أحمد كحيل

Study of the Effects of High Strain Rate Loading on Underground Structures. Underground tunnels are indivisible part of the modern civil infrastructure. The functionality of these underground facilities might be affected under the application of Blast Loadings. Apart from the preventive measures which should be undertaken to significantly reduce the possibility of explosion occurrence, it is very important to understanding the response of tunnel-soil system when subjected to blast loads. Due to the fact that the experimental determination of the response of underground tunnels under blast loading is difficult due to its unavailability. Then, an advanced numerical analysis of tunnels subjected to blast loading is the desired approach. The primary aims of this study was to investigate the response of an embedded tunnel under the application of surface blast loadings, that’s first. The second aim was to investigate the behavior of the soil under the high straining rates using strain rate dependent constitutive model. Blast loads result from explosives detonations typically produce very high strain rates ranging between [102 – 104] s-1. Soil behavior under the blast loading induced high strain rates is a dominant factor must be investigated and properly considered. The Cowper-Symonds “Power Law” constitutive model will be incorporated as the strain rate dependent constitutive model to account for the high strain rates, where the Cowper-Symonds Coefficient Parameters [D & P] will be identified through a series of High Strain Rate Testing using the Split Hopkinson Pressure Bar (SHPB) Tests. An advanced Finite element simulation of Tunnel-Soil system subjected to blast load was performed using (Abaqus/Explicit) incorprating the “Smoothed Particles Hydrodynamics technique (SPH)” to account for the high deformations resulted from blast loads application. The blast load was modeled using the CONWEP Model. The simulation was done in two conditions, the first one considered the soil as a strain rate independent, while the second one considered the soil strain rate dependency through using the Cowper-Symonds Power Law incorporated in the Drucker-Prager Constitutive Model. The analysis results agree to a great extent with the data reported in the literature, regarding the increase of the soil strength at higher strain rates. The analysis results show a significant reduction in the influence of the blast load induced straining actions while using the clay strain rate dependent parameters. The clay soil showed higher strength, and thus, the effect of the blast load on the tunnel structure was reduced significantly.

o Advanced studies in the theoretical soil mechanics & hydraulics, rock mechanics, soil lab testing & soil field testing techniques. o Applied soil mechanics highlighting the shallow foundations, deep foundations & geo-synthetics in geotechnical engineering. o Intense study concerning piles design according to different codes of practice, piles testing and tests evaluations methods. o Diploma project was the stability analysis & design of temporary shoring system using top-down construction technique.

Graduation Project: Structural Analysis Project; Graduation Project Grade: Excellent I. High Rise Building Unit o It was required to undertake the structural analysis using one software program & one manual method, the structural analysis was undertaken using 2 software programs and 5 manual methods. o It was required to design all the structural members and produce all the drawing with all calculations. II.Bridge Unit o It was required to structurally analyze the bridge using sap2000 and produce all the drawing and calculations. III. Rehabilitation Unit o It was required to re strengthen an industrial building under additional loads using FRPs (Reinforced Fiber Polymers)