Evaluation of Lateral and Axial Deformation for Earth Pressure Balance (EPB) Tunnel Construction Using 3 Dimension Finite Element Method

Mass Rapid Transit Jakarta (MRTJ) phase 1 tunnel construction using the earth pressure balance method has been completed and surface settlement and lateral displacement data according to elevation and inclinometer readings has been collected to evaluate the effect of tunnel’s construction on surrounding infrastructure. Soil stratification along the research area, defined according to boring logs and soil parameters for the hardening soil model (HSM) and the soft soil model (SSM), was determined by optimization of stress-strain curve fitting between CU triaxial test, consolidation test and soil test models in the Plaxis 3D software. Evaluation of the result of surface settlement measurements using an automatic digital level combined with geodetic GPS for elevation and position control points showed that the displacement behavior was affected by vehicle load and stiffness of the pavement. Lateral displacement measurements using inclinometers give a more accurate result since they are placed on the soil and external influences are smaller than surface settlement measurement. The result of 3D finite element modeling showed that surface settlement and lateral displacement during TBM construction can be predicted using HSM with 2% contraction. SSM and the closed-form solutions of Loganathan and Poulos are unable to provide a good result compared to the actual displacement from measurements

Settlement prediction of a group of lightweight aggregate (LECA) columns using finite element modelling

The method of reinforcing the soft clays with stone columns is the most commonly adopted technique to enhance its load carrying capacity and to reduce settlements. Their performance with respect to bearing capacity is well researched, but the understanding of settlement characteristics still requires extensive investigations. Moreover, no studies have been made to explore the effectiveness of stone columns using Lightweight Expanded Clay Aggregate (LECA) as filler material replacing normal stone/aggregates in order to improve settlement behavior of soft clay. LECA is known as a common lightweight material that have been applied successfully in civil engineering works where weight is an issue because the materials can help to reduce dead loads and lateral forces by more than half in installations over structures and those with soft soils. The purpose of this work is to assess the suitability of reinforcing technique by LECA columns to improve the settlement through finite element. The analysis of performance of LECA column in soft soil improvement was conducted through finite elements methods by using Plaxis 3D commercial software. Based on the results the settlement ratio was reduced as the column length increased until unity at end bearing condition where β = 1.0. It is also observed that bulging was reduced with closer spacing between LECA columns

Enhancing the bearing capacity of rigid footing using limited life kenaf geotextile reinforcement

This research focuses on soft clay improvement by using Kenaf textile as a natural geotextile reinforcement. A series of small-scale laboratory tests were conducted to study the impact of the geotextile reinforcement depth, d, the vertical spacing between reinforcement, S and the number of reinfor- cement layers, N on the bearing capacity of the soil model. The test results were verified using the numerical simulation by PLAXIS 2D. In this study, the influence factors included four different d/B ratios of 0.25, 0.5, 0.75 and 1.0; three different S/B ratios of 0.25, 0.5 and 0.75, and a different number of reinforcement layers, N from 1 to 4 were investigated where B is the footing width. The results clearly showed that the bearing capacity of rigid footings was significantly improved with the Kenaf geotextile layers in the kaolin. The measured and predicted bearing capacity results were in good agreement. The optimum d/B ratio and S/B ratio, which resulted in the maximum ultimate bearing capacity of the Kenaf-reinforced model ground were about 0.25 and 0.25, respectively. The optimum N was 3, i.e., the bearing capacity insignificantly improved even with N > 3

Numerical modeling of centrifuge test procedure for different embankment cases

Physical modelling through full-scale and small-scale models is widely implemented in order to define specific aspects of the prototype behaviour. On the other hand, numerical modeling is essentially required to cope with the complex geotechnical problems due to the ability of considering and analyzing all aspects of the model and can afford more perception about the behavior of structures such as geosynthetic-reinforced embankments. In this study, four different cases of unreinforced and reinforced embankment models constructed on soft and stiff grounds were studied. Small-scale physical modelling by means of centrifuge tests and numerical modelling by means of finite element simulations were performed. As the small-scale model was rotated in different acceleration fields during the centrifuge test, the dimensions of the centrifugal model were different from the original state of the prototype in different stages of the test. This paper focused on developing a finite element simulation based on the dimensions of a centrifugal model in different incremental acceleration fields applied during the stages of the test. Comparing the results of finite element simulations with the measurements of the centrifuge tests showed a good agreement between the two methods, which verified the reasonableness of the finite element models in analysis of embankments based on small-scale centrifugal dimensions. Moreover, the results showed the different deformation behaviour for embankments on soft and stiff grounds and indicated the significant effect of the geosyntheic reinforcement on increasing the stability of the embankment on soft ground

NUMERICAL MODELING OF CENTRIFUGE TEST PROCEDURE FOR DIFFERENT EMBANKMENT CASES

ABSTRACT: Physical modelling through full-scale and small-scale models is widely implemented in order to define specific aspects of the prototype behaviour. On the other hand, numerical modeling is essentially required to cope with the complex geotechnical problems due to the ability of considering and analyzing all aspects of the model and can afford more perception about the behavior of structures such as geosynthetic-reinforced embankments. In this study, four different cases of unreinforced and reinforced embankment models constructed on soft and stiff grounds were studied. Small-scale physical modelling by means of centrifuge tests and numerical modelling by means of finite element simulations were performed. As the small-scale model was rotated in different acceleration fields during the centrifuge test, the dimensions of the centrifugal model were different from the original state of the prototype in different stages of the test. This paper focused on developing a finite element simulation based on the dimensions of a centrifugal model in different incremental acceleration fields applied during the stages of the test. Comparing the results of finite element simulations with the measurements of the centrifuge tests showed a good agreement between the two methods, which verified the reasonableness of the finite element models in analysis of embankments based on small-scale centrifugal dimensions. Moreover, the results showed the different deformation behaviour for embankments on soft and stiff grounds and indicated the significant effect of the geosyntheic reinforcement on increasing the stability of the embankment on soft ground

Numerical Modelling for Geoengineering in Tropical Region

‘Tropics’ include all areas on the earth where the Sun contacts a point directly overhead at least once during the solar year, and located surrounding the Equator. The tropics comprise 40% of the earth’s surface area and contain 36% of earth’s landmass. Tropical is sometimes used in a general sense for a tropical climate which means warm to hot and moist year-round. Tropical areas tend to experience more rapid weathering because large amounts of consistent rainfall and constantly warm temperatures that influence the rate of weathering. Tropical areas usually experience both, dry and wet season. The wet /rainy /green season is the time of year, ranging from one or more months, when most of the average annual rainfall in a region falls. This rapid change of hot and cold weather more or less influenced the geology characteristics of the area such as the weathering rate, the soil formation. The uniqueness of geological characteristics in tropical regions has intrigued researchers to explore in details as to how this climate condition influenced the in situ geotechnical process and geological characteristics in order to identify the issues and challenges faced by geotechnical engineers when doing construction in the region. In an ever more globalized world, we are compelled to embrace the technological advancement in order to stay competitive. Hence, by using numerical methods to solve geotechnical problems and analysis are seen to be one of the initiatives to excel in this field especially in tropical geoengineering.Numerical analysis using finite element and finite difference methods has become a mainstream design tool within geotechnical engineering in the last decades. Numerical modelling is a mature yet vibrant research area in geotechnical engineering. Its advancement has been accelerated in recent years by many emerging computational techniques as well as the increasing availability of computational power. A wide spectrum of approaches, on the basis of continuously advancing understanding of soil behaviour, has been developed and applied to solve various problems in geotechnical engineering. The aim of this edited book is to present original research output by fellows and members of Centre of Tropical Geoengineering (GEOTROPIK) that applied numerical modelling in their analysis of geoengineering in tropical regions. The study area are mostly located in Asian region such as Malaysia, Thailand and Sri Lanka. This book is themed around numerical modeling application in rock mechanics and geology engineering, geotechnical engineering, and geoinformation to measure, manage and analyze the geospatial data relating the earth and its application in tropical regions. This theme is in line with the function of GEOTROPIK as research centre and provider of consultancy services. I thankfully acknowledge the authors for their valuable contribution in this book. Last but not least I feel indebted to reviewers, fellow editors and all those who helped directly or indirectly to make this book a successful and notable remembrance

Field performance of transition rigid piled embankment with surcharged vertical drain over soft ground

Commonly, thick filling works over soft clay is aided with piled embankment at bridge approach to reduce differential settlement between the piled abutment and embankment over soft ground. However, long stretched thick filling works over soft ground requires substantial resources and time to construct rigid piled embankment. Generally for such long stretched and thick filling development over soft ground, other ground treatment such as prefabricated vertical drain (PVD) with surcharge is introduce to reduce the cost of construction. However, excessive total and differential settlement at the surcharged prefabricated vertical drain (SPVD) and rigid piled embankment intersection during post construction period may leads to rectification works over the time. This paper presents the field performance of an alternative design approach for long stretched thick filled embankment over soft clay at structure approach to control the differential settlement between the two conventional ground treatment approaches. With the introduction of the alternative ground treatment approach at the intersection of the two conventional ground treatment, post construction total settlement and differential settlement is reduced significantly