Dynamic stiffness of pile groups - approximate solutions

207A 865291 Buried pipeline in a soil liquefaction environment Yaw-Huei Yeh; Leon Ru-Liang Wang Proc 5th Engineering Mechanics Division Speciality Conference, Wyoming, 1-3 Aug 1984 VI, P356-359. Publ New York: ASCE, 1984 The effects of soil liquefaction on the stresses and strains in a buried pipe subject to earthquake induced ground motions have been investigated. The pipeline is subjected to induced tensile and compressive stresses which are generally small. If liquefaction occurs, however, the support of the soil disappears. Failure of the pipe can occur in non-liquefied zones, due to bending deformation induced by the pipeline. 865292 Seismic response of pile supported cooling towers Bor-Jen Lee; Gould, P L Proc 5th Engineering Mechanics Division Speciality Conference, Wyoming, !-3 Aug 1984 VI, P360-363. Publ New York: ASCE. 1984 The dynamic soil-structure interaction of a shell building supported by long piles in a soil medium modelled as layered viscoelastic with constant hysterctic damping is examined by finite element analysis. Four foundation configurations are considered, fixed base (rock founded), 334 piles, 167 piles and flexible base. Some numerical results of practical significance are presented and discussed. 865293 Dynamic stiffness of pile groups - approximate solutions Salinero, I S; Roesset, J M; Tassoulas, J L Proc 5th Engineering Mechanics Division Speciality Conference, Wyoming,, 1-3 Aug 1984 VI. P364-367. Publ New York: ASCE. 1984 Dynamic analysis of complete pile foundations can be expensive and time consuming. Four analyses which make simplifying assumptions are presented. An analysis which combines all four assumptions is discussed, and is seen to be particularly efficient as all terms can be obtained in closed form. 865294 Suitability of the finite element method for the examination of careful blasting close to a building (In Swedish) Almgren, B Swedish Detonic Research Foundation report DS 1985: 3, 9 Sept 1985.29P Accurate vibration measurements were made on the foundation and further up the walls of a building which was subject to so-called careful blasting. Measured signals at the foundation were used as the boundary condition for dynamic finite element analysis of the building. For the first three periods of the signal, measured and predicted rise time and frequency content at the measurement point on the wall were in good agreement, but overall agreement was not good enough to suggest the analysis was worthy of adoption. The reasons for lack of correlation are concluded to be lack of damping in the model, simplification of the model to suit available computing power and lack of exact knowledge of material properties. A larger computer and more elaborate model are necessary to predict dynamic behaviour of the building after the initial stages.

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Underground Excavations See also: 865008

865295 Pipeline breakout from sea floor under wave action Foda, M A Appl Ocean Res V7, N2, April 1985, P79-84 A study of the stability under wave action of a pipeline laid half buried on the sea floor. A wave induced lifting force acts to detach the pipe from the sea bed, and mud suction resistance at the pipe/soil interface acts to hold it in place. Pipe equilibrium is coupled with the response of the sea bed, which is modelled a a poroelastic medium, according to Blot. Breakout conditions are evaluated for typical pipe, sea bed and wave parameters.

865296 Seepage force on a pipeline buried in a pore.elastic seabed under wave Ioadings Cheng, A H D; Liu, P L F Appi Ocean Res I/8. NI, Jan 1986, P22-32 Wave induced uplift forces on an unsupported buried pipeline in sea bed sediment have been calculated. The sea bed is modelled according to the Blot model, which couples an elastic soil specimen and a Darcy flow with compressible pore water. Equations for pore pressure and soil stresses are solved using the boundary integral equation method. Numerical results are compared with laboratory data and found to be in reasonable agreement. With realistic parameters, uplift seepage force on the pipeline can be as much as 60% of the displaced water weight if the pipeline is located in the pore water boundary layer.

Geological factors of importance in underground excavations 865297 Study of the role of geological factors in the stability of underground quarries (In French) Beaufrere, C lnt Assoc Engng Geoi Bull N32. Dec 1985, P11-24 It is difficult to evaluate the stability of underground quarries. In order to determine the factors and to explain the mechanisms which are responsible for stability, a study was undertaken to determine the heterogeneities and discontinuities of the environment and of the limestone in four underground quarries in the Gironde Region of France. The major influences of porosity and the clay mineral content on the mechanical behaviour of limestone are demonstrated by statistical analysis. By taking the geological factors into consideration, a good understanding of the creep and fatigue behaviour of limestone, whose role seems to be predominant in underground quarry stability, is arrived at.

~© 1986 Pergamon Journals Ltd. Reproduction not permitted