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2021 | Buch

Advancements in Geotechnical Engineering

The official 2020 publications of the Soil-Structure Interaction Group in Egypt (SSIGE)


Über dieses Buch

This book intends directly the practical engineers, who will be of great interest in reading the interesting chapters. Earthwork projects are critical components in civil construction and often require detailed management techniques and unique solution methods to address failures. Being earthbound, earthwork is influenced by geomaterial properties at the onset of a project. Hence, an understanding of the in-situ soil properties and all geotechnical aspects is essential. Analytical methods for earth structures remain critical for researchers due to the mechanical complexity of the system. Striving for better earthwork project management, the geotechnical engineering community continues to find improved testing techniques for determining sensitive properties of soil and rock, including stress wave-based, non-destructive testing methods. To minimize failure during earthwork construction, past case studies and data may reveal useful lessons and information to improve project management and minimize economic losses.



SSIGE Official Publications 2020: Part 1

Assignment of Groundwater Table in Liquefaction Analysis of Soils
This paper discusses the issue and potential influences of miss-assignment of groundwater table in the analysis of soil liquefaction. In viewing that the groundwater table (\( \varvec{GWT}_{0} \)) during subsurface exploration or testing for evaluating cyclic resistance ratio (\( \varvec{CRR} \)) of soils is sometimes mistakenly assumed the same as the groundwater table (\( \varvec{GWT} \)) for computing cyclic stress ratio (\( \varvec{CSR} \)) due to seismic shaking, the results of liquefaction analysis may thus be erroneous. If the \( \varvec{GWT}_{0} \) is assigned higher than the actual level, the \( \varvec{CRR} \) and the associated factor of safety (\( \varvec{F}_{\varvec{L}} \)), would be overly predicted. Alternatively, if the \( \varvec{GWT}_{0} \) is assigned lower than its actual one, the \( \varvec{CRR} \) and \( \varvec{F}_{\varvec{L}} \) would be underestimated. If the groundwater table during exploration or testing is mistakenly assigned the same as the groundwater table for computing cyclic stress ratio (i.e., \( \varvec{GWT}_{0} = \varvec{GWT} \); or “one-groundwater-table, \( \varvec{OGT} \), scenario”), then the variation in the groundwater tables will lead to the changes in \( \varvec{CRR} \) and \( \varvec{CSR} \) in the same sense. Owing to different rates of change, however, the computed factor of safety (\( \varvec{F}_{\varvec{L}} = \varvec{CRR}/\varvec{CSR} \)), and the associated liquefaction potential index (\( \varvec{LPI} \)), may sometimes result in an unexpected situation. Namely, a rise in the groundwater tables would cause an unanticipated increase in the computed factor of safety and a decrease in the associated liquefaction potential index. Based on results of current study with assumption of \( \varvec{OGT} \) scenario, the \( \varvec{LPI} \) could be reduced by 10–30% if \( \varvec{GWT}_{0} \) is 3 m higher than the actual level; or alternatively, the \( \varvec{LPI} \) would be increased by 5–45% if \( \varvec{GWT}_{0} \) is 3 m lower than the actual one.
Muhsiung Chang, Mei-Shan Chan, Ren-Chung Huang, Togani C. Upomo, Rini Kusumawardani
Production Rate Estimation Using System Dynamics (Case Study: Clamshell Excavation at Top Down Construction)
Construction projects usually face delays and do not finish on time due to many factors, including inaccurate estimation of production rates. Production rate for an activity depends on many factors that are interdependent and stochastic in nature. However, most of the available models for production rate estimation assume deterministic factors and seldomly account for the interdependencies between the various factors. This research aims to provide accurate estimation of production rates through accounting for stochastic and interdependent factors. To this effect, this paper presents the modeling and testing of a System Dynamics (SD) model for excavation activities using clamshell in top-down construction projects. SD allows for representing the interdependencies between the various elements and sub-processes of the construction process. In addition, the SD simulation process allows for depicting the stochastic nature of the various parameters that other estimation techniques fail to achieve. To achieve the desired outcome, the authors: (1) carried out a thorough literature review to study the factors affecting the excavation process; (2) collected data through questionnaires and site reports to quantify the impact of each factor on production rate and its occurrence likelihood; (3) modeled the excavation process through SD toolkit on AnyLogic simulation platform; and (4) tested and validated the model through the case study. The model was able to provide results within a mean square error of 4.14% throughout the testing phase. Although the excavation process of top-down construction activities has a lot of complexity, the presented SD model has proved able to simulate the process and provide desired realistic production rates. The model can be improved to account for more factors, in order to capture the full nature of the excavation activity, nevertheless, the modeling approach can be replicated to estimate the production rates for other complex construction activities.
Ibrahim Hamdan, Mohamed S. Eid, Ahmed Elhakeem
Stepped Loading of a Raft Foundation Supported on Deep Soft Clay Improved with Floating Stone Columns
Soil improvement techniques are necessary in construction on weak soils such as soft clays and loose sands, as these weak deposits usually suffer from excessive settlement, and low bearing capacity. Stone columns are one of the most effective and economic systems to improve soils by alteration of soil in-situ properties through the installation of columns composed of granular material. Generally, stone columns are constructed to penetrate the soft soil layer and rest on deeper strong soils (known as end bearing stone columns). However, for deep soft clay layers, end bearing stone columns are not cost effective, in which case using floating stone column is a better solution. This paper includes a benchmark problem of loading a raft foundation of a tank rested on a deep soft clay layer improved using a group of floating stone columns. The 3D numerical program PLAXIS 3D was adopted to investigate the effect of raft loading technique on the final consolidation settlement value and time. Two loading techniques were used, the first is by filling the tank using staged loading technique (slow loading), and the second by filling the tank using an immediate loading technique (quick loading). This benchmark example provide an understanding of the performance of floating stone columns when loaded in a staged loading as compared to quick loading.
Khaled Hussein Elmeligi, Mamdouh A. Sabry, Waleed El-Sekelly
The Use of a Robotized Inclinometer System to Measure Deep-Seated Ground Deformation in a Monumental Area During TBM Tunnel Excavations. The Case of Rome Subway, New Line C
The new section T3 of Rome Metro network (line C) stretches in an important World Heritage area (Colosseo, Fori imperiali etc.). In order to monitor and assure the safety of this heritage, a very complex monitoring network has been installed to provide information on monuments status, on the effectiveness of the designer’s hypothesis and on the evolution of the TBM tunnel excavation. In cooperation with METROC S.c.p.A, General Contractor for planning and construction of the project, a robotized inclinometer system was experimentally installed with the aim of measuring the deep-seated ground deformations in three sections with different inclinometer tubes length. This equipment allows the measurement of deep horizontal displacements using a single inclinometer probe and a robotic system that automatically manage the probe for the entire length of the borehole with 50 cm step and double reading (0/180°). The experimental activity was carried out before, during and after the TBM excavation and allowed the monitoring of three sections at the Basilica of Santo Stefano Rotondo al Celio (62 m), Fori Imperiali (43 m and 33 m) with a frequency of measurement up to 6 measurements/day. The results showed interesting relations between TBM progress and horizontal deep deformations induced by tunnel excavation. These deformations, although very small, highlighted the potential of this instrumentation in terms of accuracy, vertical spatial resolution and very high frequency of measurements. This type of results can be useful to a more complete interpretation of the subsoil deformations and interaction between excavation and the surrounding built environment.
Paolo Allasia, Danilo Godone, Giorgio Pezzetti, Ivan Mammone, Eliano Romani
Seismic Site Response Characterization for Suez Canal Region, Egypt
The Suez Canal Economic Zone (SCZone) is a mega project in Egypt that was launched to increase the role of the Suez Canal region in international trading and to develop the urbanization of the region. The reliable assessment of seismic hazard is a crucial input information for the designer and planner of all projects in this area. In this study, an updated seismic hazard map for Suez Canal region that incorporates revised historical earthquake catalogs, morphostructural zonation data (MZ), revised focal mechanism solutions and mechanical models of the lithospheric structure is provided. This is done within the framework of the Neo-Deterministic Seismic Hazard Assessment (NDSHA) procedure that may efficiently incorporate earthquake source rupture data, geological information and any reliable new information to adequately compute the earthquake ground motion maps, like PGA, PGV and PGD. This methodology provides a comprehensive source of ground motion records (acceleration, velocity, displacement) for Egypt where a substantial challenge is posed by the lack of recorded data. To consistently assess the uncertainty of our understanding of the seismic hazard and its effect on critical structures a sensitivity analysis is performed varying, for example, (a) source focal mechanism, (b) directivity (c) rupture process and (d) seismotectonic model. Starting from the initial definition of the source, bedrock and site properties based on the available knowledge of the characteristics of the different earthquake scenarios and of the soil structural properties of the area deduced from the ambient noise array measurements, a set of ground shaking scenarios have been computed at the selected profile crossing the Suez Canal. Variations of the ground shaking scenarios are evaluated looking basically at: (a) the amplitudes measured on the waveforms and the response spectra, (b) the changes in the shaking duration and (c) the modifications in the amplification patterns. Finally, the seismic input (e.g. response spectra, time histories) at the tunnel site that undergoes the Suez Canal to connect Sinai peninsula with the western side of the country is provided.
Mohamed ElGabry, Hany M. Hassan, Franco Vaccari, Andrea Magrin, Fabio Romanelli, Guiliano Panza
Relationships of the Physical and Mechanical Properties Obtained in Ignimbrites from a Tunnel in Morelia, Mexico
Tunnel construction is important to reduce the length of the geometric road design as well as the environmental impact. However, its construction is one of the most complex challenges due to the variability of the geotechnical properties. Stability of the tunnels in rock can be compromised for the rock mass deterioration which can cause faults during and after construction. Deterioration rate depends on the rock properties together with the environmental factors. Rock deterioration predictions can be achieved by in situ explorations and by performing laboratory tests. One important test is the slake durability, since it considers wetting and drying cycles subjected to the material wastage. This paper is focused on determining and obtaining relationships of the durability of ignimbrites from Morelia, Mexico. The ignimbrite was obtained from one geotechnical borehole of 100 m of length on the axis of a road tunnel and the physical and mechanical properties of the ignimbrites were determined, hence the deterioration of the rocks. This last, was measured using five cycles instead of the two cycles considered in the Normative. Results obtained show that from the third cycle, a constant deterioration of the rock is observed impacting in the slake durability index (Id) and furthermore, it depends in the rock hardness. The Id after the fifth cycle (Id5) was associated to estimate the physical and mechanical properties of the ignimbrites. It was found that the increase in Id5 correlates with the increase in density, compressive strength, tensile strength, P-wave velocity and decrease in porosity and absorption.
Carlos Luz-Martínez, Eleazar Arreygue-Rocha, Luisa Equihua-Anguiano
Implementation of a Single Hardening Constitutive Model for 3D Analysis of Earth Dams
In the practice of geotechnical engineering, reliable information about soil properties are often available in terms of strength parameters but data on the deformability characteristics of the materials are known to a lesser extent. For situations where the analysis of soil resistance is a condition of the project, the traditional Mohr-Coulomb model is usually applied, but there are several other situations where the anticipated estimate of the level of deformations induced by the project is an essential engineering information. In this research the single hardening model proposed by Lade and Kim was implemented in the FLAC 3D finite difference program in order to investigate the three-dimensional geomechanical behavior of earth dams during the construction stage. Numerical analyses were carried out considering 2D and 3D models to study the influence of the intermediate stress on the geomechanical behavior of earth dams. The computed results were also compared with those obtained using the traditional Mohr-Coulomb model to put in evidence the advantages using the single hardening constitutive model when analyzing geotechnical problems.
Juan Huang, Celso Romanel
Geomembranes to Line Surge Shafts
Surge shafts are underground water structures that are usually lined. The lining provides stability and watertightness to the excavation line, avoiding that excessive water infiltration undermines the stability of the slopes and of the structure itself. Traditional lining systems have been reinforced or un-reinforced concrete and steel. The construction of concrete and steel linings is expensive and time consuming, it can be further complicated in locations with difficult access, and it may require expensive maintenance. Over time, or in presence of particularly difficult geological conditions, concrete linings deteriorate, water infiltrates into the soil through fissures, or/and failing joints and increased permeability, increased roughness results in reduced hydraulic efficiency. Similarly, steel liners may be stressed above their yielding point. Loss of watertightness can eventually trigger landslides and ultimately cause partial or total collapse of the structure. Waterproof geomembrane lining systems based on the use of thermoplastic materials can efficiently substitute traditional linings for rehabilitation as well as for new construction. They can be installed in short times, and are a permanent solution to provide watertightness, reduce head losses, and maintain the shaft in its design conditions. The high flexibility and elongation capability of the thermoplastic geomembrane allows bridging construction joints and existing cracks and accommodating the opening of new cracks. In case of difficult geology, a geomembrane system can increase the safety of the shaft by maintaining the watertightness for which it has been designed. The paper discusses the design concepts and components of drained geomembrane lining systems anchored by longitudinal fastening lines and by watertight perimeter seals, through case histories of surge shafts projects recently completed, one in South America and one in the middle East. In both projects the geomembrane system was installed on the existing concrete lining and left exposed to the water.
Alberto Scuero, Gabriella Vaschetti
Expanded Polystyrene in Soil Reinforcement
The design and execution of works on soft soils represent high complexity and challenges to geotechnicians, since these soils have low bearing capacity. Traditional construction methods require total or partial replacement of low resistance soil by soil with good bearing capacity; sometimes it is possible to construct lateral equilibrium berms; or to construct vertical drains that help accelerate the densification of the massif. These methods generally require large soil movements and require a lot of time to run, sometimes requiring areas for disposal and deposits. This work aims to study the use of the constructive method of lightweight embankments, which minimizes the impacts caused by traditional methods, by using expanded polystyrene (EPS) as the main component. The main focus of this work is the case study of the construction of a viaduct on top of embankment in EPS blocks in the municipality of Jundiaí, state of São Paulo, Brazil, comparing the method used with the traditional method of lateral equilibrium berms. During the visit to the work, already completed, presented in the case study, no pathologies were found, showing that the EPS method has potential for use.
David Carvalho, Roberto Kassouf, Pedro Scatena, Vilson Scatena
Future of Underground Techniques in Deep Mines of Different Content Without Catastrophic Risks
Self-organization is not a universal property of matter, it exists under certain internal and external conditions and this is not associated with a special class of substances. The study of the morphology and dynamics of migration of anomalous zones associated with increased stresses is of particular importance in the development of deep deposits, complicated by dynamic phenomena in the form of rock impacts. An important tool for this study is geophysical exploration. To describe the geological environment in the form of an array of rocks with its natural and technogenic heterogeneity, one should use its more adequate description, which is a discrete model of the medium in the form of a heterogeneous block medium with embedded heterogeneities of a lower rank than the block size. We have carried out an analysis of the morphology of the structural features of disintegration zones before a strong dynamic phenomenon. The constructed theory demonstrated how complicated the process of complexion methods using an electromagnetic and seismic field is to study the response of a medium with a hierarchical structure. This problem is inextricably linked with the formulation and solution of the inverse problem for the propagation of electromagnetic and seismic fields in such complex environments. Using the theory of solving the inverse problem, one can trace the migration of zones of abnormal stresses, their increase or decrease due to cyclic explosive influences during mining of the array, and also assess the possible risk of high-energy dynamic phenomena in the array. The most important conclusion consists on that fact: the monitoring system must be tuned to search the rock massif as a hierarchical structure. The catastrophic events are linked with the dynamics of the hierarchical inclusions state. For today we have sufficient knowledge to use these systems with mathematical software of predicting catastrophic events.
Olga Hachay, Oleg Khachay
Utilization of Silica Fume and Slag to Improve the Geotechnical Properties of Expansive Soil
Expansive soils are recognized as a problematic soil that imposes several challenges for civil engineers. Such soil undergo significant volume change in case of water penetrates into them, and they shrink as they lose moisture. Lightly-loaded engineering structures such as pavements, single story buildings, railways and walkways may experience severe damages when they are founded on such soils. Determination of expansive soils and quantifying their swelling potential and pressure caused by their expansion are essential in the application of geotechnical engineering practice. Therefore it is necessary to overcome problems associated with the swelling potential through introducing some other materials as an improvement aids.
The present study presents an experimental investigation of the swelling behavior of an expansive soil taken from Al-Andalos area at New Cairo, Egypt. Atterberg limits, Grain size distribution, Specific gravity, Optimum water content, maximum dry density, Swelling pressure, Free swell index (FSI) and swell potential of the soil were assessed. Based on the test results, soil sample classified as a highly clay percentage which leads to activity. Silica Fume and Slag were added to soil sample with ratios of 1%, 3%, 5%, 6%, 7% and 10% by dry weight of soil sample as an improvement and their effect on the geotechnical properties of tested soil were investigated.
The obtained test results were analyzed to establish the optimum percentage that can be added to improve the geotechnical properties of expansive soil in terms of swelling potential and unconfined compressive strength. Based on the obtained results, the treatment of the expansive soil with 5% of both Silica fume and Slag revealed better improvement with moderate swelling potential. Otherwise, the unconfined compressive strength should uncertainty trend depending on the shear parameter characteristics of both Silica fume and Slag.
Ahmed Hussien Zaki, Samir Gad, Mahmoud AbuBakr Alsedik
Effect of Sand Cushion Thickness and Lateral Extension on Heave of Remolded Swelling Soil
Swelling soil is one of the most common problematic soils. Swelling phenomenon can cause severe damage to the overlying lightly loaded structures. Many alternatives have been proposed to mitigate the effects of expansive soil on civil foundations such as pre-wetting, sub-drainage, hydraulic barriers, chemical stabilization, and mechanical treatments. Sand replacement is considered to be one of the most effective and practical techniques that can be utilized for the construction of safe foundations. Experimental study using a large-scale box model is used to investigate the effect of sand cushion on reduce the heave of the expansive soil. In addition, Parametric study was performed to assess the effect of sand cushion thickness and lateral extension on the heave of the footing. The results demonstrated that the use of sand cushion reduces the heave of the footing by increasing the thickness of the sand cushion. Moreover, the rate decrease for sand cushion thickness greater than two-thirds of the footing width. Thus, the optimum thickness of the sand cushion is 2/3 footing width. The footing heave decreases with increasing the lateral extension, Le, of sand cushion, and the rate of reduction of heave becomes negligible when using lateral extension greater than twice thickness of sand cushion.
G. E. Abdelrahman, Youssef Gomaa Youssef, A. E. Abdeltawab
Dynamic Response of Stabilized Soft Clay Under Cyclic Loading at Low Shear Strain Level
Grand construction projects all over Egypt require large infrastructure projects. In Northern Egypt where large buildings are needed for new developments, large areas of soft soils are abundant. These buildings transfer heavy static and dynamic loads to soil. Soft clays can be stabilized to carry these loads with minimum settlements and high shear strength. This research focuses on improving the static and dynamic properties of soft clay using chemical stabilization by cement or lime. undisturbed samples were collected from Belkas, Dakahleia – Egypt. The engineering properties were determined and classified as soft silty clay (CH). Low proportions of added cement or lime between 4 and 8% by weight were mixed with the natural samples, The effect on the strength and dynamic properties of reconstituted samples were investigated. Three series of a free-fixed type of resonant column tests were conducted in torsional mode on natural soft silty clay, stabilized soft silty clay with cement, and stabilized soft silty clay stabilized with lime. The influence of confining pressure and stabilizer amount on dynamic shear modulus (Gmax) and material damping (Dmin) for natural and treated samples were studied. The threshold shear strain γth for each treatment type is investigated at small-to-medium shear strain amplitude levels to investigate the effect of torsional shearing on material softening behavior and normalized shear modulus (G/Gmax) degradation of treated soil. The results are presented and discussed displaying percentages stabilizers that led to significant improvement in the soil stiffness and shear modulus using cement or lime as the stabilizers, The damping ratio, (Dmin) decreased by increasing stabilizers dosage.
Ahmed M. Karim, Osama M. Ibrahim, Mohamed I. Amer
Review of Soil Improvement Techniques
Foundation designers use deep foundation, when shallow foundation proved to have inadequate bearing capacity for the loading conditions, or the total and differential settlements are intolerable for the given structure. As an alternative approach, designers may consider one of the many soil improvement techniques to improve the geotechnical quality of the ground, i.e. bearing capacity and settlement characteristics. In choosing a soil improvement techniques, several factors should be considered including the suitability of the technique for the soil in place, the associate cost beside the durability and its performance over the year for the given load and geometry. These techniques may be used as a solution for problems in the ground for both existing and new constructions. However, there are several considerations, which engineers must examine before adopting any of these methods. This paper presents a review of the available soil improvement techniques, including their advantages, disadvantages/limitations, and provide applicability guide to practicing engineers for a given soil conditions and field applications. Design case study is presented proposing compaction grouting technique to overcome the collapse of bored piles. Selected field case studies from literature have been also presented using different soil improvement techniques explaining the improvement achieved from using each technique.
Mohamed Mamdouh Abdel-Rahman
Numerical Evaluation of Bearing Capacity of Step-Tapered Piles Using P-Y Curves Analysis
Step-tapered piles are those with a larger top diameter, and a smaller diameter at lower sections as the body gets slender stepwise from top to toe in one or some steps. This study aims to investigate the behaviour of step-tapered piles having only one step under axial loading condition. Three series of piles embedded in sand are examined numerically using the three-dimensional finite element method. Each set consists of five piles, including one reference straight sided wall pile and four step-tapered piles having the same volume. Different internal friction angles of 33°, 37°, 41° (to represent loose, medium and dense sands, respectively) and corresponding elastic modulus and lateral earth pressure coefficients are considered to observe their effect on the bearing capacity and settlement of piles. The load-displacement diagram of each pile is obtained, and accordingly, the frictional and end bearing resistances are calculated using conventional methods. A MATLAB code is developed to get the numerical data and carry out the calculations. Moreover, the normal and shear stress states, plastic points, and deformations around the step and toe of piles are computed and compared. According to the results, the advantages of step-tapered piles over their counterpart cylindrical ones in terms of bearing capacity and settlement are discussed. Finally, the optimum stepped length of the pile is determined.
Amin Shafaghat, Hadi Khabbaz
Using Traditional and Advanced Soil Improvement Techniques for Swelling Soil Heave Mitigation
Swelling soil is one of the most common problematic soils. The swelling phenomenon can cause severe damage to the overlying lightly loaded structures. Many alternatives have been proposed to mitigate the effects of expansive soil on civil foundations such as pre-wetting, sub-drainage, hydraulic barriers, chemical stabilization, and mechanical treatments. Sand replacement is considered to be one of the most effective and practical techniques that can be utilized for the construction of safe foundations. The sand cushion is used in this study as a traditional solution to reduce the heave of the expansive soil. On the other hand, the sand cushion reinforced with triaxial geogrid is used as an advanced solution. An experimental study using a large-scale box model is used to investigate the effect of sand cushion on reduces the heave of the expansive soil. Besides, a parametric study was performed to assess the effect of sand cushion thickness and lateral extension on the heave of the footing. Also, the effect of reinforcing sand cushion with triaxial geogrid was taken into consideration and studied the importance of using it in reducing of the swelling soil heave. The results demonstrated that the use of sand cushion reduces the heave of the footing by increasing the thickness of the sand cushion. Moreover, the reduction rate of heave decreases for sand cushion thickness greater than two-thirds of the footing width. Thus, the optimum thickness of the sand cushion is 2/3 footing width. The footing heave decreases with increasing the lateral extension, Le, of sand cushion, and the rate of reduction of heave becomes negligible when using lateral extension greater than twice thickness of sand cushion. Furthermore, it was concluded that using triaxial geogrid with sand cushion as a reinforcement element leads to reduce heave of the swelling soil due to the tension developed in geogrid. In addition, The maximum reduction percentage of the footing heave is equal to 53.77% when using sand cushion thickness is equal to the width of footing but, the minimum reduction percentage of heave is equal to 35.39% when using sand cushion thickness of 1/3B.
G. E. Abdelrahman, Y. G. Youssef, A. E. Abdeltawab
Advancements in Geotechnical Engineering
herausgegeben von
Dr. Hany Shehata
Prof. Dr. Mona Badr
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