Test 1 [L1 to L6] Flashcards
What is the brazilian test? (PrevT)
The Brazilian tensile strength test is a method used in rock mechanics to determine the uniaxial tensile strength of rock specimens.
The test involves applying a tensile load to a cylindrical rock sample until it fails, and the maximum load is recorded.
What is the uniaxial compressive strength test? (PrevT)
The uniaxial compressive strength (UCS) test is another common test used in rock mechanics to determine the compressive strength of rock specimens.
The test involves applying a compressive load to a cylindrical rock sample until it fails, and the maximum load is recorded.
What is the 1st stage of site investigation?(PrevT)
- Desk study and site reconnaissance
A desk study involves gathering information about a site from existing documents and records.
Site reconnaissance involves physically visiting the site, gathering information through observation, and interacting with local residents and specialists.
What is the 2nd stage of site investigation? (PrevT)
- Preliminary ground investigation
A preliminary ground investigation aims to gather sufficient information about the site to determine if a more detailed or advanced investigation is necessary.
A preliminary ground investigation may include surface sampling and mapping of soil, rock, and water, geophysical surveys to determine subsurface conditions, test pits or trenches to expose subsurface soil and rock, and drilling to obtain some soil and rock samples.
What is the 3rd stage of site investigation? (PrevT)
- Detailed ground investigation
The detailed ground investigation builds upon the preliminary ground investigation and acquires more detailed information about the site.
Additional data may be obtained from advanced drilling techniques to obtain soil and rock samples from deeper depths with in-situ testing such as cone penetration testing, Casangrande Peiezometer testing, standard penetration testing, and vane shear testing, dilatometer testing, Split-spoon sampling to determine soil and rock properties.
What is the 4th stage of site investigation? (PrevT)
- Monitoring
Monitoring during a site investigation is collecting data over time to track changes in site conditions and compare the new data to previous investigations.
Describe what are direct tests. (PrevT)
Direct tests in rock mechanics involve the measurement of rock strength or other mechanical properties under controlled laboratory conditions.
Give 3 examples of direct test? (PrevT)
Uniaxial compressive strength, triaxial compression tests, and direct shear tests.
Describe what are index tests. (PrevT)
Index tests are used to provide a rapid estimate of rock strength and other mechanical properties in the field.
Index tests are usually less accurate than direct tests but are faster and less expensive to perform.
Give 2 examples of index test? (PrevT)
Point load test, the Schmidt hammer test
Name 3 different geophysics techniques used in subsurface investigation. (PrevT)
- Seismic Refraction
- Electrical Resistivity
- Ground Penetrating Radar (GPR)
Describe the Seismic Refraction technique. (PrevT)
Seismic Refraction: This method involves the measurement of the time delay between the arrival of seismic waves at different points in the subsurface, which is used to determine the velocity of the waves as they pass through different layers of rocks and soil.
Describe the Electrical Resistivity technique. (PrevT)
Electrical Resistivity: This method involves injecting a low-level electrical current into the ground and measuring the electrical resistance between two electrodes.
Describe the Ground Penetrating Radar (GPR) technique. (PrevT)
Ground Penetrating Radar (GPR): This method operates by emitting high-frequency electromagnetic pulses into the ground and measuring the time delay and strength of the reflected signals.
Name 4 subsurface techniques (not geophysical).
- Test Pits
- Borehole Drilling
- Soil Sampling
- In Situ Testing
Describe the subsurface technique of Test Pits. (PrevT)
Test Pits: This method involves digging shallow pits to expose the subsurface materials and structures for visual inspection and sampling. Test pits are often used in archaeological investigations and environmental assessments to gather information about the subsurface soil and rock layers.
Describe the subsurface technique of Borehole Drilling. (PrevT)
Borehole Drilling: This method involves drilling a deep hole into the subsurface to collect samples of subsurface materials and to install monitoring wells. Borehole drilling is commonly used in groundwater investigations and site characterizations.
Describe the subsurface technique of Soil Sampling. (PrevT)
Soil Sampling: This method involves collecting soil samples from the subsurface using various sampling techniques, such as auger sampling, split-spoon sampling, and others. Soil samples are analyzed in the laboratory to determine their physical and chemical properties.
Describe the subsurface technique of In Situ Testing. (PrevT)
In Situ Testing: This method involves performing tests on subsurface materials in their natural state without removing them from the ground. In situ tests, such as cone penetrometer tests, permeability tests, and others, provide information about the subsurface materials’ mechanical and hydraulic properties.
Describe the main and following problems of the Carsington tunnel. (PrevT)
Improper site investigation. The other problems such as broken equipment and water seeping into the tunnel originate from a lack of awareness of the geological conditions along the tunnel pathway.
What is triaxial testing of rocks? (PrevT)
The test involves placing a cylindrical specimen of rock or soil in a triaxial cell and applying confining pressure to the specimen while measuring its response to axial and radial loads.
What are the parameters which are obtained from triaxial tests? (PrevT)
With the axial and radial stresses, it is possible to plot Mohr circles offset from each depending on the stress applied. The circles defined a failure envelope for this type of rock. The failure envelope is the tangent line to the Mohr circles.
With all these information, it is possible to obtain the shear stress parallel to fracture failure, the cohesion of rock, the normal stress across the shear zone and finally the coefficient of internal friction.
Name the 4 main types of slope failure. (PrevT)
- Planar
- Wedge
- Toppling
- Composite
Describe the slope failure: Planar (PrevT)
Describe the slope failure: Wedge (PrevT)
Describe the slope failure: Toppling (PrevT)
Describe the slope failure: Composite (PrevT)
With the aid of a graph, demonstrate the brittle and ductile behavior of rocks. (PrevT)
Where/How do you measure the modulus of elasticity. (PrevT)
How do we test shear strength of joints? (PrevT)
Give the definition of rock mechanics (Extra)
Rock mechanics is a theoretical and applied science of the mechanical behavior of rock and rock masses.
Why is rock mechanics said to be a science but also an art?
The Art can be considered as the experience gathered.
The science is application of Mechanics.
What is rock mass characterization?
Description of the Rock Mass, including distribution in space of both the materials that constitute the mass and the discontinuities that divide it.
What is a rock mass?
is the total in situ medium containing bedding planes, faults, joints, folds, and other structural features. Rock masses are discontinuous and often have heterogeneous and anisotropic engineering properties.
What is Rock material?
Rock material: is the term used to describe the intact rock between discontinuities
What is Rock structure?
The nature and distribution of structural features within the rock mass
What is soil?
Soil: is a natural aggregate of mineral grains that can be separated by such gentle mechanical means
What is rock?
Rock: is a natural aggregate of minerals connected by strong and permanent cohesive forces.
Give 2 type of weathering. 3 examples for each
Physical: Waves, Freeze/thaw, wind
Chemical: Redox, hydrolysis, carbonization
What are joints?
Joints: Fractures that result from brittle deformation – typically no displacement.
What is rock burst?
Rock Burst: It is caused by the failure of rock masses due to the stress concentration and release of energy stored in the rock mass. Throwing rock
Give 2 instances where dynamic forces are applied on rocks.
Blasting and Earthquakes
What are bedding planes?
Bedding planes: divide sedimentary rocks into beds or strata
What are folds?
Folds: are structures in which the attitudes of the beds are changed by flexure resulting from the application of post-depositional tectonic forces.
What are faults?
Faults: are fractures on which identifiable shear displacement has taken place.
What is soil mechanics?
Soil mechanics: is a discipline that applies the principles of engineering mechanics to soils to predict the mechanical behavior of soil.
Name 3 types of retaining structures.
- Tiebacks
- Soil nailing
- Sheet piles/Cofferdam
Describe tiesbacks.
Tiebacks: They consist of cables, rods, or straps that are anchored into the ground behind the wall and then attached to the wall itself, creating a horizontal force that counteracts the vertical forces acting on the wall.
Describe soil nailing.
Soil nailing: It involves the insertion of reinforcing steel bars, called soil nails, into the soil or rock mass. The nails are then covered with a shotcrete layer or grout to create a reinforced soil mass.
Describe sheet piles
Sheet piles: are installed in a trench or excavation, either by driving them into the ground. They create a continuous wall that resists lateral soil pressure and helps to retain soil or water.
Describe cofferdam.
A cofferdam: is constructed by excavating the area around the work site and installing sheet piles, bulkheads, or other retaining structures to create a watertight enclosure. Cofferdams allow construction to occur in areas that would otherwise be inaccessible and provide a safe and controlled environment for workers.
Give 4 ground improvements methods.
- Compaction (Impact roller)
- Jet grouting
- Compaction grouting
- Chemical injection
Describe jet grouting.
Jet grouting: is used in various applications, such as reinforcing soil for retaining structures, improving the load-bearing capacity of soil. It involves injecting a high-pressure jet of grout into the ground, which fragments and mixes the soil to create a dense, homogeneous mass.
Describe compaction grouting.
Compaction grouting: involves the injection of a low-slump grout mixture into the soil to increase its density and strength. The grout mixture fills the voids and spaces in the soil, increasing the overall soil mass and creating a denser, more compact soil structure
Describe chemical injection.
Chemical injection: involves the injection of a chemical mixture into the ground to improve the soil’s strength, stability, and load-bearing capacity. The chemical mixture can be a grout, a polymer, or a combination of both, and is typically injected using specialized equipment.
What is site investigation?
Site investigation refers to the procedure of determining surface and subsurface conditions in an area of proposed construction.
What are the 4 primary objectives of site investigation?
- The nature and sequence of the subsurface strata
- The groundwater condition at the site
- The physical properties of the soils and rock underlying the site
- The mechanical properties, such as strength and compressibility of the different soil or rock strata
What are sinkholes?
Sinkholes : are geological formations that occur when the surface layer collapses into a void created by dissolution of underlying rock.
Name 3 types of boreholes techniques.
- Hand operated auger methods
- The mechanical auger method
- The wash boring method : Water at high velocity is pumped down and up carrying the soil particles to the surface
How to make sure samples have the same properties in the field and in the lab?
To ensure it will have identical properties to the field conditions, right after extracting core samples from the core barrel, they can be wrapped in plastic sheeting and sealed in a core box using wax or resin foam.
If soil and rock samples are not tested in a timely manner, they may be disturbed by… Name 3
- dehydration,
- swelling
- vibration
What is SPT?
SPT – Standard Penetration Test
140 lb hammer dropped 30” penetration is measured
When is casing used?
Casing is used in loose, weak or fractured rocks to prevent caving in of the strata, in porous fissured rocks to prevent loss of the flushing medium and in soft rocks to prevent them from swelling and squeezing into the hole.
Name 5 test that can be done Downhole.
- Perioscope
- Cameras
- Imperssession Packers
- Geophysical logging
- Downhole testing
Name the 2 types of rock samples that can be obtained.
- Cores
- Blocks
Name 3 reasons to understand stresses in rock mechanics.
- There is a pre-existing stress in the ground and we need to understand it
- The stress state can be changed dramatically with activity
- Stress is not familiar
Name 2 problems with core drilling.
- Rock mass surrounding borehole not self-supporting
- Protruding material in borehole
Name 3 solutions to problem with core drilling.
- High density drilling fluids plug fractures and temporarily stabilize the borehole wall
- Installing casing in the borehole and reducing the size of the hole beneath the casing
- Cement hole and redrill after the cement has hardened
Name 6 ways to minimize Core losses due to erosion of material from fluid circulation
- Bit discharge directed away from core
- Drilling fluid use kept to a minimum
- Polymer compounds added to drilling fluid
- Vibration of drill rod minimized
- Controlled advancement of the drill rod
- Core-catching devices installed
What is contained in rock core logs. Name 3.
- Percent core recovery
- Amount and location of core loss
- Depth of the beginning and ending of each core run
What is porosity?
Porosity refers to the fraction of a material’s total volume that is made up of void spaces, or pores. It’s a measure of the amount of space available for fluid to occupy within the material.
What is permeability?
Permeability, refers to the ability of a material to allow fluid to flow through its pores. It’s a measure of the ease with which fluid can move through the material.
What is brittle deformation?
Brittle deformation : permanent change that occurs in a solid material due to growth of fractures and/or sliding on them once they have formed
What is rock spalling?
Rock spalling is the process of breaking off small fragments or chips from a rock surface due to stress
What are 3 discontinuities caused by brittle deformation?
- Joints
- Faults
3.Veins
What are the 4 categories of brittle deformation processes?
- Tensile Failure : Opening and propagation of cracks into unfractured material
- Shear Failure : Initiation of macroscopic shear fracture
- Frictional sliding and Failure : Sliding on preexisting fracture
- Cataclastic flow : Macroscopic ductile flow from grain-scale fracturing an frictional sliding
What is hydraulic fracturing?
Hydraulic fracturing : can create tensile fracturing in a rock cylinder even if remote principal stresses are compressive by increasing the fluid pressure in pores and cracks
Give the coulomb fracture criterion formula and describe variables.
Graph the result of triaxial tests and identify important components.
Give coulomb fracture criterion formula when there is fluid pore pressure involved.
Describe the Ring shear test.
Ring shear Test : Load is applied parallel to the axis of core. As the load is applied to the plunger, 2 sets of complex fractures surfaces form along the two planes of imposed shear. The shear strength is calculated by Tp = P/2A where p = load , A = area of cross section of specimen.
What is the point load index formula?
Describe the SCHMIDT HAMMER REBOUND index test
The hammer measures the rebound of a spring-loaded mass impacting against the surface of the sample. The test hammer will hit the concrete at a defined energy. Its rebound is dependent on the hardness of the concrete and is measured by the test equipment. By reference to the conversion chart, the rebound value can be used to determine the compressive strength
Give the Slake durability Index test formula.
ID = ROCK RETAINED IN THE DRUM/TOTAL DRY WEIGHT OF THE ROCK *100
