• Computers and Concrete
• /
• v.32 no.5
• /
• pp.465-474
• /
• 2023

The point load test (PLT) is a widely-used alternative method in the field to determine the uniaxial compressive strength due to its simple testing machine and procedure. The point load test index can estimate the uniaxial compressive strength through conversion factors based on the rock types. However, the mechanism correlating these two parameters and the influence of the mechanical properties on PLT results are still not well understood. This study proposed a theoretical model to understand the mechanism of PLT serving as an alternative to the UCS test based on laboratory observation and literature survey. This model found that the point load test is a self-confined compression test. There is a compressive ellipsoid near the loading axis, whose dilation forms a tensile ring that provides confinement on this ellipsoid. The peak load of a point load test is linearly positive correlated to the tensile strength and negatively correlated to the Poisson ratio. The model was then verified using numerical and experimental approaches. In numerical verification, the PLT discs were simulated using flat-joint BPM of PFC3D to model the force distribution, crack propagation and BPM properties' effect with calibrated micro-parameters from laboratory UCS test and point load test of Berea sandstones. It further verified the mechanism experimentally by conducting a uniaxial compressive test, Brazilian test, and point load test on four different rocks. The findings from this study can explain the mechanism and improve the understanding of point load in determining uniaxial compressive strength.

• Geomechanics and Engineering
• /
• v.13 no.6
• /
• pp.1045-1055
• /
• 2017

Tensile strength is considered key properties for characterizing rock material in engineering project. It is determined by direct and indirect methods. Point load test is a useful testing method to estimate the tensile strengths of rocks. In this paper, the effects of rock shape on the point load index of gypsum are investigated by PFC2D simulation. For PFC simulating, initially calibration of PFC was performed with respect to the Brazilian experimental data to ensure the conformity of the simulated numerical models response. In second step, nineteen models with different shape were prepared and tested under point load test. According to the obtained results, as the size of the models increases, the point load strength index increases. It is also found that the shape of particles has no major effect on its tensile strength. Our findings show that the dominant failure pattern for numerical models is breaking the model into two pieces. Also a criterion was rendered numerically for determination of tensile strength of gypsum. The proposed criteria were cross checked with the results of experimental point load test.

• Explosives and Blasting
• /
• v.22 no.2
• /
• pp.45-54
• /
• 2004

Samples examined in this study were acquired from Machun building stone, Dukwoo building stone in Kyungnam province The aim of this study is to examine physical features of Machun rock from specific gravity, porosity. absorption, point load test. triaxial compressive test, Brazilian test, petrology test, and chemical analysis test.

• Explosives and Blasting
• /
• v.22 no.1
• /
• pp.81-91
• /
• 2004

Samples examined in this paper were selected from Samwoo building stone, Sinra building stone, Gana building stone, and Chung gin building stone in Kyunggi province and Whakwang industry, Gomoch building stone, and Sejin building stone in Kyungbuk province. The point of this study is to examine the physical and mechanical features of Pochun rock, Munkyung rock and Ildong rock through specific gravity, porosity, absorption, point load test, triaxial compressive test Brazilian test, petrology test and chemical analysis test.

• Journal of Korean Society on Water Environment
• /
• v.20 no.4
• /
• pp.333-338
• /
• 2004

This study was carried out to investigate the generation and discharge characteristics of non-point pollutants from farmlands in Nak-dong river basin. Annual unit generation load of nitrogen and phosphorus by fertilization in the test paddy field was almost similar to those calculated by the fertilization standards of district agricultural technology center, but it was extremely higher in case of the test dry field. By comparing annual total generation load of nutrients from fertilization to the data of fertilizer marketing, the accurate forecasting of generation load of pollutants was achieved by marketing data. The annual total discharge ratio of nutrients through infiltration and overflow from the farmland of the test paddy field were 9.5% and 1.1%, respectively, and those in the test dry field were 22.0% and 0.1%, respectively. The monthly discharge load of nutrients were shown the highest proportioned to the discharge load from lands, but it showed higher in phosphorus, which was caused by the intermittent discharge of phosphorus accumulated in drainage.

• Journal of the Korean Society of Industry Convergence
• /
• v.5 no.3
• /
• pp.247-254
• /
• 2002

This study has researched the following conclusion to compare to the existing theory and to examine lateral earth pressure, which have measured to add incremental load on sandy soil, and were different in types of compaction by modeling earth pressure test. Lateral earth pressure by incremental load shows that it is increasing at depth forty four centimeters as 2/3H point for wall high, and under 2/3 H point the variation of earth pressure on incremental load is not conspicuous. Therefor, the more a position of surcharge load is close with fixed wall, the more a variation of lateral earth pressure marks considerably. According to relative compaction density of soil, lateral earth pressure turns up larger effective value for layer compaction test to a thickness of thirty three centimeters than layer compaction test to a thickness of twenty centimeters by the roller.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.228-233
• /
• 2004

A derailment coefficient of railway vehicle is as one of important element that estimate running safety. Derailment coefficient is ratio of lateral load/vertical load happens in contact point between wheel and rail. Lateral load increases, dangerous of derailment can rise. There are ground and vehicle to measurement method of these derailment coefficient. Method of ground is simple, but when vehicles passes data of a point, there is shortcoming that acquire locally. Curved surface style wheel shape that use so far among vehicle method in this research wishes to be not but describe about static load test of wheel-set for derailment coefficient measurement that have plane plate shape that manufacture separate way and correction result etc. to test.

• Journal of the Korean GEO-environmental Society
• /
• v.8 no.1
• /
• pp.21-26
• /
• 2007

The strength evaluation of rocks is a very important factor in designing and constructing tunnels or underground excavation. However, it takes a lot of time and endeavor to perform the unconfined compressive strength test for practice and a number of tests are limited. In order to make up for this method, the point load strength test is suggested. Generally, the strength of a rock differs depending on its type and region. However, as people unite the Point Load Strength Indexes of various regions and types to use in practice in many cases, they find difficulty in analogizing the exact strength. The purpose of this study is suggestion of the value in construction site by analizing the relation of both unconfined compressive and point load strength in the Gyeonggi gneiss complex.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.1
• /
• pp.189-197
• /
• 2011

In the field of structural test, it is a very important factor to apply with an appropriate test jig to enhance test accuracy and efficiency. Especially in the large scale structure test, proper test apparatus scheme will reduce overall cost and time of the test project. Actuators, oil jack and UTM is generally used to evaluate the flexural capacity of the test beam. But in the case of multiple loading point or asymmetric loading of large scale test specimen, existing test method such as UTM have a difficulty in giving an accurate load. In this study new test method which is composed of existing test apparatus will be developed to improve test accuracy and economic efficiency.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.6
• /
• pp.22-27
• /
• 1997

In general, the load which acts on the structure is almost independent of time in many locations. In this case. It is difficult to estimate the life with the service load history, because the structure is on the multi- axial and multi-point loading states. In this study, the service load of the excavator which is widely used in industry field was calculated using measured cylinder pressures and displacements. The fatigue life was estimated using the multi-axial and multi-point load counting method. Service load history of 4 pin joint which act independently each other is yielded by mult-axial and multi-point load counting method. The stress spectrum is yielded by superposition of the results of FEM stress analysis applied unit load. Palm- gren-Miner's cumulative Damage is 0.000804 for Von Mises equivalent stress sequence by one side fillet weld S-N curve. This result agress with Bench test results. As a result of this study, the fatigue life esti- mation using the multi-axial and multi-axial and multi-point load counting method is useful.