Showing papers by "Jyant Kumar published in 2018"

Bearing capacity of foundations on rock mass using the method of characteristics

Abstract: The method of stress characteristics has been used for computing the ultimate bearing capacity of strip and circular footings placed on rock mass. The modified Hoek-and-Brown failure criterion has been used. Both smooth and rough footing-rock interfaces have been modeled. The bearing capacity has been expressed in terms of nondimensional factors N-sigma 0 and N-sigma, corresponding to rock mass with (1) =0 and (2) 0, respectively. The numerical results have been presented as a function of different input parameters needed to define the Hoek-and-Brown criterion. Slip line patterns and the pressure distribution along the footing base have also been examined. The results are found to compare generally well with the reported solutions.

Required Lining Pressure for the Stability of Twin Circular Tunnels in Soils

Abstract: In this study, the stability of twin circular tunnels in purely cohesive and cohesive-frictional soils was evaluated. It is assumed that the internal compressive normal pressure (σi) requir...

Upper-Bound Finite-Element Limit Analysis of Axisymmetric Problems for Mohr-Coulomb Materials Using Semidefinite Programming

Abstract: An upper-bound formulation for performing finite-element limit analysis by using semidefinite programming (SDP) for an axisymmetric stability problem involving the Mohr-Coulomb yield criterion has been presented. The SDP technique has an advantage in that it can deal with the yield criterion directly in its native form in terms of principal stresses and strains without any smoothing of the parent yield surface. The associated flow rule and plastic power dissipation are expressed entirely in terms of principal plastic strain rates. Nodal velocities and element plastic strain rates were framed as basic governing variables without involving stresses. The solution was obtained by using the SDP solver MOSEK in MATLAB. The problem of finding the bearing capacity of a circular footing was dealt with by choosing a planar domain that was discretized with (1)three-noded constant strain finite elements and (2)six-noded linear strain finite elements. The results were obtained with and without the provision of the velocity discontinuities, and were compared with those reported in literature. It was learned that quite accurate solutions can be obtained with the application of six-noded linear strain triangular elements and using velocity discontinuities along all the elements' interfaces.

Multimodal phase velocity-frequency dispersion images using different MASW transformation techniques

Abstract: Three different transformation techniques, namely, (i)w-c, (ii) w-k and (iii) tau-p, has been employed for generating multimodal dispersion images on the basis of multi-channel analysis of surface waves (MASW) data recorded in distance-time domain; here w= circular frequency, c = phase velocity, tau = time intercept, p = phase slowness (1/c) and k = wavenumber. All the three methods have been first clearly described. The results from these three different transforms have been examined by using synthetic as well as field data obtained from field tests using 48 geophones. The effect of sensor spread length (X) and geophone numbers (M) on multimodal dispersion images were examined. The solutions from these three transforms were found to match generally well with each other. The w-c transform has been noted to provide the most clarity since it does not require either high sampling rate as normally needed for the tau-p method or inclusion of the zero padding of the data in a distance domain for the w-k approach. The paper will be useful since it not only describes the methods, but it brings out simultaneously their merits in implementation and for generating the dispersion images.