Ground Improvement Program Research Articles

The state of practice of in situ tests for design, quality control and quality assurance of ground improvement works

In the state-of-the-art report that was published on ground improvement processes at the 17th ISSMGE conference, ground improvement was defined in five categories. This paper has focused on the ground improvement techniques that either mechanically stabilize the soil or incorporate admixtures or inclusions and the most common in situ geotechnical tests that are used during the geotechnical investigation, quality control and quality assurance phases of these techniques. In addition to the suitability and feasibility of the technique itself, the level of success of any ground improvement program is also related to the applicability and suitability of the criteria that is to be satisfied and the testing campaign that is to be undertaken to verify the works. Experience of the authors indicates that the optimal approach is when acceptance is based on the project’s actual geotechnical requirements rather than on minimum test results. At the same time, ground improvement design parameters can only be properly determined when the ground conditions are correctly comprehended, which is possible through meaningful geotechnical investigation. Similarly, applied treatment can only be confidently verified when testing is able to well relate to acceptance criteria. Hence, tests that are able to predict the acceptance criteria without reliance on experimental correlations and published work from other sites will result in the best engineering practice and confidence in results.

Use of Reclaimed Asphalt Pavement in Conjunction with Ground Improvement: A Case History

The use of Reclaimed Asphalt Pavement (RAP) in lieu of virgin crushed stone aggregate is becoming a widely accepted practice for a number of construction applications, particularly pavement base courses. A number of laboratory RAP studies have considered the mechanical properties of RAP bases in order to support pavement designs incorporating RAP. These studies have revealed a number of interesting relationships between RAP moisture content, compaction, and stiffness. This paper discusses the experiences of a design-build contractor integrating a geosynthetic ground improvement program with a RAP base during the reconstruction of a 1.95 ha asphalt parking lot. Field observations of base course construction with RAP explore some of the implications of laboratory findings. A number of interesting observations on the technical, construction, and economic issues resulting from the project challenges and the use of RAP are presented.

Environmental quality criteria for fish farms in Japan

Environmental deterioration around fish farms has been widespread in Japanese coastal areas. In order to prevent self-induced deterioration of the surrounding environment, the “Law to Ensure Sustainable Aquaculture Production” was enacted in 1999. Criteria based on three indicators, i.e., (1) dissolved oxygen content of water in fish cages, (2) acid volatile sulfide content (AVS-S) in the sediment and (3) the occurrence of macrofauna under the fish cages were determined to promote the “Aquaculture Ground Improvement Program” by applying this Law. The second criterion (AVS-S) is based on the assimilative capacity of the sediments to organic wastes from a fish farm. For applying this criterion to each farm, the maximum phase in the process of biological remineralization must be detected for a farm site when the benthic oxygen uptake (BOU) rates shows maximum. The peak of BOU, however, could not be determined during a survey in Gokasho Bay, suggesting a need for reexamination regarding the practical application of this criterion. In order to obtain data for refining the third criterion (macrofauna), a quantitative survey was conducted at 22 fish farms (red sea bream and yellowtail) along the Kumano-nada coast, central Japan. The biomass of the macrobenthos peaked in sediments containing 1.2 mg/g of total nitrogen, where the majority of aerobic mineralization of the loaded organic matter is supposed to occur. In summer, animals were scarcely found in sediments with AVS-S>1.7 mg/g, suggesting that this is a critical condition for the fish farm environment. An index embayment degree (ED), which represents the topographic conditions of a farm site, is proposed to discriminate artificial factors arising from fish farming activities from the natural factors related to the topography. Community parameters of the macrobenthos and environmental factors were significantly correlated with ED ( P<0.001). In shallow, semi-enclosed sites (larger ED values), environmental deterioration and decreases in the benthic biomass were more conspicuous in large-scale farms than in small-scale farms. Six assemblages of the macrobenthos were identified by cluster analysis and were classified into three groups, indicating conditions as healthy, cautionary and critical, respectively. As fish production increased, habitat of the assemblage in the cautionary zone shifted to the offshore, deeper areas (smaller ED values), indicating that both of aquacultural activities and topographic conditions affect the species composition. Macrofauna, sediment parameters and the index ED are concluded as useful to develop pragmatic guidelines for site selection of fish farms.