Napat Intharasombat

Laboratory investigations to address the use of compost amendments to enhance expansive subsoils

The process of composting of organic wastes is expanding rapidly in the United States and other countries since landfill spaces or disposal of organic wastes are becoming scarce and expensive. Compost materials, given their moisture affinity and low hydraulic conductivity, can provide stabilization of natural expansive soils by mitigating shrinkage cracking and encapsulating subsoil surfaces. To verify these advantages, a research study was conducted to measure the geotechnical characteristics of composts and compost treated topsoils (CMTs). Two types of composts, Dairy Manure and Biosolids, and a local expansive soil were used as materials. This paper presents laboratory test results from Atterberg, organic content, direct shear strength, free swell, linear shrinkage, and hydraulic conductivity tests and analyses of these results to evaluate the potential applications of CMTs to serve as highway shoulder covers to mitigate shrinkage cracks. The results indicate that shrinkage strains are reduced and strength and swell strains are increased with the use of compost amendments. Environmental assessments including the presence of organic matter are also addressed.

Experimental investigations to evaluate benefits of using compost amendments to modify expansive soils

Composting is a successful method of recycling organic waste materials such as yard trimmings, municipal biosolids, animal manure and organic urban wastes into stabilised materials that could be used for bioremediation, erosion control, landscaping, and roadside vegetation. The process of organic wastes composting is expanding rapidly in the USA and other countries since landfill spaces for disposal of organic wastes are becoming scarce and expensive. Researchers and practitioners always seek new application areas for composts. Compost materials, given their moisture affinity (hydrophilic characteristics) and low permeability characteristics, could provide stabilisation of natural expansive subgrades by mitigating shrinkage cracking and encapsulating subsoil surfaces. In order to verify these advantages, a research study was conducted to measure geotechnical characteristics of composts and Compost-Treated Topsoils (CMTs). Two types of composts, dairy manure and biosolids, and a local expansive soil were studied. This paper presents the laboratory test results, which showed that compost amendments resulted in the reductions of linear shrinkage strains and increase of shear strength and swell strains. Ranking analyses of test results also showed that compost amendments provided low to moderate enhancements to subsoil properties. Currently, field studies are being conducted to address potential applications of CMTs as unpaved shoulder covers to encapsulate and maintain compaction moisture conditions.

Quality of Runoff Leachate Collected from Biosolids and Dairy-Manure Compost-Amended Topsoils

Compost amendment of pavement shoulder subgrades was attempted to mitigate shrinkage cracking, which otherwise would result in severe distress to adjacent pavement infrastructure systems. Two types of composts, biosolids and dairy-manure composts, were evaluated. As a part of this application, the runoff leachate emanating from the compost soils needs to be environmentally assessed as this leachate potentially ends up in storm sewer collection systems. As a part of the research, runoff collection systems were placed in both dairy-manure and biosolids compost-amended soil sections and a control untreated soil section. The collected water samples at various time intervals were then subjected to various chemical and environmental tests, including total suspended and dissolved solids, biochemical and chemical oxygen demand, total Kjeldahl nitrogen (TKN), and phosphorous measurements. This paper presents a summary of these test results from both sections and their comparisons with similar results from another ...

REVIEW OF CURRENT METHODS FOR SWELL CHARACTERIZATION OF SUBSOILS FOR TRANSPORTATION INFRASTRUCTURE DESIGN

Expansive soils exhibit large volume changes due to moisture content fluctuations from seasonal changes. These volume changes cause extensive damages to geotechnical infrastructure. Several methods are available in the literature using different test methods and loading conditions to characterize expansive soils. The selection of an appropriate characterization method is always a challenge to the practicing engineer. A few case studies are presented to explain the need for better descriptions on different characterization methods using swell strain and swell pressures for estimating the severity nature of expansive soils. Both tables and pressures are presented and discussed. The details presented in this paper are useful to provide reliable characterizations for expansive soils and offer assistance to practicing engineers towards better design and selection of subgrade foundations and stabilization methods.