ALBERT

Description: A theoretical solution for the progress of consolidation of a saturated soil layer subjected to cyclic loading is obtained.Consolidation, proceeding inwards from the drainage face, is slower than consolidation under an equivalent sustained loading because positive and negative pore-water pressures, produced during the loaded and unloaded portion of the cycle, cause flow of water from and into the soil. An equilibrium, or finalized, consolidation ratio is reached which is dependent on the pattern of loading cycle; it is not possible to reach 100% consolidation under cyclic loading.

Description: The method of control of water in open excavations by pumping from sumps, from deep wells, or from well points is such an accepted practice that sometimes little attention is given to its complex and difficult hydraulic nature.This paper describes the causes leading to a hydraulic failure of a 15 m deep temporary sheeted cofferdam required to found a concrete slab for a pump house. The construction of the new pump house was for the extension of facilities of a sewage treatment plant. The piping failure caused a considerable construction delay and it also served as a field case to reassess the construction procedure of the excavation and the inadequacy of the well point installation.

Description: The paper is divided into two parts. The first part deals with the systematic program of measurements undertaken on an open braced cut in dense sand at the Greenway Pollution Control Centre in London, Ontario. In the second part, the experimental data are analyzed and a new solution is presented based on Dubrova's analysis, which related qualitatively and quantitatively the active earth pressure distribution to the mode of deformation of a retaining structure.The roughly L-shaped excavation measured 68 × 42 ft (20.7 × 12.8 m) for the longest leg, the other leg was 30 × 23 ft (9.1 × 7.0 m). The temporary bracing system consisted of interlocking steel sheet piles (Larssen IIIN), and wales and struts from wide-flanged steel sections. The maximum depth of the cut was 50 ft (15.2 m) below ground elevation of 722 ft (220.1 m). The soil consisted of fine uniform dense sand having a relative density varying from medium to very dense. The natural water level was approximately 20 ft (6.1 m) below the ground surface prior to construction.The instrumentation program was carried out during the 6-month construction period (January–June 1964) and consisted of measuring: (1) The strut loads with a mechanical strain indicator (Whitmore gauge) over 8 in. (20.3 cm) gauge lengths, (2) The deformation of the north wall in a horizontal and a vertical plane, (3) The water levels and water pressures from borehole and standpipe observations, and (4) The active and passive earth pressures over the cut with 'Geonor vibrating-wire pressure transducers mounted flush on two adjacent sheet piles of the north wall.Field and laboratory tests supplied the necessary soil data.Comprehensive measurements of this kind in deep cuts in sand, prior to this London investigation, had only been made in Berlin, Munich, and New York. But at London, for the first time the actual distribution of earth pressures in sand were measured on a full-scale braced wall.The analysis of the experimental data showed that the earth pressure distribution can be approximated by the extended Dubrova’s solution. The agreement between the total active earth pressure obtained from the pressure cells and the corresponding Coulomb values varied from excellent (upper bound) to good (lower bound).An experimental relationship between the horizontal soil strain and the variation of K-values over the depth of the cut was established.The different theories for predicting Ko-values do not seem to apply to over consolidated dense sand deposits. The experimental Ko-values, rather, agree with other published experimental values for similar soils.The strut load readings were somewhat erratic, not necessarily corresponding to the excavation progress. The total strut loads were lower than the corresponding forces from the earth pressure cells or the corresponding Coulomb values.

Description: A preliminary investigation has been conducted to explore the potential utilization of neutron radiography for the in vitro examination of soils contained within sampling tubes. Radiographic images obtained by such means have been found to provide indications of changes in soil type and details of soil structure which are distinct from images obtained by conventional X-ray radiographic means.