Selected Research Projects:

Software Development for Geo-Engineers

Over the years (especially after finishing PhD degree) I have been active in developing and extending the computational capabilities of educational numerical codes (non-commertial). The combined knowledge of geomechanical engineering and computer programming has enabled me to develop generic, useful free programs for researchers, students and practicing engineers. These free engineering programs have been currently used worldwide assisting students, researchers and engineers. The list of developed free programs is available in Demos & Codes page.

Seismic Earth Pressure on Retaining Structures

An investigation was made to experimentally and analytically study the seismically induced earth pressure on non-displacing and displacing cantilever structures as well as basement walls retaining a cohesionless soil backfill and subjected to earthquake-type dynamic excitations using the centrifuge modelling technique. 4 series of centrifuge tests have been conducted as a part of PhD research program under advisory of Prof. Nicholas Sitar. Further information about this project can be found at NEEShub web page. This work was performed with funding from NSF-NEES-CR Grant No. CMMI-0936376: Seismic Earth Pressures on Retaining Structures through collaborative project Between University of California, Berkeley and Itasca Consulting Group Inc. Programs FLAC2D and FLAC3D were generously made available by Itasca Consulting Group Inc. under collaborative research agreements.

Explicit Three Dimensional Discontinuous Deformation Analysis for Blocky System

This work presents a 3D-DDA formulation that uses an explicit time integration procedure and an efficient contact detection algorithm optimized to minimize the computational effort. The advantages of the explicit formulation are that the global stiffness matrix does not need to be assembled and the linear equations do not need to be solved by matrix inversion. Consequently, the computational effort and memory requirement can be reduced considerably, which is important for efficient solution of large 3D problems. The contacts between the blocks are detected by using Fast Common-Plane (FCP) approach. The halfedge (HE) data structure approach is used to handle the navigation into the topological information associated with polyherdral objects (vertices, edges, faces). The halfedge data structure allows for quick traversal between faces, edges, and vertices due to the explicitly linked structure of the network.

3D Simulation of Tsunami Wave Induced by Rock Slope Failure using Coupled DDA-SPH

We present a three dimensional fluid-structure coupling between SPH and 3D-DDA for modelling rock-fluid interactions. The Navier-Stokes equation is simulated using the SPH method and the motions of the blocks are tracked by a Lagrangian algorithm based on a newly developed, explicit, 3D-DDA formulation. The coupled model is employed to investigate the water entry of a sliding block and the resulting wave(s). The coupled SPH-DDA algorithm provides a promising computational tool to for modelling a variety of solid-fluid interaction problems in many potential applications in hydraulics, rock mass stability, and in coastal and offshore engineering.

3D Fly-Through Animation for Geotechnical Projects

This clip presents the 3D fly-through animation for complex underground structures. A matlab code has been developed to extract the images from well know geotechnical program so called FLAC3D and then Windows Movie Maker has been used to bind the frames and create the movie clip.

Fully Grouted Cable bolt Modelling

Numerical procedure based on explicit finite element method (FEM) for the analysis of fully grouted rock bolt and rock mass interactions are introduced in this work. The finite element procedure incorporates elasto-plastic concepts with Mohr-Coulomb yield criterion and has been applied for rock mass. Rock bolt behaviour are evaluated based on finite elemenet method and are embedded in the elasto-plastic procedures of explicit FEM.

Development of Constitutive Model for Rock and Soil

This project presents a plastic stress update algorithm for the exact generalized Hoek-Brown criterion (modhb) including the apex and corner singularities. This new methodology has been implemented to the 2D and 3D finite difference code FLAC and FLAC3D, via their User-Defined-Model capability. The model builds on the constitutive efforts of Johan Clausen and Lars Damkilde. The plastic flow rule is taken to be non-associated with a plastic potential which are similar to the yield criterion. Perfect plasticity and isotropic linear elasticity are assumed. The stress update algorithm belongs to the class of algorithms termed return mapping, backward Euler or implicit integration. This work was performed with funding from NSF-NEES-CR Grant No. CMMI-0936376: Seismic Earth Pressures on Retaining Structures through collaborative project Between University of California, Berkeley and Itasca Consulting Group Inc. Programs FLAC2D and FLAC3D were generously made available by Itasca Consulting Group Inc. under collaborative research agreements.

The user can access to "modhb" constitutive model on Itasca-UDM web site.

New Developments for Opensees

As a part of PhD research project couple of new elements have been added into the Open Source for Earthquake Engineering and Simulation (OpenSees) program as listed below:

1- Implementing Node-to-Segment (NTS) frictional contact element (ZeroLengthContactNTS2D, ZeroLengthInterface2D).

2- Implementing a constant strain triangular element (Tri31).

Particle-Based Discontinuous Deformation Analysis

This work presents a 3D-DDA formulation that uses an explicit time integration procedure and an efficient contact detection algorithm optimized to minimize the computational effort. The advantages of the explicit formulation are that the global stiffness matrix does not need to be assembled and the linear equations do not need to be solved by matrix inversion. Consequently, the computational effort and memory requirement can be reduced considerably, which is important for efficient solution of large 3D problems. In addition, the computational efficiency is increased by eliminating unnecessary contact computations using a grid based nearest neighbor search. The contacts between the blocks are detected by using Fast Common-Plane (FCP) approach. The halfedge (HE) data structure approach is used to handle the navigation into the topological information associated with polyherdral objects (vertices, edges, faces).

Modelling Fluid Flow using Smoothed Particle Hydrodynamics

I have implemented a fluid flow simulation using the smoothed particle hydrodynamics (SPH) method.