Seismic Performance of Footings on Stone Columns Treated Dry Sand Beds

Priti Maheshwari,Nitish Kumar Yadav,Jagdish Prasad Sahoo 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.11

An extensive experimental study has been carried out to study the seismic performance of footings on stone columns treated dry sand beds. Physical models have been prepared in a laminar shear box of size 1 m3 on the shaking table which has a single degree of freedom motion for representing horizontal shaking action under seismic vibrations. Effect of the configuration of stone columns, aspect ratio of footing, relative density of sand bed, frequency and peak ground acceleration (PGA) of cyclic input motion on vertical settlement of footing has been studied. Optimum length of stone columns has been found to lie between 13 − 16 times the diameter. Direction of shaking perpendicular to length of footing has been found to be more critical. Effect of aspect ratio has been found to be more pronounced at larger PGA. Influence of the frequency on response of footings has also been quantified.

Combination of ammonium nitrate, cerium chloride and potassium chloride salts improves Agrobacterium tumefaciens-mediated transformation of Nicotiana tabacum

Maheshwari, Priti,Kovalchuk, Igor 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.2

The frequency of plant transformation can be improved by addition of various chemical into transformation media. In the past, we showed that exposure of tobacco, wheat and triticale explants to ammonium nitrate, cerium and lantanium chloride and potassium chloride resulted in an increase in the frequency of transformation. Here, we tested whether a combination of increased concentrations of the aforementioned salts yielded a higher transformation frequency. We found that exposure to 61.8 mM ammonium nitrate caused a 5.0-fold increase in transformation frequency, whereas exposure to 1.0 ${\mu}M$ cerium chloride or 47.0 mM potassium chloride resulted in 1.2- and 2-fold increases, respectively. Exposure to 61.8 mM ammonium nitrate and 1.0 ${\mu}M$ cerium chloride led to a 4.8-fold increase in transformation frequency, whereas exposure to 61.8 mM ammonium nitrate and 47.0 mM potassium chloride let to a 5.2-fold increase. Finally, exposure to 61.8 mM ammonium nitrate, 1.0 ${\mu}M$ cerium chloride and 47.0 mM potassium chloride produced a 5.1-fold increase. The analysis of the intactness of T-DNA borders showed that plants exposed to ammonium nitrate and a combination of ammonium nitrate with other salts had the more intact right borders and the less intact left borders. The best results were observed when all three salts (ammonium nitrate, potassium chloride and cerium chloride) were used. Thus, we concluded that the addition of cerium chloride and potassium chloride does not substantially improve the transformation rate beyond the improvement observed upon treatment with 61.8 mM ammonium nitrate, but may slightly improve the intactness of T-DNA borders.

Influence of inclusion of geosynthetic layer on response of combined footings on stone column reinforced earth beds

Maheshwari, Priti,Khatri, Shubha Techno-Press 2012 Geomechanics & engineering Vol.4 No.4

The present paper deals with the analysis of combined footings resting on geosynthetic reinforced granular fill overlying stone column improved poor soil. An attempt has been made to study the influence of inclusion of geosynthetic layer on the deflection of the footing. The footing has been idealized as a beam having finite flexural rigidity. Granular fill layer has been represented by Pasternak shear layer and stone columns and poor soil have been represented by nonlinear Winkler springs. Nonlinear behavior of granular fill layer, stone columns and the poor soil has been considered by means of hyperbolic stress strain relationships. Governing differential equations for the soil-foundation system have been derived and solution has been obtained employing finite difference scheme by means of iterative Gauss Elimination method. Results of a detailed parametric study have been presented, for a footing supporting typically five columns, in non-dimensional form in respect of deflection with and without geosynthetic inclusion. Geosynthetic layer has been found to significantly reduce the deflection of the footing which has been quantified by means of parametric study.

Double Beam Model for Reinforced Tensionless Foundations under Moving Loads

Shashank Bhatra,Priti Maheshwari 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4

An attempt is made herein to analyse the rails resting on earth beds with geocell inclusion under a moving load. Reinforced soil system is assumed to react to compressive forces only, i.e., the tensionless foundation. It comprises of a granular fill layer (modelled as Pasternak shear layer) followed by a geocell inclusion (represented by an infinite beam with finite bending stiffness) overlying the foundation soil (modelled as a series of spring and dashpot connected in parallel). The governing differential equations are developed and converted for general use in non-dimensional form. These equations are solved using suitable boundary conditions and employing Finite Difference Scheme along with iterative Gauss-Seidel technique. Critical velocity of tensionless system is determined and compared with perfect contact case. The parametric study conducted shows the influence of applied load, relative compressibility of soils, relative flexural rigidity, depth of placement of geocell, damping in the system and velocity of load on the response of rail and geocell reinforcement. Also, a sensitivity study is carried out which suggests that uplift of the rail is quite sensitive to more number of parameters than to its downward deflection.

Combination of ammonium nitrate, cerium chloride and potassium chloride salts improves Agrobacterium tumefaciens-mediated transformation of Nicotiana tabacum

Igor Kovalchuk,Priti Maheshwari 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.2

The frequency of plant transformation can beimproved by addition of various chemical into transformationmedia. In the past, we showed that exposure oftobacco, wheat and triticale explants to ammonium nitrate,cerium and lantanium chloride and potassium chlorideresulted in an increase in the frequency of transformation. Here, we tested whether a combination of increased concentrationsof the aforementioned salts yielded a highertransformation frequency. We found that exposure to61.8 mM ammonium nitrate caused a 5.0-fold increase intransformation frequency, whereas exposure to 1.0 lMcerium chloride or 47.0 mM potassium chloride resulted in1.2- and 2-fold increases, respectively. Exposure to61.8 mM ammonium nitrate and 1.0 lM cerium chlorideled to a 4.8-fold increase in transformation frequency,whereas exposure to 61.8 mM ammonium nitrate and47.0 mM potassium chloride let to a 5.2-fold increase. Finally, exposure to 61.8 mM ammonium nitrate, 1.0 lMcerium chloride and 47.0 mM potassium chloride produceda 5.1-fold increase. The analysis of the intactness ofT-DNA borders showed that plants exposed to ammoniumnitrate and a combination of ammonium nitrate with othersalts had the more intact right borders and the less intactleft borders. The best results were observed when all threesalts (ammonium nitrate, potassium chloride and ceriumchloride) were used. Thus, we concluded that the additionof cerium chloride and potassium chloride does not substantiallyimprove the transformation rate beyond theimprovement observed upon treatment with 61.8 mMammonium nitrate, but may slightly improve the intactnessof T-DNA borders.

Stochastic Analysis of Strip Footings on Elastic Layered Soil

P. Pradeep Kumar,Priti Maheshwari 대한토목학회 2013 KSCE Journal of Civil Engineering Vol.17 No.7

In the present work, Monte Carlo simulation assisted analysis of strip footings resting on elastic layered soil has been carried out. The elastic modulii of soil layers have been treated as a stationary stochastic field characterized by mean, variance, Autocorrelation Function (ACF) and the Autocorrelation Distance (ACD). Realizations of elastic modulii (E), generated by solving a stochastic differential equation, have been fed to a deterministic distributed parameter model to generate realizations of dependent stochastic fields viz. settlement of footing and interfacial vertical stresses. Subsequently these realizations have been analyzed to evolve probability distribution functions, variance and ACF of the dependent stochastic fields. It is revealed that ACF of these fields are independent of the ACF of E. The variance of settlement has been found to increase as the ACD of E increases, implying requirement of a larger factor of safety when random soils display low frequency (macro level) variations. On the other hand variance of the vertical stress is larger at smaller ACD of E, indicating that for vertical stress, larger factor of safety is required when the random soils display high frequency (micro level) variations.