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Skempton, Sir Alec Westley (1914–2001), civil engineer and historian of engineering, was born at 216 Abington Avenue, Northampton, on 4 June 1914, the only child of Alec Westley Skempton (d. 1926), leather merchant, and his wife, Beatrice Edridge, née Payne. Skempton's father died of tuberculosis, the consequence of gassing during service in the First World War which subsequently led to pleurisy, but as he was never hospitalized there was no documentation to confirm this, and there was no pension for Beatrice Skempton. Skempton attended Waynflete House preparatory school in Northampton, where he was when his father died. In 1928 he moved to Northampton grammar school. With the aid of his father's savings his mother managed to continue to pay his school fees, even after he had moved to the grammar school.

Family connections, through his maternal grandfather who was works manager for British Reinforced Concrete, led Skempton to read engineering at university, and in 1932 he joined the department of civil engineering at Imperial College, with which he was closely connected until the end of his life. As a student he played an active role, and in his final year (1935–6) he was vice-president of the City and Guilds student union (City and Guilds being a constituent college of Imperial), and captain of both the City and Guilds and the Imperial College rugby first fifteens. The former team played on Wednesdays, the latter on Saturdays. An interest in sport, particularly rugby and cricket, remained with him all his life.

Even before he graduated, which he did with first-class honours in 1935, Skempton had decided to spend his life in research. Though he particularly enjoyed geology he was encouraged by Professor Sutton Pippard, then head of the department of civil engineering, to carry out research on reinforced concrete. Before completing his PhD he was offered a research post at the Building Research Station (BRS) at Garston, Hertfordshire, where he moved in 1936. Nevertheless his interest in geology developed into a life's work in the then evolving subject of soil mechanics. A soil physics section had been formed at the BRS in 1933, and by 1935 its name had changed to soil mechanics. Within months of arriving at the BRS, Skempton had abandoned his studies of concrete and in January 1937 he joined the soil mechanics section, where he worked for the next ten years.

A few months after Skempton joined the soil mechanics group the Chingford dam in the Lea valley, Essex, then under construction, collapsed. Similar dams in the Lea valley had been constructed quite safely, so the reason for the collapse was not immediately apparent. The BRS was asked to advise, and the soil mechanics group, of which the young Skempton was rapidly becoming a leading member, quickly concluded that the problem was the incomplete consolidation of the alluvial clay foundations. This explained the stability of the earlier dams, which had been constructed more slowly in the horse-and-cart era (thus allowing time for consolidation so that the dam's foundations could gain strength). At Chingford mechanized plant was used for construction, so the dam was constructed quite quickly. Karl Terzaghi (universally regarded as the father of soil mechanics) was brought in, and he confirmed the diagnosis, leading to a long association between Terzaghi and the BRS group. Skempton remained at the BRS until 1946, and made significant contributions to projects involving Waterloo Bridge, the Muirhead dam (near Largs, Ayrshire), and Gosport Dockyard among other structures.

During his student days Skempton met (Mary) Nancy Wood (1912/13–1993), then a student at the Royal College of Art, situated adjacent to Imperial College. She was the daughter of Ernest Reginald Wood, silk spinner, of Brighouse, Yorkshire. They married on 5 July 1940, and Nancy was his constant companion and supporter until her death. They had two daughters, Judith and Katherine. Nancy was a fine bookbinder but her particular expertise was wood engraving. In 1989 Skempton, in tribute to her, published privately a selection of her engravings.

The civil engineering subject of soil mechanics was in its infancy in the 1930s and 1940s, and Skempton's research was stimulated by engineering problems brought to the BRS. His success in this respect was demonstrated at the Second International Soil Mechanics Conference at Rotterdam in 1948, where Skempton was author or part author of no fewer than ten papers, seven of them published in the conference proceedings, and two in the first two numbers of the soil mechanics journal Géotechnique, which was established (by a group that included Skempton) in that year.

Skempton returned to Imperial College in 1946 as senior lecturer at the invitation of Sutton Pippard, and remained there for the rest of his life. In 1947 he became reader in soil mechanics, and in 1955 professor of soil mechanics. He took the title of professor of civil engineering on becoming head of the department of civil engineering in 1957, a title he held until his retirement in 1981. He then became professor emeritus and a senior research fellow of Imperial College, working almost daily in the civil engineering department until only three or four months before his death.

Skempton made many contributions to soil mechanics, but undoubtedly his most important were to the study of slopes and landslides. In 1953 he resolved to apply the principle of effective stress to the study of clay slopes, and the first result of this was an article published in 1954 analysing a landslide at Jackfield, Shropshire. Skempton was particularly associated with the topic of residual strength, the strength that the soil retains after a landslide has taken place. This was the subject of the fourth Rankine lecture, published in Géotechnique in 1964. In this he reassessed the analysis of Jackfield and other landslides, and demonstrated that the residual strength was a fundamental property, dependent on, among other things, the mineralogy of the soil. Though ideas on residual strength developed, with further contributions from Skempton himself, this lecture was Skempton's most important single contribution to soil mechanics.

The late 1950s and early 1960s proved golden years, with one influential paper following another. Consulting work stimulated research on the allowable settlements of buildings, leading to recommendations which were still being widely followed at the time of his death, as was his pragmatic ‘α-method’ (first outlined in 1959) for the design of bored piles in London Clay. Another important contribution was his perceptive assessment of horizontal stresses in the London Clay. Collectively, Skempton's papers were perhaps the most influential ever published in the subject of soil mechanics by one individual.

Throughout his career Skempton's advice on engineering problems was widely sought. In addition to Chingford dam he advised on a number of embankment dams, including that at Chew Stoke, for which he designed an array of sand-drains to accelerate consolidation of the weak alluvial foundations, the first such in the UK. He was retained as consultant by the consulting engineers Binnie and Partners (later Binnie, Black, and Veatch), his first commission from them being Usk dam in 1951. However, perhaps the most important of the many Binnie schemes with which he was involved was Mangla dam in Pakistan (1958–67), where his recognition of tectonically sheared zones in the dam foundations was crucial to its safe construction. In 1984–5 he reviewed the failure of Carsington dam, Derbyshire, which had collapsed in 1984. Large landslides on which his advice was sought included Sevenoaks (during 1965–7) and Mam Tor, Derbyshire (on which he published an article in the Philosophical Transactions of the Royal Society in 1989). His work on building foundations included that on Waterloo Bridge, London, during 1938–9, the tower of Pisa, Italy, in 1965–7, and reviews of the foundations of both St Paul's Cathedral, London (during 1970–72) and Salisbury Cathedral (in 1982).

In his years at the BRS, Skempton developed an interest in the history of civil engineering, his influence in this subject being as great as his influence in soil mechanics. His major historical contribution was the study of early civil engineers, especially those of the eighteenth century, whose achievements had been ignored by previous historians of engineering. He re-evaluated the careers of the founder of civil engineering, John Smeaton, in a book-length study published in 1981, and of Smeaton's contemporaries, John Grundy (in an article published in Lincolnshire History and Archaeology in 1984) and William Jessop (in a biography co-written with Charles Hadfield and published in 1979). He also wrote an authoritative bibliography of early civil engineering literature, Civil Engineers and Engineering in Britain, 1600–1830 (1996). In the last five years of his life he edited and contributed extensively to A Biographical Dictionary of Civil Engineers in Great Britain and Ireland, 1600–1830 (2002). He worked on the proofs, but did not live to see its publication.

Skempton was widely regarded as one of the leading developers both of the subject of soil mechanics and of the history of civil engineering. Soil mechanics as an engineering discipline hardly existed at the time of his own engineering education in the 1930s, but long before he retired the subject had become, along with structural and hydraulic engineering, one of the three main branches of civil engineering. He received many honours. He became a fellow of the Institution of Civil Engineers in 1957, and was elected FRS in 1961. He became a founder fellow of the Royal Academy of Engineering in 1976. He was awarded numerous medals and honorary degrees, and his ultimate accolade was the knighthood he received in January 2000.

Skempton had a great love of classical music, and was a competent flautist. A particular fondness for eighteenth-century music led to a study of the Loeillets, a French family of composers, published in Music and Letters in 1962. Active almost to the end, he died at the Chelsea and Westminster Hospital, London, on 9 August 2001, of lung cancer and bronchopneumonia. He was survived by his two daughters.

Richard J. Chandler

Sources  

R. J. Chandler, Memoirs FRS, 49 (2003), 509–19 · J. Niechcial, A particle of clay: the biography of Alec Skempton, civil engineer (2002) · The Independent (21 Aug 2001) · The Times (10 Sept 2001) · The Guardian (4 Oct 2001) · WW (2001) · personal knowledge (2005) · private information (2005) · b. cert. · m. cert. · d. cert.

Likenesses  

W. Bird, photograph, 1964, RS; repro. in Memoirs FRS, facing p. 511 · R. Foster, oils, exh. Royal Society of Portrait Painters 1982, repro. in Niechcial, A particle of clay, frontispiece · photograph, repro. in The Times

Wealth at death  

£1,959,056: probate, 15 Jan 2002, CGPLA Eng. & Wales