Test 3 [KB] Flashcards
What is Rock Structure Rating (RSR)?
A classification method based on a quantitative method for describing the quality of a rock mass and for selecting appropriate support.
RSR = A + B + C
-Classification method
- Quantitative method
- quality of rock mass
- appropriate support
For RSR, what is the first parameter and its subparameter?
Geology:
a. Rock type origin (igneous, metamorphic, sedimentary)
b. Rock hardness (hard, medium, soft, decomposed)
c. Geological structure (massive, slightly faulted/folded, moderately faulted/ folded…)
For RSR, what is the second parameter and subparameter
Geometry:
a. Joint spacing
b. Joint orientation
c. Direction of tunnel drive
What is the 3rd parameter and subparameters
Effect of groundwater inflow and joint condition.
a. Overall rock mass quality on the basis of A and B combined
b. Joint condition
c. Amount of water inflow
What is tunneling Quality index (Q)
The Q index system assigns a numerical value to a rock mass based on the quality of the rock mass and the conditions of the tunneling project.
-index system
-numerical value to rock mass
-quality rock mass
-conditions of tunneling project
Write the equation and list the parameters involved.
Describe the Block Size.
Overall structure of rock mass
Describe Inter block shear strength.
tan-1 (Jr/Ja) is good approx of sliding angle of friction along clay coated joints
Describe Active stress.
Empirical factor describing active stress
Discuss about the possibility of performing an Unconsolidated-Drained triaxial test.
Performing an U-D triaxial test is possible,
but If the soil is too dense or compact,
it may not be possible to perform the U-D test
because it will be difficult to achieve the desired stress state in the sample.
A clean well-graded sand would rate very high in the AASHTO soil classification system, and thus be considered a good soil for use as a highway subgrade. However, it would be a very poor choice for certain other applications. Give an example of a situation where this soil would not be a good choice.
For example, if a building were to be constructed on a layer of such soil,
water could easily pass through and accumulate below the foundation.
This could lead to the loss of support and stability of the foundation, potentially causing settlement or even collapse of the building.
When subjected to typical rates of loading in the field, sands are usually considered to have
drained conditions. Why?
When a sand layer is loaded in the field, the water in the soil is able to flow out quickly through the soil pores due to the high permeability of the sand.
This means that the excess pore water pressure generated during loading is able to dissipate rapidly.
Therefore, the soil can be considered to be under drained conditions.
