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The Indian National Gas Hydrate Program Expedition 02 (NGHP-02) was the most comprehensive gas hydrate drilling expedition carried out to date. From 74 pressure cores that were successfully recovered from various site locations offshore India, 19 subsamples were obtained for further detailed geotechnical analysis using the PCATS Triaxial apparatus to investigate the geomechanical behaviour of the cores, including small-strain stiffness, G max , undrained shear strength, S u , as well as direct-flow measurements of permeability, k. Samples tested included fine-grained muds with no appreciable hydrate through to coarse-grained sands that contained extensive hydrate within the pore space. Although the subsampling and transfer of pressure cores into the PCATS Triaxial under zero effective confining stress, σ′ , remains challenging, 12 samples were successfully transferred and underwent detailed geotechnical characterization. During consolidation, after reapplication of in-situ σ′ , all samples experienced axial and radial consolidation, with variations between samples seemingly dependent on the degree of sample disturbance, stress relaxation between coring and testing, hydrate saturation, S h and grain size, D 50. The largest values of G max were obtained from samples with high S h in the pore space, with values much higher than that expected for similar sediments without hydrate under comparable σ'. Samples with high permeability had both high S h and larger grain size, suggesting that in coarse-grained sediments sufficient pathways are available for reasonable fluid flow even with high hydrate saturations. Triaxial testing and unconfined compression tests highlighted the influence of hydrate on increasing sediment strength, although the size of the sediment grains appeared to have an important control on the magnitude of the strength increase and the overall stress-strain behaviour. The results from the detailed geotechnical characterization of the recovered pressure cores will be invaluable in helping India identify potential locations for future gas production wells, and assess the long-term performance of such reservoirs. • Testing of pressure core samples using PCATS Triaxial apparatus was undertaken. • Induced strains during consolidation are influenced by test and sample conditions. • Permeability of hydrate-bearing sediments are greater than fine-grained sediments. • Hydrate cement increases strength/stiffness of coarse-grained sediments. • Increases in strength/stiffness influenced by grain size and clay content. [ABSTRACT FROM AUTHOR]

Mine overburden removed during surface mining is considered as “waste” or “spoil” that is consuming a vast tract of land for storage. Due to high ash content (30–50%) of Indian coals, 130 million tons of fly ash per year is generated with less than 50% of it is being used. Many a time thermal power plants are close to coal mines. Hence, in the present study it is proposed that a mixture can be prepared using fly ash and coal mine overburden with or without cement, which can be used as a stabilized pavement material. The present study deals with characterization of cement stabilized mine overburden fly ash mixture as a pavement material. Mixtures with varying cement percentage of 4–7% were prepared. Based on the unconfined compressive strength and California Bearing ratio values of the stabilized mixture, it was observed that it can be used as a stabilized pavement material. [ABSTRACT FROM AUTHOR]

Utilization of reclaimed asphalt pavement (RAP) in the construction industry is gaining an advantage over conventional materials in terms of sustainable credits. However, the amount of production of RAP and its utilization has no comparison. The general practice is to replace a small fraction of virgin aggregates with RAP, usually restricted to a maximum of 30%, in base layers to promote RAP usage in the pavement industry. The present study focuses on the utilization of a high proportion of RAP (>50%) substitution in virgin aggregates (VA) as a base material in low volume roads (LVR). Mixes containing 100:0, 80:20, and 60:40 proportions of RAP:VA stabilized with different dosages of fly ash were evaluated for maximum dry density (MDD), optimum moisture content (OMC), unconfined compressive strength (UCS), resilient modulus (Mr) and California bearing ratio (CBR). It was observed that the 80:20 RAP:VA design mix with 40% fly ash meets the design requirements (UCS > 1.7 MPa and CBR > 80%) specified by the Ministry of Rural Development (MoRD), Government of India, and was considered to be an optimum mix. An example is discussed to design an LVR with an optimum mix according to the Indian Roads Congress (IRC) and AASHTO methods. The results revealed that the fatigue and rutting strains are well within the permissible limits for the new mix. The new mix design proved economical, as there was a 50% reduction in base layer thickness compared with the conventional design mix. [ABSTRACT FROM AUTHOR]