如何对岩石进行分类?(ENGINEERING CLASSIFICATION OF INTACT ROCK)
|This method of rock classification was introduced by Deer & Miller in the year 1996. Two parameters are considered while classifying rocks on this method, which are
- Uniaxial compressive strength
- Modulus of elasticity
Step by Step Method to Classify Rock Based on Engineering Parameters)
This method of rock classification consists of 3 steps, as given below.
Step-1 (Classifying the rock based on uniaxial compressive strength)
Step-2 (Classifying the rock based on modulus ratio)
Step-3 (Combining both the above classification)
Step-1 (Classifying the rock based on uniaxial compressive strength)
- Perform uniaxial compressive strength test on a cylindrical rock specimen having length to diameter ratio of at least 2.Click here to know the U.C.S. Test procedure.
- Based on the uniaxial compressive strength test result, the rock is classified as ClassA, B, C, D&E. the table given below was prepared by Deer & Miller to classify rock based on uniaxial compressive strength.
Class Name | Description | Uniaxial Compressive Strength (kg/cm2) | Rock Material |
A | Very high strength | Over 2250 | Quartzite, diabase, basalt, majority of igneous rocks, strong metamorphic rocks. |
B | High strength | 1125 to 2250 | Weakly cemented sand stones, hard shales, majority of limestones, dolomites |
C | Medium strength | 562.5 to 1125 | Many shales, porous sand stones and limestones, schistose, varieties of metamorphic rocks. |
D | 低强度 | 281.25 to 562.5 | Porous, low density rocks, friable stone, truff |
E | Very low strength | < 281.25 | Clay shale, weathered & chemically altered rocks of any lithology |
Step-2 (Classifying the rock based on Modulus Ratio)
- From the stress-strain curve obtained from uniaxial compressive strength test, draw a tangent at 50% ultimate compressive strength of rock & calculate the tangent modulus at this point.
- Then using the following formula, calculate modulus ratio
MR = Et50/σult
Where,
MR = Modulus Ratio
Et50= Tangent modulus at 50% ultimate compressive strength of rock
σult= Uniaxial ultimate compressive strength
- Based on modulus ratio, rock is classified as classH,M&L. After calculating modulus ratio, use the table given below to classify rock based on modulus ratio.
Class | Description | Value of Modulus Ratio |
H | High | >500 |
M | Medium (average) | 200 to 500 |
L | Low | < 200 |
Step-3 (Combining both the above classifications)
In this step, we use both the above class designation to classify rock as AM, BH, CM etc.
例如,CM表示中等强度和模量比的平均值。
2 Comments
How one can differentiate soft rock and common material?
Hello Sir, curious to know whether there’s a silver line of Hard Rock or Ordinary Rock. How one can differentiate whether it is a Hard Rock or Ordinary one from the Strength (UCS) ?