Mohamed Mansour | Ain Shams University (original) (raw)

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Papers by Mohamed Mansour

Geotechnical and Geological Engineering, 2021

This study investigates the behaviour of bored tunnels in the Port-Said very soft to firm clay de... more This study investigates the behaviour of bored tunnels in the Port-Said very soft to firm clay deposit in El-Tina Plain, north-eastern Egypt. Recent studies provided full characterization of the physical, mechanical and time-dependent properties of Port-Said Clay. This characterization enabled simulating its constitutive behaviour using the stress-dependent Modified Cam Clay model. The finite difference method is utilized to simulate the interaction between the tunnel and Port-Said Clay. The results are presented in terms of the pore water pressure regime, shear strain level, ground surface settlement and tunnel lining bending moment. The results show significant effect of the face and grouting pressures on the tunnel’s short and long-term behaviours. The term “reference hydrostatic pressure” is introduced to evaluate short-term face stability as a more practical and easy-to-quantify parameter compared to the conventional stability number. New empirical equations are developed to describe the long-term surface settlement trough (maximum settlement and trough width) in terms of the grouting pressure and tunnel diameter for tunnels in similar soft clay deposits.

HBRC Journal, 2018

Geotechnical design is carried out according to one of two main methods; the Working Stress Desig... more Geotechnical design is carried out according to one of two main methods; the Working Stress Design (WSD) and the Limit States Design (LSD) methods. The LSD can be carried out according to two main approaches; the Factored Strength Approach (FSA), and the Factored Resistance Approach (FRA). The use of LSD in Egypt is limited to the design of reinforced concrete structures. The geotechnical design is still based on the WSD method. The updated Egyptian Geotechnical Code will include both methods for a transition period before fully adopting the LSD. This study describes the methodology and results of determination of the partial factors for the limit states FSA for cantilever walls in dry cohesionless soils such that the LSD matches the WSD. These calibrated values are essential for the transition period when both the WSD and LSD design philosophies are applicable. The study recommends a partial factor of 1.25 in the future version of the Egyptian Code for the limit states FSA design of cantilever walls in dry cohesionless soils, which agrees with the current state of practice in different international codes.

Ain Shams Engineering Journal, 2018

Port-Said Clay is very soft to firm clay deposited in the delta of an old tributary of the Nile a... more Port-Said Clay is very soft to firm clay deposited in the delta of an old tributary of the Nile at the east of Port-Said, Egypt. Despite the detailed characterization carried out for Port-Said Clay, no tests were carried out to measure its seismic or small strain properties except for some measurements for clays in offshore Egypt. In this paper, the maximum shear modulus, modulus reduction ratio and damping ratio of Port-Said Clay are predicted by utilizing available measurements for clays in offshore Egypt and other similar soft clay deposits. These measurements, along with the characteristic properties of Port-Said Clay and well-established empirical correlations, are utilized in this study to recommend correlations and/or charts that predict the seismic and small strain properties of Port-Said Clay. The study also suggests a modification to some existing correlations and delivers the required parameters for seismic and small strain modeling of Port-Said Clay.

International Journal of Geotechnical Engineering, 2015

The serviceability of slopes after earthquakes becomes a design concern when footings are founded... more The serviceability of slopes after earthquakes becomes a design concern when footings are founded near the slope crest. The previous studies focused on the sliding block model and numerical analysis of particular slopes or landslides to account for the permanent post-earthquake deformation. In this paper, the post-earthquake deformation of dry sand slopes is calculated by numerical analysis utilizing the finite element method. An artificial earthquake time history is used as the source of the seismic excitation. Different slope heights, surface surcharges, and peak accelerations are investigated. The seismic waves' propagation through the soil mass is also investigated. The results are presented in the form of equations and charts that enable the design engineer to estimate the permanent seismic deformation of dry sand slopes, based on the slope height, the external surcharge, and peak crest acceleration (PCA). In addition, the safe setback distance for footings near slopes is recommended.

World Applied Sciences Journal

The permanent seismic deformation of highway embankments on a typical profile encountered in the ... more The permanent seismic deformation of highway embankments on a typical profile encountered in the northwestern zone of Egypt'sNile delta is investigated. An artificial earthquake acceleration-time history is used to define the input seismic motion. The permanent seismic deformation is calculated by two approaches. The first approach, the Dynamic Deformation Approach (DDA), redistributes the seismic shear stresses in excess of the static shear strength in order to calculate the permanent deformation using the finite element idealization. The second approach, Newmark Approach (NA), is based on Newmark sliding block model. The results show that the permanent seismic deformation is expected to reach 100 mm, which compares well with empirical methods. The DDA rigorously accounts for the development of local yield points, while NA necessitates that the total shear stresses along a potential sliding surface are greater than the available shear strength, in order to calculate permanent deformation.

Ain Shams Engineering Journal, 2016

Randomly distributed fiber reinforcement is used to provide an isotropic increase in the sand she... more Randomly distributed fiber reinforcement is used to provide an isotropic increase in the sand shear strength. The previous studies were not consistent regarding the fibers effect on the volumetric change behavior of fiber-reinforced sand. In this paper, direct shear tests are conducted on 108 specimens to investigate the effects of the fibers content, relative density, normal stress and moisture content on the shear strength and volumetric change behaviors of fiber-reinforced sand. The study investigates also the possibility of using dry fiber-reinforced sand as an alternative to heavily compacted unreinforced moist sand. The results indicate that the fibers inclusion increases the shear strength and dilation of sand. Moisture suppresses the fibers effect on the peak and postpeak shear strengths, and dilation. Dry loose fiber-reinforced sand achieves the same shear strength of heavily compacted unreinforced moist sand, yet at more than double the horizontal displacement.

International Journal of Geotechnical Engineering, 2014

Accurate prediction of soil parameters is a challenge to braced excavation systems design, especi... more Accurate prediction of soil parameters is a challenge to braced excavation systems design, especially when the wall retains ''Fill'' containing artificial materials. This paper presents a case study of a braced diaphragm in situ wall supporting 14 m of Fill in Egypt with the objective of estimating representative parameters for the Fill. The wall, designed based on conservative strength and deformation parameters, was monitored using inclinometers. Back analysis is conducted to determine representative Fill parameters using the beams on elastic foundation (BEF) and finite element (FE) methods. The FE analysis is conducted using the hardening soil constitutive model, and a comparison is made with Mohr-Coulomb (MC) model. The results show that the hardening soil model can reproduce the wall movement better than MC model and the BEF method. Hence, representative parameters are estimated for the retained Fill. It is illustrated that adopting the deduced values could result in considerable savings.

ABSTRACT Deep seated retrogressive earth slides along the walls of the Little Smoky River valley,... more ABSTRACT Deep seated retrogressive earth slides along the walls of the Little Smoky River valley, in northwestern Alberta, have lead to significant ongoing maintenance on Highway 49 for the past 50 years. While localized, higher velocity zones, have lead to site specific ...

Landslides, 2010

Abstract Facilities such as buildings, highways, railways, bridges, dams and pipelines often are ... more Abstract Facilities such as buildings, highways, railways, bridges, dams and pipelines often are built on natural slopes where the risk of landslides is not low. The vulnerability of these facilities to slow-moving slides has sometimes been underestimated, although the velocity ...