Ebook: Soil-Structure Interaction, Underground Structures and Retaining Walls
With construction techniques becoming ever more complex, and population pressure leading to the development of increasingly problematic sites, expertise in the area of soil structure interaction is crucial to architectural and construction industries worldwide.
This book contains the proceedings of the ISSMGE Technical Committee 207 International Conference on Geotechnical Engineering - Soil Structure Interaction and Retaining Walls - held in St Petersburg, Russia, in June 2014. The conference was dedicated to the memory of the outstanding geotechnical expert Gregory Porphyryevich Tschebotarioff.
Topics covered at the conference included: soil structure interaction, underground structures and retaining walls, site investigation as a source of input parameters for soil structure interaction, and interaction between structures and frozen soils.
The papers included here are the English language papers. Papers presented by the authors in Russian are published by the Georeconstruction Institute of St. Petersburg.
Technical Committee 207 ISSMGE “Soil-Structure Interaction and Retaining Walls”, of which I have been honoured to be the Chairman since 2005, has organized eight conferences and special sessions in Saint Petersburg, Ghent, Moscow, Rostock, Dubrovnik and Paris.
This conference which is taking place during the white nights in Saint Petersburg is dedicated to the memory of an outstanding geotechnical expert Gregory Porphyryevich Tschebotarioff.
Gregory Porphyryevich Tschebotarioff is mentioned in all encyclopaedias as a Russian-American scholar, a specialist in soil mechanics and foundation engineering. He was born in February 1899 in Pavlovsk. His parents owned a splendid residential house in Tsarskoe Selo, a suburb of St. Petersburg.
In light of several inconsistencies in his subsequent biography I would like to clarify certain moot points based on archive materials found in St. Petersburg and specifically in the library of Saint Petersburg University of Transport, formerly known as Alexander I Institute of Transport, founded in 1809. In 2014 Saint Petersburg University of Transport regained its association with the name of that benevolent Russian Emperor Alexander I, known by many to have been its founder. This oldest establishment of education in the field of technology is also inherently connected with the name of Gregory Porphyryevich Tschebotarioff.
Gregory Porphyryevich Tschebotarioff was born not simply in the family of a Cossack officer. His father was especially close to the Russian Emperor's family, as can be now stated unequivocally, whereas his wife and mother of G.P. Tschebotarioff served as a lady-in-waiting to the Empress. Prior to the October Revolution of 1917 his father was in the rank of lieutenant-general serving in the Guards of the River Don Cossack Regiment. And one more interesting touch: G.P. Tschebotarioff's godmother was the Dowager Empress, the mother of Tsar Nicholas II, who was deposed after the 1917 uprising.
Gregory Tschebotarioff's first wife was Lydia Fyodorovna Krasnova, who prior to their marriage was a young friend of Tschebotarioff's mother and resided in Detskoe Selo (currently a town of Pushkin, a suburb of St. Petersburg mentioned above). She was close to the emperor's family even through the location of her house. It was natural that generals true to the emperor, like Tschebotarioff or Krasnov, Grigory's father in law, as well as the historic River Don ataman Kaledin, felt it a call of duty to preserve Russia's integrity by being victorious both against Germany and inside Russia itself, at the time embroiled into Bolshevik revolts, which the remaining army tried very hard to quell. Those included the well-known mass uprising on the River Don. Subsequently the forces of the so-called “Volunteers” or the White Army were fighting battles with the Red Army Corps, initially victorious but later largely unsuccessful. The last stronghold of the whites on the River Don was the city of Novocherkassk. Allegedly, it was there that Grigory Porphyrievich ended his military career. Here I would like to mention several interesting moments from the highly eventful revolution months of 1917–1918. The young Gregory Porphyryevich, having barely turned 18, was appointed a personal aide to general Krasnov, one of the combatants against the Reds in 1917–1918 in Russia. Being an expert German translator, having legal, albeit secondary education, Gregory took part in the famous talks between Krasnov, Trotsky and seaman Dybenko, which were attended also by the German military.
Now let's move to a bit of historical data, establishing the fact that his legal education began at the age of 12 when he joined the Imperial Law School. It was already during the war that he finished a concise course at Mikhailovsky Artillery School and graduated in 1916 in the rank of corporal. It was thus impossible for him to have been one of the leaders of the Whites' opposition neither in St. Petersburg nor on the River Don, as is sometimes believed. He doubtless must have felt deeply for them, but his chosen career at that turbulent time for Russia was that of a civil or transport engineer.
Here I have in front of me a copy of G.P. Tschebotarioff's inscription and signature on a book on soil mechanics published in the USA and presented in 1973 to professor Vladimir Petrovich Sipidin at the Department of subsoils and foundations of St. Petersburg Transport University (Figures 1 and 2). Therein Gregory Tschebotarioff designates himself a student who entered the Transport University in 1918. The inscription states that the book is being presented to be read and subsequently donated to the university library.
The full title of the book is “Foundations, retaining and earth structures”. I am a member of the international community of geotechnical engineers united today by the ISSMGE, and I am really happy about the fact that G.P. Tschebotarioff had chosen his professional career at our Transport University and that amongst his colleagues, professors of soil mechanics, to whom he would subsequently present his books, were representatives of our department at St. Petersburg. Moreover, he held Russian specialists, and particularly geotechnical engineers, in high regard. Having worked in the USA for a long time he condemned politically engaged distortions of Russian history published by the USA media during the McCarthy era at the time of the so-called “cold war”. It is officially known that during exchange of scientific delegations between the USA and the USSR Professor Tschebotarioff declined certain advances on the part of the CIA. Moreover, as a sign of protest he turned down the Professor Emeritus rank at Princeton. Another reason for that reaction were cases of persecution of professors of Slavic nationalities, particularly those teaching the Russian language and literature. This gives us a man of a very broad range of attention in the areas of both science and humanities.
All this does not quite endorse the image of a leader of Whites' opposition to the Reds on the river Don. At the age of 19 in 1918 he opted to come to St. Petersburg and enter the University of Transport which he could not graduate from for purely political reasons, being a member of a family close to the Russian Emperor, who were at the time being persecuted by the Soviet law enforcement agencies.
Having spoken to my senior colleagues from the field of soil mechanics and construction I confidently can bring to your attention the following moments from Gregory Tschebotarioff's youth. After entering the University of Transport he understood quite clearly that his social origins could lead to quite dramatic consequences. He was aware of what was being done to his colleagues – officers from famous St. Petersburg families, but the wish to become a professional civil engineer prevailed over the sense of self preservation danger. According to the famous professor of St. Petersburg University of Architecture and Construction (St. Petersburg Institute of Civil Engineering) and St. Petersburg Transport University Vladimir Alexeevich Gastev and professor Victor Anatolievich Florin, Gregory Tschebotarioff was interested in soil testing research in the Laboratory of Soil Mechanics at the Transport University. At that time the laboratory supervisor was the famous Russian and subsequently American professor S.P.Timoshenko. I am convinced that their ways crossed whilst still in St. Petersburg: it was in that oldest mechanical laboratory that N.M. Gersevanov conducted his pile tests (a graduate of the Transport University of 1902 and son of the rector of the University who served in that capacity for more than 25 years). Subsequently, the leading and one of the largest specialized underground construction and foundation engineering institutes in Russia was named after N.M. Gersevanov (known today as Moscow NIIOSP). Among his student contemporaries there were N.N. Maslow and V.A. Florin who subsequently having become leading geotechnical specialists of world renown served as translators of papers and monographs by G.P. Tschebotarioff published in the USA. One can say quite confidently that since the very first days of his study at the University of Transport, being in contact with a constellation of future geotechnical gurus (S.P. Timoshenko, V.A. Gastev, N.N. Maslow, N.M. Gersevanov), he could not help getting engaged into geotechnical science which was at the time at the breaking point in terms of its importance for construction practice, and not only in Russia. He continued to maintain his ties with those bright minds also in his late years. The present writer was not spared the “geotechnical bug” that tied him to the circles of people engaged in soil mechanics after attending lectures by professor N.N. Maslov in 1957 in St. Petersburg. I was at the time a cadet of the military faculty at the University of Architecture and Construction (former Institute of Civil Engineers, later known as LISI).
According to Prof. N.N. Maslov young G.P. Tschebotarioff arrived to Berlin Technical School with notes on lectures by S.P. Timoshenko on theory of elasticity and books including publications by the Transport University Press presreved in his personal library. He profoundly impressed the examination board having presented to them his Russian knowledge in the German and English languages. According to his own testimony, Gregory Tschebotarioff had free and lengthy conversations in those languages with the members of the board and the invited leading civil engineers from the Berlin Technical School.
Sadly, fear for his life never left G.P. Tschebotarioff during the war years after the October Revolution in 1917, even after his departure to the south of Russia. Those fears were especially reinforced after he found out that some people known to him were imprisoned after their arrests and the military officers arrested in those years were loaded on ferry boats and drowned in the Gulf of Finland. This information is contained in his memoirs. I read about a lot of similar facts in Tschebotarioff's book entitled “Russia, My Native Land” published in New York in 1964 by McGrow-Hill Book Company. From this book I learned that his grandfather, whose name was also Gregory Tschebotarioff, was of Cossack stock and, a graduate of the Paris Institute of Technology, was in charge of railway construction in the South-East of Russia connecting the cities of Rostov and Voronezh in late 19th – early 20th centuries, whereas his mother Valentina Ivanovna during the war was a nurse in the military hospital at Tsarskoe Selo, where at this time the Empress Alexandra Fyodorovna was also engaged in a similar capacity. Gregory Tschebotarioff doubtless was in contact with them – his mother and his god-mother, during his sojourn while on leave in 1917 at Tsarskoe Selo, where his family resided at the time.
Initially it was with a certain degree of reluctance that I read sections on G.P. Tschebotarioff's life not connected to soil mechanics and foundation construction. But those five chapters read like an adventure story resembling “The Road to Calvary” by Alexey Tolstoy. G.P. Tschebotarioff was frequently arrested in the south of Russia but he was lucky “not to have been shot” as he himself put it in the book. Once he was mistaken by the Reds' patrol to be a “Whites' guerrilla fighter” due to a typical white officer's knapsack he was wearing, but he was spared by the timely benevolent intervention of a high-ranking official of the Reds who happened to be a former officer of the Imperial Russian Army, and a native St. Petersburger. He quietly talked to Gregory Tschebotarioff and in spite of violent protests from the blood-thirsty revolutionaries let him go. The second arrest was even more dangerous but he had time to conceal himself from the arresting brigade in the huge crowd of pro-revolutionary populace greeting the arrival of the Red Leaders to the city of Novorossiysk. In such environment of constant threats the only solution left for him was emigration. He was evacuated to Egypt together with the College of the Don Cadets where he worked as instructor since 1921, acting as an aide to the Artillery Inspector of the Don Army. We will not be far from the truth supposing he instructed his officers in the matters of construction science because construction was the only practical field where disciplined Russian officers were in high demand, organizing and conducting building activities – there were simply no other activities ongoing in Egypt at that time.
After graduating as a civil engineer in Berlin, Gregory Tschebotarioff worked in Egypt. Demanding ground conditions of that country alerted him to the issue and importance of soil mechanics in general, and to complicacy and responsibility of foundation construction in particular. He served as a consultant in these areas for some time in France, Germany and the USA. As of 1937 he became a fulltime professor at Princeton, holding a tenure in the art of construction. It is interesting to point out that directions connected to soil mechanics and foundations, including stability of retaining structures were quite rightly regarded as construction art. Gregory Tschebotarioff was involved in projects related to construction of bridges, high dams, tunnels and other civil and military structures, some of them being unique.
I would like to point out the following moments from Gregory Tschebotarioff's notes which infused our work in ISSMGE TC 207 “Soil-Structure Interaction and Retaining Walls” for eight years (2005–2013):
– he alerted the scientific community to instances of serious discrepancy between results of large-scale and expensive in situ tests and calculations, including those behind recommended values in design standards and construction codes;
– he objectively reviewed hypotheses and theories propounded by various authors and prevalent at the time openly challenging instances of inconsistency and obsolescence;
– he reinforced understanding of soil mechanics as the theoretical foundation for calculation and computation paying specific attention to soil tests as capable of clearer representations of stressed-strained conditions in soils and structures of any degree of responsibility;
– in his book “Soil Mechanics, Foundations and Earth Structures” Prof. Tschebotarioff provides a lot of numerical data and gives a large number of numerical examples as compared to calculations according to various theories.
Below follow some highlights from a section of his book entitled “Interaction between structures, foundations and subsoils”. Here is a direct quotation: “The bearing soil beneath a foundation, the foundation itself and the superstructure form a connected system and must therefore be always viewed as a unified whole”. This premise was in the past too often ignored and is still sometimes overlooked by individual authors. All of it is largely connected to the complicacy of the actual problem, which was impossible to calculate efficiently with the old mathematical toolbox, that is to say without the computerized numerical modelling capabilities. Even today, theoretical background lags somewhat behind the actual contemporary construction practice, in which we have witnessed mega-deep underground structures and super-tall skyscrapers over 1000 meters tall.
Reviewing his quotes about calculations and in situ measurements one may conclude that Gregory Tschebotarioff was and has remained an ideologist for the activities of our contemporary Technical Committee No207 (Soil-Structure Interaction and Retaining Walls) of ISSMGE, which I was fortunate enough to head for eight years (2005–2013), and which was hosted by Russia and the Transport University.
Without looking down on the SSI related research of my contemporaries, it is important to point out the significance of Prof. Tschebotarioff's ideas which he even in his day and age communicated to colleagues whilst a delegate to almost all congresses and conferences of ISSMGE (whose abbreviation certainly changed a number of times over the years), starting from the first 1936 congress in the USA. He frequently chaired sessions and sections, as well as working committees on stability of retaining walls and underground structures.
In 1958 the USA and the USSR exchanged delegations of scientists and engineers. As member of the American delegation Gregory Tschebotarioff visited Moscow, Leningrad, Kiev and Stalingrad. He summarized his impressions in the following words: “I was leaving with a happy feeling that my motherland – Russia – was alive and recovering after the terrible ordeals which it had had to suffer”.
Concluding my account of the life of a world-famous geotechnical specialist Gregory Tschebotarioff, who started his career as a student of the St. Petersburg Transport University in 1918, and developed into a great specialist at Princeton in the USA, it is relevant to address a possible question from my geotechnical colleagues as to why it was that the members of TC 207 “Soil-Structure interaction and retaining walls” suggested a lecture dedicated personally to Prof. Gregory Tschebotarioff. I believe that soil-structure interaction was the leading element in his works and, additionally, extensive systems of monitoring on large scale projects in the USA assisted his evaluation of integrity of calculations and in situ tests.
The two sessions allowed to TC 207 “Soil-Structure Interaction and Retaining Walls” at the 18th International Conference on Soil Mechanics and Geotechnical Engineering in Paris in 2013 hosted about 1350 conference delegates, which demonstrates importance of our field to the geotechnical community. We enjoyed record attendance figures, which was pointed out in the concluding speech by the newly elected ISSMGE President Roger Frank (France). All significant construction projects over the last 10 years have broadly implemented systems of mathematical modelling in design, during construction and in subsequent monitoring. This was conducive to unification of “the three elephants” who serve as foundation for our profession both in new construction and in reconstruction. The three elephants in question are the architect, the superstructure engineer, and the geotechnical engineer. The reports at TC207 SSI sessions in Paris presented bold achievements implemented in design of supertall structures (over 1000 m) constructed in Dubai, as well as in other unique structures using state-of-the-art software engineering solutions and contemporary construction codes (Proceedings of the TC207 workshop on soil-structure interaction and retaining walls – September 2013, Paris – www.paris2013-icsmge.org).
The geotechnical engineers of the new century have reached a new stage in numerical calculations using advantages of contemporary computing, i.e. such as were simply not there before. This disadvantaged level of calculation methods troubled Professor Gregory Tschebotarioff and burdened him greatly, which he openly wrote and spoke about.
In conclusion I would like to quote our newly elected ISSMGE President Professor Roger Frank: “The perspective of contemporary codes for geotechnical design will be grounded in three words: “SOIL-STRUCTURE-INTERACTION”!"
Chairman of TC207 ISSMGE (2005–2013)
Professor V.I. Ulitsky (Russia)
Soil-structure interaction calculations constitute a basis for design decision making on a structure of any building even an ordinary housing. The importance of soil-structure interaction calculations largely increases when unique structures are designed for which construction there is no experience in geotechnical conditions of a given area. Special interest is placed on calculations of a high-rise building on soft subsoil where there is a necessity to estimate soil strains caused by application of unusually high loads.
In this paper the behavior of single piles under lateral impact is investigated by using the performed pendulum and bogie tests. Three types of soil deposits were used in the experimental tests including hard clay, loose sand and crushed limestone. The acceleration and displacement of the striking mass are measured. The results show that the soil response to impact is a function of soil stiffness; however the inertia and damping resistance are also important contributors. In order to model the system, a Single Degree of Freedom (SDF) model with two different basic materials is used to find the best simple model to predict the behavior of piles under impact. Finally an advanced model with multi degree of freedom is used to analyze a single pile under the pickup truck impact with 60 miles per hour. The results of the simple model and the experimental tests are compared with the LS-DYNA simulations.
A 5 m high earth fill embankment comprising vertical side-walls constructed from precast concrete wall panels tied together using steel straps was constructed on a 10 m thick deposit of soft clay. Due to the relatively small specified settlement tolerances of the embankment/wall structure, ground improvement in the form of drilled displacement columns (unreinforced concrete columns) was used to improve the engineering properties of the embankment foundation. This paper discusses the design and construction of the embankment and foundation system and compares the predicted settlements with those measured after construction. Discussion on the quality control measures adopted during construction is also provided.
The analysis of the soil-structure-interaction is a very important part during all stages of planning, design and construction. Large urban construction projects create an impact not only on neighbouring structures but also on existing, sensitive underground structures, like metro and street tunnels. But not only new constructions have an effect on existing structures. Deconstruction projects may cause enormous displacements as well. For the analysis of the soil-structure-interaction in most cases numerical methods are necessary. For verification of the numerical simulations geodetic and geotechnical measurements according to the observational method have to be carried out. An outstanding large urban construction project on existing underground structures of the metro of Frankfurt am Main, Germany, is presented in this paper.
With rapid development in metropolitan areas, deep excavation and tunnelling are often carried out close to existing buildings or infrastructure. The soil movement due to excavation may cause damages to adjacent foundation, worse for shallow foundations as compared to deep foundations. In this keynote paper, the latest development and understanding of soil-structure interaction involving foundation subject to adjacent excavation are presented; with references to successfully implemented projects or research work based on finite element modelling, centrifuge experiments and field monitoring, observations and interpretations. The novel concept of limiting soil pressure due to excavation stress relief is also presented.
The lecture will cover mainly the importance of stiffness parameters of crushable type of foundation sands in the perspective of the state of the art of soil testing and its new developments.
Any soil structure interaction model (SSI) can be deployed successfully or can fail depending on the reliability of the estimations of the soil structure interaction stiffness parameters. The stiffness evaluation of the engineered materials' structural elements and their combined role in the structure itself, commonly can be evaluated rather easily. However, the key issue and the much more problematic interaction parameters in any successful SSI analysis are linked to the soil stiffness, at the relevant strain levels, of the specific interacting soil layers under the corresponding structural loading conditions.
Piles are powerful geotechnical foundation elements which are suitable for most subsoil conditions where structure loads should be transmitted to deeper layers either to fulfill the required bearing capacity or to control the deformation to acceptable values regarding the structural serviceability requirements. In most cases, the pile foundations consist of group of piles. Realistic considerations of the pile group action regarding both the ultimate bearing capacity as well as the deformation behavior of the pile group are necessary to achieve a reliable, efficient and economic design. This paper deals with performance of pile groups under vertical compression loads. Simple analytical methods to estimate the settlement of pile groups will be presented and compared with enhanced three dimensional numerical analyses. The field monitoring of a well documented pile group under vertical compression loads and the feed-back of this information into the analyses procedure of the same pile group applying different analytical models will be demonstrated and discussed.
The paper contains results of long-term settlement monitoring of historic buildings in St. Petersburg. Based on results of repeated surveying, statistical processing of settlement rates of more than 2300 historic buildings was performed. Basic conclusions are drawn as to distribution of maximum settlement values throughout the city area. Also, the paper contains settlement monitoring results for 30 buildings constructed on soft soils in St. Petersburg (monitoring period extending from 23 to 77 years). Basic conclusions as to the character of settlement development are offered alongside primary comparisons of monitoring results with engineering methods of settlement calculations. The analysis thus performed is necessary for development and verification of engineering calculation methods, as well as of numerical rheological models of subgrade behaviour.
This article presents a developed design method applied in an actual structure (St John's Church, Tartu, Estonia) during the process of extensive underpinning. The article focuses on a practical theory of how to implement soil-foundation-pile interaction using pretested, end-jacked piles and how to design a strip foundation using only one method based on ultimate limit state (ULS) and serviceability limit state (SLS).The method takes the following into account as geotechnical requirements: contact pressure, total settlement and angular distortions. As far as structural requirements are concerned, the method considers admissible plastic rotations, end movements due to displacement angle, as well as control of cracking.
The surrounding conditions of tunnel lining may be changed during the investment period, which lead to a redistribution of forces acting on the tunnel lining, and perhaps generate new forces that are not taken into account during the design. In this paper, a case study of Alsafkon tunnel is regarded, which is one of the Syrian Railway deep tunnels. The lining of this tunnel suffers from cracks, leakage, and other defects. The results of numerical analysis are conformed to the current situation of the tunnel in terms of distributed cracks places in the concrete lining. The study showed also the importance of improving the lens properties to avoid the total fall down of the tunnel.
Three techniques for the study of the soil structure interface properties will be presented. The first technique involves the development of a 3D surface roughness parameter to evaluate the skin friction. The second technique is used to map contact stress concentrations at the soil structure interface using sensitive films developed for medical profession. The third technique is manufacturing artificial crushable sand at the desired properties to study static and dynamic interface behavior of soil and concrete. All of the techniques presented have a potential to understand the interface behavior in more detail. The techniques presented are implementable and practical.
The structure of the Villa Méditerranée is in an unstable position, which gives to four of its foundations a permanent traction load. Each of these foundations is stabilised by 4 to 6 active permanent anchors (149 to 349 Tonnes of load service each). In order to limit deformations due to elasticity of prestressing cables, a specific level of prestressing has been defined. The paper presents the design, the achievement and the monitoring of the prestressing anchors, in order to insure the stability of the structure.
Many river dikes and embankments in the coastal region of Tohoku area were damaged due to strong ground motions of the 2011 Off the Pacific Coast of Tohoku Earthquake and subsequent attack by the tsunami. This paper analyzes the cause of damage to the Yoshihama river dike located in Ofunato city of Iwate prefecture based on past field investigations and numerical simulations. Analyses revealed that the dike body had low liquefaction resistance and the volume change after liquefaction was rather large. Due to main shock and aftershocks there is likelihood of liquefaction in dike body and the re-liquefaction possibilities are high even under small ground motions. Based on the series of analyses it could be confirmed that even though the dike body was covered with concrete panels, due to liquefaction induced settlement of the embankment, gaps developed between the embankment crown and the concrete covering. These gaps ultimately reduced the tsunami resistant characteristics of the dike, and thus resulting in the collapse of the dike.
Cases of deformation in reinforced soil retaining walls have been reported in Hokkaido, Japan. Based on a survey of the deformed cases, the deformation was attributed to poor winter construction in which portions of the embankment soil froze and then subside during the thawing period, which resulted in bulging of the wall.
In this study, to clarify how the temperature acting on the groundaffects the pulling resistance of the strip, pull-out tests were conducted under various embankment materials and curing conditions. The pulling resistance under the various construction conditions is discussed.
Based on long-term research on soil frost heave conducted in laboratory and in situ including both experimental and expert investigation sites the influence of groundwater level on frost heave-induced deformations has been identified. Nature of change of moisture during frost penetration has been studied, parameters of changes of water accumulation coefficient for the main types of soil in Minusinsk cavity have been obtained. Options of anti-heave activities during construction for driven and end-bearing piles have been proposed.
This study investigates the oblique capacity of a drilled pile embedded in a marine ground containing methane hydrates using the distinct element method. Results indicate that the presence of methane hydrates significantly enhances the uplift and lateral capacity of the pile. The peak shaft resistance of the pile decreases with the decrease of the inclination angle of pile displacement due to de-bonding, while the residual shaft resistance increases as a result of increasing lateral earth pressure mobilized at large pile displacement. The uplift component of the oblique forces has detrimental effect on the lateral capacity of the pile. The oblique capacity of the pile can be empirically correlated to the inclination angle of the displacement of the pile head.
The continuum modeling of polymeric sheet reinforcement–backfill interaction is presented. Polymeric sheet reinforcement is subjected to axial pull at one end of the reinforcement. The continuum analysis is carried out by FLAC (Fast Lagrangian Analysis of Continua), a software based on the finite difference method. The displacements of reinforcement are quantified for different pullout forces and the variations of displacement and tension along the reinforcement length presented. The effects of axial stiffness of reinforcement, soil–reinforcement interface shear stiffness and length of reinforcement are quantified.
The paper introduces an original approach to face seismic hazard on existing buildings by treating with a soft grout a thin layer of soil at a certain depth. The paper presents a parametric analysis with reference to the case of a typical clayey soil, considering the ideal cases of an horizontal or vertical layer. The information gained from these two extreme cases are essential to understand the true behavior of a real soft caisson, whatever its shape. Surprisingly, the seismic isolation capacity of the vertical layer depends not only on shear stiffness but also on bulk stiffness, and this has to be taken into account in the design of a seismic barrier composed of both vertical and horizontal layers.
The paper presents some results of a joint research of three universities from Rio the Janeiro, Brazil, aiming at the observation of concrete creep and shrinkage effect on soil structure interaction. In this paper an 18 story building resting on shallow and deep foundations was submitted to a site instrumentation to monitor settlements and loads of some columns close to the ground floor during the construction phase. Particular attention is given to the effect of concrete creep and shrinkage in soil structure interaction effects. Due to the extent of the experimental results, only part of the database is presented.
The paper describes principles of solving problems to calculate changes in stressed-strained conditions of soils during their freezing and thawing, necessary to predict behaviour of structures contiguous with these soils. Approaches are suggested whereby to choose mathematical soil models necessary to predict deformations of frost heave during freezing, including cases of water migration in soils and formation of frost related cracks, as well as models to figure out potential soil deformations during thawing.
A comparative analysis of a deep foundation of a highrise building in Bangkok subsoil shows that adoption of the piled raft design concept could result in a significant cost saving of the foundation work. When the raft was placed in the first stiff clay layer, the load share by piles was reduced to 77% from 100% generally considered in the traditional practice. The required number of piles could be significantly reduced without scarifying stability of the foundation and settlement requirement for the building. The 3D FEM analysis yielded a more realistic settlement condition of raft and load distribution of piles than the conventional plate on spring analysis owing to its direct and complete consideration of soil structure interaction.
A non-classical alternative was adopted for the foundation system of a thirty-storey building in Beirut, Lebanon. The subsurface strata included a thick layer of highly weathered marls and/marly limestone overlying the karstic limestone base stratum. Ground improvement by rigid inclusions/mortar columns was proposed, analyzed, designed and successfully executed. 2D & 3D Finite element simulations were conducted to assess the degree of improvement, and then used to perform/finalize the design of the foundation system. The paper discusses the conducted analyses & presents some parametric studies & recommendations.