Department of Civil Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Geosynthetic encased stone columns have been widely recognized as an efficient and cost-effective ground improvement technique for improving the load carrying capacity of soft soils. But, the conventional resources such as stone aggregates, gravel etc. are not able to cope with the high demand in the construction industry. Therefore, utilization of potential waste materials such as crushed construction and demolition debris (CCD) in lieu of conventional aggregates in stone columns is a viable and sustainable option. Hence, an attempt was made to use geosynthetics encased CCD columns in improving the load capacity of soft clayey soil. A series of load tests were carried out to examine the performance of soft clay reinforced with geosynthetic encased CCD columns. From the load tests conducted for various L/D (length of geosynthetic encasement to diameter) ratios of the stone columns, it was observed that with fully encased CCD columns, there is a maximum of about 6 fold increase in the load carrying capacity. Thus, CCD can be considered to be a good alternative for aggregates in geosynthetics encased stone columns.

World University root node

Geosynthetics Conference 2019

Behaviour of Geosynthetic Encased Crushed Construction and Demolition Debris Stone Columns

Post-tensioned girders with internal and external tendons are widely used for the construction of bridges because of their eminent advantages. However, owing to poor grout quality, damage to protective ducts, exposure to environmental conditions, overstressing of strands, and overloading of the girder, the external tendons are susceptible to corrosion and breakage of strands. It is important to identify loss in cross-sectional area of the strands, in order to take preventive actions to avoid loss in capacity, and in some cases even failure of the tendon. Magnetic Flux Leakage (MFL), a non-destructive evaluation technique, is used to detect and quantify metallic defects in external post-tensioning systems. In order to evaluate this technique in in-service bridges under field conditions, a full-scale post-tensioned girder specimen was constructed as a control specimen. Metal defects that include section loss, corrosion, and breakage in wire and single or multiple strands with known loss in cross-sectional area, were fabricated and placed in the external tendons. The MFL device is then used to evaluate loss in metallic area (LMA) in the control girder specimen. The MFL device consistently detects LMA greater than 5% of the total strand cross-sectional area for the group of strands in a tendon. The measurements are found to be repeatable and reproducible. Even though there are errors associated with the estimated LMA percentages, especially for defects with greater than 50% loss in cross-sectional area, the estimated magnitude of the loss in total strand cross-sectional area gives a good indication about the severity of the defect. © 2019 Elsevier Ltd

Engineering Structures

Magnetic flux leakage technique to detect loss in metallic area in external post-tensioning systems

Pile caps are critical structural members that transfer loads from columns and bridge piers to the pile foundation. They are large concrete blocks with significant disturbed (D-) regions, low shear span-to-depth ratio, low longitudinal reinforcement ratio, and typically no vertical ties which makes them vulnerable to shear failure. The current major concrete codes of practice suggest both the sectional approach, and the Strut-and-Tie Method (STM) for the design of pile caps. Neither of the approaches accurately capture the ultimate capacity, force-deformation behaviour, complex strain variation, or the final mode of failure of pile caps. Compatibility Strut-and-Tie Method (C-STM) is an efficient, minimalist, non-linear modelling approach that satisfies equilibrium, compatibility, and constitutive material relationships and effectively simulates the behaviour of shear-critical reinforced concrete members. A displacement based three-dimensional (3D) C-STM is proposed to simulate the behaviour of four-pile caps. Appropriate geometry and material constitutive relationships, including tension stiffening and softening effects, are incorporated into the model. The effects of concrete softening due to transverse tensile strains are also incorporated in the model. To establish the generality of the model, the load and deformation corresponding to cracking, yield, and failure of 33 four-pile cap specimens with varying shapes, sizes and material properties are considered. The model satisfactorily simulates the overall force-deformation behaviour, internal strain behaviour, and sequentially predicts the non-linear events that lead to the failure of the pile caps. The results from the 3D C-STM are in good agreement with the experimental results and observations of four-pile cap specimens. © 2019 Elsevier Ltd

Modelling four-pile cap behaviour using three-dimensional compatibility strut-and-tie method

ISSMGE TC107 Symposium on Laterites and Lateritic Soils

Geosynthetic filters to Prevent Soil Piping and Internal Erosion

ISSMGE TC107 Symposium on Laterites and Lateritic Siols, 20-21 September, 2019, Goa, India

Deformation behaviour of reinforced soil slopes subjected to rainfall induced subsidence

Uncontrolled dumping of huge quantities of calcium carbide residue (CCR) which is an industrial by product of acetylene gas industry is hazardous to environment due to its high alkalinity. Utilization of calcium carbide residue for stabilization of subgrade soils is a cost effective and sustainable practice, which can be adopted in design and construction of flexible pavements. In the present work, the efficacy of treatment with CCR in reducing the accumulation of permanent deformations in black cotton soil (BC soil) subgrade subjected to repeated loading is investigated. Untreated black cotton soil samples and CCR stabilized samples are subjected to repeated load triaxial tests for determining the accumulation of plastic strain with repeated loading cycles. Effect of cyclic deviatoric stress levels and moulding water content on the development of permanent deformation is examined. The accumulation of permanent deformation is quantified using the critical cyclic stress levels based on the shake down theory. The experimental data for the permanent deformation of treated as well as untreated soil samples is found to fit well with two the models (VTT model and power law model) reported in literature. The efficacy of CCR stabilization in reducing the permanent deformations of black cotton soil subjected to repeated loading is confirmed based on the mineralogical and morphological studies carried out on the treated samples. © 2019 Elsevier Ltd

Construction and Building Materials

Permanent deformation behaviour of black cotton soil treated with calcium carbide residue

The present paper proposes a new and simple mechanical model for predicting the maximum sloshing wave height (MSWH) in a partially filled, laterally excited cylindrical tank. The proposed model is a linear, two degree of freedom spring-mass-damper system which consists of two masses representing the sloshing and non-sloshing mass of the partially filled cylindrical tank. The model is validated through a series of experiments conducted on a cylindrical tank filled with water which is mounted in a slosh test rig. The proposed model successfully captures the beating phenomenon observed in sloshing wave height, when the tank is laterally excited near the resonant frequency of the liquid. The present study leads to a simpler, accurate and faster mechanical model which can predict the MSWH, frequency of sloshing liquid and the lateral sloshing force. The model can be readily used by the design engineers, instead of time consuming numerical models like computational fluid dynamics and smoothed particle hydrodynamics, in the preliminary design phase of any structure involving lateral sloshing and provide quick results which will substantially lead to shorter design cycle time. © 2019 Elsevier Ltd

Journal of Sound and Vibration

Development and validation of a simple two degree of freedom model for predicting maximum fundamental sloshing mode wave height in a cylindrical tank

The current paper proposes the formulation of beam elements using B-spline wavelet on the interval based wavelet finite element method by incorporating von Kármán nonlinear strains. Formulation is proposed for both Euler–Bernoulli beam theory and Timoshenko beam theory. A background cell based Gauss quadrature is proposed for numerical integration. Numerical examples are solved for transverse deflections and stresses in axial direction, and are compared with the existing converged results from finite element method. The issues of membrane and shear locking for the proposed elements are examined and solution techniques are suggested to overcome the issues. © 2018 Elsevier Inc.

Applied Mathematical Modelling

Construction of beam elements considering von Kármán nonlinear strains using B-spline wavelet on the interval

In southwestern Georgia, increased groundwater withdrawal for irrigation in the Lower Flint River Basin (LFRB) is greatly affecting the supply of freshwater to downstream regions during drought years. This study was undertaken to understand the sensitivity of groundwater components to changes in irrigation pumping scenarios during droughts in the highly connected karst Upper Floridan Aquifer (UFA) and assess the effectiveness of irrigation shutdown on stream-aquifer fluxes. This study was done using the United States Geological Survey (USGS) MODular Finite-Element Groundwater model (MODFE). The model was run for the water year 2011 and changes in simulated groundwater-budget components for monthly irrigation pumping rates of 50%, 75%, 100%, 125%, 150%, and 200% of that indicated by metered irrigation systems were quantified. The effect of irrigation shutdown in the vulnerable Spring Creek subwatershed was also investigated. Results show that increasing irrigation pumping in the study area decreased aquifer storage, induced recharge to the UFA (vertical leakage), and induced recharge from streams into the UFA. During the months of May-September 2011, doubling of irrigation pumping induced nearly double the recharge rate into the UFA from streams and effected a 10% decrease in discharge rate from the UFA to streams. Analysis of irrigation shutdown indicates that eliminating irrigation pumping from the Spring Creek watershed alone facilitated an increase in baseflow of 46 × 10 4 m 3 =day, or about two-thirds the total increase in baseflow that would be realized from eliminating irrigation pumping within the entire LFRB. © 2018 American Society of Civil Engineers.

Journal of Hydrologic Engineering

Sensitivity of groundwater components to irrigation withdrawals during droughts on agricultural-intensive karst aquifer in the Apalachicola-Chattahoochee-Flint River Basin