Numerical Methods in Soil Mechanics D.PDF Numerical Methods in Geotechnical Engineering contains the proceedings of the 8th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE 2014, Delft, The Netherlands, 18-20 June 2014). It is the eighth in a series of conferences organised by the European Regional Technical Committee ERTC7 under the auspices of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). The first conference was held in 1986 in Stuttgart, Germany and the series has continued every four years (Santander, Spain 1990; Manchester, United Kingdom 1994; Udine, Italy 1998; Paris, France 2002; Graz, Austria 2006; Trondheim, Norway 2010). Numerical Methods in Geotechnical Engineering presents the latest developments relating to the use of numerical methods in geotechnical engineering, including scientific achievements, innovations and engineering applications related to, or employing, numerical methods. Topics include: constitutive modelling, parameter determination in field and laboratory tests, finite element related numerical methods, other numerical methods, probabilistic methods and neural networks, ground improvement and reinforcement, dams, embankments and slopes, shallow and deep foundations, excavations and retaining walls, tunnels, infrastructure, groundwater flow, thermal and coupled analysis, dynamic applications, offshore applications and cyclic loading models. The book is aimed at academics, researchers and practitioners in geotechnical engineering and geomechanics.
Anderson, Loren Runar et al "HISTORICAL SKETCH" Structural Mechanics of Buried Pipes Boca Raton: CRC Press LLC,2000 429 APPENDIX D HISTORICAL SKETCH Pipeline engineering dates from prehistory The ganats of ancient Persia were underground tunnels bored back under the mountains to collect fresh water for the cities on the plains The catacombs of Egypt were remarkable underground conduits Medieval Paris and London had brick-lined sewers The subway tunnels of Saint Louis, long since abandoned, are rediscovered as engineers study light rail systems The technology of buried pipes of the past arose from experience — including failures The modern approach to buried pipeline engineering began in the early 1920s by Anson Marston, Dean of Engineering at Iowa State College Each spring he saw the plight of Iowa farmers as they bogged down in quagmires of mud on the rural roads His concern became a rallying cry, "Let's get Iowa out of the mud." Because of this effort, Marston was named the first Chairman of the Highway Research Board As such, he reasoned, correctly, that the first step toward adequate roads was drainage That meant buried drain pipes, and a procedure for designing buried drain pipes He proposed a theory for predicting soil loads on buried rigid pipes The strengths of the pipes were determined by crushing samples of the pipe between parallel plates For design, the soil loads on the buried pipes had to be less than the parallel plate loads that caused failure But how much less? Tests were needed Marston assigned the testing to a student, M.G Spangler, who was instructed to bury samples of rigid pipe and measure the soil loads on them The objective was to relate parallel plate loads to soil loads at pipe failure, and thus provide a design procedure for highway pipes and culverts During the time Spangler was testing rigid pipes, flexible corrugated steel pipes appeared on the market Spangler realized that for flexible pipes, a parallel plate test was not representative of field conditions In the field, soil at the sides of the buried pipe supports the pipe and resists deflection So Spangler derived the Iowa Formula for predicting ©2000 CRC Press LLC the ring deflection of buried flexible pipes The formula was based on: the Marston soil load on the pipe; ring stiffness and soil stiffness which Spangler called the modulus of passive resistance of soil The Iowa Formula required a number of adjustments such as deflection time lag factor, bedding angle, and load factors The load was soon changed from the Marston load to prismatic soil load plus the influence of live load Both soil and pipe were assumed to be elastic The boundaries included a plane of equal settlement which was affected by trench or embankment condition, and positive or negative projection The Iowa Formula was published in 1941 in the Iowa Engineering Experiment Station Bulletin 153 Spangler was convinced that buried corrugated steel culverts invert at the top when ring deflection is about 20% So he applied a safety factor of four and proposed that buried flexible pipes be limited to 5% ring deflection Kelly of Armco Corporation attempted to apply the Iowa Formula to corrugated steel pipes But the formula broke down With 5% ring deflection and all else constant in the formula, Kelly plotted height of soil cover as a function of pipe diameter The result was that in diameters over ft, the allowable height of soil cover increased as the diameter increased This seemed irrational The Iowa Formula was abandoned In 1957, Spangler's student R.K Watkins, discovered that Spangler's modulus of passive resistance of soil had to be redefined in order to be a correct property of material A modified Iowa Formula overcame the irrationality demonstrated by Kelly It was published in 1958 in the Proceedings of the Highway Research Board Pipeline agencies commenced to publish values for the corrected soil modulus, now called the modulus of soil reaction Published values were excessively conservative They became a catch-all for the many assumptions in the Iowa formula, and for 430 STRUCTURAL MECHANICS OF BURIED PIPES incautions in installation Published values of the soil modulus, at best, yielded only a rough, conservative estimate of ring deflection From field and laboratory testing, Watkins found the modulus of soil reaction to be elusive and undependable — a sidewise modulus based on vertical soil loading It was not constant E-prime is a function of depth of soil cover (confinement) and ring stiffness Similar findings were reported by Duncan, Molin and others The many factors and assumptions required to solve the Iowa Formula made the prediction of ring deflection less precise than direct prediction of ring deflection based on vertical compression of the sidefill soil Ring deflection is related to vertical soil compression and to the ratio of soil stiffness to ring stiffness Soil stiffness is found by standard laboratory compression tests Ring stiffness is a form of the spring constant for a diametral line load on the ring For flexible pipes buried in good granular soil, the stiffness ratio is so large that the influence of ring stiffness is negligible and the soil alone determines ring deflection; Research at USU showed that: Ring deflection of buried flexible pipes is equal to (or less than) vertical compression of the embedment (the sidefill) For high soil cover, pipe "failure" is not necessarily ring deflection (Spangler's 20%), nor is it necessarily Marston's parallel plate load The pipe wall can buckle or crush by ring compression at deflection less than 20% In fact, the wall can buckle or crush when deflection is zero A pipe with high ratio of wall strength to stiffness, such as a thin-wall steel pipe, may buckle at less than 20% ring deflection A pipe with low ratio of wall strength to stiffness, such as plastic pipe, may crush at less than 20% ring deflection These observations have since been confirmed by finite element analyses, and by tests — especially on large diameter buried flexible steel pipes For flexible pipes in select soil envelopes, engineers ©2000 CRC Press LLC can predict ring deflection as a function of vertical soil strain Whoever uses the Iowa Formula must reduce the number of variables by substituting average or assumed values for those variables that have the least effect on the result The Iowa Formula is not a procedure for design It is an approximate procedure for predicting ring deflection Ring deflection has proven to be an important limit to be specified Other important performance limits include soil slip, ring collapse, and ring compression stress as reported by White and Layer Ring compression is described in Chapter Other models for analysis have been proposed by Hoeg, Luscher, Meyerhof, and others Most are based on elastic theory An elegant analysis of elastic soil embedment was presented by Burns, J.Q., and Richards, R.M., Attenuation of stresses for buried cylinder s , Proceedings of the Symposium on Soil Structure Interaction, University of Arizona, Sept 1964 Both pipe and soil were assumed to be elastic One analysis was for full bond between soil and pipe, and the other was for zero friction between soil and pipe They provide a "feel" for pipe-soil interaction Performance limits require special analysis for a variety of embedment conditions, such as backpacking and encasements, and for new pipe materials and configurations — especially plastics Stresses in plastic pipes relax under constant strain, and creep (even to a long-term regressed strength) under constant stress Clearly, pipe-soil interaction becomes complex Basic principles of engineering mechanics of materials are proving to be the most dependable tools for analysis Worst-case conditions are assumed Greater precision is not justified because of imprecisions in soils and in installations Because of their versatility and corrosion resistance, plastic pipes have increased and dominated some buried pipe markets since World War II Bombing of German cities destroyed not only the industries APPENDIX D HISTORICAL SKETCH that provided steel for guns (and pipes), but also the water supply pipelines that served the cities In desperation, one quick remedy seemed to be PVC pipes The Germans had led in processing and fabricating PVC (polyvinyl-chloride) PVC pipes were successful Other plastic pipes soon came on the market ©2000 CRC Press LLC 431 With computers available for complex pipe analyses, with new pipe configurations and materials on the market, and with an urgent and sustained need for buried pipes, present-day technology is only a primer for future design of buried pipes ... from experience — including failures The modern approach to buried pipeline engineering began in the early 1920s by Anson Marston, Dean of Engineering at Iowa State College Each spring he saw the... buried in good granular soil, the stiffness ratio is so large that the influence of ring stiffness is negligible and the soil alone determines ring deflection; Research at USU showed that: Ring... ratio of soil stiffness to ring stiffness Soil stiffness is found by standard laboratory compression tests Ring stiffness is a form of the spring constant for a diametral line load on the ring For