Behavior of pile foundations supporting tension leg platforms

i 79A 9O3387 Pull-out tests on a grouted driven pile in calcareous sands Barthelemy, H; Martin, R; Nauroy, J F; Le Tirant, P; de Medeiros, C J Proe 6th International Symposium on Offshore Engineering, Rio de Janeiro, 24-28 August 1987 V6, P243-255. Publ London: Pentech, 1988 The grouted driven pile was proposed as a cheaper alternative to the drilled and grouted pile in calcareous soils. Initial tests using external grouting showed promising increase in soil friction. Tests were then carried out using piles pre-equipped with internal grout pipes at several levels. Effects of grouting through one hole then subsequently through others on pullout resistance were examined. Piles were cycled below failure load then up to failure load to assess degradation of pile friction with cycling. 903388 Impact of pile inclination on the design of platform foundations van Zandwijk, C; Beurze, R S Proc BOSS'88, Trondheim, June 1988 VI, P343-339. Publ Trondheim: Tapir, 1988 In classical platform design, foundation piles are set at the angle of the legs or frame for ease of installation and to minimise the shear load. Recent calls for vertical piles are in conflict with this philosophy. An alternative solution, placing the piles at an intermediate angle, is proposed. The sensitivity of foundation stiffness to natural variation of soil properties in analysed, taking into account uncertainties in the soil model and influence of soil elasticity on group effects. Optimisation of pile batter in strength and stiffness dominated designs is examined. Effective foundations can be designed now hammers are available which allow driving at the specified inclination. 903389 Drivability of large pipe piles analysed by case records Lango, H; Janbu, N; Bernardes, G P; Tjelta, T I Proc BOSS'88, Trondheim, June 1988 VI, P361-378. Publ Trondheim: Tapir, 1988 Driving records from 3 offshore and 2 onshore sites with soils ranging from soft clays and silts to dense sand and moraine including hard clay layers are analysed. Driveability predictions based on an energy equation and on a more sophisticated wave equation analysis (WEAP) are compared with field records. Predicted and observed values agree well if excess pore pressure during driving is taken into account. Energy and wave equation predictions agree well if the damping term in WEAP is neglected. 903390 Behaviour of model grouted piles in cemented and uncemented calcareous soils Allman, M A; Lee, C Y; Poulos, H G Proc BOSS'88, Trondheim, June 1988 VI. P379-391. Publ Trondheim: Tapir, 1988 Results of static and load- and displacement-controlled cyclic tests on model drilled and grouted piles are reported. They indicate that cementation significantly increases static skin friction capacity, reduces susceptibility to cyclic degradation of pile friction in pre-peak load controlled cycling, and increases potential for pile friction degradation in post peak cycling, when ultimate skin friction possibly degrades to the value for uncemented soil. Results are consistent with field observations over a wide range of load levels.

903391 Probabilistic assessment of the foundation collapse strength of piled offshore platforms Hamilton, J M; Murff. J D Proc BOSS'88, Troadheim, June 1988 VI, P393-408. Publ Trondheim: Tapir. 1988 The first order second-moment formulation of Ang and Tang (1984) was used to compute reliability of offshore platforms against collapse failure. Axial and lateral soil resistance, plastic moment capability of piles, and gravity and environmental loads are considered as random variables. The sensitivity of reliability calculations to uncertainty in random variables is studied for various modes of foundation collapse. The reliabilities of 3 piled steel jacket platforms are evaluated and compared with those from industry experience. 903392 Behavior of pile foundations supporting tension leg platforms Malek, A M; Azzouz, A S; Baligh, M M; Whittle, A J Proe BOSS'88, Trondheim, June 1988 VI, P433-447. Publ Trondheim: Tapir, 1988 Piles supporting tension leg platforms are subject to sustained tensile loads and superimposed cyclic shear loading. To investigate the behaviour of foundation clays during storm loading, a series of undrained, stress controlled, cyclic direct shear tests was carried out on normally consolidated Boston Blue Clay. Results are compared with those of other clays under similar conditions. A simplified method to predict the performance of a rigid, rough pile supporting a tension leg platform is proposed.

Dams and embankments 903393 Test embankment dam of fracture grouting. Technical note Chen, J Y; Zhang, S L J Geotech Engng Die ASCE VIIS, Nil, Nov 1989, P!6681672 Fracture grouting has been used in China to seal leaks in poorly compacted cohesive fill embankments. It has been suggested that its mechanism is formation of a vertical grout wall parallel to the dam axis and along the minimum principal stress plane, and intrusion of grout into seepage channels across the dam axis. Tests on an abandoned dam have allowed collection of direct evidence to confirm this supposition. Based on these results, methods of controlling the dam grouting are discussed. 903394 Seismic monitoring around large dams at Nagarjunasagar and Srisailam in the Southeastern part of Peninsular India Rastogi, B K Phys Earth Planet later 1/58, NI, Nov 1989, P35-43 Seismicity around the two dams, approximately 60kin apart on the Krishna river, Andhra Pradesh, has been monitored. The first was filled over the period 1968-1974, the second during 1975-1984. Sporadic weak tremors monitored up to 1985 were assumed due to regional seismicity, not reservoir induced. Four weak tremors have been recorded since then along geologically active faults. Because of the presence of these faults in a region of fractured and jointed rocks and low level prevailing seismicity,the area is prone to induced seismicity and should be carefully monitored.

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