Study on Determination of Rock Mass Quality Parameter M, S Value and Impact of it to Rock Mass Strength
Based on the research works of the predecessors the author firstly induced and sum up some methods of determining rock mass quality parameter m, s value. And the author had the study on impact of the rock mass quality parameter m, s value to rock mass str
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STUDY ON DETERMINATION OF ROCK MASS QUALITY PARAMETER M, S VALUE AND IMPACT OF IT TO ROCK MASS STRENGTH Hailang Hu, Qiufeng Huang and Jianlin Li China Three Gorges University Key Laboratory ofGeological Hazards on Three Gorges Reservoir Area, Ministry ofEducation, Yichang 443002, China Based on the research works of the predecessors the author firstly induced and sum up some methods of determining rock mass quality parameter m, s value. And the author had the study on impact of the rock mass quality parameter m, s value to rock mass strength, while it combining with the high slope rock mass of Three Gorges Project permanent navigation lock of Yangtse River. Then got the change patterns about not only m, s value to Hoek-Brown strength envelope curve, but also m, s value to instantaneous internal friction angle rPi' And it has some application value and reference value for studying the impact of rock mass quality parameter to rock mass strength. FOREWORD
The rock mass quality parameters m, s value are determined by rock characteristics and the damage degree before it reaching the maximum main stress crt and the minimum main stress cr3 ( Li Jianlin, 2003). The m, s value as the important parameters of describing rock mass characteristics, the values have quite big randomness. Just like professor Liao Guohua said.i'We can't directly determine the experienced parameter m, s value exactly." Therefore, m, s value right or wrong, not only takes quite error with using the Hoek-Brown strength criterion, but also influencing the accurate judgment for the engineering security. The author has studied the determination of rock material parameters m, s value and their influence to the rock mass strength in this paper. METHOD FOR DETERMINATION OF m, s VALUE Looking up the table to estimate m, s value
When E.Hoek came up with the Hoek-Brown strength criterion in 1980, on the basis of triaxial experimental data of different kinds ofrock mass, he got the experienced parameter m, s value through summing up the data. He then modified the values in 1988, and gave the modified m, s values. The modified m, s values are acquired combining the practical experience based on the results achieved in 1980. And they had been used widely in the engineering field at home and abroad (E.Hoek and E.T.Brown, 1988).
Using rock triaxial experiment to determine m, s value For the integrate rock block, usually assuming s=l, then calculates to get the m value and rock compressive strength ere (Zhou Hanmin.2006) according to the data. Assuming then,
x=er3,
y=erl-er3,
ere =
LY _LX[L XY -~LXLY] n n LX -!(Lxf n
(1)
2
m
=;,
LXY -! LXLY] [ LX' -1(LX)'
(2)
In the formulas, n is the number of groups, and the number is usually more than five.
! LY-!mercLX
s= n
n erc 2
(3)
If the calculated s value is less than zero, then should assume s=O, for showing it is the damaged rock mass. And the calculating formula ofcorrelation coefficient p2 is as follows. 2
p=
[LXi~-~LXiL~
J
[LX/ -~(LXir][ L~2 -~(L~r]
~
The more correlation coefficient p2 closed
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