P{f} for Slope Mass Quality

Hi Alvian,

see classes by Ray and use the explanation by me.

Have a good time and fun.

Michael Lersow

Chinese Slope Mass Rating System (CSMR)

Chinese slope mass rating system (CSMR system) is developed by Romana and Zuyu (……….). They introduced two coefficients ξ and λ and modified slope mass rating (SMR) formula as follows.

CSMR = ( ξ * RMR ) + [ λ * F1*F2*F3 + F4 ]

Where, ξ represents the slope height factor and λ represents the discontinuity factor. These factors are included in the system because there are several slope failures for which SMR indicates stable slopes. Therefore, these two factors are included to improve the classification system.

F1, F2, F3 and F4 are the adjustment factors from SMR.

The factor ξ is applicable only for heights greater than 40 m. However, this is an accepted system of classification in Chinese condition only, and needs a number of corrections and modifications before using at any other place.

ξ = 0.57+0.43*80/H

where, H is the height of slope in meters

and,

λ = 1 for faults, long weak seams filled with clay

= 0.8 to 0.9 for bedding planes, large scale joints with gauge

= 0.7 for joints, tightly interlocked bedding planes

Slope Mass Rating (SMR)

Slope mass rating is a system of classification developed by Romana (……)as an extension of Bieniawski's rock mass rating approach for application to rock slopes. RMR is widely used in tunnels and it is not suitable for slopes due to the fact that joints are a more governing parameter for stability in slopes. Some parameters are introduced to include the attitude of discontinuities to assess slope stability

The proposed ‘Slope Mass Rating’ (SMR) is obtained from RMR by subtracting a factorial adjustment factor depending on the joint-slope relationship and adding a factor depending on the method of excavation.

SMR = RMR + (F1 . F2 . F3) + F4

The RMR is computed according to Bieniawski’s 1979 proposal, adding rating values for five parameters:

(i) Strength of intact rock;

(ii) RQD (measured or estimated);

(iii)Spacing of discontinuities;

(iv)Condition of discontinuities; and

(v) Water inflow through discontinuities

RMR has a total range of 0 - 100. The adjustment rating for joints is the product of three factors (F1*F2*F3) as follows:

F1 depends on the parallelism between joints and slope face strike. It ranges from 1 (when both are near parallel) to 0.15 (when the angle between them is more than 30 degrees and the failure probability is very low). These values are found to match approximately the relationship:

where, A is the angle between strike of the slope face and the joint.

F2 is related to joint dip angle in the planar mode of failure. It is a measure of the joint shear strength. Its value varies from 1 (for joints dipping more than 45 degrees) to 0.15 (for joints dipping less than 20 degrees). It has been found to match approximately the relationship:

(B)

where, B denotes joint dip angle. For toppling mode of failure, F2 remains 1.

F3 reflects the relationship between the slope face and the joint dip.

F4 is a factor for the method of excavation and its adjustment factor has been fixed empirically as follows: (Table1).

thanks so much for both of you sir. But, i still thinking. 

for Mr. Ray Russ: Is it true class of CSMR? is it really on percentage?

Yes Mr.,

the ranges of Slope Mass Quality of CSMR, which Ray Russ sent to you, are correctly. Please take a little bit time to read this: http://www.iitbhu.ac.in/faculty/min/rajesh-rai/NMEICT-Slope/Pdf/14%20Classification%20systems%20in%20slope%20stability%20analysis.pdf

Have fun

Michael Lersow

thanks sir. i already read it

Once I have obtained the values with the CSMR method, is there a chart I can use to evaluate the stability of the slope?? There is one for when you use the SMR method. Please Help. I am working on my graduation process.