Three dimensional lower bound solutions for the stability of plate anchors in sand

Soil anchors are commonly used as foundation systems for structures that require uplift or lateral resistance. These types of structures include transmission towers, sheet pile walls and buried pipelines. Although anchors are typically complex in shape (e.g. drag or helical anchors), many previous analyses idealise the anchor as a continuous strip under plane strain conditions. This assumption provides numerical advantages and the problem can solved in two dimensions. In contrast to recent numerical studies, this paper applies three dimensional numerical limit analysis and axi-symetrical displacement finite element analysis to evaluate the effect of anchor shape on the pullout capacity of horizontal anchors in sand. The anchor is idealised as either square or circular in shape. Results are presented in the familiar form of breakout factors based on various anchor shapes and embedment depths, and are also compared with existing numerical and empirical solutions

The stability of inclined plate anchors in purely cohesive soil

Soil anchors are commonly used as foundation systems for structures requiring uplift resistance such as transmission towers, or for structures requiring lateral resistance, such as sheet pile walls. To date the design of these anchors has been largely based on empiricism. This paper applies numerical limit analysis and displacement finite element analysis to evaluate the stability of inclined strip anchors in undrained clay. Results are presented in the familiar form of break-out factors based on various anchor geometries. By obtaining both upper and lower bound limit analysis estimates of the pullout capacity, the true pullout resistance can be bracketed from above and below. In addition, the displacement finite element solutions provide an opportunity to validate these findings thus providing a rigorous evaluation of anchor capacity

Uplift capacity of inclined plate ground anchors in soil

The design of many engineering structures requires foundation systems to resist vertical uplift or horizontal pull-out forces. In such cases, an attractive and economic design solution may be achieved through the use of tension members. These members, which are referred to as soil anchors, are typically fixed to the structure and embedded in the ground to sufficient depth that they can resist pull-out forces with safety. Soil or 'ground' anchors are a lightweight foundation system designed and constructed specifically to resist any uplifting force or overturning moment placed on a structure

Three-dimensional stability charts for slopes based on limit analysis methods

This paper uses finite element upper and lower bound limit analysis to produce chart solutions for three-dimensional (3D) natural slopes for both short- and long-term stability. The presented chart solutions are convenient tools that can be used for preliminary design purposes. The rigorous limit analysis results in this paper were found to bracket the true factor of safety within ±10% or better, which can be used as a benchmark for the solutions from other methods. The depth of the slip surfaces is observed to be generally shallow for most analyzed cases, particularly for the long-term slope stability problem. In addition, it was found that using a two-dimensional (2D) analysis may lead to significant differences in estimating safety factors, which can differ by 2%–60% depending on the slope geometry and soil properties. Therefore, great care and judgement are required when applying 2D analyses to 3D slope problems

Effect of abutment angle on stress distribution under supercritical longwall panels

Efficient and effective ground control design in underground coal mines requires a sound understanding of the stress environment in the surrounding rock strata. This is particularly the case in multiple-seam mining where the stress environment is very different from that encountered when mining in strata that has not previously been mined. This is because previous mining activity causes a redistribution of the ground stresses, leading to the concentration of vertical load in chain pillars. The extra overburden load carried by the chain pillars in longwall mines is related to a quantity identified as the “abutment angle”. This study aims to present the effects of the abutment angle on the final in situ vertical stress in the rock strata underlying supercritical longwall panels. The magnitude and distribution of these vertical stresses provide valuable information when considering multiple seam mine layouts below existing longwall panels. Wilson’s equations have been used for the stress distribution induced in the pillars and longwall goaf, to estimate the stress changes in the strata beneath the mined panel using a plane strain elastic model. Finite element analysis was used to predict the final stress in the underlying strata. The results show that larger abutment angles generate larger stresses in the underlying stratum. For a given ratio of interburden to overburden there is a linear relationship between the abutment angle and the maximum normalised vertical stress

Efficient Syntheses of AZD4407 via Thioether Formation by Nucleophilic Attack of Organometallic Species on Sulphur

The development of two efficient strategies for the synthesis of AZD4407 is reported, both of which are considered suitable for large-scale manufacture. In the first approach, 3-bromothiophene is coupled with (2S)-2-methyltetrahydropyran-4- one using Grignard chemistry. Following hydroxyl protection and lithiation at thiophene C-2, reaction with a protected 5-mercapto-1-methyl 1,3-dihydro-indol-2-one derivative bearing a leaving group on sulphur provides AZD4407 after acid- catalysed deprotection and epimerisation. The second approach starts from 2,4-dibromothiophene, which undergoes a selective Grignard exchange reaction at C-2 followed by reaction with similar protected mercapto-oxindole derivatives. Reprotection of the oxindole ring, followed by a second Grignard exchange, and reaction with (2S)-2-methyltetrahydropyran-4-one provides AZD4407 after acid-catalysed deprotection and epimerisation