Mohmad Thakur

This study presents the findings of a GPR investigation at two archaeological sites in Vadnagar, India; Area 1: Gaon Tal near a Hindu Temple (23°47'19.57"N; 72°38'47.75"E) and Area 2: Baba No Tekdo locality II (23°47'30.53"N; 72°38'55.59"E). Area 1 was surveyed in two plots of dimensions 16m × 10m and 12m × 16m, and Area 2 in a single plot of size 40m × 36m. Total seventy-two profiles were taken using GSSI 3000 GPR system with an antenna of 200MHz frequency at a transect spacing of 2m in two orthogonal directions. Raw GPR data was processed using commercial software RADAN 7. The GPR results indicate stratification in both the areas which may be attributed to the change in soil layers or presence of a feature like brick platform. Part of Area 1 is also characterized by multiple reflections indicating the presence of metallic objects at shallow depth whereas Area 2 shows reflections characterizing wall-like features. It is pertinent to mention that the present study covers only a small area of potential sites of archaeological interest in Vadnagar.

The hydromechanical response of partially saturated soils at macroscale is a manifestation of fundamental physics associated with pore scale. The Soil Water Characteristic Curve (SWCC) is an important state variable which affects mechanical as well as transport properties in a multiphase porous media. In present work, X-ray CT imaging and Pore Morphology Method (PMM) are leveraged to demonstrate robustness of a predictive approach in enhancing understanding of multiphase flow in sands from a pore scale perspective. The 3D microstructure of the Ottawa sand assembly is obtained from attenuation contrast-based X-ray Computed Tomography (CT) which serves as an input to PMM-based predictions. PMM relies on Young Laplace equation and mathematical morphology to simulate drainage and imbibition processes on an actual pore space. This approach is computationally efficient in comparison to computational fluid dynamics approach where highly nonlinear Navier Stokes equation is solved on a compu...

Stress–strain and volume change behavior for clean sands which have distinct particle shape (rounded and angular) with very similar chemical (mineralogical) composition, size, and texture in one-dimensional (1D) compression and drained triaxial compression are presented. The effect of particle morphology on the crushing behavior in one-dimensional loading is explored using laser light diffraction technique which is suitable for particle crushing because of its high resolution and small specimen volume capability. Particle size distribution in both volume/mass and number distributions are considered for improved understanding associated with the process of comminution. Number distributions present a clearer picture of particle crushing. It is argued that particle crushing in granular assemblies initiates in larger particles, rather than in smaller particle. It was found that rounded sand specimens showed greater crushing than angular sand specimens with higher uniformity coefficient....

Stress–strain and volume change behavior for clean sands which have distinct particle shape (rounded and angular) with very similar chemical (mineralogical) composition, size, and texture in one-dimensional (1D) compression and drained triaxial compression are presented. The effect of particle morphology on the crushing behavior in one-dimensional loading is explored using laser light diffraction technique which is suitable for particle crushing because of its high resolution and small specimen volume capability. Particle size distribution in both volume/mass and number distributions are considered for improved understanding associated with the process of comminution. Number distributions present a clearer picture of particle crushing. It is argued that particle crushing in granular assemblies initiates in larger particles, rather than in smaller particle. It was found that rounded sand specimens showed greater crushing than angular sand specimens with higher uniformity coefficient. In 1D compression, loose specimens compress approximately 10% more than dense specimens irrespective of particle shape. Densification of angular sand results in improvement
in stiffness (approximately 40%) and is comparable to that of loose rounded sand. In general, density has a greater influence on the behavior of granular materials than particle morphology. The effect of particle shape was found to be greater in loose specimens than in dense specimens. The effect of grain shape on critical state friction angle is also quantified.

Because of the recent advancements in hardware and reconstruction algorithms, multiphase flow modeling in porous media is experiencing a shift toward using advanced imaging techniques such as X-ray computed tomography in conjunction with direct numerical simulations. This approach captures heterogeneities in soil samples utilized in laboratory testing and results in quick and less tedious predictions compared to the existing methods. In this paper, an experimental setup is developed specifically to validate numerical predictions of the soil water retention curve (SWRC) for two types of sands with identical size but distinct grain morphology of round (Ottawa sand) and angular particle shape (Q-Rok). The complex 3D pore network is captured noninvasively using high-resolution attenuation-based X-ray computed tomography. The numerical predictions are carried out by solving a Young-Laplace equation using the pore morphology method. The experimental results and numerical predictions match well, including the effect of hysteresis in SWRC measurements. The spatial distribution of pore water and pore air corresponding to different capillary suctions is obtained from numerical predictions, providing greater insights into the hydromechanical behavior of partially saturated soils. The sensitivity of the voxel size on simulations is quantified by predicting the pore size distribution of Ottawa sand at three different tomography resolutions.