1,720,968 research outputs found
Investigation of New Energy Absorbing Mechanisms Used to Fix Rock Bolt Plates
Full text linkIn this study, different plate fixing designs were tested in order to improve rock bolting performances. Instead of commonly used steel nuts, different plate fixing designs were investigated by both laboratory and site studies. In addition, the usability of nuts and energy absorbers made of the polyamide type engineering polymer was investigated to assess whether they are advantageous for the aim of supplying high-energy absorbing features. In this experimental study, deformation-controlled load tests were carried out to evaluate the bearing and energy absorption capacities of totally eight different groups of specimens. According to the findings from this study, use of the polyamide material with steel nuts as an energy absorber material, rather than using instead of steel nuts supplies good results. As another outcome, it has been determined that use of proper washers between steel nuts and polyamide absorbers can significantly improve the energy absorption performances. It has been evaluated that the energy absorption capacity of the bolt plates can be economically increased up to 10 times by using suitable polyamide energy absorbers placed between the plate and steel nut parts. It was concluded that the polyamides can be used to remarkably improve the rock bolting performances especially in the rock masses where the high energy absorption capacity property is needed, like those with rock bursting, squeezing and swelling problems
An Investigation of Soil Void Ratio Effect on Liquid Limit Values Determined by Different Test Methods
Full text linkUse of Microgrid Fiber type new Additives to Improve Load Bearing and Energy Absorption Capacities of Shotcrete Mixes
Full text linkIn this study, different polypropylene type polymer fiber additives were comparatively examined carrying out a series of EFNARC plate (slab) loading test, which is a popular test for evaluation of the shotcrete liner performances. A new fiber type called microgrid fiber (MGF) was compared with the conventional polypropylene fiber (PPF) additives. Shotcrete mixes were tested to determine their load bearing, deformability and energy absorption capacity properties. Additionally, indirect (splitting) tensile strength (ITS) values of specimens were determined to compare influences of different fiber types. According to the slump test findings, the workability of the fresh mixes decreased with an increase in fiber content. It was determined that the workability properties of conventional PPF and MGF added specimens were similar. However, it was found that the MGF type additive reduced the fresh mix workability more than the PPF additive due to the increase in the fiber content. It was found that MGF additive was found to supply better improvements in ITS values, load bearing and energy absorption capacity properties of slabs in comparison with the conventional PPF additive. The new MGF type additive was assessed to be usable to effectively improve the shotcrete performances
Use of Microgrid Fiber type new Additives to Improve Load Bearing and Energy Absorption Capacities of Shotcrete Mixes
Full text linkIn this study, different polypropylene type polymer fiber additives were comparatively examined carrying out a series of EFNARC plate (slab) loading test, which is a popular test for evaluation of the shotcrete liner performances. A new fiber type called microgrid fiber (MGF) was compared with the conventional polypropylene fiber (PPF) additives. Shotcrete mixes were tested to determine their load bearing, deformability and energy absorption capacity properties. Additionally, indirect (splitting) tensile strength (ITS) values of specimens were determined to compare influences of different fiber types. According to the slump test findings, the workability of the fresh mixes decreased with an increase in fiber content. It was determined that the workability properties of conventional PPF and MGF added specimens were similar. However, it was found that the MGF type additive reduced the fresh mix workability more than the PPF additive due to the increase in the fiber content. It was found that MGF additive was found to supply better improvements in ITS values, load bearing and energy absorption capacity properties of slabs in comparison with the conventional PPF additive. The new MGF type additive was assessed to be usable to effectively improve the shotcrete performances
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Use of Rock Mass Rating (RMR) values for support designs of tunnels excavated in soft rocks without squeezing problem
Full text linkLength Effect on Load Bearing Capacities of Friction Rock Bolts
Full text linkWOS: 000487826900004Change in the load bearing capacity of the split set type friction rock bolts with variations of bolt lengths was investigated within this study. To determine a relation between the load bearing capacity and bolt length parameters, different friction bolt models with various lengths were analyzed with a numerical modelling study. In addition, a series of pull-out tests was carried out to evaluate the load bearing capacities of the split set type friction rock bolts with different lengths. The load bearing capacity of the bolts was found to decreasingly increase with the increase in the bolt length. As an outcome of this study, a relation between the load bearing capacity and rock bolt length parameters is suggested in accordance with the results obtained from both numerical and experimental studies
Determination of Direct Tensile Strength Values of Rock Materials by a New Test Method of Drilled Disc Tension
Full text linkWOS: 000514834600004Use of drilled disc specimens was investigated with both numerical and experimental studies to determine direct tensile strengths of rock materials. A new loading apparatus with rods to insert into the drill holes of discs has been designed and manufactured to supply tension by using the compression test presses. In addition to the use of popular compressive presses for direct tension, elimination of the gluing in the standard direct tensile strength test method is a significant advantage to make possible both hard and soft rocks to be tested. The Brazilian test discs with the diameter of NX size and length to diameter ratio of 0.5 were used in tests. Different loading apparatus designs were analyzed and ideal angle of contact between rock and the loading rods was assessed to be 50 degrees within various choices investigated in this study. The drilled discs were determined to fail due to the crack initiation under the condition of uniaxial tensile stress distribution at sidewalls of the hole. In addition to the drilled disc tension test, standard direct tensile strength tests were also carried out to take as reference and compare the results obtained from different methods. According to the results of both numerical and experimental studies, an equation was suggested to determine uniaxial tensile strengths of drilled disc specimens with 20 mm hole diameter and the contact angle of 50 degrees
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