To classify the surrounding rocks of superlargespan caverns of 20~70 m, a novel method is proposed. This method
uses the area weighted average to determine the basic quality indicators of the
surrounding rock during the preliminary classification stage and increases the
span influence correction coefficient during the detailed classification stage.
The value of the span influence correction coefficient is determined based on
the relationship between the stability coefficient of the tunnel and the basic
quality index of the surrounding rock, along with the tunnel span.
Additionally, a threedimensional numerical simulation
of the entire excavation process and strength reduction method are used to
calculate the stability coefficient of caverns with spans of 20~70 m in grade Ⅰ~Ⅳ surrounding rocks. Through analysis, an
empirical formula relating the stability coefficient of the cavern to the basic
quality index and span of the surrounding rock is obtained. The results reveal
the following insights: (1) As the span increases from 20 to 70 m, the
stability coefficient of the tunnel decreases by 46.54% to 50.67%. (2) When the
tunnel span remains constant, the smaller the basic quality index values of the
surrounding rock correspond to poorer tunnel stability. The span influence
correction coefficient is defined as the ratio of the relative deviation of the
tunnel stability coefficient from the reference span (20 m) to the grade
difference of the reference span tunnel stability coefficient. This correction
coefficient for span influence is 0~1.0, where the most adverse effect of
increasing the span on the stability of the surrounding rock is equivalent to
decreasing one grade in the grade of the surrounding rock.
QIAO Chunsheng
,
WANG Ke
,
HE Weiguo
,
LYU Shuqing
.
Surrounding Rock Classification Method for Super-Large-Span Flat
Underground Caverns
[J]. Tunnel Construction, 2023
, 43(9)
: 1443
-1454
.
DOI: 10.3973/j.issn.2096-4498.2023.09.001
