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Brief history of Swedish Soil Mechanics

Geotechnical engineering in Sweden has a long tradition, dating back to the work of such outstanding engineers and scientists as Albert Atterberg, John Olsson, Wolmar Fellenius, Sven Hultin and Walter Kjellman. The "Geotechnical Commission of the Swedish State Railways" was instituted in 1913 because of repeated landslides along the main railroad lines and can be regarded as one of the milestones of modern soil mechanics.

Landslide at Vita Sikudden on 1 October 1918

The term "geotechnics" (Swedish geoteknik) was coined by the Commission. The Geotechnical Commission worked under the leadership of Wolmar Fellenius, professor at the Royal Institute of Technology in Stockholm, and presented its report in 1922. The Commission investigated more than 300 embankment failures and land slips. The use of different field and laboratory investigation methods was discussed. In the report the following closing remarks were made:

"The Committee calls special attention to the fact that in several cases it is not yet possible to exactly determine the conditions of balance in loads on weak ground. By means of some examples the Committee shows that the demand for absolute safety is not defensible financially, and roughly estimates the costs of similar measures on the system of state railways to rather more than less than one hundred million Swedish crowns. At such places where there is a risk, but where to ensure complete security is not within reason on account of the expense, the Committee considers it better to endeavour to eliminate the risks of railway disasters, and this can be done by introducing effective guard arrangements, especially the automatic warning system. The Committee lastly calls attention to the fact that the solution of the geotechnical question lies in a considerably deeper and more extensive study of the same, and emphasizes the wish that the building department of the state may arrange a special medium for geotechnical investigation."
Report of the Geotechnical Commission of the Swedish State Railways in 1922

Besides the Swedish Geotechnical Commission, a special Harbour Committee was set up in Gothenburg in 1916 because of the failure of several quays.

Failure of the Stigberg quay in the harbour of Gothenburg in March of 1916

The analysis of this slide, which was performed under the guidance of Sven Hultin and Knut Pettersson, resulted in the development of the "Swedish Slip Circle Method". As was usual at that time, the shear strength of the clay was expressed as a friction angle. The back-calculation gave a value as low as 9 degrees.

"Swedish Slip Circle Method" developed by the Geotechnical Commission

The Geotechnical Department of the National Swedish Road Authority was started as early as 1936 under Dr. Walter Kjellman, and was reorganised as the Swedish Geotechnical Institute in 1944. The Swedish Geotechnical Society was founded on February 27, 1950. The Swedish Geotechnical Institute plays an important role in the practical application of research and innovative foundation methods. During its 50 years of existence, SGI has been the breeding ground for many geotechnical engineers who have since contributed to the progress of Swedish geotechnical knowledge. In 1959, the Swedish Commission on Pile Research was created.

Geotechnical investigation methods
Swedish geotechnical engineering has made significant contributions to various areas of soil mechanics and foundation engineering. The investigations of the Swedish chemist Atterberg on the consistency and classification of clays, the so-called Atterberg Limit Tests are today used all over the world. The work of the Swedish Geotechnical Commission on the shear strength and settlement of clay was also of fundamental importance.

The Swedish fall cone test was developed for determination of shear strength and sensitivity, Kjellman´s direct shear apparatus, unconfined compression test and first true triaxial apparatus are today standard tools of soil mechanics.

Swedish fall cone test device of 1915

The difficult geotechnical conditions in Sweden, with deep deposits of soft, sensitive clay required to the development of innovative geotechnical field tests, including the Swedish weight sounding method, the first vane test equipment constructed in 1919, Kjellman´s Iskymeter and the static cone penetrometer of 1948, the Swedish Standard Piston Sampler etc.

Swedish Weight Sounding in early 1920

Piling methods
Historically, the location of cities was often decided by good communication links (by sea, rivers or roads) and from a military, strategic viewpoint. In those areas, the geotechnical conditions were often less than satisfactory and buildings had frequently to be supported by piles. Also, defence structures and harbour facilities had to be provided with foundation support. It is thus not surprising that piling technology, using driven timber piles or hand-excavated and refilled shafts were used at an early stage. Driven piles were installed using a hammer, which was lifted by hand. Based on the experience from the shipping industry, rope-lifted hammers were introduced, which facilitated the installation procedure and made it possible to use horse-driven pile hammers. The first "modern" pile driving equipment was developed by the famous Swedish inventor Christoffer Polhem already in 1740. As a result of the industrial revolution, the first steam-driven pile hammer became available during the end of the 19th century. These were gradually replaced by diesel hammers, and later by drop hammers.

Timber piles were the most common foundation method for buildings on soft clay deposits. As long as these untreated piles were embedded in clay deposits and remained below the ground water level, they performed very well. Due to the uplift of the Scandinavian peninsula following the recent glacial period (up to several meters during the past 500 years), the top of many of the timber piles became exposed to air and started to deteriorate. Many of the ancient buildings in the Old Town of Stockholm had therefore to be underpinned during the past 20 years.

As a result of urban development, higher buildings and larger loads had to be supported on available ground, often with very poor geotechnical properties. Therefore, longer piles were needed which could carry higher loads. Towards the end of the last century, driven steel piles were used and the first concrete piles were introduced during the early period of this century. While steel tube and H-piles were commonly used in other countries, timber and concrete piles were the most common deep foundation method for heavy building loads. The harsh climate with cold winters and the geological conditions, consisting of very soft clay deposits on stiff till or rock favoured the development of driven, pre-cast concrete piles. The first concrete piles were used in Sweden around 1917. The use of timber piles was prohibited in the inner city of Stockholm in 1944 and gradually, the pre-casting technique of concrete piles developed and became refined. The longest concrete piles were installed in Gothenburg at the Swedish west coast, where the soft clay deposits reach a thickness in excess of 100 m.

Besides pre-cast concrete piles also other piling methods were used at some projects, such as driven, cast-in situ piles (Franki pile) during 1935, and later bored piles (Benoto piles).

The Swedish Commission on Pile Research was founded in 1959, which played an important role in the development of equipment, design and testing methods. The Pile Commission, which is still very active, combines the efforts from research at universities, the Swedish Geotechnical Institute with the practical experience of contracting and consulting companies. It took an active role in the development of new codes, which resulted in cost-effective design methods and more efficient use of driven concrete piles. In 1968, codes for three classes of concrete piles were introduced.

During that period, the piling rigs were modernised, moving on caterpillar tracks, and provided with adjustable leaders. Innovative solutions, such as cost-effective pile joints, rock shoes and pile monitoring techniques have contributed to the rapid development of Swedish infrastructure. The first patents for pile joints of pre-cast concrete piles were awarded around 1960 (type ABB and Herkules). Swedish hydraulic pile hammers (type Uddcomb and Banut) were developed, well as the first pre-stressed pile cushion.

During the 60´s, the first stress wave measurements were performed on concrete piles, which helped to replace the crude "piling formulas" (Hiley and Kruger) with rational driving criteria based on dynamic field measurements. Stress wave measurements became used more frequently during the 70´s and helped to optimise the pile installation process and quality control methods. The first International Conference on Stress Wave Measurements was arranged by the Swedish Pile Commission in Stockholm in 1980, the second in 1984.

In 1979, the Swedish Pile Commission issued a code for the design and installation of bored piles, and suggested methods for dynamic pre-loading of the bore hole using heavy tamping. As a result of the need for underpinning work in the Old Town of Stockholm, different types of small diameter driven piles (steel tube piles) were developed. These could be driven using light air hammers.

Stress wave measurements in combination with more sophisticated analysis methods (CAPWAP and WEAP) helped to advance the understanding of the pile installation process and the assessment of load carrying capacity. Soil structure interaction was studied extensively, and the findings of this research led to new design concepts, such as "creep piles" (floating pile rafts, where the load is being shared between the foundation slab and the piles).

Underpinning methods were further improved and several innovative pile methods were introduced, such as the Soilex Pile, which uses an enlarged pile base (Expander body). These new piling methods were more gentle and could be used even in vibration-sensitive areas, such as basements of ancient buildings and historic structures.

The European Federation of Foundation Contractors (EFFC) was founded in 1989, which since has played an important role with respect to the development of execution codes for different deep foundation methods. The Swedish Association of Foundation Contractors (PEF) represents Swedish foundation contractors in the EFFC, and was responsible for the development of codes for driven pre-cast piles.

Soil improvement methods
As early as 1940, Kjellman developed the cardboard drain and the vacuum consolidation method.

Principle of the Swedish vacuum method developed by Kjellman in 1952

The group of capable engineers around Kjellman at the Swedish Geotechnical Institute, made many valuable contributions to ground improvement techniques, such as Oleg Wager, the inventor of the pre-fabricated plastic drain and soil reinforcement by steel anchors and geotextiles and Hansbo on consolidation and ground improvement.

First application of "steel-reinforced" embankment, invented by Oleg Wager in 1966

Different types of vibratory compaction techniques, such as rollers and vibratory probes have been developed for shallow and deep densification of granular soils. Today, many of the soil investigation and foundation methods developed in Sweden are used throughout the world.

Probably the most important recent development in soil improvement is the Swedish "lime column method", which was invented in 1969 by Kjeld Paus. This method has since been further developed and is today the most widely used method for improvement of soft, compressible clay deposits. Highly advanced installation equipment with electronic monitoring systems have since been developed. Research is carried out under the umbrella of the recently founded Swedish Deep Stabilization Research Centre, located at the Swedish Geotechnical Institute.

Swedish Geotechnical Society (SGF)
The Swedish Geotechnical Society was founded in 1950, and has more than 600 individual members. The most important geotechnical event in Sweden is the annual "Foundation Day" (Grundläggningsdagen), where different topics of practical importance and interest are discussed.

"Back to Basics" Topic of the Swedish Foundation Day 1995

This annual gathering is usually very well attended. It is complemented by society meetings, which are arranged by SGF committees, dealing with geotechnical problems of particular interest at the time.
SGF, through its committees, works out standards and recommendations for geotechnical investigations, analysis and design methods. These and other important documents are published by SGF as technical reports or information pamphlets. Several of these reports are published in English.

One of the landmarks of the Swedish Geotechnical Society was the organisation of the X. International Conference on Soil Mechanics and Foundation Engineering, which was held in Stockholm in 1981. In addition, international conferences and symposia were organised by the Swedish Geotechnical Society, such as the first European Symposium on Penetration Testing, ESOPT in 1974, International Conferences on Application of Stress-Wave Theory, Nordic Geotechnical Meetings etc.

An important objective of SGF is to facilitate interaction between experienced and young engineers. Scholarships are awarded annually to outstanding students and researchers at different levels, encouraging them to visit research institutes, conferences or interesting projects abroad.
The Swedish Geotechnical Society has close co-operation with the Nordic sister societies in Denmark, Finland, Iceland and Norway. New contacts are being taken with the geotechnical communities in the emerging Baltic states, which share similar problems as the Nordic countries.

Geotechnical research
Geotechnical research in Sweden is carried out primarily at the major technical universities: Royal Institute of Technology, Chalmers Univeristy of Technology, Technical University of Lund, Technical University of Luleå. In addition, the Swedish Geotechnical Institute carries out extensive research programmes, being a link between the research institutions and geotechnical practice.

In Sweden, there is a long and fruitful tradition of a close co-operation between scientists, educators, practising engineers, manufacturers of geotechnical and construction equipment, clients and authorities. Research in areas of great importance to society is carried out in Commissions, with the task to focus research, development and dissemination of information on specific areas. By these Commissions, the work of which is financed by government authorities as well as by contributions from the industry, important contributions have been made to the development of Swedish geotechnical and foundation engineering.

The Swedish Pile Commission, the Land Slide Commission and the Swedish Vibration Committee are examples of fruitful co-operation between different sectors of society.


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