• Advances in materials Research
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• v.13 no.1
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• pp.19-35
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• 2024

Presented Article evaluates the effect of nanoclay on permeability, compressive strength, and plasticity behavior of fine-grained soil related to the Tabriz landfill site. In this regard, comprehensive experimental study was performed on taken soil samples (42 specimens) with aim of design high-performance liners for Tabriz landfill. The samples was mixed by 0% (control) 3%, 6% and 9% nanoclay and prepared in 1, 7, 14 and 28 days before testing stage. Index tests like particle-size, permeability, atterberg limits, and uniaxial compressive strength (UCS) was conducted on samples. The results show that studied soil is classified as CL in USCS classification and atterberg limits measured as LL is 37, PL is 20.67, and PI is 16.33 which increase into 75, 45, and 30. The assessment presented the LL was increased about 20.27% based on increasing in nanoclay from 0% to 9%. These variations for PL and PI were 21.77% and 18.37%, respectively. Also, the and soil's compressive strength is increase from 120 kPa to 188 kPa and permeability is estimated as 4.25×10^-6 m/s which reduced into the 6.34×10^-9 m/s with respect the naboclay content increases form 0% to 9%.

• Geomechanics and Engineering
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• v.37 no.2
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• pp.149-166
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• 2024

The acoustic emission (AE) technique is utilized to estimate the rock failure status in underground spaces. Understanding the AE characteristics under loading conditions is essential to ensure the reliability of AE monitoring. The AE characteristics depend on the material properties (p-wave velocity, density, UCS, and Young's modulus) and damage stages (stress ratio) of the target rock mass. In this study, two groups of granite specimens (based on the p-wave velocity regime) were prepared to explore the effect of material properties on AE characteristics. Uniaxial compressive loading tests with an AE measurement system were performed to investigate the effect of the rock properties using AE indices (count index, energy index, and amplitude index). The test results were analyzed according to three damage stages classified by the stress ratio of the specimens. Count index was determined to be the most suitable AE index for evaluating rock mass stability.

• Journal of the Korean Geotechnical Society
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• v.34 no.10
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• pp.5-16
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• 2018

The ever-increasing amount of waste vinyl is causing big environmental problems. In particular, those from farming industry are sometimes left on site or even illegally reclaimed due to the lack of environmental concerns and capacity for collection, which worsens the situation. It is, therefore, believed that the recycling of waste vinyl is the most ideal solution in the viewpoint of environmental preservation. In this context, the potential of vinyl strip as a ground reinforcing material is investigated to expand the application of waste vinyl recycling. In this study, a series of uniaxial compression tests and resonant column tests were performed for sand specimens reinforced with vinyl strips and cement to investigate their reinforcing effects on static and dynamic behaviors. The changes in the uniaxial compressive strength (UCS), the shear modulus and the damping ratio according to the mixing ratio of vinyl strips and cements were analysed for sand specimens, having 40% and 60% relative densities, under various mixing conditions. As a result, both the static and dynamic reinforcing effects of vinyl strip-cement mixture were confirmed and the optimum mixing ratio was proposed.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.771-784
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• 2007

This study shows the weathering characteristics of mica-schist affected by faulting and metamorphism through laboratory tests. Frozen-thaw test, which simulate the physical-chemical weathering processes in the laboratory, shows the important influence of foliation developed in mica-schist, resulting in $20{\sim}40%$ reduction of UCS according to weathering grade of rock. Slaking durability test was carried out for different weathering grade rock specimens and indicated that the specimens from fault area had a low durability index compared to other relatively fresh samples. XRD analysis allowed to estimate the dynamic evolution of mineral composition through wet-dry cycle in which the chlorite was the most important mineral leached out during slaking test. The creep test indicated that the main deformation produced along the foliation plane. The compacted clay minerals between discontinuity planes influence on the discontinuity shearing properties and result in a big difference between peak shear strength and residual strength. The results of laboratory tests on mica-schist show the possibility of a important deformation along the foliation plane or discontinuity.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.435-443
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• 2007

This study shows the prediction of the engineering properties of weathered zone bearing corestones through the engineering geological surveys and the scale model test in the laboratory. The window survey and the observation on the borehole core were peformed on three natural slopes in corestones area in order to analyse the distribution pattern and the geometrical properties of corestones. Natural corestones were crushed and abrased for the scale model test into less than 5 mm in maximum-2mm in average by the scale reduction ratio based on the size of natural corestones and the specimen size. Scale model tests were carried out on soil and plaster model specimens with different corestone content ratio - 0%, 10%, 20%. The direct shear test on soils shows that shear strength is increased by the increase of corestone content ratio. The increase of cohesion is, however, more important factor to the shear strength of soil for 20% corestone content ratio due to interlocking of crushed corestone particles. The plaster model test shows a tendance of increase of UCS and modulus of elasticity with increase of corestone content. The variation ratio of specimen property by change of corestone content ratio in plaster model test was applied to in situ properties in order to estimate the properties of weathered zone bearing corestones. So it could be predicted that the increase of corestone content to 10% and to 20% produce about 18% and 30% UCS's increase respectively.

• Tunnel and Underground Space
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• v.24 no.3
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• pp.224-233
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• 2014

It is well known that rock properties can be affected by loading in underground condition. In the case of flooded underground mine or tunnels, rock properties variation due to loading might be different from the loading in dry condition. In order to verify the influence of saturated loading condition on rock properties, various laboratory tests had been carried out. Loading on the rock specimen was controlled to be ranged in between 20 ~ 80% of UCS. By comparing the variation of thermal, mechanical, and physical properties of rock specimens under the same load in saturated and dry condition, it was possible to find that the rock properties can be more significantly disturbed in the saturated loading condition than in dry loading condition.

• Tunnel and Underground Space
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• v.22 no.4
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• pp.284-295
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• 2012

Abrasiveness of rock plays an important role on the wear of rock cutting tools. In this study, Cerchar abrasiveness tests were carried out to assess the abrasiveness of 19 different Korean rocks. Cerchar abrasiveness test is widely used to assess the abrasiveness of rock because of its simplicity and inexpensive cost. This study examines the relationship between Cerchar Abrasiveness Index (CAI) and mechanical properties (uniaxial compressive strength, Brazilian tensile strength, Young's modulus, Poisson's ratio, porosity, shore hardness of rock), and the effect of quartz content, equivalent quartz content, which was obtained from XRD analysis. As a result of test, CAI was more influenced by petrographical properties than by the bonding strength of the matrix material of rock. CAI prediction model which consisted of UCS and EQC was proposed. CAI decreased linearly with the hardness of the steel pin. Numerical analysis was performed using Autodyn-3D for simulating the Cerchar abrasiveness test. In the simulations, most of pin wear occurred during the initial scratching distance, and CAI increased with the increase of normal loading.

• Geomechanics and Engineering
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• v.25 no.1
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• pp.41-48
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• 2021

In cold regions, the integrity of the infrastructures built on weak soils can be extensively damaged by weathering actions due to the cyclic freezing and thawing. This damage can be mitigated by exploiting soil stabilization techniques. Generally, ordinary Portland cement (OPC) is the most commonly used binding material for investigating the chemo-hydromechanical behavior. However, due to the environmental issue of OPC producing a significant amount of carbon dioxide emission, calcium sulfoaluminate (CSA) cement can be used as one of the eco-sustainable alternatives. Although recently several studies have examined the strength development of CSA treated sand, no research has been concerned about CSA cement-stabilized sand affected by cyclic freeze and thaw. This study aims to conduct a comprehensive laboratory work to assess the effect of the cyclic freeze-thaw action on strength and durability of CSA cement-treated sand. For this purpose, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were performed on the stabilized soil specimens cured for 7 and 14 days which are subjected to 0, 1, 3, 5, and 7 freeze-thaw cycles. The test results show that the strength and durability index of the samples decrease with the increase of the freeze-thaw cycles. The loss of the strength and durability considerably decreases for all soil samples subjected to the freeze-thaw cycles. Overall, the use of CSA as a stabilizer for sandy soils would be an eco-friendly option to achieve sufficient strength and durability against the freeze-thaw action in cold regions.

• Computers and Concrete
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• v.29 no.1
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• pp.31-45
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• 2022

Experimental and numerical simulation were used to investigate the effects of angle and number of T shape non-persistent crack on the shear behaviour of crack's bridge area under uniaxial compressive test. concrete samples with dimension of 150 mm×150 mm×40 mm were prepared. Within the specimen, T shape non-persistent notches were provided. 16 different configuration systems were prepared for T shape non-persistent crack based on two and three cracks. In these configurations, the length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 30°, 60° and 90°. Similar to cracks configuration systems in the experimental tests, 28 models with different T shape non-persistent crack angle were prepared in numerical model. The length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 15°, 30°, 45°, 60°, 75° and 90°. Tensile strength of concrete was 1 MPa. The axial load was applied to the model. Displacement loading rate was controlled to 0.005 mm/s. Results indicated that the failure process was significantly controled by the T shape non-persistent crack angle and crack number. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the crack number and crack angle. The strength of samples decreased by increasing the crack number. In addition, the failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods (PFC2D).

• Smart Structures and Systems
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• v.30 no.1
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• pp.49-62
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• 2022

Experimental and discrete element methods were used to investigate the effects of triple joints lengths and triple joint angle on the failure behavior of rock mass under uniaxial compressive test. Concrete samples with dimension of 20 cm × 20 cm × 5 cm were prepared. Within the specimen, three imbedded joint were provided. The joint lengths were 2 cm, 4cm and 6 cm. In constant joint lengths, the angle between middle joint and other joints were 30°, 60°, 90°, 120° and 150°. Totally 15 different models were tested under compression test. The axial load rate on the model was 0.05 mm/min. Concurrent with experimental tests, the models containing triple joints, length and joint angle are similar to the experiments, were numerical by Particle flow code in two dimensions (PFC2D). Loading rate in numerical modelling was 0.05 mm/min. Tensile strength of material was 1 MPa. The results show that the failure behaviors of rock samples containing triple joints were governed by both of the angle and the length of the triple joints. The uniaxial compressive strengths (UCS) of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behavior of discontinuities is related to the number of the induced tensile cracks which are increased by decreasing the joint length. Along with the damage failure of the samples, the acoustic emission (AE) activities are excited. There were only a few AE hits in the initial stage of loading, then AE hits rapidly grow before the applied stress reached its peak. In addition, every stress drop was accompanied by a large number of AE hits. Finally, the failure pattern and failure strength are similar in both methods i.e., the experimental testing and the numerical simulation methods.