Modeling cover-collapse sinkhole based on the theory of shells

2019 ◽  
Vol 08 (01) ◽  
pp. 1850028
Author(s):  
Zhen Liu ◽  
Cuiying Zhou ◽  
Zichun Du ◽  
Dingli Su ◽  
Jieming Li ◽  
...  
Keyword(s):  
Equilibrium State ◽  
Limit Equilibrium ◽  
Critical Factors ◽  
Karst Terrain ◽  
Collapse Sinkhole ◽  
Limit Equilibrium State ◽  
Soil Arch ◽  
Collapse Phase ◽  
Theory Of Shells

The shape and height of a natural balanced soil arch are two of the critical factors for the development of a sinkhole. The exposure of the natural balanced soil arch can be described as the initiation of the surface-collapse phase of the cover-collapse sinkhole in karst terrain. In this paper, by simplifying the natural balanced soil arch as a thin shell in a limit equilibrium state, a theoretical model is developed using the nonmoment theory of rotary shells with the shape and height of the natural balanced soil arch derived based on the Protodyakonov’s theory. First, the developed model is validated using a case study (a cover-collapse sinkhole occurred in Guizhou, China). It demonstrates that the shell theory used in this study can describe the equilibrium state of a natural balanced soil arch reasonably well. After model validation, a series of numerical simulations are then carried out to investigate the critical factors which govern the collapse of a sinkhole. The results show that buried depth serves as a compulsory condition for the formation of the natural balanced soil arch. Furthermore, it shows that a buried depth less than six times of the radius of a cave could result in the formation of a natural balanced soil arch in the cone surface.

A Further Study on Soil Slope Stability Analysis by Finite Element Slip Surface Stress Method

2012 ◽  
Vol 204-208 ◽  
pp. 492-501
Author(s):  
Hong Jun Li ◽  
Yan Yi Zhang ◽  
Zu Wen Yan
Keyword(s):  
Shear Strength ◽  
Equilibrium State ◽  
Surface Stress ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Strength Reduction ◽  
Engineering Practice ◽  
Limit Equilibrium State ◽  
Ultimate Limit ◽  
Sliding Force

In this paper, it proves that the necessary and sufficient condition for the potential sliding body reaching the ultimate limit equilibrium state is that the summation of shear stresses along the sliding surface equals to that of resistant shear strength. Based on the rigorous theory analyses and derivations, it is clearly shown that the definition of factor of safety (FOS) in the slip surface stress method (SSSM) is irrelevant with the shape of slip surface. Thus, the authors demonstrate that the FOS of noncircular slip surface can also be defined as the ratio of the sum of resistant sliding force along slip surface to that of sliding force. Furthermore, the physical meaning of the FOS in the SSSM, which can be taken as the average evaluation of the strength reduction coefficient that makes the sliding body reach the ultimate limit equilibrium state along the slip surface in nature, is formulated on the basis of strength reserving theory rather than the overloading theory like that in the Limit Equilibrium Method (LEM) and the Shear Strength Reduction Method (SSRM). Finally, the factors of safety (FOS) and the locations of critical failure surfaces obtained by the SSSM, LEM and SSRM are compared for various geotechnical practices. It is found that the SSSM can achieve precise and reasonable stability assessments for the soil slopes on the basis of actual stress field. Consequently, compared with the LEM and SSRM, the SSSM is demonstrated to be effective and efficient alternative approach for routine analysis and design in geotechnical engineering practice with a high level of confidence.

Supergene degeneration opposes polymorphism: The curious case of balanced lethals

2021 ◽  
Author(s):  
Emma Berdan ◽  
Alexandre Blanckaert ◽  
Roger K Butlin ◽  
Thomas Flatt ◽  
Tanja Slotte ◽  
...  
Keyword(s):  
Equilibrium State ◽  
Balancing Selection ◽  
Mutation Accumulation ◽  
Small Population ◽  
Quasi Equilibrium ◽  
Deleterious Mutations ◽  
Critical Factors ◽  
Critical Aspect ◽  
Allopatric Divergence

Supergenes offer some of the most spectacular examples of long-term balancing selection in nature but their origin and maintenance remain a mystery. A critical aspect of supergenes is reduced recombination between arrangements. Reduced recombination protects adaptive multi-trait phenotypes, but can also lead to degeneration through mutation accumulation. Mutation accumulation can stabilize the system through the emergence of associative overdominance (AOD), destabilize the system, or lead to new evolutionary outcomes. One such outcome is the formation of balanced lethal systems, a maladaptive system where both supergene arrangements have accumulated deleterious mutations to the extent that both homozygotes are inviable, leaving only heterozygotes to reproduce. Here, we perform a simulation study to understand the conditions under which these different outcomes occur, assuming a scenario of introgression after allopatric divergence. We found that AOD aids the invasion of a new supergene arrangement and the establishment of a polymorphism. However, this polymorphism is easily destabilized by further mutation accumulation. While degradation may strengthen AOD, thereby stabilizing the supergene polymorphism, it is often asymmetric, which is the key disrupter of the quasi-equilibrium state of the polymorphism. Furthermore, mechanisms that accelerate degeneration also tend to amplify asymmetric mutation accumulation between the supergene arrangements and vice versa. As the evolution of a balanced lethal system requires symmetric degradation of both arrangements, this leaves highly restricted conditions under which such a system could evolve. We show that small population size and low dominance coefficients are critical factors, as these reduce the efficacy of selection. The dichotomy between the persistence of a polymorphism and degradation of supergene arrangements likely underlies the rarity of balanced lethal systems in nature.

scholarly journals Critical Factors Influencing CO2 Capture Cost, a Case Study

2014 ◽  
Vol 63 ◽  
pp. 7298-7306 ◽  
Author(s):  
Ragnhild Skagestad ◽  
Agnieszka Lach ◽  
Nils Røkke ◽  
Nils Henrik Eldrup
Keyword(s):  
Co2 Capture ◽  
Critical Factors ◽  
Factors Influencing

scholarly journals Staffing System Management: Evidences from Singapore

2017 ◽  
Vol 7 (2) ◽  
pp. 136
Author(s):  
Mussie T. Tessema ◽  
Kubilay Gok ◽  
Alex Ngoma ◽  
Mengsteab Tesfayohannes ◽  
Gerry V. Fernando
Keyword(s):  
Public Service ◽  
Research Direction ◽  
Future Research ◽  
System Management ◽  
Critical Factors ◽  
Organization Level ◽  
The World ◽  
Practical Implications

This paper uses Singapore as a case study to illustrate how staffing policies and practices affect the quality of the workforce which ultimately influence performance at employee and organization level. It reveals that Singapore public service has been able to put in place most of the ‘critical factors’ for an effective staffing system management. The presence of those critical factors have played an important role in making Singapore to be one of the most effective public services in the world. Finally, it forwards theoretical and practical implications of the study and future research direction.

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