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I served as a geotechnical expert for the U.S. Department of Justice (DOJ) supporting the defense of the U.S. Army Corps of Engineers (USACE) against alleged professional negligence in its design of the flood walls for the Inner Harbor Navigation Canal (IHNC). A group of attorneys representing individuals affected by the levee failures launched a lawsuit, as Plaintiffs, seeking tens of billions of dollars of restitution from the U.S. government. This article briefly describes the case and its outcome, focusing on the different theories of failure for two flood wall breaches and presenting my assessment of the failures based on additional investigations.

This paper aims to demystify the use of risk assessment as a decision management tool and present a methodology that places quantitative risk assessment within reach of every geotechnical engineer, even for routine engineering assignments. In particular, we propose using quantification of expert judgment (i.e., subjective probabilities) as a practical alternative for determining probability of slope failure. The writers present a semiempirical relationship between factor of safety and annual probability of failure that permits estimation of slope failure probabilities with relatively modest effort. The case study for a tailings dam shows that risk assessment based on quantification of expert judgment provides a framework to arrive at rational management and engineering decisions related to dam safety and other geotechnical problems. Using the semiempirical relationship presented here, practicing engineers can use this helpful tool by applying their current skills.

The Kentucky Lock Addition project is the construction of a new 34 m wide by 366 m long navigation lock that will be located landward and adjacent to the existing 34 x 183-m lock. The U.S. Army Corps of Engineers, Nashville District, has the primary responsibility for designing and constructing the project and will operate the lock once it is complete. However, the Tennessee Valley Authority (TVA) is an active partner in the new lock since it will be an integral component of TVA's Kentucky Dam Prior to construction of the new lock, a cofferdam had to be built to act as a temporary dam to hold back upstream water (Kentucky Lake). Once the cofferdam was constructed, excavation began for the new deep foundation by removal of soil material downstream from the cofferdam and immediately adjacent to the existing land-side lock wall. This leaves the cofferdam and existing lock wall unrestrained on the exposed land side which could result in movements or instability that could cause life-safety issues to construction workers, construction delays and closure of the existing lock. Having both the water loads on only one side of both the cofferdam and existing Lock wall required installation of an autonomous sensor array to continuously monitor horizontal soil displacement (in-place-inclinometers), water levels (piezometers) and Lock wall movement (tilt meters and joint meters). Data was automatically collected from IPIs, Piezometers (cofferdam), tilt meters and joint gages (Lock Wall) from remotely positioned Data Loggers powered by solar panels. Each sensor has limit values assigned that when exceeded, trip email messages to staff that allow for remote access and review of data for decisions related to changes in construction sequencing or implementation of contingency plans. The system is integrated into Geocomp’s iSiteCentral GIS database software for ease of data collection, review and reporting. Each data logger location and sensor is superimposed onto an aerial plan view of the project site. The sensor icons are active and provide pull-up plots of active, near real-time data. This system has been in continuous operation since 2008, providing continuous 24/7 monitoring and reducing risk for both the Contractor and Owner. 2519 IFCEE 2015 © ASCE 2015

Some would argue that the introduction of new information technology tools into geotechnical engineering will soon obviate the need for engineering judgment. Nothing could be further from the truth.

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.

Instrumentation and monitoring of dams, levees and impoundments plays an important role helping to manage safety and risk. The technologies to instrument and monitor have experienced remarkable change and growth over the past 20 years. This paper summarises the current state-of-practice of instrumentation and monitoring for dam, levee and impoundment safety. The paper presents and discusses reasons to monitor performance, recent technological advances in instrumentation and monitoring, and some recommended practices. Instrumentation and monitoring, combined with vigilant visual observation, can provide early warning for many conditions that contribute to dam failures and incidents. But instrumentation and monitoring must be carefully planned and executed to meet defined objectives. Data must be conscientiously collected, reduced, tabulated and plotted in a timely manner to determine what it indicates about the safety of the dam. The monitoring team must understand the significance of changes and trends. They should have action levels defined for taking action and a contingency plan in place to carry out when required. A principal theme of this paper is the important role of instrumentation and monitoring in helping to identify and manage risk associated with potential failure of these structures. When considered as a part of a risk management programme, the role and value of an instrumentation and monitoring programme becomes clearer to all involved.

Hartsfield Jackson Atlanta International Airport (H-JAIA) added a $1.4 billion new International Terminal, namely Maynard Holbrook Jackson International Terminal (MHJIT). During this project, the existing Automated People Mover (APM) tunnels were extended from west of Concourse E to MHJIT. The type of excavation was open cut, approximately 70 feet wide and 50 feet deep. The excavation was supported by micro piles, soldier pile/timber lagging system and tie back systems and underpinning piers to a depth of approximately 50 feet below the existing grades. Movement and settlement of the existing test track tunnel and Concourse E was a concern due to unbalanced earth loads and existing foundations for Concourse E. Approximate length of new APM tunnel underneath Concourse E was 1200 feet and underneath Taxiway Dixie was 900 feet. To monitor the settlement and movement, Automated Total Stations (AMTS), Uni-axial and Bi-axial inclinometers were installed. Data generated by the monitoring systems were captured real time and used to provide early warnings and unexpected behavior of the structures associated with the new construction. The risk management program includes alarms generated from the system thru email when measurements exceeded the threshold limits and triggered a plan of action to avert any potential disaster.

Instrumentation and monitoring of earth structures has experienced phenomenal change and growth since the last slope stability conference some twenty years ago. This paper gives an overview of the current state-of-practice of instrumentation and monitoring for slopes and embankments and other structures that involve global instability considerations. Reasons to monitor performance, technological revolutions in instrumentation and monitoring over the past 20 years and some recommended practices are presented and discussed. A principal theme of this paper is the important role of instrumentation and monitoring in helping to identify and manage risk. When considered as a part of a risk management program, the role and value of instrumentation and monitoring program becomes much clearer to all involved.

Atlanta's International Airport is adding a new $1.2 Billion International Terminal. The Automated People Mover (APM) trains are extended beneath an existing terminal to the new one via twin open-cut tunnels as wide as 67 feet. The excavation was braced by a soldier pile/lagging/tieback system and underpinning piers to depths of about 40 feet. Movement of the adjacent existing tunnel and building was a concern due to unbalanced earth loads and the potential for unexpected behavior. To manage this risk, a real-time, performance monitoring program was used to provide early warnings of unacceptable or surprise performance to implement protective measures to stop/reduce the consequences. The risk management program included alarms generated from the system via email when measurements exceeded safe values and a plan of action to engage contingency measures. The plan was used to avert potential disaster as well as long delays in the construction schedule.

Many structures located close to excavations are damaged by excessive ground movements during construction. This is partly due to limitations of commonly used methods to design the excavation support system. The authors propose using a displacement-based design method that focuses on designing to keep movements within allowable values. A step-by-step approach for the method is described and illustrated for a deep excavation into soft clay.

The products of the Information Age give geotechnical engineers powerful tools to perform their work. One view of geotechnical engineering is that Information Technology (IT) tools may replace many of the functions that geotechnical engineers now perform. This view can be framed to argue that the right IT tools will even replace the need for engineering judgment. Since geotechnical engineers rely heavily on their engineering judgment to formulate and defend their arguments, this view would mean a major change in the way we do geotechnical engineering. This paper looks at geotechnical engineering in today's IT dominated world and considers ways that geotechnical engineering may change as the IT tools become increasingly powerful and pervasive. The paper's aim is to stimulate people's thinking about how we can make more effective use of IT tools in our future work. For experienced engineers, the result is insight to the important role of engineering judgment in an IT dominant world. For young engineers, the paper provides perspective on the role of IT tools in engineering practice and how they may develop their judgment skills. For non-engineers, such as owners, regulators and attorneys, the paper can help them better understand how geotechnical engineers think, or should think.

Geotechnical laboratories have traditionally tracked laboratory samples with hand-written labeling systems and recorded test data in hand-written records. These records are then used to produce hand-written reports or manually entered into data reporting software to generate reports. This approach consumes a lot of man-time and presents many opportunities for errors. GeoTesting Express has developed and implemented a new process for sample tracking, data management and test reporting to improve the laboratory’s performance. Central to the process improvement is the design and implementation of a new Laboratory Information Management System (LIMS) which allows for sample tracking and status updates while also eliminating hand written data and manual data entry for production of reports. This paper shows how the implementation of this new LIMS has benefited our laboratory by decreasing turnaround time, decreasing production costs and reducing errors.

The Central Artery/Tunnel Project in Boston, Massachusetts is the largest, most complex highway project in American history. It involves the construction of 7.5 miles of highway through the center of the city with half the work occurring underground. Several conditions favored an extensive geotechnical monitoring program to provide engineers and contractors with up-to-date performance information. This paper describes the data acquisition and management processes used to collect, store, validate, reduce and report data from a large number of geotechnical instruments. It also describes some of the unique experiences presented by this challenging project.

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.

Backfill materials used in utility trenches must maintain physical and mechanical integrity when subjected to the seasonal effects of freezing and thawing. Materials used over gas utility lines must also have adequate permeability to allow any leaking gas to flow upward and out. To help determine how soils and flowable fills might perform as backfill over utility lines, we conducted laboratory tests to measure the permeability of backfill materials before freezing, during freezing, and after thawing. The two materials investigated in this study were a silty sand, and a flowable fill made with Type F fly ash. Our work also examined the susceptibility of these materials to frost heave and thaw weakening. An apparatus and standard test method for performing permeability during freezing and after subsequent thawing did not exist. We developed a method by adapting the ASTM Standard Test Method for Frost Heave and Thaw Weakening Susceptibility of Soils (D 5918) and the ASTM Standard Test Method for Measurement of Pneumatic Permeability of Partially Saturated Porous Materials by Flowing Air (D 6539). Although more data are needed to confirm specific conclusions determined from this study, the test method developed here appears to be useful for evaluating the effects of freeze-thaw on backfill materials for utility trenches. Additional work is needed to demonstrate whether these laboratory results correspond to actual field conditions.

An approach is presented to ensure the safety of a constructed facility by outlining, discussing, and illustrating various components of a comprehensive safety program. When dealing with important complex geotechnical facilities, experience clearly shows that the geotechnical profession cannot feasibly create a facility which completely fulfills all performance criteria for the entire life of the facility. Rather, the only logical approach is to engineer a facility for its design life, i.e., create a reasonable design, construct the facility according to the design, and then execute an appropriate ongoing safety program. The comprehensive safety program consists of nine components. These components are described, and several are illustrated, using experience from actual project.

An analytical model has been developed to predict permanent stresses and strains in sands under cyclic loading for general drainage and boundary conditions. Here the model is combined with the finite element method to predict the permanent displacement of a storm barrier under combined tidal and wave loading. The results are compared with predictions from previous analyses, yielding a good correlation. The effects of drainage conditions and soil densification on permanent displacement are evaluated. The results demonstrate the importance of including in the pore pressure calculation the effects of both the tendency for volume change and the change in the average total stress.

This paper updates the stress path method proposed by the first writer in 1967. Use of the method by the writers in their teaching and practice has helped evolve it into a systematic approach to elucidating and solving geotechnical problems. The underlying principle of the stress path method states that the behavior of a soil element depends on the stress path for the history and for the stressing the element will receive in the future. This paper presents the stress path method as a series of six steps that help identify and interrelate the fundamentals underlying a geotechnical situation involving force, deformation, stability, or fluid-flow. The paper gives desirable features and limitations of the method and illustrates the method by evaluating the likelihood of a shallow slide in the downstream face of a dam.

Performance criteria for the settlement of large steel tanks used to store fluids at ambient temperature and pressure are presented. Where possible, the criteria include a factor of safety, defined as the ratio of tensile stress to developed stress. Permissible values of factor of safety for safe operation are indicated. The performance criteria are developed by interpreting and expanding previous studies, making approximate analyses, and analyzing the measured performance of 90 large tanks, including the tanks at Toa Nenryo Kogyo's site at Kawasaki City, Japan. For each criterion, the mechanism of failure, the structural element to which the criterion applies, and the basis for the criterion are identified.

The permanent deformation of soils as the result of cyclic loads is an important consideration in the design of offshore structures. Experimental studies show that the permanent strains are influenced by the porosity, the intitial shear and effective normal stresses, and the amplitude of the cyclic shear stress, as well as by the number of cycles of loading. These effects are combined into a logarithmic relation. The resulting equations have been incorporated into a finite element program that calculates permanent displacement without changes in net boundary loads or stresses. The analyses are applied to a proposed offshore barrier to show the importance of the ways in which cyclic loads combine with monotonic loads due to tides to give permanent displacements.