A simplified approach to directly consider intact rock anisotropy in Hoek–Brown failure criterion

Many rock types have naturally occurring inherent anisotropic planes, such as bedding planes, foliation, or flow structures. Such characteristic induces directional features and anisotropy in rocks' strength and deformational properties. The Hoek–Brown (H–B) failure criterion is an empirical strength criterion widely applied to rock mechanics and engineering. A direct modification to H–B failure criterion to account for rock anisotropy is considered as the base of the research. Such modification introduced a new definition of the anisotropy as direct parameter named the anisotropic parameter (Kβ). However, the computation of this parameter takes much experimental work and cannot be calculated in a simple way. The aim of this paper is to study the trend of the relation between the degree of anisotropy (Rc) and the minimum value of anisotropic parameter (Kmin), and to predict the Kmin directly from the uniaxial compression tests instead of triaxial tests, and also to decrease the amount of experimental work

Magnetization of three Nubia Sandstone formations from Central Western Desert of Egypt

A total of 198 oriented cores (from 16 sites) have been sampled from three Cretaceous Nubia sandstone formations distributed around the Kharga–Dakhla and Dakhla–Uwainat roads in the Western Desert for paleomagnetic studies. Two of these formations are of the Early Cretaceous (the Six Hills, Abu Ballas formations) and the third one is of the Late Cretaceous (Maghrabi formation). The studied rocks are subjected to rock magnetic measurements as well as demagnetization treatment. Rock magnetic experiments reveal that the presence of hematite is the main magnetic mineral in the three formations. Therefore, present study relies mostly on thermal demagnetization. Two magnetic components have been isolated from the studied rocks. The first component has been isolated from the Six Hills and Abu Ballas formations and is carried by hematite with D = 347.1°, I = 41.6° with α95 = 7.8° and the corresponding pole lies at lat. = 78.2° N and long. = 294.1° E. The second component has been isolated from the Maghrabi formation and is carried also by hematite with D = 22.7°, I = 28.4° with α95 = 9.9° and pole position lies at lat. = 66.3° N and long. = 140.6° E. The first magnetic component obtained from the two older formations is considered primary, as the corresponding pole reflects the age when compared with the previously obtained Cretaceous poles for North Africa. On other hand, the second pole obtained from the Maghrabi formation (the younger) is inconsistent with the Cretaceous pole positions for North Africa, but falls closer to the Eocene pole indicating that the rocks of this formation could have suffered remagnetization during the late Eocene time

A model for evaluating the fire resistance of contour- protected steel columns

A numerical model, in the form of a computer program, for evaluating the fire resistance of insulated wide-flange steel columns is presented. The three stages associated with the thermal and structural analysis in the calculation of fire resistance of columns is explained. The use of the computer program for tracing the response of an insulated steel column from the initial pre-loading stage to collapse, due to fire, is demonstrated. The validity of the numerical model used in the program is established by comparing the predictions from the computer program with results from full-scale fire tests. Details of fire tests carried out on wide-flange steel columns protected with ceramic fibre insulation, together with results, are presented. The computer program can be used to evaluate the fire resistance of protected wide-flange steel columns for any value of the significant parameters, such as load, section dimensions, column length, type of insulation, and thickness of insulation without the necessity of testing.Nous pr\ue9sentons ici un mod\ue8le num\ue9rique sous la forme d?un programme servant \ue0 \ue9valuer la tenue au feu des poutres d?acier \ue0 ailes larges isol\ue9es. Les trois (3) stades qui sont associ\ue9s \ue0 l?analyse thermique et \ue0 l?analyse structurale dans le calcul de la tenue au feu des poutres sont expliqu\ue9s. On d\ue9montre l?utilisation du programme aux fins du tra\ue7age de la courbe de r\ue9ponse de la poutre d?acier isol\ue9e, \ue0 partir du stade pr\ue9alable \ue0 la charge jusqu?\ue0 l?effondrement caus\ue9 par le feu. La validit\ue9 du mod\ue8le num\ue9rique employ\ue9 dans le programme est \ue9tablie par comparaison des pr\ue9dictions du programme avec les r\ue9sultats provenant des essais de r\ue9action au feu en vraie grandeur. Sont expos\ue9s les d\ue9tails des essais de r\ue9action au feu men\ue9s sur les poutres d?acier \ue0 ailes larges prot\ue9g\ue9es par un isolant en fibre de c\ue9ramique, ainsi que les r\ue9sultats de ces essais. On peut employer ce programme pour \ue9valuer la tenue de poutres d?acier \ue0 ailes larges prot\ue9g\ue9es relativement \ue0 toute valeur des param\ue8tres significatifs, tels que la charge, les dimensions de la section, la longueur des poutre, le type et l?\ue9paisseur de l?isolant, sans n\ue9cessiter de mise \ue0 l?essai.Also to be published in Sixth IAFSS Symposium in France.Peer reviewed: YesNRC publication: Ye