Variability of unconfined compressive strength in relation to number of test samples

Ruffolo, Richard M.; Shakoor, Abdul

doi:10.1016/j.enggeo.2009.05.011

Cited by 54 publications

(16 citation statements)

References 23 publications

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“…They further demonstrated that for a given rock and test type, the minimal sample size varies from one case to the other. The conclusions by Gill et al (2005) are in direct agreement with more recent work by Ruffolo and Shakoor (2009). The latter work investigated the number of required tests to estimate the mean unconfined compressive strength of different rock types.…”

Section: How Reliable Are Collected Datasupporting

confidence: 83%

“…Unless they can be analysed and summarised, they are of limited use. In order to be useful, data have to be processed and 9 Minimum number of samples needed to estimate mean unconfined compressive strength based upon acceptable deviation from mean and corresponding coefficient of variation, using confidence interval approach, after Ruffolo and Shakoor (2009) At least three converted into information. In a deep mining context it may very well be that, depending on the level of detail required, one person's information is another person's data.…”

Section: Discussionmentioning

confidence: 99%

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Where do the data come from?

Hadjigeorgiou

2012

Mining Technology

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Deep and high stress mining poses a significant number of geotechnical challenges. Despite considerable improvements in almost every technological aspect of the design and operation of mines at depth and under high stress, the weakest link remains the quality and quantity of data. This paper addresses certain inconvenient facts on how data are collected and managed. The case is made for a disciplined approach to data collection, analysis and interpretation. Unless this is implemented in a systematic way, it will not be possible to capitalise in gains made from improved engineering tools. A further concern is that for mines operating at depth, the margin of error due to inadequate or inappropriate data is much smaller, and the repercussions more severe, compared to shallow mines.

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Section: How Reliable Are Collected Datasupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Where do the data come from?

Hadjigeorgiou

2012

Mining Technology

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“…Variation in sonic velocity logging data (Figure 3h) similarly implies a frequent variation in rock strength [Chang et al, 2006]. Incorporating such heterogeneity in the distribution of rock properties in modeling of a geologic medium is fundamental to establishing confidence in a risk assessment of instability for drilling and excavation design [Einstein and Baecher, 1983;Tang, 1997;Hoek et al, 2000;Moos et al, 2003;Ruffolo and Shakoor, 2009;Sari, 2009].…”

Section: Remarks Of Geologic Heterogeneitymentioning

confidence: 99%

In situ stress conditions at IODP Site C0002 reflecting the tectonic evolution of the sedimentary system near the seaward edge of the Kumano basin, offshore from SW Japan

Song

Chang

2017

JGR Solid Earth

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This paper presents a complete set of in situ stress calculations for depths of 200–1400 meters below seafloor at Integrated Ocean Drilling Program (IODP) Site C0002, near the seaward margin of the Kumano fore‐arc basin, offshore from southwest Japan. The vertical stress component was obtained by integrating bulk density calculations from moisture and density logging data, and the two horizontal components were stochastically optimized by minimizing misfits between a probabilistic model and measured breakout widths for every 30 m vertical segment of the wellbore. Our stochastic optimization process reveals that the in situ stress regime is decoupled across an unconformity between an accretionary complex and the overlying Kumano fore‐arc basin. The stress condition above the unconformity is close to the critical condition for normal faulting, while below the unconformity the geologic system is stable in a normal to strike‐slip fault stress regime. The critical state of stress demonstrates that the tectonic evolution of the sedimentary system has been achieved mainly by the regionally continuous action of a major out‐of‐sequence thrust fault during sedimentation in the fore‐arc basin. The stable stress condition in the accretionary prism is interpreted to have resulted from mechanical decoupling by the accommodation of large displacement along the megasplay fault.

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Section: Variability Of Unconfined Compressive Strengthmentioning

confidence: 99%

“…Unconfined compressive strength is a commonly used parameter for rock mass characterization, slope stability analysis, bearing capacity analysis for foundations, the design of underground excavations, and selection of excavation methods (Ruffolo and Shakoor, 2009). The estimation of unconfined compressive strength can be challenging since the value of unconfined compressive strength frequently varies from the same rock.…”

Section: Variability Of Unconfined Compressive Strengthmentioning

confidence: 99%

Development of a correlation between mineralogy, rock strength measures, and breakage of Copper Porphyries

Yildirim¹

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The role of the comminution step in mineral processing is to reduce the size of the ore so that the valuable minerals liberated from the gangue minerals, in preparation for beneficiation. The effectiveness of the comminution step is related to the rock strength, which controlled by the minerals making up the rock, relative mineral abundances, texture, fracture frequency, and its associations. Copper porphyry deposits account for approximately two-thirds of global copper and form a good basis for investigating the effects of ore structure in comminution.Recent developments in integrated studies between ore variability and mineral processing have driven the need to understand ore variability better as a means of maximizing the value from the ore. As a result, the developed methodologies are now being adapted for incorporation into geological and metallurgical databases, with the aim of linking ore mineralogy to comminution and beneficiation performance. However, the current developments are driven by statistical correlations rather than a fundamental and mechanistic understanding.This thesis aims to develop a fundamental mechanistic relationship between mineralogy, hardness, and breakage by focusing on proportional mineral ratio changes caused during copper ore formation. Incorporated geological understanding of porphyry copper ore formation and phyllic alteration to processing is studied for two case studies viz. Highland Valley Copper Mine (HVC) and Los Bronces Mine (LB) and the approach underpins and strengthens the current methodologies for predicting the mill throughput of copper porphyries.This new approach introduces the key ore-forming parameters to mineral processing. The relationship between processing performance (breakage) and the degree of phyllic alteration is studied. This provides a link of ore genesis with rock strength and breakage behavior. A mechanistic method of single impact load cell test was utilized to measure the rock strength. The link between the strength and primary geological features is studied using QXRD; X-ray computed tomography and automated logging instruments.The thesis establishes that there is a relationship between the proposed porphyry copper process alternation index (PAI) and rock strength. The methods in this study can be used in developing the relationships between primary geological features and the rock strength; providing a novel and powerful technique to propagate breakage characteristics into the geological model of an ore body. Barış Gazanfer Yıldırım ii Declaration by authorThis thesis is composed of my original work and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis.I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and a...

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Variability of unconfined compressive strength in relation to number of test samples

Cited by 54 publications

References 23 publications

Where do the data come from?

Where do the data come from?

In situ stress conditions at IODP Site C0002 reflecting the tectonic evolution of the sedimentary system near the seaward edge of the Kumano basin, offshore from SW Japan

Development of a correlation between mineralogy, rock strength measures, and breakage of Copper Porphyries

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