Point Load Strength Index Research Articles

Point Load Strength Index and Slake Durability Index of Marbles from the Kanti Highway, Central Nepal LesserHimalaya

Point Load Strength Index (PLSI) is determined to obtain the strength of the rock, while Slake Durability Index (SDI) offers quantitative data on the mechanical behavior of rocks exposed to cyclic wetting and drying. This study aims to find out such index properties of marbles from the Markhu Formation of Central Nepal, Lesser Himalaya. The study of the strength and durability of marbles is crucial to classifying strength and identifying resistance to weathering, deterioration patterns, and rock quality. Fresh rock samples were collected from 20 different locations within the Markhu Formation, exposed across the Kanti Highway. The SDI and PLSI tests were carried out. The study reveals that the PLSI ranges from 2.54 to 9.08 MPa, and the test samples belong to strong to very strong rock categories according to the calculated value of UCS, indicating that the marbles from the Markhu Formation are of good quality and are strong enough to withstand the load, contributing to rock mass quality. The marbles have extremely high second cycle SDI (Id2) of 98.92% to 99.50%, and therefore, a high resistance to the wetting and drying cycle, showing slow slaking behavior. Between the second and the fifth cycle, SDI (Id5) was deduced by about 1%. It implies that the marbles are highly resistant to weathering and erosion. Marble shows two kinds of disintegration after the second cycle and deteriorates under three types of patterns under five cycles.

Estimation of Uniaxial Compressive Strengths of Cappadocia Pyroclastic Rocks after Freeze–Thaw Cycles Using Point Load Strength Index

Estimation of Uniaxial Compressive Strengths of Cappadocia Pyroclastic Rocks after Freeze–Thaw Cycles Using Point Load Strength Index

Evaluation of Ni-Cu Ore from Zapolyarnoe Based on Mineralogical and Physical Properties before and after Comminution

For the effective comminution and subsequent enrichment of mineral ores, comprehensive knowledge of their mineralogical and physical properties is required. Using an integrated methodology, this study evaluated samples of polymetallic Ni-Cu ore from Zapolyarnoe, Russia. Several analytical techniques were utilised, including optical microscopy, microindentation with Vickers geometry, the Point Load Test, and Mineral Liberation Analysis (MLA). The purpose of this study was to determine mineral associations, physical features, and enrichment during jaw crusher comminution. The acquired properties included the Point Load Strength Index, Vickers Hardness Number, and fracture toughness. The MLA method characterised seven fractions in terms of particle size distribution, degree of liberation, association, and modal mineralogy. Magnetite, pyrrhotite, pentlandite, and chalcopyrite were calculated in terms of wt% and their textural features. The enrichment of each ore phase in fractions with particle sizes smaller than 400 µm was determined. The influence of this enrichment was discovered to be correlated with various textural and structural parameters, such as intergrowth, grain size, and crack morphologies after indentations. In addition, the chromium content of magnetite contributed to an increase in the fracture toughness values. Despite the complexities involved, even limited samples of materials provide valuable insights into processing behaviour, emphasising the importance of considering mineralogical parameters in comminution studies.

Effect of rock properties on wear and cutting performance of multi blade circular saw with iron based multi-layer diamond segments

This study is an attempt for comprehensive, combining experimental data with advanced analytical techniques and machine learning for a thorough understanding of the factors influencing the wear and cutting performance of multi-blade diamond disc cutters on granite blocks. A series of sawing experiments were performed to evaluate the wear and cutting performance of multi blade diamond disc cutters with varying diameters in the processing of large-sized granite blocks. The multi-layer diamond segments comprising the Iron (Fe) based metal matrix were brazed on the sawing blades. The segment’s wear was studied through micrographs and data obtained from the Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDS). Granite rock samples of nine varieties were tested in the laboratory to determine the quantitative rock parameters. The contribution of individual rock parameters and their combined effects on wear and cutting performance of multi blade saw were correlated using statistical machine learning methods. Moreover, predictive models were developed to estimate the wear and cutting rate based on the most significant rock properties. The point load strength index, uniaxial compressive strength, and deformability, Cerchar abrasivity index, and Cerchar hardness index were found to be the significant variables affecting the sawing performance.

Reliability assessment of carbon fiber mortar: Combined pulse velocity, point load, and compressive strength tests

Cement mortar is used as an adhesive and plaster for brick walls, drainage channels or irrigation with river stones or mountain stones, and in the manufacturing of short revetments. The performance of cement mortar requires continuous improvement by construction materials researchers, scientists, and building contractors. Recently, carbon fiber sheet has gained popularity for use in retrofitting and improvement to the performance of building elements. This study aims to recycle small sheets of unused carbon fiber by cutting them into short carbon fiber (SCF) with a uniform length of 12 mm, which is used as an internal reinforcement in the cement mortar. All plain and fibrous mortar were prepared with a 50 mm cube mold. In addition, tests were conducted to provide reliable data regarding the application of recycled carbon fiber sheets as discrete fiber reinforcement in the improvement of cement mortar; these include ultrasonic pulse velocity (UPV), compressive strength, and point load strength index (PLSI) (known for performance rock testing in geotechnical and geological environments) tests. The test results for UPV, PLSI, and compressive strength showed that the addition of carbon fiber improves the performance of the mortar when compared to plain mortar. Furthermore, two simplified relationships are made: the first correlation was for PLSI with compressive strength, and the second correlation was for UPV with compressive strength. Finally, these correlations were compared with those of experimental tests obtained from published literature, thus demonstrating the correctness of the PLSI, compressive strength, and UPV values obtained in this study.

Overview of the Empirical Relations between Different Aggregate Degradation Values and Rock Strength Parameters

The aggregates are essential materials in civil engineering, they are used for railway and road constructions, for hydraulic engineering but they are also the base material of concrete. The crushed stones are exposed to several effects during their lifespan. Therefore, several tests were developed to evaluate their performance. One of the most important aspects is the resistance to degradation. However, degradation tests require special types of equipment and usually take longer than common strength tests which are more likely to be available for rock materials. Therefore, the empirical connections between strength and degradation values can be extremely useful in practice. The paper aimed to collect all available relationships and datasets from the literature that presents the relations between these different parameters – such as Aggregate Impact Value (AIV), Aggregate Crushing Value (ACV), Ten Percent Fines Value (TFV), Los Angeles Abrasion Value (LAAV), and micro-Deval Coefficient (MDE) – and rock strength parameters – such as Uniaxial Compressive Strength (UCS) and Point Load Strength Index (IS(50)) – and to provide the best-fit formula for different rock types. The paper also highlights the difficulties and limitations of the compared relationships.

Strength and durability status of the Fagfog Quarzite from the Lower Nawakot Group, central Nepal Lesser Himalaya

Railways have played vital role in the development of many countries worldwide. Government of Nepal has already planned to establish various national and international railway networks within the nation. A substantial quantity of durable rock ballasts is required for building a sustainable railway network. Quartzites from central Nepal Lesser Himalaya can be a promising source to fulfill this requirement. Therefore, the quartzites from the stratigraphic unit Fagfog Quartzites of the Lower Nawakot Group located in Dhading District along the Kalu Pandey Highway have been assessed to determine physical, strength and durability characteristics of the ballasts. All quartzite ballasts obtained from the bedrocks were of Precambrian, medium-grained, bladed to prolate shaped, white to brownish white, crushed quartzites. Dry density and water absorption were respectively 2336-2641 kg/m3 and 0-2.5%. The bulk density varies from 1204 and 1387 kg/m3. Point load strength index varies from 2.04 to 11.55 MPa (medium strong to extremely strong). Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) ranges from 14.85 to 22.77% and 15.51 to 22.17% respectively. Some 7% results of AIV and 20% of ACV results exceeded the established limiting value of 22%. The slake durability index (Id5) ranges from 95.19 and 99.11%, whereas Id2 ranged between 96.94 and 100%, which shows that 80% of the samples have very high slake durability whereas remaining 20% exhibit high slake durability. There was no significant change in slake durability index from the second to the fifth cycles. Los Angeles Abrasion Value (LAAV) varies from 12.07 to 31.34% and Sulphate Soundness Value (SSV) varies within a limited range of 0.20 and 4.59%. Conclusively, the comprehensive evaluation suggests that the quartzite ballast from the Fagfog Quartzite source display favourable qualities in terms of point load, crushing and impact strengths and durable against abrasion, slaking and frosting. Thus, the quartzites from Fagfog Quartzite hold significant potential as a suitable rock type for railway track ballasts.

Study on the mechanical properties of anisotropic red sandstone under point load strength test and uniaxial compression strength

The red sandstone of Xiaopu 3# branch Cave in the Yuxi section of the Central Yunnan Water Diversion Project was taken as the research object. The uniaxial compression strength and point load strength test are conducted from the perspectives of vertical and parallel stratifications, respectively, and then the anisotropy of red sandstone was analyzed in detail. The data obtained from the field and laboratory test was analyzed, and the conversion relationship between point load strength index and uniaxial compression strength is a power function under both parallel stratification and vertical stratification. The study results showed that: The mechanical properties of red sandstone have obvious anisotropy. The difference in its mechanical properties is particularly evident in UCS and point load tests and Is(50) and UCS under vertical stratification are significantly greater than Is(50) under parallel stratification. The point load strength correction index m of red sandstone is m = 0.4096 under parallel stratification, and m = 0.4408 under vertical stratification.

Railway ballast aggregate characterization through a new strength index: Preliminary suitability evaluation of an industrial by-product for a railway application

Ballast is a layer of the railway infrastructure that ensures the correct geometric position of track equipment, distributing vertical loads on the underlying layers. Ballast is composed by aggregate grains of adequate grading, containing a consistent number of voids and a medium–low fine content.The aggregates of ballast must be tested in the laboratory to ascertain the suitability for their use under construction or maintenance. In this work, the physical–mechanical characteristics of different types of aggregate (natural and “artificial”) were evaluated to verify their acceptability as ballast under the Italian specifications. All the aggregates came from Italian production plants. One “artificial” aggregate (steel slag) was used to assess if it can be used instead of the natural aggregate on a railway line in Italy. A mixture of natural and artificial aggregates was also tested for comparison purposes. An index from Point Load Test was also assessed to predict the main physical–mechanical characteristics provided by the laboratory tests.The artificial aggregate shows excellent physical–mechanical properties, compared to the natural one, indicating that the tested by-product can replace the natural aggregate. The mixture of natural and artificial aggregates can guarantee the preservation of natural resources and solve supply difficulties of by-products, maintaining very good physical–mechanical characteristics.In general, the Los Angeles index (both before and after the freeze-thawing cycles) shows a good correlation with the Point Load Strength Index for the tested ballast aggregates. Starting from this result, the Point Load Test could be used to characterize ballast aggregates. A statistical analysis was also performed on the other physical–mechanical parameters: a good correlation was found in some cases, indicating that the Point Load Strength Index can provide a first indication of the other physical–mechanical characteristics of ballast aggregates.

Evaluation of excavation method on point load strength of rocks with poor geological conditions in a deep metal mine

In the field of deep mining engineering, it poses a challenge to promptly determine the mechanical properties of rocks under poor geological conditions through in-situ tests. However, the indirect determination of uniaxial compressive strength (UCS) of rocks can be achieved through the point load strength index (PLSI) test on irregular samples. In the present study, laboratory uniaxial compressive and field PLSI tests were carried out on irregular ore and rock blocks extracted through mechanical mining methods from a stope at a lead–zinc mine in Yunnan Province, China, with a depth of approximately 1000 m. The effects of mechanical excavation and drilling-blasting methods on the PLSI of rocks and ores are compared. It is found that there are significant differences in the point load strength indexes obtained by different excavation methods, and the Is(50) obtained after the mechanical excavation method approximates the actual value of ore and surrounding rocks. Two correction methods were utilized to obtain the point load strength indexes Is(50)-1 and Is(50)-2 of irregular rock samples. The correlation factors (k) linking Is(50) to UCS and Brazilian splitting strength are derived based on testing results. The findings indicate that using the conversion factor (k) recommended by ISRM to predict the UCS of rocks may significantly underestimate the actual strength of rocks in intricate mining environments. This study can serve as a benchmark for analogous deep mining projects.

Machine learning models for predicting unconfined compressive strength: A case study for Precambrian basement complex rocks from Ado-Ekiti, Southwestern Nigeria

This study investigates the applicability of four distinct machine learning (ML) models – Random Forest (RF), Relevance Vector Machine (RVM), Support Vector Machine (SVM), and Artificial Neural Network (ANN) - for predicting the unconfined compressive strength (UCS) values of Precambrian basement rocks. The models employ input parameters such as rock aggregate index (Aggregate Crushing Value (ACV), Aggregate Impact Value (AIV), and Los Angeles Aggregate Value (LAAV)) and mechanical test index values (Schmidt Hammer Rebound Number (SHR) and Point Load Strength Index (IS(50)) for prediction purposes. Additionally, a multilinear regression (MLR) model was implemented to compare the predictive performance of the ML models against the traditional linear regression model. The developed models were validated using performance metrics such as Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and Adjusted R-Squared (Adj.R2). The Friedman statistical test was also employed to investigate the significance of the differences in the performance of the models. The results indicate that all the models performed well and showed better predictive performance compared to the MLR model during both the training and testing phases, except for the ANN model, which exhibited slightly poorer performance than the MLR model in the testing phase. However, the SVM model demonstrated the best predictive accuracy among all the models with MAE, RMSE, and Adj.R2 scores of 0.76 and 1.45; 1.16 and 1.8; 0.98 and 0.90, respectively, for the training and testing phases. The difference in the performance of the predictive models was statistically significant, as revealed by the Friedman statistical test. A feature importance analysis was conducted to verify the significance of each input parameter, revealing that all input features had a positive effect on the output of all the models. However, IS(50) had the most significant impact on the models.

Engineering Properties of Aggregates for Railway Ballast, Rapati Nadi, Central Nepal Sub-Himalaya

Nepal has proposed various railway projects, such as the East-West Railway, Kathmandu Metro Railway, and Raxaul-Kathmandu Railway. Good ballasts are always sought in the projects to diminish maintenance cost. Sediments from the Rapati Nadi (River) in central Nepal are among probable sources of ballasts as those sediments are rich in quartzite clasts. To meet the ballast requirements for railway projects, the study assessed the physical, mechanical and durability properties of alluvial deposit aggregates. The compositional analysis yielded maximum percentage of quartzite followed by sandstone and others. The aggregates yielded uniformity in gradation. Flakiness and Elongation Indices of the tested samples ranged from 11.18 to 24.10% and from 13.07 to 42.77%, respectively. Specific gravity exceeded 2.4. Aggregate Impact Value, Aggregate Crushing Value and Los Angeles Value of the tested samples were respectively 4.4-13.2%, 10.20-17.67% and 15.75-34.25%. Similarly, the point load strength index ranged from 3.69 to 6.57 MPa, and the Sodium Sulphate Soundness Values ranged from 0.96 to 2.06%. All the test results satisfied the conditions based on IS specification in the context of aggregate shape, crushing strength, impact strength, and durability against abrasion. When the results of different indices and values are rated based on their higher, intermediate and lower ranges, all the samples fall in the range of the high rating. Thus it shows suitability of aggregates of the Rapati Nadi and sediment aggregates deposited between Basantapur and Bastipur seem better compared to other locations.

Assessing water-induced changes in tensile behaviour of porous limestones by means of uniaxial direct pull test and indirect methods

Understanding the uniaxial tensile behaviour of rocks and its water-induced variation are key issues for designing effective mining and civil engineering structures and for assessing numerous geotechnical hazards. However, these aspects remain poorly analysed because conducting uniaxial direct pull tests is a difficult and time-consuming laboratory task that requires the use of sophisticated equipment and complex rock sample preparation and processing. This work attempts to expand knowledge by determining several tensile properties of three porous limestone lithotypes under dry and water-saturated conditions through two different approaches: by conducting direct tensile tests and by means of indirect methods (i.e. Brazilian and point load tests). The results revealed that water saturation generated important reductions in their uniaxial tensile strength (UTS), tensile elastic modulus (Et), Brazilian tensile strength (BTS) and point load strength index (Is(50)). In addition, their petrological characteristics and mineralogical composition are used to discuss the main causes of the observed tensile softening. Furthermore, highly accurate correlation functions were established between the direct tensile strength parameters (UTS and Et) and the indirect ones (BTS and Is(50)) for the whole set of tested rocks. The proposed relationships are a novel and useful contribution to geomechanics because they enable the estimation of pure tensile parameters using alternative, cheap, rapid and versatile tests.

Point load test method for prediction strength of sustainable mortar made from blended cement and fly ash

Fly ash (FA) is a by-product of power plants where a number of serious efforts in the field of sustainable building materials have spawned a recycling method in the form of cementitious material containing FA as raw material, including blended cement. The contribution of blended cement to producing sustainable mortar is presented in this study. The FA at a percentage of 10% to 30% by weight of cement is used instead of blended cement in the manufacture of mortar. The results of the point load strength index (PLSI) at the age of 7 days the percentages of FA-0, FA-10, FA-20, and FA-30 were 0.58, 0.46, 0.41, 0.41 N/mm2 and at the age of 28 days were 0.88, 0.85, 0.79, and 0.78 N/mm2 respectively, indicating that the mortar produced with blended cement and FA is carried the point loads well because it has stiffness and adequate robustness. The contrast test with available methods verifies that PLSI offers an alternative to compressive test and it has high accuracy. The point load test method can be used to predict the strength of mortar produced of blended cement and FA.

Temperature effect on the mechanical behavior of shale: Implication for shale gas production

• The variation in mechanical strength parameters of shale at elevated temperatures. • Tensile strength, mode-I fracture toughness and point load strength investigation. • Mechanical strength attributes were supported with XRD and SEM analysis. • Micro-crack and thermal behaviour of minerals induced thermal behaviour of shale. Deformational shale attributes such as fracture toughness, tensile strength, and axial point load strength (PLS) index under elevated temperatures are crucial for the petroleum and gas industries. Here, an attempt has been made to investigate the thermal response of shale from room temperature to 400°C. Three-point bending (TPB) test using semi-circular bending (SCB) specimen, Brazilian tensile test, and the point load strength index test were conducted to evaluate mode-I fracture toughness, tensile strength, and PLS index, respectively, with varying temperatures. Additionally, the X-ray Diffraction (XRD) analysis was performed to determine the bulk rock composition and the resulting phase changes with increasing temperature. Furthermore, Scanning Electron Microscope (SEM) was used to study the induced microcracks in the sample due to thermal treatment. It was found that the mode-I fracture toughness increased from 25°C up to 100°C and, after that, a slight decline up to 400°C. The fracture toughness of the shale got increases from 0.256 MPa·m 1/2 to 0.454 MPa·m 1/2 in a transition from ambient room condition to 400°C. The same trend was obtained for tensile strength and PLS index. With the same temperature range, the tensile strength of the shale changed from 7.94 MPa to 9.75 MPa. The SEM images of the thermally treated samples demonstrate the formation of noticeable microcracks at 400°C.

Engineering Geological Assessment at Grandview Heights, Paya Terubong, Pulau Pinang, Malaysia

Grandview Heights, Paya Terubong is an old apartment building situated on a coarse-grained biotite granitic bedrock hillside. Paya Terubong is a landslide prone area where various landslides have been reported since 1998. The granitic hill has been disturbed during construction of the apartment. Due to the possibility of future landslides, an engineering geological study was conducted to assess the stability of this rock hill beneath this apartment. The scopes of study included discontinuity surveys, geomechanical characterization of the rock mass and slope stability analysis. Based on the results of discontinuity surveys, four major joints sets-were identified and labelled as J1 (195°/62°), J2 (248°/65°), J3 (304°/63°) and J4 (230°/39°). One (1) potential planar failure J2 (248°/65°) and one (1) potential wedge failure J1-J2 intersection (213°/60°) were identified based on kinematic analysis. Dry rock density was from 2.56 g/cm3 to 2.61g/cm3. The water content was from 0.14 % to 0.15% with low porosity values from 0.50% to 0.54%. The point load strength index, Is(50) was 6.63 MPa. The Slope Mass Rating (SMR) for was 64 to 79 and classified as class II with the probability of failure of 0.2.

Investigation of the Effect of Weathering of Selected Charnockite Rocks in Nigeria on Its Engineering Properties

The effect of alteration in the petrographic characteristics of charnockite on its strength, its engineering properties and transformations of the specific gravity which took place during weathering has been examined in this study. This study characterized selected samples of un-weathered and weathered charnockite rocks of Ijare, Ondo State, Nigeria. The physical properties determined were specific gravity, density, porosity, water content and water absorption while the mechanical properties investigated include the point load strength index. Results from the analysis carried out reveal: the point load index of 5.74Mpa and 3.72Mpa for unweathered and weathered samples; average uniaxial compressive strength of 136.90Mpa and 65.50Mpa for unweathered and weathered samples; slake durability of 98.80% and 97.80% for unweathered and weathered sample; Schmidt rebound value of 49Mpa and 45Mpa for both the unweathered and weathered samples respectively. The rock samples were also subjected to petrographical analysis whose result shows that weathering increases some investigated physical properties like porosity, water content and water absorption of the rock while decreasing the specific gravity and density. The result of the tests shows the bulk and dry densities increase for both the weathered and unweathered samples; increased degree of weathering equally results in a major reduction in the strength of the charnockite rock which is directly associated with changes in mineralogy and associated porosity. The point load strength, uniaxial compressive strength test and rebound hardness result values decreases because of weathering. Weathering processes also affected the physical properties of rock, mineralogy, chemical composition as well as the mechanical properties of the rock thereby reducing the strength and mechanical behavior of the rock materials.

Summary of the Transformational Relationship between Point Load Strength Index and Uniaxial Compressive Strength of Rocks

The point load test is an effective and rapid way to predict rock strength. Regarding the investigation of point load strength and the failure characteristics of rock, the point load test’s advantages and application scopes are introduced in this paper. According to the three main components—the rock itself, the size effect, and the loading cross-sectional area—the point load strength’s influencing factors and mechanisms on rock failure were analyzed, followed by expounding the significant effect of the technology of the point load test on evaluating engineering safety and stability. Based on previous scholars’ research results, there is a strong correlation between the point load strength and the uniaxial compressive strength. The parameters of the rocks from different regions and different sediments were summarized via substantial field and indoor testing. The functional relationship (mainly including the linear function, quadratic function, exponential function, power function, and logarithmic function) between the point load strength and the uniaxial compressive strength was obtained by mathematical statistical analysis. Finally, the challenges regarding the point load test were discussed, and accordingly, suggestions for future research were provided.

Suggesting new protocol to determine point load strength index of rocks

Suggesting new protocol to determine point load strength index of rocks

Characterisation and Evaluation of Columnar Basalt Geoheriatge in Thailand: Implication for Geotourism Management in Post-Quarrying Area

Abstract Late Cenozoic basaltic rocks in Nang Rong Columnar Jointed Basalts in southern Khorat Plateau are among the greatest columnar basalts in Thailand as famous geoheritage sites. This work aims to characterize and evaluate the post-quarrying area by field investigation, petrography, geochemistry, and geological engineering. A petrographical study determines these basalts as olivine basalts, presenting porphyritic texture with olivine microphenocryst. Geochemical characteristics indicate these basalts were alkaline basalt generated from alkaline sodic magma series within the continental plates. In addition, columnar jointed basalt presents compressive strength and point load strength index higher than platy basalt with a higher percentage of alteration. Local authorities enhance people in the area to develop and promote their georesources through touristic activities. This geoheritage demonstrates high geology and tourism management values; thus, it could be the prototype of the post-quarrying geosite of Thailand.