James A. Bay

Terrestrial-LIDAR Visualization of Surface and Structural Deformations of the 2004 Niigata Ken Chuetsu, Japan, Earthquake

Following the 23 October 2004 Niigata Ken Chuetsu, Japan, Mw 6.6 earthquake, LIDAR (light detection and ranging) technology was used to create ultra high-resolution three-dimensional digital terrain models of the earthquake damage. Two reconnaissance teams traveled with tripod-mounted LIDAR that allowed for the rapid collection of post-earthquake failure geometries of ground, structures, and lifelines prior to modification by post-disaster recovery efforts and natural processes, with range accuracies of approximately 2.5 cm and targets illuminated up to 400–700 m from the sensor. LIDAR offers several benefits: (1) detailed failure morphologies of damaged ground and structures, measured remotely and in a way not feasible by conventional means; (2) exploration and visualization of damage on a computer screen is enabled, in orientations and scales that were previously impossible, providing better definition of the failure surfaces, deformation patterns, and morphologies required for understanding failure modes; and (3) archived ultra-high-resolution data for evaluation of analytical and numerical models of deformation. High-resolution images and movies of LIDAR data can be viewed at http://walrus.wr.usgs.gov/geotech/Niigata/ and the online pages of Earthquake Spectra.

Engineering Analysis of Ground Motion Records from the 2001 Mw 8.4 Southern Peru Earthquake

The Mw 8.4 23 June 2001 Southern Peru earthquake generated intense ground motions in a large region encompassing southern Peru and northern Chile. The earthquake was recorded by seven strong motion stations with peak ground accelerations ranging from 0.04 g to 0.34 g for site-to-fault distances ranging from about 70 km to 220 km. At this time, there are no other strong motion records for an earthquake of this magnitude. Hence, the strong motion data set from this earthquake is unique and of particular interest to engineers dealing with seismic design in subduction regions. This paper presents an engineering analysis of the strong motion records. Shear-wave velocity profiles were measured using Spectral Analysis of Surface Waves methods at four stations. Measured shear-wave velocities are high, indicating that all sites classify as stiff soil sites (Site C) according to the International Building Code classification scheme. The strong motion set is characterized by strong high frequency content at large distances from the fault. Site response contributed at least in part to the observed high frequency content in the ground motions. In general, current attenuation relationships for spectral acceleration underpredicted the observed ground motions.

Super-Accelerated Testing of Flexible Pavement with Stationary Dynamic Deflectometer

The Texas Department of Transportation (TxDOT), in partnership with the Center for Transportation Research, has implemented the Texas mobile load simulator (TxMLS) as a tool for accelerated testing of in-service pavements. Although the TxMLS has been used successfully to test in-service pavements in the Yoakum and Fort Worth districts, the fact that only one TxMLS machine exists limits the number of accelerated pavement tests (APT) that can be performed. Therefore, TxDOT is evaluating a modification of the rolling dynamic deflectometer (RDD) for use as a super-accelerated pavement tester. In this application, the truck-mounted dynamic loading system is operated in a stationary mode, with the loading rollers and rolling sensors of the RDD removed from operation. The servohydraulic actuator is used for application of harmonic loading to a wheel footprint on the pavement surface. Hundreds of thousands of load repetitions are applied in a matter of hours; hence the designation as super-accelerated testing. This stationary dynamic deflectometer (SDD) is being studied as a possible tool for use in expanding TxDOT’s APT program. The SDD may allow TxDOT to increase, in a cost-effective manner, the number of accelerated tests that can be performed. Preliminary tests have been performed with the TxMLS and SDD on two different pavement recycling strategies constructed on the northbound and southbound lanes of US-281 in the Fort Worth District. That the same conclusion was reached about the relative performance of the test sections with both machines indicates the potential usefulness of the SDD.

Profiling flexible highway pavement continuously with rolling dynamic deflectometer and at discrete points with falling weight deflectometer

Nondestructive testing of pavements plays an important role in the management of pavement infrastructure. Nondestructive testing techniques have been widely utilized in the United States during the past decade to characterize pavement systems at discrete points. Discrete-point testing is, however, not feasible for routine use as a means of continuously characterizing pavement systems. A new nondestructive testing technique for continuously profiling pavements has been developed, namely, the rolling dynamic deflectometer (RDD). The RDD is a large truck on which a servohydraulic vibrator is mounted. The vibrator is used to apply large vertical dynamic loads to the pavement with loading rollers, and the induced dynamic displacements are measured at multiple locations with rolling sensors. This arrangement permits continuous measurements at multiple locations on the pavement surface in a fraction of the time required for typical discrete-point testing at a few points along the section. In this paper, the configuration of the RDD and the procedure used to analyze RDD data are discussed. Continuous deflection profiles are presented from a test section of a flexible Interstate highway pavement, which contains several distinctly different pavement structures. The effects of the structures on measured deflections are discussed, and the capability of the RDD to delineate the extent of each feature is presented. The importance of loading frequency and resonances in the pavement structure is shown. In addition, results from the RDD are compared with results from falling weight deflectometer (FWD) tests performed at the same locations.

EVALUATING RUNWAY PAVEMENTS AT SEATTLE-TACOMA INTERNATIONAL AIRPORT: CONTINUOUS DEFLECTION PROFILES MEASURED WITH THE ROLLING DYNAMIC DEFLECTOMETER

The rolling dynamic deflectometer (RDD) is a relatively new tool for assessing the condition of pavements. Continuous deflection profiles, rather than deflections at discrete points, are measured with the RDD. The results of RDD tests on two runways at the Seattle-Tacoma International Airport (Sea-Tac) are presented. These results illustrate how continuous deflection profiles can be used to assess the condition of pavements without the use of backcalculation. Continuous deflection profiles allow sections of pavement exhibiting large or anomalous deflections to be quickly and easily identified. The extent to which pavements are damaged and degraded can be determined by comparison of the deflections of intact, lightly trafficked pavements with the deflections of the pavements in question. The condition and load transfer capacity of all transverse joints and cracks in rigid pavements can be determined by observation of the measured deflections as the RDD approaches and crosses each joint or crack. The RDD is a valuable tool for rapidly identifying regions of pavement requiring rehabilitation. Critical regions of pavement identified with the RDD for possible rehabilitation can be studied further with use of traditional discrete testing methods. These capabilities make the RDD a valuable tool in airfield pavement management.

Design and Performance of an Electro-Pneumatic Pile Hammer for Laboratory Applications

Small piles used in research programs have generally been installed by pushing or driving using slow mechanical drop hammers, because of the expense and technical difficulties associated with manufacture of realistic small-scale pile driving hammers. However, pushing does not model inertial effects and slow driving does not model diffusive effects in the soil. It remains to be demonstrated whether these effects are important or not. To help clarify this issue, an electronically controlled, single-acting air hammer, with a rated energy of 211 J (156 ft · lb), and an operating frequency of up to 1.2 Hz, was designed and built. The hammer was used successfully to drive 90 mm (3.5 in.) diameter piles into dense sand under a confining pressure of 138 kPa (20 psi). The behavior of the hammer was documented using detailed measurements of time-dependent ram movements, accelerations, and chamber pressures. This paper is concerned with the design and performance of the hammer.

CONTINUOUS PROFILING OF RUNWAY AND TAXIWAY PAVEMENTS WITH ROLLING DYNAMIC DEFLECTOMETER AT DALLAS-FORT WORTH INTERNATIONAL AIRPORT

The rolling dynamic deflectometer (RDD) is powerful tool for use in managing airport pavements. With the RDD, continuous deflection profiles of runways and taxiways can be efficiently and effectively measured. These continuous profiles, both in the longitudinal and transverse directions, provide valuable information about the condition of the pavement system. The profiles are especially valuable because the entire pavement is tested and characterized rather than approximating the system with a limited number of discrete measurements to represent the entire pavement. The capabilities of the RDD were demonstrated by testing pavements at Dallas–Fort Worth International Airport. One existing runway, one existing taxiway, and a newly constructed (but not yet opened) runway were tested. The conditions of the different intact pavement sections and the various pavement joints are readily shown in the measured deflection profiles. In most cases, heavily trafficked pavement sections showed higher deflections than comparable sections with lower traffic, with the lowest deflections measured on the newly constructed runway. However, one recently constructed runway extension showed unusually high deflections, especially at the joints. The taxiway that was tested generally exhibited lower deflections than the operating runway. In the cases of the in-service pavements, transverse profiles clearly showed the softening of the highly trafficked central portion of the pavement.

Calibration of Equipment Damping in a Resonant Column and Torsional Shear Testing Device

In a coil-magnet drive system of the resonant column (RC) and torsional shear (TS) apparatus, a back electromotive force (back emf) affects the measurement of stiffness and damping in soils. An empirical approach has been used to account for this problem; however, this approach is only applicable for a narrow range of conditions. This study focused on developing a method dealing with the back emf effect more precisely. The method proposed in this study is the use of an electromagnetic model to describe the back emf effect. This approach simplifies the problem by modeling the back emf in terms of an equipment spring constant (keq) and an equipment viscous damping coefficient (ceq). The electromagnetic model consists of four parameters. The method used to measure the model parameters and model verification is presented in this paper. The back emf effect on RC and TS tests can then be predicted. In addition, this study verifies that the equipment generated damping for the TS test is negligible.

Calibrating Vertical Deformations in a Finite Element Model of an MSE Wall

This paper presents a portion of an extensive model calibration for a finite element analysis of a mechanically stabilized earth wall located along the I-15 reconstruction project through Salt Lake City, Utah. The 9.1 m wall was constructed on a soft clay foundation, and instrumentation was placed in this material to monitor foundation response. Vertical movement at the base of the wall was 0.5 m at the end of primary consolidation, and vertical deformations were obtained throughout the soil profile. These readings provided the data used to calibrate a finite element model of the MSE wall using Plaxis software.

Analysis of Strain Sensor Cable Models and Effective Deployments for Distributed Fiber Optical Geotechnical Monitoring System

Long range, distributed fiber optic sensing systems have been an available tool for more than a decade to monitor pipeline subsidence integrity challenges. Effective deployment scenarios are an important decision to be factored into the selection of this monitoring equipment and typologies relative to specific project needs. In an effort to analyze the effectiveness of various fiber optic deployment conditions, a controlled field experiment was conducted. Within this field experiment, a variety of distributed fiber optic sensors and point sensors were deployed in predefined positions. These positions relative to the pipeline were selected to support a range of deployment needs including new construction or retrofitting of existing pipelines. A 16-inch diameter by 60-meter long epoxy coated pipeline that was capable of being pressurized to mimic operating conditions was utilized. This test pipe was installed in a typical trench setting. Conventional point gauges were installed at key locations on the pipeline. Fiber optic sensor cables were installed at key locations providing 14 alternative scenarios in terms of sensitivity, accuracy, and cost.After construction of the test pipeline, real time continuous monitoring via the array of conventional and fiber optic sensors commenced. A deep trench was excavated adjacent and parallel to the central portion of the pipeline which began to induce subsidence in the test pipeline. Continued monitoring of the various sensors produced real time visualization of the evolving subsidence. A comparison of the reaction of the sensors is compiled to provide an intelligent selection criteria for integrity managers in terms of accuracy, deployment, and costs for pipeline subsidence monitoring projects. In addition, further analysis of this sensor data should provide more insight into pipeline/soil interaction models and behaviors.Copyright