The Axial Resistance of Nondisplacement Piles

Author(s):  
Rodrigo Salgado
Keyword(s):  
Author(s):  
John Barrett ◽  
Ryan Phillips

Abstract Interdependence between pipe-soil interaction springs in a pipe stress analysis should be considered. This example focused on a single pipe configuration “wished” in place in a clay soil. A conventional pipe stress analyses often idealizes the pipe soil interaction with a beam-spring finite element model where independence is assumed between reactions in axial, lateral and vertical directions. There is however interdependence between these springs as recognized in recent Pipeline Research Council International (PRCI) guidelines. For a frictional interface, axial resistance can be much higher than indicated by PRCI guidelines when accounting for increased lateral and vertical bearing pressure. At the same time, lateral and vertical capacities are shown to be reduced in comparison to pure vertical and lateral loading directions. This paper highlights the development of a 3D soil-spring interaction model based on a continuum finite element analysis approach. By developing a soil capacity envelope based on 3D continuum modeling, updated soil springs can reflect modified capacities depending on the direction of pipe movement. For the landslide scenarios considered in application of the model, the directional dependency is shown to change the accumulated plastic strain profile in the pipe.


Géotechnique ◽  
2020 ◽  
Vol 70 (2) ◽  
pp. 138-152 ◽  
Author(s):  
Fei Han ◽  
Eshan Ganju ◽  
Monica Prezzi ◽  
Rodrigo Salgado ◽  
Mir Zaheer
Keyword(s):  

Author(s):  
Gert Greeuw ◽  
Henk den Adel ◽  
Aad L. Schapers ◽  
Evert J. den Haan

2016 ◽  
Vol 114 ◽  
pp. 58-65 ◽  
Author(s):  
Hai-lei Kou ◽  
Wei Guo ◽  
Ming-yi Zhang ◽  
Yi-qing Xu
Keyword(s):  

1982 ◽  
Vol 33 (4) ◽  
pp. 665 ◽  
Author(s):  
PS Cornish

The effects of surface-sowing on root type, number and xylem radius were studied in relation to the seedling growth and survival of ryegrass and phalaris. Under optimal conditions in a growth cabinet, both species produced primary and lateral seminal roots, nodal roots and, in the absence of light, a subcoleoptile internode (s.c.i.). Phalaris had fewer lateral seminal roots and, in this species, internodal roots occurred along the s.c.i. Surface placement per se had no effect on any of the measured parameters of root development, but surface drying prevented nodal root primordia from extending, even when plants were otherwise supplied with water. This effect of surface drying on nodal root development was confirmed in a glasshouse study using undisturbed soil cores (30 by 60 cm) to simulate field conditions. Phalaris was less likely than ryegrass to produce nodal roots after surface sowing. The effective xylem radius (re) of the primary seminal root was 7.9 �m in ryegrass and 11.6 �m in phalaris. Calculations using the Poiseuille equation indicated that the axial resistance to water flow through these roots would greatly restrict seedling water uptake and growth in the absence of other roots. Lateral seminal roots and internodal roots had small vessels which could not significantly reduce the axial resistance to flow. Good seedling water relations in both species therefore depend on early development of the nodal roots which contain large xylem vessels (re > 16 �m). It was concluded that the effect of soil-surface drying on nodal root development was likely to account for some cases of poor vigour and survival of surface-sown grasses.


1983 ◽  
Vol 244 (1) ◽  
pp. H3-H22 ◽  
Author(s):  
M. S. Spach ◽  
J. M. Kootsey

It has long been appreciated that cardiac muscle is composed of individual cells connected by low-resistance connections, but most concepts of cardiac impulse conduction have been based on a simplified model of propagation assuming continuously uniform intracellular resistivity in the direction of propagation. In this article we describe the development of the application of the theory of continuous media to propagation in cardiac muscle and review some of the successes achieved with this theory. New evidence is cited that propagation in cardiac muscle often displays a discontinuous nature. We consider the hypothesis that this previously unrecognized aspect of propagation can be explained by discontinuities in axial resistance related to known structural complexities of cardiac muscle. A major implication is that the combination of discontinuities of effective axial resistivity at several size levels can produce a wide variety of complex abnormalities of propagation, including most currently known cardiac conduction disturbances that have been considered to require spatial nonuniformity of membrane properties.


1987 ◽  
Vol 38 (3) ◽  
pp. 513 ◽  
Author(s):  
AP Hamblin ◽  
D Tennant

Total root length per unit ground area (La) is often considered to be directly related to the amount and rate of water uptake. Experiments were conducted to compare the water use of spring wheat, barley, lupin (L. angustifolius) and field pea on four differing soil types in drought-stressed conditions. The La values of cereals were consistently five to ten times as large as those of grain legumes, whereas the aboveground biomass was sim~iar and never greater than twice that of the grain legumes. Growing-season water loss (WL) from the soil profile was very similar for wheat and lupins, despite this big difference in root length. Soil evaporation may have been greater under lupins, but when crop water uptake was compared for the period when leaf area was greatest, rates of change in soil water content within the root zone were still similar and were not well correlated with La. Specific root water uptake (Ur) was consistently greater for lupin than wheat. Maximum rooting depth was better correlated with WL than was La in all cases. Higher Ur values in lupin and pea may be related to their large and abundant metaxylem vessels, which give much lower axial resistance than in cereals. These results provide strong evidence for genotypic variation in root morphology, density and root extension between dicotyledenous and monocotyledenous species. They also indicate that La is not necessarily the root morphological characteristic most responsible for efficiency of water uptake in drought-stressed environments.


2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Yi Shen ◽  
Xuyan Hou ◽  
Yiwei Qin ◽  
Shengyuan Jiang ◽  
Zongquan Deng
Keyword(s):  

2018 ◽  
Vol 4 (5) ◽  
pp. 916
Author(s):  
Hamza Mahdi Salman ◽  
Mohannad Husain Al-Sherrawi

The reinforced concrete column is designed to have a nominal axial resistance. Under different conditions like errors in design, and changing the use of the building from residential to public or storage (extra live loads), the reinforced concrete column will not be able to sustain the desired applied load, and the strengthening is required. This paper presents a finite element model to simulate and investigate the behavior of adding steel jacket to a preloaded and non-damaged reinforced concrete column. Depending on the loading state of the non-strengthened reinforced concrete column and the purpose of adding the steel jacket, two possible cases have been studied. In the first case, which is suitable to investigate the reinforced concrete column with design errors, the steel jacket has been added to the unloaded reinforced concrete column; while the second case is suitable for adding steel jacket to the pre-loaded non-damaged reinforced concrete column. The finite element model was carried out using the ABAQUS/standard v. 6.13 software. The results obtained by the proposed finite element model showed fairly good agreement with the existing experimental and analytical results.


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