Honkanadavar N.P.,Central Soil and Materials Research Station |
Sharma K.G.,Indian Institute of Technology Delhi
International Journal of Geomechanics | Year: 2014
Modeled rockfill materials were obtained from nine sites (two riverbed and seven quarried) from different projects in India and Nepal, and drained triaxial tests were conducted with specimens that were 381mmin diameter and 813mmhigh. Index properties of the rockfill materials, namely, unconfined compressive strength (UCS) and uncompacted void content (UVC), were determined. An elastoplastic hierarchical singe-surface (HISS) constitutive model was used to characterize the behavior of modeled rockfill materials. The predicted stress-strainvolume change behavior was compared with the observed behavior, and it was found that both observed and predicted behavior matched closely. Procedures have been developed to predict the shear strength and elastic parameters of rockfill materials using the index properties, namely, UCS, UVC, and relative density (RD), and predictions were made satisfactorily. Predicted shear strength and elastic parameters were compared with the experimental values, and it was observed that both values matched closely. Then these procedures were used to predict the elastic and shear strength parameters of large-size prototype rockfill materials. Relationships were also developed between index properties and strength parameters of modeled rockfill materials and were used to predict the strength parameters for the prototype rockfill materials. Using the predicted material parameters, the stress-strain-volume change behavior of prototype rockfill material was predicted using the elastoplastic HISS constitutive model. © 2014 American Society of Civil Engineers.
Kumar R.,Central Soil and Materials Research Station
Water and Energy International | Year: 2012
Alkali-aggregate reaction causes significant damage to concrete structures worldwide particularly to hydraulic structures such as dams, barrages etc. This harmful reaction can occur if the alkali content of the cement and the presence of reactive minerals in the aggregate are high and enough moisture is present to sustain the reaction. Under some conditions, the reaction may result in slow but progressive expansion and cracking of the concrete. This paper presents the studies to control the alkali aggregate reaction in hardened concrete in their service life for Water Resources Projects. As we are aware that the alkali aggregate reaction in concrete is just like a cancer and it is very difficult to control it once started. The pozzolans and other materials can be used to control the alkali aggregate reaction in concrete. Studies have been conducted using the reactive aggregate, water proofing agents, geomembrane, pozzolans etc. to control the alkali aggregate reaction in concrete and their effects have been examined. Results of the study showed that the water proofing agent by crystallization technique noticeably reduces the residual alkali aggregate reaction in the hardened concrete than the other measures.
Singh R.,Central Soil and Materials Research Station
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014
This paper deals with the evaluation of deformability of rock mass in Himalayas by conducting in-situ tests with different methods. The deformability tests conducted by using plate jacking test, plate loading test, Goodman jack test and laboratory test show the comparison among different measurements and scale effects on deformability of rock mass. Plate load test, flat jack test and Goodman jack test give values of modulus of deformation which are 2-3 times lower than large size plate jacking test. Hence, large size plate jacking test must be utilized to evaluate the modulus of deformation of rock mass due to jointing in Himalayan geology. The modulus of rock tested in the laboratory is 3 to 20 times higher than insitu value of rock mass. The difference is mainly dependent on jointing in the rock mass. The indirect methods based on rock mass classification systems can also be utilised effectively by comparing modulus of deformation of rock mass by in-situ testing. © 2014 by Japanese Committee for Rock Mechanics.
Singh A.,Central Soil and Materials Research Station |
Gosain A.K.,Indian Institute of Technology Delhi
Water International | Year: 2011
A GIS-based Soil and Water Assessment Tool (SWAT) model is used to assess the impacts of climate change on the hydrological regime of the Cauvery river basin. First, the impact of changes in land-management practices on water availability under present conditions is modelled. Then, the same analysis is carried out under the future climatic scenarios. Finally, annual and monthly precipitation variability is compared under present, as well as future, climate-change scenarios. The results indicate an intensification of the hydrological cycle in the future climate-change scenario that appears to be significant on an annual basis. © 2011 International Water Resources Association.
Singh R.,Central Soil and Materials Research Station
47th US Rock Mechanics / Geomechanics Symposium 2013 | Year: 2013
This paper deals with measurement of upheaval in rock mass and remedial measures to tackle this problem. The tunnel was excavated using DRESS (drainage, reinforcement, excavation and support system) methodology in extremely poor strata in 298m reach of the 23 km long head race tunnel. Instrumentation and quality control measures were implemented in tackling the adverse geological conditions. The rock mass in this reach was completely pulverised bands of quartzite, amphibolite and quartz biotite schist inter mingled with clayey mass and drippings/water seepages which resulted in unstable crown and face, large over breaks and flowing rock mass conditions. The upheaval was noticed during muck removal for tunnel lining. The bottom struts were damaged due to upheaval and were replaced by new one before the final lining of tunnel. The upheaval of rock mass has been discussed in details along with remedial measures and excavation methodology. Copyright 2013 ARMA, American Rock Mechanics Association.