During the construction of earth structures, it is essential that the fill material be uniformly compacted to meet the compaction specification requirements. Current compaction verification methods require field inspectors to perform in situ quality assurance/quality control (QA/QC) "spot tests" at a finite number of locations within the compacted area. As a result, a large percentage of the compacted area remains unverified. Innovative compaction verification techniques have been developed, such as continuous compaction control (CCC) and intelligent compaction (IC) systems, which provide real-time monitoring and feedback about the operation and performance of soil compaction. Typically, these CCC and IC systems measure the response of the coupled soil-drum interaction using indicator values which relate to the soil stiffness. To encourage adoption of IC and CCC technology, it is beneficial to have these technologies incorporated into construction specifications. Relating these "new" intelligent compactor measurements to more traditional in situ localized "spot test" results helps to illustrate their effectiveness, and makes users more comfortable with their deployment in a field environment; it can also help in the development of new specifications. This paper examines the relationship of two CCC measured values, compactometer value (CMV) and machine drive power (MDP), with measurements taken from four different in situ test devices, including the nuclear density gauge (NDG), lightweight deflectometer (LWD), soil stiffness gauge (GeoGauge), and dynamic cone penetrometer (DCP). The use of both univariate and multivariate regression analysis were examined to develop relationships between CCC measurements and in situ test measurements. The resulting relationships may be used to assess the potential of CCC systems as a QA/QC method for compaction verification of soils.

The New Jersey Turnpike Interchange 14A project involved the construction of embankments up to 34 ft in height to support twelve new roadways. Innovative ground improvement methods were needed to meet the significant challenges for the project which included: poor subsurface conditions, space constraints, existing/proposed utility constraints, an aggressive construction schedule, and the immense size of the project. A variety of ground improvement methods were utilized to limit settlements and ensure stability of the embankments. These methods included preloading with surcharge and prefabricated vertical drains, load balancing using lightweight fill, and rigid inclusions (RI). The proposed roadways were divided into six zones, based on location, subsurface condition, and embankment height. This paper focuses on the ground improvement performed in Zone 2, which consisted of concrete column rigid inclusions. The problematic subsurface conditions in Zone 2 consisted of up to a 25-ft thick layer of highly-compressible peat and organic soils without ground improvement. These soils were estimated to undergo up to 4 ft of primary consolidation settlement due to the proposed embankment loads. The design of the RIs was performed by a specialty ground improvement contractor (SGIC) using Plaxis 2D and 3D software. The performance of the Zone 2 concrete column rigid inclusion systems was verified and monitored by load tests and instrumentation. This paper presents details of the concrete column rigid inclusion design, construction, monitoring results, and lessons learned.

Modern compaction equipment can be outfitted with sensors that allow for real-time monitoring of the compaction process, an approach that is commonly referred to as continuous compaction control (CCC). This paper describes the results from an experimental research study that was conducted to assess the effectiveness of CCC technology for construction of a roadway embankment using a sand containing a significant percentage of silty fines. During embankment construction, simultaneous machine drive power (MDP) and compactometer value (CMV) measurements were recorded, along with the corresponding position of the roller. Location-specific in situ “spot tests” were also performed to independently assess soil compaction, including nuclear density gauge (NDG) tests, soil stiffness gauge (SSG) tests, light weight deflectometer (LWD) tests, and dynamic cone penetrometer (DCP) tests. A comparison of the CCC measurements with the location-specific in situ test results was performed using spatial data analysis tools and statistical regression. The measured data, spatial and regression analysis approaches, and associated discussion that are presented provide valuable information for researchers and practitioners that are considering the use of CCC technology.

To replace a two-lane bridge nearing the end of its design life, the Delaware Department of Transportation used an innovative approach. Built using geosynthetic reinforced soil abutments and prefabricated bridge superstructure elements, the composite bridge was constructed rapidly and has been equipped with a custom-designed instrumentation system to monitor long-term performance.

An innovative alternative to conventional bridge support technology, the Federal Highway Administration's (FHWA) geosynthetic-reinforced soil-integrated bridge system (GRS-IBS) utilizes closely spaced layers of geosynthetic reinforcement and compacted granular fill material to provide direct bearing support for structural bridge members. This new technology has a number of unique advantages, including reduced construction time and cost, generally fewer construction difficulties, and easier maintenance over the life cycle of the structure. This technology can also perform well under a variety of static and dynamic loading conditions if designed and constructed properly. These advantages have led to a significant increase in the rate of construction of GRS-IBS structures in recent years. This paper provides details about the implementation of a GRS-IBS project in Delaware, the first project of this type in the state. An overview of the design and construction process for this project is provided, along with a brief description of a custom-designed instrumentation system for monitoring the long-term performance of the GRS-IBS.

When constructing earthen embankments, it is essential that the soil be placed and spread in uniform lifts prior to compaction. To ensure that the resulting soil lifts are evenly compacted, typical compaction specification approaches place restrictions on the thickness that is acceptable for each soil lift. In current practice, it can be extremely difficult for a field inspector to verify that lift thickness requirements are being met when soil is being placed and spread over a large area, without the use of frequent surveying (which adds both costs and delays to earthwork projects). Recent advances in compaction control include the development of continuous compaction control (CCC) and intelligent compaction (IC) systems, which provide real-time monitoring and feedback about the operation and performance of soil compaction. Typically, CCC and IC compaction equipment is outfitted with a real-time kinematic global positioning system (RTK-GPS) that monitors and records the position of the compacter as the soil lift is being compacted. This paper suggests that geotechnical engineers use field RTK-GPS measurements that are made by CCC or IC equipment to monitor and control the thickness of compacted soil lifts. Data collected from a full-scale field study is used to illustrate the practical issues with using GPS measurements for field monitoring of lift thickness during construction of a roadway embankment, such as varying roller position from lift-to-lift and the measurement uncertainty associated with RTK-GPS measurement data. The use of both simple and sophisticated spatial analysis techniques are explored for interpolating measured field elevation data onto a uniform grid for lift thickness assessment. The resulting methodology that is presented can be utilized to build spatial maps of compacted soil lift thickness, a process that can be used to great benefit by field engineers who are trying to ensure the quality of compacted soil lifts.

A variety of specification methodologies have been proposed for integrating Continuous Compaction Control (CCC) measurements into existing quality assurance and quality control (QA/QC) protocols. This paper explores the use of alternative compaction specification approaches for performing QA/QC of compacted soils for embankment construction, using data collected during a field study where CCC equipment was used to construct a small embankment.

Several studies have been performed to evaluate the shear-rate dependency of the residual shear strength for clayey soils. From these studies, two general hypotheses have been proposed to explain the changes in shear strength that are observed at varying shear displacement rates: (1) changes in shear strength can be attributed to changes in the effective normal stress that are caused by development of shear-induced pore water pressures, and (2) changes in shear strength can be attributed to changes in the "mode of shearing". In order to illustrate the effect of the shear displacement rate on measured shear strengths, slow and fast ring shear tests were performed using the Bromhead ring shear device, on pre-sheared discontinuities in kaolinite. In the Bromhead ring shear device, it is difficult to measure the induced pore water pressure directly; consequently, this paper focuses on the effect of changes in the "mode of shearing". A Scanning Electron Microscope (SEM) imaging technique was used in this study, with magnifications in the range of 25X to more than 100000X. Comparisons between the image results and measured shear strengths are performed, and the relative contribution of the shear mode to the measured shear strengths is discussed.