Indian Geotechnical Journal

Sharma, Binu; Buragohain, Poly

doi: 10.1007/s40098-013-0091-1pmid: N/A

Micropiles have been installed on many projects in many parts of the world for different purposes like underpinning, seismic retrofitting, slope stabilization, resisting uplift dynamic loads. However information on the behaviour of micropiles when subjected to vertical and oblique pull is rather limited in literature. A model testing programme was designed and carried out to investigate behaviour of micropile groups under vertical and oblique pull out loads. Micropile groups having different length to diameter ratio and different spacings were grouted in sand having a relative density of 50 %. The groups were subjected to 0°, 30°, 60° and 90° pull. Ultimate pull out loads and efficiency were found to be a function of length to diameter ratio of the piles and angle of inclination of the pull out loads. Groups subjected to vertical pull failed by soil failure and groups subjected to oblique pull failed by structural failure.

Jisha, S.; Jayalekshmi, B.; Shivashankar, R.

doi: 10.1007/s40098-013-0095-xpmid: N/A

Three dimensional soil–structure interaction (SSI) analyses of tall reinforced concrete chimneys with annular raft foundation subjected to wind loads are presented in this paper. Different ranges of height and slenderness ratios of the chimneys and different ratios of external diameter to thickness of the annular raft were selected for the parametric study. To understand the significance of SSI, four types of soils were considered based on the stiffness. The chimneys were assumed to be located in terrain category two and subjected to a maximum wind speed of 50 m/s as per IS:875 (Part 3)-1987. The along-wind and across-wind loads were computed according to IS:4998 (Part 1)-1992. The linear elastic behavior was assumed for the integrated chimney-foundation-soil system and it was analysed using finite element software ANSYS based on direct method of SSI. The radial and tangential moments and settlement of annular raft foundation were evaluated through SSI analysis and compared with that obtained from conventional method of analysis as per IS:11089-1984, assuming foundation system is rigid. From the analysis, it is concluded that the SSI analysis results in higher radial moments and lesser tangential moments as compared to conventional method. All these variations depend on the geometric properties of chimney and annular raft foundations.

Banerjee, Subhadeep; Shirole, Omprakash

doi: 10.1007/s40098-013-0092-0pmid: N/A

The paper presents the results to study the response of piles in homogeneous and layered soils subjected to quasi-static and cyclic lateral loading using numerical analysis. The analyses are carried out using three-dimensional finite element software, ABAQUS v6.10. Hypoelastic constitutive model is used to simulate the small strain nonlinear behavior of soil observed during the application of cyclic lateral load on piles. The bending moment and deflection responses computed from ABAQUS analyses are compared with the results obtained from the reported case histories of field pile lateral load tests and centrifuge tests. The favorable comparisons established that the three-dimensional numerical analysis can be effective to model complex soil–pile systems. Numerical analysis was also able to simulate a cement injected layer as a reinforcement body to the soft foundation soil, which can affect the pile response. The study was further extended to understand, the effect of flow of surrounding soil around the laterally-loaded piles on the response of piles.

Pitchumani, N.; Madhav, Madhira

doi: 10.1007/s40098-013-0093-zpmid: N/A

Chennai Metro Rail Limited is constructing a state-of-the art depot at Koyambedu, in West Chennai over an area of 27 ha, for stabling and maintenance of the metro coaches. The highlight of the depot is that the 16 km of tracks within the depot will be ballastless. The rails will be embedded in a concrete slab track which will be laid on a hydraulically bound layer (HBL). A granular subbase separates the HBL from the subgrade soil. In the absence of the traditional flexible ballast, the tolerances for settlements are very limited. The geology of the site comprises of 6–12 m of soft clay at a depth of 6–8 m from ground level. Ground improvement using prefabricated vertical drains with surcharge was carried out so as to expedite the consolidation process. Plate settlement markers were installed at the original ground level and settlements were continuously monitored under surcharge load for the period until the incremental settlements were <10 %. The decision for removal of the surcharge was taken after the settlement readings had stabilised. The settlement readings are analysed to back calculate the consolidation parameters for the soft clay layer. The parameters evaluated are consistent with assumed values.

Samui, Pijush; Karthikeyan, J.

doi: 10.1007/s40098-013-0094-ypmid: N/A

The prediction of liquefaction susceptibility of soil due to an earthquake is an imperative task in Civil Engineering. This study uses relevance vector machine (RVM) for the prediction of liquefaction susceptibility of soil based on cone penetration test from Chi-Chi earthquake, Taiwan. RVM is based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Here, RVM has been used as a classification tool. It gives output in a probabilistic form. Equations have been also developed for the determination of liquefaction susceptibility of soil based on the RVM model. This study shows that only two input parameters [cone resistance (qc) and maximum horizontal acceleration (amax) are sufficient for prediction of liquefaction susceptibility of soil. The results of RVM have been compared with the conventional methods. The developed RVM model provides a viable tool for civil engineers to determine the liquefaction susceptibility of soil.