Test Method for Determining Deformability and Strength of Weak Rock by an In Situ Uniaxial Compressive Test

AbstractWater tunnels built for hydropower passing through weak and heterogeneous rock mass pose challenges associated to slaking and disintegration, as they are first exposed to dry condition during excavation and are then filled with water to produce hydropower energy. Over the period of operational life, these tunnels are drained periodically for inspections and repair leading to drainage and filling cycles. The weakening of rock mass caused by cycles of drying, saturation and drainage may lead to the propagation of instabilities in the tunnels. Therefore, it is important to study the slaking and disintegration behavior of the weak rock mass consisting of clay and clay-like minerals. This paper assesses the mineralogical composition of flysch and serpentinite from the headrace tunnel of Moglicë Hydropower Project in Albania. Further, to determine the slaking and disintegration behavior of these rocks, extensive testing using both the ISRM, Int J Rock Mech Min Sci Geomech Abstr 16(2):143-151, (1979) suggested test method and a modified variant of this test are performed. Finally, comprehensive assessments, discussions and comparisons are made. It is found that the modified slake durability test better suits for the tunnels built as water conveying systems such as hydropower tunnels.

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Estimation of Creep-Fatigue Damage Through Indentation Test Method

Volume 3: Design and Manufacturing ◽

10.1115/imece2011-63445 ◽

2011 ◽

Author(s):

Raghu V. Prakash

Keyword(s):

Tensile Properties ◽

Fatigue Damage ◽

Indentation Test ◽

Creep Damage ◽

Test Method ◽

Specimen Preparation ◽

Creep Fatigue ◽

Critical Components ◽

The Cost

Creep, creep-fatigue damage is often estimated through in-situ metallography, tensile testing of specimens. However, these methods require specimen preparation which includes specimen extraction from critical components. Automated ball indentation testing has been used as an effective tool to determine the mechanical properties of metallic materials. In this work, the tensile properties of materials subjected to controlled levels of damage in creep, creep-fatigue is studied. It is found that the tensile properties such as yield strength and UTS deteriorates with creep damage, whereas the same specimens show an improved UTS values (at the cost of ductility) when subjected to creep-fatigue interactions.

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Modeling the Resilient Modulus Variation of In Situ Soils due to Seasonal Moisture Content Variations

Advances in Civil Engineering ◽

10.1155/2019/1793601 ◽

2019 ◽

Vol 2019 ◽

pp. 1-7

Author(s):

Kevin Gaspard ◽

Zhongjie Zhang ◽

Gavin Gautreau ◽

Khalil Hanifa ◽

Claudia E. Zapata ◽

...

Keyword(s):

Moisture Content ◽

Resilient Modulus ◽

Optimum Moisture Content ◽

Test Method ◽

Large Scatter ◽

Controlling Parameter ◽

Base Course ◽

The Relationship ◽

Level 2

LTRC is conducting a research project to determine the seasonal variation of subgrade resilient modulus (MR) in an effort to implement PavementME. One objective of that project, which is presented in this paper, was to locally calibrate the Enhanced Integrated Climate Model’s (EICM Fenv) curve for seasonal subgrade MR changes. Shelby tube sampling was conducted on six different roadways to a depth of approximately 7.92 m beneath the shoulder pavement’s base course. The AASHTO T-99 MR test method was used on all samples with an additional eight specimens being tested with NCHRP 1–28A MR test method. Four soils from Louisiana which were not from the six roadways were also tested and included in the analyses. Once the MR tests were completed and plotted, it was noticed that there was a rather large scatter (R2 = −0.266) around the EICM Fenv curve. The authors hypothesized that this occurred due to the density differences between in situ and remolded specimens. Further analyses confirmed this hypothesis. LTRC developed a new method based on the EICM Fenv method to determine the relationship between changes in subgrade MR as a function of changes in moisture content with the in situ moisture content and MR used as the control. This method differs from the EICM Fenv in that the EICM Fenv uses optimum moisture content as the controlling parameter. The LTRC method can be used for design purposes as well as level 2 inputs into the EICM.

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