Jean Benoît

National Geotechnical Experimentation Sites

A system of National Geotechnical Experimentation Sites (NGES) is available in the United States. This program provides easy access to well characterized and documented field test sites with a wide range of geological conditions for the purpose of advancing the state-of-the-art in areas such as in situ testing, instrumentation, prediction of soil behavior and foundation prototype testing. This volume compiles technical information on the following NGES: Treasure Island Naval Station, Texas A&M University, University of Houston, University of Massachusetts at Amherst, Northwestern University and Spring Villa Test Site. Also included are papers describing a spectrum of applications for education and research using the NGES facilities and the associated database. This special publication ends with new directions planned for the NGES program.

Design of an Instrumented Flat Dilatometer

To better understand the mechanics of the flat plate dilatometer expansion, a probe has been developed to measure the continuous pressure-displacement soil response during the test. This paper presents details of a specially designed Marchetti dilatometer with sensors to record the continuous displacement of the membrane, unload-reload cycles, the pore water pressure, the total pressure, and the penetration thrust. With minimal impact on the original blade design, the resulting instrumented dilatometer was tested at the University of Massachusetts-Amherst National Geotechnical Experimentation Site.

Data dictionary and formatting standard for dissemination of geotechnical data

A pilot system for archiving and web dissemination of geotechnical data collected and stored by various agencies is currently under development. Part of the scope of this project, sponsored by the Consortium of Organizations for Strong-Motion Observation Systems (COSMOS) and by the Pacific Earthquake Engineering Research Center (PEER) Lifelines Program, is the development of a data dictionary and formatting standard. This paper presents the data model along with the basic structure of the data dictionary tables for this pilot system.

Field and Laboratory Densities of Municipal Solid Waste Incinerator ASH/Wastewater Sludge Mixtures in a Codisposal Above-Ground Landfill

Summary Geotechnical properties of a 5:1 (volume:volume) municipal solid waste bottom ASHrdewatered wastewater sludge mixture were evaluated for the purposes of design consideration and management of an above-ground, side-slopped ASH/sludge landfill. Laboratory proctor density testing and field density evaluation of the compacted ASH/sludge mixture using a variety of construction equipment indicated that the mixture can be compacted to dry densities up to 1.2 5 t/m 3 at moisture content ranging from 3 0 to 60 percent. The water content appears to be the only variable controlling compaction of this well-graded material. Vibratory and kneading type compaction, lift thickness, number of passes, and age of the mixture did not significantly influence the compactibility of this generally wet-of-optimum mixture. However, compaction does increase disposal capacity 5 to 20% by simple use of a bulldozer to achieve maximum densities.

Some Factors Affecting In Situ Measurement Using the Cambridge Self-Boring Pressuremeter

Research presented in this paper was conducted to assess the influence of environmental and physical factors on measurements made with the self-boring pressuremeter (SBPM). It was found that temperature changes during deployment and long-term instrument calibration drift can result in misinterpretation of in situ soil properties. It was also observed that neglecting to consider the sequential order of strain arm lift-off and radial confinement in both membrane calibration and data reduction can have an effect on interpretation of horizontal stresses, particularly in soft clays. Control experiments were conducted to quantify the effect of these factors. Based on the results of these experiments, a method for assessing excess pore pressure at the beginning of a test using the standard Cambridge SBPM transducers was developed. This method incorporates findings from temperature behavior tests. In addition, a modified method of membrane stiffness correction is proposed which includes consideration of sequential order of lift-off and confinement effects.

Enhancing Geotechnical Investigations Using Drilling Parameters

AbstractGround investigation techniques such as the pressure meter and the standard penetration test give discrete distribution of information with depth, whereas few others such as the cone penetr...

Design and Testing of a Debris Flow ‘Smart Rock’

This paper describes the development of a “smart rock,” an instrumented device for the study of debris flows, which is often triggered by earthquakes, heavy rain events, and rising groundwater conditions. Debris flows are very destructive forms of landslide consisting of a mixture of rocks, saturated soil, and debris typically flowing at high rates of speed and over long distances. In an effort to better understand the mechanics of debris flows, the smart rock was developed with a sensor package to be used in U.S. Geological Survey experiments at their flume facility in the Willamette National Forest, OR. The instrumented rock contains an inertial measurement unit (IMU) to measure acceleration and rotation rate about three body fixed axes, and two pressure sensors to measure pore water pressure. The sensors provide information about the movement of the rock and pore water pressures within a debris flow. One of the objectives of the sensor package is to use this information to track the position of a particle in the flow with an accuracy of 1 m over the course of 10 s. Calculation of position using the IMU requires the use of strapdown inertial navigation equations. Unfortunately, noise and bias in the rotation rate sensor introduce significant error in the position calculation. The results from one of the USGS debris flow experiments using the smart rock show that an ad hoc filtering method on the IMU data provides a rough estimate of the rock position in the flume, but far from the desired level of accuracy. Pressure and velocity recorded by the smart rock, while comparable to those measured by the USGS during the debris flow test, cannot be verified. Position accuracy can only be improved by using a better IMU and obtaining known rock positions versus time during the debris flow. Based on the results of this work, it is hoped that improved technology will result in a smart rock that can successfully provide useful and insightful debris flow data.

DMT Testing for Site Characterization and QA/QC on a Deep Dynamic Compaction Project

This paper describes the use of the Marchetti flat dilatometer (DMT) on a major highway relocation project in Carver, Massachusetts (USA). Parts of the new highway span former cranberry bogs. Sheet piling was installed along both sides of the new highway alignment, and organic material was dredged from between the sheet pile walls. The area was then backfilled with sands. Since most of the sand was placed in a fairly loose state under water, liquefaction was a potential problem. Therefore, deep dynamic compaction (DDC) was used to densify the fill. An extensive in situ testing program was instituted to characterize site conditions prior to densification, and to assess the sufficiency of the DDC after treatment. The results of this study suggest that the DMT can be used to provide accurate and cost-effective stratigraphic profiles. The DMT was particularly helpful in identifying pockets of organic soils (i.e., peat) that were not completely removed during the initial dredging operations. In terms of compaction QA/QC, the modulus values determined from the DMT appear to be very sensitive indicators of densification effects.

Sled for In Situ Penetration Testing

In situ testing devices such as the dilatometer, the piezocone, the pressuremeter, and the field vane generally require the use of a drill rig for penetration through soils. This paper describes a multipurpose portable pushing frame built at the University of New Hampshire and designed to be used with most in situ testing probes. This rig is compact, inexpensive, easy to use, and can operate on sites usually not accessible to conventional drilling rigs.