Support Pillars Research Articles

Coach design for the Helsinki underground

After more than 20 years of planning, an underground system will be opened in Helsinki in 1978. In 1972, a short line was constructed, with six coaches for experiments. This article describes an analysis of these coaches from the point of view of ergonomics. A travelling experiment was organised, designed to simulate the final travelling situation. After the experiment the subjects filled out a questionnaire. During the trip the behaviour of the subjects and their moving in and out was observed by two TV recorders and two film cameras. The passengers evaluated the fitness of the train in the following order of importance: 1. speed 2. cost 3. comfort. The results showed that the demands placed on the lay-out of the trains were not fulfilled in regard to speed. Although the general impression was positive, the number of handles and support pillars, too narrow passages and a lack of space for goods were features most often criticised. On the basis of these results, several alternative lay-outs have been developed, also proposals concerning dimensions of the doors, design and location of the handles, design of the seats, etc.

Pabellón de exposiciones Thyssen de Hannover - Alemania Federal

This pavilion substitutes a former one for a similar use, which was destroyed by fire. It has been erected on a lot situated between pavilions 17 and 18, in front of the information pavilion of the Fair. It consists of two fundamental floors; and the four metallic support pillars, 1.80 m in diameter and 15 mm thick, stand out as its characteristic note; inside these pillars different ducts are housed, including the heating duct and the dum-waiter. The two longitudinal Vierendel girders are also structurally interesting and support the trusses. The exterior is done in metal and glass. The pavilion is divided into vestibules, cafeteria, colloquium rooms, conference rooms, various services, offices, etc.; all of these have been provided with the latest thermal advances insofar as climatizing and comfort.

Quantitative characteristics of the dust dynamics of a stream flowing around support pillars

Quantitative characteristics of the dust dynamics of a stream flowing around support pillars

Aerodynamic characteristics of currents in a high mining-out area confined by support pillars

1. The currents in a confined space containing support pillars display changes in static pressure both along and across the streams, which explains the unusual geometric parameters of the currents. 2. The turbulence intensities of the current vary with the height; the curve plotting this change is virtually a parabola, with a minimum in the height range 0.32–0.40 m, and therefore differs essentially from the curve for a confined space without obstacles. 3. The elucidation of the very complex laws governing the kinematic parameters of the currents is greatly helped if we employ an essentially new procedure: calculations allowing for the total momentum and local pressure losses. 4. Air mobility in the waste is fairly high. Interest attaches to the relation between the turbulence levels of the main and inducing currents.

Experimental investigation of air flow past support pillars in a bounded space

1. The geometric parameters for confined flows do not undergo substantial changes in relation to the height of the stope. 2. The normal distribution law characterizing the velocity profiles in subsurface flows and the Bessel function which is valid for flows propagating in restricted spaces which are not confined by support pillars are not applicable in the investigated conditions. The velocity distribution in the jets is characterized by several exponents: cubic close to the axis and firstpower at the boundaries. In the near-wall boundary layer the velocity profile is not governed by the “1/7 law” but is represented by a parabola with a high exponent. 3. The intensity of turbulent mixing is not constant but changes in a definite manner with a change in the degree of heightwise restriction of the flow. 4. The kinematic parameters of the flows are distinguished by a complex character owing to the effect of flow past support pillars on the structure of the ventilation currents.

Acidizing with Swellable Polymers

Abstract The benefits derived from an acidizing treatment are a function of the penetration achieved by the acid before complete spending. Additional penetration may be achieved bycontrolling acid leak-oft into formation pores in the channel faces, andretarding the reaction rate of the acid. A recently developed chemical additive consists of a synthetic polymeric material which absorbs hydrochloric- acid solutions, when suspended therein, swelling up to 40 times its original volume. These swollen particles have the ability to de form and seal-off formation pores, providing fluid-loss control. In addition, they provide a diffusion barrier between the fracture face and the acid solution, prolonging the spending time of the acid. Field applications of this new technique have shown promising results. A method of conducting acid fluid-loss tests, using carbonate cores, is believed to provide fluid-loss data that are more representative of formation conditions than the conventional filter-paper determinations. Introduction The concept of oilwell acidizing has changed since its first commercial application, 30 years ago. Originally, it was visualized that the acid penetrated thousands of tiny pores and flow channels in the matrix rock, enlarging them by dissolving the carbonate walls. The resultant permeability increase was assumed to be the responsible factor in increasing production from the well. Recent laboratory studies, however, have shown that this does not provide the complete picture. Although this type of individual pore penetration by the acid does take place during acid "soaks", designed to overcome "skin effect" due to mud invasion in the immediate vicinity of the wellbore, many years of experience have shown that considerable pressure is required to attain any appreciable injection rate into the fine capillary pores of the rock. During most acidizing treatments, the bottom-hole pressure build-up due to the restriction of flow into the formation exceeds the "breakdown" pressure of the rock so that a fracture is induced. In most cases, such fractures open up along natural, incipient fissures and zones of weakness in the rock and, therefore, tend to follow the natural stress pattern of the rock-whether it be horizontal, vertical or inclined. Because of the comparatively greater permeability of the channel in relation to that of the matrix, the bulk of the acid volume is diverted into the newly opened fracture. Here it quickly penetrates the formation, opening and extending the fracture in much the same manner as a conventional fracturing fluid. Unlike the fracturing fluid, however, most acidizing solutions contain no propping agent; thus, the open fracture will again close when the injection pressure is relieved. Laboratory studies have shown that in many cases the etching of the fracture faces, resulting from the reaction between the acidizing solution and the carbonate rock, is nonuniform due to the heterogeneity of the rock structure. As a result, the two fracture faces no longer match when pressure is released, and support pillars and intermediate voids remain, forming a high-conductivity channel for well fluids. Unfortunately, this is not true over the entire area of the fracture, but only over that portion of the fracture where the rock has been partially dissolved by the acid. The acid solution spends as its travels away from the wellbore; once it has completely spent, even though it may provide additional mechanical fracture extension, no additional benefit due to etching of fracture faces can be expected. Studies of acid reaction rates under formation conditions, observing the effect of different variables upon spending time, have shown that the reaction was often so rapid that very little penetration of the formation occurred before the acid was spent. Study was undertaken to devise methods of increasing the penetration of the acid before spending, so as to provide greater benefit from the acidizing treatment by etching a greater portion of the fracture faces. Several techniques were devised to accomplish this purpose. First, chemical additives were developed which were designed to retard the reaction rate of the acid, causing it to penetrate a greater distance from the wellbore before finally becoming spent. Another method was to increase the injection rate of the acid. However, it was found that the resultant increased shear tended to accelerate the reaction rate of the acid, partially offsetting the benefits of the higher injection rate insofar as achieving increased penetration before spending was concerned. Another approach to the problem of achieving increased penetration was the development of fluid-loss additives for acid solutions, which would minimize the volume of acid lost into formation pores in the fracture faces and provide maximum fracture extension for the volume of acid injected during the treatment. The use of fluid-loss additives is now considered the most effective method of providing maximum fracturing-fluid efficiency. Unfortunately, this latter technique does not solve the problem of rapid reaction rate, with consequent limitation of the fracture area benefited by reaction with unspent acid. JPT P. 1041^