Civil Engineering

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Mumbai city is the financial capital of India and is fifth most densely populated city in the world. Seismic soil liquefaction is evaluated for Mumbai city in terms of the factors of safety against liquefaction (FS) along the depths of soil profiles for different earthquakes with 2% probability of exceedance in 50 yr using standard penetration test (SPT)-based simplified empirical procedure. This liquefaction potential is evaluated at 142 representative sites in the city using the borehole records from standard penetration tests. Liquefaction potential index (LPI) is evaluated at each borehole location from the obtained factors of safety (FS) to predict the potential of liquefaction to cause damage at the surface level at the site of interest. Spatial distribution of soil liquefaction potential is presented in the form of contour maps of LPI values. As the majority of the sites in the city are of reclaimed land, the vulnerability of liquefaction is observed to be very high at many places. ©2012 Author(s).

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Natural Hazards and Earth System Science

Assessment of liquefaction potential index for Mumbai city

A method based on the application of Kötter's equation is proposed to evaluate active earth pressure on an inclined wall retaining horizontal cohesionless backfill with uniform surcharge. This method considers only the effect of surcharge for the analysis. It is successfully used to evaluate the magnitude and point of application of reaction on the failure surface. The coefficient of active earth pressure and point of application of the active thrust are computed for different combinations of soil and wall properties and the results are presented in dimensionless forms. A fairly good comparison is seen with the available solutions.

Electronic Journal of Geotechnical Engineering

Active earth pressure on an inclined wall with horizontal cohesionless backfill due to surcharge effect

Mumbai city is the economical capital of India and is situated about midway on the western coast of stable continental region of Peninsular India. Major part of the city being of reclaimed land, the soil type is of alluvium, sand, and recent conglomerate. There are some bigger water bodies within the city range. In this study, an attempt has been made to study the susceptibility of soil liquefaction using simplified empirical procedure based on number of blow counts (N values) of the soil layers from standard penetration test. The liquefaction susceptibility is quantified in terms of factor of safety along the borehole depths at available borehole locations using earthquake-induced cyclic stress on the soil and the cyclic resistance of the soil to withstand the load. The factor of safety against liquefaction is evaluated at different sites for two peak ground acceleration (PGA) levels pertaining to 10 and 2 % probability of exceedance in 50 years corresponding to uniform hazard response spectra for Mumbai city with 475- and 2,475-year return period, respectively. Contour maps are prepared that display the factor of safety at different depths for earthquake magnitude of M w 6.5. These contour maps show the liquefaction vulnerability at different sites in the city. © 2012 Springer Science+Business Media B.V.

Natural Hazards

Soil liquefaction studies at Mumbai city

In recent years, spillway rehabilitation has increased in importance and become the subject of many projects worldwide. One solution for this problem is the implementation of a new type of labyrinth spillway, called Piano Key Weir (PK-Weir ). This is an excellent alternative for increasing the overflow capacity of existing dams. Similarly to traditional labyrinth weirs, the hydraulic capacity of a PK-Weir is a function of its geometrical characteristics. Currently, there is a lack of systematic experiments, and the existing data does not allow the proposition of a universal design procedure. This paper reviews the previous studies on the efficiency of planned and built PK-Weirs. The results are evaluated by comparing an actual PK-Weir's discharge to that theoretically obtained for a sharp-crested spillway with crest length equal to the width of the PK-Weir for a given hydraulic head. On the basis of this evaluation, a preliminary design procedure is proposed. © 2012 American Society of Civil Engineers.

Center for Environmental Sciences & Engineering

Journal of Hydraulic Engineering

Discharge capacity of piano key weirs

This article deals with the effect of adhesive bond on piezoelectric ceramic (PZT) patch-structure interaction system and the resulting effect on admittance signature, which has a major impact on the electromechanical coupled phenomena pertinent for the electro-mechanical impedance technique. The adhesive bond acts as an elastic medium which facilitates the transfer of stresses and strains developed due to piezo displacement and also couples the impedance of PZT patch with that of the host structure. In this work, the force transfer mechanism is studied along the length of the PZT patch as also the variation of the shear stress and strain along the bond. This article presents a numerical approach to study the inclusion of shear lag in the electro-mechanical impedance model through commercially available finite element (FE) simulation software. The results are compared with existing analytical as well as experimental data. Parametric study of the FE shear lag model is carried out to examine the effect of piezo-mechanical parameters on the admittance signature.

Current Science

Numerical investigations of shear lag effect on PZT-structure interaction: Review and application

The free field surface motion during an earthquake is governed by the characteristics of strong ground motions and the dynamic soil properties at a particular site. The soft soil deposits aggravate the seismic hazard due to the amplification of ground motion at some intensity level. In this article, seismic site response analysis is used to estimate the spatial distribution of surface level free field ground motion at Mumbai city due to multiple suites of input earthquake ground motions, scaled to conform to the target rock level uniform hazard response spectrum with minimum mean squared error. Free-field surface motion is found to be influenced by the softness of soil site and intensity of ground motion. Surface level free field motion due to excitation at bedrock level at each site is quantified in terms of spectral acceleration. Acceleration response spectra at selected natural periods and corresponding standard errors are computed and the results are presented in the form of contour maps. The spatial distribution of ground motion obtained in the form of contour maps will be useful in finding seismic coefficients to determine the design seismic forces and in identifying vulnerable places in Mumbai city. © 2011 ejge.

Spatial distribution of surface level free field motion at Mumbai city

<p>Piano Key Weirs are modified version of labyrinth weir with innovation to improve discharging capacity and more compatible for constructing on a existing or new spillway with lesser space requirement and structural stability. The objective of this study was to identify the Piano Key Weir in which the maximum discharge capacity at different UW with p (height of weir) could be achieved. To achieve this for different flow conditions, length magnification ratio (L/W) is taken from 3.56 to 7.40. Also, other parameters are taken in different combinations for getting optimum configuration of Piano Key Weir for better performance. With this in view, three phases of experimental campaign on eighteen Piano Key Weir models are reported in this paper. The ratio (r) of Piano Key Weir to linear weir discharge for a given head was seen to be more than one and found to increase with magnification ratio L/W upto a certain limit of h/p ratio. It was also found that performance of ratio of inlet and outlet cell width was best when two cells were of same width. The analysis of discharge coefficient variation is correlated with h/p. © 2011 Taylor &amp; Francis Group, LLC.</p>

ISH Journal of Hydraulic Engineering

Experimental study of hydraulically efficient piano key weir configuration

The Industrial Source Complex Short Term (ISCST3) model was used to discern the sources responsible for high PM10 levels in Kanpur City, a typical urban area in the Ganga basin, India. A systematic geographic information system-based emission inventory was developed for PM10 in each of 85 grids of 2×2 km. The total emission of PM10 was estimated at 11 t day-1 with an overall breakup as follows: (a) industrial point sources, 2.9 t day-1 (26%); (b) vehicles, 2.3 t day-1 (21%); (c) domestic fuel burning, 2.1 t day-1 (19%); (d) paved and unpaved road dust, 1.6 t day-1 (15%); and the rest as other sources. To validate the ISCST3 model and to assess air-quality status, sampling was done in summer and winter at seven sampling sites for over 85 days; PM10 levels were very high (89-632 μg m-3). The results show that the model-predicted concentrations are in good agreement with observed values, and the model performance was found satisfactory. The validated model was run for each source on each day of sampling. The overall source contribution to ambient air pollution was as follows: vehicular traffic (16%), domestic fuel uses (16%), paved and unpaved road dust (14%), and industries (7%). Interestingly, the largest point source (coal-based power plant) did not contribute significantly to ambient air pollution. The reason might be due to release of pollutant at high stack height. The ISCST3 model was shown to produce source apportionment results like receptor modeling that could generate source apportionment results at any desired time and space resolution. © Springer Science+Business Media B.V. 2010.

Water, Air, and Soil Pollution

GIS-based emission inventory, dispersion modeling, and assessment for source contributions of particulate matter in an urban environment

In this article, stochastic finite-fault simulation combined with site response analysis is used to understand the spatial distribution of ground motion in Guwahati city due to three damaging earthquakes. The rock level ground motion for the scenario earthquakes is generated based on the stochastic finite-fault methodology. These simulated motions are further amplified up to the surface by equivalent linear site response analyses using the available borelog data at 100 different locations in Guwahati city. A set of twenty simulated rock level time histories for each event, are used to compute the surface level ground motion. Response spectra are computed and the results are presented in the form of contour maps, at selected natural periods. The mean amplification due to local soil deposit is as high as 2.2 at most of the sites in Guwahati city. Based on these simulated motions, an average site correction factor is obtained for soil sites in Guwahati city. The standard error in the simulated response spectra is also reported. The contour maps obtained will be useful in identifying vulnerable places in Guwahati city.

Acta Geodaetica et Geophysica Hungarica

Ground motion for scenario earthquakes at Guwahati city

We have examined the interactions of gaseous pollutants and primary aerosols that can produce secondary inorganic aerosols. The specific objective was to estimate degradation rates of precursor gases (NH3, NO2 and SO2) responsible for formation of secondary inorganic aerosols. A Teflon-based outdoor environmental chamber facility (volume 12.5m3) was built and checked for wall losses, leaks, solar transparency and ability to simulate photochemical reactions. The chamber was equipped with state-of-the-art instrumentation to monitor concentration-time profiles of precursor gases, ozone, and aerosol. A total of 14 experimental runs were carried out for estimating the degradation of precursor gases. The following initial conditions were maintained in the chamber: NO2=246±104ppb(v), NH3=548±83ppb(v), SO2=238±107ppb(v), O3=50±11ppb(v), PM2.5 aerosol=283438±60524 No./litre. The concentration-time profile of gases followed first-order decay and were used for estimating degradation rates (NO2=0.26±0.15h-1, SO2=0.31±0.17h-1, NH3=0.35±0.21h-1). We observed that degradation rates showed a statistical significant positive correlation (at 5% level of significance) with the initial PM2.5 levels in the chamber (coefficient of correlation: 0.63 for NO2; 0.62 for NH3 and 0.51 for SO2), suggesting that the existing surface of the aerosol could play a significant role in degradation of precursor gases. One or more gaseous species can be adsorbed on to the existing particles and these may undergo heterogeneous or homogeneous chemical transformation to produce secondary inorganic aerosols. Through correlation analysis, we have observed that degradation rates of precursor gases were dependent on initial molar ratio of (NH3)/(NO2+SO2), indicative of ammonia-rich and ammonia-poor situations for eventual production of ammonium salts. © 2011 Elsevier Ltd.