Experimental and theoretical studies on installation torque of screw anchors

1991 ◽  
Vol 28 (3) ◽  
pp. 353-364 ◽  
Author(s):  
Ashraf Ghaly ◽  
Adel Hanna
Keyword(s):  
Soil Mechanics ◽  
Testing Procedure ◽  
Dense Medium ◽  
Theoretical Studies ◽  
Uplift Capacity ◽  
Factors Affecting ◽  
Sand Surface ◽  
Pullout Load ◽  
Upward Displacement ◽  
Experimental And Theoretical Studies

Experimental and theoretical studies on the torque required to install screw anchors in sand are presented. Tests were conducted on five models of screw anchors with different geometry to study the effect of the shape of the screw element on the performance of the anchor during installation. Anchors were installed into prepared layers of dense, medium, and loose sand. An experimental setup was instrumented to allow the measurement of the total pullout load, the upward displacement, the sand surface deflection, installation torque value, and the stress development in the sand layer during all phases of the testing procedure. Special tests were conducted on coloured-layered sand to examine the effect of the installation procedure on the sand deposit and to define the sand wedge involved in resisting the installation of the screw anchor. Based on the results of the experimental investigation, the factors affecting the value of the installation torque were identified. A theoretical model was developed, from which the required installation torque value can be predicted. A torque factor was established in terms of the parameters affecting the torque value, and a correlation between this factor and the uplift capacity factor was proposed. From this correlation, the uplift capacity of a screw anchor can be determined from the measured installation torque value. A comparison between theoretical and experimental results showed good agreement. Also, reasonable agreement was observed when the present theoretical results were compared with the available field results from other investigations. Key words: anchorages, anchors, bearing capacity, helical anchors, models, sand, screw anchors, screw helical anchors, soil mechanics, torque, uplift capacity.

Model investigation of the performance of single anchors and groups of anchors

1994 ◽  
Vol 31 (2) ◽  
pp. 273-284 ◽  
Author(s):  
Ashraf Ghaly ◽  
Adel Hanna
Keyword(s):  
Failure Mechanism ◽  
Load Distribution ◽  
Dense Medium ◽  
Unit Weight ◽  
Experimental Investigations ◽  
Experimental Setup ◽  
Uplift Capacity ◽  
Sand Surface ◽  
Pullout Load ◽  
Upward Displacement

Experimental investigations on the performance of single and groups of vertical screw anchors installed in dense, medium, and loose sands are presented. An experimental setup was instrumented to allow the measurement of the total pullout load, upward displacement, sand surface deflection, and stress development in the sand layer during all phases of testing. A sand placing technique was developed and utilized over all the testing program to ensure reproducibility of the predetermined unit weight. Stresses measured within sand deposits indicated that the tested sands were overconsolidated due to the application of mechanical compaction. Special tests were conducted on colored–layered sand to define the nature of the failure mechanism. The results of these tests, together with the measurements of the deflection of the sand surface, were employed to establish the shape of the rupture surface which could be represented by a segment of a logarithmic spiral. Groups of three, four, six, and nine anchors were tested in this investigation. The effect of installation depth, spacing between anchors, and sand characteristics on the ultimate pullout load of the group was examined. The experimental setup was instrumented to allow the measurement, of the total pullout load of the group as well as that of individual anchors in the group. Load distribution among the anchors of a group is discussed in terms of anchor location and the applied load level. At failure, all anchors contribute almost equally to the uplift capacity. Group efficiencies were calculated and compared. An installation procedure was proposed to avoid differential upward displacement during the uplifting process and to provide uniform load distribution on the different anchors of the group. Key words : anchors, failure mechanism, group action, model tests, sand, uplift capacity.

scholarly journals Experimental and Theoretical Studies of the Factors Affecting the Cycloplatination of the Chiral Ferrocenylaldimine (SC)-[(η5-C5H5)Fe{(η5-C5H4)–C(H)=N–CH(Me)(C6H5)}]

Inorganics ◽  
2014 ◽  
Vol 2 (4) ◽  
pp. 620-648 ◽  
Author(s):  
Concepción López ◽  
Ramón Bosque ◽  
Marta Pujol ◽  
Jonathan Simó ◽  
Eila Sevilla ◽  
...  
Keyword(s):  
Theoretical Studies ◽  
Factors Affecting ◽  
Experimental And Theoretical Studies

The Stabilizing Effect of Pre-Equilibria: A Trifluoromethyl Complex as CF2 Reservoir in Catalytic Olefin Difluorocarbenation

2020 ◽  
Author(s):  
Thomas Louis-Goff ◽  
Huu Vinh Trinh ◽  
Eileen Chen ◽  
Arnold L. Rheingold ◽  
Christian Ehm ◽  
...  
Keyword(s):  
High Selectivity ◽  
Side Reactions ◽  
Theoretical Studies ◽  
Attractive Feature ◽  
Catalyst Recovery ◽  
Wide Range ◽  
Stabilizing Effect ◽  
Experimental And Theoretical Studies

A new, efficient, catalytic difluorocarbenation of olefins to give 1,1-difluorocyclopropanes is presented. The catalyst, an organobismuth complex, uses TMSCF<sub>3</sub> as a stoichiometric difluorocarbene source. We demonstrate both the viability and robustness of this reaction over a wide range of alkenes and alkynes, including electron-poor alkenes, to generate the corresponding 1,1-difluorocyclopropanes and 1,1-difluorocyclopropenes. Ease of catalyst recovery from the reaction mixture is another attractive feature of this method. In depth experimental and theoretical studies showed that the key difluorocarbene-generating step proceeds through a bismuth non-redox synchronous mechanism generating a highly reactive free CF<sub>2</sub> in an endergonic pre-equilibrium. It is the reversibility when generating the difluorocarbene that accounts for the high selectivity, while minimizing CF<sub>2</sub>-recombination side-reactions.

Strong coupling: resonant effects

2017 ◽  
Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy
Keyword(s):  
Strong Coupling ◽  
Experimental Studies ◽  
Strong Coupling Regime ◽  
Theoretical Studies ◽  
Stimulated Scattering ◽  
Quantum Theories ◽  
Pump Probe ◽  
Exciton Polaritons ◽  
Linear Optical Properties ◽  
Experimental And Theoretical Studies

This chapter presents experimental studies performed on planar semiconductor microcavities in the strong-coupling regime. The first section reviews linear experiments performed in the 1990s that evidence the linear optical properties of cavity exciton-polaritons. The chapter is then focused on experimental and theoretical studies of resonantly excited microcavity emission. We mainly describe experimental configuations in which stimulated scattering was observed due to formation of a dynamical condensate of polaritons. Pump-probe and cw experiments are described in addition. Dressing of the polariton dispersion and bistability of the polariton system due to inter-condensate interactions are discussed. The semiclassical and the quantum theories of these effects are presented and their results analysed. The potential for realization of devices is also discussed.

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