Generalised framework of limit equilibrium methods for slope stability analysis

A generalised framework is proposed in this paper incorporating almost all of the existing limit equilibrium methods of slices for slope stability analysis with general slip surfaces. The force and moment equilibrium equations are derived in terms of the factor of safety and the initially assumed normal stress distribution over the slip surface, multiplied by a modification function involving two auxiliary unknowns. These equations are then analytically solved to yield explicit expressions for the factor of safety. Various assumptions regarding the interslice forces can be transformed into a unified form of expression for the normal stress distribution along the slip surface. An iterative procedure is developed to expedite the convergence of the solution for the factor of safety. Experience to date indicates that the process generally converges within a few iterations. Computation schemes are suggested to avoid numerical difficulty, especially in computing the factor of safety associated with the rigorous Janbu method. The present framework can be readily implemented in a computer program, giving solutions of slope stability associated with a number of conventional methods of slices.published_or_final_versio

Active and passive critical slip fields for cohesionless soils and calculation of lateral earth pressures

A new method of solving earth pressure problems is proposed in this paper within the framework of the limit equilibrium approach. The concept of the critical slip field (CSF) is postulated: the active critical slip field (ACSF) in the active case, and the passive critical slip field (PCSF) in the passive case. Based on the principle of extremum thrust force (which is theoretically consistent with the principle of optimality) in conjunction with the method of slices, a numerical procedure is presented for the determination of such fields and consequently the distribution of earth pressures on retaining walls. For simplicity at this stage, the backfill material is assumed to be a homogeneous cohesionless soil with sloping ground surface carrying uniform and vertical surcharge, while the retaining wall is allowed to be battered, and the strength of the soil may be either fully or partially mobilised. Compared with the rigorous method (i.e. the method of characteristics), the proposed method is simple in principle and easily implemented in a computer program. However, it is more accurate than other approximate techniques and agrees well with available closed-form solutions. A number of examples of ACSF and PCSF are given in this paper, and the validity and efficiency of the proposed method are demonstrated. In addition, it is easy to extend this numerical procedure to obtain more general ACSF and PCSF accomodating non-homogeneous c, Ø soils subject to complicated loading conditions.published_or_final_versio

Developing a critical realist positional approach to intersectionality

This article identifies philosophical tensions and limitations within contemporary intersectionality theory which, it will be argued, have hindered its ability to explain how positioning in multiple social categories can affect life chances and influence the reproduction of inequality. We draw upon critical realism to propose an augmented conceptual framework and novel methodological approach that offers the potential to move beyond these debates, so as to better enable intersectionality to provide causal explanatory accounts of the ‘lived experiences’ of social privilege and disadvantage

Management of Insulinoma using the drug Octreotide. A Case Report and Literature Review

A case report on the drug Octreotide and its use in managing insulinoma

A web of opportunity or the same old story? Women digital entrepreneurs and intersectionality theory

This article critically analyses the manner in which intersectionality and related social positionality shape digital enterprise activities. Despite popular claims of meritocratic opportunity enactment within traditional forms of entrepreneurship, ascribed social characteristics intersect to influence the realisation of entrepreneurial potential. However, it is purported that the emerging field of digital entrepreneurship may act as a ‘great leveller’ due to perceived lower barriers to entry, disembodiment of the entrepreneurial actor and the absence of visible markers of disadvantage online. Using an interpretivist approach, we analyse empirical evidence from UK women digital entrepreneurs which reveals how the privileges and disadvantages arising from intersecting social positions of gender, race and class status are reproduced online. This analysis challenges the notion that the Internet is a neutral platform for entrepreneurship and supports our thesis that offline inequality, in the form of marked bodies, social positionality and associated resource constraints, is produced and reproduced in the online environment

Early expression of MMP-9 predicts recovery of tibialis anterior after sciatic nerve crush injury

Background: The purpose of this study was to assess the expression of molecular markers and epineural blood flow after differing degrees of nerve injury to identify potential tools to predict nerve recovery in a rat sciatic nerve model. Methods: A total of 72 rats were divided into nine groups. Each group was subjected to one of three crush injuries, created by applying one of three vascular clamps for 30 seconds. Vascularity was assessed with laser Doppler flowmetry before and after crush, and at nonsurvival surgery. Nonsurvival surgeries were performed 6 hours, 2 weeks, or 6 weeks later with nerve conduction studies and muscle strength testing. Expression of matrix metalloproteinase 9 (MMP-9) and matrix metalloproteinase 2 (MMP-2) in each nerve was quantified using with enzyme linked immunosorbent analysis. Results: Persistent hyperemia was noted in the zone of injury compared with baseline at 2 weeks and 6 weeks in the groups that displayed incomplete recovery. Expression of MMP-9 at 6 hours increased with increasing severity of crush and was inversely related to tibialis anterior muscle force recovery. The ratio of MMP-9:MMP-2 expression correlated well with recovery of compound nerve action potential amplitude at 6 weeks. Conclusions: Resolution of nerve hyperemia may correlate with nerve recovery from trauma, but early measures of nerve blood flow after injury are not prognostic of recovery. Ratio of MMP-9:MMP-2 expression 6 hours after injury correlates with recovery of compound nerve action potential at 6 weeks, while MMP-9 expression alone predicts tibialis anterior recovery. These findings together suggest that increased MMP-9 expression is a potentially useful marker of more severe nerve injury

A numerical study of the bearing capacity factor Nγ

Values of the bearing capacity factor Nγ are numerically computed using the method of triangular slices. Three assumptions of the value of ψ, the base angle of the active wedge, are analyzed, corresponding to the following three cases: (1) ψ = φ, the internal friction angle; (2) ψ = 45° + φ/2; and (3) ψ has a value such that Nγ is a minimum. The location of the critical failure surface is presented and the numerical solutions to Nγ for the three cases are approximated by simple equations. The influence of the base angle on the value of Nγ is investigated. Comparisons of the present solutions are made with those commonly used in foundation engineering practice.published_or_final_versio

Determination of bearing capacity of shallow foundations without using superposition approximation

The Terzaghi superposition assumption has been widely used to determine the bearing capacity of shallow footings. Although this assumption always errs on the safe side, a rigorous procedure to calculate the bearing capacity is still of engineering value. This paper presents such a procedure that is free from errors as a result of the superposition assumption. It demonstrates that the ultimate bearing capacity can be precisely expressed by the Terzaghi equation, except that the bearing capacity factor N y is dependent upon the surcharge ratio. A recently developed numerical method, i.e., the critical slip field method, is used to calculate the modification coefficient for modifying N y It is found that this modification coefficient increases with the surcharge ratio at small values of surcharge ratio and then remains constant for large values of surcharge ratio. However, the errors invoked by the superposition assumption do not exceed 10%. On the basis of numerical calculations, a simple closed-form expression of the modification coefficient is proposed that yields the theoretically rigorous ultimate bearing capacity. In the later part of the paper, errors in bearing capacity calculations owing to the use of conventional procedures are analyzed. It is concluded that the continued use of conventional procedures is justified, but the inherent errors should not be neglected in assessing the performance of shallow foundations.published_or_final_versio