiltmeters and accelerometers. A lateral load test was designed and conducted to investigate the lateral behavior of the pier and to assess the validity of the analysis method used to design the batter pile foundations using the FB-MultiPier software. Two high strength steel strand tendons were used to impose about 1900 kips of lateral load. An automated survey station with prisms monitored the horizontal movements of the pier caps and bents. The strains and deformations within the foundation piles were measured using the inclinometers and strain gages. The results showed that the success rate of train gages and inclinometer sensors instrumentations were about 70%. A comparison of results from the lateral load tests with those from the FB-MultiPier software analyses showed that the software analyses had much higher conservative values compared to the measured values. These variations between measured and predicted values demonstrate the need to evaluate the applicability of the FB-MultiPier system for the design and analysis of batter pile group-cap systems. The soils’ p-y curves at different depths were also backcalculated from the derived soil reaction and lateral deformation profiles at different load increments.