Analysis of The Rock Fracture on Uniaxial Compressive Strength Test

The compressive strength test is one of the technical properties or compressive strength tests that are commonly used in rock mechanics to determine the collapse point or the elasticity of rock against maximum pressure. The rock collapse point is a measure of the strength of the rock itself when the rock is no longer able to maintain its elastic properties. The purpose of this test is to find out how long the rock maintains its strength or elasticity properties when pressure is applied, and to find out the difference between the strength of compact rock and rock that has fractures when pressure is applied. Rocks that have fractures will break more easily or quickly when pressure is applied compared to compact rocks. This analysis is carried out by comparing the rock strength of each sample, both those that have fractures and compact rocks. To find out these differences, laboratory testing was carried out. The test results show the value (compressive strength test 57.76 MPa), (elastic modulus 5250.000MPa), (Poisson ratio 0.05) and the average value of rock mechanical properties test (axial 0.91), (lateral-0.279), and (volumetric 0.252) . Based on the test results above, it shows that rocks that have fractures will break more easily when pressure is applied, compared to compact rocks that have a long time in the uniaxial compressive strength test.

Prediction of Uniaxial Compressive Strength of Granite Rock Samples of Lugoba Quarry Using Rebound Hammer Test

Rebound hammer test is widely used as an indirect measure of uniaxial compressive strength for engineering materials such as concrete, soil, and rock in both civil and mining engineering works. In quarries, uniaxial compressive strength is a crucial parameter in the analysis of geotechnical problems involving rock stability and rock blasting design. This study aims at establishing the empirical models of uniaxial compressive strength fits on rebound hammer number that can be used to predict uniaxial compressive strength of granitic rock at Lugoba Quarry. Data for direct uniaxial compressive strength were obtained from uniaxial compressive strength test carried out on 20 core samples at the Dar es Salaam Institute of Technology Geotechnical Laboratory using ISMR Standard Procedures. The rebound hammer test was carried out using testing hammer type N. The tests were done horizontally on two scanline's geotechnical domains of the rock mass on the footwall side of the quarry. The obtained results of UCS ranging from 105 to 132.5 MPa and RHN from 44.90 to 49.5 were found to be comparable with values of other granitic rocks in other parts of the world. Regression Analysis using SPSS software was carried out to develop 5 regression models of UCS vs.RHN. The values of obtained in this study were found to be between 0.93 and 0.95, which are comparable with other studies. This implies that RHN accounted between 93 and 95% of the total variation of the UCS and the relationships were very strong. Two models; Logarithmic and exponential were found to be appropriate and recommended for application at Lugoba Quarry.

Effects of Temperature and Chemical Admixtures on the Properties of Rock-Based Geopolymers Designed for Zonal Isolation and Well Abandonment

In this paper, the impact of temperature and admixture-based salts on the mechanical and rheological properties, and composition of geopolymers was studied. Neat geopolymer and Class-G cement, manufactured by Dyckerhoff, were used as reference samples at elevated temperatures. To enhance the additive properties of the geopolymer slurry, a combination of K and Zn was examined with a variety of K:Zn ratio ranging from ∼0.15 to ∼0.25. The workability of samples was tested by using an atmospheric consistometer, while other rheological properties were examined by running fluid loss test, and rotational viscometer test. The sample with the best workability was cured for 1, 3, and 7 days at bottomhole static temperatures of 70 and 80°C and pressure of 140 MPa where the mechanical properties were examined by ultrasonic cement analyzer and uniaxial compressive strength test. X-ray diffraction was used to analyze the composition of samples at different curing times and temperatures. The obtained results showed that the salt derivative admixtures have a significant impact on the oligomerization and polycondensation phases, where it distinctively elongated the setting time, enhanced strength, and strength development. On the other hand, the temperature effect was clearly observed by reducing rheological properties, while maintaining similar mechanical properties.

Effect of Porosity on Uniaxial Compressive Strength in Sedimentary Rocks

The rock strength parameter is an important factor used in determining the geotechnical design in determining the stability of the underground slope or mine. One of the rock strength tests in the laboratory (intact rock) is the uniaxial compressive strength test. One of the factors that influence rock strength is the porosity of the rock itself, especially in sedimentary rocks. The rock porosity test is carried out by testing the physical properties of the rock, then a regression analysis is carried out to obtain the correlation of the effect of porosity on rock strength and the correlation between porosity and absorption considered in the analysis. The linear regression results obtained between porosity and saturated water content of rocks showed a positive correlation where the increase in porosity, the saturated water content also increased. The correlation between porosity and uniaxial compressive strength obtained a strong correlation with the power regression model as the best model compared to other regression models because it has the lowest error based on the Root Mean Square Error (RMSE). The final result is obtained by comparing the effect of porosity on rock strength, that is the higher the porosity value have the smaller porosity, so that an increase in rock porosity will reduce the strength of the rock.

Selected physical and mechanical properties of hemp seeds

The basic physical properties of hemp seeds were measured to determine the correlations between these properties to facilitate the planning of seed sorting operations. The basic dimensions (length, width, and thickness), terminal velocity, angle of external friction, and mass were determined in the selected seeds. The seeds were subjected to a uniaxial compressive strength test to determine the force required to damage a seed, the corresponding displacement, and the energy consumed during the trial. The seed sorting was based on the basic dimensions of the seeds in order to divide the seeds into groups with similar average mass. The hemp seeds were most effectively sorted with the use of a screen with slotted apertures. The optimal set of screens should separate approximately 11% to 24% of the seeds into a fraction with the lowest seed thickness, and approximately 16% to 21% of the seeds into a fraction with the highest seed thickness. The basic seed dimensions significantly influenced the specific mass of the individual hemp seeds, and the corresponding correlations are most effectively described by power functions.

Anisotropy of reinforced concrete from geophysical methods

Anisotropy is expressed as the direction-dependent change of material properties and it is a very important parameter to the correct determination of the concrete quality. For the aim of determining the concrete anisotropy, geophysical measurements in the study were carried out on the reinforced concrete samples with different strengths, before concrete strengths were determined from Uniaxial Compressive Strength test. Since the propagation direction of concrete pores and saturation type of it is important parameters in affecting the concrete anisotropy, prepared samples were cured as oven-dried, water-saturated, and dried in outside. Thus, the effects of curing conditions on the anisotropy of reinforced concrete were investigated by geophysical measurements. For this purpose, ultrasonic P and S wave measurements were made on two opposite surfaces of cubic samples with different reinforcement diameters. In addition, a total of 8 resistivity measurements were performed by taking two diagonal measurements on each surface in except of reinforced surfaces of the sample. The velocity and resistivity anisotropies of samples were determined by using the anisotropy relations given in the literature. As a result, it is determined that while reinforcement diameter has no distinctive effect on anisotropy, curing conditions are especially very effective on resistivity anisotropy.

Nonlinear Stress-Strain Model for Confined Well Cement

The cement sheath is the key for providing the zonal isolation and integrity of the wellbore. Oil well cement works under confining pressure, so it exhibits strong nonlinear and ductile behavior which is very different from that without confining pressure. Therefore, for the accuracy of the simulation and the reliability of well construction design, a reliable compression stress–strain model is essential for confined well cement. In this paper, a new axial stress–strain model for confined well cement is developed based on uniaxial and triaxial test data, examinations of failure mechanisms, and the results of numerical analysis. A parametric study was conducted to evaluate and calibrate the model. The model is simple and suitable for direct use in simulation studies and well design. Results from this study show the nonlinear compressive behavior of confined well cement can be predicted using the traditional uniaxial compressive strength test measurements.

PENGARUH PENAMBAHAN SEKAM PADI DAN POLIMER EMULSI POLY VINYL ACECATE CO ACRYLIC PADA TANAH LEMPUNG DENGAN OBJEK PENGUJIAN KEKUATAN BATU BATA MENGGUNAKAN METODE UNIAXIAL

Research on the effect of the addition of rice husk and poly vinyl acetate emulsion polymer co acrylic (PVA) on clay have been conducted to see the strength of brick. Calculation of strength compared to brick by rice husks and polymer emulsion and given rice husk without any emulsion polymer. Provision of rice husk to batter was fixed at 9:1, while the provision of PVA polymer mixture for each batter with varying percentage are 1%-7%. Based on the results of the research, showed that: uniaxial compressive strength test resultsbricks to mix rice husk without PVA emulsion polymer was 28,7kg/cm2(L0), compressive strength test results bricks to mix rice husk with PVA emulsion polymer to a mixture of 1%-7%, respectively: (PVA 1% of 28,7 kg/cm2 (L1);(PVA 2% of 28,7 kg/cm2 (L2); (PVA 3% of 28,7 kg/cm2 (L3); (PVA 4% of 28,7 kg/cm2 (L4); (PVA 5% of 28,7 kg/cm2 (L5); (PVA 6% of 28,7 kg/cm2 (L6); and (PVA 7% of 28,7 kg/cm2 (L7). From the above results show that the compressive strength test results bricks to mix rice husk with PVA emulsion polymer mix increased from 1% to 3% mix, while starting from a mixture of 4% to 7% of the compressive strength of bricks dropped dramatically. The addition of PVA 3% of additions that the most effective way to improve the compressive strength of the bricks with compressive strength reached 53,5 kg/cm2, or increase of 46,4% from a brick with a mixture ofrice husk.

Degradation Phenomenon of Basic Mechanical Properties of Plain Reactive Powder Concrete with Time

The same batch reactive powder concrete specimens were obtained with same raw materials and curing process, uniaxial compressive strength test had been done on the specimens after hot water curing placed in laboratory for seven days , three months and three years. The test results showed that seven-day strength and three-month strength of plain reactive powder concrete after hot water curing are almost equal. Strength of plain reactive powder concrete has not degradation within three months after hot water curing. While strength of plain reactive powder appears serious degradation phenomenon after placed in Laboratory for three years. Comparing uniaxial compressive strength test results of plain reactive powder concrete at three-month with three-year after hot water curing ,we find that strength of plain reactive concrete at three-year decrease about 27 percent than the strength of plain reactive powder concrete placed at laboratory for three months, and elasticity modulus increases about 71 percent, axial peak strain decrease about 62 percent respectively .With the passage of time, plain reactive powder concrete appears more Brittle Features and less toughness.

Petrographic study and its implication to the uniaxial strength of weathered volcanic rocks from tawau, sabah

This paper discussed the petrographic study and its effect to the uniaxial strength of weathered volcanic rocks from Tawau, Sabah, Malaysia. The volcanic rock consists of associated dacite, andesite and basalt rocks with the age of Pliocene to Quaternary. In this study the Murphy (1985) classification were used determine the weathering grade of volcanic rocks. The uniaxial strength value were used the Point Load Test and Uniaxial Compressive Strength test. The microstructures and identification of altered minerals were analysed using scanning electron microscope (SEM) and polarized microscope, respectively. The result of analysis indicated that the uniaxial strength of volcanic rocks decreased with the degree of weathering grades where the uniaxial strength decreased from 122.2 to 15.8 MPa for dacite, 143.4 to 10.1 MPa for basalt and 181.2 to 26.8 MPa for andesite. This result is due to the different percentages of quartz and feldspar minerals in the rock samples as well as formation of secondary minerals in weathered rocks. Microstructures study showed the appearance of micro fractures with narrow apertures in the minerals also influenced the uniaxial strength of the rocks.________________________________________GRAPHICAL ABSTRACT